I wasn't sure if this should go in the Vintage Speaker section or the Car Audio section, but since it's car audio, I decided to put it here. I just picked up this MINT 1992'ish Polk C4 subwoofer from a local CL ad. I took off the bottom panel to show off the "guts" and plan on doing a video demo soon.
(info below was found in an older post in the vintage speakers section. I also found an Ad in a 1992 Car Audio & Electronics and a test in a March/April 1992 Car Stereo Review. I'll post these as soon as I get them scanned in)
Here's a Polk Audio C4, circa 1992. Original MSRP was around $500.
I took off the bottom panel so you could see the goodies. I'll do a video demo soon, so stay tuned...
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