Help with Infinity IRS speakers.

I write to you because i cannot figure out what causes me a problem in the high frequency (trebble) range.

Few weeks away i bought a pair of brand new INFINITY IRS OMEGA.
I thought I made a very good deal because those were the very last speakers of the IRS series equipped with the true and reknown EMIM et EMIT medium and tweeters, also they were sold quite cheap (around USD $3000 a pair). I saw later that those speakers were heavily price promoted mainly because they were in the inventory of Harman France since over two years (ex-factory
March 99).

First I quickly found out that one of the boomers was not fully connected: those speakers have a double circuit and only one was soldered which caused one speaker to sound with a lot less bass than the other : that was quickly solved . Anyway this incident demontrated that the speakers had not been checked before packing.

After a while I discovered there was some distortions in one of the mediums. When carefully checking the EMIM medium speaker I realised the magnetic bars were corroded (or something like that) and that some magnetic particules (even magnetic powder) were laying against the ribbon . I opened the faulty EMIM speaker, and cleaned the magnets very carefully . After that little
cleaning all distorsions went away. Excellent, i thought, my troubles have ended !

But no !

Now , after some more weeks of listening i realize there is also -from time to time- a distortion in the trebbles on both speakers. It happens on some peaks of cymbals for instance. Not on all recordings, but always on the same signal.

However I cannot make up my mind about what causes this desagreable slightly distorted sound.

Could it be :

- the EMIT technology itself which causes sometimes some distorsions under certain circumstances.
- the EMIT technology that makes the sound a lot more transparent and therefore let me hear some distorsions coming from the rest of the system or from the CD itself. ( I had electrostatics before so that should not be the case as I was used to a very transparent sound in the trebble zone.)
- The Emit tweeters that are corroded the way the EMIM medium was ? (I cant see anything and would not like to play the surgeon again)
- The crossover : could it be affected by inventoty aging ?
I suspect again the bad inventory conditions at Harman to have caused this .
If ever you experienced the same trouble with your IRS Infinity speakers or if you have any hypothesis to share with me, please be kind enough to e-mail me with your recommendations.
I look forward for your help.

Thanks.