Old School Polk Audio C4 Subwoofer - Fourth Order Bandpass Enclosure

Polk Audio C4 Subwoofer - Fourth Order Bandpass Enclosure with Four 6x9 Subwoofers in Isobaric Configuration

Wow, a true survivor here! An early 90's Polk Audio C4 subwoofer. This enclosure is one of the most unique factory car audio subwoofers of all time. It uses four 6x9 subwoofers mounted in a compound isobaric configuration. The center chamber is sealed, while both outer chambers are vented with a 3" x 5" port. Dual binding posts offer either 4 ohm stereo, 8 ohm mono or 2 ohm mono configuration.

Here are the technical specs provided by Polk:

Driver complement - Four 6x9 drivers monted in a isobaric push pull configuration
Enclosure type - 4th order bandpass
Frequency response - 25 to 150 Hertz
Sensitivity - 94 db @ 1 Watt @ 1 Meter
Recommended amplification - 25 to 200 Watts per channel
Impedance - 4 Ohm stereo, 2 or 8 Ohm mono
Dimensions - 8" H x 26.25" W x 17.125 D
Weight - 26 pounds

Bottom Panel of C4 Removed

Now, looking cool is nice, but sound quality and bass output is what's really important. After reviewing some  of the magazines in the OldSchoolStereo library, I found a test of this subwoofer by Car Stereo Review (March/April 1992). Since I don't have the equipment to compile technical measurements of speakers, I was intrigued to see the reviewer was able to get 119dB out of this unit. I've been using a JL Audio 12w6v2 for the past few weeks and although I haven't had my system measured, I feel pretty confident I'm pushing 125dB with only 300w. I guess what I'm alluding to is right off the bat, I wasn't expecting to obtain the output I'd become accustomed to over the past few weeks. However, I have been using a single Kicker Solobaric s10c the past year or so and it has been sufficient for my tastes so the C4 may be enough for my needs.

Now, I've only tested out the C4 for an hour or so total, so I won't leave my final impression until I've been able to give it a few weeks in my car. For now, I'll just say my initial impression is the C4 is quite impressive. It won't flex your windows or take your breathe away, but it will provide clean, hard-hitting, dynamic bass good enough for those looking to add some low end to their modest systems. I'll update the article in a few weeks with my overall impression. I've posted the video overview including demo below. Enjoy!


Make sure to Subscribe to my YouTube Channel to stay updated of my latest videos. You can also follow me on Twitter @oldschoolstereo.


See the video on YouTube in 1080p HD or embedded below: