Sennheiser HD-224X

A closed-ear Sennheiser that Hayden Laboratories pitched as "the new ace in our pack" - and the spec sheet backs the swagger.

Overview

The HD-224X is a closed-ear dynamic headphone. Sennheiser's UK distributor Hayden Laboratories ran full-page advertising for it in Studio Sound in the autumn of 1976, and the copy got straight to the point. "Once you have tested the superb closed ear HD 224X, you will appreciate what a winner we have," the ad reads. The spec block that follows is the real argument.

The headline numbers are a frequency response of 16 to 20,000 Hz and a nominal impedance of 200 ohms, both cited to DIN 45 500. The response figure matters most for a closed-back design of this vintage. 16 Hz at the bottom is a low claim, and a closed earphone that reaches down toward organ-pedal territory is doing what closed earphones are supposed to do - keeping the low end in and the room out. The 200-ohm nominal impedance is a moderate load, the sort that wants a real headphone jack rather than a weak portable output. Sennheiser states it plainly, with no hedging.

Sensitivity is quoted at 94 dB per system at 1,000 Hz for 1 mW of input, and the ad translates that into real-world terms: 1 mW corresponds to 450 mV at 200 ohms. That is a loud headphone on modest voltage. The advertising ran in Studio Sound, a trade magazine, so the copy is aimed at people who'd use these for monitoring as much as listening. Nominal load is rated at 0.5 W to DIN 45 582, so there's headroom before you cook the voice coils. Total harmonic distortion is specified at no more than 1% to DIN 45 500.

The physical package is just as specific. Weight is approximately 252 grams without cable. That's not a featherweight, but it's reasonable for a circumaural closed design. It ships with a 3-metre cable terminated in a jack plug, a length that suggests Sennheiser expected these to live on a desk or a console rather than clipped to a walkman. The cups are circumaural, so they surround the ear rather than pressing on it, which is the more comfortable of the two closed approaches and the one that seals best.

The record does not give production years, a US retail price, driver dimensions, or any independent laboratory test. A price of $99.80 appears in one period listing, but the archive treats that figure cautiously. It's a single data point and the currency and market aren't fully nailed down, so treat it as indicative rather than definitive. The HD-224X also sits close to other Sennheiser HD 224 variants in the documentation, and period pages sometimes blur the distinctions. Anyone chasing one should confirm the exact model marking on the cups rather than trusting a listing photo.

The advertising voice is confident to the point of cocky, and the DIN-referenced specs are complete. The design brief is sealed cups, low bass extension, moderate impedance and a studio-length cable. Contemporary period commentary in HiFI-Stereo (December 1976, p.52) noted that a good octave-band equalizer could make a poor speaker system sound tolerable and a good speaker system even better.

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