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Polk Audio FXi A4

Dipole/bipole surround speakers (Black)

Item # 107FXIA4B

Add the Polk FXi A4 surround speakers to your home theater system and enjoy dramatic rear-channel sound effects...

Add the Polk FXi A4 surround speakers to your home theater system and enjoy dramatic rear-channel sound effects...

Discontinued item
10 questions - 31 answers

Item # 107FXIA4B

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About the Polk Audio FXi A4

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 tweeters aimed 45° from each other, for an ideal mix of direct and indirect sound.

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 tweeters aimed 45° from each other, for an ideal mix of direct and indirect sound.

Dipole/bipole operation for flexible placement
A dipole/bipole switch lets you position the FXi A4s on the rear or side walls of your home theater room — you'll get great results either way. If you place them behind your listening postion, set them to bipole mode for distinct, directional sound. Or set them to dipole mode for side placement, and they'll create a more diffuse soundfield for convincing wraparound effects.

A high-tech approach to accurate sound
Polk carefully designed the drivers using laser testing to help identify and eliminate resonance points. The acoustically inert MDF cabinets fight internal vibrations that can compromise performance. It all adds up to enveloping surround sound that fully immerses you in the movie action.

Got wire?
Most speakers don't include any. Learn about choosing and installing speaker wire at the Crutchfield Learning Center.
Shop our selection of speaker wire.


Product highlights:

  • bass-reflex (ported) design
  • frequency response 60-26,000 Hz (-3dB)
  • recommended amplifier power: 20-125 watts
  • two 1" silk/polymer dome tweeters
  • 5-1/4" Dynamic Balance® polymer composite woofer
  • 8-ohm impedance
  • sensitivity 88 dB
  • dipole/bipole switch
  • keyhole slot for easy wall-mounting
  • 5-way binding post terminals
  • voice-matched to Polk's RTi tower and bookshelf speakers and CSi center channel speakers
  • 11-5/16"W x 12-1/16"H x 7-13/16"D
  • warranty: 5 years
  • Our 60-day money-back guarantee
Priced per pair
  • MFR # AM4425-B

What's in the box:

  • 1 Black left surround speaker
  • 1 Black right surround speaker
  • 2 Self-tapping screws
  • 8 Self-adhesive rubber feet
  • Owner's Manual (English/French/Spanish)
  • Template
  • Online registration sheet
  • Polk Audio product brochure

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Crutchfield response

<< >>

More details on the Polk Audio FXi A4

Stacey B.

Features & specs

Enclosure Bass Reflex
Bipole or Dipole Bipole/Dip
Tweeter Type Soft-Dome
Tweeter Size (inches) 1
Midrange size (inches) ---
Woofer size (inches) 5-1/4
Connector Type 5-way post
Power Range 20-125
Sensitivity 88 dB
Impedance (Ohms) 8
Frequency Response 60-26k Hz
Height (inches) 12 1/16
Width (inches) 11 5/16
Depth (inches) 7 13/16
Weight (pounds) ---
Wall-mountable Yes
Bracket Included Keyhole
Parts Warranty 5 Years
Labor Warranty 5 Years
The Polk Audio FXi A4 replaces these items:

Product Research

Driver Technology
Enclosure Design
Mounting Options

Driver Technology

Dynamic Balance: Dynamic Balance is a proprietary Polk Audio technology using laser imaging to determine what combination of speaker materials create the least amount of resonance. Eliminating resonance in speakers results in a wide, smooth response and low distortion.

Polymer Composite Woofers: Each speaker features a 5.25" polymer composite woofer for smooth wide-range response with low distortion. For high performance durability, each woofer uses a butyl rubber surround.

Silk/Polymer Tweeters: Each speaker has dual 1" silk/polymer dome tweeters that provide clear, detailed highs and spacious surround effects. Each tweeter uses a heat sink on the Neodymium magnet for superior heat dissipation, power handling and reliability.

Frequency Response: The overall frequency response is 50Hz-27kHz and the -3dB frequency response is 60-26kHz.

Enclosure Design

Enclosure: Each enclosure has a triangular shape with the speaker faces angled at 45 degrees. One face has a tweeter and a woofer, while the other face has a tweeter and port tube opening. A switch for selecting Dipole or Bipole operation is located on the rear of the speaker above the speaker's 5-way binding post speaker terminals. One of the speakers is specifically designed for the "left" channel and the other for the "right" channel.

Acoustically Inert Cabinets: Each speaker cabinet features all-MDF construction with internal bracings that virtually eliminate sound-muddying resonance. The speakers are finished in either a black or white laminate finish.

