I believe I have the midrange driver of one of my speakers damaged. But I can't conclusively say this is the case as it is hard to replicate. On most of the music I play there is nothing noticeable. When I do frequency sweep I don't notice any problems either. However one some particular tunes I hear crackling/distortion. This distortion becomes very noticeable when I touch the driver with my finger slightly. On the other speaker I don't hear the same distortion. I know it is not an amp clipping issue as my amps can supply quite a bit more power than what my speakers require.

Could you help me what this could be? Could it be a resonance issue? If I take it to a repair center how can I explain the problem, if it's only with some tunes the problem could be replicated?

I appreciate all your help.

Hi
from your description I guess the voice coil has been deformed. The most common cause would be it became too hot.
if you push it (very carefully, do never push the dustcap!), are there scratching noises when the diaphragm moves? Do they change when your finger changes position?

Thanks for this. Yes when I touch the diaphragm slightly I hear scratching noises. Not always but with these tunes that produce the crackling. Does this mean I should get a recone of this driver? I did not try changing my finger position too much. Let me try and I'll post it here.

Try the old switcheroo: move the mid from one cabinet to the other and see if the problem follows.

If you push at several positions around the dust cap, you will probably notice one position where the scratching noise becomes most articulated. If it sounds the same on every position, the coil probably has lifted off of the carrier.
Do you talk about reconing by the manufacturer? You could also look if your midrange speaker is available at some online auction

I tried switching the channels and the problem is still on the same speaker's midrange driver. I also tried touching the several positions around the dustcap and indeed the scratching noise problem is articulated in the bottom region. So what's the diagnosis?

It is an Infinity Prelude MTS tower. I know the midrange driver costs $100. I could order the driver from Infinity directly. If I give it to an authorized retailer it should cost me about $80 more. But their service is guaranteed for 90 days, if something goes wrong they'd take care of it.

Aaah Infinity
Do you know a recone service that can repair a damaged voice coil? Your speakers should be worth an adequate repair

The diagnosis is: [looking in my crystal ball while burning tibetan incense sticks]
If you don't see any damage at the rubber surround, the voice coil is deformed a bit, maybe at the upper side. Well, this cannot be repaired as easily as a broken surround. I think the whole diapragm assembly will have to be replaced (if this is even possible!)

I don't get it. Isn't the voice coil a part of the midrange driver? Wouldn't replacing that driver in entirety solve the problem?

Yes of course replacing the whole driver will solve your problem. In your second post you wrote about getting a recone. What I understood was that you wanted the speaker driver to be repaired, but this was wrong.