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When acoustic is correct? Modular Synthesizers
Old 16th December 2010
  #1
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When acoustic is correct?

Hello

Ok, the answer is "when it sounds good"
But, I was curious to know when you guys consider a room "correct" acoustically speaking? Which range of tolerance?

I'm curious to see some response of some big studio, or even pro studio, not big, but used for making great records

Just to have some reference

I've done some searches, but I haven't found any measurements..
Seems audio engineer are quite jealous of their measurements.. I don't know many people who shares willingly their measurements
Old 17th December 2010
  #2
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I'd love to see some real data taken from really great sounding studios!

But your question depends on what the room is FOR. there are much more steadfast laws governing control room acoustics than recording room acoustics in general, and different criteria for judging success.

I don't have time to type all i know up right now but great question!
Old 17th December 2010
  #3
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Jens Eklund's Avatar
Quote:
Originally Posted by Victor_Stoian View Post
here's one that i found on the internet, if the frequency response is what you're after:
They sure picked the right scale and image ratio to make it look good ... heh

Also, as you all probably already know, the frequency response is only one of many important aspects of a good room. Decay times (waterfalls) and ETC (reflection behaviour) is as, or perhaps even more important. Also worth remembering is that a good room (RFZ, not dead) will never have a “flat” frequency response.
Old 17th December 2010
  #4
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Look here:

http://www.aes.org/technical/documents/AESTD1001.pdf

Look for the reverberation time graph and the frequency plot. This is for surround but the same data would be good for stereo. Plus an initial time delay gap of 20 ms in which the signal is 20 dB or even 20 dB lower than the direct signal.

I found an alternative classification of rooms here:

http://www.electroacoustics.co.uk/in...s/stdclass.htm

BTW I tried out how I exactly could measure the reverberation sound field alone and sent the author a mail about it but he did not answer up to now. But still this list has some relevance imo.

HTH Hannes
Old 17th December 2010
  #5
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Quote:
Originally Posted by Jens Eklund View Post
Also worth remembering is that a good room (RFZ, not dead) will never have a “flat” frequency response.
could you expand this sentence?
I know freq response isn't the only thing, but usually when you use trap to get a flatter response, they also absorb the decay.. in my room I'm under 200 ms and even under 100ms, I don't see dacay times as a problem, talking about treated rooms (which are the ones I'm talking about)
Old 17th December 2010
  #6
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Jens Eklund's Avatar
Quote:
Originally Posted by elan View Post
could you expand this sentence?
I know freq response isn't the only thing, but usually when you use trap to get a flatter response, they also absorb the decay.. in my room I'm under 200 ms and even under 100ms, I don't see dacay times as a problem, talking about treated rooms (which are the ones I'm talking about)
The "optimum" decay time depends on room size and what design philosophy is used. If the common LEDE or RFZ in specific, an often quoted figure is 300ms but this is naturally a rough figure for an average sized room. More important is that the decay times should be more or less the same thought the frequency range but derivation in the lowest range is more excepted since it’s not easy to achieve short decay times for the lowest modes. A slight decrease in the highest range is also common.

If you have decay times of only 200ms for your lowest modes, and still 100ms or more in the highs, assuming that the room is quite (or very) small, you can be happy. The problem with small rooms is that once you’re finished treating the first reflection surfaces, you have already absorbed to much energy so small rooms will always be more or less "dead".


EDIT:

Maybe I didn’t answer the question; A room with energy return to the sweet spot will never measure completely flat. If you kill all the reflections, then you might end up with a flat curve (provided that the speakers measure flat) but then you also end up with a very dead room and this is generally not the ideal listening environment.
Old 17th December 2010
  #7
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Northward's Avatar
Quote:
Originally Posted by Jens Eklund View Post
They sure picked the right scale and image ratio to make it look good ... heh
No, we didn't. This is a quick & dirty export to Excel from a 1/24th measurement of one of our rooms I did and posted on my Forum @ R/E/P, to show a real life response to a poster there.

There is nothing wrong with it, it's the untouched raw data from an export (hence the freq scale follows the 1/24th steps - didn't take the time to change it to round numbers).

The measurement was taken at sweet spot, impuls from flush mounted ATC 300A SL mains. It's a large room with a big analog console fitted (3.60 meters wide, 120cm deep).

I can make it look pretty if you want though. We have a nice pallet of colors and presentations to choose from.
Old 17th December 2010
  #8
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Jens Eklund's Avatar
Hey, sorry about that, but all too often I see graphs manipulated to look better. Do you have a better version of that graph (perhaps 50dB scale and better aspect ratio) and perhaps a waterfall and ETC?

