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. ;-)
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.
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.
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,
You make an important correction to my saying (in my explanation of dipole cancellation) that bass frequencies are omnidirectional. As you state, it is not that bass frequencies are omni, but rather that sealed/ported subs behave as omni sources because of the woofer enclosure dimensions vs. bass frequency "dimensions" (much larger than the enclosure. In fact, much larger than most room dimensions). This topic requires more time and space to fully discuss than most would care for (again, Siegfried Linkwitz’s writings on the subject are readily available for those interested), but there are a couple of points I would like to make:
One of the benefits of dipole loudspeakers is their radiation pattern: the aforementioned figure-of-8. At higher frequencies that side-speaker null (the dipole front and rear waves meeting on the sides, and due to opposing polarities cancelling one another; +1 and -1 equal 0) greatly reduces the problem of side wall reflections. The QUAD 57 (and the Sanders ESL loudspeaker) is well known to be a single-person loudspeaker: the speaker needs to be pointed directly at the listener, as its frequency response takes a dose dive as you move off axis).
At bass frequencies, those nulls almost-entirely eliminate the excitation of room modes in the room’s left-to-right axis. Fewer room modes = less "room boom". On the other hand, as Josh points out, that dipole back wave creates a problem that non-dipoles don’t (at least not to the same degree): the rear wave (half of the loudspeaker’s output) reflecting off the wall behind the loudspeaker and traveling back to the panel, where its phase relationship with the front wave can cause either frequency reinforcement, or instead cancellation. Ay carumba!
For that reason, dipole/front wall distance experimentation is required to optimize sound quality. But you audiophiles are use to and expect that, right? ;-) But here’s a basic rule: if at all possible, a dipole should be no closer to the wall behind it than 5’, minimum. Why? Because 1- sound travels at approximately 1’ per millisecond; 2- for two sounds to be perceived as separate events, they need to be separated in time by at least 10ms. At a dipole/wall distance of 5’, the dipole rear wave travels the 5’ to the wall behind it, then the 5’ back to the dipole, where it is now separated in time from the front wave by the 10ms required for the two waves to be perceived a separate entities, rather than the rear wave being a "smearing" of the front wave. Dipole 101. ;-)
Dipole cancellation occurs on both left and right sides of a dipole, and results in reduced SPL output. Danny Richie (GR Research) and Brian Ding (Rythmik Audio) advise that their OB/Dipole sub produces 1/4 the output (fed the same signal) as the same driver installed in a sealed enclosure. The answer is of course to use more of them. Hey, its only money, right? ;-) Some fanatics use GRR/Rythmik OB subs stacked floor to ceiling.
The dipole cancellation phenomenon can be tailored in a number of ways. In the old days dipole designers/builders used a wide baffle (in the DIY world that remains common), the dimensions of which would determine the frequency at which cancellation would occur: the greater the distance between the front and rear drivers, the lower the frequency at which cancellation occurs. Danny Richie found an unbraced large panel to be sonically unacceptable (he is very intolerant of resonances), so uses the same style H-frame to house his dual 12" woofers as did Siegfried Linkwitz with his dual 10’s (to see an H-frame is to understand why it is named that). Both designers settled on roughly the same H-frame dimensions: deep enough to lower the cancellation frequency to where they wanted it, but shallow enough to make the resulting cavity resonance occur at a frequency above the passband of the sub (in the GRR/Rythmik, 300Hz). Linkwitz’s H-frame is constructed of a single layer of 3/4" MDF, but Danny---the perfectionists that he is---specifies 1-1/2"
Magneplanar Tympani enthusiasts long ago discovered that if you position one side of the Tympani bass panels right up against a side wall, you would prevent dipole cancellation on that side, resulting in increased SPL output. Another means of increasing the panel output is to brace them to the room structure, often to the wall behind them. Yes, hardcore Tympani enthusiasts are a fanatical bunch (Hi Josh ;-) .
