Bad setup, bad room, or sensitive ears? Subs are just never from the "same cloth"!

[terryj]

Another question for the experts here: Is it possible to set up a sub-woofer to emulate the quickness, dynamics, and impact of a Wilson Maxx 2 or Maxx 3 bass? Or is Wilson using special woofers? Special crossovers? Something else to make their bass standout and have visceral effects?

short answer, of course, without a shadow of a doubt. See my earlier points...a sub does not have to do much to have the speed.

dynamics?? well, let's just say that a lot do not regard wilson bass as anything special. and they use bog standard everyday passive crossovers, sorted and understood decades ago. bog standard audio drivers.

Impact? Try pro drivers, after all the ones that produce the impact live. Reckon they could not do what you are ascribing to wilson?

there is nothing cutting edge about wilsons apart from marketing.

 

[bwraudio]

coherent bass

Combining Magneplanar Tympani IV bass panels (modified)
with the Eminent Technology rotary woofer is a match that
is both powerful and totally coherent. Consider next reactance, as another example of opposite behavior. Conventional subwoofers have large reactance, plus severe reactance changes, at low frequencies. This reactance comes from the driver's free air resonance, compounded by the resonance of the enclosure volume with this driver, compounded by the resonance of the port or vent (if any). This reactance creates four huge sonic problems, which preclude correct bass reproduction. First, this reactance sets up a barrier fence at a certain frequency, below which the conventional subwoofer cannot go, to reproduce the full bass spectrum. Second, this reactance stores energy and then releases it much later in time (as bass overhang and ringing). This spurious delayed energy release not only creates a phony bass sound (boomy overhang), but also obscures subsequent musical information (of all frequencies) that happens to occur immediately after each bass transient. Third, this reactance robs energy from the initial bass transient (the energy contained in that delayed energy release has to be stolen from somewhere), so the initial attack of bass transients lacks sufficient dynamic impact. Fourth, this reactance grossly corrupts the time domain waveform put out by the conventional subwoofer, so that its contribution to the overall musical transient does not properly add up with and cohere with the waveform put out by the main loudspeaker for this same musical transient.
But again the new TRW subwoofer is just the opposite, of conventional subwoofers. It does not have any reactance at very low frequencies. Thus, the TRW subwoofer does not evince any of these sonic problems that reactance causes in conventional subwoofers. First, the TRW does not have any barrier fence precluding response to very low frequencies, and can happily reproduce the full spectrum at full amplitude all the way down to DC. Second, the TRW does not have any spurious delayed release of energy, so its bass quality is inherently correct and tightly defined, without any phony boom or overhang. And the TRW also thereby allows you to hear much more information immediately after each bass transient (e.g. the woody timbre of a sounding board), so everything from music to special effects sounds much more real. Third, the TRW does not steal any energy from the initial bass transient, so you get the full dynamic impact of each bass transient, again getting you much closer to sonic reality. Fourth, the time domain waveform put out by the TRW is inherently accurate, instead of inherently screwed up, so its waveform correctly adds up with and coheres with each musical (or sound effects) transient put out by your main loudspeaker, to give you for the first time in your life a correct, coherent transient.

No commercially available subwoofer can match this combination; totally awesome.

 

[Steve Williams]

I heard a demo of Bruce's TRW several years ago at the home of one of the members of our audio club. Thigpen and his assistant flew all the way from Florida to set it up. Needless to say it was truly impressive. I recall that Mark Seaton and Keith Yates were also at that demo. Quite a cast of characters. I remember being in the far rear corner during the demo and I had motion sickness for hours after. I was also concerned that increasing the volume on the TRW could loosen the foundation of the house as well as cracking the dry wall and windows.

The demo of the ship battle from Master and Commander was memorable to say the least

 

[sasully]

I never pulled a trigger on subs based on the fact that I always have heard the incoherencies.

