Comparison of small room acoustic models for home listening spaces - Page 4 - AVS Forum
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post #91 of 415 Old 11-24-2011, 01:08 PM
 
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Originally Posted by HopefulFred View Post

Are you saying...

You quoted me. That's what I said (speculated).

Happy thanksgiving.
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post #92 of 415 Old 11-25-2011, 12:30 PM
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Bigus, I know that this goes against the 'ideal', but you really can relax the symmetry requirement with multichannel. Consider this - with mono, one speaker playing, you can have lots of (audible!) interactions with the room. First reflections skewing the image, coloration due to SBIR/combfilter in the bass/low-mids. Our hearing is acute picking up all the necessary 'details' of room interactions. Now if you introduce another speaker and stereo material, and suddenly you have an image/'recording space'. And these cues giving the said image (partially) mask some of the conflicting(and not so conflicting) cues given by the listening room.(and also mask the poorly performing loudspeaker!)
Guess what happens in a multichannel system: front speakers usually still give the cues for different sound images, but now we have side/rear/height speakers giving us cues to the 'reverberance image'. Given that those cues consist mostly of uncorrelated signals (reverb-hash?) - there is no ill effect when such signal specularly reflects and superinposes with itself at the listening position - you just get... 'denser' reverb.
And the more (correctly processed) speakers you have, the more the room's contribution to the perceived soundfield is diminished. But yes, 'fly-by's', solid images placed to rear etc. are adversely affected - but as I said, the images are in the front, anchored to the screen usually, and ambiance comes from rear (it should from all channels actually)
Yes, there are lots of caveats to be inserted to above, but trying to get the topic interesting - cable discussions shouldn't be the hottest topic.
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post #93 of 415 Old 11-27-2011, 10:45 PM
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Originally Posted by Bigus View Post

Among others, these include anechoic, (NE) non-environment (sort of a "practical approximation" of anechoic), (LEDE) live end dead end, (RFZ), reflection free zone (a mild maturation/variation of LEDE), (RRZ) reflection rich zone, and ambechoic (ambient anechoic, i.e. blackbird studio C, approximated by the Widescreen Review room).

There have been many links posted which are all worth reading. The presentation by D'Antonio in particular is a great five minute synopsis complete with easy to understand ETC behavior of many of these models, especially as how they relate to a multichannel environment. Sound System Engineering is another good resource. There are tons of discussions on Gearslutz forums... worth the time to search on a varity of these terms/models and follow the links and discussions found therein. Home Theater Shack also has some great discussions, but more slanted towards understanding how ETC works and less about the fundamental models and which might be favored for a particular application. And searching the AES papers if you can will turn up many worthwhile reads (many referenced by other links/discussions).

In each of these links in this thread, forum discussions found in a search, etc. you will undoubtedly find many other links and references to expand your search.

I had the same problem as you... it had been years since I read about these models in any depth, and finding a decent starting point is sometimes the most difficult part.

Bigus;
I was thinking it would be nice to have the various room acoustic models summarized so people reading here could visually grasp each of them quickly.
(besides what is shown in Dr. Peter D’Antonio's Mono2Surround presentation)

Chapter 7.1 "Listening room design "from the book Acoustics and Psychoacoustics Applied (David Howard and Jamie Angus) appears to give a nice visual overview of them.
http://eetimes.com/design/audio-desi...n?pageNumber=0
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post #94 of 415 Old 11-27-2011, 11:51 PM - Thread Starter
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Mike, I'll take a look.

dannut, that makes sense. I'm approaching the problem from an idealized perspective. It seems reasonable that if the majority of source material doesn't require front/rear symmetry that the requirement can be relaxed. I'm still interested in solutions that satisfy both practical and idealized versions from an intellectual perspective. And on practical grounds, I wonder which I would actually prefer?

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post #95 of 415 Old 11-29-2011, 01:52 AM
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And on practical grounds, I wonder which I would actually prefer?

