- Manufacturer & Model
- Monolith by Monoprice M-215 Dual 15" Subwoofer
- $2,499.99 Each - Internet Direct
THX ULTRA Certified
Two 15” Subwoofers with 2-layer Fiber Pulp/Fiberglass cone
60mm (2.362 Inch) High Temperature Aluminum Wire voice coil
FEA optimized NBR (Nitrile Butadiene Rubber) Surround
FEA optimized, 2 aluminum shorting rings, undercut T-pole
focused field motor assembly
108 OZ (6.75 pound) Y35 Ceramic Magnet Structure each speaker
– 216 ounces total
Slot vented HDF cabinet with internal horizontal and vertical
bracing with selectable foam plug voicing options
2000 watts RMS/3600 watts Peak Amplifier
THX Ultra Certified, this powered subwoofer is a MONSTROUS 216-pound bruiser, that digs deep, delivers punishing bass on demand and is housed in a large, but attractive package. Various voicing options are offered via a removeable port plug. This venting option effectively makes the subwoofer either a sealed cabinet or a ported cabinet design. The plugged option bringing a more controlled, tighter sounding subwoofer with the cabinet sealed at the sacrifice of a certain amount of ultra-low-end energy and efficiency. Or, with the port open, a deeper digging and more dynamic subwoofer. A two-thousand watt RMS Class D amp delivers the power and punch while effortlessly driving the two massive 15” subwoofers to earthquake inducing, breathtaking, chest crushing levels.
Cool, I thought! A speaker that I’m really interested in from a manufacturer I’m oh so curious about. The Monolith by Monoprice M-215 (Mfg Part# 38543) Dual 15” THX Ultra Certified subwoofer.
So, the arrangements were made and the only thing to do was sit back and wait for delivery!
When the box showed up on the back of a FedEx Freight truck and was delivered into my garage by the friendly FedEx driver, I began to get just a little nervous. After all I’m just an old dude living in a COVID-19 world where help is sometimes not that easy to come by! My worries stemmed from the impressive (Read: IMMENSE) size of the box delivered on a wooden pallet and the (now) nagging thought in my head that I might have…. just might have…. bit off more than I could proverbially chew.
Now, before you say it or think it! Yes, I knew exactly how big it was (42.3"H x 20.0"W x 27.6"D) and exactly how heavy it was (216 lbs). But, because of my overwhelming curiosity and desire to experience this subwoofer in person I pre-rationalized any possible issues with muscling this thing around right out of my mind.
It all worked out however, and it was certainly an interesting time to be had, and an interesting process to process. But, with a little planning, careful application of leverage, a bit of protective padding, some straps, a furniture dolly, and a two-wheel hand truck it was workable and doable with the labor pool at hand (me… basically).
As said, it came well packed and sitting on a slightly downsized wooden pallet. As I opened the box another box was found nested inside. The weight/gauge of the outside box was somewhat flimsier than I would have expected and could stand with some “beefing up” to stiffen up the outer shell. The inside box was of the same gauge as the outer and would have been appropriate with a sturdier outside wrapper. As it was, one corner was slightly crushed and bruised up a bit.
Upon opening the inside box, the subwoofer was revealed to be resting safely inside on form fitting, closed cell foam endcaps and straddled on the sides with more closed cell wrap-around foam spacers. This appeared to be a well-designed and secure protective support system for the speaker. The grille was removed and secured in its own cutouts, captured between the top and bottom foam endcaps.
While my review sample was not wrapped in protective foam or plastic, I would imagine that a new unit shipped to a customer would be.
I unpacked it in the garage, transferred it to a furniture dolly and moved it into the house strapped on a two-wheeler.
