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An Enticing Marketing Story, Theory Without Measurement?

Floyd Toole

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I wonder if it is helpful to consider the matter of multiple subs from POV of Toole's critique and cues for virtual sound objects. After all, if a real drum were played in your room, wouldn't it distort from the same eigentone influences? What's different about a virtual drum? How can a distribution of subs - no matter how beneficial to the FR at your chair - in any possible way more closely propagate the cues for the virtual drum than a single sub behind the main speakers at the origin of the virtual image?
The core of the problem is resonances in small rooms. Bands don't play in small rooms. A real drum energizes a certain set of small-room modes, giving it a room-modified sound. The same thing happens with a single woofer in the same location. Different small rooms would yield quite different real and reproduced drum sounds.

The notion of multiple subs and EQ is to neutralize the contribution of the room to what we hear, so that we have a better chance of hearing what the mic picked up and the recording engineer heard.
 

Kal Rubinson

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So, does Kal Robinson want to "play" the virtual drum in your room as per "1"? Is he recommending taking whatever sound is picked up from the spot the mic or mikes were mounted in, in whatever room it happened to be in, and drop the drum and the recording room into your room?
No. What I mean is that the effort is to create an illusion that transports the listener to the performance site and that means minimizing any influence of the listening room on the drum and any other instruments.
 

Kal Rubinson

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The real drum has no sound of any room. The one recorded does. That is, the drums were not recorded in anechoic chamber. If you add your room sound to it, you are doubling up.
I would say it more forcefully: If you add your room sound, you are corrupting it.
 

Kal Rubinson

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Then we are back to only using room treatment, and treating rooms heavily - hardly a reality for a domestic room. EVERY real room has a sound. Thus we come back to multiple subs...
...................and multiple channels. Those provide additional spatial information from the performance space.
 

Floyd Toole

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Then we are back to only using room treatment, and treating rooms heavily - hardly a reality for a domestic room. EVERY real room has a sound. Thus we come back to multiple subs...
I was focusing on the bass. Above the transition frequency humans exhibit great ability to "listen through" rooms. It happens in real life, including live unamplified performances. A voice or a music instrument is clearly identifiable, in great detail, in different rooms. The same has been shown to apply to loudspeakers. Yes, rooms add some sound, but the most neutral loudspeakers are identifiable in very different rooms. So it is really not necessary to eliminate the room - if done, it sounds awful.
 

DDF

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I was focusing on the bass. Above the transition frequency humans exhibit great ability to "listen through" rooms. It happens in real life, including live unamplified performances. A voice or a music instrument is clearly identifiable, in great detail, in different rooms. The same has been shown to apply to loudspeakers. Yes, rooms add some sound, but the most neutral loudspeakers are identifiable in very different rooms. So it is really not necessary to eliminate the room - if done, it sounds awful.
Building on this, Dr. Olive's testing did show that some correction above the transition frequency was useful if the speaker itself has a rather poor power response in the mid range.
http://seanolive.blogspot.com/2009/11/subjective-and-objective-evaluation-of.html
"The largest measured differences among the different room corrections occur below 100 Hz and around 2 kHz where the loudspeaker had a significant hole in its sound power response. The room corrections that were able to fill in this sound power dip received higher preference and spectral balance ratings"
 
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The real drum has no sound of any room. The one recorded does. That is, the drums were not recorded in anechoic chamber. If you add your room sound to it, you are doubling up.
How can you possibly not add your room sound to it (headphones mostly excepted)? That flows from Toole's critique. How can we best help the brain "listen through" rooms, as Toole suggests a few posts ago?

The sound of the virtual sound object - oboe, drum, or Diana Krall - that the recording team tries to deliver is a "social construct" of the sound of an oboe, drum, or even Diana Krall. It is a social construct in the sense that you want listeners to say, "Gosh, that sure sounds like (the way I imagine) Diana Krall would sound in my living room"... but that's different than the usual undefinable claim about delivering "realism".
 
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amirm

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How can you possibly not add your room sound to it (headphones mostly excepted)? That flows from Toole's critique.
We are talking about bass frequencies. Here, resonances cause some 20+ dB variation. And that variation will be different from room to room, and seat to seat. How can you say this represents fidelity to the drums?
 

Cosmik

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First, are we talking about (1) the listener being "there" or (2) the drum being "here"?
(3) Your room transported to the venue and the end wall opened up.
 

Krunok

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Building on this, Dr. Olive's testing did show that some correction above the transition frequency was useful if the speaker itself has a rather poor power response in the mid range.
http://seanolive.blogspot.com/2009/11/subjective-and-objective-evaluation-of.html
"The largest measured differences among the different room corrections occur below 100 Hz and around 2 kHz where the loudspeaker had a significant hole in its sound power response. The room corrections that were able to fill in this sound power dip received higher preference and spectral balance ratings"
Very true. From what can be seen from the graphs the winning EQ curves went all the way to 8kHz to linearise response.

