RF at Ona wrote:

When two loudspeaker drivers are placed close together they become acoustically coupled and so more efficient than when spaced well apart. On in-phase signals, two closely placed drivers would play louder in the bandwidth where they are acoustically coupled but have significant destructive interference for out-of-phase signals. I think this might well apply to the mid-bass horns.

RF at Ona wrote:

In addition to these effects, on in-phase signals the pair of midbass horns might also function something like a two-sector horn where the combined mouth area determines the low frequency cut-off. The low frequency cutoff would be lower for the two horns running in-phase signals than for a single horn.

RF at Ona wrote:

Now the same issues and analysis applies to your woofer towers and with the new placement of the towers some of these effects may have become exposed. If these effects are significant than your new wider spaced ULF towers might actually be functioning more effectively in their upper range than the midbass horns in their lower range on stereo recordings with phase differences between the channels in this frequency range.

RF at Ona wrote:

Because of the low-pass roll-off on the ULF you may have found that a significantly elevated gain for the ULF is improving the music reproduction where the mid-bass horns have unwanted cancellation effects.

RF at Ona wrote:

But this elevated gain does not hurt the reproduction of the ambient/environmental sounds intended to be reproduced by the ULF towers because these sounds are much less sensitive to output level than the musical signal.

RF at Ona wrote:

How significant these effects are in practice are less clear. Stereo phono records usually become quite monaural in the low frequency range to facilitate both cutting the master and playback tracking. CDs and other modern digital sources may have enough out-of-phase bass for the coupling/cancellation effects to be noticeable.

Jorge wrote:

However, as soon the LF begin to inflict a listener with own ‘"pulsating room effect" then the volume of LF should be minimized"

oxric wrote:

RF at Ona wrote: Now the same issues and analysis applies to your woofer towers and with the new placement of the towers some of these effects may have become exposed. If these effects are significant than your new wider spaced ULF towers might actually be functioning more effectively in their upper range than the midbass horns in their lower range on stereo recordings with phase differences between the channels in this frequency range. I am not too clear about 'their upper range.' Do you mean that the lower range of the ULF towers are in principle compromised because this is an area where they overlap the upper range of the mid-bass channel and therefore the area where we have in-phase summation and out-of-phase cancellation (across the whole 42-500Hz of the mid-bass channels I would say)?

oxric wrote:

I have a question ..... I understand that the issue is a complex one and should be addressed with more care and paying attention to detail ...

Romy the Cat wrote:

I do feel that a playback sound has to be built first...The way how I trained myself is to disconnect channels. While I was making Macondo, installing it, moving it and experimenting with it I was frequently disconnecting channels and was listening “what was left”. I like to think about sound as additions and subtractions. The caT

Romy the Cat wrote:

Anyhow, if you ask about strategy to implement ULF then it is an interesting question...What I have now is more advanced but take a look at the cost and the efforts... The most interesting subject however is to go for bass and ULF or to have an integrated bass The caT

Romy the Cat wrote:

I did not have frustration with the bass then and if I did not move I would gladly use that integrated bass as my old room did not need and would not handle ULF. So, ULF and the specific ULF topology is not something that required by Sound but rather is something that is demeaned by listed and permitted by room. Therefore any generalizations is very hard to do. The caT

oxric wrote:

In my mind, and given my specific circumstances, the question of strategy is inextricably tied to the resources in terms of time, efforts and funds that I will be able to devote to this attempt to achieve what I have in mind and what for me will be my one and last playback. Just as you navigated to your present system having at least some elements which heightened the chances of success, I would like to at least initially attempt a solution with an increased chance of success.

oxric wrote:

I am torn between using Scanspeak (or McCauley/Maelstrom in that configuration), which means I need to not worry about midbass or try to go for something as unobtrusive as tapped horns in the room corners and have time aligned midbass along the left and right walls.

And I hope that you do not expect me or anybody else to answer this question? Do you need my or anybody advise about about marriage, investment and etc… Be advised that there are VERY few people who would try all 3 direction you sketched. Usually people try one direction and then work with it in order to have whatever they chose to work. Again, it all would be greatly depending from your room. Remember, bass is sound. ULF impact mostly reverberation time then actual sound. ULF will not work in small room as the room will give own gain in ULF region, this gain will have very short decay time however.

oxric wrote:

So let me rephrase my question Romy, if that was the choice that faced you, what would you do?

