In this review, we will be comparing Sib-T and R-51M, two Passive Bookshelf speakers from Focal and Klipsch.
Let's have a brief look at the main features
of Focal Sib-T and Klipsch R-51M first before getting into our more
detailed comparison.
| Key Specs | Focal Sib-T | Klipsch R-51M |
|---|
| Brand | Focal
France · founded 1979 | Klipsch
United States · founded 1946 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | .75" Dome | 1" Tractrix Horn |
|---|
| Woofer | 5.125" Polyflex | 5.25" Copper-spun IMG |
|---|
| Frequency response | 80-20kHz | 62-21k Hz |
|---|
| Sensitivity | 90 dB | 93 dB |
|---|
| Impedance | 4 ohms | 8 ohms |
|---|
| Power range | — | Up to 85 watts |
|---|
| Weight | 2.60kg / 5.7lbs | 5.00kg / 11lbs |
|---|
| Dimensions (H x W x D) | 2-1/2" x 5-5/8" x 6-11/16"
64.0 x 143.0 x 170.0mm | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm |
|---|
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
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Drivers
Both Sib-T and R-51M are 2-way speakers.
Focal Sib-TKlipsch R-51M
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
Focal Sib-T |
Klipsch R-51M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
.75-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.125-inch
|
1 x 5.25-inch
|
Sib-T features a .75" Dome Tweeter and 1 x 5.125" Polyflex Woofer. On the other hand, the R-51M features a 1" Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1660Hz.
Frequency Response
Sib-T has a frequency range of 80-20kHz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 62Hz, the R-51M can go significantly deeper on the low side and provide stronger bass compared to the Sib-T's min frequency of 80Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
Neither pair reaches down to 20Hz, the usual definition of full-range, which is normal for speakers of this size. If you want the bottom octave for movies or bass-heavy music, add a subwoofer to whichever you choose. Visit our Powered Subwoofers section to find out more about the available options.
Impedance and Sensitivity
Sib-T is a 4 ohms speaker compared to the R-51M which has a nominal impedance of 8 ohms. Lower impedance speakers, especially the ones that are rated at 4 ohms may put more pressure on the amplifier unit especially when played at high volume levels, so make sure the amp you pair with the Sib-T can provide this impedance level.
These two speakers also have different sensitivity levels. Sib-T sensitivity is rated at 90 dB and the R-51M's is rated at 93 dB. This 3 dB difference makes the Klipsch R-51M a more sensitive speaker compared to Focal Sib-T, hence will play louder with the same amount of watts.
Sensitivity
Bookshelf Speakers
Which plays louder on your amplifier?
Starting with a popular amplifier — change it to the one you own, or any you are
considering, and watch both numbers move.
Input Type and Bi-Amping / Bi-Wiring
Sib-T features Single Gold Plated Binding Posts - 5-way type posts and R-51M has a Single Gold Plated Binding Posts - 5-way type posts. None of these speakers feature bi-amping/bi-wiring.
Focal Sib-T's Spring posts terminals
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Physical Specs
The size of a speaker can sometimes be an important decision factor due to space constraints or in some cases purely for esthetic reasons. In this section, we are going to compare Focal Sib-T's and Klipsch R-51M's external dimensions. Focal Sib-T has external dimensions of 64.0 x 143.0 x 170.0mm (2-1/2 x 5-5/8 x 6-11/16inch) whereas Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm (13.3 x 7.0 x 8.4inch).
Klipsch R-51M is clearly the larger of the two speakers. Its body is 35mm wider, 274mm taller and 45mm deeper than Focal Sib-T.
Base Surface Area Comparison
Base surface area of a loudspeaker may become a determining factor when the space in your room or desk is limited.
The base surface area of the Focal Sib-T is approximately 243.1cm2 / 37.7inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The Sib-T requires 36% less surface area than the R-51M which gives it a small advantage on placement in tight spaces.
Weight Comparison The weight of a loudspeaker can become an important factor if you need to move and reposition the unit often. Weight of a speaker can also "sometimes" be an indicator of the rigidity of the enclosure and the quality of the internal components used. The Focal Sib-T weighs 2.60kg / 5.7lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the R-51M 92% heavier than the Sib-T.
Here is a comparison of how Sib-T and R-51M's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of Focal Sib-T?
Here are the items that are included inside the box of Sib-T:
- One 100V/4-ohm commercial speaker
- Adjustable mounting bracket (installed)
- 3 Drywall anchors w/ 2 screws
- 5mm Allen key (attached to mounting bracket)
- User manual
What's in the Box of Klipsch R-51M?
Here are the items that come with the R-51M:
- 2 Bookshelf loudspeakers
- 2 Grilles (installed)
- 8 Self-adhesive rubber feet
- Quick Setup Guide
- Important Safety Instructions
- Warranty Information
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
64mm
vs
338mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
243cm2
vs
382cm2
|
Takes less floor space |
 Sensitivity |
93 dB
vs
90 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
8 ohms
vs
4 ohms
|
Less selective with amplifiers |
 Woofer Size |
5.25 inches
vs
5.125 inches
|
Larger woofer |
|
Low Frequency Response |
62 Hz
vs
80 Hz
|
Generates deeper bass |
 High Frequency Response |
21k Hz
vs
20k Hz
|
Generates higher frequency |
 Price per pair* |
359USD
vs
698USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Focal Sib-T |
Klipsch Reference R-51M |
| Brand |
Focal |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Sensitivity |
90 dB |
93 dB |
| Impedance |
4 ohms |
8 ohms |
| Frequency Response |
80-20kHz |
62-21k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.125" |
5.25" |
| Woofer Composition |
Polyflex |
Copper-spun IMG |
| Woofer Surround Material |
n/a |
Rubber |
| Tweeter Size |
.75" |
1" |
| Tweeter Type |
Dome |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
1660Hz |
| Firing Direction |
n/a |
rear |
Physical Specs |
|
|
| Height |
64.0mm (2.5") |
338.0mm (13.3") |
| Width |
143.0mm (5.6") |
178.0mm (7") |
| Depth |
170.0mm (6.7") |
215.0mm (8.5") |
| Weight |
2.60kg (5.7lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
Plastic |
MDF/Wood-grain vinyl |
| Available Colors |
White |
Black |
| Mounting Bracket |
Yes |
No |
| Recommended Stand Height |
2-1/2" |
24-28" |
| Grille |
n/a |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
These sit in different price classes - Focal Sib-T costs roughly 1.9x what Klipsch R-51M does. Expect it to lead on paper; the question is whether the gap is audible enough in your room to be worth it.
| Area | Better | Why |
|---|
| Bass | B | Klipsch R-51M digs deeper - 62Hz against 80Hz. |
| Amplifier needs | B | Klipsch R-51M is more sensitive (93dB vs 90dB), so it goes louder on the same amplifier. |
| Amplifier match | B | Klipsch R-51M is the easier load at 8 ohms; the other is 4 ohms and wants an amplifier rated for it. |
| Size | depends | Focal Sib-T is easier to place; Klipsch R-51M is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | Neither adds bi-amping, a sub output or height drivers. Klipsch R-51M sits in a wider range (5 models), so a matched surround system is easier later. |
| Price | B | Klipsch R-51M is cheaper - $359 against $698, about 49% less; arguably a different class. |
A Focal Sib-T B Klipsch R-51M
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Klipsch R-51M is the easier recommendation: it leads on most of the measured areas and costs less. Take Focal Sib-T if its size, looks or fit in your room suit you better. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 80Hz anyway, so judge these on the other rows instead. In a large or open-plan room, Klipsch R-51M has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, Focal Sib-T is the easier speaker to get right.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.