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09-24-2011 Post does not mapped to Knowledge Tree
Jorge
Austin TX
Posts 141
Joined on 10-17-2010
Post #: 26
Post ID: 17060
Reply to: 17059
Slanted enclosure
fiogf49gjkf0d
I will be dubiuos about the slanted enclosure if not done properly,  all drivers must be time aligned and since they are playing the same frequency, deficiencies in time alignment become more obvious.  I made a slanted enclosure but with the drivers facing forward, that is: out of alignment completely,  you can imagine how bad they sounded!
With the configuration you propose all drivers will be aligned and will shoot at an angle to the floor,  for the frequencies under 20 hz I hardly think this will be a problem, actually it might be even better.  For crossing at 100 hz its a whole different story...

I think one of the most important things about the lower channels is amplification and GAIN! The horn channels are too sensitive,  if we use 88 db woofers even in a huge array, lowering the volume on the horns wont really help in matching volume with the right tone and dinamic size,  more gain is needed for the bass array,  I like gargantuan gain for bass channels!
09-24-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006
Post #: 27
Post ID: 17062
Reply to: 17060
Lots of Little "Woofers"
fiogf49gjkf0d
The 10" "woofer" is well known to "high-end" designers, who love the "fast" bass, and I have to admit that Wilson and Dunlavy (among others) have also managed to get some impressive (at least for a while...) "dynamics" from the little woofers.  To look at the 10" charts, or (God forbid) to listen to the 10", one sees (and hears), of course, that the "fast" 10" driver makes most of its noise well above LF, and the "long-stroke" 10" is mechanically and electrically tailored to make more LF, given a LOT more power.  Fooling with mass vs compliance can certainly drop Fs, and there are plenty of other tricks, but nothing can make a single 10" driver produce "believeable", musical LF.

Of course, this is where the idea of multiples comes in, to increase "efficiency" at the desired (LF) frequencies, which is (paradoxically) accomplished by the rather "inefficient" means of scrubbing most of the "native" output from the individual drivers and the array.  Consider as well that this "forced curvature" does not really change the "native" output of the drivers, which results in the still-widely-misunderstood "truncated" harmonics and tone, just as most "crossovers" do.

Is it even worth talking about Tone in this context? There are few opportunities to hear Tone from hi-fi LF, so most of us are probably either resigned to do without it, or we never factor it in to begin with.  As for sealed enclosures, I have recently re-visited this idea in the context of Tone and found it wanting.  For Tone, there has got to be a way for the speaker to "breathe" that does not cause either acoustic shorts, or the nebulous softening common to BR, or the Helmholz effects beloved of the "natural sound" crowd.

Paul S
09-24-2011 Post does not mapped to Knowledge Tree
oxric
Posts 194
Joined on 02-12-2010
Post #: 28
Post ID: 17063
Reply to: 17060
Stacked bass modules from a practitioner
fiogf49gjkf0d
 Jorge wrote:
I will be dubiuos about the slanted enclosure if not done properly,  all drivers must be time aligned and since they are playing the same frequency, deficiencies in time alignment become more obvious.  I made a slanted enclosure but with the drivers facing forward, that is: out of alignment completely,  you can imagine how bad they sounded!
With the configuration you propose all drivers will be aligned and will shoot at an angle to the floor,  for the frequencies under 20 hz I hardly think this will be a problem, actually it might be even better.  For crossing at 100 hz its a whole different story...

I think one of the most important things about the lower channels is amplification and GAIN! The horn channels are too sensitive,  if we use 88 db woofers even in a huge array, lowering the volume on the horns wont really help in matching volume with the right tone and dinamic size,  more gain is needed for the bass array,  I like gargantuan gain for bass channels!


Hi Jorge,

My understanding is that standing waves inside the cabinet are driven more strongly when close to interior walls or other boundaries, in this case the floors when the drivers are firing directly at them from fairly close up in the slanted enclosure. Those standing waves can be minismised by either using appropriate strategic bracing, non-parallel walls or the golden ratios or a combination of all these.

It is interesting and pertinent that the solution your company proposes adopts one last solution, which is the use of separate individual modules, albeit that the cylindrical shape also ensures no parallel walls and you presumably use padding or a dome shape 'end' to further reduce these issues.

I refer back to your website where one can see pictures of your stacked and modular bass modules.

http://sadurniacoustics.com/bassmodule.html

I have liked the design and appearance of these from the very first time I saw them (as well as the rest of your acoustic system). They are very close to what I have in mind if I were to use multiples of 10" drivers, although I was thinking of being lazy and having two drivers per module, which in my case translates to less cost. It would be interesting to learn more about the drivers you decided to use, how you came to select them and what generally you think is the result of adding more modules and when one reaches the point of diminishing returns.

Best regards
Rakesh


..
09-24-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 29
Post ID: 17064
Reply to: 17059
Please , not again that….
fiogf49gjkf0d
 oxric wrote:
"The Macondo’s Bass Channel is line arrays. The arrays employ religiously-sealed enclosures with six “spotted” Scan Speak 25W/8565-00 drivers per channel... " Clearly you had written this at a time when you did not really understand or appreciate the concept of line arrays, or you were not able to express yourself very clearly.
  
Whatever you say, your honour. If you however clime down from your hallucination tree then you might recall that in past I used my bass tower at 73Hz, first order, the setting where the line arrays were VERY much engaged. It is much different from 20Hz and 4th order. But I do not insist in anything. Perception is reality and for some people reality is the perception.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-24-2011 Post does not mapped to Knowledge Tree
Jorge
Austin TX
Posts 141
Joined on 10-17-2010
Post #: 30
Post ID: 17065
Reply to: 17063
Diminishing returns?
fiogf49gjkf0d

The other day I was listening to a friend´s system with nice Avalon speakers, only one 10" seemed to be enough, of course it seemed we were playing house when listening to music, everything was small and very nice and pretty...

Now when matching to the big size of horns I am looking first of all for speed, if the concept can be applied; I like to define it as ease of playing, clear and transparent, well defined bass when all the notes played are present on the frequency they should be (hard to find sadly).

Now the Decay of each note played by the instruments can change according to the topology of the bass "box".  Here is where the "nebulous softening" of BR does better, nice decay tones, long sounding.  But lacking a bit in precision, some notes played might get lost in there... (great use of words Paul S.)