Anti-Diffraction Grilles: The floating anti-diffraction grilles minimize grille diffraction for spacious, 3-dimensional imaging.

Port: On the side with only a tweeter, there is a single port tube opening for increased and extended bass response.


5-Way Binding Posts: The gold-plated 5-way binding posts will accept bare wire, pin connectors, spade connectors, banana plugs, and dual banana plugs.

Mounting Options

Dipole/Bipole Switch: There is a switch that allows each speaker to be used as a Dipole (out of phase) or Bipole (in phase) speaker. If you're mounting the speakers on the side walls in line with your listening position, the dipole mode will create a diffuse, ambient soundfield. If you're placing them behind your position, the bipole mode fires the drivers in phase to flood your room with surround sound. When used with a Dolby Digital system, the surround speaker setting should be set to small.

Wall Mounting: The bracket on the back of each speaker has two keyhole slots, allowing the speaker to be mounted on the wall using the supplied 2-1/2" wood screws.

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Customer Q&A

10 questions already asked

What speaker stands would you recommend for the polk fxi a4 speakers?
[ Kevin  Mar 15, 2021 ]
1 answer
We have not received any answers from other customers on your question. I would recommend reaching out to an Advisor by phone (1-800-324-9695) or online chat. They should be able to help answer your question.
[ Calvin  Mar 30, 2021 ]  Staff
How close to a wall corner is 'too close? How close to the ceiling is 'too close'?
[ allen  Aug 28, 2020 ]
2 answers
I don't think you have to worry about how close it is to the ceiling because the drivers fire to the left and to the right in either a bipole or dipole configuration. As far as how close to a side wall I think you would want at least 12" so the sound can be reflected off of the wall. If it's too close to the wall you won't get a full surround field.
[ Randy  Sep 01, 2020 ]
Mine are not near a corner, but based on what I hear from them I think it would depend on your room and if you're doing just surround or rear and surround, which I am. Mine are very close to the ceiling, but I used a long screw to make them tilt down significantly. I can tell you they really do sound good. I am using the dipole setting on the sides (surrounds) and the bipole setting on the rears and its really cool. I had 5.1 before with Audioengine P4 and they were fine, but these are far better. I'm also insane and running my whole 7.1 system on tube amps just for the novelty, but I'm enjoying it.
[ Schubert, Dirk  Aug 29, 2020 ]
Could these be mounted horizontally so they bounce sound off the ceiling?
[ allen  Aug 23, 2020 ]
6 answers
Definitely no. Aside from the concept possibly being flawed, the mounting brackets will not work in that direction.
[ Schubert, Dirk  Aug 29, 2020 ]
No - the mounting brackets on the back are configured for vertical mounting only.
[ John  Aug 26, 2020 ]
I suppose they could, however if you're trying to bounce off the ceiling you'll be way better off just going for some Atmos speakers which are designed to do just that.
[ Kerem  Aug 24, 2020 ]
In theory yes, although you would need to add rubber feet to the back as the speakers are not designed to lay on the their back; speaker keyhole mounting plate protrudes. Seems like an expensive ATMOS solution?
[ STAN C  Aug 24, 2020 ]
I suppose you could but I see no need to.By mounting them on wall close to ceiling & close to a corner if possible brings the best results in my opinion.Thats the way I have mine & the results are amazing!
[ Dave  Aug 23, 2020 ]
not designed to do that and there is no provision to mount that way. you need Atmos speakers for that
[ George  Aug 23, 2020 ]
I wish to connect these to a sonos connect to use in my garage as standalone pair. I realize they are intended for surround but what is your opinion of them as standalone bookshelf speakers?
[ David  Dec 27, 2019 ]
4 answers
I can tell you they are awesome for surround. I have 4 of them rounding out the side and rear. I would move towards something with more power for any other purpose. Besides with all the great choices crutchfield has, why settle on a surround speaker for that application.
[ Frank  Feb 01, 2020 ]
One word.. AwesomeEnter an answer to this question.
[ DONALD  Jan 07, 2020 ]
I personally use this as a surround speaker for my home theater system. If you use as standalone stereo speakers ,you may not get the best sound.
[ Ravi  Jan 07, 2020 ]
The very design and physical orientation of the drivers in these speakers intends their use as surround speakers only. My opinion would be a decent pair of 6"/ 8" woofer bookshelf types would sound much better and be better suited for your intended use. After all, it is just a garage, right ?? Even the Polk Atrium ( patio-type ) speakers would sound decent. ( I also have these ). ( I am not sure of the Sonos connectivity for either, however- ) Good luck. Your garage will sound very good -
