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    Monolith 12" THX Ultra Subwoofer
    Product # 24457
    In Stock This item should ship today (12/14/2017) if ordered within 6 hours 50 minutes

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    Monolith 12" THX Ultra Subwoofer

    Monolith THX Select Subwoofer

    The Monolith THX® certified subwoofer sets the standard for bass output, low distortion, and affordability. With chest thumping bass that plays down to well under 20Hz, the Monolith subwoofer unleashes cinema level volume, with the ability to convey and articulate the subtle nuances of music.

    THX Ultra Certified
    500 Watt Amplifier

    THX Ultra Certified
    500 Watt Amplifier

    THX Ultra Certified: THX engineers completed hundreds of different scientific tests to ensure the highest audio performance possible. The tests ensure the speaker can reach the high volumes necessary to achieve THX Reference Level without creating audible distortion or artifacts. THX Certified Ultra products are for large sized rooms, up to 3,000 cubic feet in size, with a 10-12 foot viewing distance from the screen.

    12" Woofer: The Monolith 12" driver was developed from the ground up, with a design focus on achieving output, accuracy, dynamics, and linearity, while minimizing distortion. Enclosed in a cabinet made from HDF material, massive internal bracing, and outfitted with dual ports that can utilize a foam plugs to run the subwoofer in a sealed mode.

    500 Watt Amplifier: The 500W RMS amplifier is built around a Texas Instrument 48-bit data path (with 28-bit filter coefficients) and DSP engine. Each amplifier's transfer function, power output limiting and thermal protection are monitored to the millisecond and are customized for each individual driver. The high efficiency Class D amplifier modules are based on a proven topology that has been continuously refined over the past 4 years. The amplifier has vast reserves of power for highly accurate, deep bass for your home theater or music system.

    Performance Class

    THX Ultra

    THX Certified Ultra products bring the cinematic experience to large home theaters, 3,000 cubic feet in size, with a viewing distance of 12 feet or greater from the screen.*

    * Previously known as Select2

    Anatomy of a Subwoofer

    12-inch Subwoofer

    Cabinet and Internal Bracing

    HDF (High Density Fiberboard), not MDF, was utilized resulting in a sonically inert cabinet. Internal bracing has been strategically placed to increase overall cabinet strength and limit unwanted panel vibrations that would cause discoloration and distortion. The strong cabinet and bracing combine to ensure you hear massive amounts of bass, not cabinet resonances.

    Ports and Grille

    The 12" model uses a single 88.5mm port with inner and outer flares. Multiple ports are used to ensure high SPL capability at low frequency (fb=21Hz). The dual flares help reduce turbulence and asymmetrical distortions. Additional adjustments can be made by sealing one or more ports with the supplied plugs. The "floating" grille is made from non resonant MDF to provide rigidity, while the entire structure is offset from the cabinet to maximize air flow of the woofer and ports.

    12-inch Driver

    10-inch Subwoofer

    Every part of this driver has been developed from the ground up and customized to deliver high output, low distortion, and accurate bass. Our unique hybrid cone combines long fiber pulp and fiberglass, taking advantage of the pulp's superior stiffness with the additional rigidity and lightweight properties of fiberglass, to deliver a driver of massive durability and excursion. The result is a cone that achieves optimal motion at all frequencies it is asked to produce and beyond.

    1. Lower Suspension

    FEA (Finite Element Analysis) modeling and Klippel laser based optimizations were used to design a cone that is capable of astounding >80mm peak-to-peak excursions. The lower and upper suspensions are designed together with the motor structure. The lower suspension is critical for maintaining very low levels of distortion at high excursions, which are required for high SPL at low frequencies.

    2. Spider and Cone Venting

    The spider is made from multiple layers of NOMEX with integrated tinsel leads hand stitched in place for low mass yet high strength and durability. The purpose of these vents are twofold -- first, they allow convective air flow to cool the voice coil and, second, they reduce asymmetrical compliance due to air compression under the cone/spider, which would appear as unwanted distortions.

    3. Woofer Surround

    FEA (Finite Element Analysis) modeling and Klippel laser based optimization were utilized to create this durable, high profile surround that’s made from a unique formulation of NBR (NITRILE RUBBER-acrylonitrile-butadiene copolymer). This formulation was developed after months of modeling and prototyping to ensure the highest levels of excursion, without sacrificing linearity or distortion.

