In this review, we will be comparing RTi A1 and R-51M, two Passive Bookshelf speakers from Polk Audio and Klipsch.
Let's have a brief look at the main features
of Polk RTi A1 and Klipsch R-51M first before getting into our more
detailed comparison.
| Key Specs | Polk RTi A1 | Klipsch R-51M |
|---|
| Brand | Polk Audio
United States · founded 1972 | Klipsch
United States · founded 1946 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Dome | 1" Tractrix Horn |
|---|
| Woofer | 5.25" Polymer composite | 5.25" Copper-spun IMG |
|---|
| Frequency response | 60-26k Hz | 62-21k Hz |
|---|
| Sensitivity | 89 dB | 93 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | 20-125 watts | Up to 85 watts |
|---|
| Weight | 5.44kg / 12lbs | 5.00kg / 11lbs |
|---|
| Dimensions (H x W x D) | 12.0" x 7.3" x 11.5"
304.8 x 187.5 x 292.1mm | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm |
|---|
What size room are the Polk RTi A1 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 RTi A1 |
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 RTi A1 and R-51M are 2-way speakers.
Polk RTi A1Klipsch 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 RTi A1 |
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
|
RTi A1 features a 1" silk polymer composite Dome Tweeter and 1 x 5.25" Polymer composite Woofer with a Crossover frequency at 1900Hz. 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
RTi A1 has a frequency range of 60-26k Hz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 60Hz, the RTi A1 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
RTi A1 and R-51M have the same Impedance of 8 ohms but where they differ is the sensitivity levels. RTi A1 sensitivity is rated at 89 dB and the R-51M's is at 93 dB. This 4 dB difference makes the Klipsch R-51M a more sensitive speaker compared to Polk RTi A1, 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.
RTi A1 can handle a max power of 125 watts RMS, whereas R-51M has a max power handling value of 85 watts RMS, 40 watts less than the RTi A1.
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
RTi A1 features Pair of Dual 5-way Binding Posts - Gold-Plated posts which make bi-amping or bi-wiring possible. R-51M has a Single Gold Plated Binding Posts - 5-way which doesn't feature bi-amping/bi-wiring.
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Cabinet Type and Port Position
RTi A1 has a back and front firing port whereas R-51M has a rear firing ports.
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 RTi A1's and Klipsch R-51M's external dimensions. Polk RTi A1 has external dimensions of 304.8 x 187.5 x 292.1mm (12.0 x 7.3 x 11.5inch) 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 9.5mm narrower and 77.1mm less deeper than Polk RTi A1 but it is also 33.2mm taller.
Below you can see the front view size comparison of Polk RTi A1 and Klipsch R-51M in scale.
Comparison image of Polk RTi A1 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 RTi A1 is approximately 547.7cm2 / 84.9inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The RTi A1 requires 43% 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 RTi A1 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 RTi A1 weighs 5.44kg / 12lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the RTi A1 9% heavier than the R-51M.
Here is a comparison of how RTi A1 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 RTi A1?
Here are the items that are included inside the box of RTi A1:
- 2 Cherry bookshelf speakers
- 2 Self-tapping screws
- 8 Self-adhesive rubber feet
- Owner's Manual
- Template
- Online registration sheet
- Polk Audio product brochure
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 |
125 watts
vs
85 watts
|
Handle more power from your amplifier |
 Low Frequency Response |
60 Hz
vs
62 Hz
|
Generates deeper bass |
 High Frequency Response |
26k Hz
vs
21k Hz
|
Generates higher frequency |
 Bi-Amping and Bi-Wiring |
Yes
vs
No
|
Allows bi-amping and bi-wiring connections |
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
304mm
vs
338mm
|
Easier to fit in smaller spaces |
 Sensitivity |
93 dB
vs
89 dB
|
Play louder with same amount of amplification power |
 Base Surface Area |
382cm2
vs
547cm2
|
Takes less floor space |
 Price per pair* |
359USD
vs
382USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Polk Audio RTi A1 |
Klipsch Reference R-51M |
| Brand |
Polk Audio |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-125 watts |
Up to 85 watts |
| Sensitivity |
89 dB |
93 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
60-26k Hz |
62-21k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
5.25" |
| Woofer Composition |
Polymer composite |
Copper-spun IMG |
| Woofer Surround Material |
Butyl rubber |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Dome |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
1900Hz |
1660Hz |
| Firing Direction |
back and front |
rear |
Physical Specs |
|
|
| Height |
304.8mm (12") |
338.0mm (13.3") |
| Width |
187.5mm (7.4") |
178.0mm (7") |
| Depth |
292.1mm (11.5") |
215.0mm (8.5") |
| Weight |
5.44kg (12lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
Real wood veneer |
MDF/Wood-grain vinyl |
| Available Colors |
Black, Cherry |
Black |
| Mounting Bracket |
Keyhole |
No |
| Recommended Stand Height |
28-36" |
24-28" |
| Grille |
n/a |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
Yes |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
A generation apart: Klipsch R-51M is the newer design, against a 2008 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass | evenly matched | Much the same reach (60Hz vs 62Hz). |
| Amplifier needs | B | Klipsch R-51M is more sensitive (93dB vs 89dB), so it goes louder on the same amplifier. |
| Headroom | A | Polk RTi A1 takes more power (125W vs 85W) - more in hand in a big room. |
| Size | depends | Klipsch R-51M is easier to place; Polk RTi A1 is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | A | Polk RTi A1: bi-amping. |
| Price | evenly matched | Much the same money ($382 vs $359 a pair). |
A Polk RTi A1 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?
Polk RTi A1 has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. Match it to your room: we rate Polk RTi A1 the better fit for a mid-size room and a large room, and Klipsch R-51M for near-field listening and a small room. 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.
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.