Move in new room, put in there any speakers, then encased bass in the room and observe what the room can handle. Then would make a judgment what topology of bass would better highlight best part of the properties and hide the bad properties.

oxric wrote:

Romy, I thought you always had ULF, even in your old room, just not the superior dynamics and I imagine voicing that you now have with the midbass horns, not to mention the increased ability to fine-tune the different bass channels.

Nope, I never had them. I had mono ULF for very short period of time 9-10 year back as an experiment only but it never was a part of Macondo before, nor was it necessary in my old room.

Rakesh,
Thank you for your kind remarks. I appreciate the close scrutiny you have given my previous post but I think you are at a stage of system design where many basics of your system should be considered and evaluated before the issues of my post need be considered - if ever. My remarks were more in the nature of optimizing a well-developed system and discovering how that system interacts with itself than with a fundamental design critique.

However, I would like to offer some thoughts that are relevant to the issues you’ve raised.

ONE BASS HORN OR TWO
Several of your questions essentially revolve around a basic issue to your system design – if you have space for (mid)bass horns should you try for a single horn with a larger mouth and lower cutoff frequency or two smaller horns running in stereo.

This was a question I was going to pose to Romy in the design phase of his midbass horns. He originally considered using the horns into a range much higher than he does now and where both stereo imaging and localization effects might be less acceptable. He rather quickly found the strengths of his midbass horns were in a lower range.

If you end up with a pair of bass horns next to each other it may not matter too much whether you design for two or a single horn as you might get the positive effects of a single horn but you may also get unwanted cancellation of out-of phase bass signals. Summing the bass signals electrically does no good – it merely electrically cancels the out-of phase signals instead of acoustically canceling them. Fortunately, as I mentioned in my earlier post, we are somewhat protected against out-of-phase deep bass signals by a variety of recording practices over the years. So closely placed bass horns might not be so bad.

Furthermore, I am not on the strongest theoretical ground here as I am not sure if the separation of the horns should be considered the separation of their acoustical centers (normally true) or their perimeter closeness (relevant for some analytical approaches). In analyzing woofer drivers the size of the driver is very small compared to bass wavelengths but for the large mouth of the bass horns this distinction may be important. The only practical experience I have had of speakers this size is of large panel speakers. When panel speakers are placed together the effect of the larger baffle size and reduced dipole cancellation effects were of prime importance. So I would need to listen to knowledgeable people with practical experience of large horns or be prepared to research the issue myself.

It comes down to a choice between extending the sound quality that you value in horns or attempting to preserve the stereo signal in a frequency range (below 100hz) with limited stereo information both as recorded and as perceived. Of course, there are alternative approaches.

PRESERVING STEREO WITH A MONO BASS HORN
There is a technique for fully reproducing stereo while using a low frequency mono speaker along with a regular stereo pair. This technique can be used with a subwoofer or a midbass speaker where the prime signal is carried by the mono speaker and the more limited stereo information is reproduced by the stereo pair.

It uses both the sum and the difference of the left and right signals.

SUMMING BASS SIGNALS:
Be careful here. As I mentioned above, if you only sum the bass channels you will cancel the out-of-phase signals electrically before they reach the loudspeaker. That is really not what you want. You want to preserve the stereo out-of-phase information so that it reaches the listener and propagates throughout the room to create the reflection/reverberation pattern you have designed or accepted in the room. If you ever pushed the mono button on a pre-amp or receiver and noticed that the bass went flat you have an example of the problem with a simple summing. I have sometimes preferred using just one channel or the other instead of summing to mono.

THE SUM/DIFFERENCE TECHNIQUE
Create both a sum and a difference signal from the original left and right signals:
Sum = Left + Right = (L+R)    (mono)
Difference = Left - Right = (L-R)    (stereo info)

A central woofer or bass horn carries the monaural sum signal which is the principal component in the bass.

The stereo speakers carry the difference signals which acoustically combine with the sum signal from the mono horn to recreate the stereo left/right signal at the listener.

Mono Horn + Left speaker  = (L+R) + (L-R) = 2L  (i.e. the true left channel signal)
Mono Horn + Right speaker = (L+R) – (L-R)  = 2R  (true right channel signal)
(Note the change of polarity on the right channel difference signal)

Consider how this could be used in Romy’s system,

His midbass horns would both carry the identical sum (L+R) signal so a single horn could have been used instead.

Romy’s bass towers in the new spaced, time-aligned positions would carry not only the ULF but also the stereo signals (L-R) to complement the monaural midbass horn, which should acoustically sum at the listener to the original stereo signals.

By the way, this is an old technique. Alan Blumlein used a variant in one part of his original patent on stereo. He used specially wound transformers to create the sum/difference signals. Today we use op-amps or circuits with differential stages like a Darlington (long-tailed) pair.

