In this review, we will be comparing R-51M and TSi100, two Passive Bookshelf speakers from Klipsch and Polk Audio.
Let's have a brief look at the main features
of Klipsch R-51M and Polk TSi100 first before getting into our more
detailed comparison.
| Key Specs | Klipsch R-51M | Polk TSi100 |
|---|
| Brand | Klipsch
United States · founded 1946 | Polk Audio
United States · founded 1972 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Tractrix Horn | 1" Dome |
|---|
| Woofer | 5.25" Copper-spun IMG | 5.25" Organic Fiber |
|---|
| Frequency response | 62-21k Hz | 61-24k Hz |
|---|
| Sensitivity | 93 dB | 89 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | Up to 85 watts | 20-100 watts |
|---|
| Weight | 5.00kg / 11lbs | 4.53kg / 10lbs |
|---|
| Dimensions (H x W x D) | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm | 11.0" x 7.0" x 10.1"
279.4 x 177.8 x 259.0mm |
|---|
What size room are the Klipsch R-51M and Polk TSi100 speakers good for?
The size of the room in which you are planning to use these loudspeakers is an important decision
factor. Here we have compared their suitability to various sizes of environments considering their size
and max power parameters:
| Listening Environment* |
Klipsch R-51M |
Polk TSi100 |
| Near-field |
Average |
Average |
| Small Room |
Good |
Good |
| Mid-size Room |
Average |
Average |
| Large Room |
Poor |
Poor |
| Very Large Room |
Bad |
Bad |
(* Approximate Room sizes: Small < 100sq. ft / 9 m2,
Mid-size: 100-220 sq. ft / 9-20 m2, Large 220-400 sq. ft / 20-36 m2, Very Large: >
400 sq. ft / 36 m2.
Average Floor Height: 9" / 2.7m. Typical room sizes differ from country to country, and the actual
listening experience changes depending on floor height, room shape, surface materials, listening
position, speaker locations, etc.)
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
Drivers
Both R-51M and TSi100 are 2-way speakers.
Klipsch R-51MPolk TSi100
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
Klipsch R-51M |
Polk TSi100 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 5.25-inch
|
R-51M features a 1" Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1660Hz. On the other hand, the TSi100 features a 1" Dome Tweeter and 1 x 5.25" Organic Fiber Woofer with a Crossover frequency at 2500Hz.
Frequency Response
R-51M has a frequency range of 62-21k Hz whereas TSi100 has a frequency range of 61-24k Hz. With a minimum frequency of 61Hz, the TSi100 can go slightly deeper then the R-51M's min frequency of 62Hz.
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
R-51M and TSi100 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. R-51M sensitivity is rated at 93 dB and the TSi100's is at 89 dB. This 4 dB difference makes the Klipsch R-51M a more sensitive speaker compared to Polk TSi100, hence will play louder with the same amount of watts.
Sensitivity
Bookshelf Speakers
Power Range
Power
range is the range of input power in watts RMS that a loudspeaker is designed to handle. Staying
within that range gives nominal performance; driving the speaker beyond its maximum wattage can damage it.
TSi100 can handle a max power of 100 watts RMS, whereas R-51M has a max power handling value of 85 watts RMS, 15 watts less than the TSi100.
Note that higher power handling does not make a speaker louder: that depends mainly on
sensitivity and impedance. The calculator below shows how loud each of these actually plays
on a real amplifier.
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
R-51M features Pair of 5-way Binding Posts - Gold-Plated type posts and TSi100 has a Pair of 5-way Binding Posts - Gold-Plated type posts. None of these speakers feature bi-amping/bi-wiring.
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Cabinet Type and Port Position
Both R-51M and TSi100 have rear firing ports. Rear ported speakers generally need more room between the backside of the speaker and the wall compared to sealed and front/bottom ported speakers. Placing the speakers too close to the walls may cause the bass to sound boomy.
If you are limited in space and can't get the speakers away from the backwall, check our Speakers with Front Firing Ports page.
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 Klipsch R-51M's and Polk TSi100's external dimensions. Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm (13.3 x 7.0 x 8.4inch) whereas Polk TSi100 has external dimensions of 279.4 x 177.8 x 259.0mm (11.0 x 7.0 x 10.1inch).
