Sherlock Holmes needs clues


I have determined by listening to many different solo piano CDs that something unpleasant is happening consistently across all CDs whenever the piano plays in the octave between about 500-1000Hz. The beautiful warm, natural piano sound becomes somewhat thin and tinny, as though the piano needs to be voiced. Both above and below this octave, the piano sounds warm and natural. I would like to isolate the component (or resonance, or room interaction) at fault.

I plan to play Sherlock Holmes a bit - but would appreciate any thoughts people might have to assist with my learning curve.
judit
So who's Dr Wattson over there? That depends I believe on all variables stated above + the AMPLIFIER that often may clip or increas the amount of distortions in 1000Hz piano notes.
This thread turned out to be more fun then I would have deduced. It could also be that Judith's speakers have a crossover in the vicinity of the frequency band in question that may have some negative effects...
I could be wrong but i think speakers are at fault. Once i listened B@W 801, and had similar characteristics as Judit described.
Are these the same speakers/amp that you mentioned under a previous thread? In this thread you mentioned difficulties with orchestral brass... If so I suspect you may have a defective speaker or a poorly designed one. You really need go to a pair of QUAD ESL 63s, 988s, or Soundlabs.
Ivanj, the speakers/amp are the very same mentioned in my orchestral brass question. I believe they are suspect here as well. A move to new speakers/amp is in my future. However, I want to be certain that I am actually treating the correct disease.

Plato, Relevant crossover is at 3 KHz. Your idea is the very first one I checked out.

I put a heavy quilt over my head and one speaker, listened to very near field direct path. Problem is audible. So I am thinking the room is not my problem.

I am going to do some equipment swapping tomorrow.

Some interesting ideas provided here. Thanks.