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Klipsch Reference RB-51 II

Bookshelf speakers

43 Reviews | 1 question - 8 answers

Item # 714RB51IIB

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Our take on the Klipsch Reference RB-51 II

The RB-51 IIs also use newly machined, light-yet-rigid Cerametallic woofers with a folded edge to produce smoother mids and tighter bass. The specially treated aluminum in the cones help to dampen unwanted vibrations and distortion, while an integrated dustcap gives them a cleaner look and adds stability. And the rigid, braced cabinets come in a handsome woodgrain vinyl finish.

A smart balance of performance, size, and value

Klipsch® has a no-compromise attitude when it comes to speaker performance — which is why the conveniently sized, modestly priced RB-51 II bookshelf speaker can sound so good. They offer up dynamic, full-bodied sound that makes them ideal for medium-sized rooms. Building on Klipsch's previous Reference speaker line, the Series II models have updated drivers and a new crossover system for even more spacious sound. So they're equally impressive whether you're watching a movie or listening to music.

Grille off

Horn technology for "front row" sound

All Reference Series II speakers feature a redesigned version of Klipsch's famous horn-loaded tweeter. Because high-frequency sounds are more directional than bass frequencies, it's especially important to target them right toward your ears. Klipsch places their titanium tweeter inside a flared opening, known as a "horn," which disperses the highs evenly across your listening area in a 90°-wide, 60°-high pattern. With their Series II speakers, Klipsch has redesigned the shape and slope of their famous horn enclosure, so your movie soundtracks and music will sound more "open," with improved dynamics and efficiency. All in all, you can count on powerful, "front row" sound that's crystal-clear at all volume levels.

Cabinet construction

High-tech driver design

The RB-51 IIs also use newly machined, light-yet-rigid Cerametallic woofers with a folded edge to produce smoother mids and tighter bass. The specially treated aluminum in the cones help to dampen unwanted vibrations and distortion, while an integrated dustcap gives them a cleaner look and adds stability. And the rigid, braced cabinets come in a handsome woodgrain vinyl finish.

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Upgraded from the Synergy's to these and they are excellent. They sound fantastic after you put some hours on them and they look just as good. I got a scratch and dent pair and there're totally worth it if you can find them.

Ryan G., Florida

What's in the Box:

  • 2 Black two-way bookshelf loudspeakers
  • 2 Detachable magnetic grilles (attached)
  • 8 Self-adhesive rubber feet
  • Owner's Manual

Product Highlights:

  • frequency response 50-24,000 Hz (±3dB)
  • power handling: up to 75 watts RMS (300 watts peak)
  • sensitivity 92 dB
  • 8-ohm impedance
  • Tractrix® horn with 1" titanium dome tweeter
  • 5-1/4" Cerametallic™ woofer
  • bass-reflex (ported) design
  • black ash woodgrain vinyl finish
  • keyhole slots for easy wall-mounting
  • dual threaded inserts for optional wall-mount brackets
  • 6-1/2"W x 11-3/8"H x 10-15/16"D
  • warranty: 5 years
  • Our 60-day money-back guarantee

Klipsch Reference RB-51 II Reviews

Average Customer Review(s):

(43 Reviews)
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Hands-on research

Features and Specs

Enclosure Bass Reflex
Video Shielded No
Tweeter Type Tractrix Horn
Tweeter Size (inches) 1
Midrange Size (inches) ---
Woofer Size (inches) 5.25
Woofer Composition Cerametallic
Woofer Surround Rubber
Power Range 75
Sensitivity 92 dB
Impedance (Ohms) 8
Frequency Response 50-24k Hz
Connector Type Binding post
Bi-amp Inputs No
Height (inches) 11-3/8
Width (inches) 6-1/2
Depth (inches) 10-15/16
Weight (pounds) 10.45
Mounting Bracket Included Keyhole
Recommended Stand Height (inches) 28-31
Parts Warranty 5 Years
Labor Warranty 5 Years

Product Research

Driver Technology
Enclosure Design
Mounting Options

Driver Technology

Highly-Efficient Design: The Klipsch RB-51 II utilizes a highly efficient design to produce more output using less power & energy for louder sound with less distortion. The RB-51 II is able to fill smaller rooms with outstanding, accurate, non-fatiguing sound that you can listen to for hours.

Tractrix Horn Tweeter: Each Klipsch RB-51 II features a professional-grade 1.0-inch titanium-diaphragm compression driver inside a square Tractrix Horn for smoother high-end response with greater extension, enhanced imaging, and more powerful dynamics. The Tractrix Horns deliver a 90-degree wide by 60-degree high dispersion pattern for a broader sound-stage. Behind each horn lies a 1.0-inch titanium tweeter with a linear travel suspension for open, natural, sound.

Cerametallic Woofer: The 5.25-inch woofer of the RB-51 II features Klipsch's distinctive, copper-colored Cerametallic cones. Made with an anodized aluminum, these cones are strong and dent resistant. The anodizing process converts their inner and outer surfaces to ceramic. The outcome is a rigid cone with superb damping characteristics that will not flex or resonate at frequencies within the woofer's operating range. The 5.25-inch woofer also employs a rubber surround for added durability.

