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Monoprice Monolith K-BĀS review

Monoprice’s K-BAS bookshelf speakers serve a bounty of bass, but left us hungry for detail

Monoprice Monolith K Bas review speakers covered
Monoprice Monolith K-BĀS
MSRP $249.99
“Monoprice’s K-BAS bookshelf speakers bust out big bass, but may be too laid back for audiophiles.”
  • Powerful bass
  • Stealthy appearance
  • Excellent fit ‘n finish
  • Extremely affordable
  • Treble is far too mellow
  • Uneven midrange lacks sparkle
  • Sonic details obscured

Back in the day, Monoprice made its mark by offering ultra-affordable, high-quality, house-branded A/V cables and accessories, saving budget-conscious consumers copious caches of cash in the process. Monoprice recently expanded into consumer electronics, garnering high praise for maintaining its value proposition in the process. Entry-level home theater equipment quickly followed suit. So, when word came that Monoprice was turning its attention to the high-end audio sector, we sat up and took notice, waiting to lay ears on some of its loftier audio offerings.

We didn’t have to wait long, and received its K-BĀS bookshelf speakers for review. Part of the company’s audiophile-oriented, Monolith series of A/V products, the K-BĀS speakers promise to be “The best value in high end audio” and “Performance driven products at value driven prices.” Read on to find out if the Monoprice K-BĀS live up to that goal.

Out of the box

Weighing in at a solid 14 pounds per speaker, the K-BĀS impressed us with their heft and solidity. Since each enclosure is outfitted with only two drivers, it’s a good bet that cabinet thickness accounts for much of the weight, often a good indicator of robust build quality. That cabinet takes the shape of a 15.6-inch tall, 7.2-inch wide and 13.0-inch deep, rectangular box, one that’s noticeably taller and trimmer than its bookshelf brethren.

A closer examination of the K-BĀS shows a high level of fit and finish for the price. The satin black paint feels smooth to the touch, and it’s a nice change from the vinyl wrap often found on the competition. Save for the tweeter dome and binding posts, all visible components are finished in complementary shades of black for a stealthy, understated appearance.

Features and design

K-BĀS stands for Kinetic Bass Amplification System, and it’s the patented tech Monoprice uses to get big bass from such a small speaker. In short, the technology is based on reverse horn-loading technology whereby a speaker cone’s rear wave output is first funneled through a progressively smaller, acoustically dampened enclosure space. It then passes through a resonance chamber before making its way to the enclosure’s port. This process increases the air pressure at the chamber, which in turn amplifies the low frequencies exiting the port. The result is said to be deeper and better-controlled bass than traditional cabinet designs muster.

Nearly all visible components are finished in complementary shades of black for a stealthy, understated appearance.

Indeed, the K-BĀS’s specified cut-off of 39Hz is much lower than one would logically expect from a single 5.25-inch, polypropylene and mica woofer. Couple that woofer to a liquid-cooled, one-inch, titanium dome tweeter, and the stated frequency response stretches from 39Hz to 20kHz within +/- 2.2dB limits. Protective black cloth grilles are included if you prefer the drivers remain hidden. Crossover frequency is set at 3kHz through a 1st-order filter on the woofer, and a 2nd-order network on the tweeter.

Sensitivity is specified at 87dB, though measuring distance and input power are not given. A nominal 6 to 8-ohm impedance, however, means even entry-level receivers should have no trouble supplying the K-BĀS with sufficient power. Power handling is listed as 50 watts per channel RMS, and 150 watts peak.


We placed the Monoprice K-BĀS speakers on 24-inch stands, spacing them anywhere from 6 to 8 feet apart. They sat 1 to 2 feet away from the wall behind them and were toed-in towards our centered listening position, which ranged from 7 to 10 feet away. Room dimensions ranged from as small as 10 x 12 x 8 feet, to 11 x 22 x 8-feet at the high end. Though the K-BĀS weren’t terribly sensitive to these room sizes, varying their toe-in angle resulted in drastic changes to the overall frequency balance.

Monoprice Monolith K Bas review cover
Bill Roberson/Digital Trends
Bill Roberson/Digital Trends

Sitting between the speakers without toeing them in, the K-BĀS sounded far too shut-in from the upper mids through the mid-treble. We eventually settled on pointing the tweeters directly toward our ears for the smoothest obtainable response. Even with a direct, on-axis toe-in, listening position measurements with a test tone sweep confirmed a hollowed-out treble response from about 2.2kHz to 8kHz, reaching a minimum of approximately -4.2dB between 2.5kHz and 6kHz when taking the level between 1kHz to 2kHz as the reference.

Simply put, be sure to point the K-BĀS speakers directly towards your ears if you’re looking for the smoothest and most accurate sound. Going off-axis can rapidly degrade audio quality.


Naturally, we expected to hear supremely big bass from these speakers and, in this regard, the K-BĀS lived up to the hype. Spinning up Esa-Pekka Salonen and the L.A. Philharmonic’s CD of the Rite of Spring, the Monoprice Monolith K-BĀS packed a portentously powerful wallop on the opening movement’s thunderous tympani rolls. We’ve heard more than a few pricey floorstanding speakers struggle to get this right, but the K-BĀS breezed through this torture test with relative ease.

No bookshelf loudspeakers in our experience can match the bass impact these speakers deliver.

