@richopp , big Maggies I would agree w.r.t. the potential to put out enough bass. 1.7 and 0.7, no, not enough for rock and not enough for the depths of classical music either. For the aforementioned potential issues in most people's rooms, I am not sure I would want them doing the deep bass either in an untreated room unless you have a quite large room. In a room built to suite them, they should be stellar.
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. ;-)
Showing 6 responses by theaudioamp
Well @josh358 it seems others have put things straight. When the wavelength is much greater than the speaker diameter or baffle then the speaker becomes omnidirectional. No need for a dipole.
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. That is flawed thinking. You need low distortion. The sub needs to play the signal, no more, no less.
I helped a friend integrate 1.7s with a pair of subs. Mini DSP and well chosen filters and lots of playing with placement. Sounded perfect with seamless integration. |
@audiokinesis if we are going to go to that level then we need to go all the way.
As @bdp24 points out Dipoles are much different and even as a woofer and Linkwitz is a good resource. With Mags you have both a dipole and a large surface radiator.
Paper referenced by @audiokinesis was from early 2000 and was not without it’s flaws. This was pointed out in a reply to the paper. Specifically the flaws were in how the dipoles would excite room modes in smaller rooms and that his 2D simulation was a poor assumption at low frequencies. Linkwitz also wrote a long comment about this and another paper along the same lines.
While it is true that a Dipole can provide better upper bass, at lower frequencies the lack of node excitation causes deeper nulls which are near impossible to equalize.
So the issue is not just whether you can integrate monopole subs, but whether you should allow dipoles to go that low period. If you take advantage of DSP for sub control you can smoothly integrate over a narrow band effectively and use monopole subs which will work better than dipoles where they are most effective.
A dipole sub just comes across as a poorly thought out plan for most people and one that extends at all past 120Hz is going to create imaging problems dipole or not without proving any improvement in accuracy at lower frequencies. |
@audiokinesis - Just went and look, one researcher attached comments on the paper directly to the AES original paper. Linkwitz posted his comments separately and about similar papers. Linkwitz agree with the other person commented on the AES article. The author agreed as well somewhat. |
No really. After 120Hz you have direct directional audibility. Howver you need to consider distortion products. Either way if there is energy over 120Hz the sub is locatable and that’s bad. Phase and level matching does not fix that.
Woofers sound better, not subwoofers. |