Axiom Home Page Forums General Discussion Technical Questions VP150 vs M3(x2)

Maybe you could test (since you have a pre/pro setup) and send pink noise to both your M80s. Measure the level with the SPL meter, then unplug the Y cable from one of the M80 amp inputs and see if the drop is 3 or 6 dB... I'd try this but my receiver will only output the test tone to one channel at a time.

So from all of this I am thinking two M3s in parallel on one amp and one VP150 on a separate amp both from a "y" should be roughly equal.

My vote is YES, an equal 95 dB. When do you get them? You can verify once you are setup I guess. I'd be interested. I would hope you'll get some additional/better input on this too.

dllewel,

You are correct, sir. Running two M3s in parallel from the same amplifier will result in a 3-dB increase in loudness, a change that is sujectively termed "somewhat louder". Six dB is definitely wrong for two conventional speakers run in parallel.

I don't know about the 6-dB thing with the subwoofers, unless it's room gain from corner locations. Will look into it.

Regards,

They are FO so the M3s will be a while. I need an above tv speaker because I find one speaker above or below to be too far off center for dialog. The M3s will give me greater range for a lot of channels that only fire the center and not the mains. If this doesn't do the trick, I will use the M3s as over/under centers and the VP150 for a "between the couch and wall" upward firing back channel.

Thanks Alan.

With my EP500s at opposite ends of the room I have measured an exact 3 dB change by turning the 2nd on/off. Putting them near each other on the same wall I saw that change to 5 dB. Niether were in the exact corners, maybe 3 feet out from each sidewall. It must be the room loading effect with the larger wavelengths the subs work with.

Thanks again. Have a great weekend everyone.

Doug,

I think your plan sounds excellent. With the right setup, you should be able to get the dialog sounding from the center of the screen. And as you said, you'll have a lot of options either way.

Alan,

Craigsub was specific about "stacked" EP500s producing +6 dB, not separated subs.

David,

Thanks for the replies. I am looking forward to the fun! Tracking, unpacking, moving, calibrating, enjoying......

Doug, the general increase for two widely separated speakers fed the same signal at the same power level is 3dB. When the speakers aren't widely separated but are instead "co-located" an additional increase of up to 3dB can be had at certain frequencies. This is more often discussed with respect to subs, for example in this Electrovoice brochure at p.3 under "use in multiples", but the same basic principle applies to all speakers. When their drivers are located less than about one-quarter wavelength from each other they "couple" and the increased pressure that their cones cause on each other at certain frequencies results in higher output. For example, if the center of the drivers is about 1' apart, that corresponds to a wavelength of 1130Hz(sound traveling at about 1130 ft./sec)and one-quarter of that would be about 280Hz, so as much as an additional 3dB increase, for a total increase of 6dB, would be gained under about 280Hz.