If you're not in the content creation business, then with 86% certainty you would prefer a more spacious presentation.
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post #96 of 415 Old 11-30-2011, 04:22 PM
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Originally Posted by Bigus View Post

Among others, these include anechoic, (NE) non-environment (sort of a "practical approximation" of anechoic), (LEDE) live end dead end, (RFZ), reflection free zone (a mild maturation/variation of LEDE), (RRZ) reflection rich zone, and ambechoic (ambient anechoic, i.e. blackbird studio C, approximated by the Widescreen Review room).

Good summary of the main models. I would like to add a subjective and an objective addition:

1) that all these models have been developed in professional environments where the objective is different to that in a home. In a home personally I think (and this is my subjective filter) it is all about enjoyment. If a little 'absolute accuracy' is sacrificed for the sake of maximum enjoyment then I'm on that bus.

2) that the proper way to design a room is to match the speaker to the room. A good room design for a pair of conventional cone / dome speakers will be substantially different to that for a pair of controlled directivity horn speakers. Yes, it is possible to design a room that works well for multiple different speaker types, but it will not be optimized. The historical development of the room response models such as RFZ, etc is inseparable, in my opinion, to the speakers that were popular at those times.

Things to read / listen to

A history of control rooms - a great, long paper summarizing the history of control rooms http://alexandria.tue.nl/extra2/afst...unster2003.pdf

This thread: http://www.gearslutz.com/board/studi...c-shift-3.html is of much relevance to this discussion, and has some very interesting comments from smart people who know their stuff.

Also, as an aside, we should all read / listen to the Heyser memorial lecture given by John Atkinson, Stereophile Editor at the recent AES. A fascinating examination of why what we measure is always going to be an approximation to what we perceive. http://www.softconference.com/aes/se...asp?SID=281052

Master of Minions, Acoustic Frontiers. We specialize in the design and creation of high performance listening rooms, home theaters and project studios for discerning audio/video enthusiasts.
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post #97 of 415 Old 11-30-2011, 08:22 PM - Thread Starter
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Nyal, more great information to read. Thanks, and welcome to AVS!

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post #98 of 415 Old 12-06-2011, 04:30 PM
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Nice thread for the most part, folks.

My thoughts are that these response models are conceptual. There are many areas of acoustics where we can't actually achieve the ideal, so we do what we are willing to do to get as close as we can. For example, I don't have an AT screen and I don't want one. Therefore my room will be inherently unbalanced - there is little I can do acoustically with a huge portion of my front wall.

When I approached acoustics in my theatre, I made a list of sound characteristics I was looking for and am using that as most of the guide for how I design the acoustics. For example:

(a)I have one main seat, down the middle, that I want to be as good as reasonable for two-channel music. I'm willing to compromise my ultimate multichannel performance for this goal to some extent... at a mix of perhaps 60% multichannel and 40% music.
(b)I want the bass to be even between all the seats
(c)I want the the response to be flat, or possibly with a slight house curve, in all the seats.
(d)I want good dialogue intelligibility from the center channel speaker in all seats
(e)I want the surrounds to sound somewhat "ambient" in all the seats (actually I'm not sure this was on my list but it probably should have been)

I also have some constraints:
(f) I don't want to use more than 2 inches of space on the sides... it is only a 10' wide room. I know this may limit the ultimate quality... that's my choice.
(g) I have some seats close to boundaries. I know that's said to be a good thing, and it might require me to use more absorption than otherwise. Oh well.
(h) I already owned decent smallish speakers which have the typical "normal" dispersion pattern. No horns, no waveguides, no CBT, no d'Appolito action.

And some preferences:
(h) I think I tend to desire a more "accurate" than "spacious" or as it's been put here "pleasing" sound.
(j) I'd like the room to sound larger than it really is.

Note that these aren't complete as I don't have my original notes on hand here - this is just meant as some ideas on one way to proceed.

From there it's simply a matter of figuring out how to accomplish as many of those things as possible, possibly with an order of precedence. for example my biggest priorities probably are:
1) maximum CC dialog intelligibility
2) flat-ish bass response, even in all seats (sort of the same thing anyway...)
3) good (pinpoint) imaging from the front two channels, I think it's useful for both movies and music

The first is going to imply controlled decay time and probably early reflection control. Ideally I'll become able to directly measure this using Speech Transmissibility Index (STI), which is normally considered to be a large space metric but I still think would be fun to play with. I suggested John put this in REW and he said it's on his list but not near the top. He said it's not appropriate for a small space but on the other hand Terry Montlick stated on AVS that he used to use it as part of his alpha certification for home theatres.