Crossover Network: For signal purity and perfect driver integration, the crossover on the RB-51 II features the finest components and Klipsch custom internal wiring.

Enclosure Design

Bass Reflex Enclosure: The dual 5.25-inch Cerametallic cone woofer and 1.0" titanium diaphragm compression driver are mounted in a bass reflex enclosure which features a single rear-firing port. The RB-51 II's rigid cabinet offers improved internal cross-bracing to minimize panel vibrations that can color sound and a rear-firing port to eliminate turbulence noise. A black metallic finished baffle around the horn mouth and woofer dramatically improve acoustics across the sonic range. The bass reflex enclosure features a MDF cabinet finished with a Black Ash wood-grain vinyl veneer.

Magnetic Grille: The bookshelf loudspeaker features a removable magnetic grille which easily snaps into place over its cast-aluminum front baffle. The speaker can be used with or without its grille in place.


Binding Posts: Each bookshelf loudspeaker is equipped with one pair of sturdy binding posts to ensure a secure connection to many types of speaker cables and connectors. The binding post terminals will accept banana plugs (single only), pin-connectors, spade-connectors, and bare wire.

Mounting Options

Rubber Feet: Each bookshelf speaker comes supplied with eight self-adhesive rubber feet (4 for each speaker) so you can sit the speakers on a stand or shelf securely. The rubber feet add approximately 0.3125" to the height of each speaker. There are also two 1/4"-20 threaded inserts on the back of each loudspeaker for mounting the speaker to third-party stands (sold separately).

Note: The two threaded inserts are spaced 3.0" apart.

Wall Mounting: Each Klipsch Reference bookshelf speaker feature a single keyhole slot on the back of the cabinet for wall-mounting the speaker without any additional wall-mount bracket (mounting screws not supplied).

Placement: The Reference Series bookshelf loudspeakers are designed to perform well in a wide variety of locations but you will get the most out of the speakers by following these simple guidelines.

  • Place the front left and right speakers on shelves or stands with their tweeters at approximately ear height for a seated listener. When used surround sound speakers, they normally perform best when placed slightly higher than ear level.
  • The bookshelf loudspeakers should be equal distance from the floor and the wall behind them. It can also helps to have the left and right speakers at different distances from their nearest side walls. This sort of staggering helps smooth the bass range.

Our Product Research Team

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Q & A

Customer Q&A

1 question already asked

Sorry I don't feel qualified to answer because for us these speakers are part of a 4 speaker system so we can not really isolate just these. What I can say is that these speakers along with a matching center speaker and wireless subwoofer all powered by an Onkyo amplifier produce GREAT sound with no shortage of bass. [ HERBERT  Mar 03, 2015 ]
I use these speakers as fronts in a 7.1 setup. They are satisfactory for mid bass, but suggest a powered sub to compliment them. [ BRIAN  Feb 23, 2015 ]
I have my crossover set to 100hz. I cannot speak specifically to that frequency, but I noticed some clipping at mid to mid hi volume when watching the movie "Gravity". That movie in my opinion really tests the low range of a system because there are a ton of low end thumps and bumps to simulate being in space. I noticed less clipping without a loss in fidelity at that setting. Granted you have a subwoofer. [ Nick  Feb 23, 2015 ]
I am probably not the right person to ask I am using them as part of a 5.1 surround system in my game room. For that they work great! [ MARK  Feb 23, 2015 ]
Annie ...they are absolutely amazing for their size. I would have preferred the RB61 instead but my shelf setup in my office is made of square spaces IKIA fixtures and this was the max hight it would take . It takes a while to get the best sound ( about 100 hrs ) . I recently felt I was missing a bit in the lows ( some purists might argue this point ) but I deciced to setup a 2.1 using a small sub made by klipsch other brand ENERGY , because it's the only one that was front firing and would fit it the office shelf wall . I put the sub in lower left under my desk . The 2 RB 51 are at ear level when sitting in my couch . I am getting a much fuller sound and just love the setup . My Amp is an NAD 3020D that is absolutely amazing. Hope this helps .... Sorry for the long answer :) [ SERGE  Feb 22, 2015 ]
Yes. Response in the low end is quite good.. [ JAMES  Feb 22, 2015 ]
It seems like it to me, but I have the RC-62 II center speaker that might be doing the heavier lifting on the low end. Hard to tell. What I like most about Klipsch speakers (besides the value/performance ratio) is that they are efficient and easy for receivers to drive. That lets you go louder and/or save money and not buy a higher end unit with extra watts. [ NATHANIEL  Feb 22, 2015 ]
honestly, I would say no. I used my pair in conjunction with a sub and as a temporary fix. I upgraded them to the RF 62 II speakers. I have a large room and these RB 51, while great sounding and great quality, just couldnt fill the room as i would like. You have to think, it's a book shelf speaker. They are not going to pound out thundering bass and a have huge room filling sound stage for your home theater. That being said, if you are just wanting high quality speakers for an office, bedroom or other smallish room, they will sound very good and do a respectable job, and better than most book shelf type speakers. A 51/4 inch woofer just doesnt move enough air to faithfully reproduce the low end. [ SEAN B  Feb 22, 2015 ]