This one is the Balanced Force 212. It has two massive 12” drivers operating in bipolar motion (both drivers move in or out of the enclosure at the same time), balancing out any tendency for the enclosure to move.
Dual 850-watt (3,400 watts peak total) amplifiers drive the system to window-rattling levels that will satisfy anyone’s intent to deliver realistic Star Wars-spaceship-engine noise and certainly impress more than a few friends.
Priced at $4,499.99 USD, and weighing in at 140 pounds, this is something that will take your home theater (and stereo audio system) to new levels of enjoyment.
Martin Logan Balanced Force 212 Subwoofer
- Dual 12″ drivers
- Dual 850 watt power amplifiers
- Control panel on top for easy access
- Massive build
- Programmable frequency response
I have always been a huge fan of subwoofers because I really like deep bass. I have three 18” subs in my home theater and two subs, each with six 12” drivers, in my two-channel lab.
I also have experience with several of MartinLogan’s electrostatic speakers, but this is my first experience with their subwoofers.
The MartinLogan Balanced Force 212 Subwoofer has two 12” drivers in a bipolar arrangement and two 850-watt amplifiers (1,700 watts peak/each). Here is a diagram showing the difference between a bipolar and dipolar driver configuration.
In the top part of the diagram, you can see the bipolar arrangement of the two drivers, each one moving in or moving out of the enclosure at the same time. This contrasts with a dipolar arrangement, shown in the lower part of the diagram, where the drivers are moving in opposite directions (diagram copyright DiyAudio). Speakers with open baffles on the rear (rather than a second driver) are effectively dipolar.
Two Drivers, Two Power Amplifiers
Two 12″, Bipolar Arrangement
CROSSOVER FREQUENCY (LOW PASS):
80 Hz – 30 Hz, Variable
18 Hz – 120 Hz ± 3 dB
25 Hz BOOST / ATTENUATION:
± 10 dB
Perfect Bass Kit (PBK)
Compataible with ARC Genesis
RCA, XLR, Speaker-level,
Trigger, USB, PBK
The Balanced Force 212 is a very heavy subwoofer weighing in at 140 pounds. In part, this is due to the 12” drivers being massive. That is necessary if one wants a subwoofer to put out massive sound.
In the photo below, you can see that the Balanced Force 212 enclosure is a trapezoidal shape, but the drivers are effectively sloped so that the inside of the enclosure is more of a square box. I removed the grille for this photo so you can see the driver on one side. Notice that it is not parallel to the trapezoidal side. It is parallel to a square shape.
Here is a closeup photo of the control panel on the top of the subwoofer.
At the top is the MartinLogan logo, illuminated by throwing a toggle switch just beneath the logo. You can turn it on or off according to your preference.
The volume control (Level) is next, followed by a dial that lets you boost or attenuate the sound at 25 Hz. I didn’t find this necessary, so I left it at the zero setting.
The Low-Pass control is used to set the crossover frequency between 30 Hz and 80 Hz. For the bench tests, I set it at 80 Hz (except where specified), but in use with speakers, I liked it set at 40 Hz. Of course, this depends on your speakers.
The phase dial is the lower-most one in the photo. This adjusts the phase-angle of the deep bass sound. You have to do this by ear. Play some music with deep bass and turn the dial until it “sounds” the most appealing.
At the bottom are push buttons to play a Tone Sweep (120 Hz to 20 Hz). This lets you find out if you have anything resonant in your listening room so you can fix the problem. I ran this test and found a resonance in the 100 Hz – 120 Hz range. The spectrum below shows the sweep from left to right. I used an accelerometer for this test. There is a large peak in that range. Since it is above the highest crossover (Low-Pass) frequency of 80 Hz, it is not a problem that would be caused by the subwoofer.
A piece of smoked glass comes with the subwoofer, and it covers the top panel when you are not accessing it.
A diagram of the rear panel is shown below.
You can see that this subwoofer has just about every type of input that one could possibly want, including RCA and XLR inputs for left and right channels, speaker level inputs, and USB/PBK (Perfect Bass Kit). The Perfect Bass Kit is an optional item that lets you perform room correction, and is compatible with ARC Genesis. The PBK input is used for this, and it is a mini-USB port that is connected to your computer on the other end. The “USB Input” on the panel is used for updating firmware and loading MartinLogan speaker-specific custom low pass filters that can be downloaded from the MartinLogan website.
The LFE input is connected to your surround sound processor, and the “Multi Out” jack is for daisy-chaining several subwoofers.
Room EQ and Custom Low Pass buttons on the top panel toggle the PBK curve or Custom Low Pass curve (see two photos above).
The RCA inputs are 10 kOhms, and the XLR inputs are 30 kOhms. I used the XLR inputs fed from the XLR outputs on my preamplifier.