    4. Motor Structure

    The motor is made of CNC milled low carbon steel in the modified undercut "T" pole assembly to focus the magnetic flux. Dual aluminum shorting rings are used to cancel eddy currents, further stabilizing the magnetic flux and significantly lowering distortion. The precision wound, high temperature, all aluminum bobbin (which has a lower thermal compression than copper) enable the voice coil to remain cool. The motor and suspension design is extremely critical for maintaining control of the driver's displacement over a very wide range of input signals, allowing the subwoofer to reach maximum performance and output levels while keeping distortion to a minimum.

    All Amp'd Up

    12-inch Subwoofer

    The Monolith subwoofer amplifier has an extraordinarily high power output of 500 watts RMS (900 watts peak), which can deliver massive amounts of power when needed. Each Class D amplifier is built around a Texas Instruments 48-bit data path (with 28-bit filter coefficients) DSP engine, allowing virtually unlimited design flexibility with the assurance of no signal degradation. Each amplifier's transfer function, power output limiting, and thermal protection are monitored to the millisecond and are customized for each individual woofer and cabinet air volume combination. This state-of-the-art Class D amplifier technology ensures maximum headroom capability, excellent transient response, high output, and very low distortion when driving the Monolith 12-inch THX Select certified subwoofer.

    CEA-2010 SPL Measurements @ 2 meters

    12-inch Subwoofer

    12-inch Subwoofer

    Ported (2 ports)

      SPL @ 2m Distortion
    Hz Peak (dB) RMS (dB) THD% 2nd
    16 99.7 96.7 8.1% 3.9% 6.5%
    20 108.3 105.3 9.5% 3.4% 8.0%
    25 112.3 109.3 5.7% 1.3% 5.2%
    31 113.6 110.6 4.3% 2.6% 2.9%
    40 114.2 111.2 4.0% 2.4% 3.1%
    50 114.6 111.6 2.7% 1.5% 2.2%
    63 115.0 112.0 2.6% 1.1% 2.3%
    80 115.4 112.4 1.6% 0.8% 1.0%
    100 115.9 112.9 1.2% 0.7% 0.8%
    125 116.3 113.3 1.2% 0.7% 0.6%

    Ported (1 port)

      SPL @ 2m Distortion
    Hz Peak (dB) RMS (dB) THD% 2nd
    16 101.8 98.8 9.2% 1.3% 8.5%
    20 106.3 103.3 11.7% 5.5% 8.7%
    25 108.5 105.5 8.0% 4.6% 4.5%
    31 110.8 107.8 4.7% 3.2% 2.4%
    40 111.5 108.5 3.6% 2.6% 2.1%
    50 111.9 108.9 2.5% 0.8% 2.1%
    63 112.6 109.6 2.3% 1.3% 1.2%
    80 113.6 110.6 3.3% 1.7% 1.4%
    100 114.3 111.3 1.9% 1.1% 1.5%
    125 115.0 112.0 1.3% 0.8% 0.9%


      SPL @ 2m Distortion
    Hz Peak (dB) RMS (dB) THD% 2nd
    16 95.0 92.0 15.3% 2.4% 13.5%
    20 100.3 97.3 17.1% 3.1% 15.4%
    25 105.4 102.4 12.7% 4.3% 9.9%
    31 108.1 105.1 3.5% 2.0% 2.3%
    40 109.9 106.9 2.9% 1.4% 2.1%
    50 110.9 107.9 2.2% 0.7% 1.2%
    63 112.1 109.1 2.1% 0.9% 0.9%
    80 113.1 110.1 2.6% 1.1% 1.2%
    100 113.9 110.9 2.1% 1.1% 1.7%
    125 114.8 111.8 1.4% 1.0% 0.8%

    5 Year Warranty

    Buy with Confidence

    Monoprice not only stands behind every product we sell with a 5 year replacement warranty, we offer a 30-day money back guarantee as well! If the product you purchase does not satisfy your needs, send it back for a full refund.

    Quality at a Fair Price

    Quality at a Fair Price

    Monoprice's rugged design and rigid quality control standards deliver high quality products at fair prices.