Polk TSi100 is 0.19999999999999mm narrower and 58.6mm shorter than Klipsch R-51M but it is also 44mm deeper.
Below you can see the front view size comparison of Klipsch R-51M and Polk TSi100 in scale.
Comparison image of Klipsch R-51M and Polk TSi100 Size and External Dimensions
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 Klipsch R-51M is approximately 382.7cm2 / 59.3inch2 and base area of the Polk TSi100 is approximately 460.5cm2 / 71.4inch2. The R-51M requires 17% less surface area than the TSi100 which gives it a small advantage on placement in tight spaces.
Here is another comparison that shows both speakers on a BDI Octave Media Cabinet, next to a standard size amplifier and turntable in scale:
Size Comparison image of Klipsch R-51M and Polk TSi100 on a Media Console
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 Klipsch R-51M weighs 5.00kg / 11lbs and the Polk TSi100 weighs 4.53kg / 10lbs. This makes the R-51M 10% heavier than the TSi100.
Here is a comparison of how R-51M and TSi100's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of Klipsch R-51M?
Here are the items that are included inside the box of R-51M:
- 2 Bookshelf loudspeakers
- 2 Grilles (installed)
- 8 Self-adhesive rubber feet
- Quick Setup Guide
- Important Safety Instructions
- Warranty Information
What's in the Box of Polk TSi100?
Here are the items that come with the TSi100:
- 2 Black bookshelf speakers
- Detachable cloth grille (installed)
- 8 Self-adhesive rubber feet
- Owner's Manual
- Wall-Mount template
- Online registration sheet
- Polk Audio product brochure
 Sensitivity |
93 dB
vs
89 dB
|
Play louder with same amount of amplification power |
 Base Surface Area |
382cm2
vs
460cm2
|
Takes less floor space |
 Max Input Power |
100 watts
vs
85 watts
|
Handle more power from your amplifier |
 Low Frequency Response |
61 Hz
vs
62 Hz
|
Generates deeper bass |
 High Frequency Response |
24k Hz
vs
21k Hz
|
Generates higher frequency |
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
279mm
vs
338mm
|
Easier to fit in smaller spaces |
 Price per pair* |
149USD
vs
359USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Klipsch Reference R-51M |
Polk Audio TSi100 |
| Brand |
Klipsch |
Polk Audio |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
Up to 85 watts |
20-100 watts |
| Sensitivity |
93 dB |
89 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
62-21k Hz |
61-24k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
5.25" |
| Woofer Composition |
Copper-spun IMG |
Organic Fiber |
| Woofer Surround Material |
Rubber |
Butyl Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Tractrix Horn |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
1660Hz |
2500Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
338.0mm (13.3") |
279.4mm (11") |
| Width |
178.0mm (7") |
177.8mm (7") |
| Depth |
215.0mm (8.5") |
259.0mm (10.2") |
| Weight |
5.00kg (11lbs) |
4.53kg (10lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Wood-grain vinyl |
Wood-grain vinyl |
| Available Colors |
Black |
Black, Cherry |
| Mounting Bracket |
No |
Keyhole |
| Recommended Stand Height |
24-28" |
16-30" |
| Grille |
Yes |
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 - Klipsch R-51M costs roughly 2.4x what Polk TSi100 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 | evenly matched | Much the same reach (62Hz vs 61Hz). |
| Amplifier needs | A | Klipsch R-51M is more sensitive (93dB vs 89dB), so it goes louder on the same amplifier. |
| Headroom | evenly matched | Similar power handling (85W vs 100W). |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Price | B | Polk TSi100 is cheaper - $149 against $359, about 58% less; arguably a different class. |
A Klipsch R-51M B Polk TSi100
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 ahead, but only on 1 of the measured areas, and it costs about 141% more. That is a lot of money for a narrow margin on paper - Polk TSi100 looks like the sensible buy unless something else about the Klipsch R-51M appeals to you. If your amplifier is modest, vintage or valve-based, Klipsch R-51M is the safer partner - the other will want more current or more watts to sound its best. Think about the whole system, not just the speakers: the roughly $210 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
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.