I don't suppose anyone knows a source of or drop-in replacement for http://www.madisound.com/store/manuals/ns6-255-4a.pdf ?
Discontinued on PE with no clear (to me) replacement.
What is the orginal application?
Thanks. Madi had no definitive answer? I hadn't heard of that driver or OEM untill you linked it.
My google-fu is pretty strong, but alas unless someone has an old stash of these, you'd be out of luck.
Best to post to a few DIY forums. 2017 was the last time anyone had these for sale.
I don't think there is one. Others have been looking. It is very rare to have a drop in replacement for any woofer, mid woofer or mid. The TS parameters are too numerous. The numbers just never line up when different driver are substituted. And that is even before you get to the acoustic response, which also has to line up. S its not going to happen. You have a better chance with tweeters. Sometimes a manufacturer makes an exact copy of an older renowned driver, but that is very rare.
To top it off that driver has some very unusual characteristics.
Bottom line is that unless you can find a good used driver on eBay, it is the end of the road for those speakers, unless the driver can be repaired. What is the matter with it?
Sound of metal-on-metal scratching and significant resistance when I push on it.
This looks like a rubbing voice coil, most probably distorted (overheated or fried) by too much power driven into it.
One of my friends told me that, I believe it was Mr. Bozak, had built a 48 inch woofer. When he tried it, the magnet was so powerful that it twisted the woofer basket!
Yes, you have burnt out the voice coil most likely. However they have a pretty soft suspension, so you might have caused the VC to leave the gap and then become deformed on return by catching on the pole piece.
The thing that was unusual about it, was the lack of a hard break up and then a smooth roll off at about 6 KHz.
Now those speakers claimed to be phase coherent. If that is correct, then they would have first order crossovers. With those drivers you could just about get away with it.
They have a petty high F3 as you would expect form a fairly high efficiency driver. Qts was on the high side, so I suppose the high F3 was made up for with a little excess warmth.
Really that driver would have been much better employed as a dedicated mid range driver. I'm not surprised you have burnt one out.
Sorry, but those speakers have got to the end of the road.