Polk Audio's db Series subwoofers give you trademark Polk performance without stressing your wallet. These subs combine high-tech materials with a laser-optimized motor structure for smooth, powerful bass response.

The db840 8" subwoofer boasts a rigid polypropylene cone and durable Santoprene™ surround built to handle big power over the long run. Polk Audio tests their subs rigorously to ensure that they stand up to sunlight, moisture, and extreme temperature changes.

Match a db sub to a suitable enclosure, and enjoy impressive low-frequency performance rarely found in this price range.


Priced per speaker

Product Highlights:

  • 8" 4-ohm subwoofer
  • polypropylene cone with Santoprene rubber surround
  • power range: 50-180 watts RMS
  • peak power handling: 360 watts
  • frequency response: 30-200Hz
  • sensitivity: 85 dB
  • top-mount depth: 4"
  • sealed box volume: 0.35 cu. ft.
  • ported box volume: 0.6 cu. ft.
  • warranty: 1 year
  • Our 60-day money-back guarantee

What's a component sub and why would I want one?

A component sub is simply a speaker that's designed to reproduce bass once it's installed in a compatible enclosure. Think about the impact of a movie soundtrack in a big theater or even in your own home HDTV setup. A component sub can add the same kind of power to the music in your car. And a car sub is not all about the boom that you hear on a street corner (although that's cool too) - you can pair a component sub with your choice of enclosure to get bass just the way you like it, from tight and punchy to fat and loose. And once you experience music in your car with a well-tuned subwoofer, you'll never go back.

Hands-on research

What's in the box?

Download owner's manual

  • One 8" woofer
  • 1 Rubber gasket (installed)
  • 8 Mounting screws
  • Manual (English/Spanish/French)
  • Online registration sheet

Product Research

Features
Enclosure Compatibility

Features

Polypropylene Cone: The cone is made with polypropylene, which provides durability while being lightweight and rigid. The cone is supported by a vented cone/coil coupler, which stiffens the cone for greater mechanical stability and lower distortion.

Santoprene Surround: The Santoprene surround is resistant to extremes in temperature, humidity, and exposure to sunlight for excellent long term reliability.

NOMEX Spider: The fire-retardant flat NOMEX Spider allows extended linear motion while providing highly reliable mechanical and thermal stability.

Triple-vented Kapton Voice Coil Former: Triple venting of the 4-layer Kapton Voice Coil Former, Cone/Coil Coupler and Pole Piece contribute to the high power handling and reliability of the db Series subs.

Klippel Laser Analyzed: The Polk db woofer's voice coil alignment, motor, and suspension are optimized using a state-of-the-art Klippel laser analyzer for superior cone travel linearity, resulting in a flatter response with lower distortion.

Break-In Period: Polk db subwoofers will achieve even greater performance once they are thoroughly broken-in. To break in a new db Sub, play music through it for 20 to 30 hours at moderate levels.

Enclosure Compatibility

Recommended Sealed Box Volume: Polk recommends mounting this woofer in a sealed enclosure made out of 3/4" MDF with an internal volume of 0.35 cu/ft.

Recommended Ported Box Volume: Polk recommends a ported enclosure made out of 3/4" MDF with an internal volume of 0.60 cu/ft using a 3" diameter x 11" long port.

Recommended Bandpass Box Volume: Polk recommends a bandpass enclosure made of 3/4" MDF with a total internal volume of 0.90 cu/ft. The bandpass box should have a 0.40 cu/ft sealed rear chamber and a 0.50 cu/ft ported front chamber with a 4" diameter x 12" long port.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Polk Audio db840 Reviews

Average Customer Review:

12 reviews
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polk audio db840 sub

Written By nick, Portland, OR on Saturday, June 15, 2013

Crutchfield Customer Review (What's this?)

  • rating
    "Coolness Factor"
  • rating
    Build Quality
  • rating
    Ease of Use
  • rating
    Sound Quality
  • rating
    Value

i am pleased with my polk audio 8 inch sub which i installed in a sound ordance sealed box. the bass punches tight and i can enjoy the crisp notes on the guitars.

Pros: gives my kenwood player more dimension

Cons: none

Excellent

Written By Anonymous, Saint Louis, MO on Tuesday, November 27, 2012

Crutchfield Customer Review (What's this?)

