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Surprising development concerning dust covers on your turntable... [message #12180] Thu, 26 May 2005 07:15 Go to next message
Mr Vinyl is currently offline  Mr Vinyl
Messages: 407
Registered: May 2009
Illuminati (1st Degree)
Hi,

I had posted a while ago that I had a custom dust cover made for my turntable. Just to recap: It is made out of 1/2" thick Plexiglas and fits over my entire turntable which sits on top of a BillyBags Pro turntable stand. This cover also has a hinged top on it so I could open it up like a box and change records etc without having to lift it over and off the turntable. The reason I had this dust cover made was two fold. One to keep dust off but more importantly I wanted a barrier to keep air borne vibration from the speakers effecting the sound of the turntable. Made good sense to me. In any case I had a sneaking suspicion that the dust cover was actually making noise worse. My brother had a good idea. He suggested that I take my Radio Shack sound meter and place it on the platter of the turntable. Play some music and see how many decibles it was recording. Then put the dust cover over the turntable and see if the decibles went down. Which I fully expected they would. I used a Stereophile test cd to play test tones in about 10 different frequencies for my experiement. Much to my surprise the sound level more than doubled and at some frequencies tripled with the dust cover over the turntable. I could hardly believe it. The dust cover was actually amplifying the sound not blocking it. Keeping in mind that this dust cover doesn't touch the turntable in any way. My turntable also sits on a 1.5" thick maple butcher block which the dust cover also doesn't touch. The only thing I can think of to help solve this problem is to add some kind sound absorption material inside the case to soak up reflected sound but I haven't tried that yet. I will probably just leave things as they are since I can't really hear a difference with the dustcover on. I can always take it off for very critical listening if I want. But here is my point. If you have a dust cover on your turntable you might want to try this experiment. I would imagine a dust cover that is attached to the turntable would effect the sound greatly.

Re: Surprising development concerning dust covers on your turntable... [message #12181 is a reply to message #12180] Thu, 26 May 2005 08:03 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Mr. V; AR used to tell everyone back in the day to remove the dustcover while playing records for just that reason. They expressed it this way; the dustcover acts as a giant sail to trap soundwaves and transmit them to the table. It is like an echo chamber.

Re: Surprising development concerning dust covers on your turntable... [message #12182 is a reply to message #12181] Thu, 26 May 2005 08:14 Go to previous messageGo to next message
Mr Vinyl is currently offline  Mr Vinyl
Messages: 407
Registered: May 2009
Illuminati (1st Degree)
Yes, I agree completely but I didn't think 1/2" Plexiglas, that didn't touch the table in anyway, would cause this problem. I am certainly a proponent of removing dust covers from turntables. This was the point of my post. Frankly I didn't think much sound would get through 1/2".



Re: Surprising development concerning dust covers on your turntable... [message #12183 is a reply to message #12182] Thu, 26 May 2005 09:54 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
I don't know if they meant the sound penetrating the cover so much as resonances being excited by the ambient sound then being picked up by the stylus and amplified. It is bad news really because without the cover the static charge grabs all that dust and impacts it right into the grooves. You had the right idea.

Re: Surprising development concerning dust covers on your turntable... [message #12184 is a reply to message #12183] Thu, 26 May 2005 10:56 Go to previous messageGo to next message
Mr Vinyl is currently offline  Mr Vinyl
Messages: 407
Registered: May 2009
Illuminati (1st Degree)
Well, it's great for stopping dust and it also looks really cool. I will use it most of the time and still recommend it. Frankly if it is degrading the sound it is minimal. As I said I can easily take it off if the urge strikes for serious listening.

Re: Surprising development concerning dust covers on your turntable... [message #12188 is a reply to message #12184] Thu, 26 May 2005 19:22 Go to previous message
Russellc is currently offline  Russellc
Messages: 397
Registered: May 2009
Illuminati (1st Degree)
Manual block is right on. It's not the sound that is dectectable inside the cover thats at isssue, its resonance and vibration. Sound in the room can also excite vibrations by stiking the cover which could then be picked by the cartridge/stylus. I would think your extra heavy cover would cut down on this, but it may depend on the resonant frequency of your cover. Everything, even large massive things like the planet, have a resonant frequency. You would still have the echo chamber effect spoken of by manualblock. I find mine sounds best (to me) with the cover up. But I would like a big "cake cover" like that, even with may regular cover on to eliminate dust getting on it. I usually keep a clean T-shirt thrown over it!

Regards, russellc

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