[Ultralight]

I saw a bass trap that is triangular in shape and two inches thick. The dealer hung those on the wall's top corners behind the speaker.  However, occur for me to ask whether it would be better to have  those triangular bass trap on the lower corner than the top corner?

I assume that basstrap that reaches from floor to ceiling would be better but if one only had the triangles, would it be better to place on top or lower corners?

Thanks!
UL

[paul79]

If you have carpet, I think the upper corners would be better. Might be better even if you don't   

[Big Red Machine]

2" thick does not a bass trap make.

6", 8", and better, 12" make bass traps.  Whatever those triangles are, they are not going to do much.

[Glenn Kuras]

2" thick does not a bass trap make.

6", 8", and better, 12" make bass traps.  Whatever those triangles are, they are not going to do much.

Agreed. 

[Wayner]

The idea is to keep bass frequencies from rebounding in the corner(s) where bass can easily be augmented because of the 3 boundaries, assuming these are hard surfaces. After all, in sub-woofer placement, each surface can produce up to 6db of augmentation, in the corner would make for approx. 18db.

The corner can also act as a reflector or a horn and project the amplified (naturally) waves and beam them towards the listener.

IMO, the bass trap might be a strong term, but your corner wedge can muffle the bass energy without being massively thick. You just want to stop the reflections, not completely suck out all of the bass.

Most bass traps that I have seen are cylindrical and stand about 6-7 feet tall at anywhere from 12" in diameter or more.

'ner

[InfernoSTi]

There is a second concept with triple 90 degree corners and that is high frequency distortion.  I find that if I place something to remove the corners from the equation, regardless of bass mode issues, the sound quality improves.  This is why I like to have the bass traps (GIK soffit traps) standing vertically in the corner on the ground and then a QRD diffusor on top of that all the way to the ceiling across the corner.  That way I address the bass mode and the high frequency distortion issues equally.

I suspect the 2" triangles were there to address high frequency only.

John

[steve f]

I used to think that bass traps had value. Then I read Geddes and Parham. The best way to get uniform bass in a listening room is through multiple subwoofers. Two subs will greatly reduce room nodes. Four subs, which can be placed just about anywhere in the room provides the best uniformity. Yes it get expensive, and takes up space, but it works.

steve

[InfernoSTi]

There are different approaches to managing bass modes in rooms.  They all have their pros and cons.  No one solution is perfect although folks who take their solution to an extreme will say their method is best.  The truth seems to be that dealing with bass modes is better than not dealing with them and different systems and situations require the use of one of the methods over another. 

There are other acoustic issues at play, as well.  These aren't related to bass modes directly but affect sound quality.  Things such as first reflections that can't be addressed electronically, the triple corners causing high frequency issues, and overall decay times, for example.

I use three different methods to address bass modes in my room. 

One is the physical bass traps.  I have some that are two feet thick and I have them placed in a variety of locations to start to manage the modes.  I find the modes that remain are much more manageable that without the physical traps. 

A second is I use OB sub woofers because they excite bass modes differently (less) than most subwoofers.  If I were to use a box subwoofer, I would use a sealed box, not a ported box, for similar reasons. 

A third is I use multiple speakers each with multiple drivers and I run them in stereo.  I also located them where most people do not locate subwoofers.   The bass modes are further excited less and I get much more localized bass that you can absolutely tell directionally.  I believe the theory has to do with harmonics and keeping the subs related to the mains, but that is another conversation altogether.

I do not use DSP type mode control but I understand it is getting much better in the last two years and I have heard folks who really spend the time to get it right are gaining a lot of value from it.  I would only use it below some number such as 250 Hz, perhaps lower, however.  I really don't want to mess with my mid and upper frequencies. 

John

[paul79]

There are different approaches to managing bass modes in rooms.  They all have their pros and cons.  No one solution is perfect although folks who take their solution to an extreme will say their method is best.  The truth seems to be that dealing with bass modes is better than not dealing with them and different systems and situations require the use of one of the methods over another. 

There are other acoustic issues at play, as well.  These aren't related to bass modes directly but affect sound quality.  Things such as first reflections that can't be addressed electronically, the triple corners causing high frequency issues, and overall decay times, for example.

I use three different methods to address bass modes in my room. 

One is the physical bass traps.  I have some that are two feet thick and I have them placed in a variety of locations to start to manage the modes.  I find the modes that remain are much more manageable that without the physical traps. 

A second is I use OB sub woofers because they excite bass modes differently (less) than most subwoofers.  If I were to use a box subwoofer, I would use a sealed box, not a ported box, for similar reasons. 

A third is I use multiple speakers each with multiple drivers and I run them in stereo.  I also located them where most people do not locate subwoofers.   The bass modes are further excited less and I get much more localized bass that you can absolutely tell directionally.  I believe the theory has to do with harmonics and keeping the subs related to the mains, but that is another conversation altogether.

I do not use DSP type mode control but I understand it is getting much better in the last two years and I have heard folks who really spend the time to get it right are gaining a lot of value from it.  I would only use it below some number such as 250 Hz, perhaps lower, however.  I really don't want to mess with my mid and upper frequencies. 

John

Great post!