Monoprice Monolith K-BᾹS Bookshelf Speakers Review

 

In the world of home audio, Monoprice has established a reputation of providing low-cost electronics accessories such as cables, wall mounts, adapters, and so on. However, with the launch of their Monolith series of higher-end home theater gear at the 2016 CEDIA Expo, Monoprice looks to be trying to break away from their reputation as merely a source for very low cost products and instead become a destination for high-performance speakers and amplifiers as well. We acquired a pair of their new Monolith K-BᾹS bookshelf speakers for review, and now we'll see how serious Monoprice is about making headway into the realm of hi-fi speakers.

Appearance

The K-BᾹS speakers arrived sensibly packed with a large stiff foam blocks on the top and bottom of the speakers. The speakers were covered with a soft plastic bag to protect it from moisture and scuffs. Unpacking revealed a tall but narrow black speaker with a nice satin black finish and rounded edges. With the grille on, the K-BᾹS looks rather plain: just a black box. Removing the grille certainly gives this speaker more personality, as the woofer, tweeter, and Monolith emblem are unmasked. There isn’t much more to say here; overall the appearance is not bad at all, if not exactly dazzling. They look like a pretty typical bookshelf speaker. They don’t have a lot of pizzazz, but they are polite and clean-cut.

Design Overview

Here is where things get a bit more interesting. Monoprice claims a frequency response of 39 Hz to 20 kHz in a +/- 2.2 dB window. Now, a lot of manufacturers make bass extension claims that just aren’t plausible, especially for bookshelf speakers, and, given the bass specs of a speaker like this (a 5.25” polypropylene woofer) I would not believe a response like that on the face of it, but this frequency response window is strangely specific. What’s more, the K-BᾹS sports a design that could, in theory, reach very low for its size. The K-BᾹS uses a patented inverse horn design from speaker designer Phil Clements, which is a special enclosure design that allows relatively small cabinets and drivers reach much deeper frequencies than is typical for their size. Atlantic Technology speakers also uses same design in their H-PAS speaker, so it is no coincidence that the K-BᾹS speakers bear a strong resemblance to some of the Atlantic Technology speakers.

Within the cabinet, the backwave pressure caused by the rear-facing side of the cone get squeezed through a progressively smaller space as it travels toward the port. This squeezing increases air pressure as the pressure waves move through the cabinet. The pressure waves also pass by a chamber that acts as a Helmholtz Resonator. Helmholtz Resonance is the physical principle behind the phenomena where, when you blow air over the top of a bottle or jug, a distinct sound is produced, and it is how ports produce sound on conventional bass reflex speaker designs. The heightened flow of pressure waves amplify the sound produced by the Helmholtz Resonance in the K-BᾹS enclosure. Furthermore, the chamber by which the Helmholtz Resonance is created is heavily damped with Dacron, which helps to filter out harmonic distortions that might have developed from previous chambers. By the time the pressure waves exit the port on the K-BᾹS, they have been increased in amplitude and lowered in frequency, so the system can produce deep bass very efficiently.

For those of you who made it through that last paragraph, congratulations; you are well on your way to a degree in acoustic science! Everyone else can just take away the idea that the flow of sound waves within the cabinet are carefully controlled to optimize low frequency efficiency and extension, so this bookshelf speaker might actually be capable of its claimed low-frequency extension. The high frequencies are taken care of by a 1” ferrofluid-cooled titanium dome tweeter. The 5.25” woofer has a beefy motor that is needed to push the rear pressure waves through the various chambers. For a design like this to work best, the woofer needs some “working” distance in the interior of the cabinet from the port, so the tweeter is positioned below the woofer. The tweeter and woofer are given separate printed circuit boards on the crossover in an effort to reduce crosstalk. The crossover chokes are wound using large diameter wire, which Monoprice claims will enable these components to resist adding any coloration to the signal. The crossover uses low-loss polyester capacitors and inductors with the “highest grade” core material for 1st-order low pass and 2nd-order high pass signal separation between the drivers at 3 kHz. 

The cabinet itself is relatively sturdy, with a ¾” thick front baffle and ½” thick sidewalls. The interior chamber paneling does serve very effective double-duty as bracing to reduce cabinet resonance. The cabinet is generously stuffed with Dacron in order to damp resonances as well. The speaker terminals are a pair of sturdy binding posts. The cabinets do not come with feet attached, but Monoprice has included small rubber dimple ‘stickers’ that can be attached and used as feet. Overall, the design looks to be solid, with a reassuring attention to detail.

