Sound absorbers

**stevedruck** · **09-24-09, 05:59 PM**

Hi,
I'm setting up my basement as a sound studio. I've studied acoustics so I know about absorbing, diffusing and isolating...I just don't know how much to use and how to target specific frequencies. I'm using cotton insulation as the core of my absorbers,(great stuff, not itchy and very high NRC rating!), which I have on the walls and ceiling, thicknesses from 1 1/2" to 5 1/2". The trouble is, to get the room "flat", my EQ is a big smiley face with the center frequencies cut as far as possible and the highs and lows boosted. I need to change/ rearrange stuff but what?
Steve

**bpape** · **09-24-09, 06:09 PM**

Welcome

What are the room dimensions?
Where are the speakers in relation to the room boundaries?
Are the speakers on a desk?
Where is your head in relation to the room length?
What is the natural frequency response of the speakers?

Bryan

**stevedruck** · **09-25-09, 07:22 PM**

Thanks for responding, the room is 13' x 22' x 7' high. It's far from ideal but I just want it to be as good as possible...the speakers are 6" from the front (13') wall which is sheeted with 3/4" plywood with pleated moving blankets on them, angled in 10 degrees with the speakers so they're more perpendicular to my line-of-site. These are big Carvin vintage PA speakers with a ported 15" EV for lows and a separate EV 1" radial horn for 1.2k and up...28" wide x 48" tall (with horn) x 24" deep... overall frequency response is 55Hz to 15kHz. My head is 9' from the back wall or 2' back from the center at a desk with a Futon couch in front of it.
Steve

**bpape** · **09-25-09, 11:23 PM**

OK. Well, then most likely the bottom 3 bands of the EQ should be ignored as they'll be below the natural response of the woofer.

Try moving forward about a foot with your head. Might not be perfect but should give smoother bass response.

Remove the blanket from the front wall. That's way too much high frequency only absorbtion. Pull the speakers forward at least a couple of feet and use something like a 4" thick panel behind them.

Bryan

**stevedruck** · **09-27-09, 10:29 AM**

Hi Bryan,
By "4" panel" I'm assuming you mean one or more of my insulated panels? How big should it/they be? Spkrs are 2½'w x almost 4' tall, remember...
Also, I was labeling the 1.5kHz area as center frequencies, is that correct? 700Hz to 2k were the loudest sine-tones when I first tested SPL with the EQ set flat. On a graph, the "decibel-hump" starts at 500Hz(up 20db to the 1.5k peak) then starts dropping around 3 or 4k...sorry, I guess I should have mentioned these numbers at the beginning. I was thinking I had to add more stuff like the blankets to absorb the 1k area...I'm way off, aren't I? jeez...
I sure do appreciate your time on this Bryan, if you ever need any advice on house carpentry, I have over 30 years experience at it.
Thanks,
Steve

**bpape** · **09-27-09, 11:15 AM**

It would be really nice if you can post plots. One from 20-300Hz unsmoothed and then one from 300 to say 4kHz would be great to really see what's happening.

Bryan

**stevedruck** · **09-28-09, 06:14 PM**

Bryan,
You lost me with your terminology(plots,unsmoothed?) I may be old but I'm just a baby when it comes to this stuff...all classroom, no field experience...
Steve

**stevedruck** · **09-28-09, 06:15 PM**

I do have a scanner...

**bpape** · **09-28-09, 11:12 PM**

Just wanting a frequency response plot and also the decay time/waterfalls. When you run REW, turn smoothing off in the bass.

Bryan

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