The second is going to imply modal control, which I can verify with waterfalls and the various decay measures in REW.

The third is likely to imply control of early reflections from L/R, especially given my speakers - and across a range of seats which does require a fairly broad swath of absorbent in the room - with an end result much like the "thin absorbent almost all the way around" that's been discussed here. Either way it is verifiable with the ETC as has been discussed.

Therefore those three items have been at the top of my acoustical list and the focus of my initial acoustical efforts. Next I'm launching into modal control of the bottom octave, adding subs to even out LF through the room, as well as adding diffusion. An image of my plan is actually on here in the "DIY diffusors" thread and I've sort of come into a "dead height-live height" plan. Will it work well? I think so but who knows... gotta install, listen, measure. I'll measure performance based not only on objective acoustical measurements but how often I say "wow" when I listen to music or watch movies. And by how many times I have to pause and go back to figure out what a character said! (that one better ultimately be never

I should add that a treasure trove of acoustical information is in the GS sticky Acoustics/Treatment Reference Guide.

Possibly even more useful would be standards for multichannel mixing rooms. Doesn't it make sense that we would want to hear our media reproduced the way it was intended, and if our rooms sound a bit like the dubbing stages and mixing rooms where it's created then we would presumably achieve that. Plenty of standards are available free online, and avare links to them all in this post as well as the following one.

I personally think the ideal response model is not the same for all channels in a multichannel setup . As noted before it's not really achievable but my best guess would be Center-NE/anechoic, Left/Right-RFZ, surrounds-ambechoic. As for LF, go for Welti/Devantier/Geddes - which really amounts to ... oh goodness... just make it work.

If you play with the demo of RPG Room Optimizer, it tells you to put absorption at LCR first order reflection points, and diffusers at surround first order reflection points.

I don't claim to be any sort of expert. I have not even yet read Toole's book, the mentioned passages of SSE (though I have read the small acoustical space chapter), or made it through a complete review of the standards in the avare posts above. I look forward to a full review of the Mellor/Hedbeck white paper mentioned earlier which on skimming looked to have some great ideas. And unlike those that Penn mentioned, I actually LIKE to study! It's great to have threads like these around, in fact I'd like to see some further and more in-depth discussion of the ideas. But we also have to face the fact that 99.9% of people on AVS are not at all interested in this depth.
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post #99 of 415 Old 01-02-2012, 07:11 AM
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Bump - time to re-awaken this thread for 2012!

Can we make some high level summary/conclusions, and Bigus post those in the 1st post as key points discussed/gathered in this thread?
(with links to key discussions)

I'd then vote to add this to the sticky "Setting Up Your Home Theater 101" under the "Sound Treatments and Acoustics" section.
Also, add it to Master Thread of favorite AT links that member jcthornton gathered.

Lot's of good discussion in here, a shame to have it go away.
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post #100 of 415 Old 01-02-2012, 09:03 AM - Thread Starter
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Lol, I'll have to reread the thread and see what conclusions i can draw. I do recall thinking that in the post above items a through e and h (the second one) and j sounded very much like my own design priorities.

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post #101 of 415 Old 01-02-2012, 12:03 PM
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Originally Posted by Bigus View Post

Lol, I'll have to reread the thread and see what conclusions i can draw. I do recall thinking that in the post above items a through e and h (the second one) and j sounded very much like my own design priorities.

Double LOL! All of aackthpt's goals would apply to my preferences, except "f", and I'm no too overly concerned about my back row.
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post #102 of 415 Old 01-02-2012, 12:25 PM
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Are you saying that no matter which set of goals you use in treating your listening room, they all sound the same and all you hear is the recording?

Actually, I agree with AJ on this one... It's not the room itself that creates a convincing illusion, it's the synergy between the recording (micing techniques etc.), the speakers characteristics (polar response, placement in the room etc.) and the room itself.