As good as acoustic bass was through these speakers, electronic bass sounded even better. The K-BĀS seemed to thrive on music with preternaturally prodigious lows, such as those heard on Majid Jordan’s A Place Like This, Kendrick Lamar’s DAMN., or Drake’s Views. The Monoprice speakers always sounded sufficiently taut, appropriately punchy and satisfyingly weighty through the lower registers. If big bass is your bag, you’ll relish the way the Monoprice K-BĀS do it.

While the K-BĀS are undoubtedly champions of bass, the rest of their frequency range isn’t up to the same standard. Due to the speakers’ carved-out treble, aggressively hot or bright recordings sounded well balanced, but other tracks and movies sounded noticeably recessed. On Chris Isaak’s San Francisco Days, for example, the shakers on “Two Hearts” lost enough of their presence and detail that we had to concentrate to hear them; cymbals and high hat on “Can’t Do a Thing” were also missing much of their sizzle, shimmer, and decay.

This treble recession was especially evident on instruments whose power response lies in this region. Both massed and solo strings on Janine Jansen’s performance of Britten’s violin concerto lost a good measure of their silken sheen, sparkle and radiance, and the K-BĀS glossed over tonal gradations and other textural details. Again, the mellow highs were less of a problem with music that already lean towards the treble-heavy or excessively forward side, so if your listening diet consists mainly of such recordings, you may find the Monoprice K-BĀS make for a refreshingly easy-listening antidote.

Monoprice Monolith K Bas review speakers side
Bill Roberson/Digital Trends
Bill Roberson/Digital Trends

The K-BĀS’s diminished treble presence seems to affect other sonic parameters as well, namely soundstaging prowess. In our experience, the soundstage as presented on Jansen’s Britten concerto can bloom deep into the room, practically bathing the listener in a fully immersive auditory experience. Through the Monoprice speakers, the soundstage extended widely enough but sounded flat, devoid of depth, and as if it were stuck close to the plane presented by the speakers. We realize most folks interested in these speakers will hardly, if ever, sit in “the sweet spot” when listening, so if you’re not in the habit of doing so, the K-BĀS’s soundstaging capabilities may be of little to no concern.

The Monoprice speakers seemed uneven through the midrange’s upper and lower sections, but fared better through its center. On Kings of Convenience’s Riot on an Empty Street, Erlend Øye’s warm baritone vocals can sound captivatingly rich, soothing and appropriately textured through well-balanced or neutral speakers. Unfortunately, the K-BĀS pushed his vocals too far to the warm side, making them sound a bit thick and congested. Upper midrange female vocals also sounded somewhat recessed and rolled-off, such as Alison Krauss as heard on her album New Favorite. Here, her high notes were blunted and robbed of their piercing power, and brilliant sustain.

The K-BĀS glossed over tonal gradations and other textural details.

In terms of overall output, we had no trouble pushing the Monoprice speakers to satisfying levels while using an amp rated at the recommended 50 WPC RMS. We did however determine that their 87dB sensitivity rating might be a bit optimistic. We usually needed to increase the volume about 3 to 3.5dB to match the output levels of most of the bookshelf speakers we’ve tested that meet this spec. A quick check with an SPL meter verified our findings to be accurate.

Nevertheless, the K-BĀS was plenty loud enough for our listening sessions. Unless you’re fond of listening at rock concert levels, we wager you’ll also find their volume capabilities entirely sufficient. Taken as a whole then, the Monoprice Monolith K-BĀS proved to be an interesting mix of strengths and weaknesses. If your listening tastes cover a comprehensive range of music, you may find the K-BĀS too laid back and mellow to be musically satisfying over the long haul. However, no bookshelf loudspeakers in our experience can match the bass impact these speakers deliver, so if that criteria is tops on your list, you may find the Monoprice K-BĀS dovetails nicely with just what you’re looking for.

Warranty information

The Monoprice Monolith K-BĀS speakers come with a limited five-year warranty for defects in materials and workmanship.

Our Take

The Monoprice Monolith K-BĀS speakers deliver big bass as promised, but their overly mellow, laid-back balance won’t be to everyone’s liking.

Is there a better alternative?

Available for the exact same price, the Elac Uni-Fi UB5 are one of the class leaders in the sub-$500/pair, bookshelf loudspeaker category thanks to their overall sound quality. Their three-way design also offers excellent low-end response, and their imaging and sonic refinement from the midrange up are simply unparalleled at the price. However, the K-BĀS have greater low bass extension and output.

At $50 more, the new KEF Q150 are sonically on par with the Elacs and also surpass the Monoprice K-BĀS in terms of overall sound quality. Their slightly recessed upper midrange makes them a good match with aggressive-sounding electronics, and they manage to avoid the K-BĀS’s excessive suppression in this region. The K-BĀS still dig a bit deeper in the bass however, and their front-facing port offers more placement flexibility.

How long will it last?

Since the Monolith K-BĀS are passive loudspeakers and feature durable build quality, we imagine they’ll last for decades or more, provided they’re used according to the manufacturer’s recommendations.

Should you buy it?

Buy the Monoprice Monolith K-BĀS loudspeakers if you specifically need the biggest bass you can get from the smallest enclosures. Otherwise, we’d recommend investigating other options: similarly priced alternatives will provide better overall sound quality, especially through the treble region.

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