M&K Sound X15+ THX Dominus Certified Subwoofer Review Page 2

A second key feature the subwoofer lacks is a Bluetooth control app—all adjustments are manual and must be made using the controls on the sub's rear panel. (A standard remote control also isn't provided.) Granted, for most listeners setup happens once and the subwoofer is not touched again for years, but I've gotten used to making adjustments from the couch versus doing things the old-fashioned way of reaching around back.

The X15+ features standard controls such as a variable phase knob (0-180 degrees), three low pass filter settings (Fixed 80Hz, Variable, and No Low Pass THX Mode), bass level reference (THX Fixed and Variable) and a switch to choose between THX Bass EQ (for movies) or Anechoic MK EQ (for smaller rooms and music). I found I got the best results using No Low Pass THX Mode (the crossover was set electronically in my pre/pro), THX Bass EQ, and THX Fixed bass level reference (level adjustments made with my pre/pro). The sub's connections include both balanced XLR and RCA inputs and outputs. There's also a non-grounded detachable power cord as well as a three-way power switch (Off, Auto, and On).

No user manual shipped with the X15+, though I was able to download one from the M&K Sound website. Given all of the various onboard controls, it's worth reading through before you begin the setup process. (And no, you won't have to surrender your man card if you take time out to read the manual.)

Uncrating this 135-pound beast was a two-person job. The sub arrives double-boxed, and once you get it on the floor it's somewhat easy to maneuver around the room as long as you have a friend on-hand to assist. Given the large enclosure (20.3 x 32.8 x 18.1, WxHxD), placement can be tough depending on your room. In my case, I tried putting it in a convenient location along a side wall. This positioning ended up being a huge mistake and lead to a nasty dip in bass response at 25 Hz. I then repositioned the sub one-third of the way across my front wall and got much better, though not perfect, results (see measurements).

I ran than the X15+ in my system for well over a week to acquaint myself with its distinct sound signature before doing any heavy testing. If you've never listened to a system with an M&K Sound sub first-hand, it's something you need to experience. There are a ton of great subwoofers on the market, but M&K models do have a unique and extremely precise sound.

After that first week of break-in, it was time to see how deep and loud this baby would go. Initial impressions were very favorable. First off, the sub-20Hz performance of the X15+ was extremely impressive. I did an A/B comparison with the full suite of reference subs that I use in my system—SVS PC-Ultra, HSU 15H-MK2, and dual JL Audio F110s—and the X15+ on its own was able to produce higher measurable output below 17Hz (it's rated down to 16 Hz, so it more than meets its specifications). As you can see by the measurements, the X15+ holds its own against my reference EQ'd sub array. (If I was able to test a pair of X15+ subs, I'd be able to overcome my 40Hz room node because utilizing multiple subwoofers evens out frequency response throughout the room.)


Edge of Tomorrow is a movie that begs for an Ultra HD Blu-ray release along with a newly minted Dolby Atmos soundtrack, but alas, we have to slum it with the old Blu-ray for now. Regardless, this movie is one of my favorite guilty pleasures both for its entertainment value and grin-inducing DTS-HD Master Audio 7.1 soundtrack. As the film opens, there's a low-frequency sweep that really separates the subwoofer men from the boys. In fact, my reference subs can't play this sequence at anything louder than –10dB without massive distortion. I started at –15dB with the X15+ and it handled that with no problems. Next, I tried –10 dB (pass), then –5 dB (pass), and finally 0dB from reference. To my surprise, it never bottomed out or lost any clarity or precision. Perfection!

Next up was my usual battery of movie torture tests: Interstellar (black hole sequence), 13 Hours: The Secret Soldiers of Benghazi (compound attach), The Greatest Showman (intro song), and Hacksaw Ridge ("soften them up" scene). The M&K sub's ability to dig deep and play loud proved mighty impressive—at one point I was afraid it was going to wake the dead in a nearby cemetery.

So, the X15+ shines with movie soundtracks, but can a 15-inch sub work equally well with music? YES! I cued up the Imagine Dragons Smoke & Mirrors Live Blu-ray with its reference-quality Dolby Atmos soundtrack. I initially planned to just listen to the intro and then jump ahead to "Radioactive," both of which feature outstanding bass, but I ended up so enthralled that I sat through the entire 102-minute concert, marveling at the M&K Sound sub's accuracy and precision. Over subsequent days I found myself going through various concert discs to recapture my initial experience: Eagles Farewell 1 Tour — Live from Melbourne, Hans Zimmer: Live in Prague, and Pink's Funhouse Tour: Live in Australia, among others. In each case, I grew more and more impressed with the 15X+.

To say I enjoyed my time with M&K Sound's X15+ would be an understatement. In fact, I've enjoyed it so much it's not leaving my home. This push-pull sub design plays deep and loud, and it passed the most strenuous tests I could throw at it with ease. Add in the impeccable build quality and peace of mind that THX Dominus Certification brings to the table, and acquiring it became an easy decision despite the lack of conveniences such as app control or a handy remote. In the end, everything comes down to performance and the quality of the bass, and by this measure it's the best subwoofer I've encountered in two decades of audio product reviewing.

jeff-henning's picture

For $6K, this sub is over priced a bit. Not saying that it doesn't sound good because I'm sure it does

Rythmik Audio offers the dual-opposed, G25HP Direct Servo sub. It offers solid response down to 14Hz and 1.8kW of real, continuous power. It's also half the price and, since it's a servo sub, it will be cleaner.

Also, in piano black, being less than $3K, why would you even consider this sub?

Hey, the push-pull design does reduce distortion, but only the even harmonics. The more egregious distortion is odd order harmonics. They are what you will hear more easily and will, in your brain, register as unnatural. This is why a servo sub will sound better. Hey, a push-pull servo would be even better.

Which begs the question, why has S&V never reviewed a Rythmik servo sub? They offer not only the best performance of competitively priced subs, but of any subs on the market, period.

Also, 4 or 6 small subs will out-perform 1 huge sub and they are a lot easier to move.

TFK49's picture

In past reviews you have stated that you have 4 subwoofers in your home theater set up. In this review you stated that you liked the M&K so much you are keeping it. Just curious, will it replace 1 of the 4 subs in your system, or will it replace them all? It seems like a beast.

David Vaughn's picture
This sub ended up replacing a SVS SB3000 (which is now installed in my den system). In fact, I'm running five subs now, but dual JLAudio F110s are treated as one sub (master & slave) and are co-located. All are run through a MiniDSP and EQ'd with a MiniDSP vis RoomEQ Wizard.