Sealed cabinets are good place to go with good precision and a good decay.

I find a better tone comes in when the other channels perfectly match bass in phase and size.

When designing a water pressure vessel, cylindrical shapes and domes are a must.  A pipe ¼” thick of steel can hold as much pressure as a “box” of steel 1 ½” thick!   Cylinders are much better for any pressure system; alas our system has no pressure accumulation. I just find out round sounds better than square.

What we are using is more of a BLH, transmission line thing where the back wave of the driver joins in with the front wave.  The drivers are actually 6.5 inches and there is a peripheral ring around the driver where the back wave comes out.  We made the same cabinet for 12” drivers and, besides being huge, sound was cleaner coming from a 6.5 inch driver and with a better lower extension.

I still like the tone of an Altec 416 inside a modded Karlson.

I have never found the law of diminishing returns to apply to audio!  Going crazy always sounds better, well implemented things are always better and the better your system gets, the more sensitive to upgrades it becomes, and better stuff becomes not only a better solution but a necessity.  With a good system a bad implemented tube amp will kill your ears!  The magic of nickel and M3 cores becomes so noticeable...


About the rubbery after taste, I am afraid all that Grenache might have washed it all down!
09-24-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 31
Post ID: 17066
Reply to: 17065
The best bass solution.
fiogf49gjkf0d

 Jorge wrote:
I have never found the law of diminishing returns to apply to audio!  Going crazy always sounds better…

Jorge, we need to have a perspective about those things.  With exception of oxric’s episode, who still is not able to figure out when to laugh and where to cry, the given  thread  about “Constructing LF modules to the limits” is shaping in  formulating a few approaches: 1) haralanov’s large volume from large drivers 2) Romy’s multiple of 25W driver in line array 3)yours with some cylinders of unknown design. I would like to note that it might be dozens of other completely legitimate ways to make the LF to the limit. What is very important to understand that all of it very much not compete with each other, or pout in this way: we have no framework to correlate the results. 

I would love to sit in the same will with haralanov and you, to hear his large underhaned(!) drivers, my arrays and your UFO cylinders, compare notes and learn from each other’s mistakes, successes, references and evaluation criteria. The reality is the even if it physically be possible them it would not be possible methodologically.   You see in bass reproduction there are so many “depends” and so many variables that any generalization counts very little.

If you paid attention it has been long attitude of my site is that I talk about my own practice, my own experiments, my own concussions, my own though process and my own results. Some people might feel that it needs to be “compared” to others as most of the people in audio practice audio not for themselves but for wrong idiotic reasons. The reality I absolutely assure that that the people who are driven in audio by the proper motivations do not have need to look in whose guarder the grass is greener. If you grow tomatoes because you are a connoisseur cook and you need for your salads some kind of specific texture of tomato then would not care about anything else then how to make your texture to  be the most fruitfully.  Sure you would like to have your horizons wide and open but if you are truly committed to get great test of your visualization then you use the word experience of tomato growing to improve the tomato bread of your choosing. Unless you grow the tomatoes to sell, no pun intended (you know what I mean).

BTW, I would like to pay anybody attention that the case with Haralanov any referenced are not applicable. The man makes his own drivers and his drivers can be absolutely anything. He might be very much delusional in his results and he can operate at the level of the drivers that none of us can’t even approach. No one knows and I have absolutely no problems with it. 

The most important point in the “diminishing returns” is the threshold where the “good enough” lives. This “good enough” has no diminishing return but it has only own sense of desire. Pay attention, I play not 4 drivers per channel and I do understand that to double it would give great benefit. As I told before: all that I need to do is to write a relatively small check and go to work on Monday. As I get home from work the new completed 8 woofer tower will be sitting in my room and I have absolute confidence that it will be significantly better. I do not do it because the threshold is “good enough” doe not frustrate me. Does it mean  that those 4x25W drivers are enough for my type of room? Absolutely not. In fact it means absolutely nothing and has absolutely no general conclusive value. Would I advise to go more drivers for woofer tower of my type? Absolutely! Would I criticize the other if they use Macondo-like installation and play just 4 drivers woofer towers? Absolutely! Does it make me willing to change anything? Not necessarily. You see, my aspiration to change anything has absolutely nothing to do with compliance to what is the “best”, even objectively the best. I can assure you that all people who practice audio for right reason have the very same thinking pattern. The rest are just a horde of bystanders…

I am very sure that the subject of this post of mine “The best bass solution” will be a few minutes indexed by search engines and in a few days I will have  hundreds Morons hitting my site with their search for a recipe for the “best bass”. I assure they will be disappointed. You know what, fuck them!  I am off for my “Bruckner on just 4 woofers”…

Cat_Yelow_chiken.jpg

Rgs, Romy the Cat.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-25-2011 Post does not mapped to Knowledge Tree
AllenB
Posts 3
Joined on 07-06-2011
Post #: 32
Post ID: 17067
Reply to: 17066
Getting the returns
fiogf49gjkf0d
 Jorge wrote:
I have never found the law of diminishing returns to apply to audio!  Going crazy always sounds better, well implemented things are always better and the better your system gets, the more sensitive to upgrades it becomes,


OK. I believe this gets difficult. All your problems become smaller and they are all the same size. You can be listening to two, three, five problems at once and you are working to fix just one. When you reach the point where you can't hear much improvement but you can still hear a problem, I think it is time to begin working on a different problem.

 Romy the Cat wrote:
The reality I absolutely assure that that the people who are driven in audio by the proper motivations do not have need to look in whose guarder the grass is greener.


Yes OK, but a person with the proper motivations who is also not happy with his own system will probably still look in other peoples backyards for ideas. We can't everytime simply look at a design and know if it will sound like what we want. Then, without hearing someone's system across the internet we could read some opinions, try to cut past the bullshit and find something to build to hear it for ourselves (and maybe write and tell everyone about it...).
09-25-2011 Post mapped to one branch of Knowledge Tree
haralanov


Bulgaria
Posts 130
Joined on 05-20-2008
Post #: 33
Post ID: 17068
Reply to: 17050
The tone at LFs
fiogf49gjkf0d
 noviygera wrote:
I am very curious what "properly made" means when perusing the tonal attributes of LF. What properties or specifications other than driver diameter do you evaluate when perusing a better tone?