The Monolith M-215 is a monstrous, brutish, beast of a subwoofer. But despite that big and brutish appearance it has an industrial, functional kind of beauty that appealed to me. I was especially fond of the look without the full-length grille attached. With the two front-firing 15” woofers looking forward and the proudly tagged “MONOLITH” dust caps staring you in the face the speaker gives the distinct impression of being ready to rumble… and of being all business. With the grille on, it was only slightly less imposing. Displayed either way it was still very much “PA” cabinet-like in size and aesthetics. Likely, because of the imposing size, it will not gain much traction with those who are more “Décor Conscious” than I. In case of point, my wife immediately referred to it as “Ugly!”. Conversely, when she had a chance to sit and listen, she actually turned to me and stated, “I can hear the difference! It sounds good!” The amount of good, however, was sadly not enough to convince her we needed a subwoofer the stature of a mid-sized refrigerator in the living room.
This speaker can be used on its side for those that want to place it under a screen for example or hide it theater-like behind an under-the-screen speaker enclosure build-out.
Form, fit and finish were excellent. The cabinet is well put together and solid. A good rap with the knuckles produced only the slightest hint of ringing, even in this huge box. Construction is said to be five layers of HDF laminated together making for a very rigid and dense enclosure. When in operation the cabinet does vibrate at extremely high volumes, as one would expect, but it is surprisingly inert at all volume levels up to insane.
I took a peep inside the box by removing one of the speakers and saw a lot of sound damping material stapled about the interior with substantial bracing strategically placed. The front panel is about 1.5” of milled laminated HDF material.
The cabinet is wrapped in, what looks like, a vinyl faux Black Ash finish that looks good while keeping the price point realistic.
The cabinet is a ported front firing design with a slot-style port that extends across the bottom and folds into the interior of the cabinet and is sized to reduce/eliminate port noise and “breathing” turbulence. The speaker is designed so the port can be sealed if you prefer the slightly tighter, more controlled, sound of a sealed cabinet.
The 2000 watts RMS (3600 watts peak) Class D plate amp on the back of the speaker is approximately 9.5” wide and 22” high. From my little peep inside it is a pretty densely packed amp component-wise, extending about 3.5” into the cabinet interior. Built around a Texas Instruments™ 48-bit data path (with 28-bit filter coefficients) DSP engine, every aspect of the amplifier’s transfer function, power output limiting, and thermal protection is constantly monitored to the millisecond and is customized for each individual driver. There are twin RCA inputs and a single XLR balanced input with XLR out feedthrough. The controls on the amp, other than the mains power switch at the bottom, were three toggle switches; Auto On/Always On, Extended/THX (curve selection) and Crossover/THX (internal variable crossover disabled – fixed at 80Hz) and three knobs; Crossover (40Hz to 140Hz), Phase (0 degrees to -180 degrees) and Level (-20db to +15 with a single tactile detent at the THX Reference Level setting) All controls work as expected. There are no “High-Level” (Speaker Level) inputs. Only the line level RCA’s and the Balanced line-level XLR inputs are provided.
The custom designed 15” drivers are truly massive. Cones are made of long-fiber pulp and fiberglass to increase rigidness while keeping it light and responsive. The critical motor components feature a 60mm voice coil with high temperature aluminum wire and black anodized aluminum bobbin, FEA computer optimized design, 2 aluminum shorting rings, undercut T-pole focused field gap, and massive Ceramic Y35 magnets weighing in at 6.75 pounds on each speaker.
Advanced computer modeling was used in the design and prototyping of the critical woofer surround resulting in the unique formulation of the NBR (Nitrile-acrylonitrile-Butadiene Rubber copolymer) used.
These elements working together result in an up to 2.32” maximum available excursion.
There are six tiny rubber feet screwed into the bottom of the cabinet for support that seemed to be totally inadequate for the size and weight of the speaker. If you want to use the sub laid on its side, you will have to provide your own support method. I would suspect rubber isolation feet or a solid thick layer of damping material, or even a rubber mat, would work well enough for side placement or even to replace those tiny rubber feet when used in the vertical as well if desired.
Supplied accessories include the molded 14-gauge power cable, removable foam port plug, and a 117-page manual (first 26 pages are in English) that details the controls on the amp and gives setup and configuration advice along with a modicum of placement instructions. The instructions are repeated in French, German, Italian, and Spanish.
