or Connect
AVS › AVS Forum › Audio › Receivers, Amps, and Processors › The Audyssey Pro Installer Kit Thread (FAQ in post #1)
New Posts  All Forums:Forum Nav:

The Audyssey Pro Installer Kit Thread (FAQ in post #1) - Page 8

post #211 of 5250
Quote:
Originally Posted by LarryChanin View Post

Hi Guys,

Returning to the thrust of Fitz's remarks the reason for the Audyssey high frequency rolloff is to account for differences in the acoustic environment between the recording studio and the typical small listening room. It really doesn't have anything to do with the "X-Curve".



Larry

Larry - I may have overblown the connection to the X-curve. I think the more complex version of my meaning fits with yours. I believe the X-curve and the HF rolloff in Audyssey are both derived from largely the same underlying property of acoustics. That is the difference in response between direct, close in, so-called "near field" measurements vs. those in the more reverberant "far field". I think the previously cited papers on the X-curve make this underlying cause clear.

Obviously, the X-curve itself was developed and is intended for large auditoriums. But, the same measurement issue occurs to a significantly lesser degree with sound in home listening rooms when room reflections come into play. We see this in the 3 standard rolloff curves built into Pro. It is only #3 that is intended for large spaces and tends to be more like the X-curve with much more rolloff. #'s 1 and 2 are Audyssey's adaptations of the underlying idea, not of the X-curve itself, based on their own research for typical smaller home theaters. Chris's explanations also including acoustic treatments in mixing/mastering studios may also be a factor, although studios do vary. But, the distance from the speakers is itself sufficient to cause the underlying HF measurement phenomenon based on the ratio of direct to reflected sound.

In any case, the key is how much room reverberation is involved with the mike to speaker measurement positions. "Near field" and "far field" are kind of red herrings. Sorry I introduced them, but acousticians talk in those terms all the time. They are merely proxies for the amount of direct vs. reflected sound. And, what Audyssey is all about is correcting for adverse effects of those room reverberations.

Flat HF response would be fine for typical computer/workstation speakers. But, in real rooms under typical listening conditions, an adjustment is needed to the measured HF response for the effect of the room. The Audyssey rolloff of the target curve gives us an approximation of that. But, for geezers like me without much hearing above 15K, I cannot say that the effect is profound. More important may be the very slight rolloff in the target curve below 15K. In any case, I very much like what Audyssey has done to the resulting sound using Pro curve #1.
post #212 of 5250
Quote:
Originally Posted by LarryChanin View Post

Returning to the thrust of Fitz's remarks the reason for the Audyssey high frequency rolloff is to account for differences in the acoustic environment between the recording studio and the typical small listening room. It really doesn't have anything to do with the "X-Curve".

I suppose I was unclear. I was using far-field in the context of theater equalization -- the nominal purview of the 202M et. al. The Allen article calls the space from 0-15 feet near-field and 40 feet far-field.
post #213 of 5250
Quote:
Originally Posted by BobL View Post

If we are trying to recreate the acoustical space of recordings we must first determine where the recording took place. Most movies the final mix is not done in a recording studio but in a dubbing stage. This is a medium sized theater with a mixing console in the middle. It is considered large room acoustics and would definitely be far field.

High frequencies are frequently boosted in this environment because high frequencies dimminish quicker than low frequencies. When you transfer a soundtrack to a DVD/B-ray this will make the material sound bright if not compensate for in the transfer. It is the reason for many THX/theater/cinimea modes in processors.

For reference most home theaters will show a natural roll off at ~6-8 khz depending on the distance if the seating. This shouldn't be compensated for with EQ as the tonal changes make it vey noticeable. Theaters being a larger space roll off at ~2khz and is routinely compensated for with EQ. I'll explain further.