FINAL THOUGHT ON AMBIENCE
You wondered about trying to reproduce ambience/environmental sounds at an elevated level. I agree completely with you that sounds like applause, reverberation and general room noise which are part of the recorded sound in the audible bandwidth should be reproduced at the same level as the music. I don’t know how to do it otherwise without creating ambience effects artificially.

I interpret Romy’s findings to relate only to SUBAUDIBLE sounds – sound which lies below our general low frequency hearing. These subaudible sounds need to be quite loud to be even be classified as above the threshold of hearing. I suspect Romy is finding a range of loudness for these sounds which is barely at or below literal hearing but can be perceived or felt. I am not sure if he is compensating for low frequency roll-off in the recording or discovering a way of enhancing the sense of space or acoustic volume with a perceptional trick of hyper-elevating the subaudible sounds. He seems to be convinced that this technique enhances the music reproduction even beyond the sense of acoustic space. I have experienced the beneficial effects of deep bass reproduction and as Romy and others have indicated even without music the awareness of the acoustical space is enhanced. These experiences involved reproduction of the subaudible signal at the same level as the audible bandwidth so Romy’s technique of hyper-elevating the subaudible is new to me.

Regards,
Robert

I am trying to keep the discussion about midbass horns out of ULF thread, I guess if Rakesh would like he can create a separate thread dedicated to his specific installation and the design ideas. I would like to keep the content of the posts more or less related to the subject of the thread.

Very briefly. I never had doubts one midbass horn or two. Sure the proximity of the horns is liability and I well know how they need to be position to be “proper”. There we have the real word of making the horns that would not destroy living hood and become invisible in room. This is where I feel any estimates and predictions fails- you build what you want to build and then deal with consequences. The monophonic position of my midbass horn doe has own toll but it is imposable to share what is right and what is wrong- all negatives and positive very much mixed together in one presentation. Also, the system is very much optimized to play with this type midbass horns the upperbass horns made do not work linearly but they a bit overshoot.  The result is that upperbass horns take over the attention from midbass horns and listening the installation without ULF you clearly hear the midbass notes as they are coming from front-located upperbass horns. It is very-very nice and in a way unbelievable. Even without using the ULF the location of midbass horns appears to be not identifiable. Dose the midbass horns semi-mono location has an impact to the “width” of playback. Yes it dose and I did clerlay expressed it in posts what I played with idea of width modulation channels. However, the width channel that I described was not because the midbass horn but because some upper MF cancelations, the cancelations that ULF has fixed. Still, the midbass horns are where they are and they are where I would like them to be. In my view there is no need in prediction of sonic results and to use those predictions as stimulation or contra-encouragement for building the horns itself. A midbass horn is like a child – it is perfectly possible that you son will become a serial killer. Still, it is not what you think when you consider to have a child. You conceive the concept and then do your best in order you son do not become a serial killer. The very same with such a large architectural project as midbass horn – it will be the result of your steering to the most part.

Now back to the ULF topic. I was thinking about use of R and L delta (I have the sum and stereo delta in my R&S multiplex decoder) but very fast discard this idea. To use phase injection means to interact with the original signal. It does have benefits but it also degrades “direct” sound as well. How to assess what kind injection is beneficial and what kind sound deterioration is still acceptable? I am staging on position that if the main signal is compromised in ANY way then whenever is being done is not usable.  The Macondo capacity is very high and it is very “clean” of you know what I mean. You hear pretty much what you hear with good headphones only much more in terms of tone, space and imaging. For instance I have Dorrough modulation meter that has 2meg input impedance. You understand that adding 2mR cable to 16R speaks has to have absolutely no impact. In fact I use in on my MF channel and I see no difference. However, to use the same meter on midbass channel does affect sound very negatively. Now, to add to my system another devise with 2-3 active stages that would do phase prosing I feel will be too damaging and I would like to keep the path as sort and non-compromised as possible. Do not forget the a few years back I was not able to make a 0 gain buffers that would be transparent enough.

I do feel that what Robert propose might be experimented and use but NOT at the design stage. The design concepts need to relay upon dealing with straight signals. Then, after the straight operating playback is set, then one can see what else might be done and how different intentional additions work against the non-compromised signals.

