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The Elephant in the Room...

jblnut

jblnut

Don't Overthink It
This has been danced around in a few other threads and I think it's time we call this out and tackle it, once and for all (LOL..as if there could ever be only one thread on a topic here :-).

We all realize on some level that turntables are acoustically sensitive instruments. They are designed to try and minimize the effects of any acoustic feedback from effecting playback. This can be seen as spring suspensions, dense and non-resonant plinths, vibration absorbing feet, etc. It can be taken to even higher levels using mag-lev suspension platforms for example so clearly everyone realizes that sonic vibrations reaching the stylus are bad.

So why then do 99% of us have the turntable in the room with the speakers ? I know the answer is "because that's where the stereo system is", but if you think about it - shouldn't we really solve the problem and get it out of there ? Or perhaps use some system to isolate the turntable from the room's sound ? Tube guys put rubber dampers on tubes to minimize microphonics, right ?

I recalled seeing these back in the day where I worked - they kept the noisy printers quiet. It makes me wonder...wouldn't this also work in reverse by keeping the table in a quiet environment ?

http://www.ergonomichome.com/acprincov3.html

I myself am in the camp of "it's good enough, don't overthink it" and will not be moving tables or trying to cover them. But as I see others go to extreme lengths to isolate their tables with exotic feet and isolation systems based solely on how it sits, I have to wonder - why not tackle the elephant itself ?

What say you and what have you done in this area?

jblnut
 
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So, here's my suggestion for some quasi-empirical data:

Since you (Theo) contend that "seismic" vibrations are a problem and are diminished by your arrangement, it would be quite informative to do some testing:
1/ with motor off and stylus on a disc, what "seismic" noise is apparent; footfalls?; using another source to drive speakers, record phono output-how much microphonic pickup is there? (this could be quantified w/scope or DVOM on AC mV at rec-outs; readings needed before lowering stylus also)

2/ with motor/platter running, put stylus on plinth; how much noise is present? (Expectation would be that at least that much would be heard through a blank groove/playing a disc and thus a measure of "motor noise"/diminished rumble); now measure w/motor off.

While none of this information is absolutely empirically accurate, it certainly would be informative. (and empirically accurate when comparing apples to apples in a given setup)
And, it could be used to make comparisons to other setups if the same recoded material was used and sound level @turntable equalized (smartphone apps are easy)
Maybe someone else will take this on; it would move aspects of this discussion beyond the subjective and IMO be sensible.
 
I put my turntable on a sturdy wall mounted support, on the other side of the room from the speakers. I think that this is an adequate level of isolation, you can turn the volume all the way up with the needle on a record and the platter stopped, without any hint of feedback. Tapping the player itself makes some noise in the speakers, but the wall or anywhere else nearby doesn't.

If your room doesn't allow for such placement, or if your house is made from resonant materials (I've heard suspended floors which are supported from above rather than below in the UK are especially bad), you have options including setting the turntable on a massive block of cement, which will absorb vibrations, using an isolation system consisting of layers of different materials, various spring suspensions, etc.

If you're really interested in this subject, I suggest reading about the methods used to isolate electron microscopes from physical vibration. I was once involved in such a project, and it's just incredible how small of a vibration will totally ruin their results.

I think the best solution is simply to avoid the problem in the first place, as I have done.

N.B. having the turntable in another room doesn't mean much if that room is still affected by vibration from the speakers.
 
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, but if you think about it - shouldn't we really solve the problem and get it out of there ?
Yes, we should.

I forgot about the noise absorbing printer foam...... interesting idea.
 
maxhifi said:
I put my turntable on a sturdy wall mounted support, on the other side of the room from the speakers. I think that this is an adequate level of isolation, you can turn the volume all the way up with the needle on a record and the platter stopped, without any hint of feedback. Tapping the player itself makes some noise in the speakers, but the wall or anywhere else nearby doesn't.

If your room doesn't allow for such placement, or if your house is made from resonant materials (I've heard suspended floors which are supported from above rather than below in the UK are especially bad), you have options including setting the turntable on a massive block of cement, which will absorb vibrations, using an isolation system consisting of layers of different materials, various spring suspensions, etc.

