In this review, we will be comparing RP-504C II and CSi A6, two Passive Center Channel speakers from Klipsch and Polk Audio.
Let's have a brief look at the main features
of Klipsch RP-504C II and Polk CSi A6 first before getting into our more
detailed comparison.
| Key Specs | Klipsch RP-504C II | Polk CSi A6 |
|---|
| Brand | Klipsch
United States · founded 1946 | Polk Audio
United States · founded 1972 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Tractrix Horn | 1" Dynamic Balance |
|---|
| Woofer | 4 x 5.25" Cerametallic cone | 2 x 6.5" Dynamic Balance polymer composite |
|---|
| Frequency response | 50-25k Hz | 55-26k Hz |
|---|
| Sensitivity | 96 dB | 90 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | up to 150 watts | 20-200 watts |
|---|
| Weight | 16.50kg / 36.3lbs | 13.18kg / 29lbs |
|---|
| Dimensions (H x W x D) | 6-15/16" x 32-3/16" x 15-1/8"
177.0 x 818.0 x 385.0mm | 7-13/16" x 24-1/16" x 14-1/4"
199.0 x 612.0 x 362.0mm |
|---|
What size room are the Klipsch RP-504C II and Polk CSi A6 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* |
Klipsch RP-504C II |
Polk CSi A6 |
| 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.
Drivers
Both RP-504C II and CSi A6 are 2-way speakers.
Klipsch RP-504C IIPolk CSi A6
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
Klipsch RP-504C II |
Polk CSi A6 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
4 x 5.25-inch
|
2 x 6.5-inch
|
RP-504C II features a 1" titanium Tractrix Horn Tweeter and 4 x 5.25" Cerametallic cone Woofer with a Crossover frequency at 1950 Hz. On the other hand, the CSi A6 features a 1" silk/polymer Dynamic Balance Tweeter and 2 x 6.5" Dynamic Balance polymer composite Woofer.
Frequency Response
RP-504C II has a frequency range of 50-25k Hz whereas CSi A6 has a frequency range of 55-26k Hz. With a minimum frequency of 50Hz, the RP-504C II can go significantly deeper on the low side and provide stronger bass compared to the CSi A6's min frequency of 55Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Center Channel class in our database.
Low Frequency
Center Channel 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
RP-504C II and CSi A6 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. RP-504C II sensitivity is rated at 96 dB and the CSi A6's is at 90 dB. This 6 dB difference makes the Klipsch RP-504C II a more sensitive speaker compared to Polk CSi A6, hence will play louder with the same amount of watts.
Sensitivity
Center Channel 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.
CSi A6 can handle a max power of 200 watts RMS, whereas RP-504C II has a max power handling value of 150 watts RMS, 50 watts less than the CSi A6.
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
RP-504C II features 5-Way post type posts and CSi A6 has a 5-Way post type posts. None of these speakers feature bi-amping/bi-wiring.
Klipsch RP-504C II's Binding post terminals
Polk CSi A6's 5-Way post terminals
Cabinet Type and Port Position
Both RP-504C II and CSi A6 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
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 Klipsch RP-504C II's and Polk CSi A6's external dimensions. Klipsch RP-504C II has external dimensions of 177.0 x 818.0 x 385.0mm (6-15/16 x 32-3/16 x 15-1/8inch) whereas Polk CSi A6 has external dimensions of 199.0 x 612.0 x 362.0mm (7-13/16 x 24-1/16 x 14-1/4inch).
Polk CSi A6 is 206mm narrower and 23mm less deeper than Klipsch RP-504C II but it is also 22mm taller.
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 Klipsch RP-504C II is approximately 3149.3cm2 / 488.1inch2 and base area of the Polk CSi A6 is approximately 2215.4cm2 / 343.4inch2. The RP-504C II requires 42% more surface area than the CSi A6 which gives it a small disadvantage 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 Klipsch RP-504C II weighs 16.50kg / 36.3lbs and the Polk CSi A6 weighs 13.18kg / 29lbs. This makes the RP-504C II 25% heavier than the CSi A6.