When sold for use in the OB/Dipole Sub, Brian Ding installs in his Rythmik A370 plate amp a "Dipole Cancellation Compensation Circuit". It is basically a filter which is a mirror-image of the roll-off endemic in the OB/Dipole’s output characteristics, which allows the sub to reach quite low in frequency, at relatively-high maximum SPL capabilities. Not Rock ’n’ Roll concert levels (I saw NRBQ in a medium size club last night, and it was pretty damn loud. Not Ramones !LOUD!, but loud), but as much output as most of us need (want is a different matter ;-) .
I of course don’t yet know how the upcoming Magnepan dipole woofer sounds, or for that matter the OB from Eminent Technology (Bruce also offers a "true subwoofer", for the frequencies below 20Hz!). But the GR Research/Rythmik Audio Servo-Feedback OB/Dipole Sub is a hard act to follow. I just wish I had a room big enough for the Tympani bass panels, as they require no augmentation (well, unless you need 30Hz and below), and remain my low frequency reproduction yardstick. The GRR/Rythmik OB/Dipole comes closest to matching the Tympani bass panels as any woofers/subs I’ve yet heard, far better than the woofer towers of my now-sold (back to Brooks Berdan, from whom I bought them) Infinity RS-1b’s (also a servo-feedback design).
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.)
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.
One's ears don't care where the sound cones from as long it works. Been in this hobby for 42yrs, used to sell high end stuff. I am very happy with my system, esp the value equation.
@jkf011- I’ve not heard your system, but I have heard one system I remember well with panel speakers and conventional, if high-quality, cone subs. It sounded fantastic. As with so many things in audio, results come more from care and quality of implementation than from following some guru’s formula. How much nicer it would be if all it took were money and if Universal Audio Truth were easy to come by!
Nonsense. I love my 1.7is but the arrogance and self-delusion at the company annoys me no end. In my large very open room that had little bass and no "slam" or "punch." I bought a pair of 10" Emotiva BasX subs. WORLD.OF.DIFFERENCE! Now my system - with the addition of MagnaRisers - sounds nearly perfect from all my sources and all sorts of music.
I remember Wendell Diller from a demo of Maggies at a local dealership. He insisted on playing a recording of a solo cello at the same volume as a freight train. Everything else he played was also absurdly loud. I don’t think I’d take advice from him about anything sonic.
yes, old guys losing their hearing, legends in audio they may be, is a problem when they insist on using only their own ears as the judge of what sounds right
I remember Wendell Diller from a demo of Maggies at a local dealership. He insisted on playing a recording of a solo cello at the same volume as a freight train. Everything else he played was also absurdly loud. I don't think I'd take advice from him about anything sonic.
No ! Not the old farts, who I believe are mostly interested in being happy with what they believe is the best of what they are hearing ......... until they hear better (damn those ears, as they betray us) It is often the audio-snob who seems to enjoy putting down those of us who actually enjoy their quest - that of pursuit of finding quality music, and equipment that can produce sound such that it can make the hairs on our being stand on end and make us feel thrilled that we can bring the talent of some great artists in our home, and feel in awe of that pleasure.
@secretguy, you dragged yourself into it by posting "You noticed the same level of blowhardiness too?" in response to the @pedroeb post, which you reposted. It's okay, all is forgiven. Attention @pedroeb: that too is a joke.
Hi there Jim! I’m about to head over to Portland to see NRBQ tonight (in the same club in which I last year saw Mary Gauthier.). Are they making it up to the Seattle area? Only Terry Adams remains, so I don't know what to expect. The classic lineup with Al Anderson on Telecaster and vocals was one of the greatest live bands I've ever seen and heard (twice at The Roxy on Sunset Blvd., in the 90's).
Excellent post @rhg3! I too chose the XLR version of the Rythmik A370 plate amp, gladly forfeiting the high-level hookup provisions in exchange for balanced/XLR low-level ones.
