When Ken Kreisel contacted me about reviewing his new subwoofers, there was little hesitation. After all, we have been using the original M&K (Miller & Kreisel) MX350THX subs in our home theater room for over 10 years along with a trio (left, center, and right) of the M&K S-150THX speakers and a pair of SS-250 tripole surrounds. When M&K Sound announced the closure of their operations back in 2007, many followers including myself were disappointed. However, like all great speaker designers, Ken Kreisel is resilient and could not stay dormant. His passion for speaker design has again emerged into a new company appropriately named KEN KREISEL. The first of the new speakers being launched are the DXD-12012 ($2995) and DXD-808 ($1995) subwoofers. Each have a similar configuration using a push-pull driver arrangement. The DXD-12012 features dual 12-inch drivers while the DXD-808 features dual 8-inch drivers. Instead of the traditional front-firing driver, the DXD series subwoofers are now side firing. The second driver is reverse mounted and points up into the cabinet just like the previous push-pull designs. Vents for the bottom driver occupy three of the four sides of the cabinet. This is not to be confused with a vented enclosure as this design is sealed.
It's not everyday we get the opportunity to review $20K worth of subwoofers at one time, so our excitement meter was pegged. On one side of our room we configured the DXD-12012 QUATTRO (four DXD-12012's) and on the other side the DXD-808 QUATTRO(four DXD-808's). Each DXD-12012 measures 24" x 15.5" x 20" (HxWxD) and weighs 78 pounds. The DXD-808 measures 18" x 11" x 14" (HxWxD) and weighs 46 pounds.
Each subwoofer comes wrapped in a black cloth cover to prevent scratches on the finish during shipping. There is plenty of hard foam in the over-sized box surrounding the heavy cabinet to prevent damage even from fairly large impacts. The first thing that strikes you when you pull the DXD-12012 out of the box is the sheer mass of this unit. Build quality is top notch with a high gloss piano black finish on the side panels covered in protective material. Each sub comes with a power cord and a set of rubber feet.
The DXD-12012 build quality is solid and weighs close to 80 pounds even with the state-of-the-art switching amplifier design, which is significantly lighter than traditional linear amplifiers. This subwoofer occupies about 2 square feet of surface area. The sealed box design has a "Q" of .5 - .707 (without active equalization), exhibiting excellent transient response with a natural roll-off of 12dB/octave. The high gloss piano black MDF side panels are 25mm thick with an additional 18mm panel on the driver side for additional reinforcement to the cabinet to reduce colorations due to vibration. The top panel is also 25mm and the rear panel is 18mm The body of the cabinet is covered with simulated black leather and features a reversible jeweled logo, allowing users to change it based on the orientation of the cabinet.
Optional Gloss Top
For those looking to match the top of the DXD subwoofer with the high gloss sides, an optional kit (see photo) is available that brings the glossy black look
to the top. Personally, I prefer the matte look for theater rooms since glossy surfaces tend to reflect light. Aesthetically, the gloss finish wins hands down and will greatly increase the SAF (Spouse Acceptance Factor).
The DXD-12012 uses two specially designed low-mass, long-throw drivers. The cone material is made from a very strong long fiber pulp blend which is designed to offer maximum strength and rigidity while maintaining minimum mass. The front of the cone is treated with a specialized coating compound. According to the company, the combination of the cone angle, dust cap diameter, shape and geometry provide optimum performance in both the forward and reverse directions. The nominal impedance on each driver is 4 ohms. The two drivers in the cabinet are not wired together, but instead have a dedicated mono amplifier independently controlling each of them. This approach ensures the highest performance with no electrical interaction between the two drivers. The spider uses a unique blend of cotton and pure NOMEX for extreme linearity, low mass, high strength and durability.
The surround material is custom molded from a select NBR formulation (NITRILE RUBBER-acrylonitrile-butadiene copolymer), which provides minimum mass, maximum linearity, and a “Silent Running Suspension”™ system. Unlike foam-based surrounds, these are built to last and will not deteriorate like many of the designs from the past. According to Ken, the surrounds and spider really need to be heated up at least once or twice before they sound right. Ken recommends a preliminary "break-in" period of a good 20-minute to maximize performance. Ken is planning to provide a specially recorded break-in test disc in the future to maximize break-in effect and minimize break-in time.
