THORENS TD145 - Speaker cones move back and forth

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fongio
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THORENS TD145 - Speaker cones move back and forth

Post by fongio » 12 Jan 2019 15:56

Hi all,
When I play any 33 record on my Thorens TD145 the speaker cones move back and forth quite extensively/abnormally. This is worrying me as I am afraid to damage the speakers :( .
This problem does not happen when playing any other support i.e. CDs, cassettes, radio etc.
Any advice on what could be the problem?
Thanks in advance.
Fongio

Alec124c41
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Re: THORENS TD145 - Speaker cones move back and forth

Post by Alec124c41 » 12 Jan 2019 16:16

If you have a rumble filter on your amp, use it.
You might be getting low frequency acoustic feedback. Keep the turntable away from the speakers.
Remove dust cover.
Use your fingertips to detect any vibrations in the turntable, bottom of turntable, shelf the turntable is on.
If the bottom of the turntable is thin, try removing it, or replacing it with a thicker piece of board.

Cheers,
Alec

nat
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Re: THORENS TD145 - Speaker cones move back and forth

Post by nat » 12 Jan 2019 18:22

You might consider the arm mass/cartridge compliance interaction. What catridge are you using? The 145 arm isn't particularly massy, but if you have a very compliant cartridge, you might have some low frequency resonance that is causing the pumping.
I'm not one of those who obsess about this issue, but since it is a possible source of the problem, it's worth checking.

fongio
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Re: THORENS TD145 - Speaker cones move back and forth

Post by fongio » 12 Jan 2019 18:41

Hi, Thanks for your inputs.

I am using a SHURE M95ED.
I removed the dust cover: no improvements.
Turntable quite far from speakers.
Cannot detect any vibration in the turntable.
Haven't tried yet to remove the bottom of the turntable yet. Will try tomorrow.

That's for now.
Cheers
fongio

user510
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Re: THORENS TD145 - Speaker cones move back and forth

Post by user510 » 12 Jan 2019 19:00

I'm with nat on this thread. And I've seen woofer pumping with my TD160C. Effective mass of the TP16 tonearm is 16g. When high compliance cartridges were mounted to it (and among those some Shures) I often times did see some woofer pumping. The problem would go away when I had a better compliance match-up between arm and cartridge.

And I should add that in those instances where woofer pumping was happening I was also on a flexy suspended floor. In that environment taking a step anywhere near the turntable would agitate the arm/cartridge into movement which in turn would create motion of the woofer cone (you could see this when speaker grills are off).

It seemed mysterious and almost other-worldly. But as noted above, the problem goes away when you have a more acceptible compliance match between arm/cart. Aim for the 8hz - 12 hz range. Try a cartridge with a compliance rating under 20.

-Steve

fongio
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Re: THORENS TD145 - Speaker cones move back and forth

Post by fongio » 13 Jan 2019 07:51

Thanks Steve for your precious advice.

Do you have a specific cartridge responding to your specifications to recommend?
Living in Rwanda won't be easy to find :-) but could ask friends to procure one in Europe.

I read somewhere, can't remember where exactly, that tightening the spring below the plate, could Help solving the problem. What do you think?

I also have a problem that did not talk before. The motor shaft was bended during transport. I managed to adjust it (following the excellent advice from the members of this forum). However is not completely and perfectly straight. Do you think could be a source of problem?

I thank you all guys for your support.
Cheers
Fongio

Alec124c41
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Re: THORENS TD145 - Speaker cones move back and forth

Post by Alec124c41 » 13 Jan 2019 15:11

Using a pencil to touch the side of the pulley, and tapping against a small block of wood placed where the pencil mark shows, using a small hammer, or a wrench, to tap, you should be able to get the shaft almost perfectly straight.
Yes, a cartridge with a stiffer suspension would be a better match for a 16 gram EF arm.

Cheers,
Alec

user510
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Re: THORENS TD145 - Speaker cones move back and forth

Post by user510 » 13 Jan 2019 18:51

fongio wrote:
13 Jan 2019 07:51
Thanks Steve for your precious advice.

Do you have a specific cartridge responding to your specifications to recommend?
Living in Rwanda won't be easy to find :-) but could ask friends to procure one in Europe.

I read somewhere, can't remember where exactly, that tightening the spring below the plate, could Help solving the problem. What do you think?

I also have a problem that did not talk before. The motor shaft was bended during transport. I managed to adjust it (following the excellent advice from the members of this forum). However is not completely and perfectly straight. Do you think could be a source of problem?

I thank you all guys for your support.
Cheers
Fongio
Not any particular cartridge. However when looking for cartridges, and you can look at many within the cartridge database here at VE, pay attention to the spec sheet that comes with each cartridge. More specifically, look at the compliance value on that spec sheet. If to match up with the TP16 (mk1) choose a cartridge with a compliance value that is less than 20.

re:bent motor shaft. Well that doesn't Help matters but it should be treated separately. And it is serious. See post above about shaft straightening. If it were mine I would be looking for a replacement motor.

re: spring below plate...... There is a suspension system that isolates the platter and tonearm from all supporting surfaces. This system may be adjusted and tuned but the term "tightening" does not apply.

-Steve

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