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Thorens TD145 - Speaker cones move back and forth

Posted: 12 Jan 2019 14:56
by fongio
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 12 Jan 2019 15:16
by Alec124c41
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 12 Jan 2019 17:22
by nat
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.

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 12 Jan 2019 17:41
by fongio
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 12 Jan 2019 18:00
by user510
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 13 Jan 2019 06:51
by fongio
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 13 Jan 2019 14:11
by Alec124c41
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 13 Jan 2019 17:51
by user510
fongio wrote:
13 Jan 2019 06:51
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

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 21 Jan 2019 08:34
by fongio
Hi,
Following Steve’s advice, I have procured and have it shipped to Rwanda a new motor to replace the old one which shaft was still slightly bended.
I have also adjusted (tighten the bolts) the 3 springs beneath the TT plate. The rumbling is slightly diminished but the speakers are still “pumping” if compared to when CD/Reel to reel (Revox A77)/cassette deck/radio are played and… I am still quite afraid of damaging them ☹
I must say that when tapping with my hand on the top of the cupboard where the TT is placed the pumping increase considerably.
When tapping on the top of the cupboard where the TT is placed the pumping also increase considerably.
Do not know what else I can do to solve the problem unless replacing the cartridge (SHURE M95ED) which is new. I tried to apply more weight to the cartridge but…no improvement.
OK. That’s where I am so far.
Cheers
fongio

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 21 Jan 2019 13:54
by Alec124c41
You need something to cut the connection to the cupboard vibrations.
A large cutting board, slab of wood or stone, on top of the cupboard, with something between them, might help a lot. For the "between," try a sheet of rubber or foam, cork, maybe even cloth, to damp the vibrations.
When you tap on the top of this sandwich, it should sound dead, not like a drum.

Cheers,
Alec

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 21 Jan 2019 18:29
by klegier
Try a record weight (if you haven't already.) Otherwise, I am pretty sure your problem would be cured with these:
https://www.amazon.com/FMOD-Crossover-P ... 293&sr=8-2

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 21 Jan 2019 19:43
by poutrew
Yep. I can confirm the FMODS work to tighten up the bass response and eliminate speaker pumping. I chose the 30 Hz FMODS and they have worked out good , but did slightly reduce overall sound amplitude, but I just turn up the volume for that.

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 22 Jan 2019 09:39
by fongio
Hi,
Thanks for all advices. I will try to put a marble board between the TT and the top of the cupboard.
However hard to get the FMODS here in Rwanda 😫.
Steve recommended installing a cartridge with compliance less than 20. I humbly confess this detail is too technical for me and despite looking on internet could not quite understand the meaning of compliance and therefore search for a suitable cartridge. Nevertheless I have a brand new LP GEAR AT95SA (Shibata) since I have a quadraphonic Pioneer QX949 since 1973 😊.
Would you think it will fit in the compliance? Before changing the cartridge I wish, once more to call for your expert and wise advice.
Many many thanks.
Cheers
Giorgio

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 22 Jan 2019 11:27
by tlscapital
fongio wrote:
22 Jan 2019 09:39
Hi,
Thanks for all advices. I will try to put a marble board between the TT and the top of the cupboard.
As 'Alec124c41' I believe that it is crucial for your turntable to have a good anchoring on a sturdy dampened support. Else you'll just get too much of that unwanted vibration loop cartridge pick-up.

So indeed, start with a better/thicker/heavier isolating base for your turntable, then give a sturdy and heavy mass support that has greater inertia and that is vibration absorbant.
fongio wrote:
22 Jan 2019 09:39
However hard to get the FMODS here in Rwanda 😫.
I don't like nor feel the need for such apparels. But as far as I can understand and have read record weights are not good with suspended turntables and it makes sense as it would challenge the suspension of the original springs.

Some clamps are liked by some though. But as 'poutrew' defined it it reduces the sound amplitude, I can't think of it as being an "improvement". Since volume can't really compensate for the loss of "higher frequencies" and dynamic.
fongio wrote:
22 Jan 2019 09:39
Steve recommended installing a cartridge with compliance less than 20. I humbly confess this detail is too technical for me and despite looking on internet could not quite understand the meaning of compliance and therefore search for a suitable cartridge. Nevertheless I have a brand new LP GEAR AT95SA (Shibata) since I have a quadraphonic Pioneer QX949 since 1973 😊.
I think with your AT95SA cart you're in the right ball park. The matching dynamic of a cartridge with the effective mass of a tonearm is crucial for any cartridge to perform optimistically. You'll understand better after some reading on the matter.

Now I couldn't find on the spot it's given dynamic compliance, but as a reference high compliant cartridges do prefer low VTF where low compliant higher VTF. And medium mid VTF. Yours is advised at 2 grams VTF. That = mid = good 4 U.

Re: THORENS TD145 - Speaker cones move back and forth

Posted: 24 Jan 2019 06:34
by fongio
Hi,

I installed a thick and heavy marble plate below the TT. The plate is of the exact size of the TT. Unfortunately it doesn't help in solving the problem :-( In fact touching/tapping on the to of the cupboard the problem of pumping remains.

I will then try installing the new Cartridge AT95SA and see if things will get better. Despite controversial advice I am also trying to procure the FMODS and test them. I will let you know the results.

Wish you all a nice day.
Giorgio