I set the subwoofer up in my living room which is a big open concept area connected to the kitchen and dining areas and on the order of 8000+ cubic feet of volume. Speakers are BG PD-6 in-walls for the left-center-right and 4 - BG P-8’s in-ceiling for the surrounds. The PD-6’s have 2 – 6” Kevlar conventional woofers and 1 – 3” Planar Ribbon Tweeter while the P-8’s have an 8” Kevlar woofer with a 3” coaxially mounted Planar Ribbon tweeter.
The only subwoofer normally used, for what was up to now, casual music listening and TV watching, was my tiny by comparison, Polk PS-10 10” subwoofer.
Using my Sony receiver, I did the preliminary level/distance measurements, and then manually tweaked the level, crossover point, and phase on the subwoofer by ear to my liking.
After all was said and done, I ended up with the crossover set at about 85Hz and phase hovering just South of 0 degrees (at about -3 degrees) with the level set to my liking.
If you are looking for a “set it and forget it” scenario I suggest going with the THX settings preset on the sub that sets the crossover at the THX standard 80Hz and bypassing the subs crossover controls altogether. Let Audyssey, ARC, DIRAC, or room correction scheme of your choice, handle the level, phase and other setup parameters and go from that starting point. I did some phase testing with REW to do my final tweak before listening tests were performed. I also switched to the “THX” settings a few times when listening just to see if that improved anything. The THX settings made minimal change to the sound and sounded no better, so I went back to my settings leaving them as they were.
A Note About THX Certification
Monoprice makes a big deal about the THX Ultra Certification of this subwoofer. Personally, I worry less about that than some, and think that measured performance and proven reliability are more important than third party endorsements and certifications in the long run. However, it behooves me to lay a few paragraphs down about just what THX Certification means when seen stamped on whatever product you are considering for purchase, and specifically what it means for this particular product.
As most of you are aware THX is a set of DESIGN and PERFORMANCE parameters that must be both designed into a product, and then proven to exist in a product by THX Lab testing to gain certification. A designer/manufacturer must start this expensive process by purchasing the design goals and any required circuit design from THX for whatever product they are building. Once designed, a functioning final assembly/prototype/sample must be submitted, and PAID for, by the manufacturer to THX for testing to ensure the product meets all of those set design requirements and goals. Once it is proven to meet the goals set by THX, certification is granted. The manufacturer continues to pay a small royalty/licensing fee for each unit sold with the THX certification mark until that product is no longer manufactured.
This entire process is rather expensive for the manufacturer but gives us, the consumer, several real benefits. The biggest, from my viewpoint is we are purchasing a product that has been designed to certain performance standards, and has been proven to meet, or exceed, those specific design goals and specifications. Is this an automatic guarantee that the product will meet your expectations, goals and quality requirements? NO! But it is an established benchmark that can be pointed to by the manufacturer and an assurance to the consumer that defined standards have been met. For anyone with a specific budget and goals, but with limited experience in putting things together, this can be a very good starting place when building a system.
The metrics that are tested by THX for Speakers and Subwoofers are:
Axial Frequency Response Analysis
Low Frequency Cut Off
Stray Magnetic Flux
Maximum Output Level
Acoustic Noise Level
It’s easy enough for the consumer to find out what metrics THX is testing… But not so easy for anyone who has not purchased the THX Certification package to find out what the pass/fail limits of those tests are. It’s generally considered a secret to be shared between THX and the manufacturer.
Keeping in mind that, for the consumer, THX is primarily a home theater set of design and performance goals. THX has been stretching into other consumer areas such as computer speakers and portable sound as well.
On the other fronts along the THX continuum, an entirely different set of metrics and specifications exist for professional studios and theaters/presentation venues.