If we back up a bit and look at how loudspeakers are measured at typically 1-2 meters from the speaker. This measurement is the reference for that speaker. If we listen 10-20 feet from that speaker we will still be able to tell the timbre of the speaker. Just like if you were across the room from a friend with a stuffy nose you can tell his voice sounds different than normal. Compensating for this small amount of roll off in small rooms can often make the source sound un-natural.

In a large room sitting 50-100 feet or more from the screen with roll off that starts at a lower frequency and is steeper we need to have some compensation so dialogue doesn't sound distant and lose the illusion of dialogue taking place as if we were in the room.

The good thing about dubbing stages is they are acoustically similar as they have standards. Also there aren't that many of them (~20) so it is easier to recreate their acoustical properties.

Music and TV are a whole different animal. Most of these are recorded in recording studios which vary quite a bit acoustically. Some are very near field with speaker (monitors) sitting on the mixing console. Other have baffle mounted speakers (like in wall speakers) which are 10-20 feet from the mixing console. Most have acoustical treatments in the room but there is no standard and the room acoustics differ greatly. As the previous poster mentioned the high frequencies may be boosted because the room has lots of absorption. Unless you know the exact recording studio a piece was mixed in, it is highly unlikely you will recreate the acoustical space for music or TV.

Large room vs small room each has its own set of acoustical issues. Large rooms deal with much more reverberration while small rooms have standing waves problems. Where is the cut off between large and small. Well opinion vary but IMHO once your space is bigger than 50 ft x 50 ft you are dealing with large room acoustics. I don't think anyone would argue that 100 ft x 100ft is a large room.

Defining near field depends on the person but the recording studio with monitors on the console I think everyone can agree is near field. From a technical standpoint nearfield is less than 2 wavelengths, usually referred to in other areas of electronics. Far field is greater than 2 wavelengths. For audio this would be a tough definition because wavelengths change with frequency. A 20hz wave is greater than 50ft and 20khz is less than an inch. I'd say nearfield is less than 2 meters but there is no definition and not all recording studios would be considered near field.

Hi Bob,

Thanks for the well-written posting.

Your posting gives the impression that you have some hands-on experience with regard to an aspect of the recording industry. Would you mind telling us whether you are an enthusiast or professional?

Thanks very much.

Larry
post #214 of 5250
Quote:
Originally Posted by bodosom View Post

I suppose I was unclear. I was using far-field in the context of theater equalization -- the nominal purview of the 202M et. al. The Allen article calls the space from 0-15 feet near-field and 40 feet far-field.

Hi,

Thanks for your response, but I have to admit that I'm confused by your remarks quoted above.

Here's your previous comment:

Quote:
Originally Posted by bodosom View Post

I don't listen in the far-field. I suspect few people do at home.

I think it fair to say that Fitz's points had to do with listening in a reverberant field at home. I don't think that Allen's remarks about what is far-field in a commercial theater has any relevance to his points. Regardless a raw distance measure is unlikely to accurately determine whether the listener is seated in a reverberant field. The size and reverberation time of the listening room, the directivity of the speakers, in addition to the distance from the speakers are all factors in making this determination.

Larry
post #215 of 5250
Quote:
Originally Posted by fitzcaraldo215 View Post

Au contraire. Most home listening is done in the far field. Unless your speakers are about 1 meter away, it is farfield listening where room reflections start to become significant. That is the meaning of "far field."

I was using near/far in the context of the "X-curve".

Quote:


But with music, you have a live sound reference in live concerts. With movies, I really do not know exactly what Meryl Streep's voice sounds like.

Sure but that's not the point. Dubbing stages have standards that govern their room response (despite Dolby's measurements to the contrary). The mixing environment for other content is up to the whim of owner/producer/engineer/mixer (e.g. Frank Filipetti).

Quote:


No, I think there is broad professional consensus that bass should be measurably flat in your room (at reference level).

If you have some references for that I'd appreciate seeing them.