C1.JPG


C2.JPG
 
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(3) Your room transported to the venue and the end wall opened up.
Earlier, I recognized that option because "it resembles the familiar proscenium theatre conceit". It may be your target and a good one, but aiming for some kind of social construct "sound of Carnegie Hall in the laneway behind my house" does nothing to actually remove the room from the sound. In a way, it just confuses the production because the recording is now as-if playing into some weird room with three walls. Nothing removes the room except headphones and they scramble cues in their own way.
 
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We are talking about bass frequencies. Here, resonances cause some 20+ dB variation. And that variation will be different from room to room, and seat to seat. How can you say this represents fidelity to the drums?
Nor sure I understand your point. The room soundscape is inescapable whether for stereo speakers or your very bassy Uncle Harry.

It makes sense to improve a room because tone will vary as you walk around a domestic-sized room, at least at first, esp in the low bass. A goal of treating the room acoustics is to make it easier for your brain to sort out the perceptual cues (not necessarily the stuff that "sounds" funny to your eyeballs on a plot*). The question I was asking is whether having multiple sources for low bass harms the cues for the virtual sound object although it seems there's no localization of bass below 80 Hz in lab tests.

*the results of comb filtering reflections look horrid on a plot but may have little impact on cues; we successfully sort out early reflections from nearby walls practically all the time when indoors
 

Krunok

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.. although it seems there's no localization of bass below 80 Hz in lab tests.
You don't need lab tests to confirm that, it is a simple physics. No localisation occurs because woofer diameter is much smaller than wavelength of 80Hz wave and below. It happnes gradually, of course. If membrane playing 80Hz and below would be large enough those waves would become very localised. ;)

Anyway, that means that answer to your questions is that multiple sources for low bass doesn't spoil anything related to "virtual sound object" nor localisation because their woofers are far too small to be localised at frequences below 80Hz where they play.
 

Krunok

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The real drum has no sound of any room. The one recorded does. That is, the drums were not recorded in anechoic chamber. If you add your room sound to it, you are doubling up.
This is of course true. And if I was to record that same drums in my room that would of course sound differently than playing the recording in my room of those same drums recorded in some studio room. IMHO the only thing that can be done is to dump room a little to have R60 Topt somewhere in the 300-500ms range north of 300Hz and below 300Hz fix linear response with EQ. And that's it, no further miracles are possible, we have to learn to live with sound of our rooms. The same is valid for people we listen speaking in those same rooms - in some other room their voices would sound different too. :)
 

Cosmik

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Earlier, I recognized that option because "it resembles the familiar proscenium theatre conceit". It may be your target and a good one, but aiming for some kind of social construct "sound of Carnegie Hall in the laneway behind my house" does nothing to actually remove the room from the sound. In a way, it just confuses the production because the recording is now as-if playing into some weird room with three walls. Nothing removes the room except headphones and they scramble cues in their own way.
If you want to remove the room, there are things you can do. But I don't want to remove the room. I think I want a two-way bridge between me and the recording, so that the sound of my voice or the opening of a wine bottle shares something of the same acoustic as the performance. I also want some 'dynamic acoustic' that responds to my head turning or moving around in my seat. Luckily, it just so happens that a speaker in a room does all this 'for free'. In my opinion, it couldn't be better.
 
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You don't need lab tests to confirm that, it is a simple physics. No localisation occurs because woofer diameter is much smaller than wavelength of 80Hz wave and below. It happnes gradually, of course. If membrane playing 80Hz and below would be large enough those waves would become very localised. ;)

Anyway, that means that answer to your questions is that multiple sources for low bass doesn't spoil anything related to "virtual sound object" nor localisation because their woofers are far too small to be localised at frequences below 80Hz where they play.
Overlooking the naive inclination (common enough) of deeming the Laws of Physics as the model and arbiter in a discussion of human perception, localization (a human perception) depends on how you test it. I mentioned the figure of 80 Hz because it is for present purposes a "worst case". On music, clean subs and sharp XO slopes nudge that point much higher.

We are asking if it is helpful to have subs spread around the room, granted they greatly reduce the variation in the room. So the sub to my left has 10% HD distortion and other distortions and a 18dB/8ave XO slope at 80 Hz (not to mention that slight buzz from my amp's old power supply). Which means there's a ton of very audible sound coming out of it north of 80. Seems pretty detectable to me.
 

Krunok

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We are asking if it is helpful to have subs spread around the room, granted they greatly reduce the variation in the room. So the sub to my left has 10% HD distortion and other distortions and a 18dB/8ave XO slope at 80 Hz (not to mention that slight buzz from my amp's old power supply). Which means there's a ton of very audible sound coming out of it north of 80. Seems pretty detectable to me.
Actually it is not - human ear is much more tolerant for LF distortion than at higher frequencies.
 

Cosmik

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I would advise anyone who wants to completely remove the room to try to listen to music in some space close to anechoic chamber. it would make you wish for the room to come back momentarily. :D
There might be a way around it: use some ambient mics, artificial (electronic) reverberation and artificial background noise when the record isn't playing. I suspect the real problem with an anechoic chamber isn't what it does to the music, but the silence and what happens to ordinary sounds in the room.
 
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