The way the speakers off-axis response together with early reflections affect the sweetspot and imaging and how stable the soundstage is when sitting off-axis etc. But, at the same time the recording/mix also affect the sweetspot and stereo perspective. A time difference mix and a pan-pot mix creates very different cues to our brain(s), and depending on the rolloff of our speakers and how the room has been treated this affect how we percieve the soundstage, positioning and "air".

Personally I favour a clearly defined, focused soundstage before a wide airy soundstage and have chosen my room and speakers for that purpose.

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post #103 of 415 Old 01-05-2012, 08:18 PM
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Originally Posted by hevi View Post

Actually, I agree with AJ on this one... It's not the room itself that creates a convincing illusion, it's the synergy between the recording (micing techniques etc.), the speakers characteristics (polar response, placement in the room etc.) and the room itself.

I both agree and disagree with all of your points. LOL. Sixty percent of the time, it works every time.

There's no reason to not extend the concept of source/speaker/room/listener to the recording, particularly since that's the ultimate source. However I somewhat object to the idea that there is "synergy" there. Speaking of HT, the intent is to hear what the content creator heard, period. Therefore if our speaker/room system has a similar response to that of the dubbing stage, we are golden. If there is a wide variety between dubbing stages, we are screwed; if they all are acoustically reasonably similar then we can do this, or at least some approximation considering the typical room size differences.

If we are talking about ultimate stereo listening performance, most audiophiles I have met are all too glad to tell you that the ultimate reference is a live music performance. In that realm these pan-pot or time-difference mixes should be irrelevant because we should presumably only be listening to naturally-miked, non-post-mixed audio. With that sort of material, the synergy idea may be applicable.

However, if we take multitrack recordings, it would seem optimal to make the listening room sound like whatever room the final mix was monitored in. This may actually allow a surprisingly large degree of latitude since one of the main design goals for those environments is for the mixes to "translate" well to a variety of environments. Nonetheless, I think it's reasonable to expect that precise room response to sound a smidgen better than others, just because it's the same content creator situation as with multichannel.

Ever read this article? It perfectly describes every audiophile I have ever met. One I know even likes to speak at length about live music being the reference point while listening almost entirely to rock&roll studio recordings. Sure his system sounds good; with that as typical source material does it matter? And a philosophical question, should your listening tastes be prioritized above your sensibilities in audiophilia or should your desire for the ultimate audio and recording influence what you are choosing to listen to? I'll tell you that I've heard some recordings I'd never choose... much like I never wanted to see The Fifth Element more than once. I'm glad those days are over.

BTW,Bigus, good catch on the multiple h's. It's not the only error in my diatribe (item g: good to have seats near boundaries, LOL), I guess I was tired when I wrote it.

From the silence in this thread I can only presume everyone has been off reading AES TD 1001 and other multichannel production documents.
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post #104 of 415 Old 01-05-2012, 08:53 PM
 
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Originally Posted by aackthpt View Post

Speaking of HT, the intent is to hear what the content creator heard, period.

Johnny mnemonic style? Retroactive binaural scan of the premises? How do you do that?

Quote:
Originally Posted by aackthpt View Post

Therefore if our speaker/room system has a similar response to that of the dubbing stage, we are golden.

Cool. What sort of mid-field soffit mount mains you using? JBL? Tannoy? Klein & Hummels? They sound identical, do they?

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Originally Posted by aackthpt View Post

If there is a wide variety between dubbing stages, we are screwed; if they all are acoustically reasonably similar then we can do this, or at least some approximation considering the typical room size differences.

We're screwed.

