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

How would two M3s side by side compare to a single VP150 in terms of loudness at a given dB?

M3 is 92dB / VP150 95dB - (1w/1m In room)

at a given dB? Do you mean which would be louder if you sent the same signal at the same output level to either the 2 M3s or the VP150?

That's the question.

One VP150 would always be louder than one M3. I would guess by 3dB.

Not at the same dB, it wouldn't...

At the same wattage, it probably would be.

My first post should have been "at same watt".

I have been told that if I buy a second EP500 and stack my 500s, they would be 6 dB louder than a single EP500.

Do small speakers work the same?

If you wire the 2 8 ohm M3's in parralell to your amp it would give your amp a 4 ohm load, each speaker would get the same wattage as if you were only running one M3. So at 1 watt, you'll be running both M3's at 92 dB each.

This is the same as doubling the power, which means a 3 dB increase. This is not the same as doubling the loudness, which is 10 dB. I'm not sure technically why co-locating subs gives 6 dB, probably due to the walls in the room. But I think the answer is 95 dB for 2 M3's wired in parallel. Wired in series would be worse off.

You're going to level balance everything anyway right? What I wonder about is the effects of wave cancelation from the dual M3's near each other.

Maybe this is why it's reccomended to put dual centers above and below the screen, separating them by a few feet- but not spreading the center channel out side to side.

Using separate amps connected with "Y" to pre/pro.

One amp for VP150 above screen and one amp for twin M3s below.

Why 2 M3s? One M3 would not equal one VP150 but 2 M3s would. Right or wrong?

BTW. Thanks for the replies. Just trying to learn something.

Maybe it would be better to use the "Y" to split the signal to an used channel. Then calibration would be easier and this would be moot.

From DYI Audio forum:

<<Two speakers hooked up to a single channel will increase 3 dB over one speaker hooked up to a single channel.

I believe that two identical speakers, each powered by a separate amplifier channel playing at 1 watt, will play 6 dB louder than one speaker powered by a single amplifier channel playing at 1 watt.>>

And I would have guessed only 3 dB instead of 6, but again- I'm not sure why co-located subs give an increase of 6 dB.

If your amp supports 4 Ohm loads, then I think you'll get the same power out of one amp with the M3's in parallel, versus separate amps each driving a single M3. Either way the power doubles, yielding 3 dB.

Of course I've been wrong many times. I'm thankful for any clarification so I can learn more. That's the fun part of this hobby, learning something new

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.

Colocating bass drivers is a bit of an inexact science, though... and while you may get overlapping waves doubling expected sound pressures, others may not... at best you'd end up with "4 subs' worth of bass"... at worst you'd end up with a non-linear response throughout the handled frequencies.

And for a bunch of people that pee and moan about speaker response graphs that don't lie flat enough to check a ruler by, intentionally sacrificing linear response for sound pressure seems odd.

But what do I know...? People buy clocks to syncopate their audio systems then play compressed audio files through them.

Bren R.

While balancing channels, I had to lower the M3 centers 6 DB on the HK to have equal sound output as the M22’s. They are positioned horizontal about a quarter inch apart with the tweeters together. I’ll also say that they have a slightly different tone than the 22’s. I initially had the woofers together, but the center channel just seamed to be two ‘wide’ for dialog. Night and day difference (and improvement) with the tweeters together.

The VP150 has the tweeters at the ends, and there are three smaller woofers vrs the two larger woofers running two M3’s.