Sincerely Jens Eklund


EDIT: Also, I didn’t say that the result was bad, a +/- 5dB in a large LEDE/RFZ room is good!
Old 17th December 2010
  #9
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SörenHjalmarsson's Avatar
 

It should also be mensioned that there are alot of different acousticians out there... that works with very different designs... that achieve very different percieved responses... that suits very different engineers... etc... (the LEDE and RFZ models are only 2 of these)

The final goal is of course to make great music, that the room should be a helpful tool that makes the translations easy and is a joy to work in. So although there are objectively defined goals for treatment, there will always also be subjective matters at play, since the room must always be made so as to suit the people that are to work within them (and people are different heh).

Great records and music have been made in all of these room models, even though the data measurement from them might look different (or at least the response will be).


Cheers,
Old 17th December 2010
  #10
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Quote:
Originally Posted by Jens Eklund View Post
The "optimum" decay time depends on room size and what design philosophy is used. If the common LEDE or RFZ in specific, an often quoted figure is 300ms but this is naturally a rough figure for an average sized room. More important is that the decay times should be more or less the same thought the frequency range but derivation in the lowest range is more excepted since it’s not easy to achieve short decay times for the lowest modes. A slight decrease in the highest range is also common.

If you have decay times of only 200ms for your lowest modes, and still 100ms or more in the highs, assuming that the room is quite (or very) small, you can be happy. The problem with small rooms is that once you’re finished treating the first reflection surfaces, you have already absorbed to much energy so small rooms will always be more or less "dead".


EDIT:

Maybe I didn’t answer the question; A room with energy return to the sweet spot will never measure completely flat. If you kill all the reflections, then you might end up with a flat curve (provided that the speakers measure flat) but then you also end up with a very dead room and this is generally not the ideal listening environment.

Thank you!
Old 17th December 2010
  #11
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Quote:
Originally Posted by Northward View Post
No, we didn't. This is a quick & dirty export to Excel from a 1/24th measurement of one of our rooms I did and posted on my Forum @ R/E/P, to show a real life response to a poster there.

There is nothing wrong with it, it's the untouched raw data from an export (hence the freq scale follows the 1/24th steps - didn't take the time to change it to round numbers).

The measurement was taken at sweet spot, impuls from flush mounted ATC 300A SL mains. It's a large room with a big analog console fitted (3.60 meters wide, 120cm deep).

I can make it look pretty if you want though. We have a nice pallet of colors and presentations to choose from.


Thank you for the measurements, do you also have the nearfield measurements? Possibly without any approximation
I'm more interested in nearfields measurements, cause I will never get a pair of big nor mid fields :P at least in that room

Honestly I don't understand why people approximate to 1/24 or 1/3, I never use this feature, only when I make measurement and I'm not sure if the overall is getting better
Old 17th December 2010
  #12
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Northward's Avatar
Quote:
Originally Posted by Jens Eklund View Post
Hey, sorry about that, but all too often I see graphs manipulated to look better. Do you have a better version of that graph (perhaps 50dB scale and better aspect ratio) and perhaps a waterfall and ETC?

Sincerely Jens Eklund


EDIT: Also, I didn’t say that the result was bad, a +/- 5dB in a large LEDE/RFZ room is good!
Hey, no problem I know what you mean. I see a lot of obviously manipulated data on forums.

I won't spill the beans on an ETC or waterfall, it says too much about FTB rooms. Our clients have full access to these data though. But Silvia or I will make another quick export of that measurement and post.

Yes, this response, while closer to +/-4dB than +/-5dB is pretty standard for a professional large room with a large console in it, which can sometimes be a pain to deal with. It's no surprise that a 1 ton+ metal behemoth impacts the response quite a bit. But we try and compensate for that in the design to start with.

We've noticed that rooms around +/-5dB (so within 10dB) are the best ones. When you go beyond that it's often the case that rooms become dull and lifeless. In short, they don't translate anymore. There's a fine line not to cross.

This room, anyone can visit anytime, it's our show-room. We're always happy to have people around come and visit us, grab a coffee and have good listen.
Old 17th December 2010
  #13
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Northward's Avatar
Quote:
Originally Posted by elan View Post
Thank you for the measurements, do you also have the nearfield measurements? Possibly without any approximation
I'm more interested in nearfields measurements, cause I will never get a pair of big nor mid fields :P at least in that room

Honestly I don't understand why people approximate to 1/24 or 1/3, I never use this feature, only when I make measurement and I'm not sure if the overall is getting better
No, I don't think we have the nearfield measurements. These rooms are designed so you can work 100% on mains and never have to turn your nearfields on. The way it should be

I'll have a look though, maybe we did it anyway. It was a while ago.

Our measurement system exports the data in 1/24th plots, so no choice here. We just leave it like that, it's really good already.
Old 17th December 2010
  #14
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Jens Eklund's Avatar
Quote:
Originally Posted by Northward View Post
There's a fine line not to cross.
+1

/Jens
Old 17th December 2010
  #15
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Northward's Avatar
Here it is. I reduced it to the measurement under 500Hz which is the most interesting part in these graphs. Major scale is 5dB, minor scale is 1dB.

Export Data used attached in a text file.

