Dustcover Blues

Works for me Lew. Obviously, I am having trouble involving the dust cover. It is a first for me and my music habits have not changed. Once I fix the problem the dust cover will be all benefit again:-)

@atmasphere , Actually, because there is no rear wall and I use dipole linear arrays my room is very well behaved. The turntable is adjacent to the listening position. The bass is due to the boundary effect. This happens in almost every room. The table handles this just fine with the dust cover open. I am not putting it in the middle of the room.

I already have four subwoofers soon to be 8. Although they meet the definition of a "swarm" system they are arrayed in a specific pattern for a reason. At any rate the problem is not with the subs. The problem is a resonating turntable and it only happens with a few records cranked to the max. Next weekend I will make that skirt to see if closing off the space under the turntable will stop the resonance. The dustcover is now effectively sealed. Sealing off the bottom will prevent air pressure from having immediate access to the interior of the table.

The bass is due to the boundary effect.

Yes. But it appears you have a standing wave; if you were to break that up the boundary effect might be a bit reduced (that's how it worked out in my room anyway...). From how you've written about this, it appears that if you make just a bit of an improvement the problem would be gone since it only happens with certain cuts at higher volumes. I forgot to ask- what sort of stand are you using for the turntable?

Look at my system page and you can see where the turntable is. It is on a granite slab sitting on a built in walnt equipment/record cabinet (which I made) which rests on a concrete slab. The uprights are 1 7/16" plywood. All the shelves are braced. The entire affair sits in an alcove in the side wall. 

On my system page you can also see graphs of the frequency response at the turntable dustcover up and down. There is a definite rise in the bass but no really big peak or trough. Over 1 kHz the response drops 10 dB with the cover down. 

@atmasphere , see above!

Dear @mijostyn : "" much steeper slope without phase issues. ""

I use first order high-pass and the blend between main speakers and the Velodynes are in " heaven ".

"" It was digital bass management that finally solved this problem ""

not really must be digital IMD goes really low if you cross over 80hz to 100hz and does not needs to be digital.

"" I am working on new enclosures and will use 8 instead of 4 drivers which will halve their excursions. ""

Look, contrary of what you think my take is not more drivers or more subs. What we and you need is proved bass quality performance developed by each driver and that means low bass driver it self.

Velodyne subs are the lower distortions levels in the world. Eacg bass driver in the Velodyne is monitored over 16K times at each second and when the driver distortion goes near the Velodyne limit of distortions impedes that the distortion levels goes up and no matters if the subs are developing 120db SPL.

Quality is the name of the game in overall bass management too.

I understand that you designed and builded your four subs, well maybe needs not more drivers but a different design but I can’t know for sure.

In the mean time enjoy the MUSIC with out dust cover because life is to short and you have not bougth it.

R.

"" On my system page you can also see graphs of the frequency response at the turntable dustcover up and down. There is a definite rise in the bass but no really big peak or trough. Over 1 kHz the response drops 10 dB with the cover down ""

Maybe you are not measuring what you need to measure that can tell you what is going own down the dust cover. You like science then use it in the rigth way.