Subwoofer Woe!

Pike900fish

New member
Jun 23, 2008
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Hi..Wonder if anyone can help me with the problem that's developed with my sub...

It's a Paradigm PDR10 active sub. When I turn the volume (sub level) higher than about 10 o'clock it begins to uncontrollably rumble and increase in volume until I turn it down. The rumbling then stops. I can't take the grill off the speaker (it's a fixed on design) but from putting my hand near the rear port the air movement feels like the speker is pumping in and out in some sort of spasm?

It is connected via the subs single phono connection and to the right high output channel of my NAD preamp. The Frequency level adjuster is set at 50Hz. I find this to be the best balance with my main speakers.

Please help!

Thanks in advance
 
A

Anonymous

Guest
Sounds like it might be sort sort of feedback. Does it happen if you just connect the sub to a line level source on it's own?
 

Pike900fish

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Jun 23, 2008
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Thanks welshboy..i think I've found the problem as it only happens with vinyl..It must be the low level rumble (I think it's refered to as the "wow as in "wow and flutter") which creates some kind of feedback when its bad on some not so flat pressings.

With CD and Homecinema i can crank it up to shake my fillings without any problems! Just have to excercise restrain (respect!) for the good ole black stuff (I appreciate some vinyl is also available in other colours!)

Cheers
 
A

Anonymous

Guest
Pike900fish:
Thanks welshboy..i think I've found the problem as it only happens with vinyl..It must be the low level rumble (I think it's refered to as the "wow as in "wow and flutter") which creates some kind of feedback when its bad on some not so flat pressings.

With CD and Homecinema i can crank it up to shake my fillings without any problems! Just have to excercise restrain (respect!) for the good ole black stuff (I appreciate some vinyl is also available in other colours!)

Cheers

It's acoustic feedback. Try fixing a shelf to the wall and mounting the turntable on it.
 

Andrew Everard

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May 30, 2007
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Or turn the sub off when playing LPs.

The cartridge is picking up the low frequency stuff from the sub, which is being amplified and fed back to the sub and then picked up again and amplified and fed to the sub and so it goes and so it goes and so it goes.
 

Pike900fish

New member
Jun 23, 2008
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Thank you Jim and Andrew,

The Turntable is mounted on a target wall stand with the plinth it sits on isolated by spikes. However the isolating plinth is only cheap MDF. Any views on a more isolating material I could construct a plinth out of..Something like a piece of slate if not too heavy? I do have the wall stand fixed in 6 positions with 3" long size 8 screws so should take a fair bit of weight
 
A

Anonymous

Guest
What turntable do you have? If it feeds back to that extent I would consider replacing it.
 

Andrew Everard

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May 30, 2007
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Jim Highfield:What turntable do you have? If it feeds back to that extent I would consider replacing it.

See OP's signature.
 

Pike900fish

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Jun 23, 2008
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Pike900fish:Tear Drop:Cast acrylic, not the standard perspex, is a VERY good material.

Tear Drop, where can source cast acrylic especially design for this kind of isolation support application?

Also, Jim I've double checked and there are no transit screws left in and I've had the TT from new , 1989.

Thanks
 

Tear Drop

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Apr 23, 2008
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The company I have used in the past are no longer in business, so I haven't got a specific recommendation, but I just googled 'cast acrylic' and 'plastics' and 'perspex' and there are a lot of UK suppliers. A bit of digging and you should find one that will do custom orders for a fair price.
 

Tear Drop

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Apr 23, 2008
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...just remembered a friend of mine had a one-off custom job (turntable sub-platter) done by these guys http://www.plasticonline.co.uk/ which he was very happy with.
 

Pike900fish

New member
Jun 23, 2008
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Tear Drop:...just remembered a friend of mine had a one-off custom job (turntable sub-platter) done by these guys http://www.plasticonline.co.uk/ which he was very happy with.

Thanks again Teardrop
. i'll definitely order some up, I guess the thicker the better and I'll have to come up with a way of protecting it from the spikes?
 

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