John Sayers' Recording Studio Design Forum Archive

Hey all,

Here are some pictures and REW analysis.

- The front/angled ceiling isn't installed / treated yet (that may explain the gaps @132Hz and 209Hz) .
- The side walls will have reflective wall units.

What do you think about the RT60 measurement?
Will I need some special/tuned low frequency treatment? (like membrane absorbers on the back wall)
Any recommendation so far?

Room dimention:
Length = 500.0 cm
Width = 472.0 cm
Height = 400.0 cm


MDAT link:
https://www.dropbox.com/s/cdorp50sqw3er ... .mdat?dl=0

Here are some pictures and REW analysis.

Before I answer your questions, my first question would be: What sub and speakers did you use??? It's pretty amazing that the sub manages to put out over 70 dBC down at 10 Hz., and the roll-off seems to be linear at barely 6dB per octave, from 160 Hz down.... That does seem rather unusual.... and since you apparently are putting out a very large amount of sub-sonic energy, an octave below the bottom end of the audible range, I'm wondering how you isolated that room! What MSM frequency would you use for that?

I'm also wondering why the HIGH end rolls off at a rather steep 18 dB per octave above 2.5 kHz.... I'm not aware of any reference monitors that have such huge low end, way down into the sub-sonics, yet no high end at all. That's very strange.

I guess what I'm saying is: Are you CERTAIN you set up and calibrated REW correctly, and that you ran the tests correctly? Did you do it like this? http://www.johnlsayers.com/phpBB2/viewt ... =3&t=21122 .

That's a very strange measurement. What speakers did you use (make and model)? What mic did you use (make and model)? Where did you have the speakers set up (location in the room)? Where did you have the mic set up (location in the room)?


- Stuart -

Good point!
I should have mentionned that this measure has been done while I was testing the bass driver of the DIY speaker we are building for the studio.
That explains the high frequency roll off


Here's an other measurement we did some times ago with a real pair of speakers:
https://www.dropbox.com/s/a7fzyn0tcojwc ... .mdat?dl=0

I used a miniDSP UMIK-1 calibrated USB measurement microphone.

I should have mentionned that this measure has been done while I was testing the bass driver of the DIY speaker we are building for the studio

That explains the hig end, sort of, but I'm still suspicious: What bass driver goes down to 10 Hz at 70 dBC? And has a roll-off of less than 6 db/octave? Also, if that is only a sub that you used for that test, then how come it goes up to 2.5 kHz?

Something just doesn't sound right here. In order to get down to 10 Hz smoothly, you would need a massively huge driver, and a massively powerful amp to drive it to those levels, yet there's no evidence of the room "pumping" or "breathing" below the lowest mode...

Sorry to harp on this point, but I'm not convinced that the data is valid.

Here's an other measurement we did some times ago with a real pair of speakers:

That data is more valid, but was obviously done in a totally empty room, before any treatment was applied, so it doesn't help to show anything about how the room is behaving now. Also, what does the third measurement in that file refer to? It is labeled "L+R -30db"?

Since the two sets of measurements were done with different speakers, they cannot be compared validly. It is not possible to draw any conclusions at all from what you have posted so far.

I would suggest that you carefully follow the instructions I linked you to above, using the exact same speakers as you used the first time, set up in the exact same locations in the room, and using the exact same calibration. It would also help to know what speakers you used (make and model), and the locations of both the speakers and the mic in the room, relative to the hard room boundaries (surfaces of the walls, floor and ceiling).

- Stuart -