Help with decreasing resonance

[gago1101]

I was wondering if there was an easy way to decrease the resonance of the speakers. My speaker are about 88 lbs or 40 kg each. At high volumes I can feel the resonance in the cabinet and I am sure it is affecting the sound. Is there an easy way to decrease this resonance? I was thinking of increasing the weight of the speakers by adding heavy glass or metal plates on the sides that would also serve an aesthetic purpose. Would increasing the weight be enough or is this resonance due to an inherent design flaw of the speaker cabinet and is unfixable?

thanks in advance

[turk 182]

well you've given very little to go on other than stating how much your speakers weigh and you perceive a problem with a resonance.
what kind of 88 pound speakers are they,fullrange,two-way,three way,sealed,bass reflex?
is your source a turntable that might not be adequately isolated or experiencing low frequency feedback?
mass loading your boxes might be the right thing but with so little to go on i'd be guessing.

[gago1101]

They are 2 way rear ported (2 ports) bass reflex reproducing bass down to 20Hz at around -3db. two 10 inch drivers and a high freq compression driver mated to a horn. The source is an Oppo BDP-95 to active crossovers to speakers. Also, the resonance seems to come mainly from the bass at higher outputs.

[turk 182]

ok
what is the box made out of ? and how big is it? and is any sort of damping used inside?

[gago1101]

It is thick plywood with wood veneer on top measuring 48.5x11.6x16.3 inches (HxWxD). It has foam sheets inside for damping.

[turk 182]

well your on the right track if your trying to stop the box from resonating at higher SPL's mass loading with a dense material is the way to go.
the foam sheets aren't going to control bass energy.
is there any diagonal or lateral bracing inside especially on the 48.5 X 16.3 side panels.
your original thought on adding metal cladding or thick glass might indeed be effective providing a good bond between the two.
other options could include something like Dynamat or heavy weight felt inside the box.
have you identified the prime or band of frequencies of the offending resonance.

[gago1101]

Thanks for the suggestions. There is one brace between the 2 mentioned panels. How hard is it to find out the resonant frequency? I have a program that measures SPL, impulse, et. Not sure how to measure the resonance though

[turk 182]

not knowing what your SPL measuring program is or what features it has makes it alittle hard to tell you which way to go from here.
if it has pink noise or a sweepable generator it should be fairly easy to identify as a significant bump in the response curve assuming your hitting the spl level that excites said resonance.
is this a commercially made speaker or is this something you built from a kit or designed yourself?
one brace how big and where.
can you upload any pictures of these speakers?

[gago1101]

It is a modified Klipsch RF7 ii. I always assumed the large rise in SPL below 80Hz was due to my Bass processor. I do like to have a loud bass.

[turk 182]

wow
an almost 20 db increase in bass below a 100 hz
i like bass loud too but if the the rest of the frequency spectrum is getting left behind in the dust...
can you give me a little more info on your Bass processor.