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. ;-)

Hi BDP, Didn't know about the ET dipole, interesting! While they share dipole virtues, the GR Research and Magnepan subs are somewhat different beasts. The GR is bigger -- the Magnepan sub is a 3' tall triangle that's designed to be concealable. I'd say it's also more of a subwoofer, with flat response down to 20 Hz. OTOH, from what I've heard, the Magnepan woofer sounds better where it plays because of the smaller drivers. TANSTAAFL!

Hi Josh, nice to hear from you here. I decided not to respond to @theaudioamp, as he appears to be one of those who knows just enough to be convinced of his lack of ignorance (for instance, everybody knows a dipole does not "load" the room the way a monopole does). Guess he’s never read the writings of Siefried Linkwitz. THAT is a humbling experience ;-) . One of the geniuses of loudspeaker design.

Regarding the smaller drivers used by Magnepan in their dipole sub: Brian Ding was for quite a while offering a Rythmik Audio sub using 8" woofers, but argued that it’s advantage was not simply in "speed" (lots of people think a smaller woofer automatically results in "faster" performance. Yes, lower driver moving mass can produce faster "settling time" in a woofer, but moving mass alone is but one of many factors involved in that issue.), but rather in its ability to play higher in frequency (the GRR/Rythmik OB sub plays up to 300Hz). He offered the 8" sub as a "midbass coupler", emphasizing that his 12" and 15" woofers are just as "fast" as are his 8", but with greater maximum SPL output capability.

By the way, the Magnepan dipole sub is named the Ultra Wideband Bass System because its response extends up into not just the midrange, but even into the treble range! The technically informed reader knows the higher in frequency a driver will play, the greater is its ultimate speed capability potential. Wendell argues that the UBSes high frequency extension is another reason (aside from its dipole performance characteristics) for its ability to blend with planar loudspeakers.

8" is certainly a popular size woofer in hybrid loudspeakers (planars with built in subs). Roger Modjeski used an 8" woofer in his Music Reference ESL loudspeaker, as of course does Bruce Thigpen in his Eminent Technology LFT-8b.

bass frequencies are known to be omni directional, so it has never made sense to me why the dipole sub topic gets significant air play, if in fact the subs are truly producing 100-120 hz output and below - i suppose that for even good subs there is some ’leakage’ above that cutoff, which may be the answer...

dsp, otoh, seems to be very useful, to deal with timing/delay/phase issues, and as per the above, to manage a steeper rolloff/cutoff - computing power is so cheap to build into audio gear now, cellphone control and app-writing is so easily done

that said, with my 3.7i's in my room i do not feel the need for a sub/subs in the least - one day i will hook up my rels and see if i would amend this present belief

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