Quote:


I have several friends with Anthem D2V's with ARC. It provides very similar results. We once did a listening session of a D2V (ARC calibrated) vs. an Integra DTC 9.8 (Pro calibrated MultEQ XT) side by side in the same room. There were no obvious differences in the sound; they were virtually indistinguishable with Mch SACD - hats off to Integra for matching the sound of a > 4X more expensive unit!

Heh heh ... funny story ... this conversation started when I referenced Sean Olive's paper which just happen to compare ARC1 to the Audyssey Sound Equalizer. It's felt they found significant differences but the systems are anonymous so it's somewhat speculative.
post #216 of 5250
Quote:
Originally Posted by LarryChanin View Post

Thanks for your response, but I have to admit that I'm confused by your remarks quoted above.

In the context of 202M far-field is a theatrical space. The Allen article about the "X-curve" refers to near-field monitors at 15 feet and far-field at 40 feet. I was suggesting that most home theaters have speakers closer to 15 feet than 40 feet (or are much smaller than a SMPTE small theater). Not that that inhibits Audyssey from offering that choice on the HF side of the curve.

The conclusion that ambiguous terms like near/far field are unhelpful is sound .
post #217 of 5250
Hi Larry,

Enthusiast or Professional? Both!

I have worked in recording studios to help my friend which owns a couple of them. I currently work as a custom integrator where we mainly design home theaters with an occasional small or home recording studio. I have an engineering background with a focus on acoustics. I have had many trainings on acoustics and HT, including THX, HAA, Dolby Labs, other dubbing stages as well as many other HT education opportunites.

As an enthusiast I like to design and build speakers and play keyboards. Of course without MIDI I'd really stink

Bob
post #218 of 5250
I'm terrible on piano without those big pedals you alternately pump under the keyboard.
post #219 of 5250
Quote:
Originally Posted by fitzcaraldo215 View Post

Larry - I may have overblown the connection to the X-curve. I think the more complex version of my meaning fits with yours. I believe the X-curve and the HF rolloff in Audyssey are both derived from largely the same underlying property of acoustics. That is the difference in response between direct, close in, so-called "near field" measurements vs. those in the more reverberant "far field". I think the previously cited papers on the X-curve make this underlying cause clear.

Obviously, the X-curve itself was developed and is intended for large auditoriums. But, the same measurement issue occurs to a significantly lesser degree with sound in home listening rooms when room reflections come into play. We see this in the 3 standard rolloff curves built into Pro. It is only #3 that is intended for large spaces and tends to be more like the X-curve with much more rolloff. #'s 1 and 2 are Audyssey's adaptations of the underlying idea, not of the X-curve itself, based on their own research for typical smaller home theaters. Chris's explanations also including acoustic treatments in mixing/mastering studios may also be a factor, although studios do vary. But, the distance from the speakers is itself sufficient to cause the underlying HF measurement phenomenon based on the ratio of direct to reflected sound.

In any case, the key is how much room reverberation is involved with the mike to speaker measurement positions. "Near field" and "far field" are kind of red herrings. Sorry I introduced them, but acousticians talk in those terms all the time. They are merely proxies for the amount of direct vs. reflected sound. And, what Audyssey is all about is correcting for adverse effects of those room reverberations.

Flat HF response would be fine for typical computer/workstation speakers. But, in real rooms under typical listening conditions, an adjustment is needed to the measured HF response for the effect of the room. The Audyssey rolloff of the target curve gives us an approximation of that. But, for geezers like me without much hearing above 15K, I cannot say that the effect is profound. More important may be the very slight rolloff in the target curve below 15K. In any case, I very much like what Audyssey has done to the resulting sound using Pro curve #1.

Hi Fitz,

Yes, I think we are almost saying the same thing. I agree that the difference of the ratio of direct to reverberant sound fields between the mixing and home listening environments is an element common to the Audyssey roll-offs and aspects of the X-Curve and the SMPTE 202M modern variant.

