Openly Baffled: DDR in Extremis

[Z33]

A little while ago, Dan Wiggins published an OB dipole design using Adire's Extremis 6.8 drivers, but even after a fairly persistent search I was unable to locate an actual builder of this design other than Dan himself. After a sensible period of modeling and pondering and wondering, and worrying that nobody but Dan had ever built the thing, I decided his DDR was likely to sound even better than my own OB experiments.

I'm not a woodworker, but I was introduced to a fine one who's also an audiophile, and he agreed to make the panels to Dan's basic spec, and with artistic license. The panels are still MDF, but veneered with walnut burl, and edged with mahogany, as are each of the cutouts. The single support has been replaced by a removable pair of sail panels on a spiked base.

I took a few liberties with the crossovers, using Solen, Jantzen and Mills parts, except the big inductors in the lowpasses, which are Erse. They're wired PTP on FR-4 single-sided copper-clad boards. They're not yet enclosed.

The plans are here

http://www.adireaudio.com/Files/DDRDipoleDesign.pdf

and the result is attached. They came alive yesterday afternoon, and they sound better than I would ever have imagined. The Extremii move a lot of air, but gracefully and in both directions, and there's no shortage of either bass or SPL. The Neo3PDR planar tweeters run without cups as true dipoles, with remarkable clarity. They're still breaking in, but they got their first taste of trumpets today, and they loved it.

[Z33]

And another....

[Z33]

And the rear...

[Z33]

The virgin panels, sitting in Del's shop...

[studiotech]

Looks great! Keep us posted with your observations on the sound.

Greg

[TerryO]

I got to listen to Dan's pair during the crossover design phase and I was very taken by the clarity and balance of this setup at the time.

What has surprised me is that more people haven't built these, they seem to be excellent speakers, but listening to them in the Adire warehouse isn't the same as a regular room, so YMMV.
I'm interested in what the verdict will be on these when they're broken in and set up properly in a "real" listening room.

Keep us posted on developments.

Best Regards,
TerryO

[Z33]

I suspect that most prospective builders have all the usual concerns about any OB design WRT bass extension and SPL. Added to that, the Extremis 6.8 is a fairly new driver, and as expensive as some better understood European parts, as is the GB Neo3PDR for that matter. And the latter actually has to be modified for the DDR. And then there's the fairly complex, high-order crossover. And the low efficiency. Pretty scary stuff.

The DDR really is something of a tour de force, and delivers in spades everything you might want from a dipole. The bass delivery was so surprisingly good that initially I had to double check that I'd really unplugged the sub. My listening area is 20'x25' or a little larger, with a high, sloping cathedral ceiling, and the DDRs light up the whole room with ease, and with just a few watts from my old Son of Ampzilla. The visceral bass of Luminal's Sounds from the Ground was very convincing, even before things had started to loosen up at all.

Listening to Diana Krall this morning, the meters were barely moving, with the upright bass comfortably loud (and Diana's voice of course doing the whole goosebump thing...). Listening to the trumpet on Robert Jospe's Time to Play yesterday, they were about half-scale, with room to grow. I'll put on Audioslave this afternoon, and Grieg later, just to see, but so far the DDRs have kept up with everything.

But even discounting all that somewhat surprising adequacy (let's face it, OB are supposed to somewhat suck at bass extension, SPL and efficiency) what really amazes is an uncanny sense of transparency to everything they do. The soundstage is vast, appears out of nowhere, and holds everything. Closed my eyes during Derek Trucks' Blind Crippled and Crazy, and the only thing missing was a smoke-filled room.

That's pure open baffle magic, and that the DDRs do really, really well. I think things will only improve when I retire the SOA in favor of Greg Ball's modules this weekend. By then the DDRs should be beginning to show their true colors. Or lack of.

[Z33]

Well, I've lived with the DDRs for a little while now, and they seem to have settled down. I think they Extremii must've been pretty tight from the factory, and there was an odd sense of tension in the upper mids that gradually disappeared, leaving ... nothing, or about as much nothing as you'd ever expect from a loudspeaker. I'd thought they were pretty honest from the start, but they've gotten even more open and relaxed as they've run in, to the point that they all but disappear. Not unlooked-for or unexpected from an OB, but the DDR is exceptionally polite about it. The Neo3PDRs were silky smooth from the get go, and perfectly complement the Extremii, up to and beyond what I can hear.

I discovered a couple of things fairly quickly, though. First, the DDR likes power, and isn't afraid to use it.

