Polk FXi A4 Dipole Bipole Surround Speakers, Pair

$395.00

Two 1-inch silk/polymer dome tweeters aimed 45 degrees apart and a 5.25-inch Dynamic Balance woofer in a triangular, side-ported cabinet, with a switch that moves them between dipole and bipole. 88 dB, 8 ohms, 20 to 150 watts, keyhole-slotted for wall mounting. Voice-matched to Polk’s RTi and CSi models. Good working condition, fully tested.

1 in stock

Description

Polk FXi A4 Dipole Bipole Surround Speakers Pair

Versatile Polk Audio FXi A4 dipole/bipole surround speakers with switchable modes, dual tweeters, and Dynamic Balance drivers delivering enveloping rear-channel effects for immersive home theater performance.

Add the Polk FXi A4 surround speakers to your home theater system and enjoy dramatic rear-channel sound effects with your favorite movies. These cleverly designed speakers feature two 1-inch silk/polymer dome tweeters aimed 45 degrees from each other, creating an ideal mix of direct and indirect sound that fully immerses you in the movie action. A unique triangular cabinet design positions a 5.25-inch Dynamic Balance woofer and tweeter on one side, with a port and second tweeter on the opposite side, delivering spacious, three-dimensional imaging that wraps around your listening position. The dipole/bipole switch provides flexible placement options: set them to bipole mode for rear-wall mounting with distinct, directional sound, or switch to dipole mode for side-wall placement to create a more diffuse soundfield for convincing wraparound effects.

Polk carefully designed the FXi A4 drivers using laser testing to help identify and eliminate resonance points, ensuring clear, detailed highs and natural midrange reproduction. The acoustically tuned bass-reflex cabinet with side-mounted port tube delivers increased and extended bass response down to 60 Hz, adding weight and impact to explosions, musical scores, and low-frequency effects. Each tweeter uses a heat sink on the Neodymium magnet for superior heat dissipation, power handling, and reliability during extended listening sessions. The acoustically inert MDF cabinets fight internal vibrations that can compromise performance, while floating anti-diffraction grilles minimize grille diffraction for spacious imaging. At 88 dB sensitivity and 8-ohm impedance, the FXi A4 pairs easily with receivers and amplifiers from 20–150 watts, making them compatible with a wide range of home theater systems.

Voice-matched to Polk’s RTi tower and bookshelf speakers and CSi center channel speakers, the FXi A4 ensures seamless tonal integration across your entire surround system. Gold-plated 5-way binding posts accept bare wire, spade connectors, or banana plugs for secure, high-quality connections. Integrated keyhole slots make wall-mounting straightforward, though the side-ported design means they can be mounted closer to walls than rear-ported speakers without compromising bass response as severely.

Key Specifications:

Design: Dipole/bipole surround speakers with switchable mode

Drivers: Two 1-inch silk/polymer dome tweeters with Neodymium magnets and heat sinks, one 5.25-inch Dynamic Balance polymer composite woofer

Frequency response: 60–26,000 Hz (-3 dB), 50–27,000 Hz (total)

Sensitivity: 88 dB

Impedance: 8 ohms nominal

Recommended amplifier power: 20–150 watts per channel

Enclosure: Bass-reflex (ported) design with acoustically tuned side port

Terminals: Gold-plated 5-way binding posts

Mounting: Integrated keyhole slot for easy wall-mounting

Voice-matching: RTi tower and bookshelf speakers, CSi center channel speakers

Grille: Floating anti-diffraction design

Finish: Black

Condition: Good working condition, fully tested

Dimensions: (Width x Height x Depth) 287 x 306 x 198 mm (11.31 x 12.06 x 7.81 inches)

Weight: 4.08 kg (9 lbs) each

At 9 lbs per speaker, the FXi A4 offers substantial cabinet construction and driver mass that contribute to extended bass response and dynamic capability, while remaining manageable for secure wall-mounting in real home theater rooms.

