Now that is what I call a woman.

Nice; I can smell the metal.

Dominique, let's have a beer sometime.


jd*

Im in the process of building a pair of 115hz MDF horns.  Any suggestions, on the size and type of vent for the the back chamber? Ive seen Jessie's implementation but I am pretty sure I will not be able to do that in my situation.  I assume a simple hole sealed with silicone would not suffice given the amount of pressure build up in the rear chamber? Thanks in advance!

Jp,

what do you mean by “vent for the back chamber”. Why are you planning to make the back chamber vented?  The side would be depending from the type of your driver, but generally it will be always smaller then you think.

The Jessie's implementation is unquestionably wonderful if it is easy for a person to do but I with all sincerity ask if it necessary to go into this extend. The back chamber setting is one time deal (per a driver) and there are many other ways, way less demanding but identically effective, to set the back chamber’s size.

jp wrote:

I assume a simple hole sealed with silicone would not suffice given the amount of pressure build up in the rear chamber?

The pressure that builds up in right rear chamber is truly enormous.

jessie.dazzle wrote:

… adjusting chamber volume will not be as convenient as turning a threaded shaft, but once the correct volume is found, you're done.

Even when we are talking in context of one non-changeable driver it opens up a ground for a great discussion: what happen when the resonance of chambered driver and mouth rate “almost” match? We have a few variables: the type of the driver and the location of the horn in the room. It is easy to measure where the Fs of chambered driver sits in relation to the horn’s rate. However no one ever told about what happen with Sound when the Fs ascend for ½ hertz. It might be that the precision in it is not important at all but it also might be that a very precise dialing of Fs creates some interesting sonic benefit. How, that “precise dialing” might be changed by driver or by position of the horn relative the back wall only God knows.

Sure, the “smart” people use the HornResp… :-)

jd wrote :

"...I may have come up with a way of making the BIG horns fairly painlessly..."

Yes well, I really must give up the absinthe !

Lbjefferies7 wrote :

"...Not "end-of-life"in the sense that it will be built and then I'll never have to mess around with speakers again, but more in the sense that it's a project that will likely kill\cripple me..."

Been a bit slow on posting progress reports lately because I've had to delay construction of the second mid-bass horn. This was due to having herniated a disk in my back while moving the first mid-bass horn out of the way.

Here it is (throat = 8", cutoff = 40Hz)... Just test-listening here ; no filter, no rear chamber, driver not securely fixed but just placed on a box... Original plan was to listen for a few minutes, then get it out of the way and start on the second horn... I ended up leaving it in place for about a week, eventually adding an approximate filter :





Photos were taken about 3 months ago... Horn is laying on its side; shold be rotated 90° with short side on floor.

Still lots of finish work to do... Finish work will commence once second horn is to this same rough state.
I am now back to work on the second horn, which is about 1/4 of the way done. It is extremely boring and repetitious work.

Lbjefferies7 wrote :

"...My system certainly follows the 'form follows function' rule but I have wondered how the looks of a speaker (or entire system) effects the listener's perception.  Of course we have all experienced some male grunting and hooting over the shinny things and glowing tubes.  This only led me to believe that the appearance of a system can theoretically produce a more sophisticated and music-friendly perception.  How to accomplish this while keeping axioms intact is a daunting challenge..."

I chose to give priority to the axioms... In the case of these mid-bass horns, my intention is to leave the deeply ribbed exteriors out in the open, letting them work as diffusers for the mid and high frequency channels (their primary function being of course structural). These horns will eventually get a coat of semi-flat black paint inside and out. I may one day (if forced by a woman) have to build a sort of case around the outside of each one, or build them into a house.

jd*

To answer Romy's questions :

Drivers :  

Vitavox AK151

Resonant frequency  :

I did not try to measure it. Can anyone confirm the following : I assume this parameter is most easily determined by playing a series of tones at constant signal strength (volume setting) while measuring the SPL; the frequency of a tone that gives the highest SPL is the resonant frequency of the assembly. Is this correct?

Filters : 

Initially I ran the horn full range, without the other horns. I was immediately sort of horrified at how high (in frequency) it would play. I then stuck a 5mH coil in front of it, so as to low pass somewhere around 200Hz (really could have used a 3.5mH coil, but didn't have one on hand). Next I made a band pass filter to give a theoretical operating range between 90 and 185 (normally I'd let it go higher, to around 250Hz but again, I didn't have exactly the right stuff sitting on the shelf... Used a 150µF cap followed by a 10mH coil; driver measures around 6 Ohms). In case its not clear, the filter is first order. So now with things reined in a bit, I sat down to listen, both with and without the other horns. 

Sound : 

First, I may be totally off here, as I was extrapolating potential from a situation where the horn was about 15 ft out in front of the other horns, so any evaluation in the context of the rest of the system is to be taken lightly. Given that disclaimer, I will say that I was satisfied in a very basic way. This may seem obvious; I sought first to confirm the presence of real mid-bass as compared to what happens when filling in for the absence of this horn as I had been doing, by running the other channels beyond their ideal range (running the 115Hz horns down lower than they should go, while running the lower bass enclosures up higher than they should go... For this session, I did go to the trouble of changing the filters on those channels, moving their operating ranges out of mid-bass territory). Well so do I now have real mid-bass? At this point I can only say that this bass differs in that it is not as constrained sounding, but more weightless and relaxed... Somewhat a contrast to the way the horn looks. Next I would say that despite being way out in front, in the context of the rest of the system, the sound of the additional channel did not call attention to itself; my neighbor however, listening from his apartment, did ask if I hadn't changed something... To me, the system did not seem any louder. Removing the horn from the system (to make space for creation of the second one) turned out to be difficult, and not just because of its mass; given the horn's position, I know how silly this will seem, but momentarily disconnecting the channel had already confirmed that its contribution would be missed; the result was that it stayed there for about a week. I will post more observations once I get the pair of them up and running.

Weight :

One horn without driver, rear chamber or supporting chassis and wheels weighs around 900 lbs. Heavy yes, but not excessive; with music playing at live listening levels, one's hand is enough to detect whether or not the horn is working. The assembly comes apart in quarters split along the horn's firing axis (see clamped flanges in photos above). A single multi-layer lamination (about 1" thick) over the forming tool or buck yields one pair of mirrored quarters, or half a horn. I will post photos of the construction process some time in the future. 

Hang on a minute... I see what may be a sign of progress in the ability to upload images to the cat's server via a Mac navigator... I'll now attempt to post an image of the forming tool (do not hold your breath) :

Well I'll be damned ! Meow !

Above is the forming buck, soon to receive a coat of shelack, followed by several coats of wax.

jd*

Whoa... An "Edit" button! Nice work Romy !

Ok, its a bit screwy (done several edits trying to get the font and colors right and the thing seems to have a mind of its own) but this is real progress.

jessie.dazzle wrote:

Resonant frequency  : I did not try to measure it. Can anyone confirm the following : I assume this parameter is most easily determined by playing a series of tones at constant signal strength (volume setting) while measuring the SPL; the frequency of a tone that gives the highest SPL is the resonant frequency of the assembly. Is this correct?

Well, it is a bit incorrect way to determine resonant frequency as it will be “colored” but other factors.  The easiest way to get the resonant frequency very accurate and very prices of connect resistor of a few Ohm   in series to a mounted driver and to drive the driver with generator, sliding frequency up and down, measuring the highest voltage rise on the resistor. It will be very prices as the peak will be very sharp. Now, it is simple to move resonant frequency up and down but to associate the moving consequences with subjective sonic results is way more complicated as it will greatly depending from the positioning of you horn, filters and many other things.

jessie.dazzle wrote:

Filters :  Initially I ran the horn full range, without the other horns. I was immediately sort of horrified at how high (in frequency) it would play. I then stuck a 5mH coil in front of it, so as to low pass somewhere around 200Hz (really could have used a 3.5mH coil, but didn't have one on hand). Next I made a band pass filter to give a theoretical operating range between 90 and 185 (normally I'd let it go higher, to around 250Hz but again, I didn't have exactly the right stuff sitting on the shelf... Used a 150µF cap followed by a 10mH coil; driver measures around 6 Ohms). In case its not clear, the filter is first order. So now with things reined in a bit, I sat down to listen, both with and without the other horns.