In the end - a comment about “reproduction of the subaudible signal at the same level as the audible bandwidth”. It is not necessarily what it is.  There is no same level, hyper-elevating level or elevated level. When we hear live sound then we have no “level of space” and we subconsciously get the messages about “space” from naturally-long reverberation time, from visual aspect and from another sensors.  Recordings does not have this information, the listening rooms has near close decay time is necessary (The Symphony Hall in Boston has drop at 60dB for 1.5 seconds), not to mention that ULF information is severely distorted on recording. So, the idea is do not correlate the ULF messages with auditable signal but to separate them and to run ULF at the level that creates SIMILAR sensation as it happens during live event. The keys in it to have ULF do not affect the audible signals, to have a feasibility of ULF level, to have front of ULF time-aligned, to have the ULF leading edge as compressed and sharp as possible, to have a room that will be able to dissipate the ULF decay evenly. So, it is not about levels in terms of dB equalization but rather about of equity of perception.  I do not even know what the objective level of my ULF. My ULF is higher than it would be with a linear single driver that would 20Hz-20kHz bandwidth but who said that linearity is a part Reality? I so not even mention that in audio we do not deal with  Reality but we deal with very barbaric ways to mimic Reality…

RF at Ona wrote:

By the way, this is an old technique. Alan Blumlein used a variant in one part of his original patent on stereo. He used specially wound transformers to create the sum/difference signals. Today we use op-amps or circuits with differential stages like a Darlington (long-tailed) pair.

RF at Ona wrote:

...I have experienced the beneficial effects of deep bass reproduction and as Romy and others have indicated even without music the awareness of the acoustical space is enhanced. These experiences involved reproduction of the subaudible signal at the same level as the audible bandwidth so Romy’s technique of hyper-elevating the subaudible is new to me.

Romy the Cat wrote:

Dose the midbass horns semi-mono location has an impact to the “width” of playback. Yes it dose and I did clerlay expressed it in posts what I played with idea of width modulation channels.

Romy the Cat wrote:

I do feel that what Robert propose might be experimented and use but NOT at the design stage. The design concepts need to relay upon dealing with straight signals. Then, after the straight operating playback is set, then one can see what else might be done and how different intentional additions work against the non-compromised signals.

Romy the Cat wrote:

In the end - a comment about “reproduction of the subaudible signal at the same level as the audible bandwidth”. It is not necessarily what it is.  There is no same level, hyper-elevating level or elevated level. When we hear live sound then we have no “level of space” and we subconsciously get the messages about “space” from naturally-long reverberation time, from visual aspect and from another sensors.  Recordings does not have this information, the listening rooms has near close decay time is necessary (The Symphony Hall in Boston has drop at 60dB for 1.5 seconds), not to mention that ULF information is severely distorted on recording. So, the idea is do not correlate the ULF messages with auditable signal but to separate them and to run ULF at the level that creates SIMILAR sensation as it happens during live event. The keys in it to have ULF do not affect the audible signals, to have a feasibility of ULF level, to have front of ULF time-aligned, to have the ULF leading edge as compressed and sharp as possible, to have a room that will be able to dissipate the ULF decay evenly. So, it is not about levels in terms of dB equalization but rather about of equity of perception.  I do not even know what the objective level of my ULF. My ULF is higher than it would be with a linear single driver that would 20Hz-20kHz bandwidth but who said that linearity is a part Reality? I so not even mention that in audio we do not deal with  Reality but we deal with very barbaric ways to mimic Reality…

Romy the Cat wrote:

I am trying to keep the discussion about midbass horns out of ULF thread, I guess if Rakesh would like he can create a separate thread dedicated to his specific installation and the design ideas. I would like to keep the content of the posts more or less related to the subject of the thread.

There is site out dedicated it infinite baffles subwoofers. I am not sure how serious they are as they use mostly metal in rubber drivers as got thrilled when “Apollo 13 takeoff, my doors move back and forth 1/2", and the  frequency is below 5 hz”. Taken from here:

http://ibsubwoofers.proboards.com/index.cgi?board=general&action=display&thread=8

Still they have a few threes about Rotary ULF idea

http://video.google.ca/videoplay?docid=-7885139890934147401

What particularly interests me was that somebody told:

“Note that there have been other 'rotary' drivers (Tom Danley created one). Bruce's is the first to work in this maner (varying the pitch of rotating group of blades according to frequency) .”

http://ibsubwoofers.proboards.com/index.cgi?board=stuff&action=display&thread=656

I did not know that Danley has a product in ULF world.

I do don’t know if I have an interest in Rotary driver to use in my playback but I am for sure would like to experiment with one. The problem is that this thing might need to have infinite baffle configuration and my house do not have the firmness to handle it.

