Seadogs1,
Dipole bass is diffrent from monopole bass. That chest-thump you feel on a kickdrum is from the whole room being pressurized. A box woofer can actually increase or decrease the net air pressure in the room, but a dipole can only create local pressure differentials so it takes an awful lot of air-moving capability to give that kind of bass impact.
A large dipole bass system like the Maggie 20/20.1, full size Sound Labs, and the Audio Artistry Beethoven can move enough air in the bottom end for you to feel it. They can even give you that "room shaking" feeling on organ and synthezised bass. But in my experience they do not give you the chest-whumping impact on drum and bass guitar that a good large box will. On the other hand, a good dipole bass system will usually give you better pitch definition because its figure-8 radiation pattern puts significantly less energy into the room's side-to-side and top-to-bottom bass resonant modes, so the notes decay more quickly and naturally (less overhang). And of course, there are no boxy resonances.
The bottom end impact of a given dipole system can be increased by adding "wings" on either side to increase the path length between the frontwave and the out-of-phase backwave. This may well thicken or otherwise color the tonal balance, unfortunately, and can disturb the cohesiveness of the presentation.
I appreciate Rangers Audio's comments, but the Sound Lab M-1's don't normally go quite down to 20 Hz (disclaimer - I peddle 'em). I say "normally" because two of my customers claim to measure in-room response down south of 25 Hz, but the factory spec of somewhere in the upper 20's is probably more realistic. The big Maggie 20 and 20.1's also go just as low, and are a bit less expensive than the full-sized Sound Labs. The metal-frame Sound Lab Ultimates do indeed have better impact and bottom end extension than their wood-frame counterparts do, but they cost almost a Honda Civic more. For another two and a half Civics' worth, you can add a pair of 40" wide metal-frame Ultimate bass panels, and these are big enough and have enough excursion that they will definitely give you that chest-whump even though they're dipoles.
Obviously, if you go with a good hybrid system, you can get chest-whumping bass from the woofer boxes. But I have yet to hear a hybid system that sounds as coherent as a good full-range planar. That's why Quad came out with the 989, so you wouldn't have to add a separate sub with very different radiation characteristics (if you'd like I'll go into detail about why the radiation patterns matter, but I don't want to bore you too much here). Anyway, the best impact I've heard in a hybrid system was a big Wisdom Audio system, but in this case amplifier matching was critical.
Let me pause and mention that with any of the full-range dipole systems we're talking about here, amplifier matching makes a world of difference in whether or not you have good dynamics and impact. A Maggie 3.6 with the right amp will subjectively have more dynamic impact and liveliness than a 20 or 20.1 with the wrong amp.
Now, there is a full-range dipole speaker that will be introduced within the next few months which will have very deep low-frequency extension along with exceptional air-moving capabilty, so it should fill the niche you're asking about. I haven't actually heard the speaker yet, but I'm friends with the designer, Mark Gilmore of newly-formed Gilmore Audio (Mark and his parter, distributor Harry Blazer of Glacier Audio, gave me permission to post this). The Gilmores will be two-way dipoles with an extremely lightweight ribbon operating above 200 Hz or so and an array of flat-panel, ultra long excursion planar hybrid woofer elements operating down to a claimed bottom end of 20 Hz. Mark is pushing the edge of the envelope in several directions at once - his speakers will also be fairly efficient and easy to drive. More specific information will be available in a few weeks. Disclaimer - I will be peddling these.
Best of luck to you, Seadogs!
Duke