I think the best solution is simply to avoid the problem in the first place, as I have done.

N.B. having the turntable in another room doesn't mean much if that room is still affected by vibration from the speakers.
Click to expand...

But what is the contribution of loud music picked up microphinically? "using another source to drive speakers, record phono output-how much microphonic pickup is there?
"1/ with motor off and stylus on a disc, what "seismic" noise is apparent; footfalls?; using another source to drive speakers, record phono output-how much microphonic pickup is there?(this could be quantified w/scope or DVOM on AC mV at rec-outs; readings needed before lowering stylus also)
 
pfcs49 said:
But what is the contribution of loud music picked up microphinically? "using another source to drive speakers, record phono output-how much microphonic pickup is there?
"1/ with motor off and stylus on a disc, what "seismic" noise is apparent; footfalls?; using another source to drive speakers, record phono output-how much microphonic pickup is there?(this could be quantified w/scope or DVOM on AC mV at rec-outs; readings needed before lowering stylus also)
Click to expand...

That's a very easy test to try, I'm game. Will do when time available..
 
As the OP in this thread, I'd like to keep this on topic - and the topic is not what you put your table *on* but what steps you take to isolate the table from in-room (in the air) sonics.

Please no more links about turntable bases. That has been beat to death here there and everywhere.

Many thanks...

jblnut
 
Here we have an ISI ( Internal Seismic Isolation platform) being installed in an Ultra High Vacuum chamber( no sound waves in there!!) for the LIGO project.:


Why do they bother?
 
If I couldn't watch my turntables whilst playback, half of the fun would be lost...

But I foremost use headphones anyway, so acoustic feedback isn't an issue.

Greetings from Munich!

Manfred / lini
 
I have a raised foundation floor c1954. Had terrible bass feedback loop issue. Personally I want my TT in the room with the speakers so I mounted the TT on the wall using a DIY project I found on Vinyl Engine. I also built an Isolation table from 7/8th thick bamboo cutting board and mounted Sorbothane feet and laid Sorbothane Sheets on that platform then rested my Sansui SR 929 on all that. Maybe over kill but I get zero feedback distortion. I also had some Speaker stands built from Gwiz Products. I highly recommend this company, simple order process and beautiful stands. Still working out the overall main system config but so far so good. Do we ever finish with a system config :D

TT Isolation detail.jpg TT Isolation.jpg

If your interested I can take a picture of the stands and post them?

My .02
 
Most, perhaps. All, definitely not.

If I had an "old school" preamp/receiver with separate record outs (and a working tape deck) it would be fun to do the following experiment:

1) Play a CD or Tuner through the speakers
2) Set Record out to Turntable
3) Set the needle on the record but don't start the motor
4) Start recording the turntable
5) Gradually increase volume (say 3db every 10 seconds) until it gets loud
6) Play the tape back

I will venture that the "base is most of the problem" crowd would hear a lot more than they'd expect on that recording - even those with extravagant support mechanisms and those who don't have a feedback issue.

Anyone have such a setup to test this theory with ?

jblnut
 
My simple answer for why not put the TT in another room would be this - having perfect acoustic decoupling (if such a thing even exists) would be pointless if you can't hear what you're playing, or have to run back and forth between rooms in between tracks. And even if you were pretty quick, you'd probably miss the beginning of whatever you just put on the table.

My setup is relatively simple, and the isolation is more than good enough for me. If I was going to do any serious transcribing, I'd probably use headphones for that anyhow.

My .02,

bs
 
jblnut said:
So why then do 99% of us have the turntable in the room with the speakers ?
Click to expand...
I think because most people of typical income barely have space for things already have and only dream to have dedicated room or closet for tuntable
And even if do it never fails it will not be in right location to do any practical good
I know if I had I would use as you suggest! ; -)
I did do an install when I was teen aged for family living in large colonial home and they actually had a closet to dedicate to turntable it sounded fantastic
I ran the speaker wires under the floors and hid amplifier in built in bookcase small holes in hardwood floors it was a formal home
JJ
 
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