Review: Klipsch RB-81 MKII

This week we tested the Klipsch RB-81 MK2, a substantially sized bookshelf loudspeaker whose 8″ driver and dome tweeter team up to produce an ultra-realist sound. A compact model that seems to offer many of the benefits of a larger one…

If you?ve been keeping up-to-date on the latest products designed and manufactured by trusted names on the hi-fi market ? and especially Klipsch ? you no doubt already know that the American brand has recently renewed its Reference range. Meanwhile, certain models from the previous generation are still part of the brand’s catalog. These exceptional models, namely the Klipsch RF-7 MKII floor-standing speaker, the Klipsch RC-64 MKII center speaker and the Klipsch RB-81 MKII compact speaker, don’t have successors in the new Reference Premiere range. These uncompromising products put sound quality ahead of esthetic considerations and will be sure to attract the attention of any guests you invite into your living room.

Klipsch RB-81 MKII : a rare bird

With its 8″ driver, the Klipsch RB-81 MKII is quite the exception. Apart from the serene Monitor Audio Silver 2 and a few models produced by Dali and Jamo fitted with 7″ drivers, manufacturers who dare to put a large driver into a compact loudspeaker are few are far between.

This is unfortunate, as an 8″ driver is often the key to a truly lively listening experience rich in bass frequencies.

However, an 8″ driver is designed to move a large amount of air, which entails the use of a large cabinet. If this requirement isn’t respected, an 8″ driver will struggle to produce convincing bass frequencies, thus defeating its purpose.

The Klipsch RB-81 MKII is 23 cm wide, 48 cm tall and 31 cm deep. The Klipsch Heresy III aside, the Klipsch RB-81 MKII is one of the biggest bookshelf loudspeakers on the market.

Klipsch RB-81 MKII : presentation

The Klipsch RB-81 MKII is a 2-way model which pairs up an 8-inch bass-medium driver along with a compression driven, titanium dome tweeter mounted on an acoustic horn. It has a frequency response of 44 Hz to 24 kHz (within a range of 6 dB) and a sensitivity of 97 dB at 1 kHz for 1W (measured at 1 m). In other words, the Klipsch RB-81 MKII is a ?powerful’ loudspeaker capable of putting out a huge amount of sound, which means that you can obtain a high volume even with a less powerful amplifier. A 2×20 W integrated amplifier can deliver a very convincing result with the Klipsch RB-81 MKII, even if its 150 W power handling suggests that a more powerful amplifier would be more appropriate.

The loudspeaker?s cabinet is composed of MDF panels with a black, wood-effect vinyl finish. The front of the loudspeaker is plastic, and this choice of material has allowed Klipsch to produce a one-piece panel which conceals the driver?s basket and fastenings while integrating the Tractix horn and the bass-reflex port. The loudspeaker?s grill is composed of black acoustic cloth and held in place with magnets. The rear of the loudspeaker features terminals which allow for bi-amplification and are compatible with banana plugs. Metal straps are pre-installed to allow for standard single-amplification.

Klipsch RB-81 MKII : drivers

The 8-inch driver features a copper and ceramic cone (Klipsch Cerametallic technology) and a very powerful magnet (which explains the loudspeaker?s high sensitivity rating). This driver is fitted within a bass-reflex enclosure with a front-firing laminar port, making it possible to install the loudspeaker against a wall or on a bookshelf. Its frequency response ranges from 40 Hz to approximately 1.4 kHz, at which point the tweeter takes over.

The 1-inch titanium dome tweeter is equipped with a rear compression chamber to increase its sensitivity. The tweeter is mounted on a Klipsch Tractrix horn in order to amplify medium frequencies up to about 1.5 kHz. The main benefit of this horn-based mechanical amplification technique is that it allows the driver?s cone to make very small movements, thus keeping distortion to an absolute minimum while enhancing the transient response. A conventional tweeter is very limited in comparison. Having developed horns for 80 years, Klipsch knows how to avoid the pitfalls sometimes associated with this technology (coloration, sound projection). Moreover, while a non-horn-loaded tweeter loses a considerable amount of energy beyond a distance of 5 meters, the horn-loaded tweeter makes itself clearly heard from twice as far away.