As mentioned, the M-215 Subwoofer is THX ULTRA Certified. In a nutshell this meets the THX design and performance goals of a speaker or subwoofer at THX defined levels in an up to a 3000 cubic foot environment. A THX SELECT certification would mean the speaker would be certified to meet a different, more relaxed, set of goals in a less than 2000 cubic foot environment.
Say you have a bigger room than 3000 cubic feet Bucky? Simply buy more speakers/subwoofers and power up :-)
Our contact at Monoprice told me through e-mail communication that in addition to being designed with THX certification in mind, their primary design considerations with all speakers is stated as: “Our main philosophy is to make speakers that have exceptional dynamics, are really "fast" with transients, can play at high SPLs with low distortion, and deliver an incredible value for the money.”
Below is a chart supplied by Monoprice displaying the manufacturers Frequency Response vs. SPL with the various port configurations along with the “Extended” vs “THX” curve switch setting. Clearly the deepest and strongest bass response is in the open port configuration with the mode switch set to “Extended”. I did some testing, port plugged and port open, to ascertain what was the best overall configuration for music and/or movies in my room. Check out the comments on both configurations in the Listening portion of the review below.
I did some REW Frequency vs. SPL measurements in my room to see what my room was doing to the frequency response.
Frequency vs SPL at my listening position – M-215 VENTED
Frequency Response/SPL with the M-215 VENTED vs PD-6 right and left speakers only (NO SUB) at the LP
M-215 SEALED - Measured at Listening Position
It can be seen from the graph above that inserting the plug immediately restricts the lowest frequencies of the sub, and that does cause some audible changes depending on what material you are listening to.
For the musical portion of the test I started out with my standard goto’s, listening to selections from Simply Red, Spock’s Beard, Thomas Dolby, Tower of Power, and of course Steely Dan. I also listened a good mix of several artists, over several sessions, on both Amazon Music HD and Pandora Premium that included this time, for whatever reason, a lot of Michael McDonald and Keiko Matsui.
All listening was done in both cabinet configurations starting with the VENTED (open) configuration and then repeating with the cabinet in the SEALED (closed) configuration.
Movies and Video
For movies I went with selected chapters from John Wick 3, GI Joe, and The Dark Knight Rises. I also watched some Netflix and Disney+ stuff that included the likes of The Mandalorian among other material.
All listening was done in both cabinet configurations starting in the VENTED (open) configuration and then repeating with the cabinet in the SEALED (closed) configuration.
Simply Red – “Sad Old Red”
VENTED – The sweetly presented “Walking Bass” throughout this song was well defined, deep and tonal in the lower bass registers and highlighted the M-215’s ability to work well with the main speakers in a seamless crossover. Very musical and pleasant presentation.
SEALED – A tighter more “refined” and “defined” sound.
Spock’s Beard – Twenty Years of Spock’s Beard – “The Light”
VENTED – This recording has some incredible lows in both the bass and synth lines that pop in and out of the tune. The M-215 did a more than solid job of presenting this aspect in a musical way. Some of the more rapidly changing staccato passages became somewhat less defined and more “run together” with, what felt like, a bit of bass overhang.
SEALED – Tighter, more impactful sound on the bass but lost a little “something” with the synth in the very bottom. The lowest string on a 4-string bass is 41.2Hz but there is no such restriction on a synth. Because of the roll off when the M-215 was sealed the bass guitar was naturally emphasized a bit more and the deeper digging synth was muted slightly.
Thomas Dolby – Aliens Ate My Buick
VENTED - Playing my favorite track from this 1988 album “Airhead” was a fun experience thru the M-215. The late, great Terry Jackson laid down a funky bass line that many subs just give up on. Combined at times with a synth the bass in this tune digs deep. The M-215 reproduced the song with aplomb only slightly blurring the bouncy and funky low bass. The result while not a clear, distinct rendition of the track, was a decidedly fun and musical version, nonetheless.
SEALED – Bass was much more “controlled” and as a result the kick drum more connected than with the open port. The synth lines did not suffer as on the previous tune. Actually, an overall better sound.
Tower of Power – “What is Hip?”