At hi-fi shows Danny Richie uses pairs of the OB/Dipole sub in the front of the room, pairs of F12's in the rear. Killer combo.
Read daily, don't post often; but I have some practical pertinent experience here.
This year I moved from IRS Betas to Analysis Orions. Huge 7 foot 4 panel system with dedicated bass panels that I believe would compare to 30.7's. Powering the Analysis with Mc901's on the main panels and Speakercraft 700w monos for the bass panels. The Speakercraft have time alignment and other goodies the Rythmik plates have.
Upon set up and initial listening with the Orions I was extremely pleased with room-filling fast, articulate bass; but missed that bottom octave punch in the chest the Betas have in spades. I experienced high quality open baffle sub stacks as well that sounded great, but didn't "hit" like I wanted. Something was still missing.
Enter 1st pair of Rel Carbon Specials..Wow! Then second set, then third set to complete the Line Array. The vertical bass component Rel details in their media is real. The Rels absolutely keep up with the Orions. Now, depending on mood I can listen to my Orions for one wonderful experience, or fire up the Rels and FEEL another experience. The fast, concussive performance of the Rels is something I haven't experienced in 25 years in this hobby.
@mbmi Sorry, not familiar with whomever you are speaking of. I know that Mark Levinson used them in his HQD system since we built the cabs for them. They were on 4" casters and weighed a ton or two, but if you really want BASS, there you go!
@theaudioampI suppose you are correct. I stopped selling before all the newer Maggies came out, but have been listening to T-1-C's for over 40 years in a great room, and have superb bass WHEN IT IS IN THE RECORDING. As someone mentioned, even a lone cello can bang you in the gut with the right acoustics. So yes, YOUR ROOM is clearly quite important and setting them up correctly is critical and, of course, having high-quality source electronics is key. Put all that together and you get MUSIC!
I’ve had had Maggies for a few decades now, currently 3.7i. I’ve been on both sides of the sub debate/dilemma. Maggies are sensitive to room placement and when it’s right the bass is definitely there.
There’s also more to how we hear than just our ears. As an example, many years ago I attended a concert with Yo Yo Ma playing Bach Cello Suites. I remember him walking out onto that large stage that usually was filled with a symphony orchestra. But it was just him and and his cello walking out to that lone chair. I actually felt a little bad for him out there all by himself. Then he drew his bow across his cello and the sound just filled the room. I was sitting center orchestra and some of the lower notes felt like they were going through my chest. It was a unique experience. I wasn’t just experiencing the music with my ears that’s for sure.
Last year I ordered a Rythmik F12SE-XLR3, A370XLR3 plate amp and fed it from my pre-amp. The plate amp has a number of controls (https://www.rythmikaudio.com/download/XLR3_sealed_quickguide.pdf) but dialing in the phase was all that was needed for the music to take on a different, meatier (can I even say that?) tone. My wife wandered into the room and asked what I’d done and to not undo it.
The bass is subtle and it's not entirely obvious that there’s a sub running — until the sub is turned off at which point the “texture” of the music changes to something much leaner.
I was pretty impressed so I bought a second Rythmik sub a month later. I don’t know how well non servo subs would integrate but the Rythmiks are a game changer for me.
As for Wendell Diller, he’s an icon. And he also has an agenda like everyone else. He’s really not going to encourage his customers to augment his product with another manufacturers speakers.
I’m glad that Magnepan plans on introducing a sub to their product line it will address a long standing desire from many of their customers.
@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.
@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.
Personally, I have never seen the need for a sub with Maggies, but to each their own, I suppose. In my shop, we would sell you whatever you THINK you need, and be happy to cash your check.
Maggies reproduce what you feed them, so I suggest you get some good "feeder" stuff and then listen. Bass from Maggies is tight and does not slam you gut like live bass at heavy rock shows where the mixer has no idea what is going on and cranks it up to 12. Whatever.
