Monoprice Monolith THX Ultra Speakers 5.1.4 System Review: Extreme Performance and Value

Published On: December 25, 2021
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Monoprice Monolith THX Ultra Speakers 5.1.4 System Review: Extreme Performance and Value

The best-kept secret in home theater sound is the Monoprice Monolith THX-certified speaker line.

Monoprice Monolith THX Ultra Speakers 5.1.4 System Review: Extreme Performance and Value

By Author: Sean Killebrew

Sean Killebrew began his writing career in the '90s, covering football for UCLA (his alma mater). His first foray into publishing was in 2000, with the below-the-line film- and TV-production guide books LA 411 and NY 411. For the past decade, Sean's passion for audio/video has been poured into writing for When not chasing A/V deals, Sean spends time skiing and losing to his son in basketball.

Monoprice, if you’re familiar with the name, it’s likely not due to their speaker line, but rather their aggressively priced and well-regarded A/V accessory line. They’ve been steadily adding to their product offering since their inception in 2002, and now offer everything from tube amps, to 3D printers. I’ve been one of their customers for 11+ years, beginning with the purchase of a 100’ component cable and most recently with a binding post wall plate for my outdoor speakers; not riveting intel, but gives you a sense of the diversity of their product line.

More recently, they’ve turned their attention to home theater speakers and, rather than limp in, they’ve attacked this segment of home theater. The subject of this review is essentially a 5.1.4 Atmos capable rig (the .4 coming from Atmos drivers in the towers and surrounds) from their Monolith line: the THX-465T towers, THX-365C center channel, THX-265B surrounds and 15” THX Ultra Certified 1000-Watt Monolith subwoofer (model 24458).

Monolith THX Certified Speakers

As you can imagine, given the nomenclature, all of these speakers, and the entire Monolith line, are THX Ultra Certified. In a nutshell, THX Certification helps ensure accuracy, wide dispersion (for those sitting in the cheap seats), and the ability to play at high volume without distortion. The 465T towers retail for $999 each (currently on sale for $799) and feature four 6.5” woofers, a 2” cloth dome midrange driver, and a 1” silk dome tweeter. The Atmos driver on the top of the speaker features a 5.25” pulp cone woofer and a .6” silk dome tweeter. They’re also quite large, measuring 55.3” high by 13.1” wide by 16.7” deep and they weigh a stout 55 pounds each. Frequency response measures 29 Hz – 24 kHz vented and 45 Hz – 24 kHz when sealed and sensitivity is rated at 89.5dB. It’s also worth noting that the cabinets in the Monolith line are all HDF (High-Density Fiberboard), not MDF, worth mentioning as this provides markedly better damping and is a welcome touch, especially at these price points.

The THX-365C center channel retails for $399 (currently on sale for $349) and features two 6.5” pulp cone woofers, a 2” silk dome midrange driver, and a 1” silk dome tweeter. The 365C measures 9.7” high by 22.9” wide by 10.8” deep and weighs in at 26.4 pounds. Frequency response is 65 Hz – 24 kHz and sensitivity is rated at 89.5dB.

The THX-265B Atmos-enabled surrounds retail for $349 (currently on sale for $269) and feature one 6.5” pulp cone woofer and a 1” silk dome tweeter, while the up-firing Atmos speaker features a 5.25” pulp cone driver and a .6” silk dome tweeter. Frequency response is 65 Hz – 24 kHz and sensitivity is rated at 86.0dB. The 265B’s measure 15.4” high by 9.7” inches wide by 10.8” deep and they weigh 21.4 pounds each.

Lastly, the Monolith 15” 1,000 Watt sub, which is an extreme example of their exemplary price to performance ratio (more on that later).

Hang on to your hats as you read these specs, both those of form, as well as function. The sub retails for a very reasonable (given its performance) $1,339 (currently on sale for $1,099) and features a 15” driver and 1,000-Watt Class D amp. The cone is made of a combination of fiber pulp and fiberglass, said to provide greater accuracy, output, and dynamics. It’s also been designed with 3 ports, allowing you the flexibility to run it sealed or unsealed. Frequency response is dependent on whether you run it sealed: 15-200Hz, vented (2 ports): 14-200Hz, or vented (3 ports): 16-200Hz.

