Monolith by Monoprice 13″ THX Ultra-Certified Subwoofer Overview

Today Monoprice started shipping their 13″ Monolith THX Ultra-certified subwoofer. These new subs are meant for rooms of 3000 cubic feet or larger. At $1600 a pop, they aren’t cheap but are they worth the money? Let’s examine the relative strengths and weaknesses of the newest addition to the Monolith line of subwoofers. First the specifications and then we’ll break down what is really important.


Driver Size13″
Driver Material2 layer long fiber pulp/glass fiber cone
Voice Coil100mm, with high-temperature aluminum wire and black anodized aluminum bobbin
SurroundFEA optimized NBR (nitrile butadiene rubber)
MotorFEA optimized undercut T‑pole focused field, with 2 aluminum shorting rings
MagnetCeramic Y35, 2 pieces, 300 oz. total
Xmax28mm (one‑way)
Xmech90mm (peak‑to‑peak)
EnclosureSealed or vented HDF cabinet with horizontal and vertical bracing
FinishBlack Ash
Amplifier2000 watts (RMS)/3800+ watts (peak)
Harmonic Distortion<1% 20~100 Hz (90dB @ 1m)
Variable Level Control+15/‑20 dB
Reference Level100mV @ 40Hz (89dB @ 1m)
CrossoverInline/Bypass variable 40~160 Hz
Variable Phase0~180 degrees
Inputs2x RCA, 1x XLR
Outputs1x XLR
Signal Turn OnSelectable always-on/auto
Auto Turn Off Time30 minutes
Dimensions23.8″ x 20.3″ x 29.1″ (605 x 515 x 740 mm)
Weight153.2 lbs. (69.5 kg)
    Frequency Response (‑6dB)SealedVented (2 ports)Vented (3 ports)
    Extended EQN/A16~200 Hz16~200 Hz
    THX® EQ20~200 Hz19~200 Hz20~200 Hz

Monolith by Monoprice 13″ THX Ultra-Certified Subwoofer Build Quality

As we scan the specs of any sub, we look for a couple of things. The first thing that jumped out at us was the enclosure. Size-wise, the Monolith by Monoprice 13″ THX Ultra-certified subwoofer is about as small as a 13″ driver and three ports will allow. What is interesting is that they constructed the enclosure out of HDF. Normally, speakers and subwoofers are constructed out of MDF (medium density fiberboard). HDF is harder to work with and much heavier.

This, of course, led us to check out the weight. At 150+ pounds, the Monolith by Monoprice 13″ THX Ultra-certified subwoofer is no lightweight. If you are planning on ordering one of these monsters, make sure you have a place picked out for it and (hopefully) a dolly. We were glad to see that Monprice had included rounded corners on this subwoofer. This is not a sub that needs sharp corners.

Monolith 13″ Subwoofer Performance

The Monolith 13″ subwoofer is rated down to 16Hz in Extended EQ mode and 20Hz in THX mode. As THX mandates 20Hz performance, this is actually a pretty nice feature. While Monoprice didn’t need to include the Extended EQ mode, they did so that they could get the THX Ultra certification, and wring as much performance out of the subwoofer as they could.

The 13″ driver has lots of excursion meaning it can get loud but only if it has the right amp. Monoprice has given the Monolith THX Ultra-certified subwoofer an amp beefy enough to get that 13″ driver moving. At 2000 watts (3800 watts peak), the sub should have all the power it needs. It also includes integrated DSP so that you can access the two output modes. What isn’t available is any way to tune or alter those modes. No parametric EQ or app control.

Lastly, Monoprice has included port plugs so that you can tune the Monolith 13″ THX Ultra-certified subwoofer to your liking. When we look at the measurements, we see what we would expect. If you plug all the ports (sealed), the subwoofer performance drops off earlier but more gradually. As soon as you open the ports, we get more extension but a quicker drop off. The more ports you open, the louder the bass gets.

One thing we found strange was that there was no measurement for a single port open (two ports plugged). We assume that Monoprice does not recommend running the Monolith 13″ THX Ultra-certified subwoofer in this configuration.

Should You Buy One?

The closest sub we could find to compare to the Monolith by Monoprice 13″ THX Ultra-certified subwoofer, was the SVS PB-3000 subwoofer. The SVS is smaller, lighter, has one fewer port, and a smaller amp. When we compared the measurements, the Monolith had more output overall and lower extension in ported mode. The SVS has their app for control while you’ll have to control the Monoprice from the amp (like it is 2010). The SVS costs $300 less, but they both have similar finishes.

For a little extra money, the Monolith by Monoprice 13″ THX Ultra-certified subwoofer definitely delivers extra performance over the SVS. But it isn’t without giving up some of the features of the SVS. For $1600, the Monolith pretty much delivers everything you want out of a sub. If you have a large (3000+ cubic foot) space, this sub will easily fill your room.

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