Product Review - M&K Surround 55 Tripole Speakers - July, 2000

Ralph Calabria


M&K Surround 55 Tripole Speakers

Sealed Enclosure

One 1" Soft Dome Tweeter, Two 3" Cone Mid-Tweeters, One 5 1/4" Woofer

MFR: 87 Hz - 20 kHz ± 3 dB

Impedance 4 Ohms Nominal

Recommended Power: 10 Watts Min, 200 Watts Max

Size 10 1/4"  H x 6 7/8" W  x 8 1/4" D  

Weight: 12 Pounds Each

Finish: Black or White

MSRP: $699/pair 

Miller & Kreisel Sound Corporation, 10391 Jefferson Boulevard, Culver City, California 90232; Phone 310-204-2854; Fax 310-202-8782; E-Mail [email protected];  Web 

A Little Primer

When shopping for a pair of surround-sound speakers at your local audio/video store, you’ll come across a variety of designs to choose from.  The ongoing debates can still be heard echoing in the sound room on which type of speaker is “ideal” to use for surround-sound duty.  Let’s take a look at the more common ones.  First and most common, there’s the direct radiating speaker. They resemble the mini-monitors typically used for left and right front speakers in audio and video setups.  There’s a tweeter and a woofer both situated on a front baffle.   Then there’s the dipolar speaker, which have been the favorite (and the THX standard) for a lot of  people when Dolby Pro Logic (DPL) was the standard, before Dolby Digital and DTS emerged.  Dipoles are speakers that have two sets of drivers on 2 baffles, with each side being wired out of phase.  When dipoles are used a few feet out from a wall, the speaker is routinely positioned such that one set of drivers is directing sound to the front of the listening room and the other to the rear, creating a more diffused, non-localized sound.  When used in the rear, mounted on the wall, the drivers are usually positioned so they fire to the sides. Dipoles work well for DPL because, for one thing, the rears are in mono, i.e., each speaker is being fed the same information.  Most dipoles’ low frequency cutoff are typically around 100 Hz (one of the effects of having the drivers wired out of phase), which is fine since most movies mixed in DPL have cut off frequencies below 100 Hz anyway.  Bipolar speakers are somewhat similar, but the drivers are wired in phase, and frequency response is generally extended slightly in the lower range compared to the dipoles.  As with dipoles, when used as rear speakers mounted on the walls, the drivers are positioned sideways.  Now, with digital technologies the current standard, things have changed a bit with regard to selecting the best qualified candidate for the job of surround-sound caretaker.  Several hybrids have become available that combine technologies.  My current surround sound speakers are from Paradigm’s adapted dipole speakers (ADP) line.  These speakers act as dipoles above frequencies of 100 Hz, and as bipoles below 100 Hz via a special crossover network.  That’s one way of getting more bass into the rear!  ADPs provide a nice blend of diffuse sound while still giving the surround channels some direction (on digital sound tracks) and slightly more low end output.

The Main Event

One of the newer kids on the block is the tripole™ surround speaker.  This is the technology that M&K introduced back in 1996 with their SS-150 THX tripole.  Recently, M&K has added a few more tripoles to their line.  One of their latest is the Surround-55 tripole, the least expensive of the line offered at $699 MSRP.

So how does this tripole differ from the others?  Well, as the name implies, the design intent is to act as two different speakers (a dipole and a monopole; di + mono = tri).  The two 3” paper mid-tweeters are positioned one on each side of the speaker oriented in dipole fashion.  Responding to frequencies of 300 Hz (the high pass crossover point) and up through the mid-range, the dipole speaker configuration emits diffuse sound throughout the room.    On the front baffle is a 1” soft-dome tweeter mounted at a ~5° angle pointing away from the primary listening position.  M&K claims this off-angle positioning enhances the overall smoothness of the high-frequency response both on and off axis.  The key is to point the tweeter toward the room’s back wall.  So in essence, the speakers are not interchangeable.  There is a designated left rear and right rear speaker.  Each speaker is clearly marked to make sure you get it right.  This photo shows the tweeter raised slightly (on the left side) from the front baffle.

Also on the front baffle is a 5.25” polypropylene mid-woofer.  The combination tweeter/mid-woofer provides a direct radiating speaker configuration (which happens to share the same drivers with M&K’s LCR-55 and LCR-750 satellite speakers).  The direct radiating design is optimum for digital playback were point source imaging is important. The tweeter and mid-woofer work together with something M&K calls their proprietary Phase-Focused crossover.  The crossover is intended to give a smooth response over a wide listening area, both on the vertical and horizontal axes, thus extending the sweet spot of the speaker.

The grille is somewhat unique.  The metal meshed grille is supported on the front baffle by being ‘spring loaded’, that is, the flexible grille is bowed to fit into grooves along the left and right edges of the front baffle.  Said to be acoustically inert, the grille may also be easily removed if you so desire.  The rear of the speaker accommodates M&K’s wall-mounting brackets, both the side wall and corner-mount models, their ST speaker stands via a large machine bolt, and a flush-mount hanger.  Speaker wire connections are made via the 3-way binding posts.  Construction quality was quite nice as well, being sturdy, hefty and clean looking, and the laminate was applied neatly.  The baffle is ¾” MDF mounted on a 5/8”particle board wrap, with a ¾” particle board back.  There is no internal bracing, due in part to the small design and limited bandwidth of the speaker.  The cabinet is stuffed with polyfill material.

Don't MOVE, we've got you Surrounded!