Monoprice Monolith K-BᾹS Bookshelf Speaker Conclusion

It makes sense for Monoprice to get into higher fidelity speakers, since the consumer audio market already turns to them for a variety of other audio-related items. Anything they launch is guaranteed a certain amount of exposure simply because Monoprice offers it. They could have just phoned in their effort with a nice-looking glossy speaker that had mediocre performance and still have made some money, but they have instead launched a speaker that sounds very good and measures well, although it does look somewhat plain. It can be seen that Monoprice was concerned about performance due to the complex internal enclosure design, a muscular midwoofer, and a crossover built from high quality components, all of which do add up in manufacturing cost. They might have been able to cut costs by using a more conventional approach but at the cost of absolute performance.

Monoprice has thrown their hat into a crowded ring of bookshelf speakers of similar cost, but there are certain features of the K-BᾹS speakers that help them to stand out. First, there is the low frequency extension; the K-BᾹS speakers have a very good response down to the low 40 Hz region- without the need for qualifiers such as “usable output”. Extension below 50 Hz is not easy to come by in bookshelf speakers in this price point and especially this size. Anyone looking for an affordable bookshelf speaker system that has to get by without a subwoofer would do well to strongly consider these.

Another admirable feature of the K-BᾹS speakers is the nicely uniform horizontal off-axis response. As mentioned before, the ‘Early Reflections’ curve can be a good predictor of in-room response, and the K-BᾹS speakers have a very smooth ‘Early Reflections’ measurement. These speakers do not need a heavily treated room to sound good; they will sound fine in a typical room. The good off-axis response was surely responsible for the excellent imaging that the K-BᾹS speakers projected. Another benefit of the uniform off-axis response is how much it broadens the coverage of area with good sound. The response out to 40 degrees off-axis is very good, so there is an 80 degree angle of decent coverage. If you have a wide area of seating that you want good sound for, or if you move around a lot when listening to your system, those circumstances make these speaker a good choice. A uniform off-axis horizontal response makes the sound better not just for one location but all of them. Because of this, the K-BAS speaker’s sound can compete very well with speakers that are quite a bit more expensive.

To briefly go over some of the other positives of the K-BᾹS speakers: it is an easy load for any amplifier to run and has no special requirements for amplification. It sported a very clean distortion profile for a 95 dB sweep run at 1 meter, which indicates good dynamic range considering it’s a bookshelf speaker with a 5.25” woofer. While the K-BᾹS speakers have good bass extension, the bass response is not elevated like so many other bookshelf speaker in its class; many of these speakers have a tendency to have a boost around 100 Hz or so, but the K-BᾹS speakers have a neutral bass response here. To top it off, the cabinet sports a slick satin black finish.

Monolith K-BᾹS Speakers

There is a lot to like about the K-BᾹS speakers, but for the sake of balance, I will go over some of the areas I would like to see some improvement, although I have to admit my criticisms are rather minor. First of all, while the on-axis frequency response is balanced overall, it does have some wrinkles that could stand to be ironed out. To be sure, I didn’t hear any clear flaws in my listening sessions with the K-BᾹS speakers, on the contrary, I thought the overall sound was nicely balanced, but the case might have been the content I used wasn’t majorly affected by incongruities the K-BᾹS frequency response, minor though they were. I think a more likely case is that the good off-axis response negated the shallow 3-6 kHz dip on-axis, and that the 700 Hz peak was too narrow and not high enough to significantly color the sound for me.

I also think that while the stock finish is not bad, having other finishes available for the K-BᾹS speakers would go a long way to making them more visually appealing, like perhaps some real wood finishes, or gloss finishes like pearl white. That would, of course, hike the prices of those speakers, but the extra options would be nice. One thing I will mention again here, even though this is not a gripe, is that these speakers are not suited for outrageous, headbanging, THX Reference level sound output. 84 dB sensitivity with a 8 ohm nominal impedance with a nominal power capacity of 50 watts mean that these speakers will safely able to run at around 100 dB at 1 meter outdoors continuously, maybe, (assuming typical content is being played back and not test tones) and around 105 dB peaks at 1 meter outdoors, maybe. The boundary gain of having to pressurize a smaller space means that it will be able to get a bit louder than those outdoors figures, but this is speculative; if you try running your K-BᾹS speakers at these levels and destroy them, I will not be held responsible! This is not a complaint against the speakers though, since few people will run them at these loudness levels, and few bookshelf speakers are designed to operate at levels much louder than that. I only mention this to caution those who like to listen at loud volumes in large rooms that there are more suitable speakers than the K-BᾹS.  

