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Matthew J Poes

Matthew J Poes

Full Audioholic
"Anyone who cannot be bothered to point out his problem with a response and just points to generic articles (on "small rooms" no less which wasn't part of the subwoofer myth article) without so much as giving me a clue WTF his point is in the first place (since he couldn't be bothered to state anything at all) and then rates posts dumb deserves the same in return, IMO. Frankly, Gene, I expected better from you by your reputation. Call me disappointed."
MJP: Sorry you feel that way, hopefully I've been more clear in my own response.

"I'll cover all my major points anyway (as clearly I don't mind discussing something instead of pointing to yet more articles, most on your own site at that):

-Ask Jim Thiel or any of his customers over the years what they think about time coherent audio. Even a subwoofer needs its early wave arrivals to align as closely as possible to the main speakers for the primary listening location."
MJP: Show the science. While I actually think time coherence matters to some extent, the literature doesn't strongly support this. Just Phase coherence. What Thiel or his customers think is of little consequence. That's not how you argue a point. Appeal to the bandwagon?
This doesn't really give much hope for the importance of zero phase systems. I agree with Putzey myself, it might not make a huge difference, but it makes enough to do it when you can. Theil's way is too compromised, those speakers are only zero phase in a very narrow window. Compromised in other ways because of it.

As for subs, the point of the article, there is no issue with making phase coherent systems in the bass, and even time coherence isn't that hard. I have a special technique for this which I've presented on at AXPONA.

"-I could point to numerous sources on the many advantages of near-field subwoofer placement (removing the room from the equation for smoother frequency responise and more tactile feel with far less power needed to energize the MLP space as well, giving a pants shaking feel without the danger of ear splitting levels needed to achieve it further away). I don't have to justify that statement in the slightest. Some people love it. Its limitation is placement hazards and limited to one or two seats for optimal listening, making it a poor option for a large room with multiple rows of seating. It's also a subjective experience, not a myth as your writer claims.

It's not missing realistic reflections in that the recording (if it's a real space) already has them. Most of the reflections (reverb) you're likely to actually hear in any kind of "ambient" manner are probably not being produced by the subwoofer, but the other speakers reproducing higher harmonics. Adding subwoofer level "reverb" is more than likely going to muddle the original sound waves (more interference from your room, not the one of the original recording and thus not actually in the recording itself). Look at low damping factor setups and see how good extra waves sound when they keep going after the signal has stopped.

Thus, adding room reflections to the ones already present in a recording is also well known to blur the original acoustic atmosphere. What's the point in multi-channel immersive audio like Auro-3D whose sole goal with music is to recreate the actual environment of the room the music is being recorded in (dual quad microphones that reproduce the ACTUAL reflections of the real environment of the recording across 8+ speakers) if you can just bounce your sound off the living room walls and call it a day as your writer implies?"

MJP: I already responded to this. Feel free to cite your scientific literature with explanation of the psychoacoustic benefits and how it relates to accurate sound reproduction. You are mixing up issues by adding Auro. surround sound doesn't need reflections in the room at mid to high frequencies, but Auro does nothing to eliminate reflections or a reverberant low frequency field. What I cited earlier still holds true. Reflections at low frequencies are how we percieve spaciousness.

"-Subwoofer "speed" is a non-starter in that driver action is just a basic function of mechanical motion controlled by basic physics. Larger drivers need more power and a larger magnet to control them adequately. A small subwoofer with a small amp and a small motor can perform far worse than a large sub with a large motor and a negative feedback control system. Choosing a smaller subwoofer purely on its driver size without considering the rest of the specs isn't a myth. It's dumb."
MJP: The myth is that people think small subwoofers sound faster. I feel like we agree on this but somehow you are disagreeing. Are you saying people don't claim that small subwoofers are faster than large ones?

"-Do bass traps no longer function in the real world and are they not easier to set up for a beginner than phase-aligned dual subwoofers and also a lot cheaper to boot? Shouldn't they be done first before trying to make multiple subs work so you have less issues to deal with? What's "dumb" about that? Your writer ignored that aspect entirely in favor of pushing multiple subwoofers. But my post is dumb for pointing out easier alternatives to try first or in addition to multiple subwoofers? OK...."
MJP: Can you provide proof of bass traps working below 100hz as effectively and cheaply, in a room, as multiple subwoofers? I'd like to see that. It's not cheaper or easier. They don't work. Bass traps need to be large and cover large areas. You disagree? Provide your proof with a cost comparison. I've been doing this for long enough and setup rooms both ways. I use bass traps and I believe in them, but they are not nearly as effective as multiple subwoofers below the rooms transition frequency. Not even close. This is pretty well excepted.

