dustcover up, down or off

I bought an MM7 (used with no cover) and replaced the cover with a new MM7 cover. When the cover is down the counter weight starts to hit the cover during the last 1-2 minutes on the last track of each LP, so I leave it open. Stevecham: does this happen to you?

I have an MM7 too and it sounds better with it off.

I used to own a Music Hall mmf 5.1, and noticed within the first month of ownership noticed that it sounded much better with the dust cover removed. What everyone else is saying here is correct: it acts like a microphone and causes the plinth and other components to resonate.

I have a Music Hall 7, and it definetly sounds better with the dustcover removed.

"Seriously, I've seen tt covers that surround and enclose the entire table without being attached. I really like that idea!"

Actually Mapman, that is a good solution, but they tend to be heavy if properly constructed, making them a PITA to use; and really not any better than a hinged cover if the TT is, or can be, fitted with one (not always the case these days ;-) In addition, they need to be fitted with some kind of resilient material around their bottom edges so they don't potentially rattle against the shelf ;-) The bottom edges of even hinged dustcovers should land on something resilient and not right on the plinth.

"Off, but with an acoustical screen around the TT."

Yes, I think I saw this on "Star Trek: The Next Generation" once when Geordi was playing his vinyl. He did not care for digital!

Seriously, I've seen tt covers that surround and enclose the entire table without being attached. I really like that idea!

Off, but with an acoustical screen around the TT.

My Indian Medicine Man (retired) who is regularly hired from me for a dance around my turntable, says: "It depends..."

I've heard many a more mid-fi perhaps setup over the years produce audible, power draining, and clipping causing feedback with cover up and not with cover down, especially in lively rooms with warped records and no low pass filter.

Down is safer in this regard. THat's all I'm saying

I have not had this happen ever since acquiring the Linn Axis 20 years ago.

Higher end rigs are most likely inherently mre resistant to this so I would agree it is probably an issue with some tables and nt others.

I like the Linn better currently with the cover off, but still leave it on and down 90% of the time,

I have in wall wiring runing to speakers in other rooms, so it is pre much a non issue when listening there.

I also think it's turntable dependent. However I think it best to "follow the physics" so to speak.

First let's assume a concrete slab-on-grade floor with a rigid rack or stand, or alternatively, a wall-shelf lag-bolted into a brick/block wall. So much for floor/shelf-borne vibes. I mention this because those mechanical vibes are most always of much larger magnitude than airborne vibes -- and if one is trying to hear differences in dustcover configuration, will muddy those waters. And while we're at it, let's assume zero vibes from the TT itself; except for the stylus wiggling in the groove.

The second thing to consider is the path the vibrational energy has to take, getting from the air to the platter (without any dustcover in the way, for now) where presumably it will muck up your music by causing the platter to vibrate or even resonate.

Now I'm not of the 30kg. platter school but with no dust cover, or an open dustcover, heavier is definitely better, simply because of a large amount of resting inertia - especially true if the chassis is sprung. So far so good?

NOPE! Unless your TT is RIGHT in front of the speaker, and the bottom of the platter is somehow sealed off from the room air (not!) the air pressure will be equal on all sides of the platter, with the pressure wave striking it essentially equally from all sides. So, with the DC up or off (doesn't matter which) the air vibrations will not move the platter (suspended or not) because they impinge on it equally everywhere. BTW, if the DC is up (like a sail?) not a problem. Again, it is struck by sound pressure waves equally on both sides. And one other thing, because most dustcovers have a diagonal dimension of roughly 2 feet, they would only "see" frequencies above approximately 300Hz. Everything lower would flow past them with no effect ;-)

In almost all cases where someone detects their TT 'dancing to the music', the vibration is getting to the table thru the floor or (less often) the wall to which the shelf is bolted.

DC down could be a possible problem IF:

1. The edges of the dustcover fit tightly to the plinth all around. And,
2. There is no opening through the bottom of the plinth to allow easy equalization of the air pressure between the top and bottom of the dust cover. And,
3. The DC is made of unbelievably thin plastic ;-)

Other than that, I don't think it matters - except for one thing: it is a DUSTcover after all! And no matter how clean my records, or my air, if I leave it up during play, some damn piece of crap ALWAYS SEEMS TO LAND ON MY RECORD!

So I close it ;-)
.

It seems to me that it will be turntable dependent. I see that you have a SOTA Comet. I have a 1980's SOTA Sapphire (still works like new :)), and with that turntable it is unimaginable to me that vibrations and resonances in the cover will be transmitted through the base and then the suspension to the platter or tonearm. I can literally pound my fist on the unsuspended base of the table while a record is playing, with moderate force, with no audible effect whatsoever.

While I can readily envision the concern that Mapman expressed coming into play if the cover is up -- airborne sound waves having increased effect on the suspended assemblies.

With a lighter table, or one with a different suspension design or no suspension, it wouldn't surprise me if these tradeoffs balanced out in the opposite direction.

Regards,
-- Al

Never heard the difference in all my years.

CDs sound much better anyway.

You should listen and act accordingly but if you are not sure, I think it is better to leave it down. It can help guard against and reduce rumble/feedback from airborn sound waves eminating from speakers when that occurs. I do not know of a downside in terms of sound quality leaving the cover down on most all tables I've worked with.

FWIW, I keep mine down mostly though I do not hear an audible difference. Sometimes, for convenience, I take it off all together (yeah baby!) because my hinges are just not as taut as they used to be and the cover does not always stay up anymore on its own.

Any turntable I had always was better with the lid off.The lid resonates easily and transfers the vibration to the platter,or record.Different models had different vibration characteristics,but worse with the lid on,up or down.

I agree with what the others have said so far, with one caveat: If there is even a remote possibility that the dust cover could fall down while playing a record, I would either play with it down or removed entirely, as the effect of the dustcover slamming down could easily cause damage to your record and/or the stylus.

My two cents worth.

if you don't hear a difference, do what you want...if you do hear a difference, the answer is the same

Exactly.

but I recently read an opinion

And it was exactly that , an opinion. Nothing more.

What works for one may not work for another person....somethings just have to be tried first before an opinion can be made.

if you don't hear a difference, do what you want...if you do hear a difference, the answer is the same.