Product Review (September 2009) - MK Sound
S-150THX and MX-350 MKII THX Ultra Subwoofer

By Kevin Nakano

MK Sound - S150THX SystemIn early 2007, M&K Sound announced the closure of their operations in Chatsworth, CA after operating for 34 years. People like myself who have been using M&K speakers for years could not believe the company was closing their doors. Soon after their demise, the M&K Sound was auctioned off and a Danish company bought the rights to M&K's assets, including their intellectual property (IP). We met Chris Minto at this year's 2009 CES and discussed the path forward for the new company MK Sound. As part of their revised product line, MK Sound has re-released the legacy S-150THX ($1199 each) speaker system with SS-150 Surrounds ($1399 pair) and the MX-350THX subwoofer ($2399), all of which have been updated with significant changes using the latest driver and circuit design technology. MK Sound has also introduced the LCR950 series (with the SUR95T Surrounds) and the LCR750THX speakers. We had the opportunity to review the new S-150THX for our front LCR channels along with the new MX-350THX subwoofer. Our current speaker system uses the original S150THX speakers with a pair of original MX-350THX subwoofers, so it was of great interest to us to hear the new products.

MK Sound - S150THX

Legacy versus Latest
Our original S-150THX front channels have provided our home theater with reference quality audio for the past 8 years. Needless to say we were quite excited to hear the new S-150THX from the Danish company that took over M&K. Much of the original S-150THX remains intact with a newer and improved tweeter design that is said to offer lower distortion and more definition. The new S150THX speaker looks virtually the same as the legacy model we bought back in 2001. With slight differences in the cabinetry with smoother edges and a glossy finish. Sonically, they are surprisingly similar and in fact slightly more defined than what we currently have in our system. We say slightly because the sound is so similar it might be a matter of taste. Those who liked the original S150THX will most likely enjoy the sound of the new design.

MK Sound - S150THX

On the Back
The all-metal binding posts on the back of the new S-150THX speakers are similar to the old design and accept a wide variety of cable termination options. We connected banana plugs into our speakers and find that they work very well. What has changed on the back of the S-150THX is the mounting pattern. Since the new speaker has a smaller termination panel, the mounting patterns are provided on the top and bottom.

MK Sound S-150THX Impedance

S-150THX Impedance
The S-150THX has a nominal impedance rating of 4 ohms. We measured the impedance of the S-150THX using our Sencore SP295 Sound Analyzer, sweeping frequencies from 20-20kHz. The lowest impedance we measured was 3.3 ohms at 200 Hz. The peak impedance was 27.7 ohms at 2kHz. Our measurements concur with the nominal impedance rating of this speaker. We also recommend using a good, high current power amplifier given the impedance characteristics of this speaker.

MK Sound - MX-350THX SubwooferMX-350THX Subwoofer
The new MX-350THX subwoofer ($2399) takes on most of the attributes of the original design, yet has changed the main power amplifier from a traditional linear amplifier to a new high efficiency design. The push-pull dual driver configuration in a sealed cabinet delivers deep, high impact bass with excellent articulation. The design virtually eliminates even-order harmonic distortion by having both the front and back of the drivers work together to double the sound output while canceling out driver non-linearities. The result is in-room response flat to well below 20 Hz with amazing power and authority. The long-throw bass drivers use an undercut core with an asymmetrical voice coil mounting assembly with a very linear magnetic motor. The drivers look and feel much the same as the earlier design with treated cones. The surround material on our 8 year old MX-350THX subwoofers have held up well, so we expect the same longevity from the new design. MK Sound implements their proprietary Headroom Maximizer IV circuitry that is designed to prevent amplifier clipping for enhanced deep bass resolution with reduced distortion. The Linear Phase Low-pass Filter optimizes system performance and simplifies set-up. In virtually all cases, regardless of the room, listener location, or speakers, the overlapping acoustic output of the satellites and subwoofer will sum to create a seamless transition between the upper range of the subwoofer and the lower range of the S-150THX satellite speakers. MK Sound tightly controls the System Q, keeping the drivers, enclosure and the amplifier tightly damped (low Q), which results in extremely tight and articulate bass.

