Sennheiser HD 414

A featherweight open-air headphone that made closed-cup designs feel like a helmet at the concert hall.

Overview

The HD 414 weighs 135 grams - five ounces including cord and plug, by the manufacturer's own accounting - and it all but disappears on the head. The ear pads are fine-grained poly foam discs, 2¾ inches across and ¾ inch thick. The molded plastic housings slip-fit onto a molded plastic headband, and the pads come off at the slightest touch. Sennheiser built the headphone around the idea that you shouldn't have to clamp your skull in an airtight seal to hear a string section.

The acoustic case holds up on paper. The HD 414 is rated 30 Hz to 20 kHz (±4 dB, free field), with 1 mW producing 102 dB SPL at 1 kHz and a maximum loading of 100 mW to DIN 45 573. That makes it a sensitive phone, and it will reach healthy listening levels off almost anything with a headphone jack. The impedance is deliberate. The HD 414 can hang directly off the output of a 60-watt-per-channel amplifier without overloading, and it still draws enough level from a tape recorder's line output or a preamp jack to be useful. For a studio or a serious home taping setup, that flexibility is worth more than a few points of isolation.

Isolation is the trade. The open-air design leaks in both directions. Audio (May 1976, p.38) noted that the binaural approach makes it much easier to distinguish individual speakers than with a conventional stereo set-up, and that sounds such as a ringing telephone came through with disconcerting realism. In exchange you get comfort the magazine called "just about tops," and a sound it described as excellent. The HD 414 is a listening headphone, not a tracking headphone. Anyone who wants to monitor a vocal take in a live room should look elsewhere.

Maximum output for 1 percent THD at 1 kHz exceeded 120 dB. The measurements show a clean, well-matched pair of drivers, and the channel imbalance figure in particular is good.

Both had the advantage over the Stax electrostatics of needing no polarizing voltage and offering a more useful impedance. Full orchestra climaxes were handled well, and organ-and-percussion passages came through without distortion. Speech was judged natural and pleasant, with recording faults only very slightly masked.

The design's reputation traveled. Sennheiser's own advertising leaned hard on the endorsements. The company's copy cited Electronics World's October 1971 issue calling the HD 414 "the best sound of any dynamic phones" on the strength of frequency response, transient response, sensitivity, and listening tests. It also noted that the only comparable sets in that comparison chart were priced at $95 and $150. High Fidelity, per the same advertising, praised the combination of close-up headphone quality with the freedom and naturalness of loudspeaker listening, and the cooler running that comes from letting body heat dissipate. It is advertising, but the review claims can be checked against the measured data above.

The practical details are period-typical. The cord is three-conductor plastic, 10 feet long, terminating in a standard three-way phone plug. It connects to the phones through a small polarized dual plug with a yellow sleeve for left and red for right, so orientation is obvious by feel. The slip-fit housings and pop-off pads make field replacement trivial, which helps on a headphone this old. It was also good enough to be bundled with a serious portable recorder.

The HD 414 is not an isolating headphone, it is not a low-impedance phone for weak portable outputs, and it is not a modern reference monitor. It is a 135-gram, 2500-ohm, open-air dynamic headphone with measured distortion figures that hold up, a comfort reputation that period reviewers kept coming back to, and a design simple enough that most of them are still working. It is a plain piece of late-1960s German audio engineering. Buyers should expect foam pads in various states of decay, since they are consumable, and should confirm the cord and dual plug are intact, since those are the parts that go missing. Judging by the channel-matching data, the drivers themselves tend to be fine.

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