It proved disconcertingly easy to drive the SOA into clipping, which it doesn't like at all. Ouch. I thought at first I'd found the bottom to the DDR: not so. I swapped out the SOA for a pair of Greg's GB150D modules, and everything changed. I already knew the SOA was a little fizzy on top, but I had no idea the mids were so colored, and even when operating below clipping, I could sense the SOA was straining to keep up with the DDRs.

Not so the SKA. Top to bottom, the presentation was effortless and detailed beyond all my expectations. It was, simply, beautiful. I could only hear the music. To be honest, this was not in my experience a reasonable expectation, given the fairly modest investment in both time and money, but the synergy of DDR and SKA was/is tangible.

It was almost as if I was hearing clearly for the first time. I discovered that there was acoustic guitar backing on Morphine's _Like Swimming_ that I'd never suspected. There was a wash of reverb on the opening track of the Rippington's _Brave New World_ that took me completely by surprise, and I know I've heard that tune a hundred times. Kate Bush's vocals on Peter Gabriel's Don't Give Up just about ripped my heart out...

I don't know, but I strongly suspect, that the SKA would shine even on speakers that lack the obsessive transparency of the DDRs, but at the risk of becoming another Ball Booster(tm), I have to say that this combination is just amazingly good. People really ought to know how good the SKA is before they spend silly money for something else. The return on investment for a pair of SKA is immense, and this pair was doing it on a single chip-amp supply from BrianGT, and at < 45VDC.

I tried running a pair of UCD180AD on the same PS, and it just wasn't happening. Nasty sounding, harsh and unmusical, so I hooked them up as monoblocks, still using 10k-uF/rail chipamp supplies, and they got a lot nicer. Even nicer when I bypassed the coupling caps, nice enough in fact that I could begin to enjoy listening to them. Did that all last evening, over John Serrie's Century Seasons, and a collection of Spirogyra, and McLaughlin's Live in Paris, and some old Stanley Clark.

The DDRs love the extra power, and I could turn them up about as loud as I'd want. I think they'll actually go a lot further than I've pushed them so far. Even the rumbling sub-bass on Serrie's album comes through about as well as my innards can take, and Stanley's percussive bass lines stay tight and focused. No noise, no evident distortion and razor-sharp clarity and detail, and at a truly tactile SPL. I'll have them on an HG soon, and we'll see how much better that is, but I'm beginning to appreciate Greg's point about the SKA not needing all that hand-holding.

The UCDs really are exceptionally good, but still somehow more analytical than the SKA, and less moving. The difference, as I told Greg, is much like that between a beautiful woman, and one who is merely very pretty. It's hard to fault either, but you know which one you want. I'll be biamping the DDRs soon, and it could be that a UC180AD and GB150D per channel will suffice, for SPL and SQ. That, or I up the supply voltage to let the GB150Ds breath, or there are GB300Ds in my future. The DDR and SKA marriage is just too good.

The other important safety tip when deploying the DDR: watch your toe-in! Too much and the sound stage collapses completely, leaving you wandering around looking for an image that just won't gel, wondering what you've done wrong. Mine are currently set to no-toe-at-all, and imaging is both spacious and sharp, so we'll see how that goes.

The DDRs are currently connected to the UCDs with ~2.5m Canare 4S11, doubled, and the UCDs are connected directly to a lightly mod'ed Marantz CD-5000 (AD8620 on a BrownDog replaced the OEM NJM4560), with short, junk wire. That interconnect will be replaced shortly with 1800F.

[DanWiggins]

Good feedback! I know they're power hungry (they are only 80 dB efficient - the problem with all dipoles!) but if you biamp with the UcDs on the woofers and the other amps on the planars you should have an adequate amount of power for just about anything... I know they really shine with 100-300W of power, and just keep absorbing more and more as provided. They really were scary in terms of dynamics in my 100,000 cubic foot warehouse with 1100W per channel.

Anyway, thanks for the feedback, and congrats on the great execution!

Dan Wiggins
Adire Audio&#174;

[nate]

When I heard the DDR in Dan's warehouse, there was only one channel and if memory serves, it was hanging from the forklift.

The minute or two of music that I heard was really incredible and certainly "done right". I'd love to hear a pair with my big tube amp at my house! While conditions were not ideal, I felt then and now that there is a great deal of potential in this design for really high end sound, you just need some power.


btw: Dan, I hope things are going well for you and Adire! I very happily "retired" from my previous place of employment last spring to go back to business school and I haven't looked back! You can check out the latest incarnation of my Accuton/Eton speakers here:
http://forum.audiogon.com/cgi-bin/fr...7&zzlChico_j&&

Talk to you soon
Nate