Ron's Speaker, Turntable, Power and Room Treatment Upgrades

ddk

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IF subs could help an arguably too-small room sound more like a big room, would that be potentially useful?



The movement of two cones in "phase quadrature" would be 1/4 of a cycle apart in time. When one cone is halfway through the cycle, the other cone is either 1/4 of the way through that same cycle, or 3/4 of the way through that same cycle. By way of imperfect analogy, they dance the same dance but one is always 1/4 of a step behind the other.





Imo you just put your finger on the heart of the matter! But I think you are missing one critical piece of information:

Bass cancellation is inevitable!

You cannot choose between having cancellation and not having it; you can only choose between ignoring it and doing something about it (and most of us ignore it because we don't realize it's happening). Bass cancellation is what dips in the in-room frequency response are caused by. All non-anechoic rooms have them.

In-phase reinforcement is not exactly desirable either. That's what creates in-room peaks. Perceptually, peaks are even more objectionable than dips.

The way to minimize cancellation would be to use one big sub in a corner. This will give you the deepest and loudest bass, but it will also be very far from smooth.

A fairly even distribution of cancellation and reinforcement results in smooth bass, and "smooth" bass = "fast" bass. So what we are trying to do with a distributed multisub system is, deliberately and intelligently manage cancellation and reinforcement, because both are inevitable and too much of either is undesirable.

There is no perceptual price that is paid in "articulation" when you smoothe the in-room frequency response via a distributed multi-sub system. The ear does not hear the "leading edge" of bass energy. The ear responds too slowly to the presence of bass energy to do so. What it DOES hear are the higher harmonics (perceptually that's where the "leading edge" comes from), and it also hears the in-room frequency response. As I previously explained, the ear actually has a heightened sensitivity to frequency response in the bass region relative to the rest of the spectrum, so this is the most important issue from a perceptual standpoint. Decay is directly tied to frequency response in the bass region - if a note is taking too long to decay, it is because there is an in-room peak at that frequency. Solve the one problem and you have solved the other.

I readily admit that the whole idea of a distributed multi-sub system seems highly counter-intuitive at first glance. The question is whether it actually makes a worthwhile sonic improvement, which of course cannot be established with words. But it might be useful to look at this from another angle anyway:

With a single subwoofer, in-room peaks and dips with a spread of plus or minus 8 dB are not uncommon. Let's say your worst peak is 8 dB above the "average". And let's say we can tolerate a bass peak 3 dB above the "broadband average" of our main speakers before that peak "blooms" too much. So we set the level of our subwoofer such that the peak is not objectionable, which puts the "average" level of the subwoofer region (which was 8 dB below that peak) about 5 dB down relative to the rest of the spectrum. So we'd be missing out, but this is usually preferable to turning the sub up louder and cringing whenever that peak is excited.

With a good distributed multi-sub system, our in-room peaks and dips will typically be about plus or minus 3 dB. Now we can turn up the gain on our subwoofer amp and get our 'average" bass region SPL to approximately match the "broadband average" SPL of our main speakers without the remaining small peaks being objectionable, so we are no longer missing out.

One alternative method of getting this kind of in-room smoothness is to use a single sub and rely on equalization, which has this drawback: With only one sub, the more we use EQ to improve the in-room frequency response at one listening location, the worse we are making the frequency response elsewhere in the room. This is because the room-induced peak-and-dip pattern is significantly different at different locations in the room. With a distributed multi-sub system the frequency response is much more uniform throughout the room, so that if we do still have a problem frequency, chances are it's a "global" (throughout-the-room) problem rather than a "local" one... which actually makes it a very good candidate for correction via EQ! In other words, not only does a distributed multisub system reduce the in-room peaks-and-dips, but it also reduces the variation in that peak-and-dip pattern from one location to another throughout the room. And EQ can make a distributed multisub system better for everyone in the room, not just for the sweet spot.