I have a bass devil-machine with wish I tested the construction of my house. I am taking about Sunfire cube subwoofer that I have. Sonically it is worthless thing but it cap pump insigne amount of LF pressure into the room and to let observe how the room deals with it. If I deal with something like Rotary ULF idea then I would need to do some structural modification in my room – something that I do not look forward to do. Still, if somebody know an example of sensible people with non-barbaric demands and reference in sound who have implemented the Rotary ULF idea then it might be interesting to hear from them.

Awhile back I had a conversation via email with Tom Danley concerning the Phoenix Gold Cyclone that he developed for Phoenix Gold and the car audio market. They were not well built by Phoenix Gold with some crucial parts made of plastic (although he spec'd aluminum in his prototype) and were not able to withstand the forces for long. They eventually started to rub making them useless. He did have a larger prototype that he had hoped to eventually come back to market with but I have not heard of it being realized. 

In a particular experiment with these smaller cyclone rotary woofer he was able to have response flat to 10hz with it being vented to a crawlspace. That was just one rotary woofer. It had a fs around 10hz.  It also had no power compression as the wire part (wound on the stationary
laminations) takes 30 min to heat up instead of 5 or 10 seconds or so for a voice coil.

It would be interesting to find out if the larger ones he prototyped will eventually be built but I think his tapped horn ULF boxes worked out so well for him that it might have sidetracked him.

In context of my resent observation and my desire to get more softness from my lower bass:

 http://www.GoodSoundClub.com/TreeItem.aspx?PostID=15814

I spoke last night with a friend of mind who pitched me very interesting idea. I told him that although I do have very good low bass but I do register some alien event. I gave him an example of drifting in sea on your back during a nigh and no moon, no stats, no shore signs and no light of any kind. You are laying on you back and you feel no gravity with water of the temperature of your body. The water is still and you are content. Than two single waves come, let say 5 feet tall. One way come under you, lifted you up but sine you have no references of you weight and the position of your body then you do not feel that waves and it pass not registered by your senses. The second wave pass and you feel that what you at the very crest then you got a glimpse of the shore light. I mean that was some other event in your being while you body experienced the waves. The first wave reflects how my midbass horn sound. The second wave reflects how my ULF sound. Again the difference is very minute and I do not think will be notice by the most but I am not a common observer….

When I described the situation to a friend of my last night he advised that it very much might be due to the fact the my SS amp has much faster rise time then my DSETs and therefore the leading edge of my ULF wave is steeper then with the rest of my sound. We contemplated a few ides how it might be address but I come to an observation that I do not want to loops that sharpness of bass attack. Then the friend of mine proposed that it might be about the time alignment, again!

You see my ULF are time aligned with my midbass and the rest of the playback, so what he proposed is to move my ULF towers for a few inched back and forth in order to smear the very leading edge time aliment and by doing it to create a virtual equalization of rise time between my SS amp and Melquiades. I think that idea is very elegant and I very much look forward to try it. You need to understand that we are taking about moving a bass tower that is crossed at 25Hz with 3rd order for a few inches, or perhaps towing it in or out. Under normal circumstance if you move the tower for inch of two you shall not be notice any differents. However since now I know what exactly to listen then it might be very much that the different and the purpose of this experiment does exist. In fact I might predict that I will be able to moderate the ULF softness by doing what is proposed above what I do not know if adding the “softness” to ULF I will make my midbass to lose it’s edge – something that absolutely not willing to compromise.

Anyhow, it will be an interesting experiment.  If the smearing the ULF attach will help then, sine I have no 200W DSET amp I might introduce a 1:1 transformer after the SS amp, or use the SS specialist to decrease the amp rise time to equalize what my bass Milq does. If someone heard anybody who experimented with bass SS amps to behave as tube bass amps then let me know. It would be good if the issues I described to be cure by amplification and ULF location. It might be much more painful if it came from my ULF channel itself. I do not think that it is the case but it might…. Will see…

Romy,
I might have overlooked something on your site but I understand that your ULF amp is driven directly by the preamp line stage. If that is the case, you may want to consider an old technique for integrating subwoofers and drive your ULF amp with the attenuated output of the midbass amp. Perhaps this is an idea you considered and discarded but sometimes it helps to state the obvious.

Frequently with a deep bass speaker we want to bypass the low frequency limitations of the main amp and drive a separate bass amp directly from the pre-amp. But in your case, the midbass SET amp is optimized for the low bass so using it to drive the ULF solid-state amp might help restore some tonal system integration.

This technique should also help to improve the phase alignment of the ULF and midbass speakers since the ULF would see the phase variation of the midbass low-pass crossover and any phase variation from the SET amp/transformer. You may need to adjust the ULF/midbass crossover afterwards and pay attention to any phase inversion of the amps.

