FRIED C/3 Monitor 6.500" Midbass driver replacement ???

Several options here...

Bud used several different midbass drivers.  Do you have the C/3 or the C/3L aka C/4?  The former are sealed, the latter are true transmission line.  In the end, he disliked Focal most but liked Gefco (defunct, out of Chicago) best, and the last versions employed them.

I recommend contacting Bill Legall of Millersound at (215) 412-7700, whose rebuilt countless drivers over the years.  He  redid two sets of my Frieds (C/3L and Beta), among others.  In fact, I have Bud's own personal pair, and Bill replaced a special hot rod voice coil Bud had Gefco do for himself with a part he'd only seen once previously in all his years, yet actually had on hand!  That will also cost you less than most new replacements.

When we began producing new Frieds in the previous decade, we used Peerless / Vifa drivers.  You can go that route, but I'd recommend considering Shanghai Silver Flute, which I used in some of mine.  ScanSpeak also makes a great replacement in this application, albeit at a far higher cost.  If you want to remain truest to Bud's philosophy, choose the model with the lowest Qts available, which actually goes against almost every other TL follower.  Please feel free to reach out if you need any help

Trelja knows a lot about vintage Fried products. You would be wise to follow his advice.

Thanks for your input Trelja.

The Model I built was the C/3 with the 2 pressure release holes on the front of the cabinet. I later modified the cabinets and plugged the 2 front ports, heavily damped the interior sides after incorporating an extended port the top rear of the cabinet (the port area that was half the area of the driver) approximating a modified line tunnel to relieve back pressure. I could therefore adjust the excursion of the driver and subsequent airflow by increasing the dacron dampening and adding foam filters which I cut for the rear port. I cut off the low frequency signal with an external electronic crossover at 70Hz. The result with the rear venting was airier and more spacious midrange reproduction, better transients and the sonics became more 3 dimensional. Obviously without the crossover, I severely restricted the signal intput to the speakers rather than hyperextend the driver as the XMas was limited. But I digress... 

Upon examination, the tweeters are ScanSpeak's; Model D2008/8512. The ScanSpeak P17WJ00, 6.500" midbase drivers will probably be my choice with little or no internal crossover mods to Bud's original design. I will also consider the Silver Flute W17RC38's.

thanks for helping me confirming my options,
morbius