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Author Topic: Control room acoustics - the next level?  (Read 4965 times)

AndreasN

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Control room acoustics - the next level?
« on: July 09, 2010, 08:27:04 am »

Hi folks!

Am lusting for more information and it's starting to become difficult after covering the basics.

Been reading and learning lots about acoustics, especially during the last year. Been a literal order of magnitude change in the understanding and results! From diffuser building to treating control rooms using energy time curves, a clearly defined initial signal delay, some sort of loud ending to the ISD and a nice diffuse pseudoverb tail. Which may be the very first thing one learn in acoustics class in a real school, but it certainly ain't on most of the absorption fixated internet DIY sites.

So I've basically learned 80's acoustics. An era with big developments in measurement gear, Davis' LEDE concept and D'Antonios RFZ and commercial venture with diffusers. Have learned especially much from SynAudioCon papers (and the ever so amazingly helpful Mark S) and the Davis&Patronis book that condenses much of those papers into a few pages. The Cox&D'Antonio book is another tombstone in my acoustics journey. This is to give you a general idea of where I am in the learning process. As noted, I want more!

Like, is there any info on the FTB rooms? Or just some practical examples of real rooms with energy time curves and the means used to achieve the responses seen? Have found decent base level information, but not much practical examples. It's been a while since the papers I've read was written and the world may have moved on to new territories since then. Or perhaps this is basically it, and the rest is up to hands on experience and clever imagination?

Do realize that this is stepping well into the area of proprietary information for the pros on this forum. Am not expecting to get your secrets served on a plate! Though I hope it's possible to get some pointers for learning more, like book suggestions.




If it's also possible to discuss such things in here, it would be a real bonus!

We could use my room as an example if it works for the purpose. It's described with pics http://www.gearslutz.com/board/studio-building-acoustics/481 797-lede-room-haas-trigger.html here and the ETC looks like this:

http://www.gearslutz.com/board/attachments/studio-building-acoustics/166868d1270651761-lede-room-haas-trigger-haas2.png

The upper graph is a before picture, with lots of absorption and diffusion but no particular attention to ISD. The lower graph is the after with less clutter in the early reflections, a largeish specular Haas trigger/ISD termination and a more uniform structure to the diffuse pseudoverb tail.

This is the live end:
http://nordenmaster.no/2010/studio14.JPG

And this is the "dead" end:
http://nordenmaster.no/2010/studio10.JPG

Am planning to replace some of the rear wall diffusers and reflectors with 1D diffusers made of wood. The current 2D diffusers are plastic not so fantastic. This will send more energy back and concentrate the return to the horisontal plane, hopefully letting me get rid of the currently specularly dominated Haas trigger/ISD termination. The level of the rear wall return isn't loud enough without those reflectors, as seen in the first ETC graph above. The specular Haas trigger is doing miracles to the perception of the room! It's really amazing how much clearer and more enjoyable everything sounds now. Though I'm sure a diffuse ISD termination will be better!

Another aspect that I'm wondering about is the importance of the angle of the dominant reflections. Seems to me, after lots of reading on the topic of spatial cues, that the +-110' angle as seen in the ITU 5.1 setup is an ideal angle for the Haas trigger to give maximum sense of envelopment. Using lots of diffusers ensures that the first wave of room sound comes from a lot of angles. Some of them ideal, some less than ideal. I could try to focus the energy more, striving for more energy from the +-110' directions. Does this seem like a viable concern or a waste of time?

Does the overall level of the verb looks good? Do you wizards see a graph like that and think "way too short 'verb" or "way too much!" or..? Perhaps you see something else that's worth pointing out? Any critique is welcome! It's a modest DIY effort with limited funds, though I do of course strive to make it the best room possible. The treatment is entirely modular and it's fairly easy to move things around and try different setups.

The main thing I'm wondering about, though, is that I may be missing out on something very big in the overall picture. Perhaps the way of thinking about the room I describe above is way oldschool and there are better alternatives available. If so, even if it's impossible to describe without ruining your business, a quiet whisper of "keep searching!" would be very helpful. Smile


Please pardon the ramble! These are big subjects. Hope it's understandable.


Best regards,

Andreas Nordenstam

PS: for those who see the room measurement graph above and go "huh?" - have a look at this: http://www.santafevisions.com/csf/html/lectures/023_environm ent_IV.htm#Energytimeconsiderations
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Thomas Jouanjean

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Re: Control room acoustics - the next level?
« Reply #1 on: July 09, 2010, 11:00:07 am »

AndreasN wrote on Fri, 09 July 2010 07:27

Like, is there any info on the FTB rooms?


Only in my computer and Silvia's (the other engineer working with me). Lately Silvia has been slowly compiling all our data about FTB, but I don't see us having the time to write a book/article about it honestly... And it would feel a bit pretentious too.

But you're most welcome to drop by and have a coffee (or two!). I'll be happy to discuss whatever general questions you have about it.