Herman, you are asking me where does the tone comes from in context of bass reproduction? Well, this is a multifaceted subject that takes huge amount of explanations in order to be understood properly. I will mention the very basic things that affect tone.
 
What we have in a bass driver? We have a moving cone. So if we want to have good and complex tone, we have to ensure the cone will be excited in accordance to the signal of the amplifier’s output terminals. And when we see all the influencing factors, we realize we are sunk deep in the swamp. The cone is excited by the voice coil movements. These movements should mimic the voltage waveform of the signal at the output of the feeding amplifier. Here is a short list of the factors that distort that accurate mimicking.

First of all, the voice coil should move in an absolutely uniform magnetic flux during its movement, no matter how loud the driver is being pushed. It is some kind of ideal theoretical situation which is never realized in practice. Most of the magnet systems have so unstable magnetic field in their gaps, that it is very funny to call this field “permanent/constant magnetic field”. One needs truly heroically constructed magnet system to assure stable working point of its magnet and to avoid field modulations in order to ensure a stable platform for achieving accurate VC movements. There is another problem here. Achieving stable magnetic field does not ensure this field is evenly distributed through the height of the gap. In most of the cases the induction varies to a large degree in the different sectors of the gap. The difference in the field at the bottom and at the top of the gap sometimes exceeds 40%!! You can easily imagine how much distortion could be produced with that kind of motor. So one needs smartly designed motor, where the magnetic field does not collapse when the field of the voice coil pushes against it, and also it must be the same in all points in the gap. This is not cheap to be produced. Until now we looked at only half part of the problem with achieving accuracy for VC movements. Let’s see the other half of the problem. Most of the bass drivers have their VCs longer (sometimes considerably longer) than the height of the magnetic gap. It creates a whole new world of problems and distortion forming mechanisms. One does not need to be very smart to realize that with that type of motors, the VC doesn’t “see” constant number of magnetic lines when moving back and forth. This is another process causing distortion. But wait, there is even more into it! The voice coil has parasitic electrical parameters. One of them is called inductance. The self inductance of the coil acts like a build in low-pass filter inside the driver. The problem is that when the coil moves, during its movements it sees different amount of steel around it. Steel affects the inductance value of the coil and if the steel is not of a constant amount around the coil when it is moving, the VC changes its inductance constantly, depending on its position in the gap. That means there is constantly changing crossover frequency due to inductance variations. It is called inductance modulation and affects the upper working range of the driver. So if one is looking for a bass driver which he intends to use with first order filter, he has to ensure there are no inductance modulations in order to prevent this new type of distortion mechanism.

How to eliminate all these variables in order to ensure proper excitation behavior on the cone? Well, there is only one really efficient way to do that. The solution is called underhung motor and it is used by some manufacturers in their drivers. Here we have a VC that is shorter than the height of the magnetic gap where it is moving. It sees constant amount of steel during its movement and that kills the inductance modulations. Also it is driven by a constant flux during its entire movement. It lowers some types of distortion to nearly zero level and eliminate transient compression. And this is very important.
 
At the second stage, we realize that although the coil moves in stable and constant magnetic field, its behavior is hugely dependent by its electrical interaction with the driving amplifier (that’s why the tone is dependent from the amplifier/speaker interaction). We need the current flowing in the voice coil to change in the same manner as the voltage waveform at the output of the driving amp. This is very difficult to happen because there are eddy currents flowing in the iron (this is the former material of the magnetic circuit) and there are hysteresis loses in that iron and all this distorts the current flowing in the coil. The human ear is very sensitive to that type of distortion, so all the good speakers have very serious magnet systems where some efforts are taken to break up these eddy currents and to lower that nasty sounding distortion mechanism.  Speaking of speaker-amplifier interface, I have to mention that every amplifier need exact amount of wire length in the gap in order to drive the VC properly. That’s the reason why most (practically all) of the bass drivers do not sound good with solid state amps. It is not because the solid state amps are bad, but because they need low inductance/resistance voice coils in order to work/sound properly at LFs. There is also another phenomena: imagine you have two bass drivers with identical moving parts and with identical magnet systems. The difference between them is in the type of the voice coil. The first speaker has 2 layers with 30 turns per layer (60turns in total) and the second speaker has 1 layer of 60 turns of exactly the same wire. The DCR of the two coils is the same, but the 1-layer coil sounds much better compared to the other. But why?? Do not ask me why – I do not know. I only know it affects the tone a lot, and I simply get use of it, without any explanation why it happens. 
 
When all of these 5-6-7 different types of distortion mechanisms are eliminated (I mean lowered), one has the opportunity to hear the unmasked/undistorted tone of his bass. I deliberately used the word “opportunity” because now we have to convert those accurate VC movements into sound waves and if we fail to do it, we will not get good tone out of our bass drivers. Good example of this kind of failure is JBL 1501Al bass driver. It has very very very smartly designed underhung motor, but its moving system is crap and the result is a lack of tone in its sound.
 
OK, now let’s imagine we have kind of ideal situation and our voice coil follows exactly the signal waveform and amplitude. We have to convert those movements in air molecules excitation, and this excitation should mimic exactly the VC movements. We further realize that we are not only deeply sunk in the swamp, but we are on the bottom of the swamp.
 
What we need to have uncompromised moving system? We need to attach to the VC a cone that has density equal to the air density and at the same time to have as much radiating area as possible in order to achieve good efficiency. That type of cone does not need any suspensions or electrical damping to reproduce the signal precisely. But unfortunately we do not live in an ideal world, so we need to think for a while how could we get as close as possible to the above mentioned criteria. So the first thing we need to do is to find a material having mechanical impedance as closer to the air mechanical impedance, while being rigid enough in order to maintain accurate behavior. We realize the only suitable material is long-fibered paper. Now we need to “invent” smart cone geometry to make the cone rigid enough by using smart construction geometry and not stiff materials. There are a LOT of tricks here, but I will not mention any of them. All this affects tone a LOT. But we need our cone to flex very gradually in order to avoid nasty break-up peaks, because every material on this planet flexes at some point when there is applied enough mechanical acceleration to it. Just a quick illustration: take a look at the following video (the part at 4:27-4:35):
http://www.youtube.com/watch?v=QFlEIybC7rU&feature=related
You can clearly see how this obviously rigid baseball bat flexes like an elephant ass when there is enough force applied to it. The same happens with speaker cones. The whole trick is to take control over these break-ups. It influences the tone a lot when the driver is being used over a wide range (this is the case with 1st order filtration).