When we reduce the signature that our small rooms super-impose on top of the recording, we hear more of the recording and less of the room. This is difficult to do in the bass region because the wavelengths are so long, but the phase quadrature technique is one way of making an improvement in this area, by "pushing back" the walls of the room much like professional room treatments can do higher up the spectrum.

So in one sense it's not natural, but maybe it actually sounds more natural.



That's a perfectly reasonable argument, but sometimes the ear does not PERCEIVE the way the mind reasons.

Please click on the link at the bottom of this post, and scroll down to the section entitled "The Spatial Effect." It's only a few paragraphs long. The writer is a mathematics professor at UCLA and a concert violinist. (The last time I spoke with him in person, Robert Greene was developing the nineteen-dimensional mathematics that will form the theoretical foundation for the next step beyond string theory.)

Assuming you already have at least two subs, you might even try it and see if it sounds more or less like you are hearing a live performance. If not, it is easily reversible.



Another tool for the bag is the most I could hope to convey to an industry professional.

If your system is already as close to perfect as you can reasonably imagine, then YOU have no need for anything I have described. But if you have a CUSTOMER who is fighting a losing battle against a small room, having another tool in your bag is not a bad thing! (If you are ever in that situation feel free to contact me, don't worry I won't try to sell any of my stuff to anyone involved.)

Below is the link to Robert Greene's review, read it as a commentary on the distributed multi-sub CONCEPT, rather than as a commentary on a particular product. For the record, TAS went on to give the system a "Product of the Year" ("POTY"??) award, so presumably some of the ideas it embodied had some merit. But those ideas could be even better implemented via state-of-the-art subwoofers. If nothing else, take a look at the section entitled "The Spatial Effect":

http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/

Thank you for the thorough explanation Duke, very much appreciated!

So quadrature or 30/60/90 phase inversion is basically a form of time delay, right? The popular subs I usually come across almost all come with built-in electronics and some form dsp xover, that’s where I usually see quadrature and in that configuration all of those subs are a non starter for me, there’s absolutely no way to use them in a high end setup. IMO despite the extreme price of they were never designed for use with a high end system to begin with so they get eliminated.

Coming back to your Swarm, are the subs synced or is it just random quadrature? Long time ago I learnt that it’s all about the bass, get that right and everything else falls in place. Bass is always the challenge in speakers, electronics, turntables, etc. the best sounding systems get that right and it’s quality over quantity. Believe me I appreciate me tools and you never know where our paths might cross in the future Duke.

david
 

Duke LeJeune

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Thank you for the thorough explanation Duke, very much appreciated!

Thank you, David!

So quadrature or 30/60/90 phase inversion is basically a form of time delay, right?

"Phase quadrature" refers to a rather specific phase relationship: Ninety degrees of shift, between the two signals.

This 90 degrees of phase shift can be looked at as a time delay, if we're talking about a single frequency. But the amount of time delay increases proportional with the decrease in frequency, and vice-versa, so it's not a constant time delay. That's clear as mud, right?

Lemme try again. Here is an image depicting two sine waves in "phase quadrature" relative to one another. PhaseQuadrature.jpg

The two sine waves are offset from one another by 1/4 of a cycle. One-quarter cycle corresponds to 90 degrees of "phase rotation" (360 degrees being one complete cycle).

So if those are 100 Hz sine waves, the time difference between the two is 1/4th of 1/100th of a second. If those are 20 Hz sine waves, then the time difference between the two is 1/4th of 1/20th of a second.

Coming back to your Swarm, are the subs synced or is it just random quadrature?

When using two amps to drive my four little subs, the two on the left-hand side of the room are driven by one amp and the two on the right-hand side of the room are driven by the other. So the two subs in each pair are "synched", or in-phase, with one another.

Then what I do is, take the phase knob on one amp, and rotate it to "90 degrees". So now the two subs on one side of the room are 90 degrees apart in phase from the two subs on the other side of the room. See the image above. Thus far, this has all been deliberate, not random.