The large magnetic structure uses an optimized undercut T-style pole piece design along with an aluminum shorting ring. These two elements allow for maximum magnetic field linearity and symmetry which in turn leads to reduced distortion and better controlled driver inductance.
Voice Coil Design
The ultra high temperature voice coil is precision wound on a black anodized aluminum bobbin for maximum cooling and uses Asymmetrical Centering to ensure Optimized Magnetic Field Symmetry, which is necessary for low distortion. The driver uses something called Airflow Maximizer Design™, where perforations behind the dust cap forces hot air to
exhaust and cool air to be drawn in around the voice coil. These perforations can be seen when you look at the back of the cone near the spider.
Depending on your configuration it would be a good idea to provide adequate power to these subwoofers, especially if you plan to use the QUATTRO configuration as we did. Our dedicated 20 amp outlet was used for our testing. We noticed power consumption was less than 10 watts total in the standby mode which is pretty impressive. When the subs go into the active mode the power jumps up to around 100 watts total or 25 watts each with no input signal. During our testing the power jumped to well over 1000 watts according to our power meter. Since we used the XLR connections on the subs, we switch the power mode to "Always On". It should be noted that the subs do not auto sense on the XLR inputs. The DXD-808 back panel design is similar to the DXD-12012 and offers the same features.
The DXD-12012 uses an IEC style power connector minus the ground termininal. The fuse is rated at 8 amps. Inside the back panel, heavy 12-gauge wire is used to provide power to the main power switch.
The switched line power is then routed to the two mono amplifiers using 14-gauge wire. Although it might be viewed as overkill for such short cable runs, it is certainly nice to see such attention to detail. The heavy duty power cable provided with the subwoofer is rated for 13 amps.
Controls for input Level, Phase and Crossover Frequency are provided with GREEN dots indicating the default positions when used with a typical surround processor or receiver. The Low-Pass filter control is bypassed when the Low Pass filter switch is in the Bypass mode. We let the Anthem AVM 50v A/V processor take care of the level and crossover frequency and used the default settings (green dots) on the back panel.
The front-end circuit used in the new KEN KREISEL™ DXD-series subwoofers provide the analog audio processing for both balanced (XLR) and unbalanced (RCA) input interfaces. The balanced (XLR) input uses a professional-grade differential circuit, which can sometimes help eliminate hum in some configurations. There is no digital signal processing used in this subwoofer and the entire signal path stays in the analog domain. The back panel includes a direct pass-through to facilitate connecting multiple subwoofers without the need for re-buffering the input signal. We connected four DXD-12012 subs together using balanced XLR cables. It should be noted that each subwoofer presents a load on the input. When connecting four of these subs, the line impedance will drop by a factor of 4. Users need to make sure their A/V processor or receiver is capable of driving this load.
The active front-end circuitry includes various opamps (TL072, TL074, and LM2902) in the signal path. The circuit provides the complementary drive signals to the two mono power amplifiers. This design topology is common to both the DXD-12012 as well as the DXD-808. In the DXD-12012, the two identical, but separate amplifier modules are mounted on the back panel along with the front-end electronics. The DXD-808 is similar, but has one of the amplifier modules mounted inside of the cabinet due to limited real estate on the back panel.
The DXD-12012 and DXD-808 use newly developed Claridy™ amplifiers in the subwoofers. The company calls them Dual Class-D Push-Pull Cross-Coupled High Current - Hybrid Bridge Monoblock™ amplifiers with Dual Integrated Cross-Coupled High Speed Switching power supplies. That sounds like a lot of fancy marketing talk, but in reality it is a clever idea. We will try and explain what it all means in this section. First of all, subwoofers need a lot of power and it is advantageous to use efficient power supplies and amplifiers to minimize not only the quiescent (idle) power dissipation, but the heat being generated when the subwoofer is under heavy load. Due to the high efficiency of this subwoofer, no additional external heatsinks are required.
