RT60/measuring acoustic resonance

[Tonio]

Hi all,
So RT60 is supposed to be lower for the control room vs. tracking room, yes?
If I (in my home studio/tracking combo- I know get a real place right?) wanted to get a good decay time, what would be acceptable? I want it to live as possible, yet able to hear what the heck is going on.
On a another note I tried measuring the acoustic resonance in the
"working in progress" studio last night. I don't know how close the readings should be, or at what frequencies need to be checked. So I ran a few to see generally how it is "sounding".

PLease correct me if I am going at this the wrong way? I used Make a test tone(courtesy of Audio Ease-yup a MAC) which is a sine -sineusoidal sp?- wave thru a mixer to fee standing monitors.
60hz- 73db mix pos. - 72 db middle of room
80 - 73 - 64
100 -77 - 65
125 -79 -67
155 -79 -76
175 -82 -76
250 -79 -78
300 -82 -73
500 -80 -73
1000-82 -76
Room is 17"X 11.4X 8.6.

I guess I should have done more in the mids and upper, but I guess I'm obsessed with the low end


Do I need more low bass trapping to even /smooth it out?

I do have the front absorbed with low bass traps(corners& 1 in center) and mid absorbers, back wall has low mid trap. Ceiling has polycylindrical hanging on back end.

So what y'all think any suggetions?

TIA

Tony

 

[Ethan Winer]

Tonio,

> Do I need more low bass trapping to even /smooth it out? <

More important than reverb time - in a small room, anyway - is using bass traps to reduce the standing waves that cause extreme peaks and dips in the frequency response.

> I do have the front absorbed with low bass traps(corners& 1 in center) <

What kind of bass traps?

--Ethan

 

[Tonio]

Ethan,
thanks for trying to help. The bass traps are of your design!!
The centered one is 2x8' with 1/4" ply and the corner ones are 2x8'with peg board covered with cloth. Between corners and center is cloth covered only traps. The one on back wall is 4x4 with 1/2" ply.

After much thought and messing with more tones, I tested the back wall reading . I'm geting a dip around 40, 60 * 80 hz. There isn't any treatment on the side walls yet, so it must be the low end that needs more traps. I realize the deeper the cavity & the ply thickness are the factor in tuning the traps. Could a thicker ply like 3/4" be good, or would it necessitate a larger panel in general? i.e. is it too thick to actually work. I was thinking a couple 2x8' on each side & staggered on opposite side walls.

Any suggestions appreciated.
Tony

 

[Ethan Winer]

Tony,

> the corner ones are 2x8'with peg board covered with cloth. <

If you're using peg board with holes in it, they won't work very well as bass traps. Panel traps like the ones I show in my plans need to be sealed air tight to work. With holes, the absorption will be much less, similar to using fiberglass alone. Except they'll reflect mid and high frequencies, and so be less effective than fiberglass there.

> There isn't any treatment on the side walls yet <

Yes, you really need as many traps as you can fit and afford.

> Could a thicker ply like 3/4" be good, or would it necessitate a larger panel in general? i.e. is it too thick to actually work. <

Yes, that's getting pretty thick, which makes the panel too stiff to vibrate at useful frequencies.

My best suggestion is to follow my plans exactly, not only for size and materials, but also placement as you alternate low-bass and high-bass traps with fiberglass only absorbers.

--Ethan