  • "Coolness Factor"
  • Build Quality
  • Ease of Use
  • Sound Quality
  • Value

I installed this woofer to replace a damaged one in a Tahoe. Installation was easy. After install I had much better base than the factory speakers. I had to turn the base down a little on the head unit. Excellent speaker for the money.

Pros: Price, quality

Cons: None

Polk Audio db840

Written By Brad, Jacksonville, FL on Tuesday, January 24, 2012

Crutchfield Customer Review (What's this?)

  • "Coolness Factor"
  • Build Quality
  • Ease of Use
  • Sound Quality
  • Value

The sound quality of this subwoofer is great. Like turning up the bass.

Pros: Great sound quality

Cons: Did not fit as an exact replacement as advertised. Made some minor mods to fit.

Great replacement for LSi 15 8"

Written By EndersShadow, Indianapolis, IN on Thursday, June 16, 2011

Crutchfield Customer Review (What's this?)

I am using this woofer to replace the stock 8" woofer in the Polk LSi 15 speaker. It sounds much better than the stock and was a straight drop in replacement.

I simply had to remove the rubber gasket and create my own around.

No Longevity

Written By Tropicalspeed, Houston, Texas USA on Sunday, November 21, 2010

Crutchfield Customer Review (What's this?)

I've got 21 drivers in my ride and nine of them are Polk. I was immediately Impressed with
the tightness of this 8" sub and that is what I wanted: Good tight bass without the teeth-
rattling experience. Was disappointed with the frequency response as I was hoping to hear
the upper bass sound that I got from the self-powered Bazooka that this replaced. My fault in
the sub/amp selection.
Mounted in a non-ported, .3c in. enclosure and driven by a Profile sub-amp. Unfortunately,
the sub developed the typical buzzing of the VC after about two years. Looking for another
one now.

A different use for the sub

Written By Paul, The Colony, TX on Wednesday, December 09, 2009

Crutchfield Customer Review (What's this?)

Unlike most everyone else who will buy this subwoofer, I used mine to upgrade the sub in my LSi15 home speakers. It's an easy upgrade that smooths and deepens the bass output of the 15's. I now feel as though there is enough bass for music without using a seperate powered sub.

Polk Audio db840

Written By Anonymous, Don Bedminster, Pa on Sunday, September 13, 2009

Crutchfield Customer Review (What's this?)

I have a bone stock 1995 300ZX 2+2 and wanted to keep the interior that way. I had to "hide" a subwoofer and I had been looking around for something that would fit the limited space I had to work with. I thought for certain that by going with an 8" sub, I'd be compromising the quality but I was ever wrong!. This sub fit perfectly in the small area behind the rear hatch panels and sounds incredible. I would recomend this product to anyone looking for quality sound-regardless of the space they have to work with.
Don
Bedminster, Pa

Very good "musical" bass

Written By Chris, Boston, MA on Tuesday, June 09, 2009

Crutchfield Customer Review (What's this?)

Installed this sub into a custom made enclosure built in the center console of a Jeep Wrangler. At 8" it adds nice musical low-end, no thumping heard from a mile away but that is what I wanted. I am feeding with a 200W Rockford Fosgate amp and it seems to really appreciate the power since the sensitivity is pretty low. The enclosure is a little over .3 cu ft but stuffed so virtually close to the recommended .35 cu ft and sounds great. Perfect sub for adding musical low-end to a vehicle.

Polk Audio db840

Written By Bret, Valrico, FL on Tuesday, April 07, 2009

Crutchfield Customer Review (What's this?)

Great sub woofers. I have them in 2007 Ford F150 Supercrew. I found a great center console to mount them in and it sits in the center of the back seat.

Great service from Crutchfield.

Polk Audio db840

Written By GranburyRob, Granbury, Texas on Tuesday, March 03, 2009

Crutchfield Customer Review (What's this?)

Very good. I mounted these bad boys in old enclosure, put behind the back seat in my daughters' 73 vw convertible and these things really move some air. I have a Kicker amp in bridge mode supplying the power and it seems to really work well. - Rob

Very Nice!

Written By Tracy, Minneapolis, MN on Tuesday, March 18, 2008

Crutchfield Customer Review (What's this?)

This is my first subwoofer, and I am very impressed! I didn't have much room, so I got this 8" sub and a custom Q-Logic enclosure for my truck. (My truck is a Dodge Dakota.) I already had Polk db's for my main speakers, so I went with Polk db for the sub too. It really adds the depth I was looking for to fill out my music. It really fills out the low end very nicely! With this sub as part of my system now, I was able set the amp for the main speakers to high pass, relieving them of the burden of having to produce the deep bass. I notice that I can turn the overall volume of my system up louder now. And, it stays clear too! I am very happy!