However, if I understand correctly these theater equalization curves also accommodate other issues, such as the limitations of equipment used in commercial theaters, which of course have nothing to do with the differences in reverberant sound fields. For example, these curves roll-off the bass. Allen suggests this is done to protect theater speakers from overload and avoid distortion. Allen also suggests that part of the rational for the high frequency roll-off in the curve that later became the X-Curve was to deal with distortions in the high frequencies. In other words it was done in part to reduce noise as these speakers reached their operating limits.

Audyssey is not concerned with these equipment limitation related aspects justifying low and high frequency roll-offs and as we know is flat in the bass region.

Larry
post #220 of 5250
Quote:
Originally Posted by BobL View Post

Hi Larry,

Enthusiast or Professional? Both!

I have worked in recording studios to help my friend which owns a couple of them. I currently work as a custom integrator where we mainly design home theaters with an occasional small or home recording studio. I have an engineering background with a focus on acoustics. I have had many trainings on acoustics and HT, including THX, HAA, Dolby Labs, other dubbing stages as well as many other HT education opportunites.

As an enthusiast I like to design and build speakers and play keyboards. Of course without MIDI I'd really stink

Bob

Hi Bob,

Thanks for the response.

Having folks like yourself participating in these forums, with both theoretical and practical experience, really elevates the quality of these discussions.

Larry
post #221 of 5250
Quote:
Originally Posted by bodosom View Post

If you have some references for that I'd appreciate seeing them.

That's like asking for proof if the sun is coming up tomorrow like it did the last 4 billion years.
See papers by Harman, K+H, Geddes, Genelec or University of Essex.
Or did I just misunderstand your point?
post #222 of 5250
Quote:
Originally Posted by LarryChanin View Post

Audyssey is not concerned with these equipment limitation related aspects justifying low and high frequency roll-offs and as we know is flat in the bass region.

Indeed. My original question was about simulating the tilt found in Harman systems given the significant preference for it. It seems to me that far too many people complain about "thin" bass post-Audyssey and want to turn up their sub(s). I used to think this was simply an adaptation but perhaps it's a deeper preference.
post #223 of 5250
Quote:
Originally Posted by markus767 View Post

Or did I just misunderstand your point?

It's hard to say. Perhaps I didn't have one. I was thinking that 202M has broad professional acceptance and calls for roll-off starting at 63Hz. Or maybe it was Frank Filipetti talking about his studio tuned for hip-hop.
post #224 of 5250
Quote:
Originally Posted by bodosom View Post

Indeed. My original question was about simulating the tilt found in Harman systems given the significant preference for it. It seems to me that far too many people complain about "thin" bass post-Audyssey and want to turn up their sub(s). I used to think this was simply an adaptation but perhaps it's a deeper preference.

Hi,

In the early days Dynamic EQ wasn't available to restore perceptual flatness. So many folks in the past complained about MultEQ having thin bass after EQing flat AND listening below reference level. Personally I believe today with Dynamic EQ enabled most complaints about thin bass is probably due to listeners simply being used to boomy bass.

Its true, due to the way human hearing sensitivity works, that when listening below reference a boost in the bass is usually preferred by listeners.

Larry
post #225 of 5250
Quote:
Originally Posted by fitzcaraldo215 View Post

[...] I think there is broad professional consensus that bass should be measurably flat in your room (at reference level). It sounds more like live music to me that way, as well.

Quote:
Originally Posted by bodosom View Post

If you have some references for that I'd appreciate seeing them.

Quote:
Originally Posted by markus767 View Post

That's like asking for proof if the sun is coming up tomorrow like it did the last 4 billion years.
See papers by Harman, K+H, Geddes, Genelec or University of Essex.
Or did I just misunderstand your point?

Quote:
Originally Posted by bodosom View Post

It's hard to say. Perhaps I didn't have one. I was thinking that 202M has broad professional acceptance and calls for roll-off starting at 63Hz.

Hi,

Pulling things back into context, Fitz was discussing EQing for flat bass at HOME and at reference level.