Generally speaking, a sealed sub is going to provide tighter, more accurate bass while a ported sub will be louder and give you more boom, but you’ll lose some accuracy. It couldn’t be a more subjective situation, hence Monoprice provides you the option. I prefer a sealed box and kept the sub as such throughout critical listening. As with all other Monolith speakers, the cabinet is made of HDF and Monoprice paid particular attention to the internal bracing of the cabinet in order to ensure proper damping.

In past subwoofer reviews, I’ve used the term “beast” to describe them; those reviews need to be edited to reflect what now lurks in my theater – a true beast, both in terms of girth, as well as performance. To put it in perspective, my 12-year-old son was too small to help maneuver it and my wife was simply too scared. So, in a true Festivus Feat of Strength, I wrestled all 128.5 pounds of it downstairs and into position in my theater without help. There would be no experimenting with positioning. Luckily, it did fit, albeit barely, into the subwoofer sweet spot in my theater.


I began by connecting the speakers to my Marantz SR7013 receiver, using Solstice 8 speaker cables from Wireworld. Assorted source components include my Macbook Pro, Arcam irDAC, and LG Ultra HD Blu-ray player. The only real wrinkle with connecting a system of this ilk is the fact that, given the upward-firing Atmos drivers in the front towers and surrounds, a 5.1.4 system. As such, each of those speakers needs an extra set of speaker wires. In some systems, this is pretty straightforward, in my system, due to the fact that all of my source components are in another room; it was kind of a bitch. That said, regardless of your particular setup, there’s a solid chance it’s going to be easier than cutting holes in your ceiling and routing cables to them.

The only other wrinkle I’ll mention is the fact that the tower cabinets don’t ship enclosed, rather the base acts as the final piece of the speaker cabinet enclosure. So it’s a bit disconcerting to unbox one of these beasts, lay it on its side and realize that there’s an open hole on the bottom of the cabinet. That said, once the base is installed, they seal quite nicely and, not to tip my hand, perform admirably. This is likely a cost-saving measure and one for which I have no complaint, just thought it worth mentioning. After plenty of hours of the break-in and running my receiver’s auto-calibration, it was time to begin critical listening with several Atmos encoded Blu-rays and some Spatial Audio, courtesy of Apple Music.


Out of the gate, I wanted to get a sense of how the upward-firing Atmos drivers would compare to my dedicated in-ceiling Atmos setup. I’ll admit, having only heard demos (almost always in highly controlled environments), I was skeptical about how they might perform and, honestly, had never truly considered such a setup for my theater.

So, with plenty of preconceived notions, for which I’m not proud, I fired up my trusty Dolby Atmos demo disc, given to me at CES several years ago. I started with this Blu-ray as there are several well-recorded Atmos clips with which I’m very familiar. I’ll say without hyperbole, I was truly stunned. Are there differences in the sound of a dedicated down-firing Atmos ceiling speaker vs one that’s firing up and off the ceiling? Of course. Would it bother an untrained ear with the right setup? I doubt it. Case in point – during casual listening sessions, neither my wife nor my 12-year-old son noticed any difference in terms of sound quality, immersion, etc.

Did it make me second-guess my decision to tear up my ceiling, tear out some of my hair and spend a shit ton of money on my existing in-ceiling setup? Yes. In other words, if you’re on the fence about in-ceiling vs. upward-firing Atmos speakers, I can say that unless you’re truly discerning about sound quality and want only the most immersive setup, you should strongly consider both propositions.

After ejecting the demo disc, it was on to John Wick 3 – Parabellum (Lionsgate). In the beginning of chapter 8, during the gunfight with Keanu and Halle Berry, I noted the Monoliths brought forth most of the realism and intensity that I’m used to from my reference system, while also keeping their composure through the cacophony. There are plenty of bullet impacts and stabbings in this scene and this is where the sub shone brightly.

