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So Weird- No Stylus Contact Woofer Pumping with Hana ML and Elac PPA-2

I observed the weirdest thing I have ever seen in audio. With the cartridge positioned above the record, tone arm locked up and platter spinning, the woofers were pumping on my system. I googled every permutation of query I could think of but came back with no hits. That’s when I decided to video the problem- link below:

Mystery Woofer Pumping

I could type out all the details but the video pretty much covers everything. I thought ya’ll might be interested in this.

 

mitchellcp
mphipps's avatar
mphipps
6 posts
 

The stylus is not on the record. How could it be feedback? The hi pass filter is engaged on the phono pre. 

lewm
13,030 posts
 

If TT is turned off, does problem go away.? If so then I propose that the spinning platter has some iron content and this is inducing a very low frequency signal in the cartridge which is then amplified and affects the woofers.

mphipps's avatar
mphipps
6 posts
 

The video shows that the platter alone does not cause the woofer pumping 

dweller's avatar
dweller
3,781 posts
 

Haven’t heard about this problem for 20 years. I think it has something to do with DC on your AC line. Will have to wait for the experts to return from the Super Bowl tomorrow...

Also, cut and paste the following line into google:

Cause of woofer Pumping in your speaker

mphipps's avatar
mphipps
6 posts
 

Thanks, I checked google- nothing for this issue. The issue being woofer pumping when phono cartridge is within 1/4” but not touching a spinning vinyl record.

Switching to single end puts a stop to the phenomenon. However the question remains- what’s this all about?

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