Speakers facing the short way into the room

Hi Ethan, thanks for joining us here on dzwiek.org!

I know you are a big proponent of speakers firing the longer way down the room. I sort of did the opposite.

The room (which will be used for acoustic guitar recording and playback) measures 20' x 12' x 8'6" and has carpet floor and concrete ceiling. We ran pink noise and spl measurement and this is what we came up with (please see the attached picture). This is where it sounds right to me.

I have no bass traps in the corners and there's nothing on the wall behind speakers. Panels are 48" x 72" x 2" Roxul mineral wool.

Do you think we missed something important? I would really appreciate your take on this.

Thanks,
waldek-j

It's easy to demonstrate that firing the longer way gives a better bass response. See the graph below. Have you tried measuring your room? That's the only way to know for sure how good or bad the response and ringing are. Having a wall close behind you always creates one or more deep nulls somewhere in the bass range. The null frequencies depend on the distance from your ears to that wall. If a null occurs in the "tubby" range around 200 to 300 Hz, it might sound subjectively "better" even though the response is not accurate. Again, measuring is the only way to know for sure. I use the freeware Room EQ Wizard program.

--Ethan

Thank you, that seems to prove your point. Now, does improving bass response automatically improve decay times and modal ringing?
I've had it setup the "long way" and it produced some major ringing in 160-250Hz area. No amount of tweaking would fix this (I'm limited to ten panels at the moment).

I have downloaded the RoomEQ Wizard and gave it a quick test. I'm still trying to figure out the software, so these results can't be taken as reliable, but I'm working on it.

(click to enlarge)












I'd appreciate any comments that you might have.

Thanks,
waldek-j

Improvements in frequency response made by position changes only should not reduce ringing times. You might hear less ringing because you're hearing less of the peak's energy at that place in the room. But the decay times should be the same.

--Ethan

Ok, very good.

Now, assuming the room has about 80 square feet of absorptive panels, how many more panels would be required to take this room to within 10dB of flat from say 100Hz to 10kHz? (and to keep reverberation times short and within close tolerances). Four five times the number?

Just asking for an educated guess

Thank you,
waldek-j

I honestly don't know. That's why it's always useful to measure your room as you add treatment!


--Ethan

I understand. How about the test room, the one in post #2? Can you give us the square footage anf thickness of paneling?

It appears to be within 10dB of flat from 80Hz to 10kHz.

That graph is from this review in Sound On Sound magazine:

http://www.soundonsound.com/sos/sep04/articles/realtraps.htm

It's a small room, and the author mentioned "minimal acoustic treatment" so I assume it was measured before he put in the RealTraps.


--Ethan

Much appreciated!