Now let’s imagine we have two identical voice coils. The first one drives 8” cone and the second one drives 18” cone. What happens? Since the bigger cone has more radiating area, it reproduces the LFs more efficiently and its tonal balance is centered at lower frequency compared to the small cone. The small cone has higher amplitude for the upper range of the input signal and its tonal balance is more upward oriented (Paul already mentioned that, and he very intentionally used irony when calling a 10 inch driver to be a “bass” driver) although it is perfectly suited to reproduce low frequencies if having low Fs. So properly designed big cones have better tone and higher efficiency at lower frequencies compared to small ones.
The less radiating area of smaller cones, means there is less coupling to the surrounding air. That means there is less air control to the cone movements and now these movements must be controlled by different ways. One needs harder suspended cone in order to control these movements. Of course this type of cone control has negative consequences to tone, because it acts with no own intelligence – it just blindly resists to these movements, applying a force in order to turn back the cone at its rest position. This process inserts its own tone and adds its taste to the real tone. Air loading does not have this behavior defect and it controls the cone in a smart way, applying no own intelligence, thus allowing one to hear more complexity of tone at LFs.

There is one drawback of using too  big cones for bass. This drawback is due to the raised moving mass compared to a smaller cone. This mass stores kinetic energy and if this energy is not damped by the air/suspension, it makes the VC to generate more back voltage and sent it directly to the driving amplifier in different point in time (after the original signal that feeds the VC). The amplifier should be able to absorb that energy. Sometimes this is a big stress for smaller amplifiers and they go really crazy while trying to absorb that energy, especially at Fs of the system, where the returned energy is returned in different points in time. The more powerful the amp is, the better it resist that sent back energy coming from the bass driver’s VC. By the way, that’s one of the main reasons why low powered amps cannot drive the big woofers with confidence:
http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=9390#9390
  
Now when we have good driver with high tonal potential at LFs, we have to find a way to use it. We have to prevent acoustic shortening effect. There are a lot of possibilities how to achieve that. Every solution has its own character, because its affect the cone behavior. The best way to ensure undistorted cone movements, is to load the cone symmetrically. The air loading from behind the cone should be the same as the air loading in front of the cone. This is satisfied with infinite baffle configuration. In this situation there is a lot of air behind the cone and it breathes freely in the air, providing pure tone to the listener. Every closed volume of air behind the cone manifests itself like a breath-blocking device, no matter how damped it is from the inside. Make a simple experiment: take huge amount of damping material and insert it in your wardrobe. Now put your head inside and listen carefully. You feel your head is inside a small and highly damped chamber. Very unnatural feeling, isn’t it? Now take your head out of your wardrobe and go outside in your garden. How do you feel now? Do you feel the freedom and lack of closed and stuffed chambers? Yes? Well, the same is true in context of your bass driver operation. You can always recognize there is trapped air volume behind the cone. This affects tone too, although there are no air-born resonances, due to the heavy internal acoustic damping.
 
The vibrations of the acoustic shield (the “box”) also destroy the Tone. If one wants to hear real bass tone, he must take all those sound-poisoning vibrations out of the picture. The material that really do this job well is the sand. I know there are some people who state, the acoustically dead/inert cabinets destroy tone. And the fun part is they really do not imagine it – it really happens sometimes, but there is a reason why it happens. The reason is because they are Гевреци/Gevreks (Morons) and they use tonally dead drivers. What else could they expect, besides dead tone when using tonally dead driver in acoustically inert enclosure?? So they “fix” the problem by using mechanically resonant enclosures, calling them “musical instruments”!! These wide-band resonators really make their dead drivers to sound more alive and with more “tone” but in reality it is just the opposite situation – they have nearly zero tonal complexity, because the bass tone is highly polluted with cabinet colorations. The lower the parasitic resonances, the more complex the tone becomes.
 
The type of filtering also affects LF tone. With first order low-passing, the bass channel sounds like the missing part of my widerange/upperbass channels combo, but with sharp filter it sounds much like a self contained sound that is not part of nothing. It lives its own life and although it could be +/- integrated with the other channels, this integration is light years away from 1st order filtering integration abilities.
 
There are many other factors, affecting the tone at LFs, but the people who are really interested into this, are going to learn those factors by themselves.
 
Best regards,
Petar Haralanov


"If you can't explain it simply, you don't understand it well enough." -A.E.
09-25-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 34
Post ID: 17069
Reply to: 17068
The blind contribution of driver suspension.
fiogf49gjkf0d
Petar, wonderful observation as usual. I would like to add one factor that is always there but practically impossible to consider predictably.

Any driver has suspension (with exception of suspension-less drivers that are not suitable for bass) and the properness of driver reflecting of what the signal goes is very proportional to the driver excursion. When cone moves from 10% to 70% of it max excursion then it is experiencing the resistance of suspension let say 7 times stronger. The suspension resistance is not the force the is informed about the signal and it behaves purely mechanical, reacting only upon the driver excursion. So, with any driver, regarding of design the excursion means higher introduction of signal not related anomalies. With use of multiple divers we accomplish exactly that – we spread the excursion of one large woofer to the let say 4 mini excursions of small woofers, minimizing the total participation of suspension in the entire ceremony. We spread not only excursion but also flux modulations, thermal compression of VC and many other factors that are much less at low excursion of the small drivers. BTW, we play the same game with horns, where we by adding horns to get more acoustic pressure allow themselves to use the drivers with fewer excursions.

For sure the blind contribution of the driver suspension in 10” driver and 20” are VERY different. And it is possible that 20” driver ay 80% excursion will experience less stress from suspension then 10” driver at 20” suspension. I say “possible” because there is no way to evaluate it properly as no one makes identical 10” and 20” drivers. If someone would make 10” drivers with excursions, suspension and magnetic system of 20” driver then use of multiple 10” drivers would be no brainer and it would 100% preferable then to use one 20” driver.  Of cause it is never the case and in real world to predict how different drivers behave is very hard it is all about the specific driver construction.

