In this review, we will be comparing A120 and R-51M, two Passive Bookshelf speakers from JBL and Klipsch.
Let's have a brief look at the main features
of JBL A120 and Klipsch R-51M first before getting into our more
detailed comparison.
| Key Specs | JBL A120 | Klipsch R-51M |
|---|
| Brand | JBL
United States · founded 1946 | Klipsch
United States · founded 1946 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Hard-Dome | 1" Tractrix Horn |
|---|
| Woofer | 4.5" Polycellulose | 5.25" Copper-spun IMG |
|---|
| Frequency response | 60-40k Hz | 62-21k Hz |
|---|
| Sensitivity | 86 dB | 93 dB |
|---|
| Impedance | 6 ohms | 8 ohms |
|---|
| Power range | 20-125 watts | Up to 85 watts |
|---|
| Weight | 3.82kg / 8.4lbs | 5.00kg / 11lbs |
|---|
| Dimensions (H x W x D) | 11-1/4" x 6-3/4" x 7-7/16"
286.0 x 172.0 x 189.0mm | 13.3" x 7.0" x 8.4"
338.0 x 178.0 x 215.0mm |
|---|
What size room are the JBL A120 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* |
JBL A120 |
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 A120 and R-51M are 2-way speakers.
JBL A120Klipsch 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 |
JBL A120 |
Klipsch R-51M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 4.5-inch
|
1 x 5.25-inch
|
A120 features a 1" aluminum Hard-Dome Tweeter and 1 x 4.5" Polycellulose Woofer. 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
A120 has a frequency range of 60-40k Hz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 60Hz, the A120 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
A120 is a 6 ohms speaker compared to the R-51M which has a nominal impedance of 8 ohms.
These two speakers also have different sensitivity levels. A120 sensitivity is rated at 86 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 JBL A120, 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.
A120 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 A120.
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
A120 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.
JBL A120's 5-way post terminals
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Cabinet Type and Port Position
Both A120 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 JBL A120's and Klipsch R-51M's external dimensions. JBL A120 has external dimensions of 286.0 x 172.0 x 189.0mm (11-1/4 x 6-3/4 x 7-7/16inch) whereas Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm (13.3 x 7.0 x 8.4inch).
Klipsch R-51M is clearly the larger of the two speakers. Its body is 6mm wider, 52mm taller and 26mm deeper than JBL A120.
Below you can see the front view size comparison of JBL A120 and Klipsch R-51M in scale.
Comparison image of JBL A120 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 JBL A120 is approximately 325.1cm2 / 50.4inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The A120 requires 15% less surface area than the R-51M 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 JBL A120 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 JBL A120 weighs 3.82kg / 8.4lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the R-51M 31% heavier than the A120.
Here is a comparison of how A120 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 JBL A120?
Here are the items that are included inside the box of A120:
- 2 Bookshelf loudspeakers
- 2 Grilles
- 2 Foam plugs
- 4 Brackets
- 8 Rubber feet
- 8 Screws (M6 x 8mm)
- Owner-feets Manual
- 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 |
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 |
40k Hz
vs
21k Hz
|
Generates higher frequency |
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
286mm
vs
338mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
325cm2
vs
382cm2
|
Takes less floor space |
 Price per pair* |
250USD
vs
359USD
|
costs less (*prices may change depending on the seller, location and time) |
 Sensitivity |
93 dB
vs
86 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
8 ohms
vs
6 ohms
|
Less selective with amplifiers |
|
Woofer Size |
5.25 inches
vs
4.5 inches
|
Larger woofer |
| General |
JBL Stage A120 |
Klipsch Reference R-51M |
| Brand |
JBL |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-125 watts |
Up to 85 watts |
| Sensitivity |
86 dB |
93 dB |
| Impedance |
6 ohms |
8 ohms |
| Frequency Response |
60-40k Hz |
62-21k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
4.5" |
5.25" |
| Woofer Composition |
Polycellulose |
Copper-spun IMG |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Hard-Dome |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
1660Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
286.0mm (11.3") |
338.0mm (13.3") |
| Width |
172.0mm (6.8") |
178.0mm (7") |
| Depth |
189.0mm (7.4") |
215.0mm (8.5") |
| Weight |
3.82kg (8.4lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF, Vinyl |
MDF/Wood-grain vinyl |
| Available Colors |
Black |
Black |
| Mounting Bracket |
Keyholes w/ bracket |
No |
| Recommended Stand Height |
26-28" |
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 |
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 | evenly matched | Much the same reach (60Hz vs 62Hz). |
| 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. |
| Headroom | A | JBL A120 takes more power (125W vs 85W) - more in hand in a big room. |
| Size | depends | JBL A120 is easier to place; Klipsch R-51M is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | Neither adds bi-amping, a sub output or height drivers. JBL A120 sits in a wider range (10 models), so a matched surround system is easier later. |
| Price | A | JBL A120 is cheaper - $250 against $359, about 30% less. |
A JBL A120 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-51M is ahead, but only on 1 of the measured areas, and it costs about 44% more. That is a lot of money for a narrow margin on paper - JBL A120 looks like the sensible buy unless something else about the Klipsch R-51M appeals to you. Match it to your room: we rate JBL A120 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.