VENTED - I chose this tune because of the funky yet driving bass line. The Monolith M-215 kept the driving bass forward in the mix and still well connected with the bass drum. The M-215 conveyed a good sense of musicality and excitement in this older 1973 recording.
SEALED – Probably because of the age of the recording and the lack of synthesizers this recording sounded great in either port configuration. I did lean slightly more toward the sound plugged….
Steely Dan – Two Against Nature – “Gaslight Annie” – Steely Dan
VENTED – Steely Dan always delivers stellar studio albums. One of the most connective elements across all of their albums is a wonderful Bass/Bass Drum sound. This Grammy winning (Best Recording) album is no exception. The M-215 delivered in spades with a well-defined, articulate, and connected Bass Guitar/Bass Drum sound. Musical, powerful and impactful the subwoofer delivered with only the slightest sense of looseness present in the low end.
SEALED – A fantastic recording that presented well in either configuration. But again, I leaned toward the sound of the sealed box after repeated listens.
I listened to many other selections from several other artists, from Michael McDonald to Keiko Matsui using Amazon Music HD and Pandora Premium always with good, listenable results. If the source material was good the bass representation through the Monolith by Monoprice M-215 was always hard hitting, impactful and musical when the material called for it.
I played selected scenes from three movies that represent, to me, some of the best of big, noisy action movies and the real reason to watch such movies… the SOUND! I listened to all three selections in the VENTED(open) configuration and then repeated the listening in the SEALED (closed) configuration.
I’ll just say it right up front… The best way to watch movies is in the PORTED/VENTED/LET THAT BABY BREATHE! configuration. The open port configuration dug way down there into the infra-sonics territory and in every case added a special something to any scene that featured a low frequency SfX. Explosions were bigger, gunshots more percussive, low-drones will put you on edge, thuds were, well, more….”thud-dier”.
With the PORT CLOSED (SEALED) that effect was reduced, or even lost! That in your chest compressive/percussive effect…. That FELT in your gut effect, the physicality of it, was just not there and a certain level of excitement went missing with it.
So, the blurbs below reflect my observations with the speaker in the VENTED configuration and the above reflects my universal thoughts about the configuration to use for movies.
John Wick Chapter 3 – “The Weapons Museum” – While not containing the biggest explosions and not the loudest/noisiest scene in the third part of the John Wick saga, this scene certainly contains plenty of wildly violent and visceral action cues and moments. Each gunshot, each knife strike, each punch, each body fall was rendered with authority and impact by the M-215 subwoofer.
GI Joe – Rise of the Cobra – I keep going back to this one scene in the first GI Joe movie as my HT demo scene… Chapter 2 “The Battle in the Forest”. There is so much low end from beginning to end with the continuous explosions, gunfire and even the occasional musical highlights making it a great high-volume demo for home theater. All of the action was rendered in a dynamic style when using the M-215 and strongly delivered into the large volume of the living room space. The fifty-caliber action from the gunner’s perspective was delivered crisply with the impact and the percussive notes distinctly felt with each round fired. The lower gut punch of the explosions was well rendered and presented with impact but never felt strained. I played this so loud my wife cried for mercy, but I couldn’t really hear her so….
Batman – The Dark Knight Rises – I played the scene “Bain Takes a Plane Ride” through a couple of times. Once at a reasonable volume, and once at insane (even for me) volume levels. With all of the low frequencies floating around in this scene, along with everything else happening sound wise, it’s easy for some systems to get congested and a bit overwhelmed at any volume level. The M-215 handled anything thrown at it with ease and without any overt signs of stress or strain. In fact, whether at lower volumes or the highest volumes it contributed to the overall sound in a meaningful and pleasing way on the low end.
I watched some other material including a couple of episodes of the Mandalorian on Disney+ and loved the full rich bottom end that the big Monolith sub contributed quickly highlighting where my little Polk subwoofer fell short of delivering in the big room.
