[daveapex]

I am still pondering building a three-way speaker similar in theory to the old B&W 801 versus a full-range system using the 7A's or 7F's.
I like the loudness and the slam I got when using 12" woofers from ESS in 3+ cubic feet cabinets, but also like the idea of no cross-over network to design and less coloration of the music.
I am presently running PSB towers with 2 x 5" bass speakers in each speaker and while they sound fairly clear, they still do not have the same weight and feel as the 12" woofers.
I thought of using two 7" full-ranges in each cabinet, to compensate for the air volume of just using a single full-range.
The description of using multiple full-range drivers from another company's website >
"The dual drivers produce an effortless dynamic range, delivering an unimaginable musicality to your playback system".
I also need to run two speakers on each side to match the recommended impedance load of the amp, 2 to 4 ohms. 
So far - reading through most of this forum's subject matters, I have not seen the addressing of using multiple full range drivers in each speaker.
So my questions are, will you and others comment on using two or three 7A's or 7F's in each cabinet?
Would the internal volume of the cabinet need to increase for multiple drivers?
Will this help with getting the desired slam of the 12" woofer with effortless dynamic range and achieve the loudness and clarity to enjoy listening to Santana, Yes, and Stevie Ray Vaughan?
Thanks, Dave

[Good Times]

I would advise to steer clear of >1 full-range driver per baffle. I've heard Zu speakers that have both methods incorporated (eg Omen Standards = 10" full-range plus tweeter, Omen Defs = 2x 10" + tweeter). You lose the coherency which is the main reason for going down this path in the first place.

I would stay tuned for the next gen speaker Louis has eluded to, each speaker using a 12" active sub, then a full-range (8"?) driver covering 300-ish Hz and up from there. I reckon this is the way to do it, you get all the slam and body that you're referring to, and don't lose coherency in the process. I'd much rather the crossover down low than right up where the vocals are.

[JLM]

I've read of reasonably successful 3-way designs that use an extended range driver as a 'wide-band' midrange driver (the idea being to keep the driver well within it's comfort range while pushing the crossover points away from the phase sensitive frequencies).  Keep in mind that high frequencies can beam from a larger driver and extended range drivers typically don't have sufficient X-max (displacement) to allow for high high sound pressure level (SPL) bass frequencies.

But comb effect from two side by side extended range drivers (ripples in the sound waves from two sources that destroy coherence beyond the equip-distance plane between the drivers) would be huge.  Better to consider dipole design or better yet consider a pair of one of the new series of smaller speakers with a 'swarm' of subwoofers (to even out bass response throughout the room).

But if high SPL bass is what you're after, I'd talk with Louis.  Omega is all about honest reproduction of music at 'practically' limited SPLs and frequency range (the single driver mantra), not more or bigger is better thinking.

[Blackmore]

Yeah, better stay away from multiple full rangers.  Comb filter/interference will not be a good thing.  I'm with JLM and Good Times on that point; why not explore your version of the B&W 800 series using Louis' 7A as the driver in the robot head?  From your post, I gather you'll never be satisfied until you get that slam of the 12" woofers, so don't deny it---embrace it.  B&W likes to cross the head units around 300-350, so the 7A would be coasting at that frequency and would be able to play pretty loud before throwing in the towel.

Efficiency matching may be an issue?  Louis' designs usually hover around 92-93 so you'll need to do some thinking about what higher efficiency woofer to match the Omega driver.  Eminence Legend B102 bass drivers? (I know that may be a stupid idea, but I use a bass cabinet using 2X10 and they are strong down to their cutoff frequency)  Or go active crossover and two amps? 

There are so many cool ideas using a full range with bass helpers.  For visual inspiration, look at Vapor Audio Joule series.  Love Ryan's new two box cabinets.  Good luck and be sure to post pictures once you start building.

[daveapex]

Thanks for all the great comments. It is good to hear from folks who are passionate about audio and respect the DIYers. 
The room is really the back of a converted Step-van and is only 7' wide by 10' deep, so I do not think I will need multiple subs to fill it.
I was listening to some older orchestral Frank Zappa music and must admit, musical accuracy is also very important. 
If the use of multi-full range drivers, smears the details of the music, this would go against my intentions of realism.
I am building a 12 volt system and trying too exceed the sound quality of many the home audio systems.
The PSB's with 100 watts class A/B per-side car audio amps in the back of this van is truly amazing.
However, it still can be much better.
So, for sound and convenience sake;
Maybe, one 7F on each side with an open baffle - electric crossover at 100Hz - a single 12" passive sub, will fulfill the speaker side of this.
Thanks Again for the comments and suggestions. 
It is better and less costly to learn from others' successes and trials.
Thanks, Dave

[opnly bafld]

"Distributed bass" multiple subs are about sound quality, not quantity.
I'm not sure open baffle is the best way to go in such a small space.
How tall is the listening space?

Lin

[daveapex]

Thanks Lin,

The ceiling space is only 6.5 feet. The great thing about the subs, I can always add more later.
I was also thinking, this might be too small a space for open baffles.
Some folks rave about the openness of open baffle speakers. But, I do not want this to color the sound by having too many reflections.
I do like the look and design of Louis's EKO 7A's stand mounts on the picture page of this forum.
These smaller cabinets will also, not over whelm the smaller space.

Thanks, Dave

[opnly bafld]

Do you have a small pair of bookshelf speakers for an experiment?
If you do, place them on the floor ~ facing up ~ next to the wall ~ behind the PSBs.
Ideally the ceiling should be higher, but it is worth a try.

Lin

[hibuckhobby]

One good thing is that you're going to get quite a bit of "cabin gain" in that space on the lower end.
It won't be as much as a car...but still, depending on listening distances (I would imagine fairly nearfield)
you should be able to get good slam in there even with a pair of 8's.  Ten's or 12's will roll up your
socks.  Go for it.
Hibuck....