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Sea Ranch Subwoofer

The Sea Ranch Subwoofer project was designed as a built-in subwoofer to complement an existing audio system. The owners are John and Katy Horn (yep, that'd be my folks), who live in a little community in Northern California called The Sea Ranch.

Existing System

The existing audio system is comprised of a Dynaco (?Stereo 2?) preamplifier and Stereo 70, both recently rebuilt by Audio by Van Alstine, omnidirectional speakers designed by ERD, and assorted source components, including a Pioneer multi-disc CD changer and an old (circa 1964) Dual turntable.

The original speakers are a uniqe omnidirectional design, consisting of an upward-firing 61/2" Peerless woofer, 2" Peerless soft dome midrange, and 1" Peerless soft dome tweeter. The tweeter fires upward into a convex cone-shaped reflector, which also serves as the housing for the midrange. The woofer is contained in a relatively long, narrow enclosure that is vented at the bottom, between the box and the stand. The top of one of the speakers is visible in the background of the top image at the right - it looks a little like a black nuclear power plant cooling tower. A rough diagram of the speaker is also presented at the right.

A Dynaco Stereo70 (rated at 45 wpc), recently rebuilt by Audio by Van Alstine, drives the speakers, and the Hafler DH220 was pressed into service as the sub amp. The crossover contains an inverting output, and the amplifier is run in bridged mode, providing around 380 watts into 8 ohms.

The crossover is a 3rd order Butterworth (constant pressure) alignment centered at 90 Hz. As the single sub is located asymmetrically with respect to the mains, and listening is done pretty much all around the room, pure phase alignment was not possible anyway, and uniform pressure response best suited the situation.

The Owner

Here is the proud owner of this system, complete with his grandson Nicholas. The subwoofer can be seen just under his left foot, under the seat cushions. Click the image for a full-page view.

The sub is built into a window seat, with a 3 cu ft. enclosure. It is a sixth-order Class II design, consisting of a Peerless 10" CSC-X driver and a flared 4" vent.

The crossover is a custom built 3rd order Butterworth design at 90 Hz. The crossover also supplies the 2nd order filter, effectively limiting  infrasonic signals that could damage the woofer.

Subwoofer
Details on the design and construction of the subwoofer

(Photo
of
crossover)
Crossover
Details on the crossover