Polk S20 vs Cambridge SX-50 Comparison

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Polk S20

Passive Bookshelf | 39-40k Hz

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Cambridge SX-50

Passive Bookshelf | 50-22k Hz

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Polk S20

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Cambridge SX-50

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Polk S20

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Cambridge SX-50

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Polk S20 vs Cambridge SX-50 Speaker Comparison

In this review, we will be comparing S20 and SX-50, two Passive Bookshelf speakers from Polk Audio and Cambridge Audio.

Let's have a brief look at the main features of Polk S20 and Cambridge SX-50 first before getting into our more detailed comparison.

Key Specs	Polk S20	Cambridge SX-50
Brand	Polk Audio United States · founded 1972	Cambridge Audio United Kingdom · founded 1968
Design	2-way	2-way
Tweeter	1" Soft-Dome	1" Dome
Woofer	6.5" Mica-reinforced polypropylene	5.25" Treated paper
Frequency response	39-40k Hz	50-22k Hz
Sensitivity	88 dB	90 dB
Impedance	8 ohms	8 ohms
Power range	20-125 watts	10-100 watts
Weight	7.73kg / 17lbs	3.00kg / 6.6lbs
Dimensions (H x W x D)	14.8" x 8.5" x 13.7" 376.0 x 216.0 x 350.0mm	8.8" x 6.3" x 9.4" 225.0 x 161.0 x 240.0mm

What size room are the Polk S20 and Cambridge SX-50 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	Cambridge SX-50
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 S20 and SX-50 are 2-way speakers.

Polk S20

Cambridge SX-50

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	Cambridge SX-50
Driver Setup	2-way	2-way
Tweeter	1-inch	1-inch
Midrange	-	-
Woofer	1 x 6.5-inch	1 x 5.25-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 SX-50 features a 1" Silk Dome Tweeter and 1 x 5.25" Treated paper Woofer.

Frequency Response

S20 has a frequency range of 39-40k Hz whereas SX-50 has a frequency range of 50-22k Hz. With a minimum frequency of 39Hz, the S20 can go significantly deeper on the low side and provide stronger bass compared to the SX-50'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

S20

SX-50

Min

Average

Median

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 SX-50 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. S20 sensitivity is rated at 88 dB and the SX-50's is at 90 dB. This 2 dB difference makes the Cambridge SX-50 a more sensitive speaker compared to Polk S20, hence will play louder with the same amount of watts.

Sensitivity

Bookshelf Speakers

S20

SX-50

Min

Average

Median

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.

S20 can handle a max power of 125 watts RMS, whereas SX-50 has a max power handling value of 100 watts RMS, 25 watts less than the S20.

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.

Amplifier - change this

Distance

Playing as

Polk S20

Cambridge SX-50

Input Type and Bi-Amping / Bi-Wiring

S20 features 5-way post type posts and SX-50 has a 5-way post type posts. None of these speakers feature bi-amping/bi-wiring.

Cambridge SX-50's 5-way post terminals

Cabinet Type and Port Position

Both S20 and SX-50 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.

Cambridge SX-50 Port

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 Cambridge SX-50'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 Cambridge SX-50 has external dimensions of 225.0 x 161.0 x 240.0mm (8.8 x 6.3 x 9.4inch).

Polk S20 is clearly the larger of the two speakers. Its body is 55mm wider, 151mm taller and 110mm deeper than Cambridge SX-50.

Below you can see the front view size comparison of Polk S20 and Cambridge SX-50 in scale.

Comparison image of Polk S20 and Cambridge SX-50 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 Cambridge SX-50 is approximately 386.4cm² / 59.9inch². The S20 requires 96% more surface area than the SX-50 which gives it a small disadvantage 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 Cambridge SX-50 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 Cambridge SX-50 weighs 3.00kg / 6.6lbs. This makes the S20 158% heavier than the SX-50.

Here is a comparison of how S20 and SX-50's weights compare with the average, max and min weights in Passive Bookshelf class.

Weight
All Bookshelf Speakers

Polk S20

Cambridge SX-50

Min

Average

Max

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 Cambridge SX-50?

Here are the items that come with the SX-50:

2 Bookshelf loudspeakers
2 Grilles
8 Self-adhesive feet
2 Foam port inserts
Installation Guide

Reasons to choose Polk Audio Signature S20 over Cambridge Audio SX-50

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
High Frequency Response	40k Hz vs 22k Hz	Generates higher frequency

Reasons to choose Cambridge Audio SX-50 over Polk Audio Signature S20

Sensitivity	90 dB vs 88 dB	Play louder with same amount of amplification power
Height	225mm vs 376mm	Easier to fit in smaller spaces
Base Surface Area	386cm² vs 756cm²	Takes less floor space
Price per pair*	199USD vs 299USD	costs less (*prices may change depending on the seller, location and time)

Polk S20 vs Cambridge SX-50 Specs Table

Detailed comparison of specifications

General	Polk Audio Signature S20	Cambridge Audio SX-50
Brand	Polk Audio	Cambridge Audio
Speaker Type	Bookshelf speakers	Bookshelf speakers
Power Range	20-125 watts	10-100 watts
Sensitivity	88 dB	90 dB
Impedance	8 ohms	8 ohms
Frequency Response	39-40k Hz	50-22k Hz
Drivers
Woofer Quantity	1	1
Woofer Size	6.5"	5.25"
Woofer Composition	Mica-reinforced polypropylene	Treated paper
Woofer Surround Material	Butyl rubber	Rubber
Tweeter Size	1"	1"
Tweeter Type	Soft-Dome	Dome
Aimable Tweeter	No	No
Midrange Driver	No	No
Crossover Frequency	2500Hz	n/a
Firing Direction	rear	rear
Physical Specs
Height	376.0mm (14.8")	225.0mm (8.9")
Width	216.0mm (8.5")	161.0mm (6.3")
Depth	350.0mm (13.8")	240.0mm (9.4")
Weight	7.73kg (17lbs)	3.00kg (6.6lbs)
Enclosure	Bass Reflex	Bass Reflex
Finish	Meddite MDF	MDF/Woodgrain vinyl
Available Colors	Black, Walnut, Brown Walnut	Black
Mounting Bracket	No	No
Recommended Stand Height	24-28"	28-31"
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

Verdict

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	A	Polk S20 digs deeper - 39Hz against 50Hz.
Amplifier needs	B	Cambridge SX-50 is more sensitive (90dB vs 88dB), so it goes louder on the same amplifier.
Headroom	A	Polk S20 takes more power (125W vs 100W) - more in hand in a big room.
Size	depends	Cambridge SX-50 is easier to place; Polk S20 is bigger, which usually goes with fuller bass. Your room decides.
Price	B	Cambridge SX-50 is cheaper - $199 against $299, about 33% less.

A Polk S20 B Cambridge SX-50
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 S20 is ahead, but only on 1 of the measured areas, and it costs about 50% more. That is a lot of money for a narrow margin on paper - Cambridge SX-50 looks like the sensible buy unless something else about the Polk S20 appeals to you. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 50Hz anyway, which makes the cheaper Cambridge SX-50 much easier to justify. Match it to your room: we rate Polk S20 the better fit for a mid-size room and a large room, and Cambridge SX-50 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.