What the freq. response of other small rooms look like...

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Russian Recording
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What the freq. response of other small rooms look like...

Post by Russian Recording » Thu Apr 27, 2006 1:50 pm

Hi.

I added a sub to my system with a kill switch so that I could turn it on/off as I please. With my added sub I decided to do a DIY measurement of my room's freq response by putting up an Earthworks TC-30K at listening postion and recording a frequency sweep from my Loftech tone generator.

I have a small room, about 11 x 15. I have (8) 2' x 4' pieces of 2" 705 FRK and (4) 2' x 2' pieces of 3" 705 FRK, all stradling corners in the room.

See below:
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Image

After tuning the sub (corssover, phase and volume), the best reponse I could get based on my rudimentary measurements looked like this:

a dip of about 12 dB from 67-75 Hz
a peak of about 9 dB from 140-160 Hz

the rest was "fairly" flat from 20 Hz -20 KHz with some very narrow Q dips at specific spots within the audible frequency spectrum.

If I turn the sub off, the dip at 67 - 75 Hz is less pronounced, but it starts rolling off steeply below 55 Hz.

I know it's almost impossible to get a room like mine flat, especially in the low end, but I am just wondering if my results are pretty adequate for this kind of a room or if I can still improve it some more.

thanks.
mike

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Ethan Winer
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Re: What the freq. response of other small rooms look like..

Post by Ethan Winer » Fri Apr 28, 2006 10:36 am

Mike,

> I have [8] 2' x 4' pieces of 2" 705 FRK and (4) 2' x 2' pieces of 3" 705 FRK, all stradling corners in the room. <

That's a good start, but three or four inches thick would have been better for those larger panels.

> a dip of about 12 dB from 67-75 Hz
> a peak of about 9 dB from 140-160 Hz

I'd expect much more variation, and many more peak/null pairs. Did you really measure all frequencies continuously?

> I know it's almost impossible to get a room like mine flat, especially in the low end, but I am just wondering if my results are pretty adequate for this kind of a room or if I can still improve it some more. <

Yes, it's impossible to make any small room perfectly flat. And just as important as the raw response is ringing. I use the ETF software which shows both. Below are three graphs so you can see how you're doing so far.

The first graph shows the raw response only in a room very similar in size to yours, plotted manually 1 Hz at a time. That's more like what I'd expect in your room. The second ETF graph shows the response and ringing in a room a tiny bit larger, with and without bass traps. The bottom ETF graph shows the respone and ringing I was able to achieve in my fairly large living room home theater using 38 traps.

--Ethan

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Russian Recording
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Post by Russian Recording » Fri Apr 28, 2006 11:09 am

Thanks Ethan,

Yes there were other peaks and dips, but those two were the most prominent, they stuck out like a sore thumb. Like I said, my measurements were by no means scientific. I swept slowly through my Loftech manually while watching the meter on my Crane Song Spider and pinpointed the really bad spots.

I would really like to take proper measurements. I checked out the ETF software. It seems to be totally free, but I noticed that one the "add-ons" helps with testing low frequency response and room modes. Should I get this add-on or can I take decent measurements in the free version?

thanks again
mike

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Post by Ethan Winer » Sun Apr 30, 2006 10:47 am

Mike,

> I checked out the ETF software. It seems to be totally free <

Well, there is a demo that can do raw response only, but it won't save files, print, or display ringing via waterfall plots. To get all that you have to buy the program for $150. If you do buy it, you don't really need the add-ons. The basic version is fabulous. But I can't say if $150 is worth the cost to you or not.

--Ethan

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