I hope people reading about your progress appreciate that a highly refined integration of your ULF and midbass sections is not a straightforward exercise. The midbass uses a transformer coupled tube amp, the ULF a direct coupled solid-state amp. The midbass is horn loaded, the ULF a direct radiator. They are positioned on opposite sides of the listener and their traveling waves moving in opposite directions. The pass bands are narrow allowing the primary high-pass phase/amplitude responses of the loudspeakers to mix with the responses of the crossover filters in unintended ways. Even if the ULF output is not supposed to overlap the midbass output I suspect it does so in practice - and of course the ULF distortion spectrum and resonances surely factor in the midbass if they are audible at all. And as I mentioned in an earlier post, there may be unwanted crosstalk effects between left and right channels because of close placement of the midbass horns. Be happy the results have been so pleasing and the only need is fine-tuning. Even from afar I have found this a provocative technical challenge.

---Robert

P.S.:  If you are going to reposition your ULF towers you might consider facing them away from the listener seat in an effort to reduce by redirection any higher frequency distortion or resonances that may have some (small) beaming to the front. The frequencies you want the towers to reproduce are very omnidirectional so there may be just a slight benefit to turning the towers around fully or even somewhat from the listener.

RF at Ona wrote:

Romy, I might have overlooked something on your site but I understand that your ULF amp is driven directly by the preamp line stage. If that is the case, you may want to consider an old technique for integrating subwoofers and drive your ULF amp with the attenuated output of the midbass amp. Perhaps this is an idea you considered and discarded but sometimes it helps to state the obvious. Frequently with a deep bass speaker we want to bypass the low frequency limitations of the main amp and drive a separate bass amp directly from the pre-amp. But in your case, the midbass SET amp is optimized for the low bass so using it to drive the ULF solid-state amp might help restore some tonal system integration. This technique should also help to improve the phase alignment of the ULF and midbass speakers since the ULF would see the phase variation of the midbass low-pass crossover and any phase variation from the SET amp/transformer. You may need to adjust the ULF/midbass crossover afterwards and pay attention to any phase inversion of the amps.

Hm, interesting. I did not even think about the option to drive ULF from out of the midbass amp, partially because my midbass channel is high-passed by Milq’s inner-stage capacitor at 20Hz. I tend to unload unused bass from the midbass horn in order to prevent the unnecessary excursion of the driver that do not lead to bass able to go out of mouth. I know, it is not what people do – people load as much bass to midbass horns trying to get “more”. A horn is a delicate devise and if not blow into a horn more than it might handle then it handles what it can handle with more grace.

I am not sure that the minor problems I observe are in the realm of “restore some tonal system integration”. You see, the ULF does not output anything that resembles tone. The third order at 25Hz is not “sounds” but rather some LF bumps on the road. So, I might be mistaken but I do not think that I deal with tone but rather with shaping the sharpness of the bumps.

If I use midbass with no highpass then considering that I have monster LF out transformer in there I might be a good idea to have some kind powerful current SS buffer and to drive ULF from there. It is not how my playback organized however. In my playback the midbass channel drives midbass horn with line level, inner-state level and speaker level filter. The ULF power amp source signals from preamp via a line level filter of third order. Since the current at line level is relatively low and the shunting capacitance in my RCRCRC 25Hz low-pass filter before ULF amps is relatively high the ULF filter is “slow” itself. This slowness of ULF file compensates the advantage of the super fast rise time that my ULF power amp has over my tube Melquiades. My ULF power ams is Yamaha B2, that is full DC amp with no capacitance in signal and high current. Those amps have very fast rise time and if I use it directly then I would probably shunt the am with come capacitance to keep it in rise time in the same par as my Milq has. The harmonic difference between my SS ULF amp and Milq is totally different subject however but I hope that at sub 25Hz the harmonic differences might be not so prominent… I hope….

