2. analog
  3. 1299552220

Woofer sucking in and out

I have a problem with my analogue set up that once it starts play, the woofers of my speaker will move in and out like crazy, unrelated to the music! It relates with volume as when the volume is low, the woofers will not move as much. May it has to do with oscillation between cartridge and arm but my set up is new. The turntable is Acoustic Solid-Transparent and rega301 arm with cardas wiring and weight mods, Herron VTSP 3A pre and VTPH phono. I wonder if placement has anything to do with it or power connection.
I hope someone who has the same problem before can give me some hints.
Thanks.
luna
bright_star_audio
179 posts
 
It is probably not a vibration control / isolation issue.

Barry
ct0517's avatar
ct0517
2,041 posts
 
Bright-star-audio

Absolutely the arm/cartridge relationship needs to be correct. But if you read the post from the OP.

"I have moved my TT to another spot at the back with some success. The movement is not as big as before."

With no other changes to cartridge/arm. This indicates an isolation/vibration issue.
bright_star_audio
179 posts
 
Hi Ct0517,

Thank you for your reply.

I did see that but I still feel the arm/cartride relationship needs to be examined again. Moving the TT probably only reduced the problem exhibited by that relationship.

The low freuency pumping of the woofers is probably not sourced from the speakers because it is much lower than their cutoff frequency. If it is sourced from some other source (like a large ac/heating system or a nearby industrial plant or highway) it can be verified by removing the belt from the platter and lowering the needle into the groove of a stationary record. If those are the source the pumping will be evident. The owner can also start the TT motor to see if that is the source coming up through the platter. If none of those are the source it is most likely an arm/cartridge mismatch or misalingnment.

Best,

Barry
bright_star_audio
179 posts
 
Saw a number of typos in my reply but can't seem to find the edit control.
glai's avatar
glai
446 posts
 
Tuning the resonant freq of cart/arm can damp some vibrations or at least reduce the excitability. It is part of the feedback loop. If the floor vibrates at higher frequency than the reson freq of the cart/arm, it will provide damping. If the floor freq is the same as the arm/cart reson frequency, the effect is amplified. If the floor freq is lower, the carm/cart tuning will not provide adequate damping. See Minus K article on transmissibility of vibration.

Some speakers have output below 20Hz. More so, while the floor will damp a lot of the higher audible frequencies, it may end up moving at a lower frequencies after being excited. Many of us feels the floor vibrates at heavy bass passages but we don't hear the floor playing bass.
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