Remove a Corner Bass Trap and the “Suck-out” Went Away?
Thinking you may remove a corner bass trap? This week ASC President and TubeTrap Inventor, Art Noxon, PE shares his knowledge on the subject.
It happened to Bob Hodas once and it was so unusual that he mentioned it in a MIX article on room acoustics. Actually, what he ran into could easily have been a live example of a technique we use in the design and setup of listening room and control room acoustics.
Remove a corner bass trap? It happened to Bob Hodas once and it was so unusual that he mentioned it in a MIX article on room acoustics. Actually, what he ran into could easily have been a live example of a technique we use in the design and setup of listening room and control room acoustics. Here’s how it goes:
Usually people put bass traps in corners of the room to damp the room modes, reducing the Q or sharpness of resonance from 30 down to about 10. This lowers the strength of the resonant peaks a little, around 1 dB and at the same time significantly reduces the amount of “suck-out” by as much as +5 dB. Unfortunately, no matter how many bass traps you use, you’ll still have the same room mode being stimulated. All you can do is tweak the strength of the peaks and valleys, using corner loaded bass traps.
But what is going on when you inadvertently pull a bass trap out of the corner and the suck-out you were measuring disappears. Clearly we are not fixing a suck-out by adding bass traps, as is the standard procedure. Something weird happened. We put the bass trap back into the corner, where it belongs and again, the suck-out reappears. This may be a mode problem or it may well not be a mode problem at all. Here we are going to ignore modes aspect of this and just look at how reflections can cause this effect.
What if the listening position is 5 feet off the back wall and the room is wide enough that the distance to the back corner is 10 feet. The round trip distance for the back wall bounce is 10 feet and the round trip distance for the diagonal bounce out of the back corner is 20 feet…