Instead of the rough matte black finish of the legacy subwoofer, the new MK Sound MX-350THX has a smooth satin surface that matches the finish of the new S-150THX speakers. The cabinet also has a nice thin cut along the top that adds to the modern look. MK Sound includes a set of rubber feet that screw into the base of the cabinet to adjust for uneven surfaces. They even provide a set of white gloves to keep finger print off the smooth surface when handling the unit.

The original MX350THX weighs 78 pounds with its linear amplifier and conventional power supply. The new MX350THX subwoofer weighs 56 pounds, 22 pounds less than the earlier design. The subwoofer measures 23.5” x 15.3” x 20” and has not changed in size. The cabinet is heavily braced and provides the most stable platform for the drivers to eliminate any resonances, buzzes and rattles that are common in cheaply constructed subwoofers.

Original M&K Sound MX-350 MK II Rear PanelLegacy MX-350THX
The original M&K Sound MX-350THX MK II subwoofer used a linear power amplifier to drive the pair of 12-inch bass drivers. The majority of the back panel was dedicated to a large heatsink to dissipate the power generated by the amplifier. The heavy cabinet design, drivers and the power supply and amplifier resulted in a subwoofer weighing almost 80 pounds. Power supplies for the USA and European markets are different, which further complicates the required inventory on the legacy design. The original MX-350THX MKII did not have a power switch, so once plugged in, it stayed on constantly. Some audiophiles prefer this as it keeps the amplifiers at a constant temperature for optimal performance.


MK Sound MX-350 MK II SubwooferNew MX-350THX
The new MX-350THX subwoofer has a much cleaner look on the rear panels thanks to the new BASH (Bridged Amplifier Switching Hybrid) amplifier technology. In addition to more power (400W versus 350W) with the new design, the BASH amplifier offers many benefits to subwoofer manufacturers that make it an attractive alternative to conventional linear designs. BASH takes the best of Class AB (sonic performance) and Class D (efficiency) amplifiers to create a new breed of power amplifiers. The result is a great sounding amplifier with excellent efficiency. In addition, the switching power supply design does not require heavy magnetics or large transformers making the overall amplifier much lighter and cheaper to manufacture. In addition, the design works with both 120V/60Hz (USA) as well as 220V-240V/50Hz (European) power with a simple fuse change.

The BASH amplifier tracks the incoming signal so that the amplifier’s supply rails are just above the amplifier’s voltage output reducing the amount of heat generated by the output devices. The sonic differences between the legacy design and the new design was somewhat noticeable, yet we did not hear a significant sonic advantage over the legacy design. Like the earlier design, the new MX-350THX subwoofer produced very satisfying levels of clean articulate low frequency bass for our audio and home theater system.

The three-way Power switch has the option of being set to Auto On that saves power when no input signal is detected. Some users may find this mode annoying as you have to wait for the subwoofer to turn on when music or a movie soundtrack starts. Keeping the subwoofer on also has the potential advantage of maintaining thermal stability for optimal audio performance. While most of the controls and features are the same from the earlier design, MK Sound has added a balance XLR input and pass-through on the rear panel. This is a great addition for those with long cable runs since this interface offers much better 60 Hz hum noise immunity.

The Low-pass Filter control can be set to one of three different settings. The first is the THX mode, which bypasses all low-pass filtering in the subwoofer and completely relies on the THX controller to provide the low-frequency signal to the subwoofer with the 80Hz and 24-dB/octave crossover characteristics. The variable mode allows the user to select the best crossover frequency for his/her setup with a variable control. The third setting is a fixed 80Hz and 24-dB/octave low-pass filter built into the subwoofer.

The Bass Level can be set to two different settings depending on the type of processor used in the system. The THX mode has a fixed level and is designed to be used with a THX certified processor. The variable mode allows the user to adjust the level of the subwoofer using the variable control. When using the variable mode, the setting marked Reference is the same level the THX mode uses.