As a matter of fact, I’d say at least in terms of watching an action film, it’s as solid a performer as I’ve had in my listening room. With music, wherein you might want more accuracy, speed, subtlety, etc. you can do better, but you’re also going to spend a lot more than a grand to get there. But back to the film, I did note that while still compelling, the upward firing Atmos speakers tend to put off a bit more of a manufactured sound than what you get with dedicated in-ceiling Atmos speakers, which is to be expected. That said, the Monoliths still provided a compelling sense of realism and, especially with the sub, made me miss the movie theater a tad less.

John wick 3|dog fight scene|2019|

Next up in the cue was the Diamond Luxe Edition of Gravity, the only Blu-ray release of the film that has an Atmos encoded soundtrack. So rare is this disc that it’s going for $300 on eBay, which is more than I’ll make for writing this article, but I digress. In the opening scene, as NASA communicates with the astronauts, the dialogue comes from all around you, a true showcase for Atmos and one that will expose a lesser Atmos rig. In this case, you’d never know that the Monolith Atmos drivers were firing up and off the ceiling, as opposed to hanging up in the air. Also, in this and with other films, I noted how articulate and transparent the center channel is with dialogue.

As a reminder, we’re talking about a center channel that costs $349; transparency is not a term typically associated with sub-$400 centers. The surrounds also shone brightly during this sequence of the film, drawing you right into the action with both the effects, as well as the dialogue, and managing to create and hold all of the tension the filmmakers intended. I kept marveling at the fact that this level of performance can be had for $3,600. While not a bargain for many, myself included, at this level of performance it’s a downright steal.

Gravity 2013 Opening Scene

Moving on to music, I played Pink Floyd’s Learning to Fly in Dolby Atmos through Apple Music’s new Spatial Audio offering. It was an interesting mix, with the vocals moving back and forth across the front of the soundstage. While the Monoliths did a commendable job in providing solid detail and imaging, Spatial Audio, in general, turned out to be a bit of a mixed bag. It’s highly track-dependent, wherein some mixes are compelling and others sound gimmicky and are off-putting. That said, it’s certainly worth your time if you have an Atmos capable rig and like to experiment.

As I continued with music, I played around with some familiar bass-heavy tracks to see who’d give up first, the Monolith or me. I lost. Playing Sunflower by Post Malone, I noted that the sub hit the heavy bass notes with taut, accurate bass and never lost its composure. I had a similar experience with tracks like Supersonic (My Existence) by Skrillex and The Beastie Boys Multilateral Nuclear Disarmament, which while hitting hard, is also a good measure of a system’s overall coherence and dynamic range. It was on this track, much like with the Gravity demo, where I truly fell in love with the Monoliths.

They image well, provide a compelling soundstage (on most tracks), and are just plain fun. The sub also provided me with an answer to a question audiophiles have been asking themselves for many moons – is there such a thing as too much sub? The answer is no. Going up in power, driver size, etc. is commensurate with the level of enjoyment and is one of the most compelling ways to re-create the movie theater environment.

For my last music test, I had to throw in a Blu-ray concert and, after much deliberation, went with my favorite female artist of all time – Stevie Nicks. Her Blu-ray The 24 Karat Gold Tour (BMG) in DTS-HD Master Audio is a true testament to the fact that, at least as of 2015, she’s still got it. It was during this demo that I noted the midrange prowess of the Monoliths, especially in terms of resolution. I also noted that both vocals and guitars tended to sit toward the rear of the soundstage while backing vocals tended to fill the entirety of the soundstage, though possibly due to the recording, rather than the speakers.

Any rig has its limitations and it was while listening to this concert that I came back down to earth and noted the lack of transparency and resolution compared to my reference rig, albeit at more than twice the price. All that said, we can’t talk Stevie without talking vocals and I noted that the Monoliths did a solid job conveying her signature rasp, range, and vibrato, especially on familiar tracks such as Landslide and Rhiannon. I also noted exemplary imaging, with the guitar hovering up and to my left and the piano floating all around the listening position.

