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Pioneer PL610 - PL630 Suspention Adjustment - Acoustic Feedback

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platevoltage

New Member
I'v finally picked up an Ikea Lack table as a stand for my rig.
Since then, I have excessive acoustic feedback and woofer pumping.

All of the boots on the spring suspention on my PL610 are toast. They have disintegrated. They are not fixable.

I've set the spring height a number of different ways on this TT to no avail.

Any ideas out there for boot replacement and the setup of the spring sension on the feet?

As this is designed, the feet basically hold the plinth solid and the lower chassis / TT assembly hangs from springs that sit around each of the feet. The spring tension on each foot is adjustable via an acme thread and spring seat built into each of the feet.

Right now my only remedy has been to set the TT on a 1/2" piece of drywall and below that are 4 airbags (the type used as packing material)

I'm in the process of building a inner tube mount with three seismic bearings.

I've heard that this is not optimal for suspended TT though.

I should add that the problem is so bad that the whole TT will "ring" in resonance with bass passages. If I put my hands on the plinth and press down it will stop. The problem is almost gone with the airbags underneath.

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platevoltage said:
I'v finally picked up an Ikea Lack table as a stand for my rig.
Since then, I have excessive acoustic feedback and woofer pumping.

All of the boots on the spring suspention on my PL610 are toast. They have disintegrated. They are not fixable.

I've set the spring height a number of different ways on this TT to no avail.

Any ideas out there for boot replacement and the setup of the spring sension on the feet?

As this is designed, the feet basically hold the plinth solid and the lower chassis / TT assembly hangs from springs that sit around each of the feet. The spring tension on each foot is adjustable via an acme thread and spring seat built into each of the feet.

Right now my only remedy has been to set the TT on a 1/2" piece of drywall and below that are 4 airbags (the type used as packing material)

I'm in the process of building a inner tube mount with three seismic bearings.

I've heard that this is not optimal for suspended TT though.

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Click to expand...

I wish I could help with the boots other than to suggest that you look for a suitable donor. I believe that the PL-100 through PL-600 uses the same boots. That being said, I've had a brace of PL-400s and a PL-200, all of which had toasted boots, and never had that problem.

The thing that jumps out at me in your post is the fact that the problem arrived along with the Lack table. I think your problem may be there. The table appears to be hollow. Is that true? If so, you may have just installed your gear on a great big resonance chamber. :(

John
 
Hi John,
The lack table is made from MDF and weights around 60 pounds.

Previously the TT sat on an antique walnut table that had long thin legs.

Apparently this table damped the resonance well because I did not have the problems before with it.
 
platevoltage said:
Hi John,
The lack table is made from MDF and weights around 60 pounds.

Previously the TT sat on an antique walnut table that had long thin legs.

Apparently this table damped the resonance well because I did not have the problems before with it.
Click to expand...

So, it's solid? There goes that theory! What does it sound like when you rap on it?

John

Edit: MDF is heavy stuff so even if it's hollow it could still weigh a lot. Apparently, it is hollow. Thi is from the Ikea web site regarding the Lack's materials and construction.

product description & measurements
Main parts: Particleboard, Fiberboard, ABS plastic, Printed and embossed acrylic paint, Clear acrylic lacquer
Filling material: Paper
Glass panel: Tempered/safety glass

So, it's paper filled, My guess is it's got corrugated paper stiffeners criss-crossing it much like an MDF hollow core door. That could certainly be pretty resonant.
 
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I would agree with boreas that it has to do with the table, hollow or otherwise. The boots on most of these tts are toast. I have a 610 and a 630 and they are gone on both and I have no complaints, nor have I heard any from others about acoustic feedback. At first I had thought about maybe using pipe insulation as a replacement for the boots, but never got around to it because I have no sonic issues.
 
I hate to get rid of the lack table since it's the only thing I've been able to find reasonably that everything fits on.

This may sound bizaare, but I'm thinking of drilling some acess holes in the botton of the table and filling the voids inside with some spray foam like "great stuff" brand. Wonder if this would quell some of the resonance?
 
platevoltage said:
I hate to get rid of the lack table since it's the only thing I've been able to find reasonably that everything fits on.

This may sound bizaare, but I'm thinking of drilling some acess holes in the botton of the table and filling the voids inside with some spray foam like "great stuff" brand. Wonder if this would quell some of the resonance?
Click to expand...

This may sound bizarre but I was going to suggest that. :) If you get all the voids, or even the majority of them, it should work.

I'd make a series of holes in more or less a grid pattern every 4" or so and squirt the foam in. If you drill more than one hole per void the foam will probably ooze out, not a bad thing.

BE CAREFUL THOUGH. YOU CAN DESTROY THE TABLE IF YOU'RE NOT. THE FOAM CAN EXPAND SO MUCH THAT IT WILL POP THE SEAMS & GLUE JOINTS!

