I snagged this big guy a few months ago. This is a 41 year old Dahlquist subwoofer! Indeed, subwoofers did exist back in 1976, but they weren't very common, especially in homes. Makes me wonder just what kind of a life this old beast had back in the day. Was it installed in a theater, delivering that seat shaking rumble during the mother ship scene in Close Encounters? Or was it pumping out dance classics such as the Sleeping Lions' Sound of My Heart at a discotheque? Unfortunately, I'll never know.
I had this bad boy on my workbench fully expecting the driver to need a refoam, but to my amazement it was still in very good shape. Speaking of the driver, it's a downright massive 13" woofer mounted in a heavy (65 lbs) sealed enclosure. By the way, this is a passive subwoofer, as most were before the late 1980s. To power a subwoofer like this, you'd need an external subwoofer amplifier or a passive crossover module hooked up to your main amp. As I didn't have a subwoofer amp, I used the latter.
Now, a stiff 13" driver requires serious amounts of power. I tested the subwoofer + passive crossover module with three different amplifiers: a 1992 Sony Pro-Logic AV receiver (typical home theater product of the 90s with absolutely no power supply headroom), a Marantz SR5008 home theater receiver from 2013, and Denon's flagship AVR-X7200WA. In each test, the crossover module was hooked up to the receiver's front L/R speaker outputs, and the receivers were configured to output full range audio. I set the passive crossover module to 60Hz.
The results from the first two receivers didn't exactly inspire confidence. The old Sony stereo receiver was easily driven to distortion with the subwoofer and crossover wired in. While it never went into protected mode, I feared that running it too long would cause the amp ICs to go up in flames. The Marantz SR5008, a typical 22 lbs midrange AVR, fared a bit better. I was able to get some decent volume out of the system, although listening at high volumes (-10db) for more than 10 minutes caused the receiver to go into protected mode.
Finally, I hooked the subwoofer to my Denon X7200WA, a much heavier unit with a far more robust power supply and amp section. As expected, this receiver had no problem handling the additional load. I spent a couple hours listening to music as loud as my ears could handle without any signs of trouble. However, I did notice that the Denon's two internal fans were running. Those fans never run when an active subwoofer is used!
This old skool subwoofer delivered an impressively tight and deliciously powerful low end. As most acoustic suspension designs are, this is a very musical subwoofer. I played a few tracks from Hiromi Uehara's Move and was very pleased with how nimble the speaker was, especially in the 50-60Hz region.
You may be wondering how an old, sealed passive subwoofer handles the ultra low frequencies found in many action movies. The answer is: surprisingly well, for what it is. The train derailment scene in Super 8 had my sofa shaking, although the subwoofer's response dropped off significantly below 30Hz. As expected, my duo of SVS PC12-Plus (active) subwoofers easily outperformed the old passive unit, effortlessly sending gobs of pant leg flapping energy throughout the entire room.
TL;DR: Perhaps one of the original home subwoofers, this passive unit still holds up well and is actually more musically adept than many of the active subs you'd see at Big Electronics Stores. It's not exactly friendly with entry- to mid-level receivers, as it draws so much current that most cheap receivers simply overheat and/or go into protected mode. But when you match it with a high end receiver (or even better, a powerful integrated amplifier, or a dedicated subwoofer amp), the old beast woofs beautifully!
You obviously have an idea of how much current that thing pulls, right?