Here is where the "randomness", or more precisely "semi-randomness", or more precisely still "de-correlation" comes in: Assuming asymmetrical distribution, each of the four little subs is a different distance from all four of the room's boundaries in the horizontal plane. So when the output of each sub reaches, for example, the rear wall, the wall bounce occurs at a different point along the sine wave for each sub. Having the left and right pairs of subs in phase quadrature introduces yet more de-correlation. The net effect of all this jumbling up of the reflections in time and phase is that the reverberant field of our small room now starts to behave more like the reverberant field of a much larger room (longer reflection path lengths relative to the wavelengths also equals more de-correlation, which is why big rooms generally have more natural-sounding bass than small rooms). And because in the bass region we cannot hear the first-arrival sound as a distinct event (because it happens faster than our ears can register bass energy), from a PERCEPTUAL standpoint what matters the most IS this reverberant field.

Long time ago I learnt that it’s all about the bass, get that right and everything else falls in place. Bass is always the challenge in speakers, electronics, turntables, etc. the best sounding systems get that right and it’s quality over quantity.

Yesss! The thinking behind multiple subs scattered around the room is focused on quality, not quantity. Convincing audiophiles of this is a bit of an uphill battle, but nothing compared to the subsequent battle they have convincing their wives that they need three more subs! That's why my subs are small.
 

cjfrbw

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Interesting. I have a 'swarm' of four subwoofers, with one elevated above the ears (a la Geddes?). It is easy enough to reverse the phase of one of them with a flick of the switch. I can try it, but I doubt that I have the chops to hear that much without expectation bias giving a helping hand.
 
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Ron Resnick

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Thank you, Duke! (I will have to read that one a few more times.)
 
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Ron Resnick

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Gentlemen: For those of you who are puzzled why I am even remotely theorizing about a subwoofer system for my Pendragon speakers, think of it this way: eight 8” inch woofers add up approximately to the surface area of two 15” inch drivers. The Wilson Audio XLF employs a 13” driver and a 15” driver — almost the same surface area as my woofer tower.

I don’t think anybody thinks it is per se wacky to consider using subwoofers with XLFs in a medium-size or larger room. After all Wilson Audio made Thor’s Hammers for XLFs long before the Master Chronosonic and Subsonic.
 

Mike Lavigne

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Gentlemen: For those of you who are puzzled why I am even remotely theorizing about a subwoofer system for my Pendragon speakers, think of it this way: eight 8” inch woofers add up approximately to the surface area of two 15” inch drivers. The Wilson Audio XLF employs a 13” driver and a 15” driver — almost the same surface area as my woofer tower.

I don’t think anybody thinks it is per se wacky to consider using subwoofers with XLFs in a medium-size or larger room. After all Wilson Audio made Thor’s Hammers for XLFs long before the Master Chronosonic and Subsonic.

i'm not at all puzzled that you would enjoy this theoretical discussion.

OTOH the odds.........of actually achieving seamless integration of ANYTHING to increase the deep bass extension (already on paper -3db @ 16hz) of the Pendragon bass towers ...........are astronomical.

can you cobble it together? sure. when you actually get music playing in your new space i expect you will have your hands full for a very long time just getting what you already have on your plate working. then this thing? naaaah.

theoretical discussions are what we do here.
 
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cjfrbw

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I think that with the size of your space, you would get some benefit from outboard subwoofers. However, I would try to get an idea of how much actual 10 HZ use-able material you plan to listen to before incorporating that ambition.

I have about 600 sq. inches total of subwoofer radiating area for a room that I estimate is about 3400 to 3600 cubic feet (high ceilings and dog leg), and I think I need all of it. The M&K subwoofer alone that I recently got only claims to work for about 3000 cubic feet at most, but I think that might be generous.

It's really hard to estimate the contribution of good bass until you hear it. Then, not having it feels like an amputation. Those bass guitars are a colorful and very contributory lot, not to mention the 'presence' effect mentioned by Duke.

