Bass Trap for a sub woofer

[6969]

Hello peoples of the DUC

I unfortunately have to set my desk against a wall.I'm about 6-8 inches from it. For my nearfields I'm gonna put some 3 inch foam on the wall to absorb sound. For my soon to arrive sub woofer I am having some trouble figuring out a way to trap the bass from hitting the wall behind it. Should I assume it will be a harder job to absorb because of the low frequency thump? Is there some sort of flat type bass trap that I could simply stand up behind the sub or something like that?

I have another question about the placement of the sub. Should I have it directly in the middle underneath my desk or is it ok off to the side?

Thanx for the help in advance.

DJ

[6969]

Do I even need a bass trap behind the sub at all?

Thanx

[6969]

Any experience with this in here?

DJ

[Nitronick]

Check here

www.realtraps.com

Ethan is a smart fella.

As far as sub placement, I think you should at least try to get it as close to center as possible. You would be better keeping it away from the wall though, as corners and wall/ceiling and wall/floor joints are where you will see low-end standing wave problems.
Good Luck
Mitch

[Lalaman]

Acoustics and cables are relatively low on DUC.

I read that the assumption that the positioning of a sub would be irrelevant was wrong.

It was said that placing the sub woofer should be done in the following way.
Put the sub right there where the listeners head usually would be. Then check out all different positions in the room to find out where you can hear the sub at best.
The position you end up with should be where you place the sub.

If it stands on no stand, but on bigger surface like a table, shelf, or the floor, better put the sub either on a rubber base ( 1/2 m2 = ~ 6$ ) or cones. Isolating from vibrations wouldn´t hurt also for the other speakers.

[Stone Knife]

That's really a clever idea!

Not having that technique handy, I just had to try several configurations until it sounded right in my monitoring position.

Because the bass waves are so long, it's not uncommon to hear your sub better from 15 feet away than whan it is 4 feet away from the sub.

I first put the (front-loaded) sub in between my other two speakers, facing out.

That's when I could hear better 20' back than right up front. Not optimal.

After awhile, moved the sub around in various locations and directions, wound up with it on the floor, pointed 90 degrees off axis to the main speakers, off to the right, out 1' from the back wall, and midway between the right wall and the right main speaker, facing back toward the line of main speakers.

It looks odd that way, but turns out to distribute the amplitude and frequencies most evenly in the room and still remains 'invisible' when listening with eyes closed. Better than it did in the same location but pointing into the room or at a 45 degree angle.

Try to let your ears make the decisions and not your eyes!

Hold off on bass traps until you're sure you need 'em. [img]images/icons/wink.gif[/img]

[Nitronick]

Originally posted by Stone Knife:

Try to let your ears make the decisions and not your eyes!

<font size="2" face="Verdana, Arial">Good advice!

Hold off on bass traps until you're sure you need 'em. [img]images/icons/wink.gif[/img]

<font size="2" face="Verdana, Arial">If you have a square or rectangular shaped room with no low end treadment, you do need them. Not those fake foam traps either! And if you are hearing your sub better from 15 or 20 feet away, then you have some standing wave doubling going on. An acoustially accurate room will provide the same low end no matter where you or the sub is positioned.

6969,
It would be a good idea to position your sub where you feel it's best, and play back some low end sine sweeps. Use this:

http://www.nt-instruments.com/minstruments/

Look around the site for the download of the virtual MR1. Cool little software gizmo!
Anyway, play some low sine sweeps while walking around your room. Pay particular attention to corners and the joint of the ceiling and walls. Listen for buildup or cancellation of frequencys. Those spots are where you should treat.
Also of use would be a room mode calculator like this one:

http://www.mcsquared.com/modecalc.htm

This will give you a general idea of what freqs and where.
Hope this helps.
Mitch

[6969]

Thanx fellas for the help on this one.My modest studio exists in my front room of my apartment so I will be keeping foam placements to a minimum. Asthetically I think a basic absorbtion of 3 inch foam behind my near fields(thanx Stone) will be fine for the moment and I will have to do some experimentation with the sub and placement.Damn I feel like a good student right now [img]images/icons/grin.gif[/img] Why didn't they offer this class in high school.I might have gotten better grades [img]images/icons/cool.gif[/img]

The input is highly appreciated.

DJ

[Lalaman]

Originally posted by Nitronick:
An acoustially accurate room will provide the same low end no matter where you or the sub is positioned.

<font size="2" face="Verdana, Arial">Don´t know if your obvious ignoring is just due to the idea that I wanted to put your advice down, which is not the explicit case. ( you could had figured that at the time stamps of our posts ... [img]images/icons/tongue.gif[/img] )
But the statement above is still not right.

However, if it helps the physics on your galaxy that´s alright again.
I regard that the sorts of material we know of here is only about 4% of what is out in space.
[img]images/icons/grin.gif[/img]

Lalaman