A bit of Netflix and normal cable fare completed my video sessions. The M-215 always delivered full range low end effects and sound, when the material contained such a thing, while supplying just that mild hint of fullness that a good sub will supply on material that is naturally bass shy.
Summary and Closing Thoughts
The cubic volume of my main living area is a much larger space than what THX certifies this subwoofer to be used in. But, at no time was there any hint of strain, even during the most demanding of movie passages. It just calmly delivered deep digging and punishing bass when called for with all the material I threw at it, and at any volume that I asked of it.
Because I was crossing over at around 85Hz there was never a sense of being able to localize the subwoofer. What was presented by the Monolith by Monoprice M-215 subwoofer was the desired effect of room filling and felt bass at all listening positions.
With some musical selections there was a mild sense that it was almost too much of a good thing and it had to be dialed back a hair. Some music played at high volumes seemed just a tad loose as if there was some bass overhang/trailing present in the “VENTED” (open) configuration. Even in that open configuration, the sub was still very musical with all material I fed it, and was never overpowering, boom-y or boxy sounding after being dialed in.
Plugging the port brought a more satisfying “tightness” to the sound of music but did tend dampen the Ultra-LFE sounds of movies. If you listen to a lot of music, then possibly the SEALED configuration is right for you. Leave that port open if it is all movies in your life and let the M-215 shake your world. Either configuration is eminently satisfying with both music and movies and it is going to boil down to a matter of personal preference and taste.
As in all home theaters, multiple subwoofers working in concert have been proven to deliver stronger and more coherent bass to a wider spread of seats. Two (or more :-) M-215’s strategically placed, might be just the ticket to smooth any errant room nodes and deliver enough bass to satisfy even the most ardent Basshead*.
All in all, I liked this subwoofer a lot. From a performance aspect it delivered as promised. This is a subwoofer that really shines in a home theater environment. Put an action/adventure movie on and it will more than deliver the goods!
And, while it is a good sub to be used with music presentation, I did end up missing some of the tightness, definition, agility and musicality that other subs can and do deliver when it was in the VENTED (open) configuration. It does tighten up in the “Port Plugged” (SEALED) configuration but there are several other “Audiophile” capable subs out there at more reasonable and like prices that can also do a very respectable job on movie night.
But, “Sure as I’m sittin’ here…”, I’m just as sure that some people will thoroughly enjoy the slightly looser musical presentation this sub delivers with many types of music when the sub is in the VENTED configuration.
Now having said all that, this is such a powerful speaker that it could easily be set-up to overpower almost any system it is paired with, and caution should be used in that respect. As with all speakers (and, as with people sometimes :-) you need to live with it for a while forming a reasonable partnership before moving it in… or giving it up.
The Monolith by Monoprice M-215 Subwoofer ticks so many of the boxes of what a great subwoofer can and should do, especially for Home Theater. And… it does it at a much lower price point than much of the competition that operates anywhere near the M-215’s level of performance. The M-215 deserves to be given serious consideration when putting together a high-end home theater if you have the space, budget (and of course approval) for one… or MORE!
*Basshead (from the Urban Dictionary)
A Basshead refers to someone who enjoys heavy basslines regardless of what genre of music. Musical taste of a Basshead can range
from Rap to country with modified basslines. Some defining ways of recognizing bassheads is heavy subwoofer installations in their vehicles
as well as having headphones which have been designed for the drivers to produce the most bass possible.
Monolith by Monoprice M-215 Dual 15” Subwoofer – Published Specifications
- THX Ultra Certified
- Woofer: 2 x 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 Butadiene 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: Slot vented HDF cabinet with horizontal and vertical bracing
- Finish: Black Ash
- Amplifier: 2000 watts (RMS) - 3600 watts (peak)
- Frequency Response: 14-200Hz (Extended) 16Hz-200Hz (THX®)
- Harmonic Distortion: <3% 20-100Hz (94dB @ 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: 42.3" x 20.0" x 27.6" (1075 x 508 x 700 mm)
- Weight: 216 lbs. (98 kg)
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