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[Ethan Winer]

finetuner wrote on Mon, 01 October 2007 17:05

i played both speakers simultaneously. I reckeoned, that would resemble the normal situation. So it's better to do it with one channel at a time?

Peter, it's useful to test both speakers at once and each separately. With most pop music, bass instruments are panned to the center. So your original thought is correct, to test with both at once to better simulate how bass frequencies will be played in your room.

Quote:

The strongest and lowest peak (60Hz) is mainly at the front-floor corner. So i may not need absorption covering the entire height.

I'd aim to trap as much total corner surface as possible. With bass traps, it's awfully difficult to have too many.

--Ethan

[brett]

like in glenn's drawing , I still think your listening position should be in the front half of the room. I think the proximity effect on the speakers being closer to the front wall can be dealt with a lot easier than the issue of being in the back half of a long narrow room.

[finetuner]

Brett, can you explain why ?

If i shift everything foreward, the bass will be enforced and i'll need even more trapping. I don't see the point.

Are you saying that it won't matter since the listening position will be more in a null ?

Somehow it feels like a waste to only use such a small part of the room.
But that's not based on science obviously

The 38% rule counts for either front or rear wall, so why not use it the way i do now and give the speakers some room to breathe ?

Peter

[gullfo]

you want to avoid 50% front to back, top to bottom to ensure you're not sitting in a null. 38% is general rule. attached is a graphic showing calculated room modes for your space. the wave form lines show approx locations (+/- 6") for each of the modes across each of 3 axis. you typically want to avoid the first order modes since they're usually the strongest but since you have 9' and 18' dimensions you'll have some additional strength in common modes. 8' is also close...

[brett]

 A long thin room is going to have serious issues anywhere near the mid point to rear wall. Especially since it is 9x18  a perfect half. So, what you're hearng as you compare the front to back sound may very well be a null at the mid point and not necesarily bass being "reenforced" at the front. It's pretty easy to pull the low shelve down on a dip switch or eq to deal with an extra 3db of bass because the speakers are near a front wall, as opposed to sitting in a null. The Rear wall will have other issues. Like listening to sound down a tunnel.  

I know tube traps are expensive, but you could use Roxul semi rigid panels with burlap and they work well on my front wall. I am no expert but I know what my ears hear and based on your set-up I think my ears would not like being in the middle of that room nor the rear half because of how narrow it is.

But if you can pull it off it's worth a shot. Best of luck-B

[finetuner]

OK Brett, i'm starting to get the picture now.
For a room this ratio, the 38% rule tends to be limited to the front. Otherwise the (close) sidewalls are going to play a big role.

The multitude of the sizes don't help either. I should move one day.., but fortunately it's not all that bad.

Peter.