A great DIY line array speaker????

I heard the GR-Research Alphas this past Sunday. VERY VERY nice. Layers of depth, imaging to die for, and so room-filling it was borderline spooky. And being driven by a 30 watt class A amp. I kept feeling that [good] uneasiness that a sharp drum rap might just blow me through the sofa I was sitting on; that feeling akin to sitting in a quarter-mile souped up race car with the engine just idling, daring you to punch the gas. Now I know what is meant when people leave a demo just shaking their heads, kinda wondering what they just experienced. Certainly wasn't the kind of listening that you do when the sound is coming from two small (or even standard floorstander) speakers. I mean Lyle Lovett was so much in the room that you could feel him sweat baby. A little discombobulating to be sure. And there were black sisters in the pews next to you, two rows in front, and I think I even heard some 'amens' from the back of the church. Lord have mercy. I was reaching for my wallet just in case the plate came by.

Damn fine speakers, and a screaming bargain if you've got the room to let 'em do what they do. Again, an altogether different experience - and quite the opposite of 'listening' to your basic [even very high quality] stereo.

Check out Zalytron.com under Audiophile kits for a Dr. Joseph D'Apollito design, very interesting and has customer comments. Also check out ORCAdesign.com which had the same kits and schematics for a nice line array project, if ORCA's new site is not fully finished just email or call Kimon Bellos at ORCA for details. He's a wonderful guy to talk to!

Once upon a time I designed and built several different line-array speakers. I really like the kind of sound field a tall line source sets up in the listening room.

Here are the lessons I learned:

1. It's pretty much impossible to get a seamless blend between a line source array and a point source woofer or subwoofer - if possible, make the arrays capable of doing the bottom end.

2. The amount of money spent on all those drivers would probably be more effectively devoted to fewer, higher quality drivers.

3. Horizontal symmetry is desirable if you want the tonal balance to be uniform over a wide sweet spot.

I have three ideas for a DIY line-source speaker, but I haven't built any of them.

The simplest design would be a stack of about a dozen Jordan JX-92's per side. This driver wasn't available when I built my line source arrays years ago.

A bit more complex symmetrical array would be based on an MTM kit using say 6.5" woofers and a 1" dome tweeter, but with the drivers oriented horizontally instead of vertically. Basically, imagine stacking eight such sets of drivers per side, so you have sixteen woofers flanking eight tweeters per speaker.

My last symmetrical array idea array would be a large dipole panel about four feet wide. In the center you'd have a stack of ribbon tweeters, whatever your choice is. The ribbon tweets would be flanked by a pair Bohlender-Graebener planar-magnetic drivers. Sure you could use a single B-G and save quite a bit of money, but note that Genesis and VMPS both use ribbon tweets to do the top end instead of relying on the B-G drivers. The reason is that the relatively rugged B-G driver isn't as articulate and lively at high frequencies as it is in the midrange. Anyway, the bottom end is handled by eight 15" dipole woofers per speaker, flanking the B-G drivers in stacks of four, to maintain symmetry.

If you'd like to talk about any of these options, shoot me an e-mail.

Go over to harmonicdiscord.com for more info, discussion and pics on the gr research alpha's. There's a manufacturer's info site there.

I spent a while looking at the gr-research site, which is remarkably uninformative. Has anybody heard them?

will

http://www.gr-research.com/Alpha.htm

Go to partsexpress.com and look at the B&G 72" ribbons. Build it with two "wings" on either side, preferably curved or angled back like a trapazoid, with you favorite wood, and no back to the cabinet. Build a second set of boxes to the same height, a foot or so wide and deep and the 72" height of the drivers. Put four of the new peerless sub drivers in it, or maybe two active drivers and two of the matching passive radiators. Ever see the old Infinity Servo Statik's? That's what your aiming for. but for $2000 instead of $60,000 (probably $100K now if they were still available). I think Genesis had something along these lines. They give you a design for a passive crossover for the B&G's, or perhaps use an active cross over, or maybe just direct connect a tube amp to the B&G, and a solid state amp with an electronic crossover to the Sub towers. Definitely tubes on the ribbons. That's what I am dreaming of doing, but don't have the space or funds at the present!
Tom