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, co ngratulations; 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.

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