[James Romeyn]

Please note application before reply.  Surround duty only, side and rear.

3200cf room
In-wall speakers
80 Hz active high-pass crossover
Listener to surrounds 10' side and rear
Receiver rated only for 8 Ohms (low/moderate current), 100Wpc, power amps drive surrounds only (in my personal experience the more difficult the load the worse it sounds)

These in-wall surrounds are normal monopoles, ideal for modern surround formats.  Placement height "just over the listener's head" per Dolby TrueHD instructions (not 2' over head per pre-TrueHD formats).   

Common:
Street Prices: Same
Crossover: 2.0 kHz
Tweeter: 1.5” aluminum dome
Power Handling: 120Wrms @ 100 Hz
Mid bass composition: Mica-filled IMPP
Impedance: 8 Ohm nominal, minimum n/a
Performance Series: Pioneer CST, 3rd from top (unbelievable technology in top level "Elite EX")

Different:
FR: 6.5" 32-40kHz, 8" 28-40kHz
Sensitivity: 6.5" 86 dB, 8" 87 dB

I know, I know, just pick one, right?  That's no fun!  Let's play audiophile.  Crossed @ 80 Hz, what weighs more in overall balance?  The 6.5s mid range clarity or the 8's mid bass and +1 dB greater overall (alleged) output? 

6.5" http://www.pioneerelectronics.com/PUSA/Home/Speakers/Architectural+Speakers/Pioneer+CST/S-IW651-LR
8" http://www.pioneerelectronics.com/PUSA/Home/Speakers/Architectural+Speakers/Pioneer+CST/S-IW851-LR

For reference, mains are two stand mount monitors (improved clones of French ASA Pro Monitor, Dynaudio Esotec 6.5" copolymer and 1" soft dome, 2.2kHz crossover, superb mid range transparency) per channel crossed @ 80 Hz in my Ambiance/Mode Cancelling Array: http://jamesromeyn.com/home-audio-gear/ramca-romeyn-ambiancemode-cancelling-array/

[JohnR]

How do you know the 6.5" has better midrange clarity?

[James Romeyn]

I don't. 

I ordered the 8s.  Couldn't wait.  $150/pr was irresistible. 

[AJinFLA]

Hi James,

I might be too late, but I have the 6.5s buried somewhere. They looked the part and had the right lineage, so I bought a pair for testing. Much to my dismay, they sounded rather bad. Subsequent measurements told the story. Sorry, didn't bother to save them so you could see. I'd be surprised in the 8s fared much better, but I suppose we'll find out shortly .
You did say these were to be surrounds, so all might not be lost.

cheers,

AJ

[James Romeyn]

Bummer.

Yes, only surrounds, but bad is bad.  Never found superb sound by settling.

Any suggestions for in-walls?  Prices for thin on-walls are insanely high, and you're lucky to get 5.25".  Frankly, any box, even a few inches deep, looks ungainly 45" from the floor.  I was surprised that Dolby now specifies surround height "just over the listener's head."

Others that looked interesting were:

NHT iW1 6.5" coax: http://www.audioadvisor.com/prodinfo.asp?number=NHTIW1

Monoprice 6.5" + 5.25" coax, but concerned about 6 Ohm rating: http://www.monoprice.com/products/product.asp?c_id=108&cp_id=10837&cs_id=1083702&p_id=7604&seq=1&format=3#specification

SpeakerCraft 6.5" with rigid anchor: http://www.avworx.net/collections/speakers/products/speakercraft-mt6-one

I considered the $15 Vifa 4" coax @ ApexJr. (used in an M&K speaker) but would prefer two of the same drivers, employing only one tweeter, with lower crossover pole on the separate mid bass, but the load is too difficult for my receiver. 

[James Romeyn]

Thanks AJ for your help.

Wonderful Ebay seller made full refund, hurrah!

Ordered four Polk 625-RT, $150ea MSRP, magnetic micro-perforated grill with super thin flange, silk/composite dome above copolymer 6.5”, 100 and 4.5kHz tuning, low-turbulence port, and (allegedly) easy one-cut drop-in installation.     
http://www.polkaudio.com/products/625rt

4.5 of 5 stars from in-wall/on-wall specialist Andrew Robinson, Home Theater Review:
http://hometheaterreview.com/polk-audio-625-rt-in-wall-loudspeaker-reviewed/

This was an exhaustive search.  After seeing the cosmetic beauty of the new flange-less designs I disregarded the old fashion type with huge flange around the grill.  This is the lowest-cost new cosmetic style with 6.5" mid bass.  Disregard false info @ Retrevo stating this model discontinued.