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Originally Posted by aackthpt View Post

However, if we take multitrack recordings, it would seem optimal to make the listening room sound like whatever room the final mix was monitored in. This may actually allow a surprisingly large degree of latitude since one of the main design goals for those environments is for the mixes to "translate" well to a variety of environments. Nonetheless, I think it's reasonable to expect that precise room response to sound a smidgen better than others, just because it's the same content creator situation as with multichannel

Sounds great. What standard should we use? LEDE? RFZ? RRZ? UHF/VHF?
With that easily settled, what sources at what polar coordinates?
NS-10s nearfield on the console? Genelecs mid-field? Easy enough. Now what happens when you play your Genelec mix on your NS-10's? Sound identical?
Btw, how are you confirming all this for literally hundreds of thousands of recordings?
See the issue?
Happy new year btw

cheers,

AJ
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post #105 of 415 Old 01-05-2012, 09:57 PM
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Originally Posted by AJinFLA View Post

Johnny mnemonic style? Retroactive binaural scan of the premises? How do you do that?

I didn't say it is verifiable. Goals are goals, often to be approached but not reached. I nonetheless don't see why two systems with similar frequency and time characteristics should sound significantly different. If that is not true with current measurements then we need to put our energies toward a better measurement method (encompassing hardware, data creation, and data interpretation) rather than concerning ourselves with the room response model. With a decent measurement system and decent standards in place, this isn't really a very difficult problem (well except the usual problem of getting people to know of a standard and then to actually follow it, but that is a problem of social engineering not a question of science).

Quote:


Cool. What sort of mid-field soffit mount mains you using? JBL? Tannoy? Klein & Hummels? They sound identical, do they?

There is a reason I said "similar response to" which does not mean "identical to".

Quote:


We're screwed.

To some degree, I agree.

Quote:


Sounds great. What standard should we use? LEDE? RFZ? RRZ? UHF/VHF? -snip-

Honestly I think it's irrelevant because I think reaching for sonic perfection in stereo listening in general is BS, both because it is impossible to achieve as you point out, but also because multichannel is easier. Also because I think in that arena we should aim for "enjoyable". For realistic sound, we should exit our seats and go absorb some real sound.

With that said, I vote for VHF. I'd go on "Wheel of Fish" in a second. And there are certainly people in this world that I'd like to see drink from the fire hose.

Also, you forgot about the "LLC" and "BFE" room models.

Indeed, happy new year AVS! *waves*
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post #106 of 415 Old 01-05-2012, 10:37 PM
 
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I really have no beef with the guy who says "I prefer X over Y". Padded cell over sane decor. $10k cables over rat shack. Terrific. Have at it.
It's when they start talking about "accuracy" and "ideal" and start interjecting objective reasoning for their purely subjective preferences for "accuracy" and "ideals" is when things tend to unravel.
Then I'm gonna carve you up. Real nice.

cheers,

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post #107 of 415 Old 01-06-2012, 05:02 AM
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I really have no beef with the guy who says "I prefer X over Y". Padded cell over sane decor. $10k cables over rat shack. Terrific. Have at it.
It's when they start talking about "accuracy" and "ideal" and start interjecting objective reasoning for their purely subjective preferences for "accuracy" and "ideals" is when things tend to unravel.
Then I'm gonna carve you up. Real nice.

Of course, there's never any arguing over a preference. One can, of course, object to how that preference came about. It's not as though we can all walk down to the corner to listen to an RFZ room then walk across the street to listen to an ambechoic room. Not that it's ever productive to argue over value judgments, but hey we are presumably all here because we enjoy entertainment.

As for "accuracy" etc, well that's why I mention measurement. I pretty much just assume that any statement in audio without a number attached is very fuzzy at best. Just like at least half (or so) of those made WITH numbers attached. Still, I guess if all we have is something "fuzzy" then it's better than having nothing.

Oh, and that WITH numbers rule doesn't apply to cash. Clearly that $10k cable, it's _definitely_ better than the one from rat shack. Although the rat shack one might be better if you get it off the floor... *grins*.
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post #108 of 415 Old 01-11-2012, 07:42 AM
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Originally Posted by aackthpt View Post

Speaking of HT, the intent is to hear what the content creator heard, period. Therefore if our speaker/room system has a similar response to that of the dubbing stage, we are golden. If there is a wide variety between dubbing stages, we are screwed; if they all are acoustically reasonably similar then we can do this, or at least some approximation considering the typical room size differences.