AndreasN wrote on Fri, 09 July 2010 07:27

Or just some practical examples of real rooms with energy time curves and the means used to achieve the responses seen? Have found decent base level information, but not much practical examples. It's been a while since the papers I've read was written and the world may have moved on to new territories since then. Or perhaps this is basically it, and the rest is up to hands on experience and clever imagination?


You're going to have a real hard time finding data about "real rooms". They are either protected by an agreement or owners don't want to release them for whatever reasons (usually because it may fall into the hands of a couple idiotphiles).

[/rant on] Little bit off topic there, but: honestly the internet has created somekind of alternate reality in this field of Audio. People expect ruler flat graphs with perfect ETCs, perfect speakers. I see so many guys on forums completely disconnected from reality. And so many "gurus" with literally no real-life experience (and I mean "0") but 1000s of posts filled with technical non-sense that sounds good.

Recently, I read a claim on a forum from a guy within the industry that said some rooms could be within 1.5dB.

What do you do with statements like these?

Semi-anechoic  and anechoic rooms I've worked in or visited can't claim such a response. Unless you use DSP correction (*cough*) and even then I have serious doubts, no way you can reach that. 1 reflection and you're out. 1! And seeing how bass behaves and how difficult it is to fully contain 60Hz... And the sheer amount of materials needed...

So there is a big need at one point to put things in perspective again and cut the crap.[/rant off]

So, to come back to the subject - you'd be very surprised by the response of some very respected 'old' rooms for example. And by all means they are GREAT rooms. But what you would see would probably be quite a bit different from what you'd expect...

They are good because engineers do great mixes in them that translate.

So the question is, why do they translate and what is the REAL relevant information in the measurements? I can tell you they're not ruler flat, sometimes far from it. So what makes them great?

There's your homework Smile

Every time we travel to a new place we try and visit some of the studios in the area / region. Talk with engineers. Get them to give us their true opinions about it all. If we can we'll measure and try to see what type of correlation we have between what we see on the computer and what we are told by users.

ETC, ISD, Waterfalls... Sure they're important. But what makes a great room? I can tell you: 'flat' rooms are boring. If you can get a room to be within 10/12 dB you're there - and it's already hell difficult to get there (you wouldn't believe the damage a console or workstation desk does for example). The closer you get to *perfection* the more, in my experience, they become dull and lifeless.

Psychoacoustic territory is where things happen these days. A bass trap is a bass trap. How do we make it interesting for the Mix Engineer? Maybe there is something about the way the hearing process functions that we are overlooking?

One question I asked myself when I started was this: how do the speakers "see the room" and how does the engineer "perceives" it? How do we react to different types of environments / How does the listening environment influences our perception of sound?

Here's your pointer.


AndreasN wrote on Fri, 09 July 2010 07:27


Am planning to replace some of the rear wall diffusers and reflectors with 1D diffusers made of wood. The current 2D diffusers are plastic not so fantastic.


They never are. Build in wood!

AndreasN wrote on Fri, 09 July 2010 07:27

 This will send more energy back and concentrate the return to the horisontal plane, hopefully letting me get rid of the currently specularly dominated Haas trigger/ISD termination. The level of the rear wall return isn't loud enough without those reflectors, as seen in the first ETC graph above. The specular Haas trigger is doing miracles to the perception of the room! It's really amazing how much clearer and more enjoyable everything sounds now. Though I'm sure a diffuse ISD termination will be better!


Stick to the 2D ones if you can.

AndreasN wrote on Fri, 09 July 2010 07:27


Does the overall level of the verb looks good? Do you wizards see a graph like that and think "way too short 'verb" or "way too much!" or..? Perhaps you see something else that's worth pointing out? Any critique is welcome! It's a modest DIY effort with limited funds, though I do of course strive to make it the best room possible. The treatment is entirely modular and it's fairly easy to move things around and try different setups.


I don't know of any wizards here. I know a couple engineers. There are no sacrifices of chicken or related animals in the design process Very Happy

It's more the pictures than the graphs that got me thinking about your overall geometry + ceiling. Did you work on one and if so, to achieve what goals?
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Thomas Jouanjean
Northward Acoustics - Engineering and Designs
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AndreasN

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Re: Control room acoustics - the next level?
« Reply #2 on: July 11, 2010, 02:00:59 pm »

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00

Only in my computer and Silvia's (the other engineer working with me). Lately Silvia has been slowly compiling all our data about FTB, but I don't see us having the time to write a book/article about it honestly... And it would feel a bit pretentious too.


Didn't knew it was such a personal/special concept! Explains the lack of info in the literature.

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00

But you're most welcome to drop by and have a coffee (or two!). I'll be happy to discuss whatever general questions you have about it.


Thanks for the kind offer! Will sure do so if I get around to your part of the world.

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00

So there is a big need at one point to put things in perspective again and cut the crap.[/rant off]


It's a very strange situation. Haven't seen such large disparity between the DIY crowd and the pros in any other field related to audio. Must, somewhat shamefully admit, that I've gone through it all. Have hopefully managed to shed off the worst ideas by now. But I don't know..