The DXD series subwoofers have two completely separate power amplifier modules, which include the switching power supply and the Class "D" amplifier section. At any given time when an amplifier is driving a speaker, only one phase (positive or negative) of the two amplifiers is required to supply significant current. The diagram on the left shows the two speakers (and amplifier outputs) out-of-phase (acoustically in-phase) with the amplifiers pulling from opposite rails at any given time. By connecting the two power rails together, the power reserve from one amplifier is shared with the other when the other is not using it. As a result, twice the power supply reserve is available thanks to the other power amplifier. The concept makes a lot of sense and it works well. Ken calls this the balanced Hybrid-bridge Push-Pull™ configuration. Cool name, but until I looked at the circuit topology and understood what that exactly meant, I was scratching my head.
Each monoblock amplifier is conservatively rated to provide at least 375 watts RMS of power. The efficient switching power supply uses a pair of 200-volt, 1800 micro-Farad capacitors. The power amplifier has a pair of 80-volt, 6800 micro-Farad filter capacitors, which operate at approximately + 70 V. All of the high quality capacitors are made by NIPPON CHEMI-CON. Heavy 14-gauge wire is used between the amplifier and drivers. All too often I find subwoofers using cheap under-sized wire inside of the cabinet. While it saves on cost, it is not desired.
The DXD subwoofers are designed to be stacked in DUO or QUATTRO configurations. There are two different stacking bracket kits depending if you have the DXD-808's or DXD-12012's. The DXD-808 bracket kit includes four 5mm thick (50mm x 50mm) rubber pads with adhesive, four 3mm thick (50mm x 50mm) rubber pads, and two small brackets with 8 screws. The DXD-12012 kit includes everything the DXD-808 kit includes with the addition of a large center bracket adding additional strength for holding the larger cabinet. The 5mm pads are attached to the bottom of the first cabinet and the other 3mm pads are used to interface between each of the additional cabinets as they are stacked. The kits work very well and keep the cabinets compliant and stable.
Each of the mounting plates has a thin rubber backing to prevent scratching the subwoofer surface when installed. This was a smart idea that appears to work well. Large screws hold the plates firmly in place. It might have been a good idea to include locking hardware with the screws because under heavy use these screws seemed to work their way loose due to vibration.
Stacking four of these 80 pound subwoofers is no easy task and with the help of my wife, I was able to clear the ceiling by a mere half of an inch. After stacking the 320+ pounds worth of subwoofers, my back needed a rest. One benefit of stacking these subs in a DUO or QUATTRO configuration is by alternating the orientation of the cabinets, users can greatly reduce cabinet vibration thanks to the conservation of momentum. In order for the stacking to work at its best, the sub output levels need to be precisely matched, which means using the REFERENCE LEVEL (green dot) setting. This is easy to do since the level control has a "0 dB" mode when clicked into the minimum position. Do not attempt to set the "0 dB" setting near the 12 o'clock position as it will not be as accurate as the default setting. Once configured, the QUATTRO setup worked well and even at higher levels with enormous bass output, little cabinet vibration could be felt. The brackets also prevent the subs from shifting.
Our A/V system is currently centered around an Anthem AVM 50v 3D A/V processor capable of decoding uncompressed multi-channel dts-HD Master Audio and Dolby TrueHD bitstreams. The AVM 50v preamp is connected to a 5-channel Parasound HCA-2205AT amplifier that is used to drive a trio of M&K Sound S-150THX front channel speakers and a pair of Surround 250 Tripole speakers in the rear. Our music sources were played on OPPO's BDP-105 universal audiophile blu-ray player. We also used a Dish Hopper high definition satellite receiver for source material. The AVM 50v is configured with the THX crossover
set at 80 Hz, which works well with our main satellite speakers. We ran the Anthem Room Correction (ARC) to set the levels and delay times for all channels. The StudioTech U-22T cabinet in the center holds all of the A/V gear used to test these subwoofers and has been recently redesigned to provide even more functionality.