Even if there is a wide variety between dubbing stages, I have to assume they are all still aiming for a similar target - how the soundtrack will sound in a theatrical setting. There are standards here that should serve as a roadmap. The challenge is transforming those standards meant for large rooms into an implementation in a small room that meets the same goals (as close as possible)

Quote:


If we are talking about ultimate stereo listening performance, most audiophiles I have met are all too glad to tell you that the ultimate reference is a live music performance. In that realm these pan-pot or time-difference mixes should be irrelevant because we should presumably only be listening to naturally-miked, non-post-mixed audio. With that sort of material, the synergy idea may be applicable.

I'm of the firm belief there is no point talking about an "ideal" room for 2-ch music - simply too much variation in recordings, standards, etc etc. I've always wondered this question - what's the definition of the ideal playback system for electronic music? Or for really poorly recorded indie rock?

Quote:


Ever read this article? It perfectly describes every audiophile I have ever met. One I know even likes to speak at length about live music being the reference point while listening almost entirely to rock&roll studio recordings. Sure his system sounds good; with that as typical source material does it matter? And a philosophical question, should your listening tastes be prioritized above your sensibilities in audiophilia or should your desire for the ultimate audio and recording influence what you are choosing to listen to? I'll tell you that I've heard some recordings I'd never choose... much like I never wanted to see The Fifth Element more than once. I'm glad those days are over.

The article talks about live un-amplified music but I would go even further than that. A live rock concert is a totally different animal than a recording. The mix is different, the dynamics are *hugely* different, rock CDs are almost all mixed too hot, more appropriate for playback on the radio than on a capable system. So is accuracy *really* the goal for playback of this music? For me, no thanks.
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post #109 of 415 Old 02-22-2012, 12:27 PM
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Quote:
Originally Posted by penngray View Post

Not sure if you guys followed some of the recent Omnimic discussion but Nyal Mellor recently posted a great link that might help indentify what measurements (including standards) are meanful to this discussion.





Acedemic banter is great but simple bullet points like the following...just gives most accurate guidelines to start following.

Acoustic Measurement for stereo listening rooms white paper

Standards:
ETC of the L & R speakers should:
Be visually identical (with only minor deviations) from 0‐40ms
Be down to 10dB by 40ms to prevent breakdown of the precedence effect
Clearly show a decrease in the amplitude of energy over 040ms. The decay pattern may
or may not be continuous.
Show the consecutive peaks of the highest amplitude reflections viewed across the time
axis to be relatively smooth in pattern and density.
The criteria above should be considered in conjunction with the other stated targets for
reverberation time and L/R frequency response.

I would love to see Acoustic Measurement for Multichannel Listening Rooms!!

I can take measurements and see obvious problems, but what makes a room that sounds good into a room that sounds fantastic? I can measure decay, and see if it is uniform, but what should the target be, i.e. what is the "stated" target?

Jeff
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post #110 of 415 Old 02-22-2012, 09:28 PM
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IMO the targets for multichannel are not that far off the two channel standards I published. If you get close to the two channel standards then your room is one that should sound good. Maybe post your measurements against each section and we can get a thread going....

Master of Minions, Acoustic Frontiers. We specialize in the design and creation of high performance listening rooms, home theaters and project studios for discerning audio/video enthusiasts.
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Nyal, I'm reading through your white paper now. One thing (well the first of many things ) about ETC graphs I don't understand. If I look at figure B.1 This shows an ETC graph that is within spec. But I would expect to see an initial time delay gap followed by a reverberant field? (ie. something that sort of approximates the idealized attached image) Instead its a continuous decay.

Or is this not a graph for an RFZ-type room?

Thanks!
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Quote:
Originally Posted by kromkamp View Post

Nyal, I'm reading through your white paper now. One thing (well the first of many things ) about ETC graphs I don't understand. If I look at figure B.1 This shows an ETC graph that is within spec. But I would expect to see an initial time delay gap followed by a reverberant field? (ie. something that sort of approximates the idealized attached image) Instead its a continuous decay.

Or is this not a graph for an RFZ-type room?