Stevie Nicks - Rhiannon Live ( 24 Karat Gold Tour ) 60FPS

The Downside

While the subwoofer comes with a decent set of “getting you started” instructions, nothing beyond a card directing you to the Monoprice website exists in the other speaker boxes. This might seem like a minor oversight, but when you consider the fact that these are Dolby Atmos capable speakers, it’s not necessarily going to be obvious to a noob how to properly connect them to a receiver. Further, once you follow the link mentioned on the card, Monoprice makes no mention of how to connect them to your receiver.

While these are purpose-built speakers, it’s worth noting that they are, at least with respect to the towers and sub, exceedingly large. While this is not a negative per se, it’s simply a reminder to do your homework on your theater’s size and what level of performance you’re looking for before ordering.

All of that said, sonically speaking, which is obviously the most critical component with a set of speakers; I found no critical fault with the Monoliths, at least none that would stop me from buying them.

Competition and Comparison

In the interest of trying to keep this as fair as possible, let’s consider this particular system’s total current sale price of $3,584 since that’s today’s pricing. Typically, when writing this section in a review, I have a couple of comps that pop right into my head. In this case, I’m somewhat loath to admit, I had to resort to research. Though to my credit, many of the major speaker manufacturers are limping into the Atmos realm as they’ve been waiting to see if this new technology is here to stay. 3D anyone?

Given the proliferation of films being released in Atmos, coupled with Apple embracing the technology, it’s now a pretty strong bet that it’s here to stay. Anyway, there simply isn’t anything out there, at least that I’m aware of, that delivers this much bang for the buck; they’re sort of the Bayliner of the speaker realm. Anyway, after some digging, I did come up with a couple of options – one dedicated rig, with the Atmos drivers built-in, and the other using Atmos add-ons. Anyway, without further preamble, here are a couple of other options worth a look at. I’ll start with Klipsch, as it’s one of the rare brands in which quality and consistency run from their least expensive offerings, all the way up to their reference line.

The rub with Klipsch is in trying to navigate their product offering, as it’s a mess; too many products and a website in desperate need of an overhaul. That said, a comparable Atmos capable Klipsch system would be their R-625FA 5.1.4 Dolby Atmos Home Theater System. While you’ll save some money with the Klipsch system, you’ll also lose out markedly on bass as this system is paired with an anemic (compared to the Monolith) sub featuring a 12” driver and 400-Watt amp. If you want a Klipsch subwoofer comparable to the Monolith, you’ll want to look at the THX-1200-SW, but that’s also going to cost you roughly $500 more and drop you from a 15” driver down to a 12”. On the upside, that also translates to a smaller cabinet that’s almost 50 pounds lighter than the Monolith. Another option, for those who might not be aware, is Dolby Atmos add-on speakers. These are designed to sit atop an existing tower or surround and basically make them Atmos capable. There are a host of manufacturers offering them – Klipsch, Monitor Audio, ELAC, etc. If your budget doesn’t allow for a dedicated Atmos rig, upgrading your current system is worth considering, especially if you want to test the water before doing a deep Atmos dive.


This is, by far, the longest review I’ve ever written… though we’ll see what happens once my editor gets ahold of it. The reason? I had a blast with the Monoliths and truly enjoyed what I was hearing. Monoprice offers a 5-year replacement warranty and a 30-day money-back guarantee, both critical components when selling direct to consumers. Monoprice is a company (unlike say, Elite Screens) that strives to put the customer first. As such, if you place an order and decide after setup that you want more bass, or maybe want to go smaller on your front towers, just reach out and they’ll be happy to help.

Monoprice is a rare company, especially in 2021, that is willing to put the customer first. While Monoprice has priced their speakers aggressively, putting together a high-performance Atmos system is still costly. So do your research, then create your own real-world demo in your own home, but do it with the right company, which is to say one that not only makes a solid product but does their utmost to ensure their customers are able to enjoy it.

They’re on sale and it’s the holiday season – a great time to get off the fence, get into Dolby Atmos and do it right. Monoprice touts their Monolith line as “the best value in high-end audio” – they’re making one hell of a case.


Performance: 4.5 stars

Value: 5 stars

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