Bookshelf Speakers that have to be up against the wall

   You've had some pretty good suggestions here. Speaker placement is paramount to making speakers sound as good as they are capable. Sounds like you are restricted to placing the speakers so close to the wall. "Bookshelf" speakers that are rear ported usually have that feature to enhance bass. To calm that interaction with room boundaries (walls etc.) some have plugged the rear ports to minimize close wall reflections. Of course that minimizes the bass response the speaker was designed for. Some add a sub to compensate for the loss in bass.

   You didn't mention the particular speakers you have? Adding sound absorbing material to the back wall or plugging the rear ports of the speaker may or may not improve your sound. You probably want to explore all options before shopping for new speakers. If you must place the speakers so close to the rear wall, shop for ones that are not rear ported.

Note the comment about how some speakers are "voiced" for near wall placement. Anyone can "voice" a speaker to not sound as bad near a wall. All this means is the frequency response is tailored so the speaker actually needs to be placed near a wall to sound best- in terms of frequency response.

But the OP specifically said "they lost most of their imaging." Well, of course they did! Anything else would defy the laws of physics. No amount of speaker design, no "voice" can change the fact the sound coming off the speaker hitting a flat surface so near by is gonna ruin the imaging. Cabinet, bookshelf, wall, does not matter. All the same as far as the soundwave goes. 

Things that will help - increasing the distance by any amount whatsoever, either by pulling the speaker out, or moving things away sideways; absorptive material, ideally something like Owens Corning fiberglass panel (any size, whatever you can get away with) but even something like soft fabric will help; staggering whatever you can, think books pulled out/pushed in different amounts. 

Really good imaging requires speakers being placed about 3 feet away because reflected sounds arriving within about a 3 to 5 millisecond window affect our ability to localize, and sound travels about one foot per millisecond. So anything you can do to eliminate or attenuate reflections within the first few feet of the speaker will have an inordinate effect on imaging.

 

    millercarbon is completely correct! All of those things suggested should be investigated. BUT!!!!!....Are you completely locked in to the placement of your speakers? If so, your options are limited. Even if you replace your existing speakers, the new ones will also offer a challenge as to their placement.

   It all comes down to what you perceive as acceptable sound for you. Your sound "theater" should be what you accept as ideal with what you expect. I still haven't heard what speakers you are now using? Not that it matters so much but it gives a hint as to how improvements may be accomplished.

actually, no....a careful read of my statement about tailoring the polar  response IS not about voicing, its about managing the. amplitude of those early refllections. IF they are down significant db it js the same as being out in the room 3-5’...just physics...

I can stellar image depth with. Vandersteen Treo out 20” from the wall (tweeter to wall) because they are designed for that....of course they get better at 3’ but ...... 

stop by the studio someday and hear the depth of.  image possible out of soffit mounted  set of constant directivity monitors....maybe not mastering quality but fine....for sure...

also see this month’s Stereophile for a review of “ image champs” and a designer who knows how to pull that off...