Thanks!

that graph is reserved for large acoustical spaces. there is no appreciable reverberant sound-field within small acoustical spaces. no "reverb" and especially no Dc (critical-distance).

instead, in SAS, we focus on a (laterally arriving) exponentially decaying diffused sound-field (schroeder integral) after termination of ISD.
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Quote:
Originally Posted by Nyal Mellor View Post

IMO the targets for multichannel are not that far off the two channel standards I published. If you get close to the two channel standards then your room is one that should sound good. Maybe post your measurements against each section and we can get a thread going....

Nyal, fantastic. I recently finished reviewing the paper. I'll see if I can grab the time to make the required measurements of my room and we can see how it measures up. If you have any hints or suggestions on taking the measurements please post them. Also, should I take sweeps of my surround speakers too? That's something I haven't bothered to do yet at all, and I admit I'm not looking forward to having to spin my AVR around to make the connections!
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Quote:
Originally Posted by Nyal Mellor View Post

IMO the targets for multichannel are not that far off the two channel standards I published. If you get close to the two channel standards then your room is one that should sound good. Maybe post your measurements against each section and we can get a thread going....

I keep coming to the question of whether we are to be suppressing early reflections for surround channels? Dipoles had been used extensively for surrounds, but now there are rear surrounds and people are using anywhere from dipole to monopole in either position. And if there is one answer for cinema content with ambient sounds and occasional special effects (from the surrounds), what about multichannel music mixed with an in-the-band perspective where all channels are used equally for discrete sounds?

My question goes to deadening the room too much in treating the first reflection points for all seven channels ...

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Originally Posted by localhost127 View Post

instead, in SAS, we focus on a (laterally arriving) exponentially decaying diffused sound-field (schroeder integral) after termination of ISD.

So what should the ISD region look like on an ETC graph for a small room employing RFZ model?
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Originally Posted by kromkamp View Post

So what should the ISD region look like on an ETC graph for a small room employing RFZ model?

http://www.avsforum.com/avs-vb/showp...8&postcount=25
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Quote:
Originally Posted by kromkamp View Post

So what should the ISD region look like on an ETC graph for a small room employing RFZ model?

Nyal had a guide that he helped write for two channel and multi-channel spaces that showed ideal targets for a number of things, like decay, ETC, etc. I think it was a PDF? I lost track of that link, but I'm sure Nyal or Local can post it.
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Yes, but what does it look like? Like, does someone have a REW ETC graph they can share that shows a well-treated ITC gap and termination?

Eyerlon, my question is referring to that guide. I'm asking about this graph - where is the ITC gap (and termination) in this graph?
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Quote:
Originally Posted by Eyleron View Post

Nyal had a guide that he helped write for two channel and multi-channel spaces that showed ideal targets for a number of things, like decay, ETC, etc. I think it was a PDF? I lost track of that link, but I'm sure Nyal or Local can post it.

he asked specifically with respect to the RFZ acoustical model (of which there are strict specular criteria to adhere to).
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Quote:
Originally Posted by kromkamp View Post

Yes, but what does it look like?

it looks like a graph that meets the criteria listed in the post i just referenced, if you were to actually read it vs just scanning it for photos and graphs...

but, since you require something visual, here is an example:


likewise, here is an example of Ambechoic room model:


the density of the diffused-return is what should be noted with regards to the ambechoic model. it is primarily a surround-sound model. there is no 'termination' as with other acoustic models. while -30dB down after direct signal is effectively anechoic, it does not mean anechoic!

Quote:
Originally Posted by kromkamp View Post

Like, does someone have a REW ETC graph they can share that shows a well-treated ITC gap and termination?

http://www.gearslutz.com/board/studi...s-trigger.html


Quote:
Originally Posted by kromkamp View Post

Eyerlon, my question is referring to that guide. I'm asking about this graph - where is the ITC gap (and termination) in this graph?

there isn't one. he's not abiding by a specific acoustical model in that publication or example. there are strict criteria of which to adhere to with regards to the LEDE/RFZ acoustical models as part of this discussion.

...and you really may wish to read dragonfry's commentary in this thread as well as the ETC primer thread i linked to a few posts back. he is most certainly the authoritative subject regarding this topic from a knowledge and especially experience perspective.
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