If you are hearing 'incoherencies' in a sub/speaker system , a very simple matter to explore before considering 'speed' 'quickness' and dynamics' or suchlike, would be what frequencies it is outputting. If there's a lot of energy at frequencies over 80Hz , then you will be able to 'locate' the sub by ear, which is not desirable.
Careful placement, and setting of overall levels and phase, are important too.

 

[fishnchips]

The reason that most subs cannot "friend" electrostatics is rather straightforward and I wonder why no one has mentioned it. Electrostatics are unique in that their radiating unit is far, far lighter than its own air load. About three orders of magnitude lighter. This means that, if there be any other pressure field (eg from a a sub) moving the air in the listening space, the feather-light electrostatic membrane will helplessly flutter in said sub's mighty breeze. Since almost all subs are unipolar omni radiators and 'stats are bipolars, the two conflict and all sorts of cancellations happen. This is not the case with bipolar subs, the side nulls of which oriented along the same direction as the 'statics' side nulls. In such an arrangement the conflict disappears.

Magnetostatics do not have the same problem because their radiating element, light as it may be in absolute terms, is reasonably heavy as compared to its own airload (this is the crucial parameter).

The issue of the sound quality of the 'stats being free of distortion and box colorations (as opposed to box subs) is a different one entirely; as it is not one of first principles, it is remediable.

 

[RUR]

The reason that most subs cannot "friend" electrostatics is rather straightforward and I wonder why no one has mentioned it. Electrostatics are unique in that their radiating unit is far, far lighter than its own air load. About three orders of magnitude lighter. This means that, if there be any other pressure field (eg from a a sub) moving the air in the listening space, the feather-light electrostatic membrane will helplessly flutter in said sub's mighty breeze..

Hyperbole aside, yes, bass coupling does occur with ESL panels, but this does not affect the panels ability to accurately reproduce the input signal. I discussed this with Roger Sanders via telecon this morning, and he used an elegant analogy: Imagine you're floating in a raft on a rolling sea (the bass wave). You stick your hand out of the raft and slap the water (the waveforms produced by the ESL panel). The resultant ripples are independent of, and unaffected by, the surrounding sea condition. On an empirical level, I can toggle two subs in and out of my system with a keystroke and hear no audible effect (distortion, loss of clarity) on mids/highs, even with the room thoroughly pressurized while listening to the Tron soundtrack @ >90dB.

Since almost all subs are unipolar omni radiators and 'stats are bipolars (sic), the two conflict and all sorts of cancellations happen. This is not the case with bipolar subs, the side nulls of which oriented along the same direction as the 'statics' side nulls. In such an arrangement the conflict disappears.

A very real problem in hybrid ESL's, and manufacturers of such speakers go to great lengths to mitigate this effect at mid-range crossover points (panel to monopole woofer, typically 250-350Hz), with varying degrees of success. I struggle with the concept that monopole sub/ESL mains integration is problematic at typical, omnidirectional subwoofer crossover frequencies, and I've yet to read an adequate explanation of why this is so. Linkwitz, for example, discusses the advantages of dipole subs, but not, that I can find, in the context of sub/mains integration. Perhaps you could help me out here, i.e. what and why are the cancellations and how are they different than dipole sub to dipole mains.

 

[fishnchips]

and hear no audible effect (distortion, loss of clarity) on mids/highs

Right. Air load varies with frequency: wavelength, more appropriately. The smaller the wavelength, the less air couples to the membrane. I cannot dig out the relevant equation right now but, if memory serves me right, from a certain point upwards air load decreases as 1/f^2.

how are they different than dipole sub to dipole mains.

A boxed sub pressurizes the room uniformly, i.e. it produces a positive instant pressure envelope. This is what gives boxed subs their visceral impact. A dipole sub produces equal but opposite amounts of pressurization in front of it and behind it. This explains the dipole subs' lack of visceral impact. The former increases the electrostatic membrane's air load. The latter does not, provided the two units are in phase. This is my simplistic understanding of the situation. Linkwitz does not need to address it because his designs use regular electrodynamic drivers throughout.

