So what's the verdict on bass traps in a HT? Will I really hear a difference? Seems easy enough to build them myself. And relatively cheap. Anyone installed them and can truly say movies sound a lot better?

About 50% of my walls in my HT have no insulation behind walls (previous owner built and i'm lazy to do anything about it). Low frequency sounds from movies DO sometimes rattle stuff behind walls or the walls themselves.

Thoughts?

(I need to link to my HT pics/specs in my sig. But I have a pair of M60s, VP150, a semi decent sub and various other speakers for a 7.1 setup)

Bass traps keep standing waves from forming. What happens in a room with parallel walls is the pressure waves of different frequencies reflect off walls, especially corners. This causes some frequencies to build up, and others to be sucked out. Bass traps keep the energy from reflecting back into the room, allowing for much more even response throughout.

They're not going to keep things from rattling. Nor will they offer any sort of sound proofing. Although you may be able to play your sub at a lower level because you'll be able to hear those sucked out frequencies without having to crank it up.

Thanks ClubNeon. I guess i'm a noob in the science of sound but i'm reading up on standing waves and bass traps in general. Good stuff....and interesting.

So anyone have good links on how many bass traps are good for an HT? Placement of them? When placing in corners, do they have to go from ceiling to floor (based on pics I seen)?

Thanks
LH

An excellent read on bass traps:
http://www.ethanwiner.com/basstrap.html

The four corners are the best place to start, and yes from floor to ceiling is they way to go if at all possible. That'll help in just about every case without having to worry about any calculations or measurements. After that if you want to go further you'll want to get some equipment (if just a Radioshack SPL meter and a copy of Room EQ Wizard) to get an idea of what it left to tame, and where supplemental traps would ideally be placed.

Try this thread: http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=144818&site_id=1

Lord, if you listen to a movie in a room that has no carpet or wall coverings, it sucks. Once you add carpet, furniture, etc. it is night and day better. The same applies to bass traps and first reflection panels. There is something to be said about over treating a room, but if done right it gives you great results.

Amen.

What kind of treatments normally on the walls? Just acoustical panels I assume?

Not trying to hijack, but it seems I may have an issue with the sub though in my room. Going to take some experimenting, but right now, it's not good Is the point of a bass trap to mimize reflections back into the room and the cancellation of sound waves? I always figured they were just to reduce boominess, but if it's the former I think I am going to have to look into something. My walls are bare currently, but they are insulated behind, ceiling included, if that matters.

The boomieness is caused by the reflection of lf waves inside the room so they are the same thing.

Bass trapping is most effective above 100Hz, so depending on where your issue is, bass trapping can be effective. The higher the frequency, the more effective traps become.

From all the reading I have done and from some experiments I have done in my room, to be effective, you need a fair amount of trapping. All 4 corners of the room is a minimum.

First reflection points, though equally important, are a whole other beast involving higher frequencies. There is disagreement over whether or not you should use absorption or diffusion at first reflection points on your walls. Absorption on the floor and ceiling first reflection points is desired, but again, this is for higher frequencies. A carpet would probably start being effective at something north of 1,000Hz. I'm not saying its not important, its just not bass trapping.

If you live in a [mostly] square concrete box like me, all hope is lost.