buzz from speaker..

I recently bought a pair of Dahlquist DQ-20's. The seller claimed he had just re-foamed the woofers (himself). Upon powering them up (Aragon 8002 amp) I became aware of a mechanical buzz coming from the woofers on bass peaks. The seller told me to "check my wiring"; I knew it wasn't electrical.

I pulled the woofers and sent them to http://www.nealspeakerrepair.com to be re-foamed again. Neal told me the previous owner hadn't glued the outer edge all the way around. When I got them re-installed the buzz was gone in both speakers. And here's the kicker: The bass was far stronger than it had been when I first got the speakers.

Thank you all for your suggestions. I have determined that it is the speaker by switching. I was curious if it is a non-centered voice coil can this be repaired or should I just replace cone?

One possiblity is a non-centered voice coil. If not perfectly centered, you can get mechanical noises, and worse, a dead short to your amp when the VC rubs in the magnetic gap which many amps do not tolerate well. The tolerances here are quite fine. Just because it looks OK from the front does not mean all is well on the back end. Proper suspension is everything. Good luck.

The sound that I am getting is at certain frequencies, so I am sure it is not due to any source amp, pre, etc. I checked the speaker cones all for rips or torn dust caps and the screws to all drivers and all are fine. The woofer cones are all new and I was wondering could it have gone bad, and could the magnet have lost its strength, or even loosened on the back of the driver? I thank you all again for your suggestions.

What are dustcaps ?

I may be way off base with this, but I would first check and make sure your driver screws are tight. If they have worked loose, it could cause such a noise from vibration.

If that isn't it, then try others suggestions. But I would start out with the ultra simple stuff.

I had a similar problem. Try swapping the speaker cables and see if it is truly the speaker, or something up the line. If the buzz goes to the other speaker, you know it is not the speaker. Then you have to start switching interconnects and isolate the problem to the component causing the buzz.
For me, it was the amplifier, which I had repaired and the buzz was eliminated.

one possible cause may be the dustcap. If the glue has failed it may cause a "buzzing" or "farting" sound at certain frequencies. -jz

. I would like to make a correction. It is more like a speaker cone vibrating than a buzzing sound. The sound is mechanical in its sound than electrical.This is all coming from one speaker the other seems totally fine.