Acoustic Feedback and Turntable Isolation

It’s amazing what you can learn from a simple experiment.

The other day I noticed that if I stamped hard on the floor in front of the turntable, the vibration produced a rumble I could hear through the subwoofer. So I got to thinking that maybe my turntable is not as well isolated from vibration as I had thought. Also, I recently played host to an audiophile friend who commented that vinyl playback on my system is not as detailed as digital. Could insufficient isolation be the reason? Could audio vibrations be feeding back into my turntable, causing a loss of fine detail?

I determined to do an experiment. I make needle drops of my vinyl records: high resolution digital recordings. (It saves wear and tear on the records, plus I can listen to them in the car.) Usually, I listen to the record as I’m making the recording, playing it back through the speakers at normal listening volume.

If audio vibration was causing a loss of fine detail, I reasoned, this should be audible in the digital recording. So I would make two needle drops of the same record. I would monitor the first through the speakers, as usual. I would monitor the second on headphones. In the first case, the speakers would produce audio vibrations that might feed back into the turntable. In the second case, they wouldn’t. Would the “clean” needle drop be more detailed than the “dirty” one?

And the answer is … yes! My first test was Van Morrison’s Astral Weeks. I have (and love) the Kevin Gray remastered LP. I recorded it twice, first monitoring through the speakers, and then through headphones. On the intro to the very first track, “Astral Weeks,” there is a shaker. On the first needle drop, I could tell it was a shaker, but otherwise it was just a small patch of white noise. On the second needle drop - made with no audio vibrations to feed back into the turntable - I could hear the texture of the sand inside the shaker.

At the very end of Astral Weeks, the track “Slim Slow Slider” ends with a “freakout” section: a number of instruments improvising simultaneously. This happens during the fade-out that ends the record; it's mostly faint. Well, for over thirty years, I’ve thought that the wind instrument played during those few seconds is a flute. (A flute appears elsewhere on the record.) No! It’s a soprano saxophone. All this time I’ve been mistaking a soprano saxophone for a flute, never knowing my error. But now I can hear that it is definitely a reed instrument, and specifically a soprano saxophone.

Do you need to hear this level of detail to enjoy Astral Weeks? Of course not. If it came on my car radio I would enjoy it. However, if you are infected with my strain of audiophile madness, this level of detail is intoxicating. Having once heard it, there is no going back. (A caveat: you might need a revealing system to hear the difference.) So far, every recording I’ve made while monitoring “silently” has brought new clarity and focus to the records I love.

Where to go from here? First of all, I’ve learned a valuable lesson. Not only is my turntable not as well isolated from vibration as I had thought; the whole issue of isolation from vibration was brought home to me in an audible - even visceral - way. Now begins the hunt for a better way to isolate my turntable. (It’s a VPI Aries 3; feel free to reply with suggestions.)

After that, I may experiment with better isolating the speakers themselves. Whatever happens, I’ll report back.

 

This is one of the 'arguments', reasons really, for suspended turntables such as the SOTA Sapphire, Star, and Cosmos. There are other examples such as the old AR XA's and XB's, and the Linn LP12. Some Thorens models as well. Acoustic feedback can be as audible as 'howling' or as subtle as the loss of detail, or the 'muddying' of bass. This explanation is by no means complete. There are many more examples and methods of providing acoustic isolation. Good catch and point on your part.

 

There are lots of posts about isolation. If you are looking for a non-DIY solution at reasonable cost (but not cheap), try Symposium Rollerblocks. I have mostly Aurios in my system, but they are no longer made.

Important -- if your turntable needs isolation, your tube gear, disc player and speakers may also benefit from isolation.

 

Thanks for the suggestion. I don't have tube gear, and no longer use my disc player. But as I said, I will experiment with isolating the speakers. Would the same Rollerblocks work for them?

 

I believe that Rollerblocks come in three different sizes. You probably want the middle size for the turntable, and the heavy duty version for your speakers (unless your speakers are quite small). Depending on the size of your speakers, you could probably try them as an experiment on the rollerblocks purchased for the turntable.

 

You are on a good path. Check Herbie's—lots of useful stuff.

 

I bought one of these for my TT and it has helped isolate and deaden any vibrations from my rack caused by bass

Auralex GRAMMA v2 Isolation Riser

 

Download a seismic app for your smartphone - and see the impact while placed on your plinth as you play music through your speakers. I've had success using that to test some ISO feet that I have on my other table. Great way to determine if your table is picking up the vibration that your stand is experiencing.

 

Even better, put your phone on a record on the platter without the turntable turned on, and then start cranking up the sound from another source like CD and see what happens. My be mind opening, especially knowing that your cartridge is probably much more resolving than the phone. Lots of ways to go from there, some effective, some not, depends on the situation.

 

Do you spin vinyl with dustcover on? Removing dust cover helped reduce acoustic feedback for me.

Seems you need isolation as well though, a sub, a TT that is not isolated from floor, yep.

 

Which app do you use?

 

I use - iSeismometer on the iphone - I'm sure there are a bunch.

Here is an example:

 

I've checked out the Symposium line of products and may get the Segue Iso 80# platform for the TT.

 

Cool! I will definitely try that.

 

It's not the best sort of experiment unless you or someone else routinely (or even only occasionally) stomps on the floor near your turntable.

Isolating a turntable is straightforward for most setups. It would help if you could post a photo.

Purchasing a heavy, isolating turntable platform usually does wonders for many setups. Massif, HRS, and several other companies make heavy, thick, turntable platforms that absorb an awful lot of airborne and furniture/equipment stand-borne energy.

If your turntable is positioned within a foot or two of one of your speakers, re-position the turntable farther away.

If your speakers are floorstanding and aren't isolated, takes steps to either spike them or place them on feet designed for the job. IsoAcoustics makes the Gaia speaker feet that work very well.

If you've got bookshelf speakers that are sitting on the same piece of furniture as your turntable, get the speakers off the furniture and position them on solid floor stands. The best floor stands for any particular pair of bookshelf/standmount speakers should have two or four posts, a base plate that is at least twice the size of the top plate, and a top plate that is at least three-quarters the area of the bottom of the speaker. Spike the stands if you've got carpeting; use hard rubber feet if you've got hardwood or tile flooring.

Ideally, your turntable should not be mounted on top of your receiver or amp or integrated amp. Resonant interference (a very small possibility) and heat (a very big possibility) are the enemies. A turntable motor and a platter bearing that are constantly barraged by radiant heat from the top of a receiver/amp/integrated amp, will dry out prematurely and require lubrication well before their time.

 

Wall mount if possible. My Aries 1.

 

Spikes are the opposite of isolation; they firmly couple the speakers to the floor. I suggest the following low or no-cost experiment to see whether you should be spiking or isolating. Listen to the speakers with the supplied feet (or no feet), and then listen to them spiked to the floor. Which sounds better? If the spikes sound better, leave them on. On the other hand, if the speakers sound better without the spikes, understand that they will sound even better if they are isolated from the floor. Regular speaker feet (or no feet) are just poor couplers; if the speakers sound better poorly-coupled (regular feet) than well-coupled (spikes), they will sound even better if the speakers are isolated with rollerblocks, inner tubes or some other effective isolating method. I don't have experience with the Gaia isolators, but they may certainly be fine.

 

Right. Spiking stands through carpet is the best way of stabilizing the speakers. Isolating the speakers using rigid rubber buttons on each corner of the top plate will do the trick. The point is to create a listening environment and equipment setup that has the least physical effect on the OP's problematic turntable.