 

[RUR]

Right. Air load varies with frequency: wavelength, more appropriately. The smaller the wavelength, the less air couples to the membrane. I cannot dig out the relevant equation right now but, if memory serves me right, from a certain point upwards air load decreases as 1/f^2........The former increases the electrostatic membrane's air load. The latter does not, provided the two units are in phase. This is my simplistic understanding of the situation.

In what frequency band, then, does the monopole sub pressure wave audibly affect the ESL panel’s ability to accurately reproduce musical content? Can you point me to the study or other objective evidence which demonstrates this effect?

 

[repman]

I heard the large Scaena system at Axpona last month and the subs were totally integrated , those babies were singing sweet. One of the best integrations of a sub with a driver array I have heard.

 

[fishnchips]

In what frequency band, then, does the monopole sub pressure wave audibly affect the ESL panel’s ability to accurately reproduce musical content? Can you point me to the study or other objective evidence which demonstrates this effect?

As I said, I write from memory. I guess the relevant formulae can be found in textbooks like Beranek's Acoustics and then appropriate calculations made. There is also a comprehensive chapter on electrostatics by Baxandall in Borwick's handbook. Alas, it's too much work for me to be going over tens of pages of differential equations at this time.

 

[twelti]

If you assume a completely linear system, then I agree with the waves on an ocean analogy. It is simply the principle of superposition. I also wonder how much the sub actually does move the ESL panel in practice. If the sub is truly an omni source and the ESL panel directly above it, the pressure on the back would be the same as in front and no movement. Of course a sub is not a perfect point source, and reality is a bit more complex. If the sub did manage to move the panel enough, I wonder if there could be some nonlinearity (modulation effect) produced?

As for mono summing with dipole response, I think of it as a pressure source and a velocity source (respectively). The way that they couple into the room will be compementary. For any given mode, the pressure source (standard sub) will couple most efficiently to pressure maxima in the room. The velocity source (dipole) will couple most efficiently to the velocity maxima in the room. THe pressure maxima correspond to antinodes (peaks) in the spatial response of the room, and the velocity maxima correspond to nodes (dips) in the spatial resposne of the room. The velocity source is complicated by the fact that it will depend on the orientation of the source in the room. Anyway, that means the way the sub and ESL panel couple to the room (and thus is transfered to the listener) would be guarenteed to be different, since one will be coupling to pressure maxima and one to velocity maxima (mutually exclusive).

This might sound complicated, but in real life it's proably even more complicated! The above is probalby a gross simplification.

 

[FrantzM]

Twelti

I understand it can get real complicated down there but in the end are these diferences in coupling really audible when combining an ESL or other Falt Panel with subwoofers. I was of this opinion until I carefully set up my Magnepan 20.1 with three cone subwoofers.. My system never sounded or measured better in the bass .. Biases of expectations are there .. There are so many myths in the audiophile mindscape .. For many there will never be any way that a "slow" cone could ever keep up with a "fast" or "quick" panel.. This is even more difficult to dispel than we would think .. if on were to mate an ESL with no bass with a good subs system, the added bass could well be described by the ESL-is-faster believer in negative terms ... The bass would be heard .. No way to hide it ... So ...

 

[fishnchips]

For many there will never be any way that a "slow" cone could ever keep up with a "fast" or "quick" panel

"Fastness" or "slowness" can be measured. One may anthropomorphically equate light with fast and heavy with slow, but the fact of the matter remains that Sebastian Vettel's heavy monocoque will always be faster than a toddler's light plastic tricycle - even if one switches drivers. There is more to acceleration than mass, and a certain Sir Isaac wrote about it several centuries ago. In the case of "slow cones", the limiting factor in acceleration is, more often than not, a low-pass crossover.