Now about the tone. Petar, you use 60Hz first order and of cause the tonal concepts are important to you. In your estimation would you feel the same if you use 20Hz and 4th order? I did listen my ULF sections without the rest of Macondo, trying to get a sense if “tone” is something the I was able to hear in there. I did not recognize that there was anything in there that might have a tone. I did heard the dynamic compression but not tone per say. Can you put 20Hz and 4th order on your driver and share what you hear?

Rgs, The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-25-2011 Post does not mapped to Knowledge Tree
haralanov


Bulgaria
Posts 130
Joined on 05-20-2008
Post #: 35
Post ID: 17071
Reply to: 17069
Excursion distribution and tone below 20Hz
fiogf49gjkf0d
 Romy the Cat wrote:
With use of multiple divers we accomplish exactly that - we spread the excursion of one large woofer to the let say 4 mini excursions of small woofers, minimizing the total participation of suspension in the entire ceremony. We spread not only excursion but also flux modulations, thermal compression of VC and many other factors that are much less at low excursion of the small drivers.

Yes, I agree with that. Actually I’m doing the same – to spread the excursion of one large woofer to multiple large woofers. This also lowers the flux modulations, thermal compression and distortion (just like with using multiple small woofers) but with the added benefit of huge sensitivity at lower frequencies, because for a given current flowing in the VC, the bigger driver has several dB more output, better acoustic control at Fs and better tone too. Controlling the cone movements at Fs with just efficient air loading of the cone, allows me to use softer suspension, which has very linear behavior at low to moderate excursions, so the drivers will actually operate in ultra-linear mode when used at just 4-5mm of total excursion. And because of the high sensitivity, every one of them will eat no more than 2-3 Watts to produce very high SPL at LF.
 
 Romy the Cat wrote:
Now about the tone. Petar, you use 60Hz first order and of cause the tonal concepts are important to you. In your estimation would you feel the same if you use 20Hz and 4th order? I did listen my ULF sections without the rest of Macondo, trying to get a sense if "tone" is something the I was able to hear in there. I did not recognize that there was anything in there that might have a tone. I did heard the dynamic compression but not tone per say. Can you put 20Hz and 4th order on your driver and share what you hear?

I plan to use my future woofer towers to 40-42Hz (first order), so I very much care of the tone at these frequencies, but in your case, using them below 20Hz with such a steep low pass filter, it is completely different situation and I think it doesn’t matter what kind of drivers produce that subsonic pressure. Nobody hears any tone below 20Hz, so practically it should be of no consideration. Of course I may be wrong about that – I don’t know, because I have never tried to use infra bass channels. Maybe the only requirement for the driver is to have very low Fs in order to prevent excessively eating of power in order to move/push the cone below its Fs…
 
Best regards,
Petar

"If you can't explain it simply, you don't understand it well enough." -A.E.
09-25-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 36
Post ID: 17072
Reply to: 17071
Tome and bass note and tone in general.
fiogf49gjkf0d
Yes, if you are at 40Hz first order then you are with regular dedicated LF channel and tone is certainly a subject. The entire definition of ULF channel inkstand or LF channel is that ULF channel has no tonal information. It is very same like use tweeter after 12.5K. I use ribbon tweeter that I feel has near zero tonal capacity but it is all right with me as there is no “tone” after 12.5K.

BTW, reading your comment I feel that whatever you said has very little to do with tone of LF section. There is nothing wrong with whatever you said but all said describes why some drivers do not have tone. It does not describes why some of them do have good tone and BTW they might have great tone despite not being in compliance with some agreeable design rules. I personally do not feel that bass tine come from anything but materials. Papers, glue, suspension, oil the suspension, the cone soaking – all of it and a few other factors serve what I call “absolute tone”. Then there is dynamic tone, and tonal discrimination. Those last two comes from only God knows where. Some of the drivers have it, some more and some less but administration of it is terra incognita in audio. We most know about surface of Mars then how to make tube plate of driver cone to sound more patriotic during play of the Chopin Etude op. 10 or more mourning during play of Saint-Saëns last symphony second movement.

To combine the specific tonal objective with the all together proper performance of the driver/channel is VERY hard, if even possible in the same driver. You make your own drivers, your might gig into some of the aspects. Still, I do not know any single makes of drivers who can fulfill tonal requests by demands, while keeping the all around performance of driver not compromised. I knew one cartridge manufacture why make this claims and who claim that he can make cartridges with specific tonal request. Still, after receiving private emails from that manufacture with him privately admitting the he is a full of shit and request his hypocrisy never be exposed to public I know that his claims worth absolutely nothing. So, I do not know of any occasions where we have control over tone. We can make  some action that would most likely give more or less success with tone but in my estimation we not own the process.

Rgs, the Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-25-2011 Post does not mapped to Knowledge Tree
oxric
Posts 194
Joined on 02-12-2010
Post #: 37
Post ID: 17073
Reply to: 17068
Petar, thanks for that brilliant expose of the art of building drivers.
fiogf49gjkf0d
 haralanov wrote:


When all of these 5-6-7 different types of distortion mechanisms are eliminated (I mean lowered), one has the opportunity to hear the unmasked/undistorted tone of his bass. I deliberately used the word “opportunity” because now we have to convert those accurate VC movements into sound waves and if we fail to do it, we will not get good tone out of our bass drivers. Good example of this kind of failure is JBL 1501Al bass driver. It has very very very smartly designed underhung motor, but its moving system is crap and the result is a lack of tone in its sound.
 
OK, now let’s imagine we have kind of ideal situation and our voice coil follows exactly the signal waveform and amplitude. We have to convert those movements in air molecules excitation, and this excitation should mimic exactly the VC movements. We further realize that we are not only deeply sunk in the swamp, but we are on the bottom of the swamp. 

...
 


Hi Petar,

When I revived this long dormant thread, and asked you about the fallout from your efforts with the Scanspeak drivers, little did I imagine that this would provide me eventually with a glimpse into the science or dark arts, depending on how one perceives it, of making drivers. As you make abundantly, vividly and succintly clear, the construction aspects of building a driver wilst retaining some degree of control over how it will eventually sound are so complex that I am not surprised that most people, no matter how good their playbacks otherwise might be, would never dream of building their custom-made drivers with every slightest element tailor made to fit in with their vision and understanding of Sound. Whether it in the end works or not, it is an experience that in itself must give one a profound connection with the listening experience. I am truly amazed as I would have thought that control over every aspect of construction such as the magnetic assembly, the voice coil assembly, the making of the cones, the long, arduous and painstaking iterative process of trial and error involved would require specialist tooling that would not be easy to come by unless one is in the business of making drivers.