The Bass EQ switch has two settings, THX and Anechoic. The THX setting produces the flattest response and is recommended for most installations. The Anechoic setting produces a flat anechoic response, which results in an increase in level below 30Hz due to room gain. This increase is about 12 dB/octave. The Anechoic setting is provided for measurement purposes and for those who might want this sonic profile. However, this setting limits the subwoofer's output and dynamic range.

The Phase switch is used to control the phase of the subwoofer output. There are two positions, "+" for in-phase and "-" for inverted-phase. The only way to know what the best setting should be is to try both and determine which position produces the highest level output. Positioning of the subwoofer as well as room dimensions affect the desired phase setting.

MK Sound MX350THX Subwoofers

Bottom Driver
The new MX-350THX has a different looking driver than the legacy design, but has similar build quality and construction. The large magnet structure used to be a concern for those with CRT-based displays, so M&K placed a second (bucking) magnet in the opposite direction to reduce the stray magnetic field of the woofer. This effectively cancels much of the stray B field, which can cause problems with conventional CRT displays. The older design had the additional magnet glued to the bottom as seen in the photo. The latest MK350THX MkII driver design has the bucking magnet integrated in the base of the driver. I also noticed the speaker wiring was a bit heavier in the older design, but this should not be an issue with the short wire run.

We didn't use the internal low-pass filter mode in the MX-350THX because our THX processor took care of this for us. Instead, we set the subwoofer crossover switch to THX and took advantage of our THX processor, which allowed us to seamlessly blend the MX-350THX with the our S-150THX front and SS-250 rear channels. While the SS-150THX surrounds may work well for the vast majority of home theater systems, we like the idea of having a full set of five S-150THX channels in our listening environment. For our review, we used our legacy SS-250 surround speakers in the rear to match the front channels and the results were spectacular.

Eagles - Hotel California DVD-AudioSystem Performance
Our review system took advantage of Denon's highly regarded AVR-5308CI receiver for the front-end electronics. This THX-Ultra2 rated receiver has amazing sound from an all-in-one unit. The crossover frequency was set to the standard THX reference of 80Hz. We used our OPPO BDP-83 Blu-ray player to provide a variety of source material from various disc formats. This player has excellent performance and supports Blu-ray, DVD-Audio, multi-channel SACD as well as most other formats. We played the DVD-Audio mix of the Eagles - Hotel California in 5.1 and it was quite an experience. The acoustic guitar on the Hotel California track sounded fantastic on this speaker system with transient detail as each string was picked. Deep bass reproduction was tight and made for an impressive demonstration of the system's capabilities. The sonic character of the new S-150THX maintains a well-focused image with minimal vertical dispersion to keep floor and ceiling reflections under control. The result is a focused sound without secondary reflections to blur the image. MK Sound recommends using an amplifier rated at 25-400 watts, but we feel anything less than 100W is insufficient for this speaker especially if you are expecting what we do out of this design. In our case, the Denon line level outputs fed a Parasound 5-channel HCA2205AT amplifier that provided excellent drive capability. The sound produced by the S-150THX speakers were both articulate and powerful, something not always easy for a speaker to do. We can see why they work so well for studio engineers who mix movie soundtracks. What I like most about the S-150THX design is the ability to drive these speakers hard and still get a satisfying and non-fatiguing sound from them. The new S-150THX is excellent and has much of the same character of the original design.

The MK Sound S-150 speaker system is designed for the serious audio and home theater enthusiast with a cost of around $8200 for five S-150THX channels and a single MX-350THX subwoofer. Build quality of this system is excellent and sets it apart from most of the multi-channel speaker systems we have reviewed. We were very pleased with the performance with music as well as movies.

