In this review, we will be comparing L100 and R-51M, two Passive Bookshelf speakers from Polk Audio and Klipsch.
Let's have a brief look at the main features
of Polk L100 and Klipsch R-51M first before getting into our more
detailed comparison.
| Key Specs | Polk L100 | Klipsch R-51M |
|---|
| Brand | Polk Audio
United States · founded 1972 | Klipsch
United States · founded 1946 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Ring Radiator | 1" Tractrix Horn |
|---|
| Woofer | 5.25" Polypropylene | 5.25" Copper-spun IMG |
|---|
| Frequency response | 57-38k Hz | 62-21k Hz |
|---|
| Sensitivity | 85.5 dB | 93 dB |
|---|
| Impedance | 4 ohms | 8 ohms |
|---|
| Power range | 30-160 watts | Up to 85 watts |
|---|
| Weight | 7.68kg / 16.9lbs | 5.00kg / 11lbs |
|---|
| Dimensions (H x W x D) | 13-11/16" x 7-7/8" x 11-5/16"
348.0 x 201.0 x 288.0mm | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm |
|---|
What size room are the Polk L100 and Klipsch R-51M 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* |
Polk L100 |
Klipsch R-51M |
| Near-field |
Poor |
Average |
| Small Room |
Average |
Good |
| Mid-size Room |
Good |
Average |
| Large Room |
Average |
Poor |
| Very Large Room |
Poor |
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 L100 and R-51M are 2-way speakers.
Polk L100Klipsch 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 |
Polk L100 |
Klipsch R-51M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 5.25-inch
|
L100 features a 1" Ring Radiator Tweeter and 1 x 5.25" Polypropylene Woofer with a Crossover frequency at 2900Hz. 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
L100 has a frequency range of 57-38k Hz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 57Hz, the L100 can go significantly deeper on the low side and provide stronger bass compared to 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
L100 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 L100 can provide this impedance level.
These two speakers also have different sensitivity levels. L100 sensitivity is rated at 85.5 dB and the R-51M's is rated at 93 dB. This 7 dB difference makes the Klipsch R-51M a more sensitive speaker compared to Polk L100, 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.
L100 can handle a max power of 160 watts RMS, whereas R-51M has a max power handling value of 85 watts RMS, 75 watts less than the L100.
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
L100 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.
Polk L100's Post terminals
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Cabinet Type and Port Position
Both L100 and R-51M 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.
Polk L100 Enhanced Power Port Port
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 Polk L100's and Klipsch R-51M's external dimensions. Polk L100 has external dimensions of 348.0 x 201.0 x 288.0mm (13-11/16 x 7-7/8 x 11-5/16inch) whereas Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm (13.3 x 7.0 x 8.4inch).
Polk L100 is clearly the larger of the two speakers. Its body is 23mm wider, 10mm taller and 73mm deeper than Klipsch R-51M.
Below you can see the front view size comparison of Polk L100 and Klipsch R-51M in scale.
Comparison image of Polk L100 and Klipsch R-51M 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 Polk L100 is approximately 578.9cm2 / 89.7inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The L100 requires 51% more surface area than the R-51M which gives it a small disadvantage 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 Polk L100 and Klipsch R-51M 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 Polk L100 weighs 7.68kg / 16.9lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the L100 54% heavier than the R-51M.
Here is a comparison of how L100 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 Polk L100?
Here are the items that are included inside the box of L100:
- 2 Bookshelf loudspeakers
- 2 Grilles
- Cleaning cloth
- Owners Manual
- Online Registration
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
 Max Input Power |
160 watts
vs
85 watts
|
Handle more power from your amplifier |
 Low Frequency Response |
57 Hz
vs
62 Hz
|
Generates deeper bass |
 High Frequency Response |
38k Hz
vs
21k Hz
|
Generates higher frequency |
 Sensitivity |
93 dB
vs
86 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
8 ohms
vs
4 ohms
|
Less selective with amplifiers |
 Height |
338mm
vs
348mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
382cm2
vs
578cm2
|
Takes less floor space |
 Price per pair* |
359USD
vs
999USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Polk Audio Legend L100 |
Klipsch Reference R-51M |
| Brand |
Polk Audio |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
30-160 watts |
Up to 85 watts |
| Sensitivity |
85.5 dB |
93 dB |
| Impedance |
4 ohms |
8 ohms |
| Impedance |
3 ohms |
n/a |
| Frequency Response |
57-38k Hz |
62-21k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
5.25" |
| Woofer Composition |
Polypropylene |
Copper-spun IMG |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Ring Radiator |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2900Hz |
1660Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
348.0mm (13.7") |
338.0mm (13.3") |
| Width |
201.0mm (7.9") |
178.0mm (7") |
| Depth |
288.0mm (11.3") |
215.0mm (8.5") |
| Weight |
7.68kg (16.9lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Wood veneer |
MDF/Wood-grain vinyl |
| Available Colors |
Brown Walnut, Black Ash |
Black |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-28" |
24-28" |
| 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 - Polk L100 costs roughly 2.8x 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 | A | Polk L100 digs deeper - 57Hz against 62Hz. A subwoofer would even that out. |
| Amplifier needs | B | Klipsch R-51M is more sensitive (93dB vs 86dB), 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. |
| Headroom | A | Polk L100 takes more power (160W vs 85W) - more in hand in a big room. |
| Size | depends | Klipsch R-51M is easier to place; Polk L100 is bigger, which usually goes with fuller bass. Your room decides. |
| Price | B | Klipsch R-51M is cheaper - $359 against $999, about 64% less; arguably a different class. |
A Polk L100 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?
Neither runs away with it - they trade advantages. Let the "depends" rows and your own room settle it. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 62Hz anyway, which makes the cheaper Klipsch R-51M much easier to justify. Match it to your room: we rate Polk L100 the better fit for a mid-size room and a large room, and Klipsch R-51M for near-field listening and a small room.
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.