I agree completely. In addition to real program material, I test positioning with a 360-degree pink noise sweep (off the DVE disc I believe). Using that sweep, I can say the best systems I've heard used 3 identical speakers in identical vertical plane several feet from room boundaries. Unfortunately, I've personally found it's not as simple as grabbing speakers from the same designer. After trying various combinations of JBL S310ii, S-Centerii, S38ii, and S26ii, only the S310ii L/R plus S26ii center performed similarly enough for me to be happy with after EQing with Audyssey Mult-EQ. Now, I'm looking to move beyond happy to thrilled.
My 92" screen is non-AT, so positioning is already a compromise. Based on seating posture, we're fairly reclined, so I opted to raise the screen, get the center tweeter as close to ear-level as possible, and leave the option of a more up-right posture for critical listening. I'll have to do a video tour of my space and attach it to this thread. I'll see if I can get that done tonight, but I'm working pretty late.
I'm not trying to spread FUD about towers with matching centers. Like I said, I made compromises with my setup that others may not want to make, and even with non-identical speakers, I've gotten really close to my ideal. If you're in the market, please let your ears be your guide and don't let my particular obsession for matching fronts become your own.
Audioholics probably has a great article on setting up centers to get them sounding like your fronts. My list is:
-Get the tweeter as close to ear level or matching the fronts as possible.
-Experiment with tilt towards the listeners ears (rubber door stoppers, foam, and/or thick fabric make excellent tools for tilting)
-get it out of your furniture. Set it on top away from boundaries to avoid the "boxy" sound.
-EQ with your AVR if available.
Bear in mind that while 3 identical front speakers is a good idea, it still does not guarantee absolutely identical sound from all 3. There are room acoustic issues associated with each speaker's proximity to the room boundaries, audio furniture, etc. And there are trade-offs - such as if you had to raise the TV because the center speaker is raised, then you could become psychologically bothered by the high viewing angle.
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He could not wait to run this demo for me. Know why? Because all seven speakers had the EXACT same sound on pink noise! I was almost shocked. In other words, the $250 surround speaker sounded the same for tonal balance as the $1500 high end monitor. And the two speakers were designed years apart, with different parts, and even different acoustic configurations! They sounded the same because they were designed and voiced by the same engineer.
So my opinion is that using two different speakers in the 3 locations is not as risky as one might think. And pink noise is a quick and easy way to check for timbre matching yourself.