In this review, we will be comparing S15 and S20, two Passive Bookshelf speakers by Polk Audio Let's have a brief look at the main features
of Polk S15 and Polk S20 first before getting into our more
detailed comparison.
S15 and S20 are members of Polk Audio's Signature S series of speakers. Below you can find the loudspeakers from this series.
What size room are the Polk S15 and Polk S20 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:
In the following sections, we will get into more detail in order to better understand how the Polk S15 and Polk S20 compare and hopefully end up with enough arguments to decide which one of these loudspeakers is the better choice for you.
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Drivers
Both S15 and S20 are 2-way speakers.
| Driver |
Polk S15 |
Polk S20 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 6.5-inch
|
S15 features a 1" Terylene Dome Tweeter and 1 x 5.25" Mica-reinforced polypropylene Woofer with a Crossover frequency at 2500Hz. On the other hand, the S20 features a 1" Terylene Soft-Dome Tweeter and 1 x 6.5" Mica-reinforced polypropylene Woofer with a Crossover frequency at 2500Hz.
Frequency Response
S15 has a frequency range of 50-40k Hz whereas S20 has a frequency range of 39-40k Hz. With a minimum frequency of 39Hz, the S20 can go significantly deeper on the low side and provide stronger bass compared to the S15's min frequency of 50Hz.
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
S15 and S20 have the same Impedance of 8 ohms and their sensitivity is also same at 88 dB.
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.
S15 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 S20.
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
S15 features 5-way post type posts and S20 has a 5-way post type posts. None of these speakers feature bi-amping/bi-wiring.
Cabinet Type and Port Position
Both S15 and S20 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 Polk S15's and Polk S20's external dimensions. Polk S15 has external dimensions of 304.8 x 190.0 x 260.4mm ( 12.0 x 7.4 x 10.2inch) whereas Polk S20 has external dimensions of 376.0 x 216.0 x 350.0mm ( 14.8 x 8.5 x 13.7inch) .
Polk S20 is clearly the larger of the two speakers. Its body is 26mm wider, 71.2mm taller and 89.6mm deeper than Polk S15.
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 Polk S15 is approximately 494.8cm2 / 76.7inch2 and base area of the Polk S20 is approximately 756.0cm2 / 117.2inch2. The S15 requires 35% less surface area than the S20 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 Polk S15 weighs 5.90kg / 13lbs and the Polk S20 weighs 7.73kg / 17lbs. This makes the S20 31% heavier than the S15.
Here is a comparison of how S15 and S20's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of Polk S15?
Here are the items that are included inside the box of S15:
2 Bookshelf loudspeakers2 Grille (attached)8 Self-adhesive rubber feetWall-mount templateOwners ManualOnline Product Registration
What's in the Box of Polk S20?
Here are the items that come with the S20:
2 Bookshelf loudspeakers2 Grilles (attached)8 Self-adhesive rubber feetOwners ManualOnline Product Registration
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
304mm
vs
376mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
494cm2 (190x260mm)
vs
756cm2 (216x350mm)
|
Takes less floor space |
 Max Input Power |
125 watts
vs
100 watts
|
Handle more power from your amplifier |
 Woofer Size |
6.5 inches
vs
5.25 inches
|
Larger woofer |
| Low Frequency Response |
39 Hz
vs
50 Hz
|
Generates deeper bass |
| General |
Polk Audio Signature S15 |
Polk Audio Signature S20 |
| Brand |
Polk Audio |
Polk Audio |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-100 watts |
20-125 watts |
| Sensitivity |
88 dB |
88 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
50-40k Hz |
39-40k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
6.5" |
| Woofer Composition |
Mica-reinforced polypropylene |
Mica-reinforced polypropylene |
| Woofer Surround Material |
Butyl rubber |
Butyl rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Dome |
Soft-Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2500Hz |
2500Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
304.8mm (12") |
376.0mm (14.8") |
| Width |
190.0mm (7.5") |
216.0mm (8.5") |
| Depth |
260.4mm (10.3") |
350.0mm (13.8") |
| Weight |
5.90kg (13lbs) |
7.73kg (17lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
Meddite MDF |
Meddite MDF |
| Available Colors |
Black, Walnut, Brown Walnut |
Black, Walnut, Brown Walnut |
| Mounting Bracket |
Keyhole |
No |
| Recommended Stand Height |
24-30" |
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 |