"-I also think removing features from a site because of some rating Google uses is rather sad. You're letting a giant corporation dictate the features of your web site? If you keep putting the absolute dollar above integrity and you'll soon find you no longer have any of the latter left.

Have a nice day."

MJP: If you actually understood what you were talking about. This isn't just about the dollar. The articles were being delisted. They couldn't even be searched for. It was as if they didn't exist anymore unless someone already went to our website. It dropped traffic. We can't fight this, Google has a lot of power and we have to play along. We don't spend all our time and money just to make you happy. We have to make this work for the masses.
 
Matthew J Poes

Matthew J Poes

Full Audioholic
Of course below Schroeder has plenty of reflective action going on, but what I remember reading sounded more like comments for the room reflection qualities of a speaker's interface rather than a sub....I might need to reread it.
I was referencing spaciousness, is that the confusion? We hear a rooms size, its spaciousness, largely from reflections at low frequencies.
 
lovinthehd

lovinthehd

Audioholic Slumlord
I was referencing spaciousness, is that the confusion? We hear a rooms size, its spaciousness, largely from reflections at low frequencies.
I was thinking more of sidewall/floor/ceiling reflections of speakers rather than subs in that regard, yes. Altho I do think a good solid base of bass adds to a speaker's abilities to convey the rest well but I can position my subs in various places in the room rather than the speakers for tuning the effect of the boundaries as to what I think of as spaciousness.
 
Matthew J Poes

Matthew J Poes

Full Audioholic
I was thinking more of sidewall/floor/ceiling reflections of speakers rather than subs in that regard, yes. Altho I do think a good solid base of bass adds to a speaker's abilities to convey the rest well but I can position my subs in various places in the room rather than the speakers for tuning the effect of the boundaries as to what I think of as spaciousness.
I'm using the standardized definition as used by David Griesinger, which seems to be the accepted definition of the term in acoustics.

All of these terms are hard, we all use them and don't all mean the same thing. Worse yet, is trying to measure why we perceive what we perceive.

You might find that one interesting. Look what they had to do just to get to some common concepts and then align them with actual objective concepts we can define and measure.
 
lovinthehd

lovinthehd

Audioholic Slumlord
I'm using the standardized definition as used by David Griesinger, which seems to be the accepted definition of the term in acoustics.

All of these terms are hard, we all use them and don't all mean the same thing. Worse yet, is trying to measure why we perceive what we perceive.

You might find that one interesting. Look what they had to do just to get to some common concepts and then align them with actual objective concepts we can define and measure.
Thanks, will give them a read.
 
VonMagnum

VonMagnum

Senior Audioholic
Given my account has been slowed to a crawl (and again, I can only surmise this was done purposely as I see no one else complaining about slowness and it goes away if I log out), it's a bit more difficult to do a proper response as I get to sit here forever waiting for it to update quotes, etc. It's hard to have a civilized discussion with my hands tied behind my back. If you want to ban my account, please do so. It's better than screwing with me and by god if makes your arguments look bad without saying a word, IMO. I'll try to respond as best I can here, however.

All I originally really wanted was to make a few comments and thus wondered what happened to the commentary section as I was sure it was there in the past. The answer appears to be it's Google's fault. How do all the news sites manage to have comments sections without disappearing from the Universe? I do agree Google sucks anymore and Bing just seems to be a reflection of Google's results. I miss the days when you could search a half dozen search engines and get different results. Now if Google doesn't show you what you're looking for (and more often than not I'm finding it doesn't), you're pretty much sunk. I've noticed more and more often any kind of a search on Google results in corporate web site results even if you're looking for "reviews" and make that quite clear in the search. Pages and pages and pages on a subject from the company that makes whatever product and consumer reviews are nowhere to be found. It's time for a new search engine, IMO as Google has clearly bowed to the pressure of the dollar themselves.