    Hassle Free Packaging

    Hassle Free Packaging

    Monoprice exists to bring simplicity, fairness, and confidence to technology choices. This product features recyclable packaging that is simple to open, cost effective, with minimal waste, and fully protective as it travels to you.

    Service & Support

    Service & Support

    You're never on your own with Monoprice products! We have a full team of friendly and knowledgeable technicians available to answer your questions, both before and after the sale. Contact our technical support team for questions about our products, troubleshooting, or even suggestions for products to fit your particular needs. Not to be outdone, our friendly and helpful customer service team is here to make your ordering, delivery, and any possible returns a quick and painless operation, from start to finish!

    Support Files:

    THX® and the THX logo are trademarks of THX Ltd., registered in the U.S. and other countries.

    Model 24457
    Woofer 12" cone
    Cone Material 2 layer long fiber pulp/glass fiber cone
    Voice Coil 60mm with high temperature aluminum wire and black anodized aluminum bobbin
    Surround FEA optimized NBR (nitrile budadiene rubber)
    Motor FEA optimized, 2 aluminum shorting rings, undercut T-pole focused field
    Magnet Ceramic Y35, 2 pcs total 144 oz.
    Xmax 18mm (one-way)
    Xmech 80mm (peak-to-peak)
    Enclosure Sealed or vented HDF cabinet with horizontal and vertical bracing
    Finish Black Ash
    Amplifier Class D 500Wrms
    Frequency Response (-6dB) Sealed Vented (1 port) Vented (2 ports)
         Extended EQ 26-200Hz 19-200Hz 18-200Hz
         THX EQ 29-200Hz 23-200Hz 20-200Hz
    Harmonic Distortion <1% 20-100Hz (90dB @ 1m)
    Variable Level Control +15/-20dB
    Crossover Inline/Bypass variable 40-160Hz
    Inputs RCA (2), XLR
    Outputs XLR
    Signal Turn On Selectable always on/auto
    Auto Turn Off 30 minutes
    Dimensions (H x W x D) 22.8" x 16.7" x 23.6" (580 x 425 x 600mm)
    Net Weight 98.5 lbs. (44.7 kg)
    Gross Weight 125.7 lbs. (57 kg)

    Start typing your question and we'll check if it was already asked and answered. Learn More
    Browse 4 questions Browse 4 questions and 4 answers
    Can you add maximum SPL in the various modes (THX, etc.) to the spec sheets for all of these new subwoofers? Thanks!
    Jason G on Sep 2, 2017
    Monolith 12" THX Ultra Subwoofer
    Monolith 12" THX Ultra Subwoofer
    Monolith 10" THX Select Subwoofer
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    Monolith 15" THX Ultra Subwoofer
    Monolith 15" THX Ultra Subwoofer
    BEST ANSWER: We will be adding CEA-2010 @2M burst and RMS measurements by frequency in the near future.
    Can you please provide specifications in terms of power requirements for a North American household? I'd like to run 2 of these in my home theater currently under construction and want to know if I can run them both on the same dedicated 15 A circuit... or if I need to run them both on a dedicated 20 A circuit. Thanks!
    A shopper on Oct 27, 2017
    BEST ANSWER: I has a 20 amp circuit put in for this sub and a 12" SVS sub.
    Hello. I just looked at the manual and it appears the 10” goes lower than the 12 according to the manual. Is this correct?
    New User U on Nov 8, 2017
    BEST ANSWER: The 12" subwoofer goes lower and plays louder, as a 12" should. The Monolith 12" subwoofer has a 4 to 6 dB advantage over the 10" at 16Hz and 20Hz.
    Can these sub woofers be positioned on their side for a lower profile? I have a large projection screen and plan on placing two subs up front.
    Shawn P on Oct 29, 2017
    BEST ANSWER: Yes, you can lay the subwoofer on its side with no loss in performance.
    5.0 / 5.0
    1 Review
    5 Stars
    4 Stars
    3 Stars
    2 Stars
    1 Stars
    Hits better than my SVS SB 2000
    Great sub! Tested it out yesterday ,finally ,and i am impressed. I do not have complex measurement instruments but definitely plays louder and lower than my SVS. (As it should). Pleased thus far.
    December 11, 2017
    1 month ago

    In Stock This item should ship today (12/14/2017) if ordered within 6 hours 50 minutes