Audible vibration cause by driver fitting/brace. Any help appreciated

[getaliife]

I have an audible vibration in my Pensils/A7.3. I have been loving these units for several months, but now a vibration has started on one cabinet. I have isolated the problem to the driver fitting/brace, and would appreciate advice to enable a permanent fix and to impove my speaker building technique.

After removing the back I determined that the sound of the vibration changed if I moved the driver brace slightly. Loose driver I thought, but tightening the driver mounts made the problem worse, loosening one of the driver mounting screws has stopped the problem. So, this is where i would like some help.

Is this problem caused by the driver brace being too tight on the driver motor, should the brace be there to only take some of the weight of the driver and should there be a gap between the rear of the motor and the brace, or is the problem because I have a "wonky" brace or driver rebate and I should reshape or pack it to give an even pressure on the rear of the driver.

Thanks for any help you can offer

 

[chris661]

I'd take a sharp knife and take off a bit of the brace material so that it's clear of the driver's magnet, and then use some self-adhesive neoprene foam (draught excluder) to go between the magnet and brace.

That'll give you something that can compress when you screw the driver in, but should cut out rattles.

Chris

 

[grahamgraham]

That's what I'd do.

I'd take a sharp knife and take off a bit of the brace material so that it's clear of the driver's magnet, and then use some self-adhesive neoprene foam (draught excluder) to go between the magnet and brace.

That'll give you something that can compress when you screw the driver in, but should cut out rattles.

Chris

 

[SubSoniks]

As Chris recoomends but use 'bluetack' instead of neoperene as will compress but also fully couple the driver to the brace.

 

[chrisb]

How sure are you that a loose joint between the brace and enclosure panel(s) is not in the mix? My own personal approach -with which other designers & builders might be inclined to argue- is to ensure that the sundry panels composing the enclosure are as rigidly coupled as possible, with as much resilient compliance between the driver and front baffle and driver brace as would be required to avoid over stressing the basket / frames. With the higher degree of self damping engineered into the moulded composite resin baskets of the Alpairs, and Pluvias, it’s very important to not overtorque things - eventually the frames will crack, which considering the tight tolerances between moving voice coil and fixed constituents of drive train, can wreak all sorts of havoc.

 

[planet10]

It could well be that you have the driver screwas too tight. I have had complaints of this in boxes like the FH3 without driver braces.

The screws should only be just as tight as required to hold a real or imaginary washer from spinning.

dave

 

[chrisb]

as Mr Serling used to preface his little melodrama with - long before it was hijacked as a versatile internet, and sometimes hilariously funny meme - "imagine if you will, ..."


I always "pre-tap" the screws for MA drivers, and hand tighten until the compression on thick gasket is as uniform as I can detect - some imagineering going on there too, I guess

 

[getaliife]

Thanks for the help gents. Sorry for the delay but life got in the way of speakers..... Anyway, I'd thought I'd note down what i did as it might help another victim with the same prolem.

1. I noticed that there was play in the brace. After some chipping away at the brace to clear space behind the driver the brace broke away. Not the joint but the first layer of ply seperated.

2. I reshaped the brace to give some space behins the driver and attached self adhesive neoprine to bridge the gap twixt brace and driver motor. Driver attached with hand tight screws

2. Result, vibration cured. All is well again

Thanks again for the help