Bass trap or panel?

[MichaelandKlipsch]

Hello, I have a quick question that deals with the architecture of my room in its bass response. I have a long room 23 long and 13 wide with 9 ceilings. I have overall great bass but was wondering if I were to use a reflective panel in the back right rear corner of the room if it would put some of the bass back towards the middle seating position? I have my subs in the front two corners of the room? Also where should I get a reflective panel and or should I use a bass trap instead?

[CECAA850]

Reflective panels are used to absorb high frequencies instead of letting them bounce off the walls and get to your ears milliseconds behind the direct sound from the speakers.

Bass traps absorb low frequencies and prevent them from from bouncing back into the room and cancelling other bass waves out.

Use the proper device for what you are trying to accomplish.

[colterphoto1]

A quick study of some of the posts here or the internet site of Ethan Winer will shed some light on the subject of acoustics. Generally bass is thought of as omnidirectional, that is going out in all directions pretty equally. Things you can do to increase the bass output without adding equipment include - putting them in corners (some experimentation necessary to keep from being boomy at a single frequency), or putting them together so they act as one. That gets you a FREE 3 db output gain. I have my Klipsch THX subs both stacked and in a corner of the room.

[artto]

Both of the previous post are "right".....and "wrong". (sorry guys) []

Reflective panels are not used to absorb high frequencies. They scatter the higher frequencies around which in turn eventually causes the higher frequencies to loose engery. The diffusion can also aide in making the room sound larger than what it is. There are a few outspoken individuals around that have come to claim that the large polycylindrical "diffusers" that you often see in recording studios or concert halls are not actually diffusers, but they are wrong and do not understand the problem comprehensively. And as far a the large polycylindrical diffusers are concerned, they actually absorb more in the lower frequencies and very little in the high frequencies. These can easily and cheaply be made from inexpensive tempered Masonite.

A bass trap needs to be large and deep because as the frequencies go lower, the wavelengths get much longer (400Hz=2' 100Hz=11' 50Hz=22'). Bass tends to pile up or accumulate at the room surface intersections - wall/ceiling, wall/floor, wall/wall/floor, etc. So those are the most effective locations for bass trap placement.

If you place multiple subwoofers in the same location (stacked for instance) you may get the additional output Colter mentioned but you will also most likely increase the bass cancellations making the low frequency response mor uneven. Subwoofers work best when used in a distributed manner when in a closed room the size we deal with in residences. In a very large indoor space, or outdoors, the situation is different and you cen benefit from summing the subs close together.

Your room is very long and narrow. You are going to have some major issues with irregular bass response which is why its important to start with a room that has appropriate proportions in the first place. Moving your listening position and speakers around can also help alleviate some of the bass irregularities as far as what you hear at any particular location. You may even find that you prefer one location over another for different kinds or music or recordings.

As far as bass traps go, the above mentioned Masonite polycylinders can be back filled with a dense rigid insulation made from mineral wool such as Roxul R-80. You could also use Roxul R-80 to make large corner bass traps, wraping them in some kind of cloth covering to keep the mineral wool dust contained. Auralex and Ethan Winer's company make some pretty good large corner bass traps. Both Klipsch and myself use the Auralex MegaLNRD bass traps in our rooms. I also have multiple layers of Celotex rigid insulation and Roxul R-80 behind the polycylinders in my room to act as bass trapping.