First off, let's start with some articles that talk about what I've been saying. I LOVE this one as it talks directly about Toole and Audioholics in the same article and it's all about those "good room reflections" that's mentioned over and over again above.


I agree wholeheartedly with that article. Reflections in a room mar the original signal, not improve it. My room sounds a lot better after putting dampening and deflecting areas in the room and I don't mean just hanging diffusers, but dual purpose devices like thick dark drapes in key places where I needed to block things like entrances (helps with heating/cooling on a bilevel too) and the rear wall. Early acoustic absorption for the first reflections also got rid of slap echo and stutter issues. The brick wall fire place in the middle of the room changes the reflective properties with another big drape across form it on the other wall, breaking up a mid-room mode to some extent where the room changes shape (due to a half bath), blocking all the corners with absorptive material or even furniture where appropriate (very absorptive oddly enough to have a chair in that corner). Book cases in the front of the room behind the speakers diffract the rear reflections behind the mains and absorb on the sides with material. Room "decorations" on the walls all around the room (using movie props and posters in many cases no less) also help break up the parallel wall reflections in at least part of the frequency range. Is it perfect? No. But compared to where I started, it's a massive improvement. The room was live and fluttery and awful sounding originally. It's now dead quiet, echo free (shout as loud as you want; it sounds like you're yelling into an abyss of drapery dead as can be of any discernible reverb).

My problem with the article is that it ignores the possibilities of things other than what the author is pushing. Myths? More like opinions. Near-field bass isn't realistic, for instance? How so? Prove it. Where are those articles proving near-field bass doesn't sound good?

The notion that direct bass doesn't exist without room reflections and that there is no direct sound field sounds absurd to my ears, literally. How do you hear bass with in-the-ear headphones? Reflections in your ear canal? Standing waves in a room don't mean sound waves don't propagate through the air. The length of the wave is irrelevant as it is moving and it moves your ear drum in response. Bass is non-directional below "about" 80Hz. How can you hear the room size from bass when you cannot even tell where it's coming from without moving around or listening for rattling or other clues? Most of the directional cues in music for bass guitar and the like are at higher harmonic frequencies out of the subwoofer range, which is typically below 100Hz or even 80Hz. Mid-bass definition is well above that range. That is where reverberant sound is more important and that is a good thing as it means you can get away with putting a subwoofer in odd places if that helps eliminate the room modes as you don't have to worry about the lack of direct sound affecting perception.

For example, I found if I face my subwoofer directly into an end table, my overall bass response in the room is far better than even the same location facing the listening couch. I did a "sub crawl" all around the front half of my room when I first bought the house and found the response TERRIBLE everywhere I went with the sub as the room modes varied by frequency and were merciless anywhere near the listening locations. I was terribly upset because I bought the house after looking at dozens in my price range because it had a room that looked like could work for home theater when most had fireplaces where the TV should be or all sorts of open doorways, etc. But for whatever reason, pointing the sub right at the end table I placed near it for a lamp, phone, etc. broke up most of the peaks at the MLP and gave reasonably even frequency response at the main listening location (this was before room correction was common). It went from +/- 12 or more dB to +/- 6dB at most. With correction now, it's +/- 2.5dB over most of the range.

I get similar results without room correction upstairs using Carver AL-III ribbons with two 10" woofers. Is that because of multiple woofers or could be due to the room shape and other features in the room? The odd shaped rear walls, bass tube-like hallway exiting the other section of the back, heavy drapes on the left wall and open somewhat half wall on the other side? It certainly breaks up the side wall reflections and the rear wall modes. There are no bass traps and no subwoofer (just the two 10" woofers in each speaker that play flat to 26Hz). I've had people tell me the speakers are never the best place for subwoofers, but I get +/- 2.5dB from 26Hz to 200Hz at the MLP without any bass traps or room correction.

MJP said,

I already responded to this. Feel free to cite your scientific literature with explanation of the psychoacoustic benefits and how it relates to accurate sound reproduction.
OK. If you insist. I'm sure you've heard of Siegfried Linkwitz? Here's his AES engineering paper on ROOM REFLECTIONS: https://www.linkwitzlab.com/AES123-final2.pdf

It talks about and demonstrates through repeatable observations and even recordings that the room you listen to a recording in becomes fused with the recording you're playing back such that if you record the experience with microphones near your pinnae, you can then play it back through headphones and it will sound exactly like the recording in your room, not the original recording in the original room. The two ADD together. Thus, the less your room contributes reflection-wise to that experience, the less your room will add to the playback experience and the more the original will come through.

