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|Today, 04:59 AM||#1|
Join Date: Feb 2006
Case study - modal nightmare
Link to original post here: AE Speakers Dipole 15 or LO15 ? Need advice
We are posting here in relation to a question surfaced by member JackG3, so this is his thread.
He asked about problems he is having with room modes and his woofer EMINENCE ALPHA 15 A in a dipole. He mentioned the room dimensions, in the same thread, with a waterfall attachment for the same driver.
1 : 1.57 : 1.95
But, the first length Modal resonance is ~43 Hz.
The first height Modal resonance is ~84 Hz, and the second length Modal resonance is ~86 Hz. So, very close but nothing very bad here for a home studio. We could check better with real dimensions for behind the drywall that is over the cinderblocks, but I think that's not necessary because might not be the culprit.
If we look at this woofer (pic of the linked post), ALPHA 15 A, the mounted resonance (Fsp) is 41Hz. So as a first guess I would say and concentrate in this problem. We have a speaker with 41Hz maximum impedance and a room length with a bad mode at the closest frequency of 43Hz. Usually in other cases a passive series RLC is used (#2) to attenuate the resonance of the driver.
|Today, 11:52 AM||#2|
Join Date: Nov 2003
Location: Brighton UK
That RLC won't do anything unless the amplifier
has high output impedance. 36mH ? a bit big ....
If it has high impedance that will drive the woofer
Q up at Fs, a low output impedance would help.
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
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