Wendell Diller: "You don't wanna put a subwoofer with a Magneplanar; it doesn't work."

In an interview with Chris Martens of The Absolute Sound and Hi-Fi + (viewable on YouTube), Magnepan’s head of promotion Wendell Diller (he is also involved in product development) discusses the company’s upcoming new product: the Ultra Wideband Bass System (UBS). Though the thread heading quote (taken from the interview) would lead one to assume the UBS is not a sub, it in fact is. Huh?

Wendell is of course referring to all "normal" subs, normal meaning sealed and ported enclosures with dynamic (cone) woofers. Sorry REL enthusiasts, that includes yours. ;-) Wendell goes on to say:

"’Cause you’re mixing a monopole with a dipole." Long term Audiogoners may recall I (and a few others) have been singing the praises of the GR Research/Rythmik Audio OB/Dipole Servo-Feedback Subwoofer for a few years now. I have been especially adamant in opining that this particular sub is THE sub for any and all dipole loudspeakers, and have given the technical reasons why such is the case. I won’t repeat it here, as I grow weary of wasting my time. For those seriously interested, a search of old threads will reward you with my wisdom. ;-)

Wendell goes on to say: "A dipole woofer is not a new idea." Indeed not. Danny Richie of GR Research was already designing loudspeakers employing dipole woofers (and dipole midrange and tweeter drivers) and selling them as DIY kits when he heard about a new servo-feedback subwoofer (again, not a new idea. At least in general terms.), one being offered by another company located in Texas: Rythmik Audio. Rythmik’s Brian Ding had designed (and patented) a new method of applying feedback to a woofer, and Danny proposed the two of them put their big brains together and develop the world’s first OB/Dipole subwoofer to include servo-feedback. Few have heard it, but I’m tellin’ ya, it was a game changer. Wendell and Magnepan are late to the party (they are not alone. Read on.), but better late than never.

I and other early Magneplanar Tympani owners (I bought my T-I’s in 1972) were permanently spoilt by the quality of the bass reproduced by those big bass panels (two 16" wide x 6’ tall panels per channel). I recorded my 26" Gretsch bass drum with a small capsule condenser mic plugged directly into a Revox A77, and I have never heard a cone woofer reproduce the sound of that bass drum as do Tympani’s (I now own a pair of T-IVa). Those bass panels are also unmatched when it comes to the lower registers of a grand piano, an upright bass, and in fact all low-frequency percussive sounds. Even the "shudder" produced by the massive organ pipes heard in cathedrals and churches. Tympani bass panels are also unmatched at reproducing the "texture" of bass instruments.

Magnepan now offers the incredible 30.7 (I heard it when Wendell took it "on tour" a few years ago), which is an updated version of the Tympani’s. But Wendell himself no longer has a room big enough for a pair of 4’ wide panel loudspeakers, so embarked on a development project to create an alternative. The result was the concept loudspeaker, temporarily referred to as the "30.7 For Condos". It is the midrange/tweeter panel from the 30.7, with a new dipole subwoofer in place of the huge 30.7 bass panels.

This Magnepan dipole sub will be made available for augmenting all the company’s loudspeakers, in a number of driver incarnations. The debut model incorporates 8 woofers per sub (I’ve heard either 6.5" or 8" woofers), the drivers powered by an on-board amp, with crossover and DSP facilities. Wendell: "This concept really works because of DSP. With DSP you can fix the time/phase/amplitude problems so it plays nicely with whatever the panel might be." Not to be contrary, but the Rythmik Audio A370 plate amp that is included in the GR Research/Rythmik Audio OB/Dipole Subwoofer provides controls for optimizing the time/phase/amplitude relationship between loudspeaker and sub, and does so without any digitization of the signal.

Wendell: "I see this dipole as the proverbial fork in the road for Magnepan because it can keep up with any of the panels. This concept is unique." Uh, ’fraid not Wendell ;-) .