John
 
There is some explanation of how to restore the rubber on those Pioneer feet here in the DIY section http://audiokarma.org/forums/showthread.php?t=92333 . However, if they are pretty bad, then the only choice may be to replace them with others. The inner tube arrangement actually works quite well. There are also feet that can be bought for suspending turntables – years ago I bought some that were made by Audio Technica, that were made with felt and rubber, and were adjustable, and they worked pretty well, but unless you buy used ones, they are hard to find now. Other things that have been tried are several squash balls cut in half, and used as suspension underneath heavy boards that the turntable is on.

The other thing to try is a wall-mounted shelf, which usually works well in reducing feedback.
 
While I was doing a search for some info on a turntable discussed in another thread, I found this description in another audio forum of what someone had used to reduce feedback: "I used arm floaties from Toysrus." So, another option - just head off to the toy store!:D

Edit: A search has revealed that he's a member here (I thought the name sounded familiar!), and he refers to doing it to fix the rotted suspension of.....a Pioneer turntable. See the post here http://audiokarma.net/forums/showthread.php?p=2460851 .
 
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Sorry for the long span between replies, I finally got some time yesterday to work on this.

I think that most of the problem had to do with the PL-610 suspention and the bad boots - they were there for a reason and when they go bad it creates all sorts of strange problems (I think they all have to be bad by now from dry rot if nothing else).

I took each of the springs out and very carfully wrapped them with 3M 130 degree C 69,000 volt splice tape. This is a very soft self vulcanizing tape with the consistency of chewed buble gum (if that makes sense).

This seemed to have worked very well.:music:

The other thing I did which helped a lot (and will contribute to the reliability of the adjustments) is to wrap each of the threads on the adjustable feet with teflon tape. I did this because the adjuster nuts (spring seats if you will) kept backing of and all four would end up all over the place.

I ended up with three good layers of wraps of teflon tape on each thread, just enough so that the spring seat nuts had resistance when threading on.

If you do this make sure after its all back together that you bounce or dribble the platter a number of times to make sure all of the suspention parts are seated where they need to live.

I have the TT on a piece of 3/4" solid oak and a 12-3/4" inner tube underneath.

I originally built a seismic bearing setup but it included a piece of marble tile and did not work well. Any sort of material like that is very resonant and I can't understand why people insist on using marble or glass along with thier turntables.

I've also used drywall underneath and it has worked wel.

I had her cranked up last night and did not suffer any of the normal feedback problems.

The Lack table is still plenty resonant and needs to be fixed. I may fill it up with spray foam this weekend. I've been hesitant though because spray foam is capable of exerting a lot of force as it cures. I guess drilling a lot of "weep holes" in the underside will be the key so the excess foam has a place to go, and I'll shave it all off with a blade when I'm done.

I've thought about filling the hollow core with sand but it sounds messy and may make it explode due to the massive amount of weight added.

Thanks for all of the input.
 
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platevoltage said:
I'v finally picked up an Ikea Lack table as a stand for my rig.
Since then, I have excessive acoustic feedback and woofer pumping.

All of the boots on the spring suspention on my PL610 are toast. They have disintegrated. They are not fixable.

I've set the spring height a number of different ways on this TT to no avail.

Any ideas out there for boot replacement and the setup of the spring sension on the feet?

As this is designed, the feet basically hold the plinth solid and the lower chassis / TT assembly hangs from springs that sit around each of the feet. The spring tension on each foot is adjustable via an acme thread and spring seat built into each of the feet.

Right now my only remedy has been to set the TT on a 1/2" piece of drywall and below that are 4 airbags (the type used as packing material)

I'm in the process of building a inner tube mount with three seismic bearings.

I've heard that this is not optimal for suspended TT though.

I should add that the problem is so bad that the whole TT will "ring" in resonance with bass passages. If I put my hands on the plinth and press down it will stop. The problem is almost gone with the airbags underneath.

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Click to expand...

Great looking system. and I see your in my neighborhood.

I live in Boardman.........
 
platevoltage said:
Thanks! I leave right up the street in North Lima.

Mark
Click to expand...

Wow we should get together and pick each others brains about audio. Most if not all of my audio buddies live far away and the phone and e-mails is about the extent of my talking with them..........

I have a PL600 I haven't done anything to it but reading your post makes me want to fire it up and do some adjusting of the suspension............
 
Properly restored, you can put a PL-630 on top of your speakers and crank them, with no feedback. That being said, there is only so much turntable suspension can do. If the table that your PL-630 sits on resonates at lower frequencies, and you have no damping in the turntable suspension for that range of resonance, you will have issues.

