Hi davekro,

I've been following this thread and here are a couple of points. Get rid of this idea that matching woofer sizes between different speakers, especially different brands, will somehow creat a better timbral match. Slight adjustments in the crossover of a given speaker create far more audible differences than any combination of different woofers. And I urge you not to use the BIC speakers in an Axiom-dominated system. From my experience as an audio-video magazine editor for many years, in the course of which several BIC models were tested, I can assure you that a BIC will audibly stick out or make its presence known because of inherent coloration.

The reason that Axiom does not make a dedicated in-ceiling speaker is first, that isn't how movies are mixed and meant to be played back and our hearing is much more acute to side-generated and front-generated sound and reflections. Most movies are mixed in 5.1; the decoder will interpolate material for the additional two channels at the rear from the discrete left and right surround channels. Two extra surrounds certainly improve coverage and envelopment in large rooms, however, the QS8s are so effective in their side locations, that often adding two more surrounds yields only a marginal improvement. I don't know why Brent suggested M2s at the rear; if you want 7.1, then add an extra pair of QS8s. They don't need to be 16 feet apart. Ten feet will certainly be enough for ample separation.

Axiom has made provision for mounting a W22 in the ceiling if that's the way you want to go. I also advise against swivelling tweeter designs. After measuring some of these in our anechoic chamber, they had intrinsic flaws large enough that we rejected that design approach.

As to impedance, even entry-level Denons will drive our 4-ohm M80s with no problems so long as you don't drive the Denon into clipping or distortion. The sensitivity differences between the M60 or M80s and the QS8s are not so great that you can't compensate easily with the individual channel levels in the Denon setup.

And in terms of power requirements, I always urge buying as much power as you can afford so there's no danger of exceeding the output limits of your amplifier and damaging the speakers. Your existing Denon should have ample power for very loud playback (95 dB to 100 dB SPL peaks) given your listening distance. If you are into extremley loud (above 100 dB SPL) playback, you could always add a powerful outboard amplifier later on. And has been pointed out, if you want a "slightly noticeable" increase in volume levels (3 dB), you'd need twice as much power (180 watts per channel, assuming your Denon would be driven to near-clipping to achieve 100 dB SPL). To subjectively increase playback volume to "twice as loud" requires ten times as much power.

A note on distortion: virtually all amplifiers have measurably greater distortion driving a 4-ohm load because more current runs through the output section, and it runs hotter. That said, we are talking about fractions of a percent, minuscule levels that are inaudible with music or movie programming. Distortion has to rise to greater levels than 1%--often 3% or more--before it becomes clearly audible. Those levels of distortion do not happen with modern well-designed solid-state audio amplifiers when they are not driven into clipping. They do happen with some tube amplifiers and are quite common with vinyl playback--and it's clearly audible when it occurs.

Regards,
Alan

Alan Lofft,
Axiom Resident Expert (Retired)