Actually the idea that I feel very enthusiastic is to use the same type of 1:1 output transformer that I use for my midbass but only the SS amps and my ULF section, I mean literally to bring the high current SS output signal to the transformer code. Do not forget that at sub 25Hz all coupling is coming via core. Furthermore, since the amp is DC amp (the preamp is also DC preamp) I might put some gap into the 1:1 transformer to deal with DC. I am not sure that the problems I hear are not DC related. I have drove my bass with DC amplification. Before Milq I drive my bass with a dedicated Lamm ML2 what was a SET with output transformer…  So, I am very interested to try the transformer approach but I am just too cheap to commission people to have those transformers to made just for sake of experiment. If I have borrow such a transformer and make experiments without paying around $1K then it would be more sensible solution. Does anybody have a 350H-400H, 250W-300W, 1.25:1 transformer with 100-150mH gap that I can borrow for a week or two? Preferable for me do not pay $1000 for the shipping of that thing…

RF at Ona wrote:

I hope people reading about your progress appreciate that a highly refined integration of your ULF and midbass sections is not a straightforward exercise. The midbass uses a transformer coupled tube amp, the ULF a direct coupled solid-state amp. The midbass is horn loaded, the ULF a direct radiator. They are positioned on opposite sides of the listener and their traveling waves moving in opposite directions. The pass bands are narrow allowing the primary high-pass phase/amplitude responses of the loudspeakers to mix with the responses of the crossover filters in unintended ways. Even if the ULF output is not supposed to overlap the midbass output I suspect it does so in practice - and of course the ULF distortion spectrum and resonances surely factor in the midbass if they are audible at all. And as I mentioned in an earlier post, there may be unwanted crosstalk effects between left and right channels because of close placement of the midbass horns. Be happy the results have been so pleasing and the only need is fine-tuning. Even from afar I have found this a provocative technical challenge.

Yes, what you describe is sound like what it is it but in reality it is not, well, not all of it. The “behind” positioning of midbass horn, the biggest problem that I was afraid is turned out to be not a problem at all. The key with operating of this horn was to find a VERY precise balance between the out of midbass and upperbass. I have locked it with less than ¼ db precession (ask me how and you will be laughing) and believe me or not it stop to be a subject of my concern. Even without running ULF the midbass does not call to itself, it’s location and it’s output are very fine in my estimation and I have no needs to do anytime with it. The incorporation of ULF of different topology and driver by different amp is of cause a task but frankly as I dumped my ULF channels where they are now then I got right the way a VERY serious integrated bass. BTW, it is not a reference of any kind for me but since then I had a few of audio people in my room and no one reported any dissatisfaction with bass integration. So, with all complexity of my playback it is happens that it is not so complex to manage the things. still, in contrary to the people who visited me I do feel that there is “something” in my ULF that is not the way how I would like it to be. it is very minor and it is more like harmonic or dynamic differences but I do not think that it is harmonic or dynamic. I still am trying to figure out what it is….

RF at Ona wrote:

P.S.:  If you are going to reposition your ULF towers you might consider facing them away from the listener seat in an effort to reduce by redirection any higher frequency distortion or resonances that may have some (small) beaming to the front. The frequencies you want the towers to reproduce are very omnidirectional so there may be just a slight benefit to turning the towers around fully or even somewhat from the listener.

I did have some VERY interesting and very surprising results last night while I was moving my ULF but I had very limited time to do it and to think about it. as I will do it again I will report the results.

Last night I spent some time with observing my ULF and I conclude that I am not exactly know what I deal with. Do not get me wrong: the ULF forks fine, sounds fine and the playback is perfectly operational and listenable; it does sound very good right along with ULF integrated. I have no problem to leave it in the very same state as it is now as in my view it is perfectly acceptable result.

However, this fine ULF result is not what I would like to have ULTIMATELY. Ultimately I would like to have much more output at 10-15Hz region but to have nothing extra at 30Hz. I feel that my midbass horn produce very right sound at it very low end. The way how the midbass horn’ lowest notes are dissipating in thin air is fantastic, conforms to the best of my dreams.  They might use more “room” and more “weight” but this sense of “space” and “weight” I feel need to be a bit less generic then what I get. The ULF produces very good room/weight/space trick but it is a bit the same trick type for all music. If to think about then the playback has some kind of coloration at ULF level. Still, shutting down the Melquiades amplifiers and run just ULF channels it is clearly visible that there is no tone coming out of ULF, there is no “sound” out of them that has any tonal characteristics.

As I said, I do not know where this differences minimizing common denominator of ULF coming from. It might be from amplification, might be from the design of my woofer towers, it might me from the exercise level of my ULF output or from other things. It “feels” like my ULF need to be “softer” or to have more “good honk”. I do not know how to do it at this point. Ironically the moving the woofer towers do change the way how the sound. Believe me or not  but the move them for 5-6 inches do change the roundness of the ULF – if to know what to listen then it is auditable. However, this roundness looks like not what I looking. I am looking for a right balance between the speed bump and the stiffness of suspension. I would know what kind feeling I would like to get from that car passing the speed bump but I do not know what kind mechanism I can regulate in order to get this feeling.

