Beyond the Ariel

[Variac]

For bass, Class D has to be tried, no doubt.

Another option is that each bass driver could use one of Nelson's current amps, which should improve the low end...

[agent.5]

Originally posted by Variac


On the back of the magnets?

I don't know why you want to do that, when you can easily use aluminum as the outside frame of the big woofers, and aluminum can not provide not only stiffness but also heat sinking ability.

[agent.5]

Originally posted by Variac


Another option is that each bass driver could use one of Nelson's current amps, which should improve the low end... [/B]

an array of F4?

But aren't we going back to the idea of a line level crossover? Maybe we need to incorporate a passive eq into the system -- something like a Pultec EQP1A.

[Lynn Olson]

OK, I'm going to try and post a picture of what I've been thinking of - the centerline of the 12" coax driver is 40" high, the height of the OB is 48", and the depth of the bass module is 16". All dimensions are approximate, of course, and I expect I'll get a lot of firewood out of this project - too bad I don't have a fireplace to burn it in!

The key concept is the asymmetry of the left/right leakage path - preferably, a golden-section ratio, as it is for the 12" driver at the top, with a 7" path on the left side, and a 11.375" path on the right side. Various forms of bracing, such as SL's style of magnet bracing, are omitted for clarity. Besides, you guys are plenty smart, and can figure out how to damp panels and brace them.

[agent.5]

Originally posted by Lynn Olson
OK, I'm going to try and post a picture of what I've been thinking of - the centerline of the 12" coax driver is 40" high, the height of the OB is 48", and the depth of the bass module is 16". All dimensions are approximate, of course, and I expect I'll get a lot of firewood out of this project - too bad I don't have a fireplace to burn it in!

what about moving one or both 15" to the side panels? I also think you need more curves. I have been brainwashed by those Victoria's Secret commercials that curves are sexy.



http://www.blackforestaudio.de/Helix2aWeb.jpg

[Lynn Olson]

Originally posted by agent.5



what about moving one or both 15" to the side panels?

Certainly an option, especially if you want to have four 15" drivers, two on the front, and two on the sides, with rods going between the side-mounted drivers to cancel vibration. Once you put the drivers facing each other, though, the lowpass filtering becomes more important, since the diaphragms are acoustically transparent and the drivers "see" each other. That sounds harmless enough until we get to the 1~2 mSec transit delay from driver to driver, which in turn creates peaks and dips at higher frequencies.

As a result, side-mounted drivers are partway to a "W" box in terms of box modes, so I'd reserve that option for the truly low bass content.

[agent.5]

Originally posted by Lynn Olson
[B]
if you want to have four 15" drivers, two on the front, and two on the sides

I am thinking two 12" or 15" on the front but one mounted on top of another. I am thinking 12". With two 12" mid basses and one 12" mid, the front will have three 12" mounted vertically, and then two 15" on the sides.

[planet10]

Originally posted by Lynn Olson
expect I'll get a lot of firewood out of this project - too bad I don't have a fireplace to burn it in!

Plywood doesn't make very good firewood...

dave

[Lynn Olson]

Originally posted by agent.5



what about moving one or both 15" to the side panels? I also think you need more curves. I have been brainwashed by those Victoria Secret commercials that curves are sexy.

http://www.blackforestaudio.de/Helix2aWeb.jpg

Curves are cool, but hollow spaces are not our friend, especially at higher frequencies, where you get cavity resonances that are very difficult to remove. The whole point of an OB is to remove the reliance on damping materials that is so essential for box speakers. As we know, undamped boxes are unlistenable - but damped boxes still have plenty of box sound, just kind of muted and dull.

Damping materials have colorations of their own, something we want to avoid unless absolutely necessary. The horn guys are onto something by their avoidance of damping materials, which is a band-aid for problems elsewhere in the design.

[Lynn Olson]

Originally posted by agent.5



I am thinking two 12" or 15" on the front but one mounted on top of another. I am thinking 12". With two 12" mid basses and one 12" mid, the front will have three 12" mounted vertically, and then two 15" on the sides.

With three drivers facing each other in the bass module, it's going to need good low-pass filtering so the mid-bass standing waves don't get into the audible range, but any kind of bass module (of reasonable size) is going to need a fair amount of EQ anyway.

The thing to remember is all drivers that are close to floor are going to create images of themselves, raising their efficiency. Same principle as a K-horn sitting in a corner, taking advantage of the sidewall, backwall, and floor reflections. In the mono days, a terrific idea for an unused corner, but a little more difficult when stereo came along.