If you are visually impaired and are having difficulty navigating this site, please call our Customer Support line via our toll free number 1 (877) 271-2592.
    Monolith 15" THX Ultra Subwoofer
    Product # 24458
    In Stock This item should ship today (12/14/2017) if ordered within 6 hours 51 minutes

    Volume Pricing (Log In to see Member Pricing)

    Volume Pricing

    Qty: 1 $1,299.99
    Qty: 2-9 $1,249.99
    Qty: 10-19 $1,249.99
    Qty: 20-49 $1,249.99
    Qty: 50+ $1,249.99

    To see and take advantage of our member pricing sign up for a business account or contact our sales team.

    Learn more about Monoprice Business

    Monolith 15" 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 16Hz, the Monolith THX Ultra 15" Subwoofer unleashes cinema level volume, with the ability to convey and articulate the subtle nuances of music.

    THX Ultra Certified
    1000 Watt Amplifier

    THX Ultra Certified
    1000 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.

    15" Woofer: The Monolith 15" 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 three ports that can utilize foam plugs to run the subwoofer in a sealed mode, or tune it as you see fit.

    1000 Watt Amplifier: The 1000W 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

    15-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 15" model uses three 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 the port with the supplied plug. 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.

    15-inch Driver

    15-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 >90mm 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

    15-inch Subwoofer

    The Monolith subwoofer amplifier has an extraordinarily high power output of 1000 watts RMS (nearly 2000 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 15-inch THX Select certified subwoofer.

    CEA-2010 SPL Measurements @ 2 meters

    15-inch Subwoofer

    15-inch Subwoofer

    Ported (3 ports)

      SPL @ 2m Distortion
    Hz Peak (dB) RMS (dB) THD% 2nd
    12.5 91.0 88.0 12.0% 6.0% 9.7%
    16 106.3 103.3 19.8% 16.3% 10.9%
    20 112.6 109.6 12.5% 5.5% 10.6%
    25 116.6 113.6 7.1% 4.2% 5.5%
    31 119.5 116.5 5.4% 5.6% 2.2%
    40 120.9 117.9 3.1% 2.5% 1.6%
    50 120.6 117.6 2.1% 0.7% 2.0%
    63 120.0 117.0 2.1% 0.4% 2.0%
    80 118.7 115.7 1.5% 0.5% 1.3%
    100 120.1 117.1 2.9% 0.7% 2.4%
    125 120.2 117.2 1.3% 0.6% 0.8%

    Ported (2 ports)

      SPL @ 2m Distortion
    Hz Peak (dB) RMS (dB) THD% 2nd
    12.5 100.4 97.4 16.4% 11.8% 10.5%
    16 107.5 104.5 11.2% 6.5% 8.9%
    20 111.6 108.6 11.3% 3.5% 10.0%
    25 115.4 112.4 7.8% 5.9% 4.0%
    31 118.2 115.2 5.5% 4.8% 1.9%
    40 119.7 116.7 2.8% 1.9% 1.9%
    50 119.8 116.8 2.1% 0.6% 2.0%
    63 119.5 116.5 2.1% 0.4% 2.0%
    80 119.4 116.4 1.5% 0.5% 1.3%
    100 119.9 116.9 2.9% 0.7% 2.4%
    125 120.1 117.1 1.3% 0.6% 0.8%


      SPL @ 2m Distortion
    Hz Peak (dB) RMS (dB) THD% 2nd
    16 100.8 97.8 19.4% 8.6% 16.6%
    20 106.9 103.9 19.1% 8.3% 16.1%
    25 112.3 109.3 11.4% 8.7% 4.2%
    31 115.8 112.8 7.3% 5.7% 3.7%
    40 117.7 114.7 2.9% 1.4% 2.4%
    50 118.4 115.4 2.2% 0.4% 2.0%
    63 118.6 115.6 2.1% 1.9% 2.0%
    80 118.9 115.9 2.0% 0.5% 1.8%
    100 119.5 116.5 3.0% 0.6% 2.5%
    125 120.0 117.0 1.1% 0.6% 0.6%

    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 24458
    Woofer 15" 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 216 oz.
    Xmax 25mm (one-way)
    Xmech 90mm (peak-to-peak)
    Enclosure Sealed or vented HDF cabinet with horizontal and vertical bracing
    Finish Black Ash
    Amplifier 1000Wrms
    Frequency Response (-6dB) Sealed Vented (2 ports) Vented (3 ports)
         Extended EQ 15-200Hz 14-200Hz 16-200Hz
         THX EQ 23-200Hz 19-200Hz 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) 26.8" x 17.7" x 27.6" (680 x 450 x 700mm)
    Net Weight 128.5 lbs. (58.3 kg)
    Gross Weight 162.7 lbs. (73.8 kg)

    Start typing your question and we'll check if it was already asked and answered. Learn More
    Browse 5 questions Browse 5 questions and 4 answers
    Does this 15 inch subwoofer only play up to 90db before it distorts? Harmonic Distortion<1% 20-100Hz (90dB @ 1m) Does not seem to be very loud. Would think we need it to play at 105db with less than 1% distortion for a ultra THX theater.
    carl t on Sep 24, 2017
    BEST ANSWER: 90db@1M refers to sensitivity. It means that supplying 1 watt to the speaker will produce 90db SPL at one meter’s distance, usually reproducing pink noise. From this sensitivity statement, you can determine the speaker’s SPL at various distances when supplied with various wattages.
    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 15" THX Ultra Subwoofer
    Monolith 15" THX Ultra Subwoofer
    Monolith 12" THX Ultra Subwoofer
    Monolith 12" THX Ultra Subwoofer
    Monolith 10" THX Select Subwoofer
    Monolith 10" THX Select Subwoofer
    BEST ANSWER: We will be adding CEA-2010 @2M burst and RMS measurements by frequency in the near future.
    Is the finish a real wood veneer or a vinyl finish? Thank you.
    Ralph E L on Nov 19, 2017
    What kind of power supply is it? Linear or SMPS? 110-240v compatible?
    Jeff B on Nov 9, 2017
    Is this just a private label “last year’s model” SVS sub?
    A shopper on Nov 30, 2017
    BEST ANSWER: This subwoofer is not affiliated with SVS in any way. SVS subwoofers are not THX certified, and they have never produced a 15" subwoofer. The Monolith subwoofers have been designed and engineered from the ground up for us.
    There are no reviews for this item. Write Review

    In Stock This item should ship today (12/14/2017) if ordered within 6 hours 51 minutes