The roll-off of the 202M curve has nothing to do with this. As I alluded to earlier it was probably done to protect commercial theater speakers from overloading or distorting when approaching their operating design limits for frequency.

Larry
post #226 of 5250
Quote:
Originally Posted by LarryChanin View Post

Hi,

In the early days Dynamic EQ wasn't available to restore perceptual flatness. So many folks in the past complained about MultEQ having thin bass after EQing flat AND listening below reference level. Personally I believe today with Dynamic EQ enabled most complaints about thin bass is probably due to listeners simply being used to boomy bass.

Its true, due to the way human hearing sensitivity works, that when listening below reference a boost in the bass is usually preferred by listeners.

Larry

Larry - I was just about to say exactlty the same thing. Right on!
post #227 of 5250
Quote:
Originally Posted by SoundofMind View Post

^Be my guest.

Thanks
post #228 of 5250
Quote:
Originally Posted by LarryChanin View Post

Pulling things back into context, Fitz was discussing EQing for flat bass at HOME and at reference level.

Sure and I still wouldn't mind some references that support (and possibly clarify) the position. I've heard casual remarks that suggest various things.
post #229 of 5250
I don't suppose anyone has had the Audyssey training?
post #230 of 5250
What training?
post #231 of 5250
Quote:
Originally Posted by pepar View Post

What training?

Guess that's a no for Jeff.

Quote:


Support from Audyssey

Audyssey cares about the success of our Registered Installers. That is why we provide resources, training, and marketing to our installers. Join the Audyssey Installer Program for instant access to:
....
  • Free training at CEDIA Expo and online webinars
post #232 of 5250
Quote:
Originally Posted by bodosom View Post

Sure and I still wouldn't mind some references that support (and possibly clarify) the position.

Hi,

No insult is intended, but I find it difficult to take your posting seriously. I've read a number of your postings and you seem to be a rather knownable guy. Surely for such a basic issue as spectral balance you must have already read that departures from a flat frequency response introduces timbre changes that colors the accuracy of sound of recordings. It really reduces to common sense. If your playback system emphasizes certain frequencies or attenuates others you really can't expect a recording to sound accurate.

Quote:


I've heard casual remarks that suggest various things.

So? Folks have different personal preferences. That's where tone controls come in, but twirling those tone control dials doesn't make the playback more accurate just because someone prefers the sound it produces.

As was mentioned earlier folks usually prefer boosting the bass (or tilting the response up in the bass) when listening below reference (the level the recording was monitored in the studio), but that doesn't mean that a flat response isn't the most accurate presentation of the recording when listening at reference level.

Larry
post #233 of 5250
Are you seriously still discussing X curve? It should be obvious by now that any curve based on steady state measurements ignores a lot of factors (number, level, angle, spectrum, delay of reflections) that are crucial to translation of mixes from one acoustic space to another. What worked for cinema speakers from 40 years ago doesn't work for modern speakers and rooms any more. That's the sole reason why there is ANSI/SMPTE 222M. This is what Dolby's surround mixing manual says:



They talk about preference while talking about a standard - this calls for new and better standards.
post #234 of 5250
I mostly prefer midrange compensation off however the occasional soundtrack can get a bit harsh at reference levels- mostly older stuff and non HD codec films
My room is overly damped/treated (my preference) so could see myself preferring it on in non treated room
post #235 of 5250
Quote:
Originally Posted by GPBURNS View Post

I mostly prefer midrange compensation off however the occasional soundtrack can get a bit harsh at reference levels- mostly older stuff and non HD codec films
My room is overly damped/treated (my preference) so could see myself preferring it on in non treated room

I use it for my non electrostatic surrounds. I turn mid comp off and then do a 2 db trough at the cross over frequency for my surrounds and rears.

For my Martin Logan l/c/r mid comp is off.

Not sure how important it is for the surrounds in my room.
post #236 of 5250
Quote:
Originally Posted by LarryChanin View Post

Surely for such a basic issue as spectral balance you must have already read that departures from a flat frequency response introduces timbre changes that colors the accuracy of sound of recordings.

