Openly Baffled: DDR in Extremis

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 The single support has been replaced by a removable pair of sail panels on a spiked base.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.

And another....

And the rear...

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

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.

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 said:

... They really were scary in terms of dynamics in my 100,000 cubic foot warehouse with 1100W per channel.

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1100W?! I can well imagine.... Back in the day, a buddy of mine had fun running his Heils (AMT-5s and AMT-3s IIRC) at ~1200W, using PhaseLinear 700Bs. He did have to arrange in advance with his neighbors, when he wanted to turn them up. Last I knew, he had a wall covered with ESLs, and several kW on tap. And no neighbors. At least, none remaining.

Based on my listening so far, a pair of UCD180ADs seems sufficient, so I'll probably use 4, one per Extremis, and a pair of Greg's modules for the planars, configured as 3 PA per monoblock, once I've built the active XOs to emulate your design. I've never heard of too much headroom. For most of the music we listen to, the 'right' volume level that makes the music real isn't all that high, but the peaks can be pretty wild.

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

Dan Wiggins
Adire Audio®

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My hat's off to you for a worthy reference design, and a truly remarkable driver. I was as worried as the next guy about being able to get realistically loud, accurate bass from relatively small drivers on an open baffle. There's obviously a lot to be said for radical excursion and excessive force, which for all of that hasn't also compromised an elite subtlety and tonal balance.

I've been surprised and gratified to find that the DDR delivers the full spectrum and dynamics of my favorite music with a kind of easy grace that usually comes only with a stratospheric price-tag (which characteristic it shares with the SKA). I'm with Nate on the potential of this design, although I can confidently say that much of the potential is already fully realized. And I haven't been tempted once to hook up the sub.

I was listening to an old Shadofax piece last night, and for the very first time I could actually hear the drummer mute his kick, a measure before he let it ring. The phrase appeared several times, and I'd never heard it. Now I'm going to have to listen to everything, all over again.

I'm glad I didn't waste my Extremii by putting them in a box.

The DDRs are past 40 hours run time, and continue to improve. I'm not sure how much as a side-effect of the breakin process and how much due to simple familiarity, but the Extremii seem to have integrated completely with each other, and with the Neo3PDRs. Early on, I thought I could hear the separate drivers (if I listened really really hard), but at this point they're effectively fullrange. I'm entirely convinced that much of the honesty and sonic goodness of the DDRs is due to their MTM simplicity.

I played with DDR positioning this weekend, and soundstaging improved dramatically. They're each now ~4' from the back wall, a little more from the side walls, and ~8' apart and away. Aside from some avoidable domestic clutter, I'm beginning to think this must be about the best of all possible worlds for dipoles. Since the living/listening room adjoins the dining room, the actual listening position is nearly equidistant from the front and rear walls, carpeted and beneath a cathedral ceiling. The DDRs produce deep nulls off to the sides, but the side walls also have soft window treatments, making sidewall reflections almost a noshow.

But it's clear that I need More Power(tm). I found the bottom of the UCD180ADs this weekend, with Tony Levin's Prime Cuts. I think it was Terry Bozio's drumming that did it, but I saw a huge cone excursion and a UCD cut out for a couple of seconds, I'm guessing from over-current. That was only on one cut, and it was cranked to a fairly rowdy level...

The clarity of the DDRs also pushing at me as well. I'm finding them Very revealing.

I thought my CD5000 sounded pretty decent after I'd replaced the line driver with an AD8620, but I was noticing on certain piano passages something that my wife called 'brassiness'. I did a little more surgery on the CD5000, bypassing the mute circuit and coupling caps completely, and adding 100 nF bypasses to the opamp decoupling caps, which I made 47 uF Elna Cerafine's. I also replaced the 2-wire power cord with a shielded 3-wire Volex. I ended up replacing the AD8620 with an LM4562.

I'd tried an LM4562 in there before, without any other circuit changes, and it sounded veiled and nasty. Direct coupled, it sounded better than the AD8620 in that position, very clean and detailed, and without any tendency to glare. Put on Mike Stern's Who Let the Cats Out again, and this time found things well under control, with only the brass sounding like brass. Ditto the Metheny and Mehldau collaboration. Mission accomplished, for now.....

I raised the bar on the DDRs again, and they continue to impress.

Our old Sony up-converting DVD player started making funny noises, so after a bit of research and discussion with the boss, a new Denon 3930ci followed me home. Besides all its SOTA DVD goodness, it also does a credible job with SACD, DVD-A, HDCD and POS (Plain Old Standard...) CDs. This is no 55 lb Esoteric, but at 25+ lbs, I can say confidently that it's well damped, and for simple stereo, it's also possible to power off the unneeded video and display circuitry.

I ran the separate L/R outputs to my GAS Thoebe for level control, thence to a pair of direct-coupled UCD180ADs, now using an HG supply. The latter did make an audible improvement over the 10k-uF/rail chipamp supply, both as to clarity and punch, but except for the power reserves, I still prefer the Balls. I'm thinking GB300Ds....

Although the Denon lacks the bass impact of the direct-coupled CD5000, it more than makes up for this with superior overall tonal balance and vastly improved inner detail, all of which was instantly evident with the DDRs. Shutting off the video and display circuits in the Denon made another instantly audible improvement, which surprised me, a little. The uncanny ability of Dan's design simply to express what it's given is such a pleasure, that to call the DDR merely revealing seems almost unfair.

Wes Montgomery's live session recording of Cariba (Tsubo Club, 1962) sounded completely fresh, and it took some imagination to accept that I wasn't sitting in. This one, you have to turn it up a bit, so that Kelly's piano sounds right. Oh, man.

Hi Tim,

I started out with a sub in mind, and my bases are made to be be easily replaced with side-firing subs if I ever see the need. Not sure I do, at this point, given the music I like and the size of my room. I'm convinced that much of what makes the DDR sound so remarkable is its 2-way simplicity, made possible by the exceptional capabilities of its drivers, and I'm a little reluctant to compromise that for a little better bass. I did try the DDRs with a single 10" ported sub crossed in at 80 Hz, and decided it was a waste of time.

I do think a pair of OB 15's or bigger might be beneficial, but for now I'm more involved with correcting deficiencies in the rest of my system. The DDRs hide nothing, and I'm finding that a great challenge, and better incentive to proceed carefully. At 60+ hours I still don't know whether the Extremii and Neo3 are fully broken in, since they keep sounding better, and not simply as a direct result of other changes in the system.

I've just added ~5 degrees of toe-in, and imaging is better; too much and the soundstage wants to collapse, but a little works wonders. The room needs rearranging, but that can wait until the new (Lovan Matrix) shelving arrives. I'm still waiting on Westlake to deliver some 1800F, so I borrowed a Monster component cable to use as a short interconnect between the 3930 and Thoebe; it sounds better than the 6' automotive Audiobahn I had been using.

Another Hypex HG arrived today, so I may get around to bi-amping the DDRs this weekend, and I still need to mod the 4x UCD180ADs to use the off-board op-amp supplies. Lots to do, lots to try, but not to the DDRs. They don't need fixing.

Timn8ter said:

I've been contemplating an OB design for some time while looking at the Phoenix and Orion knowing that I could do something similar using Adire drivers. As usual, Dan beat me to it so I'll just build his design, at least for starters.
I don't doubt the ability of this design to produce nice bass but I do doubt it's going to be enough to satisfy my desire to hear the deep pipe organ and synth bass in some of my recordings.
Have you given any thought to using a dipole woofer down below?

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