Eh hem!...Subwoofers... What do ya know?

Do you have any experience using the Crawl Test for anybody locating less than four subwoofers?

This is the one where you put a sub in the listening spot and walk or crawl around looking for where the bass is best, and that's where you put the first sub. So there's your answer. Because the first step is simply repeated again and again until you run out of subs. 

I did try this and unsurprisingly all the best bass was in the corners. Which anything else would have been a surprise. Bass is always stronger near the walls than out in the middle of the room. No wonder when Tim did this he wound up with speakers in the corners. But that's not hardly even the point. The real point is Tim has great, awesome, impressive, bass that continues to please after many years, and with both movies and music. He does move his chair for music but that only goes further to emphasize the point that having a DBA means having great smooth bass that is not fussy when it comes to speaker or listening locations.

Thanks for sharing your knowledge. How would you determine crossover frequency and gain with less than four subwoofers?

Same as always- by listening! 

Oh, you can use meters too. But there's a problem with that. A really big problem. One that far as I'm concerned kills the whole idea of EQ. That being, meters measure sound all nice and flat and without regard to volume. But people don't hear like that. Really low frequencies we don't even hear at all until they get fairly loud. That's why they made the Loudness switch! Don't believe me? Look up Fletcher Munson Loudness Curves.

Got it? All those lines on the left pointed up and converging? What this says is, if you set your bass to measure flat, you will indeed be able to get it to measure flat, but you will NOT be able to get it to SOUND flat except at one volume level. Then even if you get it to sound flat, it will only ever sound really flat at that one volume level. Turn it up, it will sound like more bass. Turn it down it will sound like less. 

The only real solution is to listen. Listen a long time, and to a lot of music. Listen at or close to whatever volume level you use when you really want it to sound good. Tweak tiny amounts until you're happy. You'll wind up with a little more bass at higher volume, a little less at lower, but there's quite a range recording to recording anyway. 

Doing it this way takes a little longer and if you're one of those needs validation types sorry, but its the best we got.

Validation? Nope, If you're happy, I'm happy.
I'm interested in subwoofer variable crossover control methodology.

Thank you Miller and Elliott for taking the time.    

I sold my active subs and got Duke's (audio kinesis) swarm with 4 subs and 2 amps, you locate the subs 2 in the front of the room the other 2 wherever just not together, these are very small units (wife loves to put things on top which are constantly falling as you could imagine), I just don't care about improving bass anymore it is so perfect, I will never use anything different than a distributed array ever again.@millercarbon I have mine on 8 ohms but I will be trying the 16 ohm series config, not sure with my listener skills I could hear it but willing to try, thanks for the tip

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That’s why this is such an uphill battle. As if the physics, psycho-acoustics, mono, and "integrating" aren’t hard enough, you got to try and convince people the concept is so powerful it overrides the need for great big expensive drivers. Oh, and lamp cord will do just fine. Its just too much to swallow. Even though its all true.

@millercarbon --

Something to consider: if the 10" Morel units of yours are anything to go by two "big expensive drivers" from the pro sector, like 21" B&C’s, in a given enclosure design (like the "Skram") would be no more expensive or probably even cheaper than four Morel’s. Add in the need for two extra amp channels for the quad-approach while factoring in that a pair of 21" drivers are ~10dB’s more sensitive and sports more than twice the radiation area. "Overriding the need" as you point out in this context dismisses the importance of headroom, although to some a quad array of 10" subs would seem more than enough (and it well may be in a specific context). And yet, a dual 21" set-up like the one suggested would excite more air (even with less cone movement) and have lower distortion at a given SPL, all of which translates into an even more relaxed and effortless presentation of the lower octaves. You’d miss out on the advantage of going quads in regards to response smoothness sans digital correction, but a great result is still attainable via duals without excessive use of DSP and maintaining a fairly even coverage for more than one listener.

You could even go with smaller and (all things being equal) cheaper drivers, like a 15" driver in a horn variant and end up with a bigger effective air radiation area, force multiplied by the horn, than a 21" direct radiating driver (the 21" in the "Skram" isn’t DR, I might add, but rather hidden inside the cab and loaded on both sides of the cone), in providing a better coupling of the cone to the air and a different (to my ears ’better’) bass presentation (my preferred choice of dual-sub approach, actually). The downside: a need for a bigger cab and thereby wood.

A 4-sub approach with, say, 10" drivers like you propose in all likelihood will find more wide-spread use in hifi-systems than what I’m advocating, and they would have excellent augmentation in the bottom octaves. That being said and to reiterate: there are other excellent sub-solutions, and adhering to physics I’d say my dual-sub propositions will fit the bill quite nicely as something that can’t be overridden as an essential in bass augmentation, but that are nonetheless typically overlooked.

@phusis apologies in advance as you were addressing someone else, I understand the bass augmentation can be achieved easily with the distributed array, there is such a thing as too much bass, in my array (4x10 inches not morels) I have to tune down the amps to 50 percent and sometimes plug one or two ports, I also understand that if you add more 5 6 even 8 small enclosures which are easy to hide the effect increases even more. I had 2 powered subs with dual 18 inch drivers before and it didn't sound natural (to me), also from the amps you can change phase for two subs etc. which blends the bass even more.
I'm not trying to be argumentative with you but I respectfully differ from your opinion
Luis