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TEST BENCH
Frequency response (at 2 meters)
LCR: 70 Hz to 19.5 kHz ±2.7 dB
surround: 35 Hz to 15.5 kHz ±4.7 dB
subwoofer: 20 to 92 Hz ±3 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input)
LCR: 89 dB
surround: 85 dB
Impedance (minimum/nominal)
LCR: 3.1/6 ohms
surround: 2.7/4 ohms
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters)
LCR: 63 Hz at 84 dB
surround: 63 Hz at 77 dB
subwoofer: 20 Hz at 89 dB SPL
102 dB average SPL from 25 to 63 Hz
107 dB maximum SPL at 40 Hz
bandwidth uniformity: 91%
The frequency-response curves shown in the graph are weighted to reflect how sound arrives at a listener's ears with normal speaker placement. Measurements were made at 2 meters to ensure that full effects of cabinet diffraction and front-panel reflections were included. All of the measurements shown in the graph were taken with the speaker grilles removed. The S-150THX was measured on a 6-foot stand. The SS-150 surround speaker was measured mounted on a plywood panel to simulate the effects of wall mounting. These tests gave quasi-anechoic results down to about 200 Hz. Response of woofers was close-miked and spliced to the quasi-anechoic response. The subwoofer's drivers were close-miked and summed.
The frequency-response curves of the S-150THX show inconsistent dispersion due to the speaker's asymmetrical design, which causes interference between the tweeters and woofers. However, once all the curves are averaged and weighted (with double emphasis on 30° off-axis), the result is a pretty flat response. The speaker shows a dip of about 5 dB at 2.5 kHz on axis, and rolls off above 17 kHz. At 30° off-axis on the woofer side, it exhibits a big dip between 1 kHz and 2.5 kHz. Adding the grille makes very little difference; it just adds a couple of very mild peaks and dips above 4 kHz.
Like a lot of multipolar surround speakers, the tripolar SS-150 produces all sorts of random-looking, hashy frequency-response curves at various angles. But it all averages out fairly well, again. The little speaker produces surprisingly deep bass response.
Impedance of these speakers is rather low, especially for the SS-150, which runs below 3 ohms at all frequencies above 1 kHz. Minimum impedance is 2.7 ohms at 2.2 kHz; nominal impedance is about 4 ohms. The S-150THX is a little more forgiving, with a minimum impedance of 3 ohms at 200 Hz and a nominal impedance of about 6 ohms. Sensitivity of the SS-150 is a little low at 85 dB when wall-mounted and about 83 dB on a stand, but that's fairly typical of a multipolar surround speaker. The S-150THX fares better at 89 dB.
The MX-350 plays all the way down to 20 Hz, and has a good average output of 102 dB between 25 and 63 Hz. These measurements were made with the crossover engaged; without it, the response is boosted at about 120 Hz and rather ragged above about 100 Hz; this sub was clearly intended for use with a THX crossover. The THX crossover built into the sub has a -3-dB point of 80 Hz. The THX EQ setting gives the response a bump of 2 to 3 dB below about 28 Hz.
—Brent Butterworth
I've been a fan of M&K Sound since the 1970's when Jonas and Ken had a Direct-to-Disc recording studio in Beverly Hills, CA. During that time I was an aspiring recording engineer and was invited to a recording session by a friend who was a 3M representative that supplied magnetic tape to M&K Studios. I've had the opportunity to work on and listen to numerous productions recorded/mastered on M&K speakers over the last three plus decades. In 2005 I purchased the 150 THX Speaker System for my newly built Home Theater/Media Room. The system includes two pairs of tripole speakers since my room is 40 feet deep. This also allows for a 7.1 surround sound format. All speakers are wall mounted (except the subs). The LCR's are mounted in front of a valance above the projection screen. The original set up employed two MX-350 THX subwoofers (Too Much Bass). We currently use only one sub wired to both the left and right inputs. This seems to increase the LFE by about 5 db. I wanted to purchase the surround speakers in a white finish, in an attempt to camouflage them. However, I was informed that M&K had stopped manufacturing the SS-150's in white about a year prior. I even visited their Culver City, CA factory in hopes of finding a pair or two. Visually, no one seems notice the black utility speakers. But Aurally, everyone notices them. Keep up the production of this fine, Reference Audio Reproduction System.
A Fan,
Art Copper
Los Angeles, CA