Go into the studio and LISTEN to the mix as the musicians are playing--if indeed you can find a studio that actually lets the musicians play as a BAND and not one at a time with headphones on so the engineer can "make" the music. The dynamic range of the BAND includes the bass at its appropriate volume and tenor. It is part of the total sound, and not meant to stick out by itself in the mix--disco respectively excluded, of course--and with Maggies you get good punch without overpowering the rest of the band.
BUT, if you love that gut punch, stop screwing around with those little 8-12" sissified woofers and get a REAL pair of sub-woofers : Hartley 26"’s with 1000 watt amps in 5’ high cabs and you can have it!
@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.
@pedroeb (and @perkri): Silly boys, you missed the joke. Don’t you see the ;-) after the line you quote? I am regularly guilty of giving humans too much credit. For all I know, you don’t even understand the use of irony.
Obviously some don’t understand the significant differences between a dipole sub and an omnipole one. Do some reading, and all will become clear. Reading Siegfried Linkwitz will give you a free education.
For starters, a dipole reproduces---say 100Hz---from both the front and rear of the panel, the front and rear waves being in opposite polarity. When the waves wrap around the sides of the panel (yes, very low frequencies are omnidirectional) the front and rear waves meet, and as they are opposite in polarity their combined outputs create a null on either side of the panel. At low frequencies the polar response of a dipole sub is a figure-of-8, just like that of a dipole loudspeaker. If you don’t think that’s important, Siegfried Linkwitz disagrees with you.
Then there is the fact that a dipole sub doesn’t pressurize the room as does an omnipole; the air on both sides of the dipole is moved from one side of the room to the other, while an omni pumps bass waves into the room from inside the enclosure (a virtual room within a room). Sounds like an insignificant difference, but it’s not.
Until you have heard a dipole subwoofer, your opinion of them is based on incomplete knowledge and lack of direct empirical experience.
James M. Kates wrote an Audio Engineering Society paper many years ago (which I don’t have the reference for) showing the improved in-room bass smoothness of a dipole relative to a monopole. So if we want a subwoofer system which approximates the in-room bass smoothness of a dipole, we either need to find a way to make a worthwhile improvement over the in-room bass smoothness of a monopole, or use dipoles.
Note that "smooth bass" is "fast bass", both perceptually and literally, as it is the frequency response peaks which take longer to decay into inaudibility. Kates showed that dipoles interact with the room in such a way as to have less frequency response peaking in the bass region than monopoles do. As a longtime owner of and dealer for dipole speakers (SoundLab electrostats) and a manufacturer of monopole speakers, my experience has been that good fullrange dipole speakers have superior bass region articulation and pitch definition compared with good fullrange monopole speakers, but that good fullrange monopole speakers do a better job of conveying "impact".
Earl Geddes on the subject of how to get smooth in-room bass using monopole subs:
"The use of multiple source locations [multiple subs intelligently distributed] in the modal region will globally yield a response curve that is closer to the natural power response of the sources and the room. Said another way, if we use multiple source locations the frequency response at any given location in the room will become closer to the true power response (read smoother) the more sources that are used. Basically if I have one source which has a variance, V, of the frequency response (the variation of the response from the average or smooth response) of say 6 dBs, by adding a second source we will reduce this variance by half to 3 dB. Adding a third source reduces this to 2 dB, etc. Basically the variance goes as V/N where N is the number of “independent” sources. A key requirement here is “independent”. If the added sources are close to the first source then they are not independent. And two sources in opposite corners or symmetrical locations are not as independent as two sources placed in non‐symmetrical locations. It is impossible to have two sources that are completely independent at LFs in a small room, so the effect is never as good as the formula suggests."
not sure who was being quoted about searching for past posts before posting a new thread on a given topic - leaving aside condescension and poor tone of voice, it is actually a substantively very useful and good point
one of the really special things about a-gon is its long history, and many many many caring and knowledgeable people who have shared information and discussed topics here - newbies are well advised to use the search bar above to find info on most topics they are curious about in the present tense
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.
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
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.
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