To bring this review to a close, I think the Monoprice K-BᾹS speakers are a solid choice for bookshelf speakers for the $500/pair cost. That $500 does not include shipping but does include a 1-year warranty. Monoprice does offer a full refund for the speakers for any reason if sent back within 30 days, so all you have to lose is shipping charges if you want to try them. I don’t think Monoprice will be seeing many returns on these speakers though; for most people, the K-BᾹS speakers are so good that they will be keepers.

Monoprice Monolith K-BᾹS Bookshelf Speakers Review

MSRP: $249.99 each
Monoprice, Inc.
11701 6th Street
Rancho Cucamonga, CA 91730

www.monoprice.com

877-271-2592

Monoprice Monolith K-BᾹS Bookshelf Speakers Listening Tests

In my approximately 24’ by 13’ listening room, I set up the speakers with equal stand-off distances between the backwall and sidewall, and equal distance between speakers and listening position, with weeter at ear level and the speakers facing the listening position directly. A Pioneer SC-55 receiver was used in ‘Pure Direct’ mode, so no tonal processing would interfere with the speakers’ natural sound, and no subwoofers were there to disguise its low frequency abilities. Speaker distance from listening position is about 10 feet.

Music Listening

My first choice for evaluating speakers is content with a very cleanly-recorded vocal. Since human hearing is so acutely tuned to the sound of human voices, if anything is ‘off’ about a speaker, it will be heard here. The recording I used for this was Bjork’s 2001 album ‘Vespertine,’ which has a very clear and intimate recording of Bjork’s voice. Accompanying Bjork’s vocals is an elaborate and intricate arrangement of percussion, bells, and plucked string instruments such as the harp, celesta, and clavichord. The album mostly has an intimate and close sound, but at times it shifts to a large, almost operatic soundscape with sweeping strings and a choral accompaniment. Bjork’s voice was exquisitely rendered by the K-BᾹS speakers, and I can find no fault with them in that aspect. What I first noticed was the precise imaging. The soundstage as presented by the K-BᾹS speakers was quite vivid. The instruments had well-defined placement, as did Bjork, and the soundstage was broad and enveloping. Although the recording has a close and intimate sound, the K-BᾹS speakers transported the listener inside of that space instead of being placed at a distance. The high-pitched attacks of the bells and plucked were rendered with fine detail. The bass was very good for bookshelf speakers, but they do not have the punch of a good subwoofer, or at least the punch I am used to, since I have this nasty habit of running the subs really hot. 

Another type of recording that is very good for assessing speakers is an instrumental solo. Here I turned to a long-popular album that I had only just discovered recently; George Winston’s ‘December’, released in 1982. ‘December’ is a superbly clean recording of some very skillfully played piano compositions with a seasonal flavor. The sound engineering and recording of the piano are first-rate, especially for a 35-year-old album. What many recordings of piano can miss are the high dynamics of the strike of the key, i.e. the attack of the sound envelope of each note. That attack has a power that a watered-down, compressed recording can turn into just some soft, mushy tinkling. ‘December’ has quiet piano passages, but also demonstrates the drama that the piano is capable of in other moments. The K-BᾹS speakers reproduced ‘December’ very well. As with ‘Vespertine’, the soundstage was well-defined. The piano sounded rich and clear. The strike was sharp when played as such, and the lingering decay of each note was not lost, even in notationally dense passages. This piano recording just sounded right with the K-BᾹS speakers, and I have nothing to complain about. Perhaps a larger and more powerful loudspeaker might bring out even more of the dynamics for those who like to listen at loud levels, but the K-BᾹS speakers executed the dynamics of ‘December’ well enough for me, and I did not listen to it at a soft volume.

Movie Listening

The first film I watched with the K-BᾹS speakers was ‘Fantasia 2000’, Disney’s long-awaited 1999 sequel to their ‘Fantasia’. I am betting readers already know about this film, so I won’t bother describing it again. The sound mix to ‘Fantasia 2000’ is, of course, almost entirely classical music (with a hint of jazz). The recording quality is outstanding, as one would expect from such a highly-anticipated feature, so therefore I used it to evaluate the K-BᾹS speaker’s sound on orchestral content. As with the other musical recordings, the K-BᾹS speakers produced a very convincing soundstage, with terrific imaging and great separation of instruments. The bombast and dynamics were there too, although the pounding of the bass drums certainly didn’t have the presence that a capable subwoofer or two would add. However, they reproduced the bass much better than one would have expected given their size. The timbre of each instrument was reproduced with veracity with many segments highlighting a particular instrument amidst the full orchestra. While the speaker pair was not able to match the enveloping sound of the full 7.1 soundtrack as replayed in a 7.1 system, they did provide an immersive experience thanks to their wide soundstage. ‘Fantasia 2000’, as heard on the Monoprice K-BᾹS speakers, was a delightful revisiting of this enchanting movie where great content and great playback equipment compliment each other.