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00

ETC, ISD, Waterfalls... Sure they're important. But what makes a great room? I can tell you: 'flat' rooms are boring. If you can get a room to be within 10/12 dB you're there - and it's already hell difficult to get there (you wouldn't believe the damage a console or workstation desk does for example). The closer you get to *perfection* the more, in my experience, they become dull and lifeless.


The ideal of a flat frequency response presumes, as you noted, zero reflections. Anechoic! A strange ideal for a listening room.

Using something like this illustration from RPG as an ideal makes a lot more sense:

http://www.gearslutz.com/board/attachments/bass-traps-acoustic-panels-foam-etc/161177d1267709041-lots-bass-traps-dulling-highs-partially-reflective-traps-good_room.png

Do you feel this is a good enough starting point to use as a *very broad* general guideline for the DIY crowd? I know it's a slippery slope to give such very general advice, though it's surely better than espousing a flat frequency response..?

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00

Maybe there is something about the way the hearing process functions that we are overlooking?


Such ideas have been bugging me lately. This snippet from Richard Heysers work literally blew my mind when I first encountered it:

"The frequency description of a signal and the time description of that signal are tangled up with each other in a very fundamental way. The parameter that we call "time" and the parameter that we call "frequency" are not independent of each other. And no amount of Band-Aid engineering with running transforms or things called instantaneous frequency is going to change that fact.

Yet in subjective audio, we know darn well there is the property of pitch which is frequency-like, and that pitch can change with relative time. So if we want to apply the existing high power mathematics of time domain and frequency domain to what we hear, we seem to need a joint frequency-time description. Ultimately, when we try that trick, we run into the fundamental relationship between time time and frequency, a relationship which we ourselves created from the definition we gave to these things.

But rather than blame ourselves, we choose to imagine that nature has intervened and somehow, magically, put a limit on the precision with which a codetermination of these parameters can be established. We even gave that a name, the uncertainty principle.

What leads us to this rather strange action is a very real need for some kind of math that has a time-like and a frequency-like (and a space-like, and so on) set of properties which can all be used in the same description. Up to now our tool box of math relationship has only contained the parameters related by Fourier transformation. So we've been stuck."

A very small snippes from the Time Domain Spectroscopy anthology by Richard C. Heyser: http://www.aes.org/publications/anthologies/

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00


One question I asked myself when I started was this: how do the speakers "see the room" and how does the engineer "perceives" it? How do we react to different types of environments / How does the listening environment influences our perception of sound?

Here's your pointer.


Thanks! Beyond the usual "hardcore" psychoacoustics I've found little relevant info beyond the work of Toole et al at Harman. Any other literature recommendations in the field?


Thomas Jouanjean wrote on Fri, 09 July 2010 17:00

Stick to the 2D ones if you can.


Interesting! I love 2D's and have no problem generating/building them. Prefer the looks too. Though it makes me wonder, why wouldn't it be beneficial to try to keep most of the energy in the lateral plane?

AndreasN wrote on Fri, 09 July 2010 07:27

I don't know of any wizards here. I know a couple engineers. There are no sacrifices of chicken or related animals in the design process Very Happy


Not even a great Belgian beer? Smile

AndreasN wrote on Fri, 09 July 2010 07:27

It's more the pictures than the graphs that got me thinking about your overall geometry + ceiling. Did you work on one and if so, to achieve what goals?


The room is rental, so the structure is what it is. The ceiling treatment is a bit overkill, mostly to help get the low end under control. It's a great spot for porous absorption at 1/4'th the room length! Though I'm way open for new ideas. As noted, moving things around is quite easy. If you have a gut feeling of some other potentially better idea(s), please share! Can implement, measure and post the results.


Thanks a lot for your thoughts and ideas! It have already helped quite a lot. Smile


Cheers,

Andreas Nordenstam
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Thomas Jouanjean

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Re: Control room acoustics - the next level?
« Reply #3 on: July 24, 2010, 06:52:10 am »

In the end, it's all about understanding / seeing the potential of the space dealt with, having a good global vision of it - which also implies knowing when to say stop.

When designing a commercial facility, there's always a point where the extra marginal
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Thomas Jouanjean
Northward Acoustics - Engineering and Designs
http://www.northwardacoustics.com
http://www.facebook.com/pages/Northward-Acoustics/1062876633 71

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AndreasN

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Re: Control room acoustics - the next level?
« Reply #4 on: September 03, 2010, 11:37:02 am »

Hello!

The lack of instant reply from my part doesn't mean I've forgotten your replies. They where pretty cryptic, but I do think they set me off in a certain directions that may be beneficial. Smile

Thomas Jouanjean wrote on Fri, 09 July 2010 17:00


It's more the pictures than the graphs that got me thinking about your overall geometry + ceiling. Did you work on one and if so, to achieve what goals?


As I look at it now, the ceiling looks like a tuned trap destined to absorb more in certain frequency ranges than others. Does it seem right to you?

Am thinking things over, once again, and will have another round of moving treatment and re-adjusting things in a couple of months time. Will hopefully have gotten time to make a few wood diffusers by that time too. Looking forward to room treatment V3! Smile


Cheers,

Andreas
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