In this review, we will be comparing S20 and RTi A3, two Passive Bookshelf speakers by Polk Audio.
Let's have a brief look at the main features
of Polk S20 and Polk RTi A3 first before getting into our more
detailed comparison.
| Key Specs | Polk S20 | Polk RTi A3 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Soft-Dome | 1" Dome |
|---|
| Woofer | 6.5" Mica-reinforced polypropylene | 6.5" Polymer composite |
|---|
| Frequency response | 39-40k Hz | 50-26k Hz |
|---|
| Sensitivity | 88 dB | 89 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | 20-125 watts | 20-150 watts |
|---|
| Weight | 7.73kg / 17lbs | 7.26kg / 16lbs |
|---|
| Dimensions (H x W x D) | 14.8" x 8.5" x 13.7"
376.0 x 216.0 x 350.0mm | 14.7" x 8.4" x 14.0"
374.7 x 214.4 x 355.6mm |
|---|
What size room are the Polk S20 and Polk RTi A3 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 S20 |
Polk RTi A3 |
| Near-field |
Poor |
Poor |
| Small Room |
Average |
Average |
| Mid-size Room |
Good |
Good |
| Large Room |
Average |
Average |
| Very Large Room |
Poor |
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.)
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
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Drivers
Both S20 and RTi A3 are 2-way speakers.
Polk S20Polk RTi A3
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
Polk S20 |
Polk RTi A3 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 6.5-inch
|
1 x 6.5-inch
|
S20 features a 1" Terylene Soft-Dome Tweeter and 1 x 6.5" Mica-reinforced polypropylene Woofer with a Crossover frequency at 2500Hz. On the other hand, the RTi A3 features a 1" silk polymer composite Dome Tweeter and 1 x 6.5" Polymer composite Woofer with a Crossover frequency at 2800Hz.
Frequency Response
S20 has a frequency range of 39-40k Hz whereas RTi A3 has a frequency range of 50-26k Hz. With a minimum frequency of 39Hz, the S20 can go significantly deeper on the low side and provide stronger bass compared to the RTi A3's min frequency of 50Hz.
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
S20 and RTi A3 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. S20 sensitivity is rated at 88 dB and the RTi A3's is at 89 dB. This 1 dB difference makes the Polk RTi A3 a more sensitive speaker compared to Polk S20, 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.
RTi A3 can handle a max power of 150 watts RMS, whereas S20 has a max power handling value of 125 watts RMS, 25 watts less than the RTi A3.
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
RTi A3 features Pair of Dual 5-way Binding Posts - Gold-Plated posts which make bi-amping or bi-wiring possible. S20 has a 5-way post which doesn't feature bi-amping/bi-wiring.
Cabinet Type and Port Position
S20 has a rear firing port whereas RTi A3 has a back and front firing ports.
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 Polk S20's and Polk RTi A3's external dimensions. Polk S20 has external dimensions of 376.0 x 216.0 x 350.0mm (14.8 x 8.5 x 13.7inch) whereas Polk RTi A3 has external dimensions of 374.7 x 214.4 x 355.6mm (14.7 x 8.4 x 14.0inch).
Polk RTi A3 is 1.6mm narrower and 1.3mm shorter than Polk S20 but it is also 5.6mm deeper.
Below you can see the front view size comparison of Polk S20 and Polk RTi A3 in scale.
Comparison image of Polk S20 and Polk RTi A3 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 Polk S20 is approximately 756.0cm2 / 117.2inch2 and base area of the Polk RTi A3 is approximately 762.4cm2 / 118.2inch2. The S20 requires 1% less surface area than the RTi A3 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 Polk S20 and Polk RTi A3 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 Polk S20 weighs 7.73kg / 17lbs and the Polk RTi A3 weighs 7.26kg / 16lbs. This makes the S20 6% heavier than the RTi A3.
Here is a comparison of how S20 and RTi A3'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 S20?
Here are the items that are included inside the box of S20:
- 2 Bookshelf loudspeakers
- 2 Grilles (attached)
- 8 Self-adhesive rubber feet
- Owners Manual
- Online Product Registration
What's in the Box of Polk RTi A3?
Here are the items that come with the RTi A3:
- 2 Cherry bookshelf speakers
- 2 Self-tapping screws
- 8 Self-adhesive rubber feet
- Owner's Manual
- Template
- Online registration sheet
- Polk Audio product brochure
 Low Frequency Response |
39 Hz
vs
50 Hz
|
Generates deeper bass |
 High Frequency Response |
40k Hz
vs
26k Hz
|
Generates higher frequency |
 Base Surface Area |
756cm2
vs
762cm2
|
Takes less floor space |
 Max Input Power |
150 watts
vs
125 watts
|
Handle more power from your amplifier |
 Sensitivity |
89 dB
vs
88 dB
|
Play louder with same amount of amplification power |
 Bi-Amping and Bi-Wiring |
Yes
vs
No
|
Allows bi-amping and bi-wiring connections |
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
374mm
vs
376mm
|
Easier to fit in smaller spaces |
| General |
Polk Audio Signature S20 |
Polk Audio RTi A3 |
| Brand |
Polk Audio |
Polk Audio |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-125 watts |
20-150 watts |
| Sensitivity |
88 dB |
89 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
39-40k Hz |
50-26k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
6.5" |
6.5" |
| Woofer Composition |
Mica-reinforced polypropylene |
Polymer composite |
| Woofer Surround Material |
Butyl rubber |
Butyl rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Soft-Dome |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2500Hz |
2800Hz |
| Firing Direction |
rear |
back and front |
Physical Specs |
|
|
| Height |
376.0mm (14.8") |
374.7mm (14.8") |
| Width |
216.0mm (8.5") |
214.4mm (8.4") |
| Depth |
350.0mm (13.8") |
355.6mm (14") |
| Weight |
7.73kg (17lbs) |
7.26kg (16lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
Meddite MDF |
Real wood veneer |
| Available Colors |
Black, Walnut, Brown Walnut |
Black, Cherry |
| Mounting Bracket |
No |
Keyhole |
| Recommended Stand Height |
24-28" |
24-31" |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
Yes |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
A generation apart: Polk S20 is the newer design, against a 2008 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass |
A |
Polk S20 digs deeper - 39Hz against 50Hz. |
| Amplifier needs |
evenly matched |
Similar sensitivity (88dB vs 89dB) - both want much the same power. |
| Headroom |
evenly matched |
Similar power handling (125W vs 150W). |
| Size |
depends |
Similar cabinet size - neither is easier to fit. |
| Expandability |
B |
Polk RTi A3: bi-amping. |
A Polk S20
B Polk RTi A3
depends neither is better in the abstract - it turns on your room, placement 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?
Neither runs away with it - they trade advantages. Let the "depends" rows and your own room settle it. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 50Hz anyway, so judge these on the other rows instead.
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.