Klipsch RB-81 MKII : electronic filter

The loudspeakers offered as part of this second generation (MKII) of the Reference range feature optimized electronic filters. Klipsch has situated the crossover frequency for the two drivers at 1.4 kHz, which is lower and farther from the critical range of 2 to 3 kHz than on previous models. This is of utmost importance not only because our ears are very sensitive to these frequencies, but also because electronic filters always create phase rotations at their cutoff frequency and this phenomenon can jeopardize sound quality. Since the horn acts as a magnifying glass, we can thus only applaud the brand for setting the cutoff frequency at 1.4 kHz. Because the tweeter covers a very wide range of frequencies, the sound greatly benefits from its fast response, and the restitution is better than if the 8-inch bass driver were to cover those same frequencies itself. The bass driver is thus reserved for the frequencies where it is truly necessary.

Klipsch RB-81 MKII : test conditions

For our test, we paired the Klipsch RB-81 MKII compact speakers with the Denon DRA-100 stereo receiver and the NuPrime IDA-8 amplifier, we used NorStone Classic 250, Viard Audio Silver HD12 and Audioquest Rocket 88 cables. We listened to FLAC files (DLNA streaming from a smartphone to the DRA-100 and to a Raspberry Pi 2 with Volumio for NuPrime via a USB connection.

Klipsch RB-81 MKII : impressions

The Klipsch RB-81 MKII delivers an absolutely captivating sound. The brand has judiciously crafted this sound to offer a tight and richly textured restitution of higher bass frequencies which is in perfect balance with a sharp treble register. In this respect, the RB-81 MKII, while featuring the same bass driver as the Klipsch RP-280F and Klipsch RP-280FA models, seemed more lively to us. The Klipsch RB-81 MKII is fun to listen to and a polar opposite of the sanitized sound put out by some compact speakers. There are pleasant surprises at every turn, and our constant wonderment made for a truly active listening experience. We wanted to listen again and again!

We listened to a number of different tracks with the Klipsch RB-81 MKII ? a lot of jazz, a little bit of opera and some pop music, in addition to watching several film excerpts and a few concerts.

The sound never failed to fill our entire living room, and spectacularly so considering the size of these compact speakers.

Bass: the front-firing bass-reflex port is relatively short and thus amplifies the higher bass frequencies. This, combined with the driver?s agility, gives the Klipsch RB-81 MKII an enormous amount of energy. There?s a bit of a fierce edge that is extremely pleasing. A generous amount of punch in the higher bass frequencies and a wide range of information that our ears hardly ever hear from a conventional compact loudspeaker. A vigorous bass, not at all sloppy; Klipsch announced 45 Hz and delivered.

An upward curve in the higher bass frequencies gives a lot of energy to the listening experience, while an adequate frequency slope prevents the bass range from sounding hollow. The Klipsch RB-81 MKII is even more impressive than many floor-standing models.

Medium : very well organized, human voices are extraordinary. Excellent timing thanks to the Cerametallic cone for the low-medium and the bright, titanium dome for the high-medium frequencies.

Treble: The Klipsch RB-81 MKII?s impressive dynamic range lends credibility to the sound. The tweeter steps in at only the most opportune moments. For example, we only hear it a little with human voices (which is normal, yet many other tweeters color voices) and the tweeter knows how to be bright when necessary. As we write up this test, the percussion of recordings surprises us from 7 m away! In addition, the Tractix horn is a real plus.

Klipsch RB-81 MKII : conclusions

What we liked

• The captivating, organic sound
• The punch of the higher bass frequencies
• The controlled dynamic range
• The tasteful brightness of the high frequencies
• The very, very immersive 3D soundstage

What we would have liked

• A natural wood veneer? But at this price, that?s surely a lot to ask?

The Klispch RB-81 MKII is a force to be reckoned with ? and only in the best of ways. We?d be delighted to listen to compact loudspeakers of this quality, and for this price, more often. The sound it delivers is exceptionally coherent from the lowest to the highest frequencies, while being exhilarating and spectacular when the recording allows. We recommend this model for amateurs of the rock, electro and jazz scenes, in addition to those who enjoy watching films and concerts. Based on our experience, it?s Klipsch?s best compact loudspeaker ? with the exception of the Heresy III. We had a lot of fun listening to this loudspeaker.