Excessive sibilance and edge....treat room?

JMO ... Pc123v’s syllabus and edginess issues are in the mid treble region between 2500 and 5000hz ... they are being created by excessive energy in that region ringing longer than normal ... this is referred to as Long or Extended RT60 or Decay times ... the note just keeps on ringing

Energy travelling up the wall collides with energy travelling along the ceiling at the wall/ceiling interface where the combined two energy in that region are summed together increasing the energy’s output in that region ... this extra energy just sustains the note longer than it should and the perception is Syllabus Edginess Fatigue and Irritation

You need to absorb and reduce that extra energy at the wall ceiling interface and the ringing goes down and along with it all the irritations

Simple test put on a set of head phones and if the syllabus is still there ... it’s your equipment

Pc123v has a very easy fix .. he has a dropped ceiling .. replace hard 2x2 or 2x4 hard tiles with two inches of Owens Corning OC703 or 4 to 6 pound Roxul batting ... this is what everybody uses for their first reflection and bass traps and would be a drop in replacement for the hard tile

First by replacing hard ceiling tiles you will reduce the bounce of the first reflection off the ceiling ... next you will be absorbing much of the energy that travels along the ceiling and collides at the wall/ceiling interface causing the extended ringing and a third side benefit is if there is a air gap between the dropped ceiling and the actual ceiling ... this will act as a bass trap
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"08-31-14: Davehrab
JMO ... Pc123v’s syllabus and edginess issues are in the mid treble region between 2500 and 5000hz ... they are being created by excessive energy in that region ringing longer than normal ... this is referred to as Long or Extended RT60 or Decay times ... the note just keeps on ringing"

"Simple test put on a set of head phones and if the syllabus is still there ... it’s your equipment"

Unless you have actually heard the OP's system, I don't see how you can be so sure its a room issue. Also, the test you list isn't a bad idea, but it is incomplete. If you use headphones, you won't be able to hear the speakers, poweramp, cables and possibly the preamp (depends on the signal path to the headphone amp). If you really want to rule out the room, a much better way to do that is to try the system in a different room and see if the problem still remains. Its more work, but it won't cost anything.

Before I would invest in room treatment. I would borrow a speaker from a friend or maybe the dealer that you purchased the gear from and see if you still have the sssssibilance issue. Borrow a pair that is known to be on the mellower side (Sonus Faber, Spendor, etc.). Or you if that is not an option, see is you take your speakers to another system and see how it sounds. Either way, this might give you more insights on the cause. In my experience, the sibilance issues are more from the gear than from the room.