Transmission line spks:Close or far from back wall

I own a pair of Acoustic Zen Adagios which is a transmission line design with an oval port at the bottom of the front of each speaker. Over the 5 years of ownership, I have got a mixed bag of results placing the speakers in an average size room of 12X14 with 8--9 ft ceiling. But, I have encountered again another sound problem as a consequence of placement

I have had them placed 6 ft apart and about 40 inches from the back wall. This often yielded some good sonic results, but I was still generally dissatisfied with the overall performance. A recurrent problem is a somewhat bright over the top sound which can be hollow with reduced definition. Bass is very good. However, to my regret I made some changes which has brought on a new episode of mediocre sound.

1)About two months ago. I changed speaker cables to a brand called Grover Hoffman. There was (almost out of the box) a noticeable improvement in clarity, and naturalness of tone.

2) I replaced a Shunyata Diamondback PC cord with a Panagea AC-14SE supposedly designed for auxiliary compoents like CD players. The Shunyata had a junky plastic IEC female plug that oftem came loose during playback. I noticed a greater sense of loudness with Panagea PC used with the CD player.
3) I had my Ayre CX7e player brought to full upgrade status which is "mp" version. This upgrade was recommended by many members who owned Ayre CX-7e's. The end result was subtle but notable in terms of low end detail and overall coherency. The upgrade seemed to provide also a extended sense of loudlness which I attributed to a somewhat lowered noise floor.

4) I thought the overall sound of the system was good to very good despite few anomalies of loudness and tinges of brightness. Let's cut to the chase.

5)Speakers and components were placed at end of the long axis fronted by a large window, and a glass and wood door that leads to a small outside balcony. On both sides of each speaker toward each corner, a 7 ft bookcase was placed with an equal number of books records and mostly CD's. The right shelf near the balcony has been moved across the room, and down the outside wall placed next to another upright bookcase. Therefore, the right speaker wall has only a world map for sound reinforcement, and an overstuffed recliner several feet from the right speaker which looks forward. I cannot say forsure, but the last change seemd to make me more aware of the speakers new loudness, amd a somewhat over bearing top end, that is, a polar response that was somewhat above the back wall behind the speakers.

6) I decided to buy and use an IsoTek Enhancement disc over last week end. The program ran much quicker. and was quieter in execution of its process. However, yesterday was like Black Sunday, everything I played on the system sounded hard especially piano keys, unmusical and dead with little engagement.

For the record, the listening space I have is 12.5ft X15 feet. TThere is a medium size couch that functions as a room devider between the kitchen/dining area, and the so-called living room. Starting from the couch back to the front door, the room is approx.15X15 surrounded by kitchen cabinets and a 6 ft island counter behind the sofa which I lie to throw out the window.

In retrospect, I don't know what happened to the generally smooth, uncongested and detailed sound that came from the system PRIOR TO SOME, BUT NOT ALL OF THE ABOVE CHANGES.

I have been involved in audio for 41 years, but I am stumped, and at an impasse. Unless, I can improve the sound I have so I can listen contentedly. I have concluded that the system, especially the speakers will be up for sale. I am sure members will agree that a high end system's function is to thoroughly enjoy the music it produces, not wring your hands trying to figure its foibles and faults
I have no experience with those speakers, and I know that some owners really love them, but I have heard other former owners here and on other sites complain about the high end, saying that it wasn't what they expected. (brighter)
It doesn't seem that there is anything too unusual going on in your room, except maybe too much hard reflection from the bookcases.
What speakers have you used in the past prior to these? You front end certainly shouldn't be a problem.
Roxy, Thank you for the comments. I also love the Adagios... "sometimes";....they have great bass, dynamics, and overall transparency... BUT IN THE NEGATIVE COLUMN, they can often sound bright, more so hard, and the sound is less than musical. But I have to join the chorus of members who own them, that yes the highs are a disappointment, not so much as how far they go out, but too often don't sound smooth even on the best of CD's.

I previously owned Silverline Prelude II which took a long time to break in, but were very musical before selling them to upgrade to the Adagios. Prior to that was a pair of Vandersteen 1C which were also good, but not as good as the Preludes. I also owned a pair of Green Mountain Europa's (bookshelf)which were one of my all time favorites.

My first really high end system goes back to 1988 when I had separates, and ran B&W Matrix3 MK II which were in the same league as the AZ Adagios, but also tended toward brightness and could be edgy, I always preferred a speaker with extended highs because I believed they would sound less warm, or less detailed, or simply too soft,especially on classic rock which is what I primarily listen to. . A member told me to check out the Wharfdale Jade 3 monitor or the Devore 3XL monitors ($3700) However, Devore's pricing is off the scope, and he highly recommends his stands to maximize the "sound quality" The stands are wel made, but costs $595.00. So the total investment is almost $4300....that is a bit outrageous. Though, the new line called Scansonic offers a similar monitor, B-1 and recommends their stands at $795.00 Wharfdale Jade 3 come in less money at $1500 for the monitors and only $500 for their stands.
"5)Speakers and components were placed at..."

Are you saying that after #4, you rearranged the room setup? Then sound went south? The room is the most important component. Move it back and get back to the happiness after #4 and before #5.

Otherwise, use a sound meter and test tracks to measure what's going on in the room. Tweak speaker placement and room treatments and remeasure. Search the archives here for many detailed suggestions about first & second reflections and about bass traps to tame bass peaks & valleys. Use the measurements as a guide and trust your ears for final adjustments.

Your gear didn't magically go bad. Starting from scratch is a horrid idea. Take a long walk get in a positive frame of mind and then try to figure out how to make the most of your room setup. Cheers,
Spencer, Thank you for your suggestions. Fortunately, I must have intuited what you were think. I did NOT change everything back to AS IT WAS, but I moved the speakers closer together, make some measurements as to how far each speaker was from the wall behind them( mostly window with blinds behind the right speaker). I attempted to equalize the distance. Lastly, I nixed any toe-in, and set them looking straight ahead. I assumed my 10ft distance from the spot between the speakers would create the required triangle setup. No miracle transformations, but much better than the "Black Sunday" listening session which I referred to above. However, moving them closer together has shrunk the soundstage to only the domain between the speakers, though there seems to be more coherency across the audio spectrum.

It is acceptable to good sound at this point. I may have just found the outer limits of the Adagios's performance , and now want to buy something new,that offers much better overall sound The other pieces, that is, the Rogue integrated amp is solid, but not necessarily the last work word in transparency or top end resolution. The Ayre CX-7e which is fully modded is the real anchor of the system, and I would have to spend 5 times as much of its retail price to better it. Thanks to all; I'll keep you posted.

P.S. I wish a member could provide some details and comments about the Devore speakers in particular the 3XL monitor, the Gibbon 88 floor stander, and possibly the O/93
Sunnyjim, I have and use the isotek disc... I cantl listen to my system after I run the disc until about 24 hours after playing music. The isotek shouldn't be the last disc you run before listening. You need a day of music running through. Don't laugh and try it and seewhat it sounds like.