For a more conventional film, I turned to ‘Everest’, the 2015 mountain-climbing drama based on true events. I had not previously seen ‘Everest’ but guessed that, given its production values and subject matter, it would contain a good sound mix to test a speaker’s capabilities. I was not wrong, since ‘Everest’ does indeed have a variety of scenes that would fall flat on an iffy speaker system. Scenes of avalanches and roaring snowstorms gave the low frequency capabilities of the K-BᾹS speakers a real workout, but it handled them much better than a typical bookshelf speaker. They did so well that at certain points I checked to make sure I had the subwoofers turned off. I am guessing there was very deep bass in the sound that it was missing, but I think that if I did not know what speaker was producing the sound, I would have thought a tower speaker was at work. The bass capabilities displayed by the K-BᾹS speakers in ‘Everest’ was most impressive for bookshelf speakers. Other sounds in the movie were presented nicely as well. Dialogue had no intelligibility issues, even with conversations carried out in the midst of a raging snowstorm. The music score, a mixture of traditional orchestral music with dashes of Tibetan music, was also given force by the K-BᾹS speakers. ‘Everest’ turned out to be a fine movie, and the K-BᾹS speakers were up to the task of recreating the intense conditions depicted in the film.

Another movie I watched with the K-BᾹS speakers was the 2009 science-fiction film ‘District 9’. I chose this film because of its very busy and dynamic sound mix that doesn’t shy away from bass. ‘District 9’ is rich with sound: science fiction sounds like alien speech and bizarre weapons, overlapping documentary production sounds, overlapping dialogue (sometimes with a multiplicity of languages), music scoring (both diegetic and non-diegetic), rapid editing between different situations, and gun battles with a variety of weapons and vehicles. A lesser speaker might turn this vibrant sound track into a cacophony of noise, but the K-BᾹS speakers managed to keep this complex soundscape coherent and lucid. As with ‘Everest’, I was surprised with the quantity and quality of bass these bookshelf speakers could produce. While a subwoofer would certainly made a contribution to the sound, the K-BᾹS speakers were still able to make ‘District 9’ watchable without one, certainly beyond what most bookshelf speakers in their price range and woofer size would have done.

Monoprice Monolith K-BᾹS Bookshelf Speakers Measurements and Analysis

The Monoprice K-BᾹS speakers were measured in free air at a height of approximately 9 feet and gated at 14 ms. At this window gate, some resolution is lost below 140 Hz, and accuracy is completely lost below 70 Hz and so that range should be ignored. The microphone was placed 1 meter away from the speaker at a height level with the tweeter.

Monoprice K-BAS Frequency Response Curves

The Monoprice K-BᾹS speaker measures well, although there are some slight imperfections. Most visible is a 3 dB, high-Q resonance around 700 Hz. This resonance may have high enough of a Q and low enough amplitude to be inoffensive, and in my listening I did not notice anything amiss in this region. What is likely to be more audible is the 2 dB dip from 3 kHz to 6 kHz, but since this doesn’t show up in the curves involving off-axis responses, I don’t think it is a problem. The scale of this graph and the low amount of smoothing (1/24 octave) make it a bit unsparing of any irregularities. The ‘Listening Window’ is exceptionally smooth above 800 Hz, which means this speaker should have a wide ‘sweet spot’ at least out to 30 degrees to the sides of the speaker, and it should be good for situations that need good coverage for that broad a listening area. The ‘Total Sound Power’ curve and its corresponding directivity index would seem to indicate some extra off-axis energy from 3 kHz to 6 kHz, which may mean those frequencies will be more reflected off-axis than neighboring frequency bands. However, the ‘Early Reflections’ curve is very smooth, and this bodes well for the end results since ‘Early Reflections’ can be a good predictor of the room sound, so extra off-axis energy from 3 kHz to 6 kHz is not something to be overly concerned about. For a good explanation of these curves and their significance, we refer the reader to this Audioholics article: Objective Loudspeaker Measurements to Predict Subjective Preferences.

