standing waves

[David Deratany]

Is it possible for a standing wave to be generated in a cabinet at a frequency above 500 hz when that is the crossover frequency?

[GM]

Yes, it can be the harmonic of a lower fundamental.

GM

[David Deratany]

Thank you. That helps. I'm getting a resonance somewhere between D and D# above A 440 and I'm trying to determine whether it is the system or the room acoustics. It would have been nice if I could have eliminated standing waves being the cause.

[GM]

If it moves around the room with the speaker....... Anyway a 500Hz standing wave is ~6780"/500 = ~13.56", so if one of the cab's inside or outside dim is around this, or a driver is ~ this high above the floor, or from a wall, etc..

Lots of ways to generate one IOW. Good hunting!

GM

[David Deratany]

Bingo!!! Interior depth ~13.5"

What would be the best way to break it up? I currently have 1" fiberglass on the rear, top and one side, but previously had dimpled foam on all sides, so I'm not sure that lining the front will fix the problem, unless I need to use a lot more fiberglass.

[GM]

If it's strong enough to be audible then the two walls aren't rigid/damped enough, so it sounds to me like triagulated bracing and duct seal is the cure, unless you want to stuff the cab with ~1.5lb/ft^3 of polyfil/Miraflex/or equal.

GM

[David Deratany]

Thank you, again. I'll work along those lines.

David