"blown speakers"

When the vioce coil inside the speaker gets forced beyond it's design parameters.
The coil can be bent, can be partially shorted out...Or melted.
(that inner coil is usually a coil of wire wrapped around a tube form, closely fitted in the magnetic gap. It has to be perfectly round, as the gap is usually very small, some coils are thin, some deep, some very large around.. depending on the design. that coil is attached to the back of the cone or dome of the driver. It rests inside the magnetic field created by the big magnet around the back of the driver.)
The damage can cause a rasping sound, or a lessening of response compared to the other coils. The bent coil can stick in the gap, or the melted insulation can stick in the gap.
The other sort of blown, is the surround is separated from the body of the cone.
Usually that happens with age, but a really serious overdriven speaker can have that happen. along with the inner voice coil being damaged.

Is there a way to test the speaker to see if there is a problem. The reason I ask is that in one of my speakers, when playing very loud, I heard a sudden rasping sound.When I reduced the volume, it sounded ok. It can still play quite loud without the rasping sound, but I dont really want to play it again as loud as it was to see if the sound comes back. IT was really loud, Pink Floyd Dark Side of Moon, Money. Quality amp of 275 watts, playing vinyl.

I would play It but not SOOOOO loud. You might have been clipping the amp. How loud is loud? I play hard rock over 90dbs at times like RUSH with lots of bass with out glipping my amp at all. But I have a Krell FPB 400cx. If you love It LOUD you better have lots of good clean power. Clipping a amp will blow any speaker no matter how good It is. You can never have to much power as long as It's good clean power. LOL

This stuff happens DUDE!!

Hi all ! Sounds like a rubbing voice coil .If you are handy remove the dustcap and manually move the cone in and out . You should see and hear where / what the problem is . Could be off-center ( sometimes fixed by pulling the driver and re-installing upside down ) or debris in the voice coil gap .