Bass null, diffuser/reflector maybe help? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 11 Old 01-24-2013, 01:27 PM - Thread Starter
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Hi, as I'm the youngest in the family I have the smallest bedroom, and it's making setting up my sound system a bit of a challenge.

I notice there's way more bass near the corners of the room, and a null in my sitting location. (center of room) Would some corner and wall diffusers/reflectors help bounce the bass back into the center of the room?

I was thinking maybe along the back 6'9" wall as well as the side 8'7" wall. I'm sitting right in the middle of the room.

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post #2 of 11 Old 01-24-2013, 01:35 PM
 
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Quote:
Originally Posted by Ak Gara View Post

Hi, as I'm the youngest in the family I have the smallest bedroom, and it's making setting up my sound system a bit of a challenge.

I notice there's way more bass near the corners of the room, and a null in my sitting location. (center of room) Would some corner and wall diffusers/reflectors help bounce the bass back into the center of the room?

I was thinking maybe along the back 6'9" wall as well as the side 8'7" wall. I'm sitting right in the middle of the room.

In many cases the most economical and easiest way to improve the distribution of bass is to add a second subwoofer.
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post #3 of 11 Old 01-24-2013, 01:55 PM
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Start with a 'crawl test'. Put the subwoofer in your listening position then crawl around the room listening for where the bass is loudest, place the subwoofer there.

May be hard given the limited placement options you have but its worth a shot.
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post #4 of 11 Old 01-24-2013, 04:50 PM
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+1 to all the above. Unfortunately a diffuser has to be a significant proportion of the wavelength to affect that wavelength. The lowest note on a normal bass guitar is about 40 Hz - - a 28 foot wavelength. It's possible theoretically to improve bass smootheness with absorbers, but they need to be big too. You wouldn't have a room left. Best to maximize position of yout current sub and think about a second to help smooth the room modes. Flippin physics . . . .
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post #5 of 11 Old 01-24-2013, 05:02 PM
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+1 to all the above. Unfortunately a diffuser has to be a significant proportion of the wavelength to affect that wavelength. The lowest note on a normal bass guitar is about 40 Hz - - a 28 foot wavelength.

not to mention typical distance guidelines to be ~ 3x design frequency to be in the "far-field" of the returns. tongue.gifeek.gifsmile.gif

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It's possible theoretically to improve bass smootheness with absorbers, but they need to be big too. You wouldn't have a room left.

only if limited to porous, velocity-based absorbers.
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post #6 of 11 Old 01-25-2013, 11:21 AM
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Originally Posted by arnyk View Post

In many cases the most economical and easiest way to improve the distribution of bass is to add a second subwoofer.

Yep this is what I think too. Save yourself some effort though and use two subs that are identical. Using mis-matched subs can lead to unpredictable effects in the region <50Hz where nearly all sub mfgs use EQ. Two subs with different EQ curves (and most importantly different phase shifts) can cause some integration issues.

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post #7 of 11 Old 01-25-2013, 11:25 AM
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Originally Posted by localhost127 View Post

not to mention typical distance guidelines to be ~ 3x design frequency to be in the "far-field" of the returns. tongue.gifeek.gifsmile.gif
only if limited to porous, velocity-based absorbers.

reasonably true, but to get wide enough band absorption, and capture anough of the bass to eliminate modes, would require multiple differently-tuned resonant bass traps (like a limp membrane), which may not be like filling the room with four feet of porous absorption on every suface but would still be intrusive to prohibitive in a small room.
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post #8 of 11 Old 01-25-2013, 11:36 AM
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Much great advice ...not much else to ad ... but; perhaps experimentation w/near-field subwoofer approach, as after careful optimizing and tuning, you'll both lessen modal significance, and lower playback levels,...which helps in many ways.

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post #9 of 11 Old 01-25-2013, 12:42 PM
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+1 Leave it to the sound guy to point out the simplest and potentially most effective fix.
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post #10 of 11 Old 01-25-2013, 01:04 PM
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Quote:
Originally Posted by Ak Gara View Post

I notice there's way more bass near the corners of the room, and a null in my sitting location. (center of room) Would some corner and wall diffusers/reflectors help bounce the bass back into the center of the room?

You're already getting some good advice, and I can add a bit more: First, the center of the room front to back is the worst place to sit, because that gives a deep bass null at your room's lowest resonant frequency. For a room that's 8'7" front to back, that frequency is about 66 Hz. So I'd definitely sit forward of the center line.

As for diffusers, those are meant for mid and high frequencies. If you think about it, your rear wall is already reflecting bass waves back toward you, and that's what causes the problem! This short article is mainly about home recording, but all the same principles apply to hi-fi and home theater too:

Acoustic Basics

--Ethan
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post #11 of 11 Old 01-26-2013, 05:22 AM - Thread Starter
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Thanks for all the info. smile.gif

There's only one other place I can put it, bring it off the floor and put it on the draws unit to the left of my PC. I'm gonna try it there.
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