My sentiment is that I might need to start from beginning and search for a new crossover point only now with the woofers towers to be positioned where they are now – right next to Macondo in time-aligned position as they use ot be in my old listening room. I keep driving my ULF less and less and not I am at 25dB up compare to what I was at my first day of the woofer towers in the new position. I do have more proper bass weight but I am not getting enough my ULF stimulation at sub-auditable region. I think to have it done properly I would mend two ULF channels – one for infra bass region that is still auditable in midbass and one for 8-15Hz region that has no impact to sounds but rather impact the “miracle” properly of  the room. Sure I will not have two ULF channels but I might experiment with transition sloe of my low filter at my current ULF in order to put one ass on two chairs.

So, the idea is to have more ULF in sun 15Hz region, much more, let say 15dB-20dB more then what I have now. Then to arrive to 25-30 Hz at the same level as I have now, perhaps even 1-2dB more shallow. Do not have any tonal or dymick colorations or any “events” as my midbass are decayed.  That all might be implemented by use of very sharp filter of let say 4-6 order and sliding my ULF down to frequency range at the transition slope. If I put let say 4th order at 10Hz then I might get somewhere but it would give me -48dB at the bottom of midbass horn. To the midbass to “see” my ULF I would need to push a LOT of gains and power into ULF – I just do not have this power in my ULF amplification. Even if I did then I might get just right ULF-LF-midbass balance in my room but it would not say anything about the “character” of bass sound I will get. With pumping 500W-700W into my woofer towers at 10Hz I will be dealing with very different driver reaction and I will be bounded to very limited amplification capacity – in a way will become a slave of it. Interesting the in my current seeming, even while my ULF reproduce sound that I characterize as “colored” the drivers in my woofer towers are practically motionless…

Anyhow, I think I need to rethink that whole thing. I am in a good shape to go for something offensive or as I call objectionable (in my language it means “full of loaded objectives”). What I have is good and it gives me time and room for maneuver for something what would be better than good, let see what it will bring me, at this point I am not sure that know what I deal with.

You know, it surprises me how much less fan to listen my playback without ULF.  Nope, the playback does not sound bad from audio perspective without ULF but it for sure a bit different experience. From a certain perspective to be in a room with ULF on is a different experience as ULF charnel adds some extra softness to the room. The Midbass in fact adds softness to the room but ULF adds to this softness some very fine touch “softness elegance”. The note’s decay dies more gracefully and more acoustically soft of speaking…

I do think that ULF channels has to be a part of any more or less serious playback and I think that  any more or less serious playback shall explode what is going on udder 20Hz. As I said my own ULF is in a bit compromise as it goes too high – up to 27 Hz. What I fix or buy a new power amp for ULF I will try to slide my ULF lower, let say down to 15Hz and add gain, effectively sliding the ULF down in the transition slope. I do not know where would be right balance between my sub 20Hz ULF mishigas and proper balanced auditable sound but I am sure that what I get there then I will be able to recognize it. I do not mind to experiment with ULF equalization as I think it might also bring some interesting benefits.

The whole point is that ULF has become an organic part of my listening environment and now with no ULF power amp even the playback sounds fine but the environment feels underdeveloped. I think more people have to hear the contribution of any more or less properly implemented ULF to understand what I am taking about.

Interesting that industry do produce ULF-targeted devises but they looks like do not meet a wide popularity. Wilson Audio for instance did XS subwoofers. They were unfortunately ported with two Aura 1808 drivers

http://www.soundstage.com/revequip/wilson_xs_sub.htm

…and meant to be use under the Wilson Grand Slamms. You can say anything you want about the Grand Slamm bass, I am not a huge fun of it either but Wilson for sure had a point advocating to use ULF channels to supplement the Grand Slamms bass. You will not see the idiots-reviewers feeling that their Grand Slamms, Alexandrias and the farty Maxxes need any ULF support.   The Morons are just not familiar with the whole ULF subject but by the fact that Wilson made XS modules available it clearly indicate that David Wilson is familiar. The late John Dunlavy before he bailed out from his active involvement in audio did produce set large ULF modules. John told me that his SC-VI speakers that were considered goog bass performers still might be benefited by an addition of ULF channels.

I very much do not use Dunlavy or Wilson as some kind of reference or examples as they have this own sinister reasons to do what they did. Still.  I just merely point out that those options are available out there as much as it might be some other solution that can effectively to work below auditable LF region. I do encourage you if you have opportunity to audition an installation with ULF idea engaged. You might get that ULF bug and will find the no-ULF installations being too plain for your new taste.