I think you will eventually end up with second order filter, consider the rest of your system. BTW, for this particular midbass channel if you stay with speaker-lever filter you might have inner-debate what to chose – the use of lowest possible series DCR or use air-core coil. Both are great but they are mutually excessive.  I went both ways: had high inductance air-core coils with 8ga wire and have some metal-core low DCR coils. My vote goes for lowest DCR and huge air-core coils with ultra high sensitively spacers is in a way a recipe for various problems.  In my time, when I was experimenting with speaker level filters (before the DSETs), I paid a LOT of money for custom-made low DCR C-Core toroidal Inductors. Nowadays they are available and none expensive:

http://www.parts-express.com/14-gauge-c-core-toroidal-inductors.cfm

jessie.dazzle wrote:

Sound :  First, I may be totally off here, as I was extrapolating potential from a situation where the horn was about 15 ft out in front of the other horns, so any evaluation in the context of the rest of the system is to be taken lightly. Given that disclaimer, I will say that I was satisfied in a very basic way. This may seem obvious; I sought first to confirm the presence of real mid-bass as compared to what happens when filling in for the absence of this horn as I had been doing, by running the other channels beyond their ideal range (running the 115Hz horns down lower than they should go, while running the lower bass enclosures up higher than they should go... For this session, I did go to the trouble of changing the filters on those channels, moving their operating ranges out of mid-bass territory). Well so do I now have real mid-bass? At this point I can only say that this bass differs in that it is not as constrained sounding, but more weightless and relaxed... Somewhat a contrast to the way the horn looks. Next I would say that despite being way out in front, in the context of the rest of the system, the sound of the additional channel did not call attention to itself; my neighbor however, listening from his apartment, did ask if I hadn't changed something... To me, the system did not seem any louder. Removing the horn from the system (to make space for creation of the second one) turned out to be difficult, and not just because of its mass; given the horn's position, I know how silly this will seem, but momentarily disconnecting the channel had already confirmed that its contribution would be missed; the result was that it stayed there for about a week. I will post more observations once I get the pair of them up and running.

You might want to get yours a test crossover to found a good configuration between midbass upper knee and upperbass lower knee. I might be complicated each time take the turns from coils or to solder caps. You might rent in your local pro shop for a weekend some kind of digital crossover or but it for 100 used.  You will not get good sound from it but you will have a good modeling tool. With some experience you will be able to prototype the results. It might be a bit tricky as low-path at line level and low-path at speaker level always sound and act slightly different, so it needed some time to learn and use to the difference. Still, the test crossover is a good tool to see if you move to the right direction…

jessie.dazzle wrote:

Weight : One horn without driver, rear chamber or supporting chassis and wheels weighs around 900 lbs. Heavy yes, but not excessive; with music playing at live listening levels, one's hand is enough to detect whether or not the horn is working. The assembly comes apart in quarters split along the horn's firing axis (see clamped flanges in photos above). A single multi-layer lamination (about 1" thick) over the forming tool or buck yields one pair of mirrored quarters, or half a horn. I will post photos of the construction process some time in the future.

"... I am interested in knowing the material that you made these out of... I've read you mention doing patents, so if "mum's the word," I can certainly respect that..."

No problem... If ever I were to make horns for sale to others, I would definitely not make them the way I've made these or my other horns. The processes used here are fine for making one set, or a functioning prototype. Doing it this way as a commercial venture would require that one use 3rd world labor, and even then, I would still use other processes.

The product used for the 40Hz horn is made in Germany; it is marketed in France under the name "Plasticrete". There is surprisingly little information out there on this stuff. I've done internet research for the equivalent in the US, but came up with zero. It was once used in, among other places, the auto industry, to make quick molds of clay prototype models. There are people in Detroit who must know where to get it.

It consists of a liquid used to laminate fibers. 

The fibers are soaked in an acrylic liquid (looks sort of like thinned out wood glue), mixed with an acrylic powder (looks like plaster). The ratio is 1 part liquid to 2 parts powder (a drill with a mixing attachment is about the only way to get it properly mixed). The resulting liquid is of a similar viscosity and appearance to the batter used to make crepes over here. The soaked fibers are then placed on the forming tool and left for 3 hours, after which point the lamination is fully cured; hard but not brittle.

I would guess that about half of Las Vegas is made of this stuff, so there must be an equivalent in the US. Over here it is expensive. One mid-bass horn costs me 2000€ in materials (just the bare horn, without driver, chassis, rear chamber, etc).

Above : On the shelves are most of the materials that go into one 40Hz horn. On the top shelf is a roll of very thick chopped strand fiberglass mat, which was developed specifically for this process (one horn takes more than just this one 60m roll)... When rolled up, the fibers are compressed, when unrolled they expand and soak up a LOT of the liquid. The resulting lamination is extremely heavy. One advantage of the product is an absence of shrinkage.

