Turntable rumble?

Having spent a lot more time recently listening to vinyl (after my CDP died) I noticed that I had a fair bit of cone 'excursion' even when the record was playing a quiet section - not anything audible to presumably very low frequency. My turntable (old LP12) sits on a solid wooden shelf in a built in (Edwardian) cupboard, so shouldn't really pick up any vibration from the speakers.

I can only guess that my deck is producing some sort of rumble, although I can't actually hear anything - only the gentle whir of the motor if I put my ear close.

Any ideas? Deck need a service?

 

This could be caused by an arm/cartridge mismatch.
Go to
www.cartridgedb.com/compliance_table2.asp
Enter your arm/cart details.

If your arm/cart combo is outside the green area you've got problems.

 

I assume your speakers are ported. What's happening is the LP12 is reproducing the warp in the record, about 4hz, this is what your seeing as a bit of cone flap. If the speakers were IB, you wouldn't notice it as much.

Nothing to worry about IMHO.

Graham.

 

if it changes with different records I agree .....

other wise when was the last time you checked the main bearing oil ?

 

Cheers for the suggestions chaps.

Yes, my speakers are ported, so you might be right about the cone flap (i'll have to look that up on the web). I do have some solid rubber bungs that I got hold of when experimenting with blockng the ports, so I can try a pseudo infinite baffle configuration to see if it reduces (just out of interest like).

Bearing oil? Never even looked! I will definitely look into this as a matter of sensible maintenance. I believe the deck had been serviced a couple of years before I got it and had little or no further use until I got it, but either way it must be at least 6 years since.......

As far as the arm/cartridge combo is concerned, I don't have the data to hand to fill in that link unfortunately: the arm is a Grace G707 and the cartridge a Linn K5.

 

that should be an ok combo ....

go for a flat lp and see if they still flap ...

if its low oil or no oil you should be able to hear it rumble with your ear near the platter [going round!] without the arm down.

 

Can't hear any rumble at all from the deck, but I'll still look into the oil thing at some point; the LP12 setup is something I've not taken apart or played with despite having thought about it several times. Been too worried about breaking it!

Tried the flattest lp I could find, still got a bit of extra movement, but plugging the ports pretty much stops it, so I guess that's it! Good to know that it's nothing to worry about.

Cheers again everyone!!

 

Setups not hard....but it needs to be spot on with the lp12 [which is more difficult than most ....]

I used to know what oil it was .....but I would suspect that a top quality synthetic motor oil would do the trick ...but not too thick !

theres loads on the web ...or ask the question over on pfm..

 

"My turntable (old LP12) sits on a solid wooden shelf in a built in (Edwardian) cupboard, so shouldn't really pick up any vibration from the speakers."

The LP12 manual states that
"Floor Mounting: Place the deck on a small, light, rigid table, e.g., small coffee table......

WALL MOUNTING ..... the shelf used should be light and rigid, and it should be fully supported by, but not firmly screwed or glued to it's brackets ....

The oil should be OK as long as none of it has spilled out during transportation. Linn make special oil, probably at a special price too. I recently cleaned mine out and put fully synthetic motor oil in.

Hope this is of some help. If you want a copy of the users manual
pm me your details and I can send you a photocopy.

 

Very helpful, thanks dreftar. I have since discovered that I have a pdf copy of the setup/service manual that I must have downloaded from somewhere or other, but thanks for the kind offer.

 

Linn used to be very particular about oil, there was an upgrade of bearing oil once. Cone flap due to record warp was usually dealt with in amps by a v low frequency filter. If yours is the modern non-vinyl-input type, it probably wont have one, but you could fit one if you have the electronics know-how.
Does it affect the sound? If not why worry?
Chris