Hope this helps.
Attached Files
File Type: pdf GS 10-500.pdf (119.1 KB, 368 views) File Type: txt mdata24-NOR.txt (1.7 KB, 185 views)
Old 17th December 2010
  #16
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Jens Eklund's Avatar
Excellent results!
Old 17th December 2010
  #17
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Northward's Avatar
Quote:
Originally Posted by Jens Eklund View Post
Excellent results!
Thanks!

Better be though, expensive build.
Old 17th December 2010
  #18
Gear Addict
 

+1. Shows exceptional modal control and awareness in the design process of the speaker/room relationship. Very nice.
Old 17th December 2010
  #19
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Jens Eklund's Avatar
Quote:
Originally Posted by elan View Post
Honestly I don't understand why people approximate to 1/24 or 1/3, I never use this feature, only when I make measurement and I'm not sure if the overall is getting better
An unsmoothed frequency response chart can be very hard to read and especially if before treatment:

When acoustic is correct?-before.gif

When acoustic is correct?-after.gif

When acoustic is correct?-etc-after.gif

When acoustic is correct?-waterfall-after.gif


A 1/24 to 1/48 octave smoothing simply makes the curve readable without loosing too much detail. I do however agree that 1/3 octave or higher is quite useless in these cases.

Note that this room is very, very small; 7,5 m²! Luckily, the walls are quite lossy so there’s still some response below the normal cutoff frequency. Aslo, the before measurement was measured with Genelec 8250A and the result with RCF Mytho 6 (single channel).

Given the small size, the ETC is what it is. Good luck trying to get a nice Haas-kicker in 7,5mm². heh


EDIT: Also, the before measurement was without desk.
Old 17th December 2010
  #20
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Hannes_F's Avatar
 

Jens: Beautiful!
Old 17th December 2010
  #21
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Jens Eklund's Avatar
Quote:
Originally Posted by Hannes_F View Post
Jens: Beautiful!
Thanks! Very much looking forward to see some measurements of your space after diffuser treatment!

/Jens
Old 17th December 2010
  #22
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Hannes_F's Avatar
 

Quote:
Originally Posted by Jens Eklund View Post
Thanks! Very much looking forward to see some measurements of your space after diffuser treatment!

/Jens
Yes, looking forward to that, too!
Old 17th December 2010
  #23
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Northward's Avatar
Quote:
Originally Posted by Jeffrey Hedback View Post
+1. Shows exceptional modal control and awareness in the design process of the speaker/room relationship. Very nice.
Thank you. Managing big mains is indeed a whole different story. Having 2.4 to 3 meters between your measurement mic and the mains with a console in-between isn't like having 1 meter with nearfields and smaller workspace. Not that this is any easier. Just different sets of problems...

Much higher SPL are involved too, so the room needs to be able to swallow it all. But you know all that very well I see you also do mains.
Old 17th December 2010
  #24
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what do you think about these measurements?
Attached Thumbnails
When acoustic is correct?-krk.jpg   When acoustic is correct?-krkw.jpg  
Old 18th December 2010
  #25
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Quote:
Originally Posted by elan View Post
what do you think about these measurements?
I think they are pretty good!
Try to control the 70Hz mode. that should help a lot as well!

And maybe show the graphs, so its easier to see whats going on. Having the waterfall go to 300hz only should be enough, but maybe get some more detail under 100hz!
Old 18th December 2010
  #26
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man, one is a complete spectrum, the other is the waterfall, what graph do you mean?
Old 18th December 2010
  #27
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Magickman's Avatar
 

Quote:
Originally Posted by elan View Post
man, one is a complete spectrum, the other is the waterfall, what graph do you mean?
I think Nixoblivion added a comma that made that sentence confusing.

I think this probably reads better:

Present the graphs in a way that's easier to read by displaying the waterfall graph only through 300Hz, which will in turn display more detail under 100hz!

I think?

Of course, please shoot me if I'm wrong!
Old 18th December 2010
  #28
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Quote:
Originally Posted by Magickman View Post
I think Nixoblivion added a comma that made that sentence confusing.

I think this probably reads better:

Present the graphs in a way that's easier to read by displaying the waterfall graph only through 300Hz, which will in turn display more detail under 100hz!

I think?

Of course, please shoot me if I'm wrong!

ok, I'll wait for nixoblivion clarification, then I post the waterfall up to 300 hz if required (now I don't have them at hand), but I think it's already very comprehensible, what do you don't understand?

In general how do you think it is the result? (consider there's no approximation)

Thank you
Old 18th December 2010
  #29
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SörenHjalmarsson's Avatar
 

Quote:
Originally Posted by Magickman View Post
Of course, please shoot me if I'm wrong!
Seems a bit harsh. heh

Cool threads by the way Magick, hopefully i'll get the time to read them through thoroughly...


Cheers,
Old 18th December 2010
  #30
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Quote:
Originally Posted by SörenHjalmarsson View Post
Seems a bit harsh. heh
I wear kevlar, so, not all that harsh.
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