[ Otto  Dec 27, 2019 ]
I am building a new 7.1 channel system and am thinking of using these FXI A4's for all 4 of the surrounds (pair on side and pair in back). Is this advisable or are they really only best for a 5.1 setup? I am planning on the CSI A4 center and the RTI A3 bookshelf speakers for the fronts.
[ Steven  Jun 05, 2018 ]
3 answers
I also have them for 7.1 sides and rear. The bipole/dipole switch is great for that. If you're going with all small-ish speakers make sure you have a decent subwoofer. That really makes or breaks a home theater system.
[ Schubert, Dirk  Aug 29, 2020 ]
Work great for side and back.
[ steve  Jun 05, 2018 ]
Yeah I don't think I'd do that. These are big- look at the measurements- these are bigger than the fronts you want to buy. I have them as 90 degree side surrounds in a 7.1 setup and they're great. They're also designed to be back a little further and make a 5.1 system sound more like a 7.1. If I were you would get those A3's but use them as your Surround Backs and then get either the A5 or A7's for your fronts (I have the A7s and love them).
[ Kellan  Jun 05, 2018 ]
do you have to mount these on the wall or is a stand OK?
[ S  Dec 27, 2016 ]
9 answers
They come with mounting plates but I'm sure stands would work as well.
[ James  Feb 19, 2017 ]
I have mine mounted on the wall, but I would imagine that they will work just as well if placed on a shelf or stand. They are fantastic speakers and you will not be disappointed!
[ FRANK A  Dec 29, 2016 ]
I have mine mounted. I think they'll work fine either way.
[ Robert  Dec 29, 2016 ]
I have mine mounted to the wall. If the floor stands you have except a wall mount bracket that would work as well.
[ Randy  Dec 28, 2016 ]
Either way. I have mine on the wall. Have these in my vacation home. I have Rti a3 at home also on the wall. Polk make the best all around speaker.
[ PATRICK  Dec 28, 2016 ]
Either way will work. I wall mounted mine.
[ jason  Dec 28, 2016 ]
The speakers are very solid and fairly heavy. I mounted mine on a wall with the integrated bracket, but I'm sure they would do fine on a properly sized speaker stand.
[ Rick  Dec 28, 2016 ]
These can be placed on a stand, table or shelf, as well as wall mounted.
[ GEORGE  Dec 28, 2016 ]
Stands should be ok, depending on location. Like any surround speakers.. location, location, location!!! Stands of course will be fine and work, so Good Luck!!
[ Greg  Dec 28, 2016 ]
I have a pair of polk 7LSI speakers. 2 questions. 1 will my speakers make a good match to polk FXI A4? 2 what one would you suggest as my back speakers? Currently using polk up front and dieing infinity in back with a klipsh center.
[ Rodlet  Jan 30, 2016 ]
2 answers
1. The Polk FXi A4 will make a satisfactory match for the LSi front speakers. 2. However you would achieve more seamless sound effects when you also add LSi surround speakers. I would recommend the Polk LSi M702 F/X as your surround speakers.
[ NORBERT  Jan 31, 2016 ]
i have all polk speakers and think they all match up well to each other, You cant go wrong. i use the FXI A4 on the sides and back. Love all 4 of them! I have the Polk Monitor 70 as my mains and the Polk CS2 as my center. go for it.
[ Martin  Jan 30, 2016 ]
I have the Infinity Primus PC253, PC351 and the PS312. Will the Polk Audio FXi A4 go with it?
[ Louis  Oct 03, 2015 ]
2 answers
yes they will and they sound very good
[ RICHARD  Oct 07, 2015 ]
I forwarded your question to an Advisor and they responded with the following: I would try to stay within manufacturer as much as possible. The reason for this has to do with voice matching your speakers. Ideally you want the same type of components in your speakers so that a motorcycle traveling front to back on your speakers will sound the same all the way across. The tweeter on the Polk FXi A4 will be a bit softer of a material and may give you too much of a warm sound versus the bit brighter sound of the Primus you already own. I would look at the Infinity Reference R152 which has a tweeter is made with much closer material than the Polk which will allow it to mesh better. If you would like to discuss further you can contact an Advisor directly by phone (1-800-324-9695) or online chat.
[ Krissy  Oct 06, 2015 ]  Staff
Will the Polk Audio FXi A4 or A6 make a good match with my system that uses Polk Monitor 75Ts?
[ Bruiser  May 15, 2015 ]
1 answer
Yes, both are a good match with the 75T. The FXi A4 is similar in price rage to your 75T. I have the FXi A4's and they produce excellent surround sound. i feel like i am sitting in a movie theatre.
[ JOHN B  May 17, 2015 ]

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