Klipsch R-51PM vs Klipsch R-51M Comparison

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Klipsch R-51PM

Powered Bookshelf | 68-21k Hz

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Klipsch R-51M

Passive Bookshelf | 62-21k Hz

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Klipsch R-51PM

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Klipsch R-51M

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Klipsch R-51PM

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Klipsch R-51M

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Klipsch R-51PM vs Klipsch R-51M Speaker Comparison

In this review, we will be comparing R-51PM and R-51M, two Bookshelf speakers by Klipsch. The main difference between these two speakers is that the Klipsch R-51PM is a Powered speaker which means that it has a built-in amplifier inside the speaker body so you don't need an external power amp or an integrated amp whereas the Klipsch R-51M is a Passive speaker so has to be matched with an amplifier to get any sound from it.

Let's have a brief look at the main features of Klipsch R-51PM and Klipsch R-51M first before getting into our more detailed comparison.

Key Specs	Klipsch R-51PM	Klipsch R-51M
Brand	Klipsch United States · founded 1946	Klipsch United States · founded 1946
Design	2-way	2-way
Built-in amplifier	120-watt RMS (240-watt peak)	—
Tweeter	1.0" Tractrix Horn	1" Tractrix Horn
Woofer	5.25" Copper-spun IMG	5.25" Copper-spun IMG
Frequency response	68-21k Hz	62-21k Hz
Sensitivity	—	93 dB
Impedance	—	8 ohms
Power range	—	Up to 85 watts
Max depth / sample rate	24-bit / 96 kHz	—
Bluetooth	Built-in 3.0	—
Weight	4.80kg / 10.6lbs	5.00kg / 11lbs
Dimensions (H x W x D)	13" x 7.0625" x 10.25" 330.2 x 179.4 x 260.3mm	13.3" x 7.0" x 8.4" 338.0 x 178.0 x 215.0mm

R-51PM and R-51M are members of Klipsch's Reference (R) Bookshelf series of speakers. Below you can find the loudspeakers from this series.

Klipsch Reference (R) Bookshelf Series History

Model	Body	Frequency	Watts RMS	Max Depth / Sample Rate	Woofer
Klipsch R-51PM	Bookshelf	68-21k Hz	120-watt	24-bit/96 kHzΩ	1 x 5.25"
Klipsch R-15PM	Bookshelf	62-24k Hz	100-watt	24-bit/96 kHzΩ	1 x 5.25"
Klipsch R-41PM	Bookshelf	76-21k Hz	70-watt	24-bit/96 kHzΩ	1 x 4.0"

The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.

Drivers

Both R-51PM and R-51M are 2-way speakers.

Klipsch R-51PM

Klipsch 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	Klipsch R-51PM	Klipsch R-51M
Driver Setup	2-way	2-way
Tweeter	1.0-inch	1-inch
Midrange	-	-
Woofer	1 x 5.25-inch	1 x 5.25-inch

R-51PM features a 1.0" Aluminum LTS Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1663Hz. 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

R-51PM has a frequency range of 68-21k Hz 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 R-51PM's min frequency of 68Hz.

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

R-51PM

R-51M

Min

Average

Median

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.

Cabinet Type and Port Position

Both R-51PM 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 Klipsch R-51PM's and Klipsch R-51M's external dimensions. Klipsch R-51PM has external dimensions of 330.2 x 179.4 x 260.3mm (13 x 7.0625 x 10.25inch) 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 1.4mm narrower and 45.3mm less deeper than Klipsch R-51PM but it is also 7.8mm taller.

Size, drawn to scale

Both speakers and both views share one scale, so everything here is directly comparable. Hover a box for its dimensions.

One scale for both, standing on the same surface and pushed back to the same wall, so the deeper one visibly sticks out further.

Klipsch R-51PM needs about 22% more floor or shelf area. Klipsch R-51PM is 45mm deeper, so it stands that much further out from the wall.

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-51PM is approximately 467.0cm² / 72.4inch² and base area of the Klipsch R-51M is approximately 382.7cm² / 59.3inch². The R-51PM requires 22% more surface area than the R-51M which gives it a small disadvantage on placement in tight spaces.

What's in the Box of Klipsch R-51PM?

