Two More Headphones: Infinity ES-1; Signet TK33; Headphone Summaries and Updates (Vol.1, No.6: Spring-Fall 1978)

Two More Headphones: Infinity ES-1; Signet TK33; Headphone Summaries and Updates

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It's beginning to look as if good electrostatics were the rule rather than the exception, but a new reference standard doesn't seem to be in the cards.

As we pointed out in the headphone article in Volume 1, Number 5, our headphone tests are necessarily rather similar to our loud speaker tests. (See also the speaker survey, Part III, in this issue.) The same laboratory measurements in the frequency domain and the time domain apply, except that ways must be found to couple the measuring microphone to the headphone diaphragm in a manner simulating the on-the-head acoustic transfer conditions. Our simulations aren't exactly according to standard practice, as we said, but then standard practice isn't necessarily the most illuminative and, besides, we claim only consistency for our finding, rather than a high degree of numerical accuracy. So far, the most intensive listening tests have shown very satis factory correlation between what we measure and what our auditioners hear.

Infinity ES-1 Infinity Systems, Inc., 7930 Deering Avenue, Canoga Park, CA 91304. ES-1 electrostatic headphone, $275. Tested sample on loan from dealer.

This is an excellent electrostatic head phone but it isn't made by Infinity. It's made for them in Japan by Mechano Electronic, an outfit that obviously has more faith in time domain measurements than Arnie Nudell (see Vol. 1, No. 5, p. 11), since the ES-1 reproduces pulses and tone bursts very nicely. Pulse form retention is good even with durations as short as 90 uS, and tone bursts cause little or no ringing across the spectrum except at 3.6 kHz, where the effect is still quite mild. Well done, Mechano.

In the frequency domain the bass is particularly impressive, with extremely smooth response down to the -3 dB point of 30 Hz. High frequency response goes out to 22 kHz, with some irregularities. Specifically, there are two small rises of perhaps 3 dB each, one from 8 to 9 kHz, the other from 12 to 14 kHz. In be tween, separating the two rises, there appears to be a little suckout at 10 kHz. No big deal, all in all. (The left phone looked a bit worse than the right phone in our sample.) The fundamental resonance on the bass end appeared to have a Q of approximately 1, and this very acceptable value was retained over a wide range of drive-signal levels-an other excellent design characteristic.

Listening tests with high-quality master tapes verified the deep, well-controlled bass and gave evidence of nicely focused, thoroughly detailed sound from top to bottom, with good dynamic range. Direct comparison against the Stax SR-X/Mark 3, however, turned out to be in favor of the latter. Switching from the Infinity to the Stax gave the impression of stepping into a larger, airier and more lifelike listening environment, even though the bass wasn't as good. The Stax sounded more delicately refined and at the same time more immediate and real, even without the bass. We believe the difference to be due to the Stax's somewhat greater bandwidth and speed. At least we can't find any other good explanation, since in other respects the two units appear to be evenly matched.

Unless, of course, the explanation is mathematical: maybe every design, even by the best Japanese engineers, has a definite limit as it approaches Infinity. (E.g., the 'Black Widow' tone arm.)

Signet TK33

Signet Division, A.T.U.S., Inc., 33 Shiawassee Avenue, Fairlawn, OH 44313. TK33 Electret Stereophones, 3250. Tested sample on loan from manufacturer.

Here's an unusually interesting case. This electret (i.e., permanently polarized and there fore cordless) unit turned out to have the flat test, smoothest, most extended frequency response of any headphone we had ever tested, easily within +3 dB from 30 Hz to 35 kHz. It showed no anomalies whatsoever on tone bursts and reproduced pulses of 0.15 msec width or wider with great accuracy, with just a slight blip appearing on shorter pulses. All things considered, no headphone known to us performs better on the test bench, either in the frequency or the time domain. It's rather sad to report, therefore, that the TK33 is an extremely unsatisfactory device for listening. The problem is power handling.

In any electroacoustic transducer that can be analytically represented as a high-pass filter, there's an obvious trade-off between downward bandwidth extension and headroom, all other parameters remaining equal. For example, a minibox like the Fried B/2 speaker could be designed to go down flat almost to DC if it didn't have to play at any level above a whisper. It's this trade-off that apparently went sour in the Signet. At moderate levels, its bass performance is nothing short of phenomenal, and its overall clarity and focus are exemplary, surpassed only by the Stax SR-X/Mark 3 and not much at that. As the music becomes dynamic, however, the TK33 overloads quite obviously on the louder passages and develops audible distortion long before its neat little LED display indicates an overdriven condition.

We don't believe we had a defective sample of the Signet. The evidence indicates that the Signet engineers got carried away by small signal specs, at the expense of real-life power handling requirements.

Recommendations

Despite their superior bass performance, neither one of the above headphones can alter our previous recommendations, which were based on our usual philosophy of clarity--and detail--above all.

Best headphone so far, regardless of price:

Stax SR-X/Mark 3.

Close to the best at a much lower price:

Stax SR-5.

Headphone Summaries and Updates

All of the following reviews appeared in Volume 1, Number 5.

Fontek Minifon A-4

Specs Corp., 1169 E. Chess Drive, Foster City, CA 94404. Fontek Research Minifon A-4 electrostatic unit with C-4 coupler, $300.

A good Japanese electrostatic, with impressive presence and dynamic range, but not without audible colorations. Slightly aggressive on top and woofy below. A second sample checked did not alter our original evaluation.

Koss 'Auditor' Dynamic/10

Koss Corporation, 4129 N. Port Washington Avenue, Milwaukee, WI 53212. Auditor Series Dynamic/10 stereo headphone, $85.

Rough, peaky, unfocused, fatiguing, totally incoherent in the time domain. No longer listed, in any event, at least not under the same designation.

Koss 'Auditor' ESP/10

Koss Corporation, 4129 N. Port Washington Avenue, Milwaukee, WI 53212. Auditor Series ESP/I0 electrostatic stereo headphone with E/10 energizer, $300.

Not quite as transparent and detailed as several other electrostatics; somewhat aggressive and not altogether pleasing. Ranks below the Fontek, let alone either Stax.

Stax SR-X/Mark 3

American Audioport, Inc., 1407 N. Providence Road, Columbia, MO 65201. Stax SR-X/Mark 3 electrostatic earspeaker with SRD-7 adaptor, $290.

The most strikingly detailed and transparent headphone sound known to us, somewhat lacking in deep bass. Clarity conquers all, however (at least in our book). This is no longer the top of the Stax electrostatic line; we haven't tested yet the highly unconventional SR-Sigma at $450.

Stax SR-5

American Audioport, Inc., 1407 N. Providence Road, Columbia, MO 65201. Stax SR-5 electrostatic earspeaker with SRD-6 adaptor, $170.

Almost as good as the SR-X/Mark 3, for considerably less money. Lacking only in the ultimate smoothness and textural delicacy.

Yamaha HP-1

Yamaha International Corp., Audio Division, PO Box 6600, Buena Park, CA 90622. HP-1 Orthodynamic headphones, $65.

Among the flattest and smoothest dynamics, very listenable, but still quite incoherent in the time domain. No match for the electrostatics in clarity and focus.

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[adapted from TAC]

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Also see:

Notes Toward the Definition of Two Different "Reference" Systems

Various audio and high-fidelity magazines