It is quite different to the experience of going on ebay, buying a random pile of drivers and by an incremental but oh so predictable process of elimination, which may well end not because of ensuing success but because of the accumulation of frustration and fatigue, reach a point where one declares the results perfect or 'just good enough,' to which most of us are condemned.


 haralanov wrote:

 
There are many other factors, affecting the tone at LFs, but the people who are really interested into this, are going to learn those factors by themselves. 
 


I am really curious in the drivers you are building but doubt most people are going 'to learn those factors by themselves.' The skills, the time, the resources are unlikely to be present that can support such an endeavour even if the interest is there. So to indulge my curiosity, if you do not mind, if and when your system is up and running, please let me know and I shall pay you a short visit to Bulgaria (direct flights to Sofia leave less than half an hour from here) and listen to your playback, if that's not too much bother.

Best regards,
Rakesh


 
09-26-2011 Post does not mapped to Knowledge Tree
el`Ol
Posts 225
Joined on 10-13-2007
Post #: 38
Post ID: 17074
Reply to: 17073
Go transconductance?
fiogf49gjkf0d
A $$$ solution for a bass array that comes into my mind are the sandwich cone drivers from Accuton.
Monstrous neodymium magnet, underhung voice coil (for low flux modulation).
Very low Fs.
Relatively low QMS for use in sealed enclosure with transconductance amps (zero thermal compression).
http://www.accuton.de/drivers/list.php?&m1=2&m2=2&m3=0&matID=2&appID=4
09-26-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 39
Post ID: 17075
Reply to: 17074
I truly hate Accutons.
fiogf49gjkf0d
 el`Ol wrote:
A $$$ solution for a bass array that comes into my mind are the sandwich cone drivers from Accuton.
Monstrous neodymium magnet, underhung voice coil (for low flux modulation).
Very low Fs.
Relatively low QMS for use in sealed enclosure with transconductance amps (zero thermal compression).
http://www.accuton.de/drivers/list.php?&m1=2&m2=2&m3=0&matID=2&appID=4
The Accuton drivers are subject of my hate for many years. They what I call “soft” bass drivers, it means the suspension is very soft with huge exertions. When I see the Accuton drivers working it is scare as they move back and forth like crazy, I truly do not like it and I always like the “hard” suspended drivers. This classification on soft and hard suspended drivers does not have any sense and I perfectly see people replay that I am an idiot. I am not. There are some drivers with identical Fs that while produce the same bass notes some of them move more and some other move less. I know that bass peruse is diameter by excursion  and I have no explanation why some excurt more and some do less. What I know that those that excurt less do sound better to me. BTW, my 25W drivers are something the I consider “excurt less”, I did run one single driver and look how it move back and forth – it was not a lot, at list much much lover then some other drivers I have see and MUCH lover then what Accutons do.

Also, Accutons, in my experience are dangers drivers as they behave very badly as they reach Xmax. When I overdrive any other driver with amp then, along with huge distortion you might hear some VC rubbing. The 25W drivers do it in very soft way and they do not get damages. The reportedly “underhung” Accutons when they move all the way out produce absolutely horrible very unpleasant sound. Furthermore the drivers like 25W have sort of similar structure of cone, location when the cone is glued to suspension and suspension. You can touch and knock any of the driver location and it will response virtually identical. This is what I like. The Accutons are very different animal. The stiff cone responds with very good LF response but when you knock or rub the ultra soft suspension then you have nothing in response. The suspension is in my estimate is too soft for the cone and the cone and suspension act like very different vibrating entities. This is very bad. In my past I had one even when I was experimenting with a speaker that had Accuton bass driver and the driver VC jumped out of the gap (talking about the underhunging!) but did not jumped back into the gap straight. So, as the result the cone shucked at ~20 degree, fully exerted. The driver was goner. I had another story when I was playing with another Accuton-arm speaker and the cone was also jumping out of the gap and in it’s way back it rubbed the edge, coursed the cone fracture up on 10000 small pieces. It was very expensive speaker and I was forced to pay the speaker owner to replace the driver.

So, Accutons in my view are drivers the must not be touched. Saying all of it, I might presume that if to have very many of Accutons, let say 10 in the array, where they will not move back and forth too much and will have large power handling, then it might be the only way to use them. Still, the fact the in Accutons cone and sustention live with their own lives make to me Accuton is absolutely ridicules driver.

I know there is company put there, I do not remember the name, that do a very expensive speaker with dedicated LF module that has 4 Accuton woofers. I heard it a few year back in Vegas and it was very wrong bass. Sure there are zillion other reasons why bass was bad in the show but it was very much the same bass that I would expect from Accutons.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-26-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006
Post #: 40
Post ID: 17076
Reply to: 17075
The "Perfect Piston" BS, and LF vs. ULF
fiogf49gjkf0d

Until people actually start to listen to and correlate well-determined sound with pieces and parts, they are going to continue to spend money on BS "engineering" ideas rather than listening their way through Musical options.  "Underhung" and "Perfect Piston" are great examples of ideas that actually do bring something useful to the table but, at the same time - as ever - they bring their own problems, as well.  One thing that has to be well-determined ahead of time is whether we are talking about "LF" or "ULF".  The difference is not small, IMO.  We certainly ought to consider Tone at LF; but with ULF ALL bets are off, except that no matter what you start with you will PROBABLY wind up with something else.  There are other GSC threads that address the ULF issues, but I think ULF may well be a case where money and "SOTA Technology" can actually be used to good advantage, if the speakers and the amps and the tune-able X/Os are considered at once.  However, ULF and LF are not really so similar, at least not where Music is concerned.  If anyone cares, the Accuton is wrong for "LF" because it cannot make Music.

Best regards,
Paul S
09-26-2011 Post does not mapped to Knowledge Tree
Jorge
Austin TX
Posts 141
Joined on 10-17-2010
Post #: 41
Post ID: 17077
Reply to: 17076
Apples and Oranges
fiogf49gjkf0d

We should define some borders here; LF, when you have an UBH, should be from  around 100 hz down to 30 hz,  where the last fundamental tone of an instrument is played.  ULF should be under 25-20hz.

