In this review, we will be comparing A120 and S15, two Passive Bookshelf speakers from JBL and Polk Audio.
Let's have a brief look at the main features
of JBL A120 and Polk S15 first before getting into our more
detailed comparison.
| Key Specs | JBL A120 | Polk S15 |
|---|
| Brand | JBL
United States · founded 1946 | Polk Audio
United States · founded 1972 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Hard-Dome | 1" Dome |
|---|
| Woofer | 4.5" Polycellulose | 5.25" Mica-reinforced polypropylene |
|---|
| Frequency response | 60-40k Hz | 50-40k Hz |
|---|
| Sensitivity | 86 dB | 88 dB |
|---|
| Impedance | 6 ohms | 8 ohms |
|---|
| Power range | 20-125 watts | 20-100 watts |
|---|
| Weight | 3.82kg / 8.4lbs | 5.90kg / 13lbs |
|---|
| 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 | 12.0" x 7.4" x 10.2"
304.8 x 190.0 x 260.4mm |
|---|
What size room are the JBL A120 and Polk S15 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 |
Polk S15 |
| 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 S15 are 2-way speakers.
JBL A120Polk S15
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 |
Polk S15 |
|
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 S15 features a 1" Terylene Dome Tweeter and 1 x 5.25" Mica-reinforced polypropylene Woofer with a Crossover frequency at 2500Hz.
Frequency Response
A120 has a frequency range of 60-40k Hz whereas S15 has a frequency range of 50-40k Hz. With a minimum frequency of 50Hz, the S15 can go significantly deeper on the low side and provide stronger bass compared to the A120's min frequency of 60Hz.
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 S15 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 S15's is rated at 88 dB. This 2 dB difference makes the Polk S15 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 S15 has a max power handling value of 100 watts RMS, 25 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 Pair of Binding Posts - Gold Plated type posts and S15 has a Pair of Binding Posts - Gold Plated type posts. None of these speakers feature bi-amping/bi-wiring.
JBL A120's 5-way post terminals
Cabinet Type and Port Position
Both A120 and S15 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 Polk S15'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 Polk S15 has external dimensions of 304.8 x 190.0 x 260.4mm (12.0 x 7.4 x 10.2inch).
Polk S15 is clearly the larger of the two speakers. Its body is 18mm wider, 18.8mm taller and 71.4mm deeper than JBL A120.
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.
Polk S15 needs about 52% more floor or shelf area. Polk S15 is 71mm deeper, so it stands that much further out from the wall. Polk S15 is 19mm taller.
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 Polk S15 is approximately 494.8cm2 / 76.7inch2. The A120 requires 34% less surface area than the S15 which gives it a small advantage on placement in tight spaces.
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 Polk S15 weighs 5.90kg / 13lbs. This makes the S15 54% heavier than the A120.
Here is a comparison of how A120 and S15'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 Polk S15?
Here are the items that come with the S15:
- 2 Bookshelf loudspeakers
- 2 Grille (attached)
- 8 Self-adhesive rubber feet
- Wall-mount template
- Owners Manual
- Online Product Registration
 Max Input Power |
125 watts
vs
100 watts
|
Handle more power from your amplifier |
 Height |
286mm
vs
304mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
325cm2
vs
494cm2
|
Takes less floor space |
 Price per pair* |
250USD
vs
259USD
|
costs less (*prices may change depending on the seller, location and time) |
 Sensitivity |
88 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 |
|
Low Frequency Response |
50 Hz
vs
60 Hz
|
Generates deeper bass |
| General |
JBL Stage A120 |
Polk Audio Signature S15 |
| Brand |
JBL |
Polk Audio |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-125 watts |
20-100 watts |
| Sensitivity |
86 dB |
88 dB |
| Impedance |
6 ohms |
8 ohms |
| Frequency Response |
60-40k Hz |
50-40k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
4.5" |
5.25" |
| Woofer Composition |
Polycellulose |
Mica-reinforced polypropylene |
| Woofer Surround Material |
Rubber |
Butyl rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Hard-Dome |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
2500Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
286.0mm (11.3") |
304.8mm (12") |
| Width |
172.0mm (6.8") |
190.0mm (7.5") |
| Depth |
189.0mm (7.4") |
260.4mm (10.3") |
| Weight |
3.82kg (8.4lbs) |
5.90kg (13lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF, Vinyl |
Meddite MDF |
| Available Colors |
Black |
Black, Walnut, Brown Walnut |
| Mounting Bracket |
Keyholes w/ bracket |
Keyhole |
| Recommended Stand Height |
26-28" |
24-30" |
| 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 | B | Polk S15 digs deeper - 50Hz against 60Hz. |
| Amplifier needs | B | Polk S15 is more sensitive (88dB vs 86dB), so it goes louder on the same amplifier. |
| Amplifier match | B | Polk S15 is the easier load at 8 ohms. |
| Headroom | A | JBL A120 takes more power (125W vs 100W) - more in hand in a big room. |
| Size | depends | JBL A120 is easier to place; Polk S15 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 | evenly matched | Much the same money ($250 vs $259 a pair). |
A JBL A120 B Polk S15
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 S15 has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 60Hz anyway, so judge these on the other rows instead. Match it to your room: we rate JBL A120 the better fit for a mid-size room and a large room, and Polk S15 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.