Axiom Home Page Forums General Discussion Technical Questions a couple questions about qs8 vs qs4

how big is a large room? specifically, how big does a room have to be to need qs8s as surrounds?

what are the sonic differences between the qs4 and qs8? i know the qs8s extend lower, but do they sound smoother, more detailed, etc...?

if the differences arent that great, and if the room i plan on moving my HT to is considered large, then i can buy the qs4s and save some money for stands.

Hi fong,

An "average" room is typically about 2500 cubic feet--20 feet long by 13 feet wide with, say, 8-ft or 9-ft. ceilings. The latter would be 2340 cubic feet, if my math is correct (assuming 9-ft ceilings).

When you have "vaulted" or cathedral ceilings, things change very quickly. Elsewhere on these boards, a user mentioned he had 25-ft cathedral ceilings (he didn't think he was overdriving his Onkyo receiver; I believe he was). A quick calculation on my part revealed his room volume was about 8,700 cubic feet. I suspect he drove his receiver into clipping and burned out one or both of the tweeters in his surrounds, trying to fill such a large space with high-level sound. If your room was 25 feet long by 15 feet wide with high ceilings, I'd recommend you consider QS8s; otherwise, the QS4s should be fine.

The tonal balance of the QS4s and the QS8s is very similar. The QS8s' titanium tweeter has a 1-inch voice coil, thus it's able to produce higher, cleaner playback levels in large rooms than the QS4, which uses a 1/2-inch voice coil with the same 1-inch titanium dome as the QS8s.

Regards,

Alan, out of curiousity, is there a room size 'limit' for the various Axiom models?
I know this question is obviously sound volume dependant but i am going to ask anyway.
Perhaps we can use the preceeding example for parameters:
e.g. would you suggest buying a single pair of M80s and QS8s for a room that has a 8000+ cubic foot dimension? or would you actually suggest looking for a different speaker?

I have a pamphlet on Angstrom speakers that actually places room volume suggestions on their various models (ie. 950-1700 cubic feet, Modular2; 1500-2200 cubic feet, Modular3; 2000-2800 cubic feet, Modular4 and beyond that, up to 6000 cu ft they get into adding combos together).

I chessroo,

i would rather belive that amp + room size + placement plan would be more accurate way to sell speakers rather than a bold volume size way of measurement which would problablly lead to faulse reviews about the speakers.

thanks alan!

i didnt know the dimensions of the room that is being built in my house (im going use it as an HT room), so i had no idea which surround to get. the qs4 seems to fit the bill, but im a little concerned with its low extension. they only go down to 100hz @ -3db, which would leave a 10 or 20hz gap between the surrounds and the sub. is this an audible gap? and if yes, then is there a way to fix it?

Hi fong,

Keep in mind that the bass extension of the QS4 doesn't "fall off a cliff" at 100 Hz. It's actually -9 dB at 80 Hz. Now, if you set your sub crossover at 80 Hz, it also doesn't just cut off there, it has a slope of about 12 or 18 dB per octave as the sub's output gradually diminishes above 80 Hz. But it's a gradual "slope."

First, this means that the QS4 is still producing bass at 80 Hz, only it's not quite half as loud (-9 dB) as at 100 Hz. Likewise, the response of the sub gradually declines (rolls off), so it's still producing output (but not as much) at 100 Hz. The idea of a complementary crossovers is that the combined roll-offs in output combine to prevent any holes in the response in the "10 to 20-Hz gap" to which you alluded.

Regards,

Fong,

Alan's explanation jibes with my own experience with the QS-4's during both Avia and Sound & Vision calibrations with my system.

I have the QS-4's and the EP-175 sub with the crossover set to 80HZ. During the "subwoofer crossover" tests, there is a smooth transition of the tone from the QS-4's to the sub... no "hole" in the tone that I can hear.

I've been extremely happy with my setup (Epic Master), and it is in a 20X12 viewing room that opens to another 9X8 sunroom. Good luck!

lando

thanks alan and thanks lando622. this has been very helpful.