I had similar room problems: ceramic tile around the fireplace, an opening to the foyer on one side, windows, etc.
Based on my experience ("your mileage may vary"), I wouldn't change anything until the room was at least somewhat under control. I'm using a combination of GIK Alpha Panels and Bass Traps with range limiters. Don't count out diffusion! I chose absorption plus diffusion after trying the Alpha Panels both ways (they can be ordered with cloth on both sides so they can be turned around for either pure absorption or absorption plus diffusion)
I also used a calibrated USB microphone and REW software to really see what I was dealing with, and sent the data to GIK for advice. But clapping your hands and listening to the echo to gauge relative changes works, too.
(I have no business relationship with GIK! I'm just a satisfied customer.)
I'm not at all a fan of the LS50. I had a pair, and even with an all tube system (also tried solid state), the highs could burn your ears out. This was before the room was treated, but in direct comparison to other speakers under the same conditions (JR 149 - cousin of the LS3/5A, Sony SS-M7) they were extremely bright even after trying their matching stands, different room placements, etc. They've received numerous glowing reviews, so maybe I was doing something wrong, but I just couldn't get them to sound good.
Based on my experience ("your mileage may vary"), I wouldn't change anything until the room was at least somewhat under control. I'm using a combination of GIK Alpha Panels and Bass Traps with range limiters. Don't count out diffusion! I chose absorption plus diffusion after trying the Alpha Panels both ways (they can be ordered with cloth on both sides so they can be turned around for either pure absorption or absorption plus diffusion)
I also used a calibrated USB microphone and REW software to really see what I was dealing with, and sent the data to GIK for advice. But clapping your hands and listening to the echo to gauge relative changes works, too.
(I have no business relationship with GIK! I'm just a satisfied customer.)
I'm not at all a fan of the LS50. I had a pair, and even with an all tube system (also tried solid state), the highs could burn your ears out. This was before the room was treated, but in direct comparison to other speakers under the same conditions (JR 149 - cousin of the LS3/5A, Sony SS-M7) they were extremely bright even after trying their matching stands, different room placements, etc. They've received numerous glowing reviews, so maybe I was doing something wrong, but I just couldn't get them to sound good.