I set up the 55-tripoles on the side wall of my listening room such that the bottom of the speaker was about 2 feet above my ears when seated in the primary listening position.  After adjusting the levels of all the speakers in my system,  I broke out the DVDs.  I am very familiar with the ADP surrounds in my reference system, and fully understand their qualities and limitations.  So why was I so surprised when I heard such a marked difference in the rear channels with the tripoles?  Simply put, when “surround sound” was called for, the dipoles moved to front stage.  When a soundtrack demanded pinpoint accuracy, the direct radiators kicked in.  As movie scenes panned from back to front, there was good timbre matching with the tripoles and front speakers, as high frequencies were right on, due in part to the direct radiators.  (One of the downsides to using a dipole or bipole is some high frequency information is lost because of the 90° angle created by the speaker and listening position.)  An example would be the Dolby Digital  “City (helicopter) Trailer”, where the chopper moves from back to front and vise versa.  The pan was smooth and almost seamless with the 55-tripoles.  But what about when soundtracks call for both diffuse AND direct?  No problemo for the 55-tripoles.  Several scenes in the movie "End of Days" include background sounds coming from people and automobiles on the streets of New York City, while simultaneously, specific sounds are directed to either the left or right rear speaker.  With the 55-tripoles, diffuse and direct meshed nicely, providing a very real sense of being on the crowded streets of New York (“Hey, watch it, buddy!”).

On the DVD "Terminator 2: Judgement Day", the Dolby Digital transfer proved to be a good test for the 55-tripoles.  During the famous canal chase scene, you find yourself glued to the screen with every move the T-1000 makes, while he chases John in the semi, not really noticing some of the sounds coming from all around.  I can remember the first time I watched this scene at home; the rear channels may as well have been off!  The rear channels are full of percussion and all sorts of clicking sounds.  With the 55-tripoles, I was not only confronted with visual delight, but also surrounded by an equal amount of audio excitement, making the scene more enjoyable.

(All screen shots copyright the respective studios.)

The boat-chase scene in the beginning of James Bond’s "The World is Not Enough" makes good use of the stereo surrounds on the DVD transfer.  Of particular mention is the water splashing from the front action, panning to the rear left or right.  Again, the 55-tripoles did a great job of relaying a near-realistic environment (“Honey, is the roof leaking again?!)  Several scenes had some very subtle surround information present.  On a couple of occasions, my wife said with a worried voice, “Ralph, please go see who’s outside!”   I tried to reassure her that the sounds were coming from the movie, but to no avail.  Needless to say, the streets of New Jersey were very quiet that night!

I discovered early-on that proper balancing and placement of these speakers are key to getting the 55-tripoles to sound right.  If not properly set up (as is the case with most speakers), imaging will be off, which will create unwanted distractions, specifically coming from the front radiator portion of the speaker.  But once properly set up, these speakers produce a sound field that is very well balanced no matter where I sat.  This was especially noticeable when listening to 5.1 audio soundtracks.  Again, no matter where I sat, either in the ‘sweet spot’ or off center, the sound was still very balanced with no distractions from sounds ‘leaning’ toward one side of the room as I moved closer to the left or right speaker.  The 55-tripoles even made some of those annoying music surround modes (DSP) almost listenable (almost, but not quite).  If you want significant bass in your surrounds, you’ll have to use a subwoofer with these speakers.  With an F3 of  87 Hz (usable bass down to about 80 Hz),  bass extension is a little on the weak side, but not surprising for a surround sound speaker.  M&K’s  new SS-200 and SS-250 tripoles are larger and can extend lower, but, of course, for more $$$.

I replaced my main speakers with the tripoles and listened to CDs without the aid of a subwoofer.  Soundstage was good with these little puppies.  I would describe them as slightly “bright”.  I suspect that is an artifact of not having enough bass to balance things out, rather then being a reflection on the tweeter.  Replaying the same tracks with a subwoofer softened things up a bit.  I was able to get them up to 95 dB at the listening position before audible distortion was obvious, but even then, the woofer kept its composure, pumping back and forth without “popping” the voice coil (one of the benefits of a sealed design).  Midrange was clean, well controlled, and well-defined.

That's a wrap!

Can everyone afford a pair of MSRP $699 surround speakers? Perhaps not.  But if you’re serious about the way you listen to movies, you certainly owe it to yourself to go out and audition these speakers just to see what tripole technology can offer.  Then you can determine for yourself whether they’re worth the bucks.  I definitely think they are. I’ve emphasized the fact that one weakness this speaker has is its lack of bass.  However, one would not expect a lot of bass coming from a surround sound speaker design.  That’s not its intention.  I suspect that any home theater fanatic who really likes bass in the surrounds will devote a subwoofer for that task.  To them, I say “Go for it!”  M&K makes some great subs that would be perfect for this job. The 55-tripoles are still hanging on my wall.  I suspect they’ll stay there for some time.

Equipment used during this review:

B&K AVP2000 DPL preamplifier

B&K AV5000 5-channel power amplifier

Yamaha YST-SW200 subwoofer

Audio Concepts custom built DIY Titan subwoofer

Audax custom built A652 DIY loudspeakers

Paradigm CC-300 center channel speaker

Paradigm ADP-150 surround speakers

Marantz DP-870 Dolby Digital Decoder

Panasonic A310 DVD Player

Pioneer CLD-D703 Dolby Digital modified laserdisc combi player

Audioquest and Nordost Flatline interconnects


- Ralph Calabria -


© Copyright 2000 Secrets of Home Theater & High Fidelity
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