Monoprice Monolith 12" and 15" THX Ultra Subwoofers Review Page 2

Connections on the back panel include stereo line level inputs, an XLR balanced input, an XLR passthrough, and an IEC power cord socket. There are six controls on the amplifier: three knobs for Crossover, Phase, and Level and three toggle switches for Crossover (On/Off THX), EQ (Extended/THX), and Power (Auto/Always On). Unfortunately, Monoprice doesn’t provide a PEQ (parametric equalizer) or control via a smartphone app, as can be found on some subs from competitors. I consider a PEQ and app control as nice-to-haves, not have-to-haves. As I stated earlier, the Monolith subwoofers check all the right boxes. But how do they sound? Spoiler alert: awesome!

Not for Girly Men
Unboxing either subwoofer is a two-person job: The 12” weighs just under 100 pounds (98.5, to be exact), and the 15” weighs 128.5 pounds. Then there’s the added weight of the double-boxed shipping container. There are no instructions for unpacking the beast, but it’s best to open the top of the outer box, slowly flip the whole thing over, and lift the outer box off the inner one. Repeat the process to remove the sub from the inner enclosure; your back will thank you. Each sub has spiked rubber feet, so it’s best to use some sliding furniture movers (available at your local hardware store) to position it. Monoprice includes a pair of white gloves in case you want to provide your own white-glove service and keep oily fingerprints off the satinfinish, black ash vinyl.


Given their size, neither of the subs would fit in the preferred front left corner of my room, due to a fireplace hearth and my wall-mounted front left speaker. (I usually put the small-footprint, cylindrical SVS Ultra there.) So I placed each of the Monoliths in Position No. 2, which is along the right side of my room, about a third of the way—where I usually keep my reference Hsu Research sub.

I set up two user profiles—one for the 12” and the other for the 15”—in my Anthem AVM 60 pre/pro and calibrated the speaker output levels using an SPL meter and test tones from a THX calibration disc. As mentioned, you can choose to use either sub sealed by installing the provided port plugs. This will give you the tightest bass, at the expense of some low-frequency extension. Or, given the multi-port design, you can close one of the two ports on the 12” or two of the three ports on the 15”; by doing so, you’ll get the greatest extension at the expense of reducing maximum output. I listened to both subs in this extended mode, as well as with all ports open. For music, I really liked all ports open, but for movies, I preferred the extended mode.

My go-to audio tracks to test subwoofers include Justin Bieber’s “Baby,” Regina Spektor’s “Fidelity,” and Joss Stone’s “Sleep Like a Child.” I moved back and forth between the 12” and the 15” with each of these songs multiple times, and I was surprised at how well the 12” was able to hang with its larger sibling. In a lot of cases, the 12” was a tad tauter, but I’m really splitting hairs between the two subs when it comes to music: Both sound fantastic.

On some bass-intensive rap tracks, such as N.W.A.’s “Dope Man,” the 15” definitely showed that it could dig a little deeper and play louder than the 12”, which foretold what I would hear later with movie soundtracks. Of course, that shouldn’t be a surprise given the 15” sub’s larger enclosure, woofer, and amplifier.


The Ultra HD Blu-ray of Pacific Rim is one of my favorite discs in the new format. Not only does it boast fabulous-looking HDR, but the Dolby Atmos mix is a stellar example of the breed with its ample use of overhead effects and its deep, sub-20-Hz bass content. In the movie, after the Jaeger battles the Kaiju off the coast of Alaska, the Jaeger makes its way to shore while a grandfather and his grandson search for treasure with a metal detector. With the 15”, I could literally feel the approaching giant before I saw him come through the fog thanks to its reproduction of the accompanying low-bass information. The same scene on the 12” didn’t have quite the same visceral impact. Granted, my room approaches 5,000 cubic feet, so it really puts the 12” in a situation beyond its intended application. In most every case, I was able to hear—and feel—either subwoofer deliver movie sound that had ample bass above 20 Hz, such as the dive-bomb scene on the beach in the first part of Dunkirk or the battle in “Blackwater” (season 2, episode 9) from Game of Thrones. Each sub was able to cleanly reproduce articulate bass with good extension down low and plenty of output, although I always got more oomph with the larger sub.

To be fair to the 12” and gauge its performance in a more suitable space, I spent some time with it in my secondary system that’s housed a 1,100-cubic-foot room. In that room it performed marvelously with movies. So this certainly is a case of choosing the proper subwoofer, or quantity of subwoofers, for the environment. I’m sure that dual 12” Monoliths would have performed flawlessly in my larger theater.

Double the Fun
Monoprice has definitely impressed me with their initial offering of THX-certified subwoofers. Each warrants a Top Pick—but if you can swing the extra cash for the 15” model, it would be my preference, especially if you have a large room. One thing worth repeating: In order to receive THX certification, these subs need to meet a low distortion number, which really translates to clean and controlled bass response. I truly enjoyed my time with both of these subs and wouldn’t hesitate to recommend them to a friend, but I would add to this my usual adage: Two is better than one, because, well...there’s never such a thing as too much bass!

drny's picture

Daniel I'm sure the Monoprice subs are quite good.
But what I really NEEEED to know is how did you persuade your wife (if your married that is) on the four reference Subs you already own.
I have a Deftech STS Home Theater speaker system with an additional 10"Deftech supercube sub.
My speaker selection was highly influence by their aesthetics as my wife nixed much larger Home theater speaker systems that I preffer(ugly, says my beloved).
I have attempted to add the same HSU Research and SVS model subs you owned, but no dice.
You will be my eternal God if you so kindly share your enchanting the wife skills.
Mine stink. Adding a ceiling projector and retractable screen cost me a complete kitchen remodel.
If you are single (co-habitating does not count, as they can't leave you broke on the gutter) disregard my request.

