New system has fatiguing, harsh high frequency sounds. How to fix?


I just purchased my first audio and home theater system (other than a bluetooth speaker or computer speaker system). I use it for listening to music as well as watching movies. It is a tremendous upgrade and I’m enjoying it. It has clarity and detail that I have never heard before. However, I notice a harshness in the high frequency sounds when listening to music.

I would like my treble to be smooth, sweet, soft, silky and gentle. Right now it is the opposite of that. It is annoying, screechy, metallic and harsh.

I am seeking a solution to that issue. From the little I have been able to find on this subject, it seems that room acoustics might be a big part of my solution. Is that true? If not, what is my next step? An equalizer? I can’t see many options for big changes in speaker placement. At most I can move them a few inches or change the angles.

My listening room is about 11.5 feet by 11.5 feet and square except for the doorway in the back corner which protrudes into the room 18 inches x 44 inches. In the room are a bookcase, couch, end table, media center stand (holding TV, center speaker, receiver, disc player and Roku), computer & computer monitor, my speakers (and rear speaker stands), a ceiling fan and that’s about it... I’m describing the room on the assumption that the room (or its contents) are relevant to the treble problem I’m describing. (However, throwing some thick blankets over my TV and computer monitor, as a test, did not change the issue.)

Here are my home theater components:

  • Computer monitor: WASABI MANGO UHD400 40" 3840X2160
  • TV: LG OLED65C7P 65"
  • Receiver: Sony STRDN1080
  • Disc Player: LG UP875 4K BLU-RAY PLAYER BestBuy SKU 5979504
  • Streaming Box: Roku Ultra streaming player (model 4660)
I mention the monitors (and their size) in case they play a role in reflecting sounds.

Speakers:
  • Front 1: Polk Audio RTi A7 floorstanding speakers
  • Front 2: Polk Audio RTi A5 floorstanding speakers
  • Center Speaker: Klipsch RP-250C Center Channel Speaker
  • Subwoofer 1: Polk Audio PSW125 Subwoofer
  • Subwoofer 2: Klipsch R-112SW Subwoofer 
  • Rear/Surround: Polk Audio RTI A3
Speaker Layout: 5.1 layout with two pair of front speakers and two subwoofers.

The front speakers are on either side of the LG TV on the front wall (and near the room corners. The front speakers are angled in. Minimum distance to wall is 10", but measuring straight/parallel from back of speaker to wall is at least 18". From side of speaker to wall is at least a foot (one side of room has 30 inches). There is only 3" between each RTi A5 and RTi A7 speaker.

The rear speakers are behind the couch at each corner and against the back wall.

One subwoofer is in the back corner. The other is midway on the other wall and angled toward listening area.

For music, I usually prefer listening in 2-channel stereo. The dual pairs of front speakers are awesome. (I initially started out with a 7.1 layout but I prefer this layout now.) The high frequency problem exists even in 2-channel stereo. It also exists if I use only 1 pair of front speakers.

Wiring
All speakers are bi-wired, except the center (and subwoofers), which don’t support it. (Not bi-amp’d, just bi-wired*.)

Speaker wire: Mediabridge 12AWG 4-Conductor Speaker Wire (100 Feet, White) - 99.9% Oxygen Free Copper - ETL Listed & CL2 Rated for In-Wall Use

* https://www.qacoustics.co.uk/blog/2016/06/08/bi-wiring-speakers-exploration-benefits/

Banana Plugs:
  • Mediabridge Banana Plugs - Corrosion-Resistant 24K Gold-Plated Connectors - 12 Pair/24 Banana Plugs (Part# SPC-BP2-12 )
  • Sewell Silverback , 24k Gold Dual Screw Lock Speaker Connector
  • Ocelot Banana Plugs, 24k Gold Plated Connectors, Open Screw Type
BTW, my prior speakers were the Edifier e25 Luna Eclipse. I thought they sounded good and I did not remember them having these harsh high frequency sounds. After listening to my new system for a week, I went back to those for a test and they sounded horrible in comparison. The harsh high frequency sounds are much worse, and every other aspect is worse as well. (That shouldn’t be a surprise given the price ranges being compared, but my incorrect memory had been that they didn’t have this issue.)
lowoverdrive
I see nothing but high bias class A solid state amps in my future. According to the NRC, Davis-Besse is operating at 100% tonight so I'd need a microscope to see the amount of fuel leaving the F5 on all weekend consumed. 
The better the sound system, the more you listen to music, the less you leave the house, the less you drive, the less fuel is used. Zero sum energy consumption. Leave the amps on...
@ kosst

For a high fi novitiate such as myself, could you give some examples of high bias class A solid state amps? 
@kosst

Since you seem to like taking to people who know better than you to task,
Not much I can say to someone who has judged a person's abilities or knowledge without even knowing him. If he does that with people, Imagine the judgement he will put forth about hifi equipment he knows nothing about. You talk good theory. But I doubt your experience base. Do you really think that you have more knowledge and experience than the many thousands or millions of  people who know the theory and have been an audiophile for 30-40- 50 yrs and prefer tubes because they think they sound better? Really?
@psickerson RE: "Try Roon..."

Thanks again for that suggestion. I went back and learned a little more about Roon and I also came across HQPlayer by Signalyst.
https://www.signalyst.com/consumer.html

I'm going to investigate this direction. This looks like where I need to go next.

It turns out that "Roon supports Native DSD output on Linux." It's just the Core that doesn't run on Linux, but "two packages are available for Linux: Roon Bridge and Roon Server."

HQPlayer by Signalyst also supports Linux.

I envision that I will use either HQPlayer or Roon, and I'm leaning toward trying HQPlayer first.

I'll start a new thread under "PC Audio" to ask a question about getting started.

I also need to pick hardware that would work with either Roon or HQPlayer.

The HQPlayer page has this helpful hardware list that will be a starting point.

Recommended hardware:
Of those, the Teac NT-503 looks most interesting to me (so far). I like that it has XLR balanced outputs which I can connect directly to my Yamaha P5000S amp.

Which Audiogon forum would be best for asking about these hardware choices (DAC, NAA, etc.)? I'll start a new thread in the appropriate place.

Thanks again to everyone for all the interesting feedback!