Here is a comparison of how RP-504C II and CSi A6's weights compare with the average, max and min weights in Passive Center Channel class.
Weight
All Center Channel Speakers
What's in the Box of Klipsch RP-504C II?
Here are the items that are included inside the box of RP-504C II:
- Center channel loudspeaker
- Grille
- User Manual
- Important Safety Instructions
- Warranty Information
What's in the Box of Polk CSi A6?
Here are the items that come with the CSi A6:
- One cherry center channel speaker
- One 9.5-inch kickstand
- One 5.5-inch kickstand (installed)
- 4 Self-adhesive rubber feet
- Owners Manual
- Online registration sheet
- Polk Audio product brochure
 Sensitivity |
96 dB
vs
90 dB
|
Play louder with same amount of amplification power |
 Number of Woofers |
4
vs
2
|
More woofers |
|
Low Frequency Response |
50 Hz
vs
55 Hz
|
Generates deeper bass |
 Height |
177mm
vs
199mm
|
Easier to fit in smaller spaces |
 Max Input Power |
200 watts
vs
150 watts
|
Handle more power from your amplifier |
|
Woofer Size |
6.5 inches
vs
5.25 inches
|
Larger woofer |
 High Frequency Response |
26k Hz
vs
25k Hz
|
Generates higher frequency |
 Base Surface Area |
2215cm2
vs
3149cm2
|
Takes less floor space |
 Price per pair* |
399USD
vs
799USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Klipsch Reference Premiere RP-504C II |
Polk Audio CSi A6 |
| Brand |
Klipsch |
Polk Audio |
| Speaker Type |
Center channel speaker |
Center channel speaker (Cherry) |
| Power Range |
up to 150 watts |
20-200 watts |
| Sensitivity |
96 dB |
90 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
50-25k Hz |
55-26k Hz |
Drivers |
|
|
| Woofer Quantity |
4 |
2 |
| Woofer Size |
5.25" |
6.5" |
| Woofer Composition |
Cerametallic cone |
Dynamic Balance polymer composite |
| Woofer Surround Material |
Rubber |
n/a |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Tractrix Horn |
Dynamic Balance |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
1950 Hz |
n/a |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
177.0mm (7") |
199.0mm (7.8") |
| Width |
818.0mm (32.2") |
612.0mm (24.1") |
| Depth |
385.0mm (15.2") |
362.0mm (14.3") |
| Weight |
16.50kg (36.3lbs) |
13.18kg (29lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Wood-grain vinyl |
n/a |
| Available Colors |
Walnut, Black |
Black, Cherry |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
n/a |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
These sit in different price classes - Klipsch RP-504C II costs roughly 2x what Polk CSi A6 does. Expect it to lead on paper; the question is whether the gap is audible enough in your room to be worth it.
| Area | Better | Why |
|---|
| Bass | A | Klipsch RP-504C II digs deeper - 50Hz against 55Hz. A subwoofer would even that out. |
| Amplifier needs | A | Klipsch RP-504C II is more sensitive (96dB vs 90dB), so it goes louder on the same amplifier. |
| Headroom | B | Polk CSi A6 takes more power (200W vs 150W) - more in hand in a big room. |
| Size | depends | Polk CSi A6 is easier to place; Klipsch RP-504C II is bigger, which usually goes with fuller bass. Your room decides. |
| Price | B | Polk CSi A6 is cheaper - $399 against $799, about 50% less; arguably a different class. |
A Klipsch RP-504C II B Polk CSi A6
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?
Klipsch RP-504C II is ahead, but only on 1 of the measured areas, and it costs about 100% more. That is a lot of money for a narrow margin on paper - Polk CSi A6 looks like the sensible buy unless something else about the Klipsch RP-504C II appeals to you. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 55Hz anyway, which makes the cheaper Polk CSi A6 much easier to justify. If your amplifier is modest, vintage or valve-based, Klipsch RP-504C II is the safer partner - the other will want more current or more watts to sound its best.
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.