Rerurn to Romy the Cat's Site
In the Forum: Horn-Loaded Speakers
In the Thread: Midrange driver suggestions
Post Subject: Changing driver sound with dopePosted by Paul S on: 1/30/2008
As late as the 1960s every self-respecting hi-fi nut had a "secret recipe" for "speaker dope". My own guru would not give me his exact recipe for speaker dope but insisted that developing the stuff was a rite of passage I had to go through myself.
To make a long story short, I ruined quite a few otherwise-decent drivers by doping the cones and/or putting "dots", "radial lines", "steps", etc. on them with substances ranging from damar varnish and/or expensive artist oils to the "dope" and special "Pactra" paints then used for balsa-and-paper model airplanes.
Such treatment does indeed change the sound. I realized too late that the key to good sound is to start with a driver that delivers good sound/performance in a certain range and then to limit that driver to that range. Too bad I couldn't figure out crossovers and amplification - let alone the horns - suitable to exploit my hard-won "knowledge". I also found it is a rough go to get the right "basis" when starting with smaller than a 10" driver as a "pivot point" for a direct radiator system, and nothing I have done to any smaller driver so far has yielded the balance of weight, texture and color available from a good 10", without the dope, if any of those things seem important.
FWIW, I started "seriously" with 2-way A-7s, trying to get 800 Hz out of 515s and (obviously) trying to run 808s down to meet that, and I also tried the 500 Hz "stock option". I hope it is obvious to all readers that this excercise was doomed from the beginning, and no special type or amount of "dope" was ever going to make it work.
If only for re-sale value I recommend against painting or soaking diaphragms of vintage drivers. If you happen to have a good-sounding vintage driver/diaphragm/cone do not expect it is simply "replaceable".
I think - looking back - that the key to evaluating and developing the "best" a vintage driver has to offer is first tuning into its best rather than trying mainly to mitigate its shortcomings. Yes, its "best" might well be a narrower range than its "specs" indicate; but my experience indicates that ANY sort of doping will kill the best an un-doped driver can do, even if doping "improves certain other things.
As an annoying adjunct, my guru had "doped" 515s that were remarkable in that they sounded great; but they were also very unlike any others I heard before or since.
So, given that you basically get one "treatment" per diaphragm, how much time and money do you have to throw at doping?
Best regards,
Paul SRerurn to Romy the Cat's Site