 Monoprice K-BAS Bookshelf Speakers horizontal frequency response +/-90 degrees from axis: 3D view

Monoprice K-BAS Bookshelf Speakers horizontal frequency response +/-90 degrees from axis: 2D view

Looking at the K-BᾹS speakers’ horizontal dispersion pattern, we see a relatively uniform off-axis dispersion pattern. After 40 degrees off-axis, a dip develops at 12 kHz, but that is too high a frequency for that to be a problem, especially that far off axis. At 90 degrees we see a bit more energy forming from 3 kHz to 6 kHz, and this does explain the bump in the ‘Total Sound Power’ curve in that region, but up to that point the response in this region is nicely flat. This is the dispersion pattern of the woofer starting to tighten up before playback is handed off to the tweeter, which will have wider dispersion in this frequency range. The fact that we have to wait until 90 degrees for that to become evident means the woofer and tweeter are well-mated at the 3 kHz crossover point. Overall, this is a very nice response, and bodes well for those who need a speaker that sounds good in more than just one listening position.

Monoprice K-BAS Bookshelf Speakers Polar Map

The colorful chart above is really just presenting the same data as in the two horizontal dispersion graphs above it, only shown from a top-down view and using color to indicate amplitude instead of raised lines. Presented in this way, we can more easily see certain trends from the other graphs. For example, we do see a slight narrowing of dispersion above 6 kHz. We see a hint of the 3 kHz crossover point from the slight waist-banding around that region, but it is pretty well controlled. We can more easily see the uniformity of the dispersion out to 40 degrees; past that point, there is more energy under 6 kHz, but it keeps a relatively smooth dispersion down to 1 kHz. The bottom line is essentially the same as we have seen so far; good coverage out to 40 degrees off-axis, so very good speakers for covering a wide area with decent sound and not bad control of sound outside of that point.

 

Monoprice K-BAS Bookshelf Speakers vertical frequency response +/- 90 degrees from axis: 3D view

The above graph displays the dispersion of the K-BᾹS speakers on its vertical axis. Before you panic, it should be said that the vertical dispersion isn’t nearly as important as the horizontal dispersion. This is a very typical pattern for this kind of bookshelf speaker. We see a narrow strip of a regular response on-axis, but lobing effects quickly create deep nulls as the response goes past ten degrees off axis in either direction. This is the result of the woofer and tweeter cancelling out each other’s sound around the crossover point; this is inevitable with this type of driver layout. On this scale, the negative degrees are below the tweeter, and positive degrees are above the tweeter. What this graph says is that, as with most speakers, the K-BᾹS speakers should not be placed on their side and are best listened to with the tweeter roughly at ear level.

Monoprice K-BAS Bookshelf Speakers Impedance and Phase

The impedance graph of the K-BᾹS speakers show a fairly benign electrical load. Our own measurements seem to be a couple of ohms above that of Monoprice’s. They claim an impedance minima of 4.2 ohms, but we measured a 6.2 ohm minima, although our profile shape matches theirs. Either way, most amplifiers will have no problem with these speakers; even an entry-level AVR should be able to run them fine. According to our measurements, these can easily be characterized as an 8-ohm speaker. Our sensitivity measurements showed the K-BᾹS speakers to have a 84 dB for 2.83v at 1 meter. Monoprice has these speaker spec’d at 87 dB sensitive, but they do not say if that was taken at 1 watt or 2.83v, although either way would not match our results. If that spec was taken at half-space, it would match our results, and sometimes manufacturers measure sensitivity at half-space without declaring it in the specs. We have to stress that, while that 84 dB sensitivity might seem low, it is very typical for a bookshelf speaker of these specifications, and many manufacturers have ways of stretching the sensitivity measurement. This is a speaker that can get loud, but it is not a speaker that one would want to use as mains for a big, dedicated theater room. I blasted these speakers pretty hard and didn’t sense any obvious distortion or compression. However, there is only so much a bookshelf speaker with a 5.25” woofer can do. I think these would get more than loud enough for most people’s tastes.

Monoprice K-BAS Bookshelf Speaker total harmonic distortion

The above graph depicts the total harmonic distortion of the K-BᾹS speakers at 90 dB and 95 dB sweep levels. This level of distortion looks very good for this loudness level, especially in lower frequencies. The only thing in here that could come close to being audible is the bump almost touching 3% around 700 Hz, and it would have to be using a pure tone in laboratory conditions to be heard. The third harmonic is the dominant harmonic throughout this distortion profile, but the second harmonic does crop up at the 700 Hz bump, which is almost entirely second order harmonic distortion. The ridges of distortion in lower frequencies would be totally inaudible, since human hearing is much less sensitive to distortion in that band. The beefy midwoofer driver looks to be paying off in these tests. This speaker could have taken higher levels than this and still retained its composure, but the point was already made. This is a fine showing, and the K-BᾹS speakers can stay clean at relatively loud levels.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Build Quality
Appearance
Treble Extension
Treble Smoothness
Midrange Accuracy
Bass Extension
Bass Accuracy
Imaging
Dynamic Range
Fit and Finish
Performance
Value