I would say that a driver playing 25-30 hz should not go over 100 hz, as tone becomes very important there. 

Most of us are using some sort of cabinet for the LF range.  Romy was using the Scanspeak up to 75 hz crossed to his UBH,  Haralanov is using those wonderful 23" woofers on an infinite bafle, and Jessie is using the McCauley 18" woofer on some sort of concrete coffin!

Romy is now using midbass horns to cover this LF range,  but he needed to change his house in order to achieve this; Talk about an upgrade, a MB horn with swimming pool inlcuded!!

Haralanov solution looks wonderful,  but given the sheer size of his Infinite Bafle and the construction planned, would it not be better to make a Big horn instead?  Of course he uses an open bafle midrange and is not into horns, so for him this is the right solution,  but If we do use horns...

I could be wrong as usual, the law of diminishing returns for going from 6 woofers to 8 woofers for a tower that you cannot listen,  that starts at 20 hz and under, it might be getting to the that point!  Of course if vibration is needed the more area the better,  but how much? 

Now adding more woofers in the LF range is good until it gets so big and complicated, that adding a time aligned Mid bass horn would actually be simpler!

I think  would go for the Horn most of the times!
09-26-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006
Post #: 42
Post ID: 17078
Reply to: 17077
From 30 to 20 Hz In Just a Few Keys
fiogf49gjkf0d
Can we really say that the "lowest fundamental" from an orchestra is 30 Hz?  I sort of wish it were true!

Something I think we can all agree on is that hi-fi tends to suffer from lower fundamentals and harmonics that are not properly proportioned, and -  in the case of LF -  the lower fundamentals and harmomnics may well be MIA. However, at LF it is not sufficient - in terms of Music - to simply pump the "flat" response into the room, but the "flat" response "result" must come from  properly-balanced response/production "at the source", eg, the speaker (or -  more properly -  the driver).  The bitch in terms of "reproduction" is that Music doesn't "hold back" at LF (quite the contrary...), but to "reproduce" LF we have to go through more and more mechanical and electronic gyrations as the frequency drops, even 1/2 octave, exponentially so, relative to MF or HF.

Again, adding woofers will only get you so much at LF.  Mere "gain" is not enough.  For Music there has to be Tone, and I think in the end this will only come from "proper" sound from the (single) LF driver.  If one had the room, who would not choose IB for LF? How might "IB" be well implemented in a home?

Best regards,
Paul S
09-26-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 43
Post ID: 17079
Reply to: 17077
Most of us are using…
fiogf49gjkf0d
 Jorge wrote:
…Most of us are using some sort of cabinet for the LF range.  Romy was using the Scanspeak up to 75 hz crossed to his UBH,  Haralanov is using those wonderful 23" woofers on an infinite bafle, and Jessie is using the McCauley 18" woofer on some sort of concrete coffin!
 Iwould like to remind the user that this is not DIYAudio website and collaboration of the methods is only a small fraction of objectives. Would it be small coffins, large coffins, horns, open baffles or infinite baffles, that all does not describe and does not define the bass that any of us are getting.
 
People looks like obsessed with technological aspect of having less compromised bass, there is nothing wrong with it but the perusing the non-compromise bass doe not necessarily assures the proper bass in real listening environment. What I am trying to say is that besides all technical and exoteric justifications I would like more to hear about your thoughts regarding the lower bass and how do you find your bass is different from the bass that you feel would be satisfying to you. Do not forget that we all shot in the very different targets until we know that we shot in the same target….
 
The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-27-2011 Post does not mapped to Knowledge Tree
noviygera


Chicago, IL
Posts 177
Joined on 06-12-2009
Post #: 44
Post ID: 17080
Reply to: 17068
Some thoughts in a positive direction
fiogf49gjkf0d
Petar,

I thought for along time how to reply to your post. All my thoughts basically narrow down to this. You're a soulful guy. There is nothing smart I can say to add or subtract to you findings but I think that the result you will finally get from your LF "end of all searching" is a very refined and "soulful" signal reproducer. That's good to know because this "soulful" characteristic of sound has not been explicitly described anywhere -- as means AND the end of getting to the righteous result but now there is a rough guide.

So this 23" multiple woofers project of yours is part of the means to the goal. I believe that the infinite baffle is also a good idea. It will take you in the right direction but do not mount those woofers behind your listening position. I tried that and it's tonally good but it's confusing as hell to the brain even if crossed over 80-100hz, still confusing. Put them in front or on sides, where the main channels are. That's my experience.

Also, there must be a good ratio between the speaker cone area and listening room volume to get proper tonal pressurization of the listening room. What that area is I do not know but it is a lot more that two 23" woofers for a normal sized room, I believe (see ps note). I'd like to try at LEAST two per channel, positioned behind each channel.

Since you strike me as a person of soul, I would love to hear your result from using those 23" woofers. If they are good, why not make more and sell them.
I am currently looking at multiples of 18" to 24" woofers (Precision Devices or Hartley), even wondering about that 31" Fostex.

Thank you for your reply.

Herman

p.s from my experience of having a 500 sq. ft. listening room with 7 ft. ceiling and having two 18" woofers in a infinite baffle configuration, it is not enough to pressurize the room. I am talking about low and medium listening levels. Four 18" would be just acceptable. Eight 18" woofers in infinite baffle will be good for a 500 sq. ft. room so there is your rough ratio according to my experience.
09-27-2011 Post does not mapped to Knowledge Tree
be
Copenhagen, Denmark
Posts 86
Joined on 02-12-2007
Post #: 45
Post ID: 17081
Reply to: 17080
Is there any tone in the ULF range?
fiogf49gjkf0d
It seem that the concensus here is that there is no tone in the ULF range, something like below 50Hz.

This is probably not true for live acoustical instruments.

Physical systems that can be described by non linear differential equations, are known to produce subharmonics of there fundamental frequency, combination frequencies of these and the harmonics and on top of this: harmonics of the forementionned!

Acoustical instruments are highly nonlinear mechanical devices and does indeed demonstrate these phenomena:

http://en.wikipedia.org/wiki/Subharmonics

Further, some instrument has an almost DC component as well, try to say the letter sound of "P" loudly.