Perhaps we're talking about different things. E.g. none of the Audyssey REFERENCE curves are flat (at least not with my AVR). I suspect this is representative of RC products.
post #237 of 5250
Quote:
Originally Posted by BobL View Post

Music and TV are a whole different animal. Most of these are recorded in recording studios which vary quite a bit acoustically. Some are very near field with speaker (monitors) sitting on the mixing console.

Bob... as a point of clarification regarding TV, that isn't really the case. Since the move to 5.1, most TV (talking about networks, cablers like HBO, etc...) has been mixed in smaller or mid sized dubbing stages, tuned accordingly for the intended purpose.

The "speakers on the meter bridge" was common back in the 80's and 90's... however, mixing near filed in 5.1 is really difficult because the sweet spot is so small.
post #238 of 5250
FilmMixer,

Thanks! That's good to know most network TV is trying to adhere to some standards now. I still see some smaller recording studios around here with "speakers on the meter bridge" but they aren't 5.1, only for music.

Bob
post #239 of 5250
Quote:
Originally Posted by bodosom View Post

Perhaps we're talking about different things. E.g. none of the Audyssey REFERENCE curves are flat (at least not with my AVR). I suspect this is representative of RC products.

Hi,

I feel that we have more than adequately explained the reason for the Audyssey high frequency roll-off is to adjust for differences between the mixing and listening acoustic environment with regard to the ratio of direct to reverberant soundfields. In the bass region the soundfield is closer to omnidirectional and a roll-off is not needed to restore perceptual spectral balance.

If the acoustic conditions for listeners at home matched the mixing studio a flat response for the entire spectrum would be appropriate to ensure accuracy.

Could a scientist such as Dr. Olive with a competing room correction approach conduct subjective listening tests in which listeners prefer a different target curve, say one that tilts up in the bass? Sure, but I maintain that a flat target curve when listening at reference would likely score best by trained listeners when ranking accuracy.

Interestingly Dr. Olive conducted comprehensive tests of competing speakers with trained listeners and found that the speakers that they preferred sounded flat and that it turned out that these same speakers had the flattest frequency response when measured under anechoic conditions. In other words the trained listeners were able to hear a flat frequency response even through the coloring effects of the room which adversely impacts the speaker's spectral balance.

From Toole:

Quote:


As part of the first tests, listeners were required to “draw” (using sliders on a computer screen) a frequency response, describing what they thought they heard in terms of spectral balance. This is a task that obviously could not be asked of average listeners, but these listeners had been through a training program (Olive, 1994, 2001) and were able to estimate the frequencies at which audible excesses and deficiencies occurred. When these data were compiled, the results indicated that all of the highly-rated loudspeakers had been judged to have very flat curves.[...]

In these experiments, trained listeners were able to draw curves of spectral trends—crude frequency responses—describing what they heard in the listening room. All of the high-scoring loudspeakers were described as having flattish spectra (above the transition frequency), a trend that matches the flattish on-axis/listening window curves for all of the corresponding anechoic measurements.

Larry
post #240 of 5250
Quote:
Originally Posted by LarryChanin View Post
I feel that we have more than adequately explained the reason for the Audyssey high frequency roll-off is to adjust for differences between the mixing and listening acoustic environment with regard to the ratio of direct to reverberant soundfields.
Sure. Clearly you have strong beliefs about this and since this is specific thread I'll close with these:

1) Few regularly listens at reference level so setting that as a contraint isn't helpful for most of us. But let's say it's 10% of the time. Then 90% of the time flat response is wrong.
2) Reference levels (and EQ) for non-standard mixes are generally unknown in any case.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Receivers, Amps, and Processors
AVS › AVS Forum › Audio › Receivers, Amps, and Processors › The Audyssey Pro Installer Kit Thread (FAQ in post #1)