 

[mjaudio]

The quality of a subwoofer is only one part of the equation. The setup is probably the most important portion of the "integration" scheme. I brought up the subject here:

http://www.whatsbestforum.com/showthread.php?2990-Subwoofers-and-Time-Relationships

and the ensuing discussion quickly showed how complex seamless integration of a sub (or multiples) can be. Most folks don't take the time and effort to accomplish good integration IMO.

Lee

Right off the bat Lee gave the best answer first.

It's easy to make a great subwoofer sound horrible when it's not properly integrated which can be one of the hardest things to do. It's probably more proper to refer to subwoofers as bass systems since any full range speaker has a bass system. Someone referred to the bass of the Wilson Maxx speakers but if you cut away the bass portion of that cabinet and located it separately from the mid/tweeter section it would effectively be a subwoofer.

There is absolutely no reason a properly designed subwoofer can't be integrated into speaker set-up as well if not better than a full range speaker. It just proper takes knowledge of how the sub reacts to the room and speakers through placement, proper crossover, phase, polarity and EQ never hurt anyone.

 

[FrantzM]

"Fastness" or "slowness" can be measured. One may anthropomorphically equate light with fast and heavy with slow, but the fact of the matter remains that Sebastian Vettel's heavy monocoque will always be faster than a toddler's light plastic tricycle - even if one switches drivers. There is more to acceleration than mass, and a certain Sir Isaac wrote about it several centuries ago. In the case of "slow cones", the limiting factor in acceleration is, more often than not, a low-pass crossover.

fish

Care to elaborate, especially the last part... " the limiting factor in acceleration being the "low-pass crossover" ????

 

[fishnchips]

This is analog filter theory, it is covered extensively in many textbooks.

 

[twelti]

I am going to start a thread on "fast" and "slow" subwoofers very soon. I would like to put it to bed.

 

[diggo]

To me, the biggest issues are not the subs or drivers. If the room is not properly treated, moving a sub even by a few inches can make a dramatic difference to the sound. If the room is not properly treated, room resonances mask the actual sound emitting from the sub. If the subs are located away from the walls, SBIR is a big problem. If the system crossovers arent set optimally, SBIR from the mains is also a big factor at low frequencies. If all the preceding problems arent properly mitigated, the issues of one particular sub versus another (fast, slow, whatever) are almost irrelevant.

Treating the room isnt sexy, so most attempts to do it are pathetically poor, particularly among audiophiles. People prefer to spend money on sexy gear, not rooms and room treatments. Most have no idea of the requirements to properly treat a room. Many make a token gesture, typically without any appreciation of the true nature of the problem. Their listening experiences are then filtered through the prism of their room. It's no wonder very few are satisfied with subs and struggle to describe the results.

Sean

 

[FrantzM]

To me, the biggest issues are not the subs or drivers. If the room is not properly treated, moving a sub even by a few inches can make a dramatic difference to the sound. If the room is not properly treated, room resonances mask the actual sound emitting from the sub. If the subs are located away from the walls, SBIR is a big problem. If the system crossovers arent set optimally, SBIR from the mains is also a big factor at low frequencies. If all the preceding problems arent properly mitigated, the issues of one particular sub versus another (fast, slow, whatever) are almost irrelevant.

Treating the room isnt sexy, so most attempts to do it are pathetically poor, particularly among audiophiles. People prefer to spend money on sexy gear, not rooms and room treatments. Most have no idea of the requirements to properly treat a room. Many make a token gesture, typically without any appreciation of the true nature of the problem. Their listening experiences are then filtered through the prism of their room. It's no wonder very few are satisfied with subs and struggle to describe the results.

Sean

Welcome to the WBF. Great (first) post. I would add that even in a well treated room moving the subs a few inches may result in noticeable change in sound/performance. Else I agree with you.

 

[twelti]

Room treatment

Treating the room isnt sexy, so most attempts to do it are pathetically poor, particularly among audiophiles. People prefer to spend money on sexy gear, not rooms and room treatments. Sean

All true. Plus, room treatments for low frequency problems aren't cheap by any means.