Ya know, Magnepan is not the only maker of magnetic-planar loudspeakers in the world. Bruce Thigpen of Eminent Technology, though very impressed with the Magneplanars, thought he could improve on them. Bruce developed his own m-p driver, imo better designed and built than those of Magnepan (I have both). His LFT driver is a vast improvement on the design still used by Magnepan, but to keep the size of his LFT-8b loudspeaker "manageable" he compromised by using an 8" woofer installed in a sealed enclosure to reproduce 180Hz downward.

Great minds think alike? ;-) Already available from ET is Bruce’s new dipole sub, also employing DSP. ET’s sub is being called a dipole, but I don’t know whether or not it is an OB. The sub is a bolt-on replacement for the stock LFT-8b sub, and retails for $1500/pr. The LFT-8 shipped with the new dipole sub is named the LFT-8c, and it retails for $3999. So an owner of the 8b (which originally sold for $2499, now $2999) pays no penalty for now buying the sub to use with that models still-identical m-p panels.

For planar loudspeaker owners who crave full-range bass, but both lack the space necessary for huge planar bass panels and find monopole subs unsatisfactory for use with planar loudspeakers, you now have options. The GR Research/Rythmik Audio Servo-Feedback Subwoofer is killer, but is available as a kit only. The required OB frames are available as flat pack, and are simple to assemble and paint. But for those who want plug & play, the Magnepan UBS is certainly good news. As is the ET dipole sub for current LFT-8b owners. For planar loudspeakers owners who find monopole subs fine with panels, either Wendell Diller is wrong or you are. ;-)


jss/the audio amp

Bass frequencies aren't "omnidirectional" -- they're no different than treble frequencies. Monopole woofers are omnidirectional because the wavelength is larger than the enclosure (in other words, below the baffle step). As BDP pointed out, a dipole behaves as a dipole even at low frequencies.

The audioamp -- the reduced modal excitation of dipoles is easily measured and heard. It is the main reason that dipole woofers sound better. In subjective comparisons, it takes four omnidirectional woofers to match a dipole woofer. The main disadvantage of dipole woofers is cancellation from the front wall reflection. With a monopole, the difference can be split between room surfaces. With a dipole, not so much. So they will typically have a suckout between 100 and 200 Hz as a result.

"The key to integration is fast roll off filters so subs have little output over 80hz. Allowing the woofer to extend beyond that allows the woofer become identifiable. That is a very bad thing. You don't need a high FR for a sub to be fast."

Not really. The frequency response and phase of the woofer and midrange have to match through the crossover range. That's the direct benefit of a woofer with extended high frequency response.

Hi Russ,

Someone told me that the LRS+ is there but hard to find. They seriously need to work on their website!

JKF011, you have mid sized Maggies. The big ones go much deeper and have more punch. (Bass performance also depends very much on the room -- swings of 20 dB are common. If you listen to the larger Maggies, what you'll hear is bass that's *realistic* in the way that two monopole woofers, no matter how good, aren't. To get that kind of sound from monopole woofers, you need four to reduce the excitation of room modes.

Anyway, the goal of the Magnepan woofers is to combine dipole realism with dynamic "slam" and by all accounts, they've hit a home run -- everyone who has heard it has been enthusiastic -- Chris Martens of The Absolute Sound says it's the best woofer he's ever heard. (Disclosure: I don't work for Magnepan and have never received any money from them, but I did have a role in the development of the new woofers. What I'm passing along here are some of the considerations we used in designing them, as well as the results of our experiments. We were surprised to find, for example, that multiple small drivers sound better than a large one with equal displacement -- others in the business have made the same observation. Some of this is probably due to behavior in the crossover region -- that's known to make a woofer sound "slow" if the drivers don't match -- but there are likely other factors as well.)

I run a pair of small MLs with mine to decent effect. Ideal? Probably not, but with careful adjustment, quite good.

I would expect WD’s woofer/subwoofer integration to be much better than the many trials of past integrations.  Looking forward to a demo.