Sub output: Is it the woofer size or the rated RMS

>In any subwoofer output, how important is the Watt output versus the woofer size?

This also depends on the frequency range of interest.

The air you need to move quadruples with each octave decrease in frequency.

A driver with twice the area (say a 15" driver versus a 10" driver) can play 6dB louder. A longer stroke often goes with the larger diameter; if that doubled from 12 to 24mm you'd get a total of 12dB more output at low frequencies given enough amplifier power to use the excursion.

At higher frequencies you're limited by the power needed to overcome the stiffness provided by the air spring in the box + suspension; and at the highest frequencies you're limited by the power needed to accelerate the driver.

Stanwal

Some good points, so I'll keep this short:

Regarding Wilson:

(They have Thor's Hammer subwoofer?)...two 15's

Regarding Rel subs:(and in no way intended as a knock)

(Fine subs, but mostly over rated at Audiogon, and probably under rated, at most other forums? To be honest, there has never been a time as now, when so many good subwoofers are in the market, and we are very lucky. The "AUDIOPHILE COMMUNITY" is much larger than Audiogon, and much of the hype around Rel subs stays here, or at least your statement about them " being possibly the best sub available")

Regarding subs, or mains using multiple drivers:

(Multiple drivers give you more cubic inches, they move more air...see the Wilson Thor as an example that works along with your examples. Multi driver subwoofers were not in my subject line, they are a "whole nother subject"...although an interesting one that does bring some advantage, in some systems. My Apogee MiniGrand subwoofers use a pair of 8" drivers in each cabinet, and my VMPS subwoofers use a 12" and 15" driver in each cabinet, and a single VMPS subwoofer, uses only a 12" driver).

Like you, I'm not a hometheater guy...although I wouldn't be without one, and I do enjoy it now and then. My main music system is no longer using subwoofers (except when I play my little MiniGrands). My Duetta Signatures don't need subwoofers to keep up with the MiniGrands, and the large subwoofers rarely came into play, when I did use them for music in the past (so, I thought it a poor return on value)....and I moved them to the movie system where they get more work.

Regarding 20-80hz:

(Two octaves, the first one....one 15" has a clear advantage over one 10" driver in the 20-40hz range)....the winner?, the 15"

(The second octave, 40-80z?...I can't think of any reason, why a single 10" would have any advantage here either)....the winner?, probably an "equal result" at best.

This would seem to give the larger driver an edge?....a 50% win rate at least, while the smaller driver gets no clear win...0% win rate from 20-80hz.

At freq's above 70-80hz, and using a subwoofer at these higher freq's, your on to something, or at least your ear may be....as the small driver, begins to take any advantage away from the larger driver...no rocket science here.

Regarding hometheater subwoofers:

While they do make hometheater subwoofers (I like to call them "west coast subwoofers"....I'm sure you remember the west coast sound)...any "good" subwoofer can reproduce music and movies just fine.

Regarding Quad and subs:

Dipole bass and monopole bass, does not sound the same. In order to mate "monopole subs", with dipole speakers (at least in my experience, and to my ear)...you must use a filter slope that does not allow the sub, to be active above 40-50hz... 70hz max. (lower is always better)....it's not a speed thing at all. While subwoofers do need to be "linear" (except the west coast ones(-:)...they don't need to be fast? If any one driver is playing faster than another, it's playing a different freq. yes?

Any driver only needs to play, as fast as the freq. calls for, and no faster. Large drivers do have a speed limit, because of their size and weight, but 20-80hz is well within that limit for a 15" driver.

So, I'm going to end this short post, and say I agree with you 50% on subwoofers...and 100% on speaker choice...(-:

Dave

>A driver with twice the area (say a 15" driver versus a 10" driver) can play 6dB louder. A longer stroke often goes with the larger diameter; if that doubled from 12 to 24mm you'd get a total of 12dB more output at low frequencies given enough amplifier power to use the excursion.

Also note that since drivers are rated based on total basket diameter and that doesn't grow as much with the rest of the driver the surface area differences are greater with smaller drivers.

An 8.5"/22cm driver can have nearly twice the area of a 7"/18cm driver. (220 vs. 126 cm^2)

I'm not sure if this is relevant, but the flagship Ampeg concert bass guitar amp/speaker cabinet is one of the most popular among rock musicians.

The amp does 300w @ 4ohms. The cabinet has 8 x 10" woofers. Low FR is 58Hz @ -3dB and 40Hz @ -10dB. SPL is a thunderous 130dB.

Here's what Ampeg has to say about choosing an array of 10" woofers over larger woofers:

"Why do we use eight 10” speakers? Because we learned early on that 10” speakers work much more efficiently than fifteens or eighteens—and if you put eight 10” speakers together, you can move a much larger column of air. In fact, you’d need five 18” or six 15” speakers to move as much air as the SVT-810AV! And they simply wouldn’t be able to respond to transient peaks as quickly as our tens."

"And they simply wouldn’t be able to respond to transient peaks as quickly as our tens.""

Smaller dynamic drivers do have an inherent advantage in regards to transients over larger drivers even if disadvantaged in regards to reproducing the lowest octaves.

I've always leaned towards smaller drivers in conventional dynamic speaker designs in general as a result.

For subs, I've heard it done well with both larger and smaller drivers, again depending on the robustness of the overall design more so than just pure driver size.