Got M&K MX-150 THX for Maggies... feelings?


I picked up an M&K MX-150 THX MkII for half price, feeling that it was a reasonably good deal for a 12" sealed sub to pair with my Magnepan surround sound system.

In the past it seems as though people have been impressed with the upper range of the MX-150 and that should come in handy when reaching up to the 80Hz crossover of my surrounds and center, although my mains, 1.6QRs go a bit deeper (50Hz or so).

My question is if anyone has any tips for blending this little guy into the system. I'm expecting to be blown away because my current subwoofer was a brick & mortar super sale special Infinity PS-10 that sounds a lot like my Fender Deluxe guitar amp when it is getting some seriously heinous feedback. Tips and tricks are welcome. Anyone feel that picking up a second would be a worthwhile purchase?

Thanks everyone for your help! By the way, I bought this over an Onix UFW-10 and an REL Strata III so if you think I'm a complete moron, be gentle.

-Steve
skablaw
Rodman99999, I did it that way too (for 14 years, not 26 years) until I realized it was the wrong approach ;--) I sure was happy to eliminate those external filters, delay compensators, etc., from the chain.

If your (very well designed, I assume) planar speakers sound strained, it's certainly not because you're runnuing them full range, it's because your amp is not right for the job. Planar speakers don't "strain" when they run out of bass response, the bass just fades away.

There's absolutely no reason to take ANY bass response away from the main speaker and send it somewhere else. If the main speakers produce crappy bass and it's not the amp's fault, then you should sell them and buy something better.

The purpose of a subwoofer is NOT to take over any bass duties from the main speaker but just to (subtly) fill in those regions where the main can't go.

If you'd like confirmation of this approach, you can speak with Steve Winey at Magnepan and/or Jim Power at Martin Logan. Steve will also tell you that bi-amping the old IV-A's, 3.6's and 20.1's is OK, but only if it's to put a tube amp on the tweeters -- not to cut off the bass response.
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Gentlemen,

I'm afraid that I'm becoming confused with the responses to my own question and now find myself even more puzzled than when I started. Considering that I have a great deal of knowledge to assimilate before I can take such technical observations into account, would I be folly to use my pre/pro's bass management to set a crossover at the -3db frequency of my Maggies and slowly turn up the M&K until I can match SPL at the point of crossover? Is this approach too pedestrian for the Magnepans?

I notice an MX-150 Mk II for sale here in the classifieds... I'm beginning to think about picking up a second! Would my money be better spent on the addition of an SMS-1 or some other EQ to smooth out what is an admittedly atrocious room than on a second sub at a good price? I hate the concept of limited resources with limitless wants... thank you, microeconomics, for my crippling indecision!
Bob, first I'd just like to say that I feel it's probably a mistake to make generalizations about any speaker "type" be it horns, or boxes, or planar (magnetics or stats) etc. Some are very good at everything (they do) and others not. This is less true of planars but only because they're relatively harder to build, and so there's no profit in making crappy ones ;--) So saying that "a conventional box speaker produces more distortion in the bass region by either increasing SPL or decreasing frequency" is simply not true for the majority of decently designed and built box speakers operated normally (ie with a flat signal.) And I'm not just referring to megabuck products.

For the sake of discussion, I prefer to say dipoles because some "planars" are curved, and not all dipoles are planars -- some are infinite baffle cones. So, except for Soundlabs electrostats, Apogees (now coming back), and the big bass panel Maggies (old and new) I don't know of any panel dipoles (as opposed to cone dipoles) that go flat all the way down to 25 or 30Hz . And as most people eventually discover in the case of Maggies, you really have to play them loud to get them to perform "full range" -- but it IS possible, and they CAN be driven hard without distortion. My Tympani 1-D's had great bass (ie no need for a sub) but only at live levels and they absolutely required a powerful ss amp. If you wanted rich sound otherwise, you needed a sub or a "loudness" control.

Most planar dipoles (ie electrostats) just don't have the enormous panel size it would take to produce low bass -- even the big Soundlabs barely make it, but they do make it!
So with most of them, the bass output (SPL) just starts tapering off at (what would be for an ordinary box floorstander) a fairly high frequency -- beginning 80Hz for my CLS's and down to "you can't hear nuttin' at all" below 40!! BUT, you don't get any bass distortion, no matter how loud you play them.

So fact 1.) The bass response profile (generally) for dipole planars (including Maggies most of the time;--) mimics a typical high-pass rolloff curve that you'd find in a typical electronic crossover set to say 80 or 100 Hz at a slope of 6dB per octave, PLUS there's no phase shift. Knowing that, it sort of makes the use of an external high-pass filter or crossover redundant -- the speaker, BY ITS DESIGN has already rolled off the bass in the most natural way possible! The only way you could get it to distort, and ONLY at the frequencies above its 40Hz lower limit, would be if you tried to correct it's natural bass defficiency by trying to kick it back up with an equalizer.

So fact 2.) All you need to do is add a sub that has a high frequency rolloff curve that's the opposite of the panel's low frequency rolloff curve (in other words, where the SPL of both speakers falls to about half, at the frequency where the curves cross.)

As for why your Maggies sounded better with high pass filtering, with or without a sub -- I don't know, but something was not right -- it was certainly NOT due to an imperfect design. Perhaps it was the amp, or a failure in the crossover, or even a bad panel? I know the folks at Magnepan, and I can tell you they wouldn't put out a product that sounded better after the customer circumcised it.

Fact 3.) Placement: Dipole speakers radiate two waves, equal in strength and opposite in phase. And, there are tons of dipole sub designs, which would be the obvious choice to match with panels. UNFORTUNATELY, there don't seem to be any that are commercially available and/or have great transient response. I found that the new Martin Logan designs (the Depth and Descent) with their omnidirectional radiation pattern can be made to approximate a dipole sub, if placed right between the panels and set to a 90 degree phase angle. (Meaning the sub is only a LITTLE out of phase with the front OR back of the panel.) And, they are FAST! Martin Logan also has brought out the new Summit, which has its own self powered built-in sub each side. They sound great, but I'm not sure they solve the dipole phase-matching issue as well as my solution (one Depth in the center) or perhaps a real dipole sub would do.

As for subs-with-box speakers, that seems to be a two sub solution usually. Whether its by grouping sub towers with mid/high towers (Alon, Genesis, Pipedreams, etc) or with main full-range (?) speakers. The latter being something I just totally don't understand (why not just build decent bass into the main speaker to begin with.) I'm OK with the monitor/sub solution, but again, it's going to be a compromise no matter how it's done (ie one sub or two? and where do you place it/them?)

Basically, my "convictions" (I'm OK with that:--) are that for two channel, keep the system itself as pure and simple as possible, especially the preamp-to-amp-to-speaker part of the system. Think "minimalist". Don't add stuff to fix the signal when you should fix the room. Avoid the urge to bi-amp (unless the speaker comes with it's own bass amp of course.) If your room is smaller than 15.5 feet by 23 feet, accept that your speakers will be on the short wall and you will have to listen "nearfield." As for HT or multi-channel, I have no particular convictions because the object is to produce stunning effects whatever that may require.
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