speaker movement with no sound ?

[andyjm]

Just to be clear, of the many problems associated with turntables:

1.If you are standing still and have a rythmic movement of the cones at approximately twice per second, then that is a warp in the record. Most records are warped to some degree.

2. If you jump up and down in your room and the cones move in and out, then that is low frequency feedback - the floor is wobbling the stand which in turn wobbles the turntable which in turn wobbles the platter and arm.

3. Low frequency rumbling sound (hence rumble) is due to the bearings on the turntable, this may produce visible cone movement, but it is much faster than twice per second as is definitely audible.

4. A rythmic hummm at 50Hz that comes and goes once each platter rotation on belt drive turntables where the motor is under the platter is caused by the hole in the platter (to allow belt access) lining up with the pickup and allowing magnetic interference from the motor to effect the pickup.

You can of course have all these problems at once.

 

[SPLOL4]

Thankyou for your input "andyjm"

On tonights menu is mucho stampy and tap tap

I will not be defeated

 

[TrevC]

Just to be clear, of the many problems associated with turntables:

1.If you are standing still and have a rythmic movement of the cones at approximately twice per second, then that is a warp in the record. Most records are warped to some degree.

2. If you jump up and down in your room and the cones move in and out, then that is low frequency feedback - the floor is wobbling the stand which in turn wobbles the turntable which in turn wobbles the platter and arm.

3. Low frequency rumbling sound (hence rumble) is due to the bearings on the turntable, this may produce visible cone movement, but it is much faster than twice per second as is definitely audible.

4. A rythmic hummm at 50Hz that comes and goes once each platter rotation on belt drive turntables where the motor is under the platter is caused by the hole in the platter (to allow belt access) lining up with the pickup and allowing magnetic interference from the motor to effect the pickup.

You can of course have all these problems at once.

Agreed, except that all vinyl generates some subsonic noise, not just warped ones, and no hifi turntable worthy of the description should generate rumble from the bearings.In the old days we didn't notice it because most speakers were of the sealed infinite baffle type.

 

[SPLOL4]

First of all I would like to thank you all for your help

Just finished stomping round my room and tapping everything and the problem is my hi fi rack , I think , I get no cone movement at all until I tap on the rack and my cones go mental .

My local hifi shop has agrred to let me test a couple of isoplats to see if this solves the problem , if not it looks like I will be going back to the hateful metal and glass rack that I could not wait to get rid of , fingers crossed for the isoplats .

I hate metal and glass racks btw

 

[Vladimir]

The rack needs to dig in with the spikes in the floor firmly to transfer the vibrations it receives from the speakers through the air.

 

[andyjm]

The rack needs to dig in with the spikes in the floor firmly to transfer the vibrations it receives from the speakers through the air.

Or alternatively, if the LF problem is being transmitted therough the floorboards, you need to isolate the stand from the floor using a resiliant support.

 

[SPLOL4]

my floor is solid , the rack does sit on spikes , although it is on what used to be a fire hearth , but tapping the hearth gave no cone movement , I only get the cone movement when i tap the reack itself .

 

[Vladimir]

The rack needs to dig in with the spikes in the floor firmly to transfer the vibrations it receives from the speakers through the air.

Or alternatively, if the LF problem is being transmitted therough the floorboards, you need to isolate the stand from the floor using a resiliant support.

Looks like he did just that and the results are shaky. :?

 

[TrevC]

my floor is solid , the rack does sit on spikes , although it is on what used to be a fire hearth , but tapping the hearth gave no cone movement , I only get the cone movement when i tap the reack itself .

Place the turntable on the floor and play a record. If you still get coneflap,which I think you will, it ain't nothing to do with the rack.

 

[SPLOL4]

Just carried out another tap test on my rack .

I started tapping on it from the bottom , nothing , but , as I move up the rack and get nearer to the TT the cone movement gets progressively worse until I tap on the TT plynth and once again nothing , my dog is now wondering have I lost my mind haha

 

[TrevC]

Just carried out another tap test on my rack .

I started tapping on it from the bottom , nothing , but , as I move up the rack and get nearer to the TT the cone movement gets progressively worse until I tap on the TT plynth and once again nothing , my dog is now wondering have I lost my mind haha

 

[SPLOL4]

Trevc are you having me at it ?

 

[SPLOL4]

I will try the floor test , but , first I must eat

 

[TrevC]

I will try the floor test , but , first I must eat

We all have to eat!

 

[SPLOL4]

Well Trevc , I tried the floor test and not only was there no flap , and I turned it up to 11 , but it sounded better than ever , can you get racks made out of solid floor

 

[Vladimir]

Well Trevc , I tried the floor test and not only was there no flap , and I turned it up to 11 , but it sounded better than ever , can you get racks made out of solid floor

Stand made from aluminium hollow tubes filled with sand or attabites will be sufficient.

You can also use a large baking pan, fill it with sand and put the turntable in it and place it on the stand.

 

[TrevC]

Well Trevc , I tried the floor test and not only was there no flap , and I turned it up to 11 , but it sounded better than ever , can you get racks made out of solid floor

OK, I eat my words. You need a much more solid rack.Perhaps a thick oak one, or this

http://www.inner-magazines.com/news/418/57/Compact-Concrete-Equipment-Rack/

 

[JamesMellor]

Hi ,

stupid question , but would it be worth swapping the power amps and the pre / cdp around to maybe stabilise the rack as the upper shelves cause the movement when tapped ? So from the top down TT / Pwr / Pwr / Pre / Cdp

James

 

[SPLOL4]

Hi James

I dont think for one second that is a stupid question , I will try it and let you know .

Hi TrevC

Thats some cool looking concrete