Some may be wondering how I know that one horn weighs around 900 lbs... I know this because I pay for the materials by weight, and I waste almost nothing. Yes that shelving unit is overloaded; the wheels are flat-spotted and will not roll. The whole thing just started swaying why I tried.

To the left of the shelf is a large sewer pipe that will serve to make the adjustable rear chambers (see upper-bass horn a couple pages back).

"... Is there something I should know before I cast my upperbass horns?..."

I assume you mean with regard to matarials (?). From what material will you make them?

"...Aesthetics wise, it looks like you were the designer of the Ariel Atom or Deronda or Caparo T1..."

Well... It would be "off-thread" to go into that; I already feel guilt for having posted photos of my cats!

jd*

"... Is there something I should know before I cast my upperbass horns?..."

I assume you mean with regard to matarials (?). From what material will you make them?

Thanks for replying...I'll email you as not to clutter the thread.

jessie.dazzle wrote:

1) Set horns to fire all in same direction (will require some modification to the house) 2) Move to a new house

jessie.dazzle wrote:

So it sounds like you're considering a move...

Yep, I am contemplating this now…

jessie.dazzle wrote:

Criteria : 1) Main room minimum 80m2 with correct length-to-width ratio 2) No mid-room obstructions (no poles, columns, or other supports) 3) Absence of street noise 3) Ground floor That's all I dared ask for.

Yes, I have in way similar criteria. 1 sq meter = 10.8 sq feet, so you are talking about approximately 900-1000 sq feet.  Of a single room. That is pretty much the dimension that I am looking for. A minor thing that the rooms (lofts) of this size frequently comes in Boston with 43-50 foot ceilings.  This might be a bitch as it is extremely difficult to make such rooms to work well. You need a lot of power and anal or of exertion to feel such a volume with bass and we are vey beyond the SET capacity to do this. I would rather prefer to have moderate 15 foot ceilings.

jessie.dazzle wrote:

I spent 4 or 5 months trying to find such a place, but in Paris, large spaces are often divided up into small spaces in the interest of maximizing financial gain.

Yes, the same is in Boston but I am considering buying not renting so I perfectly intend to tear down the walls… I hate the compartmentalized rooms and dummy corridors as well.
 

jessie.dazzle wrote:

I can position the large horns (which are in fact 40Hz horns) only if willing to accept toeing them in way more than I'd like.

Well, I was conserving to leave a part of the 40Hz horn outside of the walls… anyhow, the subject of real-estate and the bass horn is kind of funny and I think it very well might deserve own dedicated thread.

jessie.dazzle wrote:

I look at this audio thing as something that takes time, and I'm OK with that as long as I don't go wasting any of it. It has taken time, but I feel I've moved relatively efficiently; in any case, this is not a passing interest, and as such, its impossible to over-invest. I do however need to get the project done while there's still time left in life to sit down and properly use it!

Well, you do not need to tell me about it. Anyhow, what I see is that my audio demands for real-estate are WAY more ugly them my out of audio demands for home. The last thing would be looking proportion with reverberation time tester and specter analyzer.  Unfortunately with my consulting occupation I need to be in specific area…. That adds insult to injury….

jessie.dazzle wrote:

Also, I'm convinced that a too-big space is horrible for audio as well as being non-conducive to good mental concentration (some of the best ideas are born on the toilet!)

The subject of playback in very large rooms is a separate subject and to get a proper sound in there it requires very different technique then we are familiar in high-end audio. I tend to agree that in I do not like very big rooms but I never have seen a right attempts to properly sound re-enforce a very large closed listening space.
 

jessie.dazzle wrote:

Those Boston lofts may require lowering the ceiling/adding a second level. Quite easy to do if you keep with an "industrial" theme.

Actually it not a bad idea at all….. I never thought about it, I probably shall…

jessie.dazzle wrote:

I have almost no "normal living requirements"... Give me a non-preformatted space and somewhere to fire up the barbeque and I'll be just fine. Ideally, ….

I do have "normal living requirements" but they are very integrated with my audio habits.  I like when my audio is sitting in the middle of room where I live, I like to take my t-short from washer machine and hang it to dry on my horn overnight, I like when my Cat warms up her ass atop on my amplifiers, I like when women are hissing when I pay more attention for cleaning of my records then to compliment their make up or their hair color change, I in a way like when women get very angry because I remember Rachmaninoff birthday but “forget” my anniversary with them, I like do not go somewhere when I would like to hear what I would like to hear…. Well, lately those anniversary become shorter and shorter, I wonder why…  :-)