Modifying drivers.

[Ap]

Was wondering has anyone tried & had any success modifying cheaper drivers.
My thought was to get a pair of inexpensive Peerless 833429 for an mtm & use some sort of damping on the cone, either glue on felt or use a varnish to try & tame the cone breakup.
Any idea what specs will be altered?
Mms, fs & s: what about Qms or Qts? Thanks.

[Bas Horneman]

I modified mcm 55-1870..a la Bottlehead Straight 8. I obviously did not use the same formula Doc B. has...since that is secret.

But Doc did say he uses shellac. So did I..just mixed some fine powdered shellac with the purest alcohol I could find 96% or something...left it a day or 2 and then coated the drivers...I used a very thin layer and I doubt that has altered anything...maybe it is not even enough to damp the nasty resonances the aluminium has. The alcohol obviously evaporates and leaves the shellac on..must weigh absolutely nothing but adds damping...the secret I think is how much to use.

Doc also has some 3m vibration damping tape on the back of the (dare I call them spiders)..

Most people will obviously advise against coating...except maybe for dammar on the whizzer? of a fostex or lowther. For obvious reasons...I mean if it has to much goo on it..you ruin the speaker...

My Straight 8 is not finished yet so I can't comment on the sound unfortunately..not a lot of hard evidence but my advice is to just do it...after all the drivers you want are not expensive... Just don't go expecting the sauce to transform the drivers into the ideal speakers..or speaker drivers as (obviously) it takes a hell of a lot to make a VERY good speaker (Doc B. took YEARS to find the right amount of damping and right amount of drivers) and there are a hell of a lot of parameters..crossover/enclosure etc, etc. If everything fails at least you can say you have tried...and will be a lot wizer to boot. :-)

Maybe would be the best to find a proven design with the drivers you intend using...let the drivers run in for a couple of weeks...and then add a little sauce and see if things improve. If it does not.....well ....you can't go back.

Cheers,
Bas

[Timn8ter]

Speaker Cone Dye

Also, our moderator and many posters over at the Full Range Driver Forum perform driver mods. A few have managed to pull off some success stories, but like Bas said, they spent years working on it. There are some mods that are reversible. Adding non-hardening clay or Blue-Tak to stamped frames, wrapping poly-fil around whizzer cones or glueing felt to the inside "legs" of driver frames for example. Adding adhesives or whatever to cones increases mass and stiffness. Fs goes down, Mms goes up, efficiency goes down and these will have an effect on Q.