Polk Audio db840

Written By Dan, Rapid City SD on Tuesday, March 04, 2008

Crutchfield Customer Review (What's this?)

Good sound reproduction mounted in .35 sq ft Q-Logic box. Needs ample power for best results. (150 watts)

Get everything you’ll need to enjoy your new Polk Audio db840

We've verified that these enclosures are a good match for this subwoofer.
It's critical to have good wire, and none is included with the sub.
Reduce ambient road noise and your vehicle's "rattles," for better sound inside your car.
Add a grille and keep your sub safe.
These can be useful if you are building a custom box.
Sound Ordnance™ Bass Bunker

Sound Ordnance™ Bass Bunker

Ported single 8" subwoofer enclosure (Model BB8-60V)

Item #: 777BB860V

(13)

$49.99
Add to Cart
Sound Ordnance™ Bass Bunker

Sound Ordnance™ Bass Bunker

Pair of sealed 8" wedge-style enclosures (Model BB82W)

Item #: 777BB802

(5)

$59.99
Add to Cart
Sound Ordnance™ Bass Bunker

Sound Ordnance™ Bass Bunker

Sealed single 8" subwoofer enclosure (Model BB8-35S)

Item #: 777BB835S

(13)

$39.99
Add to Cart
T-Spec 16-gauge Speaker Wire

T-Spec 16-gauge Speaker Wire

Black/white jacket — priced per foot

Item #: 120SW16WB1

(13)

T-Spec 12-gauge Speaker Wire

T-Spec 12-gauge Speaker Wire

Black/white jacket — priced per foot

Item #: 120SW12WB1

(30)

Stinger PRO Series Speaker Wire

Stinger PRO Series Speaker Wire

Priced per foot (16 Gauge)

Item #: 541SPW516B

(53)

Dynamat 19100

Dynamat 19100

License Frame Kit

Item #: 15419100

(15)

$14.99
Add to Cart
Dynamat Xtreme Wedge Pack

Dynamat Xtreme Wedge Pack

1 sheet, 4 square feet

Item #: 15410425

(7)

$39.99
Add to Cart
Dynamat SuperLite Tri-Pak

Dynamat SuperLite Tri-Pak

Triple package — 3 sheets, 12 square feet (Model #10612)

Item #: 15410612

(17)

$69.99
Add to Cart
Dynamat Xtreme Trunk Kit

Dynamat Xtreme Trunk Kit

5 sheets, 20 square feet

Item #: 15419405

(14)

$169.99
Add to Cart
Dynamat Dynaliner

Dynamat Dynaliner

One 54" x 32" sheet (1/8" thick)

Item #: 15411101

(6)

$69.99
Add to Cart
Polk Audio db8G

Polk Audio db8G

8" subwoofer grille

Item #: 107DB8G

$29.99
Add to Cart
Metra Speaker Terminal

Metra Speaker Terminal

Round terminal cup with binding post connectors (for do-it-yourself box builders)

Item #: 120TCRB

(13)

Corner Protectors

Corner Protectors

Item #: 1251536

(5)

Metra Box Carpet

Metra Box Carpet

Carpet roll (54" x 5 yards) — available in 3 colors (Black)

Item #: 120TL3015

(24)

$39.99
Add to Cart
Polyester Fiber Stuffing

Polyester Fiber Stuffing

Make your subwoofer think it's in a bigger box (1-pound pack)

Item #: 027808

(36)

$12.99
Add to Cart
Metra Speaker Terminal

Metra Speaker Terminal

Round terminal cup with spring clip connectors (for do-it-yourself box builders)

Item #: 120TCRS

(6)

Rubber Feet

Rubber Feet

Item #: 125F1692

(4)

Springback Handle

Springback Handle

Item #: 125H1051K

(2)

Metra Speaker Terminal

Metra Speaker Terminal

Square terminal cup with binding post connectors (for do-it-yourself box builders)

Item #: 120TCSB

(7)

Metra Speaker Terminal

Metra Speaker Terminal

Square terminal cup with spring clip connectors (for do-it-yourself box builders)

Item #: 120TCSS

(7)

Port Tube

Port Tube

3" diameter, 4-1/2" long

Item #: 125M1702

(2)