I listened to the MartinLogan Balanced Force 212 Subwoofer using a pair of Sonus faber Electa Amator III Speakers with a computer (PC) delivering Tidal music streaming via USB input to an OPPO UDP-205 Universal Player, a hard drive connected to the UDP-205 with my entire digital music collection stored on it, VPI-HR-X Turntable with Sumiko Palo Santos MC Phono Cartridge, Manley Labs Steelhead Phono Preamplifier, Pass Labs Xs Preamplifier, Pass Labs Xs 300 Power Amplifiers, Classé SSP-800 Surround Sound Processor, Parasound JC 1+ Monoblock Power Amplifiers, Pass Labs X600.8 Power Amplifiers, Sony 75″ UHD (4K) Flat Panel Display, MartinLogan Summit X Hybrid Electrostatic Speakers (2) (Rear Left/Right), MartinLogan Stage X Hybrid Electrostatic Speakers (3) (Center and Sides Left/Right), Wireworld XLR cables, and Clarus Crimson speaker cables. I used a Clarus Concerto Power Conditioner for the computer, OPPO UDP-205, Manley Labs Steelhead Phono Preamplifier, and Pass Labs Xs Preamplifier. There is no power conditioner out there that will handle the two Pure Class A 300 watt Pass Labs Power Amplifiers, especially when the computer, universal player and preamplifier are also plugged into it. In particular, the Xs 300s are wired for 240 volts because they are huge-demand amplifiers weighing 300 pounds each. I placed the two Electa Amator III Speakers about 10 feet apart, angled inward at about 15 degrees. The listening position was about 12-15 feet from the speakers. I set the Balanced Force 212 Low-Pass filter to 60 Hz.
Complete List of Reference Components: OPPO BDP-105 Universal Player (4), OPPO UDP-205 Universal Player (2), VPI-HR-X Turntable with Sumiko Blackbird MC Cartridge and Sumiko Palo Santos MC Cartridge, Manley Labs Steelhead Tube Phono Preamplifier (2), Balanced Audio Technology VK-5i Pure Class A Triode (Tube) Stereo Preamplifier (2) (Fully Balanced), Balanced Audio Technology VK-500 Solid State Stereo Power Amplifier (Fully Balanced) (250 Watts per Channel), Pass Labs Xs Preamplifier, Pass Labs Xs 300 Monoblock Pure Class A Power Amplifiers (2) (300 Watts/each), Parasound JC 1+ Monoblock Power Amplifiers (2), Lamm LL1 Signature Stereo Pure Class A Triode (Tube) Preamplifier, MartinLogan CLX Full-Range Electrostatic Speakers (2), Sonus faber Lilium Speakers (2), Paradigm Reference Signature SUB 2 Subwoofers (2), Custom-Built Computer for Audio Analysis, Accupel HDG-3000 Digital Color Signal Generator (1080i capable), Component Video and DVI Output, ColorFacts Pro Video Test and Calibration Software, Version 6.0, Spyder Sensor, SpectraPlus Audio Analysis Software, Audio Precision SYS-2722 Spectrum Analyzer, Staco 3PN2210B-DVM 22 Ampere Variable Transformer (for adjusting line voltage to 120 volts during amplifier power output tests), Pass Labs XP-20 Stereo Preamplifier, Classé SSP-800 Surround Sound Processor, Emotiva XMC-1 Surround Sound Processor, Classé CA-5200 Five-Channel Power Amplifier (200 Watts per Channel), Pass Labs X600.8 Power Amplifiers (4) (600 Watts/Each), Audio Control Phase Coupled Activator (Sub-Harmonic Generator), Carver Platinum Mark IV Ribbon Speakers (2), MartinLogan Summit X Hybrid Electrostatic Speakers (2) (Rear Left/Right), MartinLogan Stage X Hybrid Electrostatic Speakers (3) (Center and Sides Left/Right), Velodyne DD-18+ Subwoofer (3), HiFiMAN HE1000 Planar Magnetic Headphones, OPPO PM-1 Planar Magnetic Headphones, OPPO HA-1 Headphone Amplifier, Bryston BUC-1 USB Converter, Sony VPL-HW55ES 1,920 x 1,080p Digital Projector, 90″ (Diagonal) Stewart Grayhawk Projection Screen, Sony 75″ UHD (4K) Flat Panel Display, Clarus Audio and Wireworld cables, Clarus Concerto Power Conditioner with Crimson Power Cable.
Music – Copland: Fanfare for the Common Man – Telarc, CD-80078 – Released 1982.
This disc is my go-to music album for testing subwoofers. The intro has bass drum thuds that are beyond description. I have listened to a number of other albums with this particular composition, and none of them have the intensity that this one does. It is available on Amazon for 10 bucks.
The Martin Logan Balanced Force 212 did the music justice, and I had to make sure the framed photos on my wall were securely fastened. The sound was deep and penetrating.
