KLH Model Nine (mid-1960s)
The KLH Model Nine is one of the very few full-range electrostatic speakers ever made that needed no woofer, no crossover, and no dynamic driver of any kind. Arthur A. Janszen designed it. He pioneered practical electrostatic speaker development in the 1950s. The Nine takes the panel technology Janszen had earlier used in KLH's hybrid Model Eight and stretches it over the entire audio band. It was KLH's top-of-the-line loudspeaker and one of the first successful electrostats in the American market.
The Model Nine is a tall open frame panel, roughly 44 inches high and 27 inches wide. The electrostatic membrane hangs between two stators and sits on an oiled walnut base. There is no enclosure at all - just the panel, the grill cloth, and a separate outboard power supply that provides the bias charge. Each speaker weighs about 60 pounds and needs AC power for the electrostatic charge, as all electrostats do.
There is no crossover because there is nothing to cross over. A single full-range membrane handles everything. The panel is about 4½ inches deep, and dispersion is approximately 20 degrees, so placement matters. The Nines are generally described as a superb match for tube amplifiers, thanks to the benign 8-ohm nominal impedance and relatively high 86 dB sensitivity. A period KLH brochure specified 30 watts minimum and 150 watts maximum as suitable amplifier power. Owners consistently describe the sound as open, transparent, fast, and detailed, with spectacular mids and highs and a very large sweet spot. The caveat, noted by nearly everyone, is that bass is light and a subwoofer is often needed for modern music. High Fidelity (October 1967, p.69) covered KLH's first stereo receiver in that issue, noting that the company's engineering approach carried across its product line. That helps place the Nine within KLH's mid-1960s push into serious high-fidelity components.
The main problem for collectors today is the membrane itself. Electrostatic diaphragms lose their charge over time and must be re-diaphragmed or replaced. The original bias supply uses a tube rectifier, which also fails, and the supply can be rebuilt. Replacement panels are available from some specialty sources, though availability is inconsistent and some owners report having to do the work themselves. Asking prices for unrestored pairs generally run from about $500 to $1500, with restored examples bringing $800 to $2000 per pair. Exact production years and the original retail price are not documented in the sources available to the Archive. The record places the Nine in the mid-1960s, as the successor to the Model Eight and the predecessor to the later Model 10 hybrid.
- Full-range electrostatic panel — no woofer, no crossover
- Frequency response: 40–20,000 Hz ± 4 dB (per KLH brochure)
- Impedance: 8Ω nominal
- Dimensions: 44" H × 27" W × 4½" D; 60 lbs per speaker
- Separate outboard bias supply (tube rectifier)
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