Here are the items that are included inside the box of R-51PM:

Powered speaker (right)
Passive speaker (left)
2 Grilles
68-inch AC power cord
Remote control
2

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

Reasons to choose Klipsch Reference R-51PM over Klipsch Reference R-51M

Speaker Type	Powered vs Passive	Built-in amplifier
Height	330mm vs 338mm	Easier to fit in smaller spaces
3.5mm Connection	Yes vs No	Connection via 3.5mm AUX input
RCA Connection	Yes vs No	Connection via RCA input

Reasons to choose Klipsch Reference R-51M over Klipsch Reference R-51PM

Low Frequency Response	62 Hz vs 68 Hz	Generates deeper bass
Base Surface Area	382cm² vs 467cm²	Takes less floor space
Price per pair*	359USD vs 599USD	costs less (*prices may change depending on the seller, location and time)

Klipsch R-51PM vs Klipsch R-51M Specs Table

Detailed comparison of specifications

General	Klipsch Reference R-51PM	Klipsch Reference R-51M
Brand	Klipsch	Klipsch
Speaker Type	Powered Stereo Speakers	Bookshelf speakers
Sensitivity	n/a	93 dB
Impedance	n/a	8 ohms
Frequency Response	68-21k Hz	62-21k Hz
Amplifier
Watts RMS (Continuous)	120-watt RMS	n/a
Watts Peak (Max)	240-watt RMS	n/a
Max Bit Depth	24-bit	n/a
Max Sample Rate	96 kHz	n/a
Drivers
Woofer Quantity	1	1
Woofer Size	5.25"	5.25"
Woofer Composition	Copper-spun IMG	Copper-spun IMG
Woofer Surround Material	n/a	Rubber
Tweeter Size	1.0"	1"
Tweeter Type	Tractrix Horn	Tractrix Horn
Aimable Tweeter	No	No
Midrange Driver	No	No
Crossover Frequency	1663Hz	1660Hz
Firing Direction	rear	rear
Physical Specs
Height	330.2mm (13")	338.0mm (13.3")
Width	179.4mm (7.1")	178.0mm (7")
Depth	260.3mm (10.2")	215.0mm (8.5")
Weight	4.80kg (10.6lbs)	5.00kg (11lbs)
Enclosure	Bass Reflex	Bass Reflex
Finish	n/a	MDF/Wood-grain vinyl
Available Colors	n/a	Black
Mounting Bracket	No	No
Recommended Stand Height	n/a	24-28"
Grille	Yes	Yes
Moisture Resistancy	No	No
Connections
Biamp Inputs	n/a	No
Aux Inputs	3.5mm, RCA	n/a
USB Port	USB-B	n/a
Phone Input	Yes	n/a
Subwoofer Output	Wired	n/a
Digital Input	Optical	n/a
HDMI Input	No	n/a
Headphone Jack	No	n/a
Ethernet Port	No	n/a
Other
Parts Warranty	1 Year	5 Years
Labor Warranty	1 Year	5 Years

Verdict

Different kinds of product: one is active with its amplifier built in, the other passive and needs one. Judge them on how you want to own the system, not just the specs.

Area	Better	Why
Bass	B	Klipsch R-51M digs deeper - 62Hz against 68Hz. A subwoofer would even that out.
What you buy	depends	Klipsch R-51PM is a complete system - just add a source. Klipsch R-51M also needs an amplifier: more money and another box, but you choose it.
Connections	depends	Klipsch R-51PM has Bluetooth and phono built in. With Klipsch R-51M that all comes from the amplifier you pair it with.
Upgrade path	depends	Klipsch R-51M can be re-amped later and outlive several amplifiers; Klipsch R-51PM ages as one unit.
Size	depends	Similar cabinet size - neither is easier to fit.
Expandability	A	Klipsch R-51PM: a sub output.
Price	B	Klipsch R-51M is cheaper - $359 against $599, about 40% less; arguably a different class. Speakers only - an amplifier narrows that gap.

A Klipsch R-51PM 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-51PM suits you if you want one box, ready to play, with nothing else to buy. Klipsch R-51M suits you if you already have an amplifier, want to choose the electronics, or expect to upgrade in stages. Neither is the better speaker in the abstract. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 68Hz anyway, so judge these on the other rows instead. Think about the whole system, not just the speakers: the roughly $240 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.