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Polk Audio db840

db Series 8" 4-ohm subwoofer

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  • Polk Audio db840

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Item# 107DB840
 

Review Summary

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Our take on the Polk Audio db840

by Dominic Devito
Polk Audio

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.

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.

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

Priced per speaker

 

Hands-on research from the Crutchfield Labs (what are the Labs?)

Features and Specs
Size
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8 -inch
Impedance
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4 ohms
Cone Material
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Polypropylene
Surround Material
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Santoprene rubber
Ideal Sealed Box Volume (cubic feet)
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0.35
Ideal Ported Box Volume (cubic feet)
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0.6
Port diameter (inches)
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3
Port length (inches)
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11
Free-Air
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No
Dual Voice Coil
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No
Sensitivity
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85 dB at 1 watt
Frequency Response
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30 - 200 Hz
RMS Power Range (Watts)
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50-180
Peak Power Handling (Watts)
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360
Top Mount Depth (inches)
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4
Bottom Mount Depth (inches)
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4 3/8
Cutout Diameter or Length (inches)
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7 1/16
Vas (liters)
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15.4
Fs (Hz)
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42
Qts
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0.56
Xmax (millimeters)
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6.1
Parts Warranty
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1 Year
Labor Warranty
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1 Year
Product 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

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.

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.

 
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Polk Audio db840 Reviews

Average Customer Review:

12 people say:

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Filter by rating:
5 out of 5

polk audio db840 sub

Written By nick, Portland, OR on Saturday, June 15, 2013
Crutchfield Customer Review (What's this?)
 
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
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"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

Excellent

Written By Anonymous, Saint Louis, MO on Tuesday, November 27, 2012
Crutchfield Customer Review (What's this?)
 
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
1 out of 1 people found this helpful
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

Polk Audio db840

Written By Brad, Jacksonville, FL on Tuesday, January 24, 2012
Crutchfield Customer Review (What's this?)
 
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.
Was this review helpful?    Yes | No
"Coolness Factor"
Build Quality
Ease of Use
Sound Quality
Value
 
5 out of 5

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.
1 out of 1 people found this helpful
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1 out of 5

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.
1 out of 9 people found this helpful
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5 out of 5

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.
1 out of 2 people found this helpful
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5 out of 5

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
2 out of 2 people found this helpful
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5 out of 5

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.
7 out of 7 people found this helpful
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5 out of 5

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.
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5 out of 5

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
2 out of 2 people found this helpful
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5 out of 5

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!
10 out of 13 people found this helpful
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4 out of 5

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)
10 out of 15 people found this helpful
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Add accessories for the Polk Audio db840

We've verified that these enclosures are a good match for this subwoofer. See all categories & accessories

Sound Ordnance™ Bass Bunker Ported single 8" subwoofer enclosure (Model BB8-60V)
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Sound Ordnance™ Bass Bunker Pair of sealed 8" wedge-style enclosures (Model BB82W)
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T-Spec 16-gauge Speaker Wire Black/white jacket — priced per foot
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T-Spec 12-gauge Speaker Wire Black/white jacket — priced per foot
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Dynamat SuperLite Tri-Pak Triple package — 3 sheets, 12 square feet (Model #10612)
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Dynamat Xtreme Trunk Kit 5 sheets, 20 square feet
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Dynamat Dynaliner One 54" x 32" sheet (1/8" thick)
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Polk Audio db8G 8" subwoofer grille
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Metra Speaker Terminal Round terminal cup with binding post connectors (for do-it-yourself box builders)
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Metra Box Carpet Carpet roll (54" x 5 yards) — available in 3 colors (Black)
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Polyester Fiber Stuffing Make your subwoofer think it's in a bigger box (1-pound pack)
31 people say
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Metra Speaker Terminal Round terminal cup with spring clip connectors (for do-it-yourself box builders)
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Metra Speaker Terminal Square terminal cup with binding post connectors (for do-it-yourself box builders)
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Metra Speaker Terminal Square terminal cup with spring clip connectors (for do-it-yourself box builders)
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Port Tube 3" diameter, 4-1/2" long
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