I was listening to "a screaming comes across the sky" by Bill Laswell, and the bass is a major contributor, not just a background theme holding the rhythm. Without good bass, you don't even get an inkling.
 
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Mike Lavigne

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I think that with the size of your space, you would get some benefit from outboard subwoofers. However, I would try to get an idea of how much actual 10 HZ use-able material you plan to listen to before incorporating that ambition.
.

non-existent 10hz musical content out there, particularly for a confirmed digi-phobe.

the only value of 10hz on paper is the headroom it can give you for the real world frequencies. but if you have to tame the inevitable doubling troubles from a less than ideal integration issue then you are trading a few on paper HZ extension for lower overall performance, and used assets likely better applied elsewhere as well as mental energy.
 

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i'm not at all puzzled that you would enjoy this theoretical discussion.

OTOH the odds.........of actually achieving seamless integration of ANYTHING to increase the deep bass extension (already on paper -3db @ 16hz) of the Pendragon bass towers ...........are astronomical.

can you cobble it together? sure. when you actually get music playing in your new space i expect you will have your hands full for a very long time just getting what you already have on your plate working. then this thing? naaaah.

theoretical discussions are what we do here.

Just my wishful thinking Ron. I am with Mike here. Thinking or planning outloud is ok. But I really do hope you get a taste of you system in your new room first before making more sunk cost.

Kindest regards,
Tang
 
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Ron Resnick

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Just my wishful thinking Ron. I am with Mike here. Thinking or planning outloud is ok. But I really do hope you get a taste of you system in your new room first before making more sunk cost.

Kindest regards,
Tang

Other than having bought a relatively inexpensive pair of used JC1s I am just enjoying, as usual, the theorizing, the research, the plotting, the planning.

Hopefully I will be playing music on the speakers in a revised listening room in a repaired house later this year. I am looking forward to spending a couple of years understanding the system, getting used to the system and tuning things before I would ever consider a major subwoofer project.

Although I do want to be on official record with my theory that a medium sized room with large openings on the right side wall and on the left side wall can probably absorb a lot of low frequency power.
 

Ron Resnick

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. . . However, I would try to get an idea of how much actual 10 HZ use-able material you plan to listen to before incorporating that ambition.

. . . .

I really don’t think it’s about the musical information below 20Hz recorded on the album, and I do not listen to pipe organ music.

I really think it’s about infrasonic ambient cues/spacial information.

There is a good reason Kevin of Evolution Acoustics made MikeL’s speakers to go down to something like -3dB at 7Hz, and I don’t think it’s merely to have the world’s most impressive-looking subwoofer column.
 

Duke LeJeune

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I have a 'swarm' of four subwoofers, with one elevated above the ears (a la Geddes?).

Yup, elevating one of the subs is Earl's recommendation, and your hard-core-ness is revealed by the fact that you went ahead and did that, which of course distributes your in-room sources in the vertical plane (complementing their distribution in the horizontal). I include the suggestion to elevate one of the units in my "Swarm Setup Guidelines", but most people don't take it that far. I tip my virtual hat to you.

... I am just enjoying, as usual, the theorizing, the research, the plotting, the planning.

Thank you for sharing your journey with us.
 

Ron Resnick

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Duke, and it’s okay to have one of the four subwoofers at twice the height of the other three subwoofers on the floor? That doesn’t create any kind of audible asymmetry?
 
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Ron Resnick

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A friend of mine said completely matter-of-factly that it is a fool’s errand to try to integrate ported Wilson Audio subwoofers with sealed full-range speakers or sealed woofer towers. This is somebody for whom I have a lot of respect, and who has a lot of experience with components I like, and if he and Gary Koh are on the same page on a particular issue I would be extremely loathe to go against their advice.

