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Polk S15 vs Polk S20 Comparison

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Polk S15

Passive Bookshelf | 50-40k Hz

Polk Audio Signature S15
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Polk S20

Passive Bookshelf | 39-40k Hz

Polk Audio Signature S20
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Polk S15 Polk S15
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Polk S20 Polk S20
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Polk S15
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Polk S20
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Polk S15 vs Polk S20 Speaker Comparison

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.

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 )

Polk S20 Key Specs

  • 2-way Design
  • 1" Soft-Dome Tweeter
  • 6.5" Mica-reinforced polypropylene Woofer
  • 39-40k Hz Frequency Response
  • 88 dB Sensitivity
  • Impedance: 8ohms
  • Power Range:20-125watts
  • Weight:7.73kg
  • Dimensions (H x W x D): 376.0" x 8.5" x 13.7"( 376.0 x 216.0 x 350.0mm )

S15 and S20 are members of Polk Audio's Signature S series of speakers. Below you can find the loudspeakers from this series.

Polk Audio Signature S Series History
Model Body Frequency SensitivityImpedance Woofer
Polk S60
  
Floor-standing 26-40k Hz 90 dB8Ω 3 x 6.5"
Polk S20
Bookshelf 39-40k Hz 88 dB8Ω 1 x 6.5"
Polk S15
Bookshelf 50-40k Hz 88 dB8Ω 1 x 5.25"
Polk S10
  
Bookshelf 67-40k Hz 87 dB8Ω 1 x 4"
Polk S55
  
Floor-standing 32-40k Hz 90 dB8Ω 2 x 6.5"
Polk S50
  
Floor-standing 33-40k Hz 89 dB8Ω 2 x 5.25"

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:

Listening Environment* Polk S15 Polk S20
Near-field Average Poor
Small Room Good Average
Mid-size Room Average Good
Large Room Poor Average
Very Large Room Bad Poor

(* 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 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.


**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 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

S15
S20
Min
Average
Max
High Frequency

Bookshelf Speakers

Polk S15
Polk S20
Min
Average
Max

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

S15
S20
Min
Average
Max

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
Polk S15
Polk S20
Min
Average
Max

What's in the Box of Polk S15?

Here are the items that are included inside the box of S15:
  • 2 Bookshelf loudspeakers
  • 2 Grille (attached)
  • 8 Self-adhesive rubber feet
  • Wall-mount template
  • Owners Manual
  • Online Product Registration
  • What's in the Box of Polk S20?

    Here are the items that come with the S20:
  • 2 Bookshelf loudspeakers
  • 2 Grilles (attached)
  • 8 Self-adhesive rubber feet
  • Owners Manual
  • Online Product Registration

  • Reasons to choose Polk Audio Signature S15 over Polk Audio Signature S20
    Mounting Bracket Yes vs No Allows mounting on walls
    Height 304mm vs 376mm Easier to fit in smaller spaces
    Base Surface Area 494cm2 vs 756cm2 Takes less floor space

    Reasons to choose Polk Audio Signature S20 over Polk Audio Signature S15

    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
    Polk S15 vs Polk S20 Specs Table
    Detailed comparison of specifications
    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

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