I have a pair of custom made bookshelf size speakers that I love. They are older speakers that use french made Focal 7" dual voice coil drivers. One mid-bass 7" driver and one tweeter per speaker, with a 7" cone in the back. Unfortunately one of the woofers sounds blown as it now sounds distorted after cranking it up. The drivers are no longer made. I called a few places to try to repair and they dont think they could match the Polyglass paper cone. They could replace with a different material, but the sound will be different. Do you think I could try replacing with a newer model from the same company? My current speaker is dual VC, with a sensitivity rating of 92. These were custom made so I have no idea how differerent woofers would match to the current internal x-over and tweeter. Any help would be great. Thanks

Hi,
Well, fortunately it was the woofer that blew out. The reason I say that is because woofer material should have little to do with accurate reproduction in that frequency range. Since I don't know the model number of the speaker that was discontinued, I can suggest to you what can be done to get a satisfactory result.
1st If you have the model number on the Bass Driver AND Focal has the specifications. Go ahead and match the characteristics using THEIR data. The most important characteristics, besides the size of the driver would be the efficiency of the driver in terms of dB out. And the resonance frequency.
If these two are matched up closely, you should be good to go.
Focal is known to make good drivers, however, if you have to go to another manufacturer and you match the specs as above, then you should still do well.
If you get a newer Driver from focal, some of the characteristics may have been improved upon over the older driver. Such as transient response. If that were improved upon, It wouldn't sound really different, but it would seem tighter in the bass range.
One other thing I suggest. If you do as I suggest above and are pleased with the result, Go ahead and replace the woofer in the other speaker.
One additional point worth mentioning. Many of the foam surround speakers used in the old days in audio have failed because the foam has literally rotted away, as may be the case with your woofer. I know, as I have re-foamed enough of them. If you find a satisfactory woofer with a butyl rubber surround, it will never rot.
That would be the best replacement, as it would be permanent (if you don't badly overdrive it)
I've been an audiophile for most of my life, and I love music. I REALLY feel for you. I think that you will come out this just fine.
I hope this helps you,
Best,
Mark