Rgds.
be
09-27-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 46
Post ID: 17082
Reply to: 17081
Sorry, they are incorrect premises.
fiogf49gjkf0d
 be wrote:
It seem that the concensus here is that there is no tone in the ULF range, something like below 50Hz.

The range “below 50Hz” is not ULF range. Below 50Hz is regular LF or regular bass region. The whole definition if ULF is that ULF is the LF message that is not registered and recognized as sound. Playing ULF you shall not be able to not only recognize music but to be able to say in most of the case the music even is placing. If you can say what is being played by ULF then it was not ULF but regular bass channel. In my estimation ULF stars around 25Hz with shaper then 2 order filter.

So, the most of what being discussed in thread there is not ULF but bass channel. There is absolutely nothing wrong with it and in some cases the bass channels might do low enough that ULF would not be necessary. Still, I feel that question tone in ULF range is like cooking a soup with poisoned mushrooms and to think about a proper amount of salt in it.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-27-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006
Post #: 47
Post ID: 17083
Reply to: 17081
Another Look at the "Problem" (and Branding)
fiogf49gjkf0d
Be, thanks for bringing  up the "subharmonics" in the way that you have done, for another good look at the elusive-to-hi-fi "undertones".  I have been bitching about and futzing with this for ages, and now am I working with the drivers, themselves, to better understand and address this (among other things).  Yes, this "structure" certainly exists in life, as those with ears can hear, and it won't be dismissed, nor (IMO) can it be "simulated" with electronic boost, at least not with Musical integrity.  No, to get this right for Tone, it has to be gotten right from the "beginning".  The Idea is to hang on to as much as possible without effing up something else to the point of diminishing returns.

Herman, the pressure is certainly something that can work both with and against other LF "features", and I think the "balance" can only be gotten with the "Serious Music".  I agree (at this time...) that for LF, "more is better" at "the source".  By this I mean that nothing about Romy's "20 dB Axiom" changes at LF, except it is MUCH harder to do "properly" at LF. Typically, we see/hear what amounts to an "inverted" version of the "LF" driver's output, achieved by some combination of amplification and attenuation.  Or, we see/hear the "thunder machines" that have nothing whatsoever to do with Music.  Of course, it's up to each of us to decide how we will deal with the many conflicting LF issues.  Just now, my "thing" is Tone, as I have described extensively.  Generally speaking (and I'm sure you agree), I think anyone could draw closer to a personal solution if he knew more about the "qualities of Sound" that make the Music he wants (and expects) to hear, as opposed to trying to figure out "which brand is best".

As for ULF, I mostly agree with Romy, and I think there is already some pretty good information in the GSC ULF threads, right now.

Best regards,
Paul S
09-27-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 48
Post ID: 17084
Reply to: 17080
What is your reasoning?
fiogf49gjkf0d
 noviygera wrote:
p.s from my experience of having a 500 sq. ft. listening room with 7 ft. ceiling and having two 18" woofers in a infinite baffle configuration, it is not enough to pressurize the room. I am talking about low and medium listening levels. Four 18" would be just acceptable. Eight 18" woofers in infinite baffle will be good for a 500 sq. ft. room so there is your rough ratio according to my experience.

Herman, I would like to ask what methodological reasoning you uses to assess that your room of 500 sq feet having two 18" woofers in a infinite baffle it is not enough? Do you feel that not enough bass? You do not have more power or gain in your amplification? Do your drivers excurt too much? Do you hear too high distortions or compression?  Do you have measurements in the room at the frequencies that you are interested in?

The reason I ask as I feel that 4x 18 inchers for 500sq feet room is certainly wonderful but it is nowhere near absolute minimum. A good pair of 416/515 drivers with moderate 40Hz would perfectly fine for 500 sq. ft. Sure the more drivers and more size is better but when we do it we just minimize the excursion of each driver and improve sound by spreading all problem across multiple transducers allowing each transducer to be not as good as a single driver. Anyhow, I would be interested to know how you came to the concussion you have came. 
 
The caT

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-27-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,156
Joined on 05-28-2004
Post #: 49
Post ID: 17085
Reply to: 17080
Full-back position for LF
fiogf49gjkf0d
 noviygera wrote:
… but do not mount those woofers behind your listening position. I tried that and it's tonally good but it's confusing as hell to the brain even if crossed over 80-100hz, still confusing. Put them in front or on sides, where the main channels are. That's my experience.
Cut shorter with Tchaikovsky, Stravinsky, Ravel and R. Strauss and movie to Brahms, Bruckner Beethoven and Bach. You will very fast minimize the brain confusion with location of your woofers behind your listening position. Also, you need to have very prodigious crossover point and very accurately set volume with mandatory from channels “override” to facilitate the back position. I however did not experiment with full-back position but back-above position but I think with full-back it still might be double. If you would like I might elaborate about back position for LF in a separate thread.
 

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-28-2011 Post does not mapped to Knowledge Tree
be
Copenhagen, Denmark
Posts 86
Joined on 02-12-2007
Post #: 50
Post ID: 17089
Reply to: 17082
The point..
fiogf49gjkf0d

It is difficult to say below what frequency there is no sound registered, the lowest fundamental on a double bass is 41Hz and the A0 on a grand piano is 27Hz, both these fundamentals and at least one harmonic  thereof would probably be recognizable with a 25Hz second order filter.

The violinist Mari Kimura can with her instrument produce sub harmonics one octave lower than the fundamental of violin. Something similar might sometimes happen with other instruments to.

 The movements of the musicians is often heard or felt because the stage floor of a concert hall. The stage floor would have a fundamental frequency of maybe 5Hz, with the first 2-3 harmonics below 25Hz.

All this does not support the idea to call below 25Hz ULF based on the tone of reproduced acoustical  instruments.

Instead of defining the ULF range from the reproduced instruments, it is much smarter to do it based on the first resonance frequency of the listening room, because the frequency response of a closed room has a 12dB/oct rise in frequency response, due to the cavity effect starting approximately half a octave below the fundamental mode of the room.

This effect could be balanced by the natural 12dB/oct. fall in response of a closed box speaker, with a Qts of app. 0.7 and below its resonance frequency.

If the listening room is not leaky and with solid walls, a flat response down to a few Hz might be possible without equalizer.

Obviously one does not have to cross to a ULF channel below the fundamental frequency of the room to use this effect, but then the knee/ resonance frequency of the closed box should be placed there.

Rgds
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