Siegfried Linkwitz said,

A simple experiment may serve to illustrate the perception of space.
- Listen to a CD through the 2-channel loudspeaker setup in your room.
- Record the CD playback with small omnidirectional microphones on the sides of your head near the pinnae.
- Play back the recording over the two loudspeakers and compare it to the initial CD reproduction.

Note that your room's contribution to the overall sound has become clearly audible because the room response is now imbedded in the direct signal from the loudspeakers. The reflections from your room are again fused with the direct signal and it dominates perception. Thus you hear a recording of your loudspeakers's sound in your room. The experience is similar to how you would hear a recording of a person speaking in your room, which is not how you actually hear the person or the loudspeakers in the live situation where their sound is fused with the familiar room response.

He also says 2-channel is sufficient to give the experience of a different space entirely

Siegfried Linkwitz said,

Two-channel playback in a normal living space can provide an experience that is fully satisfying as loudspeakers and room disappear and the illusion of being transported to a different place and moment in time takes over.
How does adding MORE reflections from your own room "improve" the recreation of the room that is in the recording of something like an Auro-3D recording of a given space? You're now blurring the two together. No, Auro-3D does not get rid of the room reflections magically on its own. You need to treat your room to reduce those reflections if you want more accurate reproduction of the recorded space. You'll probably never fully remove your room from the equation, but you can certainly take steps to reduce it.

Your article, on the other hand, seems to encourage room reflections, but it gives no information or advice on what kind of room or shape of room or size of room or materials of room might make a good listening space. Some of the best auditoriums on Earth have fantastic acoustics. Some of the worst don't. What's the difference? The article doesn't expand on that. It just tells me reflections are GOOD.

My room before treatment did not sound "good" to me. It was overly reverberant and downright stricken with flutter echo. I don't want "more" of that. Even IF my room is "great sounding" for a live concert, how does that help me more accurately reproduce the cathedral on the Auro-3D recording? I could hope to find a binaural recording and remove the room entirely from the equation and hope their dummy head is similar sized to my head. Or I could dampen the room to a "reasonable" degree so that my room is at least "dimmed" compared to the room coming out of the 11+ speakers in the room reproducing most of the actual room from the recording (and no I don't mean subwoofer bass with those 11+ speakers but the actual reverberant field well above that range).

Reverb on DSP systems is not produced by the subwoofer(s)! They are reproduced by the main and surround and height speakers ("presence" speakers in Yamaha terms). With the room now damped and 17 speakers spaced around the room like Dolby's diagrams, the sound reproduction is immaculate sounding. Auro-3D sounds like a different room altogether. Frequency response is excellent. Slap echo is non-existent. There is no sign of reverb when you shout in the room (I guess I don't shout at bass frequencies or I'd hear how spacious it is). It sounds almost dead. I try to leave the reverb to the recordings.

MJP said,

You are mixing up issues by adding Auro. surround sound doesn't need reflections in the room at mid to high frequencies, but Auro does nothing to eliminate reflections or a reverberant low frequency field. What I cited earlier still holds true. Reflections at low frequencies are how we percieve spaciousness.
Really? What's your definition of "low frequencies" because I never heard a subwoofer level "deep bass" wave with the main speakers turned off make me think the room was spacious or otherwise. Above the subwoofer frequencies higher level bass and above certainly become audible as reverb and they are also more directional. Your article was on subwoofer myths, not higher bass and mid-level reproduction reflections wasn't it?

MJP said,

Can you provide proof of bass traps working below 100hz as effectively and cheaply, in a room, as multiple subwoofers? I'd like to see that. It's not cheaper or easier. They don't work. Bass traps need to be large and cover large areas. You disagree? Provide your proof with a cost comparison.
Bass traps don't work? What? Are they magical devices now like Shakti stones that they don't work? They're "more difficult" to install than multiple subwoofers? I don't know what you'd even accept as "proof" given that you're contradicting every article I've ever read on bass traps. I mean how hard is it to stick a bass trap in the corner? How hard is it to hang some absorptive material like drapes for higher frequencies or some of those almost picture frame-like diffusers and absorptive panels? Compare that to needing test tones and moving subs around the room and adjusting them and phase, etc. to "best" cancel out as many bass peaks and dips as possible. I suppose you could find the latter more enjoyable as the former is more like decorating or light carpentry.