David Vaughn's picture
Patience is a virtue :) It took me years of convincing, but it helps that I earn income from this writing gig and I pulled it off as "it's something I HAVE to do!" By the way, you made me LOL with the kitchen remodel because that's how I got a front projector in 2005!
jalan's picture

For $300 more wouldn't a setup of dual Monolith 12's be far superior to the single Monolith 15? Both seem like well made and fantastic subwoofers but The 15 at $1000 or $1100 would be a more logical price point.

David Vaughn's picture
Yes, dual 12" subs would be the preferred setup if you can't swing the cost on the 15" subs. While you'll give a little up in deep bass extension, that's something you feel rather than hear anyway. If I were on a budget, that would be the direction I'd go.
hk2000's picture

I have a 10" Velodyne that goes down to 19Hz, like the Monolith 12, and I do feel the bass, the floor shaking under my feet from 10 feet away, so why would the Monolith not be able to do that.

David Vaughn's picture
It can, but the Monolith 15 goes deeper than the 12.
hk2000's picture

Those subs are way too heavy, how are you supposed to experiment with location? That'd be a killer chore.
Also, why use 4 different Subwoofers? Most reviewers always advocate same make and model, and you turn around and mix and match from 3 different manufacturers? And one more thing, who listens at home at THX levels? unless you have no neighbors, of course.

David Vaughn's picture
I used furniture sliders to move them around. As for multiple subs, you can mix an match, but it makes integrating them harder. That's why I use a Mini-DSP, which allows me to integrate the 4 subs as one. This takes a lot of time to do right, which most people aren't willing to do, which is why using the same sub manufacturer the "easier" choice.
David Vaughn's picture
As for THX levels, I don't listen that loud unless I'm testing products to ensure they sound proper at those levels (generally, it's much too loud for me). The loudest I personally like to go is -10 from reference, which is plenty loud.
hk2000's picture

So, if I'm more interested in extension- especially at lower volume than I'm in maximum loudness, wouldn't it make more sense to go for a sub that may be limited in headroom , but accurate to below 20hz?
I'm currently using 2 subs in my theater room that can dig down to below 20hz (at reasonable loudness)and still give me enough visceral impact that I more feel than hear, and yet, even put together, they weigh less than either of these monoliths here.
Frankly, I feel Monolith is trying to be the American muscle car in the lot of exotic imports, offers a lot of value /performance, but leaves something to be desired. But I'm sure they'll generate a lot of interest for the value they offer.

David Vaughn's picture
They weigh so much because of using HDF, which is much heavier than MDF or plywood. I'm not sure what benefit, if any, the HDF offers, but definitely does add to the weight of the subs. The good news is once they are placed in the proper spot (or spots), you never need to move them again until the next upgrade comes along :)
kevon27's picture

Please have Monoprice send you the 10 inch sub for review. That sub will most likely be the preferred choice for people with apartments and small rooms.

David Vaughn's picture
Check over at AVS and you'll see some people that have bought it and like it. Given the performance of the 12" and 15", I'd almost blind buy it if you have space or noise constraints.
DoughMucker's picture

I've had a Mirage Omni S8 for several years and though it has nice sound, it doesn't have enough oomph for my medium sized basement theater. So, after reading this review, I think it's time I pull the trigger on a couple of these. My room is about 2700 cubic feet (11.5'x31'x7.5'). From what I've read, the 10" version would be too small, but would two be enough to pressurize the room? Or do I really need to step up to the 12" subwoofers?

David Vaughn's picture
The 12" will go deeper, especially two of them.
DoughMucker's picture

Thanks. I had already went ahead and bought two of them. :) Arriving in a few days.

David Vaughn's picture
That's great to hear. Be sure to post any thoughts you have on them.
Adam Wade's picture

I have a 5000 cubic foot apartment/living room. I want a sub mainly for movies -- for that deep bass impact.

Until now I was targeting the subs from HSU, SVS, and Rythmik for this price point. Not sure where these Monoprice fit into that segment.

David Vaughn's picture
These fit into that segment, although if size isn't an issue, the HSU VTF-MK2 at $859 is a much better value. I use one of these as my reference subs and it does an outstanding job.
jpgin's picture

What happened to the Marantz 8802a?

mmamun7's picture

Total home is approximate 2,000 sqft. Will setup in loft (upper floor), 20ft by 17ft. One side of loft is open to lower floor living, kitchen dining. I am confused among SVS PB or SB 2000 (500 RMS)/ Monolith 12"(500 RMS)/ HSU VTF-2 MK5 (350 RMS) subwoofer. Which subwoofer should I get?
Movies 65%, Music 35%

Have Martin Logan Motion 40s as main speaker.
Any help?

Film235's picture

Hi Dave, I’m building an M&K atmos system at home (S150s & SS150s) and I’d like to upgrade my sub from a VX-760. Is a MX-350 the way to go or is the Monolith 12 a better option? I believe you’re an old M&K guy like me, so I thought I’d ask your advice. Love your work, thanks!