Movie soundtracks were exceptionally clear and subtle nuances were reproduced with fine textures. Both Dolby TrueHD and DTS-HD Master Audio soundtracks decoded on our Denon AVR-5308CI delivered unprecedented resolution and dynamic range. The Blu-ray version of Wall-E demonstrated the virtual reality state-of-the-art animation can provide in our own theater rooms. Stunning picture quality accompanied by high resolution multi-channel audio made for an virtual world experience. The MK Sound S-150 system provided the ability to reproduce the soundtrack in its entirety from the subtle mechanical movements to the thunderous explosions of rocket engines firing. The MX-350THX subwoofer not only reproduced deep bass from these scenes, but did so in a way that didn't sound muddy or boomy. Bass reproduction was tight and punchy with the authority of well designed subwoofer. Even at higher levels the MX-350THX produced excellent bass without breaking up or bottoming out.

While MK Sound has recently changed hands, the company's product line continues to be solid and provides the sonic experience the original M&K was well known for. We are pleased with the new S-150THX speakers and MX-350THX subwoofer and believe customers will be quite happy with the build and sound quality. The original S-150THX speakers have a well established history in the professional audio industry with numerous awards for "Best Sound" on many popular soundtracks.

The S-150 Speaker System is designed to offer customers great sound with excellent build quality, whether the need is for home theater or audio. While the cost of the standard S-150 system ($7,400 retail) is significant, performance and build quality is among the best out there. For those looking to have the ultimate speaker system with five S-150THX speakers as well as a second MX-350THX subwoofer, the system price will jump to $10,800. We have been using the M&K S150 system for all of our reviews and have not had the urge to change speakers in eight years.

- Kevin Nakano

Light up your home with Lumigado Lighting

OPPO BDP-103 Blu-ray Player

Review System

Projector: Mitsubishi HC5500 1080p LCD Projector
Screen: Stewart Filmscreen 100" FireHawk Screen on a Luxus Deluxe ScreenWall
A/V Receiver: Denon AVR-5308CI THX-Ultra2 7x150W Receiver
Amplification: Parasound HCA-2205AT THX-Ultra Five Channel Amplifier
Front Speakers: Miller & Kreisel S-150THX (L+R) and S-150AC (Center) Speakers
Rear Speakers: Miller & Kreisel SS-250 Tripole® Surround Speakers
Subwoofer: Two Miller & Kreisel MX-350THX MkII THX-Ultra Push-pull Subwoofers
Thermal Management: Active Thermal Management Cool-it II Equipment Cooler
Room Treatments: Echo Buster panels and Bass Buster towers
Set-top Box: Dish Network ViP722 HDTV Satellite and Terrestrial Receiver with HDMI
Blu-ray Player: OPPO BDP-83 Universal Blu-ray Player
HD-DVD Player: Toshiba HD-A1 HD-DVD Player with HDMI
Remote Control: Remote Technologies Inc. T4 Controller
DVI Cable: AudioQuest DV-1 20m DVI-D Cable
HDMI Cables: VizionWare Hi-Wirez 20-meter, Accell 45-meter UltraRun HDMI Cable
A/V Cables: Ultralink Platinum and Advanced Performance Series Cables

Review at a glance

MK Sound S-150THX Speaker Specifications

  • Impedance: 4 Ohm
  • Frequency Response: 77 Hz – 20 kHz ±3dB
  • Recommended Power: 25 - 400 Watts
  • Finish: Black Satin

Dimensions (HxWxD): 12.5” x 10.5” x 12.5”
Weight: 21 pounds
MSRP: $1199 each

MX-350 MKII THX Ultra Subwoofer Specifications

  • Rated Power: 400 Watts
  • Frequency Response: 18 Hz – 200 Hz ±3dB
  • Low Pass Filter: Variable 50 Hz-125 Hz
  • Low Pass Filter: Fixed 80 Hz THX Filter Bypass
  • Finish: Black Satin

Dimensions (HxWxD): 23.5” x 15.3” x 20” (59.6 x 38.8 x 50.8 cm)
Weight: 56 pounds
MSRP: $2399

Company Information
MK Sound ApS · Denmark
Phone (International): +45 8619 8733
Email: (PRO), (CONSUMER)

Source: Manufacture Supplied

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