But you wanted PROOF. OK

Let's look at some evidence regarding the use of bass traps and my man Ethan Winer. He also talks about how the ROOM itself is the CAUSE (not the solution) of all the audio problems you have, as I have alluded to earlier. I think this quote says it all, "Bass Trap Basics: Reflections are the root of all evil." It also directly deals with your question of proof regarding bass traps below 100Hz as well as above 100Hz and the bass directionality, clarity, etc. and best and most appropriate of all it's called, "BASS TRAP MYTHS!" Yes, they do work below 100Hz, just not as much as above it. Bass below 100Hz is only half the equation anyway, as the article says.


As I tried to allude to before, the best solutions usually involve more than one methodology. Two subwoofers probably aren't going to solve all your bass problems, let alone all your room problems above that range. Of course, if you're only worried about one or possibly two seating locations, you might very well get away with one subwoofer, especially if it's near field as this takes the room largely out of the equation.

It's hard to prove the claim that near-field subwoofer listening is less realistic. This pretty much tells people with near field systems they suck. I don't use near field, but I can appreciate near-field. It has many benefits including tactile response and lower power usage per decibel. It has down sides like limited effect range and quite possibly difficult placement (try reclining your chair with a giant sub right behind it).

I can offer a discussion on the audible perception of near field by people that use it:


I can offer other advice on the benefits from an acoustic engineer with over 30-years of experience:


Now IF you're going to do multiple subwoofers to fix room modes, the BEST solution might very well be the double bass array (DBA): https://en.wikipedia.org/wiki/Double_bass_array

That will pretty much kill the pesky room modes (you'll still likely need treatments above that range, however). It can be done with as little as two subwoofer type speakers, but it has to be done correctly and it's well above the average Facebook reader and it's going to mean room modifications in most cases.

Hey, I'd love to listen to some music outdoors in a field with a 9.1.4 system (put the heights on booms) with a near-field subwoofer behind me. Perfect response as far as the speaker designs allow. I'd want multiple speakers and perhaps Audyssey DSX to simulate some reverb for sterile direct instrument recordings. Plug in Auro-3D music recordings and I'd be in the space they're at with my eyes closed. No fake room reverb. No standing waves. Think it would sound like crap without the room to make the space and the reflections and the reverb and all that crap you keep talking about that supposedly "makes" the sound? If I had the resources, I'd try it out in a heartbeat.

Now seriously, I'm not trying to crap all over your article. It clearly has a lot of good ideas in it, but I had some issues with some of the concepts being presented as if that's all there is to it. Good audio reproduction is not as simple as flattening out some bass with two subs. Frankly, if you and Gene can't take a little light commentary and criticism, you're better off not having a discussion forum on your site at all. Worse yet, if your boss is just going to call my comments "dumb" and then slow my account down, well that's not very adult behavior in my book and it only makes my point that perhaps commentary is sometimes not just desirable, but needed.
 
Alex2507

Alex2507

Audioholic Slumlord
@VonMagnum ,

Ethan Winer got banned here. :D

You're next, Mister !!! :p

I wouldn't know how it works but that slow page loading business is strange.

Frankly, if you and Gene can't take a little light commentary and criticism, you're better off not having a discussion forum on your site at all. Worse yet, if your boss is just going to call my comments "dumb" and then slow my account down, well that's not very adult behavior in my book and it only makes my point that perhaps commentary is sometimes not just desirable, but needed.
This is what you call light commentary? And I think it's unfair to paint Matt with the same brush.

I hate how uncivil people have gotten on the forums and I don't really like to spend a lot of time on forums.
In contrast I found this forum to be an example of how better men interact. Thirteen years with only a couple of weeks 'in the hole' (probation) is mind-blowing, all things considered. But the f^%& who put me on probation is now banned so he can go suck it. :D

Oh ... there I go being me. See? This place is a lesson for me on how better men behave.
 
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