You can get aftermarket 4x10. heat etc where they are makes most fail after 3-5 years no matter what brand.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Pioneer makes exact fit replacements for the front and rear. They work great with the stock radios or aftermarket. About $75-100 for both front and rear.
it's amazing that the speakers put out as much sound as they did. May go with some 5.25 adapters and install component speakers. There are lots of opinions on which way to go. I'm sure anything will sound way better than the trashed originals.. Probably a good time to install the Premium Sound System that I found on my last boneyard visit...
I have Aftermarket 4x10 coax speakers for 15+ years and while still sound good the glue on the edge to metal failed after ~ 4 years because of heat... Dash parts can reach 150-200°F when parked and fast too. Most Electronic parts has a max storage temp 150-180°F. Many are less then that. (Cold temp's often don't help either. Speaker parts can become brittle or stiff and break when run like this.)
Fiero Rear speakers get hot too because of location and Moisture Dirt and Ozone won't help them. Old speakers there, after 3-7 years, are often junk too no mater what brand. (Dirt, hair, and worse Cleaning Chemicals get to most speakers.)
OE Radio is "dead" now because heat and age killed caps and other parts and no real interest or money to get a new or good used one. Radio may work but tape died decades age and now clock is always hours off. (I think I even have good GM CD unit but no adapters to use them.)
I did the adapters from BTR and used 5 1/4 component speakers up front. I am have them all fitted in. Have not used them yet as I am still working on everything interior wise but you can not tell from just looking at the dash anything is different.
Pioneer makes exact fit replacements for the front and rear. They work great with the stock radios or aftermarket. About $75-100 for both front and rear.
Front: Pioneer TS-A4103 Rear: Pioneer TS-A4672R
TS-A4103s have always been my "go to" speaker for the fronts of my Fieros. I have compared them directly to the similar Kenwoods, and the Pioneers have much better bass response. One guy (a confirmed Fiero-head) even thought I had the performance sound system. All of my rear speakers (B-pillar, not seat speakers) are the originals. They don't get baked in the sun, and are usually in okay shape, unless they've just been blown out. At least the ones I've found.
------------------ Raydar 88 Formula IMSA Fastback. 4.9, NVG T550
Same here. Thought about a refurbishment of the OEM ones, but passed on that. Thirty years was long enough for the cones. Ended out doing the Pioneers.