These Polk Audio FXi A4 dipole/bipole surround speakers deliver the enveloping, three-dimensional soundfield that makes movies come alive, with flexible placement options, voice-matched performance to Polk’s RTi and CSi series, and quality construction that ensures years of reliable home theater enjoyment.

Backed by Radique Audio’s Bumper-to-Bumper Warranty and our Perpetual Trade-Back Program, you can purchase with confidence.

$395.00
Additional information
Weight21 lbs
Dimensions22 × 15.4 × 16.1 in
About brand
Polk Audio at Radique
New Polk Audio, too, quoted direct from the Canadian distributor:
We service Polk, too. Bring us your own Polk speakers and subwoofers for repair, servicing or restoration (speakers up to 80 lbs each), with a 90-day warranty on the work. See our Audio Service page

Polk Audio began in Baltimore in 1972, founded by Matthew Polk, George Klopfer and Sandy Gross. Its SDA speakers of the 1980s used a cable between the left and right speakers to widen the stereo image. We carry Polk towers, bookshelf speakers, centre channels and subwoofers. We've had more than 180 Polk listings so far, covering more than 80 different models. Every used Polk here is inspected, tested and serviced as required, then photographed in-house and covered by our Bumper-to-Bumper Warranty and Perpetual Trade-Back Program. Looking for new Polk? We also quote new Polk Audio direct from the Canadian distributor, with free shipping within Canada: request a quote below. Don't see the model you want? Tell us on First Dibs and we'll email you when one arrives.

Our five best-selling Polk models so far: the RTi10 towers, the PSW10 and PSW125 subwoofers, the RTi4 bookshelf speakers and the CSi3 centre.

The Polk story, 1972 to today

Matthew Polk, George Klopfer and Sandy Gross, graduates of Johns Hopkins, founded Polk Audio in Baltimore, Maryland, in 1972. The Monitor 7 of 1974 was their first model to succeed, and the Monitor 10 followed in 1976.

SDA. In 1984 Polk introduced SDA (Stereo Dimensional Array). A cable between the left and right speakers lets each one cancel the sound that crosses over to the wrong ear, for a wider stereo image.

Growth. Polk went public in 1986 and moved to new premises in Baltimore. It began moving manufacturing to Tijuana, Mexico, in 1988, and by 2012 Stereophile reported that Polk designed in the US and built in China.

New owners. Directed Electronics agreed to buy Polk in 2006. Polk later became part of Sound United, Masimo bought Sound United in 2022, and in September 2025 HARMAN, a Samsung company, completed its purchase of Sound United. The 2018 Legend series brought SDA back.

Which Polk is which?

Monitor (1970s to early 1990s): the Monitor 4, 5, 7, 10 and 12, with A, B and C revisions.

SDA (1984 to about 1991): the SDA-1 and SDA-2 families, CRS, SRS and the later "TL" models.

RTA (1979 to 1992): towers such as the RTA 11t, with two woofers and two passive radiators.

RT and RTi (2001 onward): Polk's lower-priced lines. Our best-selling RTi10 towers and RTi4 bookshelf speakers come from here.

CSi centres and PSW subwoofers: the CSi3 centre and the PSW10 and PSW125 subwoofers are among the Polks we sell most.

LSi (about 2001 to 2010) and LSiM (2011): Polk's flagship lines of that decade, followed by Signature (2016), Legend (2018) and Reserve (2021).

Buying used Polk: what to check

SDA cable. SDA speakers need the interconnect cable between them for the SDA effect, and early SDA models need a common-ground amplifier. Make sure the cable comes with the pair.

Tweeters. Owners report that some SL3000 tweeters on the 1989 to 1991 SDA TL models leaked their ferrofluid and failed, and that Monitor-series pairs may carry mismatched factory or replacement tweeters. Check that every tweeter plays.

Surrounds. Some early Polks used foam surrounds, which rot with age; later models such as the RTA 11t and LSiM use rubber. Press gently on each woofer surround.

Everything we list is inspected, tested and serviced as required here, and comes with our warranty.