I also listened to this album with my larger floor-standing speakers, and the MartinLogan subwoofer helped. Floor-standers cannot really handle extremely deep bass regardless of the design. The 20 Hz – 30 Hz region requires a separate component.
Here is a spectrum of the first few seconds of the Fanfare. The red spectrum is from the segment played internally in the computer from out to in, no subwoofer, no microphone. The green spectrum is with the segment played through the Balanced Force 212 subwoofer with a microphone placed at head listening height (as if you were sitting in a chair), about 1 meter from the subwoofer. The dips such as at 17.5 Hz, 22.5 Hz, and 25.5 Hz are due to standing wave cancellations. These change depending on the microphone position. Note that the 212 reproduces the signal all the way down to 10 Hz (low pass crossover set at 40 Hz). Very, very nice result. This is not a test anyone has ever used before in a consumer audio magazine, at least, I cannot find any. Nonetheless, it is very demonstrative.
Music – Art Pepper: Picture of Heath – Pacific Jazz Records/Blue Note – Released December 31, 1997.
Jazz isn’t something where you would think you might need a subwoofer, but some of the string bass notes get down there, and a good sub helps. It certainly made a difference with this album, not only with the string bass but also with the drum solos.
And hey, Chet Baker joined Pepper here, so how can you lose?
Movie (4K) – Prometheus – 20th Century Fox – 2012.
In this prequel to Ridley Scott’s 1979 masterpiece, Alien, a discovery of the possible origin of the human race leads astronauts on a dangerous journey to a distant moon, where they find some very nasty organisms.
The deep bass engine sounds are amazing, and the Balanced Force 212 did the job admirably. It really looks great in 4K too. If you want to impress your neighbors with your movie surround sound system, this movie is a must-have.
Music – Bach: The Organ Works – Helmut Walcha – Archiv Produktion – Released December 31, 1999.
How could one test a subwoofer without pipe organ music? And Bach would be a good choice. So here it is. The Toccata and Fugue in D Minor is perhaps his most famous composition. There are plenty of recordings out there, and this is a good one. The pedal notes were reproduced beautifully by the 212. Note that a good subwoofer has powerful amplifiers because it takes plenty of it to reproduce deep bass. The Balanced Force 212 has dual 850-watt amps, 3,400 watts total peak. Ten watt Class A tube amps won’t do it here guys. Massive raw power. Got to have it. If that causes your electric bill to increase, just suck it up. High-end audio is not a bargain hobby.
The Impulse Response (IR) is shown below. Bench test measurements were taken with the microphone 1 meter from one side of the subwoofer (facing one driver) at the driver center level, except where noted.
You can see that it is very complicated because there are two drivers on opposite sides of the subwoofer.
The frequency response is derived from the IR, shown below.
In general, it is a decreasing response from about 65 Hz to 12.5 Hz. Distortion is at a maximum at 12.5 Hz, which is expected, and a minimum at 70 Hz. This is with an output of 100 dB SPL. The second harmonic is the largest of the three harmonics illustrated. The dips and peaks are due to standing waves. Although some room effects can be removed by measuring the frequency response derived from the Impulse Response, the standing waves are not removed.
Raising the output to 110 dB SPL, shown below, gives the same response curve, but the 2nd harmonics (blue line) are decreased, while the 3rd harmonics (gray line) are increased. This suggests stress, and I am not surprised.
Here is a calculated frequency response with all room effects, including standing waves removed. It is the realistic response, but only theoretical because room effects and standing waves are part of what is considered when designing the subwoofer. The curves shown above are what you actually get.
Measuring the room response from four different microphone locations, all about 1 meter from the subwoofer, and at different heights, the results are shown in the following graph. You can see that the most fluctuation (the result of standing waves) occurs between about 27 Hz and 60 Hz, compared to the region between 10 Hz and 27 Hz.
Here is a spectrum of a 30 Hz sine wave at 92 dB SPL. THD is 2.16% with the 2nd at 2.02%, the 3rd at 0.75%, and 4th at 0.039%. That is really good.
The oscilloscope trace for 30 Hz at 80 dB is shown below. It is clean.
Here is the Step Response. As with the Impulse Response, the Step Response shows two sets of peaks, one for each of the drivers.
The first driver’s response is from 1,355 ms to 1,368 ms, and the second driver begins at 1,386 ms and ends at 1,405 ms. Both drivers are in phase with one another as shown by the positive wave being the first part of each driver’s response.
The Cumulative Spectral Decay (CSD), shown below, indicates cabinet resonances that are over by about 2.5 ms.
The MartinLogan Balanced Force 212 is one of the three best subwoofers I have ever tested.
- Low distortion
- Plenty of inputs
- Massive build
- Cell phone app to control volume and upload various custom low pass filters
The other two are much more expensive. It is powerful, plays deep, distortion controlled, and is very flexible in terms of how you can set it up