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.
JBL A120 Key Specs
- 2-way Design
- 1" Hard-Dome Tweeter
- 4.5" Polycellulose Woofer
- 60-40k Hz Frequency Response
- 86 dB Sensitivity
- Impedance: 6ohms
- Power Range:20-125watts
- Weight:3.82kg
- Dimensions (H x W x D): 286.0" x 6-3/4" x 7-7/16"( 286.0 x 172.0 x 189.0mm )
Polk S15 Key Specs
- 2-way Design
- 1" Dome Tweeter
- 5.25" Mica-reinforced polypropylene Woofer
- 50-40k Hz Frequency Response
- 88 dB Sensitivity
- Impedance: 8ohms
- Power Range:20-100watts
- Weight:5.90kg
- Dimensions (H x W x D): 304.8" 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.)
In the following sections, we will get into more detail in order to better understand how the JBL A120 and Polk S15 compare and hopefully end up with enough arguments to decide which one of these loudspeakers is the better choice for you.
**This post contains affiliate links, and I will be compensated if you make a purchase after clicking
through my links. As an Amazon Associate I earn from qualifying purchases.
Drivers
Both A120 and S15 are 2-way speakers.
| 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.
Below graphs depict how these two speakers compare with the max, min and average values of the Min and Max Frequencies of other speakers in the Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
High Frequency
Bookshelf Speakers
None of these speakers achieves full range experience which is commonly agreed as 20Hz-20kHz. In order to achieve lower lows / deeper bass, we recommend you pair these with a subwoofer. 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. While using
an amplifier within this range ensures the nominal performance , inputting a power that is higher than the
max wattage can result in a damaged speaker.
A120 can handle a max power of 125 watts RMS from the amp the whereas S15 has a max power handling value of 100 watts RMS, 25 watts less than the A120.
Keep in mind that a higher max power handling value doesn't necessarily make that a louder speaker
compared to a lower max handling speaker. Loudness or the sound level is also impacted by parameters
such as Impedance, sensitivity and system efficiencies.
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
Size of a speaker can sometimes become 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.
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 loudspeakers2 Grilles2 Foam plugs4 Brackets8 Rubber feet8 Screws (M6 x 8mm)Owner-feets ManualWarranty Card
What's in the Box of Polk S15?
Here are the items that come with the S15:
2 Bookshelf loudspeakers2 Grille (attached)8 Self-adhesive rubber feetWall-mount templateOwners ManualOnline 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 |