Connecting the Sub
The Anthem AVM 50v provides up to two balanced XLR subwoofer outputs that allowed us to connect directly to the DXD-12012's or DXD-808's. We then daisy chained from the first sub to the remaining three subs to complete the QUATTRO configuration. The pass-thru interface on the sub's back panel is un-buffered, so each additional subwoofer will put an additional load on the preamp output as mentioned earlier.
We also ran a series of tests with the subs configured as two DUO's allowing us to have stereo subs in our listening environment. This can be a little more difficult and challenging since the interaction between the subs can sometimes cause cancellations in the low frequencies.
The DXD-808 and DXD-12012 subs have obvious differences such as driver and cabinet sizes, but share the same power amplifier design. The bass reproduction from the two designs also exhibit different charateristics and each have their advantages and disadvantages. Reproducing music is in many ways less forgiving than what we might expect with playing back movie soundtracks. Many of us have trained our ears to hear subtle differences with transient bass response of instruments. What I found was the DXD-808's had the ability to be fast, tight and agile with bass reproduction. The smaller DXD-808 design also offers substantial bass output particularly in the QUATTRO configuration, while being able to reproduce detail in the upper bass region where many larger subwoofers struggle. One of my favorite studio recordings is Steely Dan's Gaucho in DTS 5.1. This music was originally recorded between 1978-1980 (mixed by Elliot Scheiner), which won the 1981 Grammy® for “Best Engineered Recording, Non Classical”. Elliot Scheiner also re-mixed the newer 5.1 DTS version.
Moving to the DXD-12012 was a whole different experience offering substantially more bass output while effortlessly hitting deeper notes. Neither of the subs sounded boomy or uncontrolled, but for music I might lean towards the DXD-808's agility. I also enjoyed the dual DUO configuration for music, balancing the bass between the front channels. It is largely a personal preference and is worth experimenting with. The Room Gain Optimized EQ setting was my preference over the other EQ settings and I think this is why Ken chose this EQ setting as the default.
When watching movies, I am usually searching for a slightly different set of criteria and the DXD-12012 QUATTRO delivered the goods. Pushing these subs hard was never a problem and with eight 12-inch drivers synchronously moving air in-phase allowed the subwoofer system to produce mind-boggling output levels with plenty of headroom. Movies with low-frequency sound effects such as Jumper, provided the cinematic impact only the best systems are capable of acheiving. It brings the movie experience to a whole new level.
For the first time the structure in our theater room began to rattle at these high volume levels. This was not too surprising given that each of the eight 12-inch drivers have a dedicated 375+ Watt (rms) amplifier behind them. Thankfully, nothing fell off the walls and no glass broke, but I can tell you that you will be hard pressed to find a more effective subwoofer system for watching movies in your listening environment all while remaining tight and accurate.
We played a few selections from DTS' Bluray demo disc #15 and #16. These demo discs provide a collection of both music and movies with excellent fidelity, utilizing uncompressed dts-HD Master Audio as the multi-channel bitstream. The DXD-12012 QUATTRO subwoofer system delivered amazingly tight and powerful bass without any signs of running out of steam with these reference clips. Some of the best demos were Tron: Legacy, Red: Special Edition, X Men: First Class, and Sucker Punch. DTS has a history of pulling some of the best material together and releasing them as exclusive demo discs.
The DXD-12012 and DXD-808 subwoofers are excellent designs and I have never experienced this level of precise, high impact bass reproduction in my home theater room. Sure, we have had some excellent subwoofers in the past and many of them I wouldn't hesitate recommending, but never has there been a configuration that produces so much effortless bass in the room at very high levels. My preference leans towards the dual DUO configuration even though it is a bit more difficult to tune. The QUATTRO has the advantage of producing a large wavefront from a single location, making it easier to place. There was no distortion from the subwoofer tower, but you will likely find new items that are loose in the house with these subs. I certainly wish my budget allowed me to have these as a permanent setup because the bar has certainly been raised.
The QUATTRO DXD-12012 subwoofer system retails for $11995 for the four DXD-12012 subwoofers ($7995 for the QUATTRO DXD-808). The configuration produces unparalleled bass output if cost is no object. I have never had the ability to reproduce this much bass in our theater room and while I had to dedicate a 20-amp breaker to the QUATTRO stack, it was well worth it.