In this review, we will be comparing Alpha P5 and R-51M, two Passive Bookshelf speakers from PSB and Klipsch.
Let's have a brief look at the main features
of PSB P5 and Klipsch R-51M first before getting into our more
detailed comparison.
| Key Specs | PSB P5 | Klipsch R-51M |
|---|
| Brand | PSB
Canada · founded 1972 | Klipsch
United States · founded 1946 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 0.75" Hard-Dome | 1" Tractrix Horn |
|---|
| Woofer | 5.25" Polypropylene | 5.25" Copper-spun IMG |
|---|
| Frequency response | 55-21k Hz | 62-21k Hz |
|---|
| Sensitivity | 89 dB | 93 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | 10-90 watts | Up to 85 watts |
|---|
| Weight | 4.61kg / 10.1lbs | 5.00kg / 11lbs |
|---|
| Dimensions (H x W x D) | 11-3/8" x 6-3/4" x 10"
289.0 x 172.0 x 254.0mm | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm |
|---|
What size room are the PSB P5 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* |
PSB P5 |
Klipsch R-51M |
| 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 Alpha P5 and R-51M are 2-way speakers.
PSB P5Klipsch 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 |
PSB P5 |
Klipsch R-51M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
0.75-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 5.25-inch
|
Alpha P5 features a 0.75" anodized aluminum Hard-Dome Tweeter and 1 x 5.25" Polypropylene Woofer with a Crossover frequency at 2500Hz. 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
Alpha P5 has a frequency range of 55-21k Hz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 55Hz, the Alpha P5 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
Alpha P5 and R-51M have the same Impedance of 8 ohms but where they differ is the sensitivity levels. Alpha P5 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 PSB P5, 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.
Alpha P5 can handle a max power of 90 watts RMS, whereas R-51M has a max power handling value of 85 watts RMS, 5 watts less than the Alpha P5.
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
Alpha P5 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.
PSB P5's 5-way post terminals
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Cabinet Type and Port Position
Both Alpha P5 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.
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 PSB P5's and Klipsch R-51M's external dimensions. PSB P5 has external dimensions of 289.0 x 172.0 x 254.0mm (11-3/8 x 6-3/4 x 10inch) whereas Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm (13.3 x 7.0 x 8.4inch).
PSB P5 is 6mm narrower and 49mm shorter than Klipsch R-51M but it is also 39mm deeper.
Below you can see the front view size comparison of PSB P5 and Klipsch R-51M in scale.
Comparison image of PSB P5 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 PSB P5 is approximately 436.9cm2 / 67.7inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The Alpha P5 requires 14% 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 PSB P5 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 PSB P5 weighs 4.61kg / 10.1lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the R-51M 8% heavier than the Alpha P5.
Here is a comparison of how Alpha P5 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 PSB P5?
Here are the items that are included inside the box of Alpha P5:
- 2 Bookshelf loudspeakers
- 2 Grilles
- 8 Self-adhesive rubber feet
- Quick Start Guide
- Warranty Card
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 |
90 watts
vs
85 watts
|
Handle more power from your amplifier |
 Low Frequency Response |
55 Hz
vs
62 Hz
|
Generates deeper bass |
 Height |
289mm
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
436cm2
|
Takes less floor space |
 Price per pair* |
359USD
vs
449USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
PSB Alpha P5 |
Klipsch Reference R-51M |
| Brand |
PSB |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
10-90 watts |
Up to 85 watts |
| Sensitivity |
89 dB |
93 dB |
| Impedance |
8 ohms |
8 ohms |
| Impedance |
4 ohms |
n/a |
| Frequency Response |
55-21k 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 |
0.75" |
1" |
| Tweeter Type |
Hard-Dome |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2500Hz |
1660Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
289.0mm (11.4") |
338.0mm (13.3") |
| Width |
172.0mm (6.8") |
178.0mm (7") |
| Depth |
254.0mm (10") |
215.0mm (8.5") |
| Weight |
4.61kg (10.1lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF, Wood-grain vinyl |
MDF/Wood-grain vinyl |
| Available Colors |
Walnut,Black Ash |
Black |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
28-30" |
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 |
No single best speaker here - they are built to different priorities, and the right one depends on your room, your amplifier and what you listen to.
| Area | Better | Why |
|---|
| Bass | A | PSB P5 digs deeper - 55Hz against 62Hz. A subwoofer would even that out. |
| Amplifier needs | B | Klipsch R-51M is more sensitive (93dB vs 89dB), so it goes louder on the same amplifier. |
| Headroom | evenly matched | Similar power handling (90W vs 85W). |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | depends | Neither adds bi-amping, a sub output or height drivers. PSB P5 sits in a wider range (9 models), so a matched surround system is easier later. |
| Price | B | Klipsch R-51M is cheaper - $359 against $449, about 20% less. |
A PSB P5 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. 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.