Bitumen Panels

[Soulwax]

I’m looking for a method to damp the energy leaving the rear of my loudspeakers. The reason is my loudspeakers sound notably more balanced when approximately 4ft from the rear wall. Unfortunately, owing to domestic arrangements, I can only get them about 2ft from the real wall.

I’m thinking a 2mm bitumen 'dedshete' panel glued externally to the rear of the enclosure may help. Any comments?

My other query (and this may sound daft) but do these types of bitumen panel smell?

[wintermute]

I think probably you will find that it isn't energy being radiated out that back of your box that is the problem, but that you are getting reinforcement of the sound waves that wrap around the baffle and then bounce back off the wall.

If your speakers crossover has baffle step correction in it, you might want to try lowering the amount of cut.

Tony.

[Soulwax]

Thanks for this information.

The loudspeaker crossovers are a standard pair of 2nd order filters with damping on the tweeter, there doesn’t appear to be any additional compensating networks.

Is there any way to reduce the output of the port (while retaining tuning frequency) such that output is somewhere between that of a fully open port and a fully blocked port – a resistive vent or similar?

[quiet]

as i understand it - if you plug the port with a bit of stuffing or foam
you create an aperiodic enclouser
this may provide some of the dampining you seem to be looking for
with out effecting too much else

i have heard others mention that if your running a sub this also helps with overlay

[rcw]

This sounds like a standing wave problem, putting the speaker at a particular place in front of the wall is causing cancellation of the standing wave, the only thing to do if the best speaker position is inconvienient is to equalise the peak away.