604 styrofoam cone stiffeners

[Elitopus1]

I was browsing ebay and came across this lot of 3 Altec 604B drivers. One of them has some ribs on the cone that the seller describes are "styrofoam cone stiffeners for improved cone breakup characteristics".

Was this a common thing to do? Does it work as described? I have heard of people stiffening a 604 cone with some kind of epoxy but I have never seen these ribs.

Another thought is I wonder how much these 3 604B will go for

3pcs. ALTEC 604B COAXIAL WITH N1000B CROSSOVERS | eBay

Attachment 3468

[BillWojo]

I've never seen it before and to me it detracts from the value, big time.
That said, I'm no Altec expert but I would think if it made a significant improvement that Altec themselves would have incorporated a cleaner version of that mod into the drivers. Looks like a recone is in order.

BillWojo

[GM]

There's myriad ways to control cone break-up and this is one of them, but to do it to now irreplaceable diaphragms, especially ones that respond best overall to doping? Oh well, to each his own, but I seriously doubt any Altec fan will like its flatter/duller 'tone'.

GM

[Elitopus1]

I would use the two good drivers and sell the 3rd. I bet its worth more with the original cone even with the styrofoam braces.
I don't see any reason to really modify the 604 driver itself. You can mod the cabinet, xover, electronics etc and get a much better result.

[bowtie427ss]

I'll take 2, hold the foam please.

At least they didn't make it look like it just had a litter of puppies.

[GM]

My all time fave 'full-range' driver. A pity more weren't made and/or survived.

GM