So two or four double stacks of Funk Audio 18” drivers (four or eight 18” drivers in total) with Nathan’s strongest magnetic structure, tuned to focus on 20Hz and below and to present a low impedance load to the amplifiers, with each cabinet powered by a JC1 (800 watts of Class AB at 4 ohms, and a somewhat similar topology to the Gryphon Class AB amps in the bass towers), and the two or the four boxes controlled by two Watch Controllers, is the current design plan.

With aluminum panels encased in a Baltic birch box exterior box the weight of the caninet will be about 400 pounds, not quite the weight of a Wilson Audio Subsonic. (Or is better damping achieved if the interior box is Baltic birch and is surrounded by an exterior box of aluminum?)

And all of this is for Jack and for LL21 so that when each of them visits me in Los Angeles and wants to play some “deep house” he’s not disappointed!
 
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Duke LeJeune

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Duke, and it’s okay to have one of the four subwoofers at twice the height of the other three subwoofers on the floor? That doesn’t create any kind of audible asymmetry?

In my opinion, that's definitely okay.

The unorthodox concept of deliberately spreading bass sources around the room ideally includes the vertical plane as well as the horizontal one. I don't see how it could cause any audible asymmetry assuming the subs are crossed over neither too high nor too gradually.

A friend of mine said completely matter-of-factly that it is a fool’s errand to try to integrate ported Wilson Audio subwoofers with sealed full-range speakers or sealed woofer towers.

Not that it's any of my beeswax, but did he offer an explanation?
 

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Ron, the Watch controller stops at 30hz. But that's ok because the Pendragons will likely do well with a little bit of reinforcement in the 20hz range to make it more even, because that's exactly where the modes and nodes begin is right under 30hz. You could maybe get a custom crossover for it, however. The Watch Controllers ability to adjust phase and Q is what are going to make the system do real well.
 
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Ron Resnick

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Yes, the lowest low-pass setting on the Watch Controller is 30Hz. The low-pass slope choices are 12dB and 18dB.

There is a “Q” adjustment (but no variable phase adjustment) on the Gryphon woofer towers. I’m not quite as pessimistic as MikeL is.
 
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Ron Resnick

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In my opinion, that's definitely okay.

The unorthodox concept of deliberately spreading bass sources around the room ideally includes the vertical plane as well as the horizontal one. I don't see how it could cause any audible asymmetry assuming the subs are crossed over neither too high nor too gradually.



Not that it's any of my beeswax, but did he offer an explanation?

No; I will ask him “why” next time.
 
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Duke LeJeune

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Yes, the lowest low-pass setting on the Watch Controller is 30Hz. The low-pass slope choices are 12dB and 18dB.

There is a “Q” adjustment (but no variable phase adjustment) on the Gryphon woofer towers. I’m not quite as pessimistic as MikeL is.

Between the adjustability that the Watch Controller gives you (lowpass filter frequency and slope, phase, and parametric EQ) and being able to adjust the system Q of the Gryphon woofer towers, I share your optimism.

Imo you don't need (or want) phase adjustment on the woofer towers; their most important job is to blend seamlessly with the panels, and if you mess with their phase you mess with that blend.
 

Folsom

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Yes, the lowest low-pass setting on the Watch Controller is 30Hz. The low-pass slope choices are 12dB and 18dB.

There is a “Q” adjustment (but no variable phase adjustment) on the Gryphon woofer towers. I’m not quite as pessimistic as MikeL is.

No reason to be IMO. Mike tuned his the old fashion way, moving them around and some changes to the room. IIRC he had to change the ceiling to get them right.

The Q on the Pendragons you'll adjust based on how it sounds with the amount and type of feedback your amps have. That's what they're for. On the Watch Controllers the Q will allow you to be similar to the Pendragons. The phase will help you integrate without causing stronger modes. But Q for subwoofers can also help them play a bit lower if it's higher. It might take a few days, or a few minutes, but you'll have a lot of control to get there. Understanding what you're doing and why is part of the key, maybe someone will help you setup?
 

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