The rubber boots over the springs do not hold the feet on, like the PL-518. But they do provide spring damping. If you cannot restore the boots, you will have to supply some other kind of damping. The spring tension is NOT adjustable. The adjustment is for suspension throw balancing. What you do is set the adjustment so that you can dribble the platter up and down, and it tends to max out top and bottom equally.

Now to damping...What you need is to fit a strip of open-celled yellow uphostery foam between the spring coils. What you do is coil it parallell with the spring coils, fitting the foam strip in between the spring coils. If you want the foam to last longer, impregnate it with a "very light" amount of light machine oil. You want your strip of foam to be just big enough to be somewhat compressed by the spring coil as you wrap it in. This will damp out suspension oscillation. If it does not solve your problem, your problem is not in the TT suspension.

Rubber tape is to stiff fo use for the purpose here. You will stiffen out the excellent suspension that the PL-630 is known for.

Enjoy,
Rich P
 
pustelniakr said:
Properly restored, you can put a PL-630 on top of your speakers and crank them, with no feedback. That being said, there is only so much turntable suspension can do. If the table that your PL-630 sits on resonates at lower frequencies, and you have no damping in the turntable suspension for that range of resonance, you will have issues.

The rubber boots over the springs do not hold the feet on, like the PL-518. But they do provide spring damping. If you cannot restore the boots, you will have to supply some other kind of damping. The spring tension is NOT adjustable. The adjustment is for suspension throw balancing. What you do is set the adjustment so that you can dribble the platter up and down, and it tends to max out top and bottom equally.

Now to damping...What you need is to fit a strip of open-celled yellow uphostery foam between the spring coils. What you do is coil it parallell with the spring coils, fitting the foam strip in between the spring coils. If you want the foam to last longer, impregnate it with a "very light" amount of light machine oil. You want your strip of foam to be just big enough to be somewhat compressed by the spring coil as you wrap it in. This will damp out suspension oscillation. If it does not solve your problem, your problem is not in the TT suspension.

Rubber tape is to stiff fo use for the purpose here. You will stiffen out the excellent suspension that the PL-630 is known for.

Enjoy,
Rich P
Click to expand...

Rich,
The rubber tape I used was perfect for this application. It has the consistency of bubble gum. The springs are able to move freely when stretched by hand because the tape is very soft. If it would not have worked, I would not have posted results here. I've listened to it for two nights in a row, last night from 8Pm to 1Am and it did not miss a beat - I played some Bass heavy music too to really put it through the paces.

Your silicone "augmention" repair is unrealistic because you cannot fix crumbling rubber. Maybe if you had a boot that had a rip in it or something like that, but most rubber from this era is going to be deteriorated beyond the point of repair. Rubber to exposed to air and the enviroment naturally deteriorates over time.

I offered it as a solution to fix a problem that worked. If your boots are bad a roll of the 3M 130C tape can be had for $7.00 online. If it doesent work for you than you are only out $7.00

I think it's even more imprtant to keep the spring adjuster seats in place and the teflon tape worked perfectly for that. Time will tell if they stay put. Previously every time I took the TT apart, all 4 spring seats were at different levels (presumeably from vibration) If the seats end up at different heights, the suspention is never going to work right.
 
I have the PL-610 and like it very much. Fortunately (believe it or not) the boots on mine are still intact and in very good condition. The PL-600 I used to have, not so much.
 
Stanton681EEES said:
Wow we should get together and pick each others brains about audio. Most if not all of my audio buddies live far away and the phone and e-mails is about the extent of my talking with them..........

I have a PL600 I haven't done anything to it but reading your post makes me want to fire it up and do some adjusting of the suspension............
Click to expand...

Do you buy vinyl from Sach in the old McCrones on the weekend? I'm generally always there sometime between noon and 1 on Saturday.
 
platevoltage said:
Rich,
Your silicone "augmention" repair is unrealistic because you cannot fix crumbling rubber. Maybe if you had a boot that had a rip in it or something like that, but most rubber from this era is going to be deteriorated beyond the point of repair. Rubber to exposed to air and the enviroment naturally deteriorates over time.
Click to expand...
I have responded to your request for help, providing experience accumulated over a long period of time. The PL-630/PL-610 line is a good part of my bread and butter. I am familiar with the tape you used. In order to function it must be stretched tight. The results are much stiffer than original. Just because you solved your issue over the narrow range of resonance frequencies, does not mean you have retained good performance over the range of frequencies that the PL-630 was designed to be immune to.

Broken up rubber boots are simply a puzzle to be put back together with cyano-acrylate, then supplemented with RTV. If too broken up to repair the boots, the foam strip solution is very close to original in resonance immunity. But then, I have only fully restored about 50 PL-630s this way. I guess maybe your right.

Your gear. You may do as you wish.

Good luck,
Rich P
 
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