Sennheiser MS 100 Headphones Review

Although Sennheiser calls the MS 100 stereo headphones an “Inside-Out” model, this does not imply any unique physical construction. Rather, it emphasizes the dual-purpose design of these phones, which are equally suited for use with a home music system (“inside”) or with a personal portable cassette player or radio (“outside”).

The MS 100 (the “miniStar” marking on the headband gives a clue to the origin of that nomenclature) employs the Open-Aire technology that has long been a feature of Sennheiser phones. Each earpiece is vented to the outside on its rear surface in addition to the direct inward coupling to the ear. The earpieces rest very lightly on the ears with acoustically transparent yellow foam cushions. The cushions are removable, and a spare, less flashy gray pair is included with each set of phones. A lightweight, adjustable metal-spring headband connects the two earpieces and rests lightly on the wearer’s head. The MS 100 weighs a mere 1.4 ounces, and its integral lightweight parallel-conductor 4-foot cable is fitted with a standard stereo miniphone plug that fits any personal portable unit.

For “inside” use the MS 100 comes with a 6-foot extension cable. A stereo miniphone jack at one end accepts the phones’ fitted plug, and the other end is terminated in a full-size 1/4-inch phone plug compatible with most home amplifiers, receivers, CD players, and cassette decks.

The manufacturer’s ratings of the Sennheiser MS 100 list its frequency response as 20 to 20,000 Hz (no tolerance given), impedance as 42 ohms, sensitivity as 96 dB nominal sound-pressure level (SPL) at 1,000 Hz (no drive level given), and distortion as 1 per cent (measurement conditions not stated). Price: $85.

Laboratory Measurements

The Sennheiser MS 100 phones were tested on a standard headphone coupler. A drive level of 1 volt and a sweeping sine wave with a one-tenth-octave “warble” were used for the frequency-response measurement. The resulting frequency-response curve was impressively flat and smooth (for a headphone). The midrange response (at a very loud 110 dB SPL) was almost perfectly flat from about 500 to 1,200 Hz. The output rose gently to about +4 dB at 150 Hz and fell off at 9 dB per octave below 100 Hz, reaching — 18 dB (referred to the midrange output) at 20 Hz.

There was a 7-dB peak centered at 2,600 Hz, with minor response irregularities between 3,000 and 12,000 Hz, above which the output dropped off rapidly. The overall variation of only 7.5 dB from 85 to 12,000 Hz represents excellent uniformity for a headphone (peak-to-peak variations of 20 dB or more are common in high-frequency coupler measurements).

The impedance of each earpiece was 40 ohms over most of the audio range, with peaks of 50 ohms at 130 Hz and 52 ohms at 20.000 Hz. The harmonic distortion of the headphone output was measured at 100 and 1.000 Hz with input levels between 0.1 and 3 volts (corresponding to midrange sound-pressure levels from 90 to 120 dB). At 1,000 Hz the distortion was lost in the measurement system’s noise levels for outputs below 100 dB. It was 0.16 per cent at 100 dB and rose smoothly to 0.26 per cent at 120 dB. As expected, the low-frequency (100-Hz) distortion was higher because of the intrinsic nonlinearity of the greater diaphragm excursions. It varied from 1.6 per cent at 90 dB to 17.8 per cent at 120 dB.

We also measured the headphone response with the impulse driving signal of our IQS FFT analyzer, largely to confirm the sweeping-sine-wave response measurements. The results were essentially similar, with the peak at 2,600 Hz being the most prominent departure from flatness.

Comment

We have been favorably impressed by the sound quality of several su-pra-aural lightweight headphones we have used, and the Sennheiser MS 100 is unquestionably one of the finest of those we have tested. Its quality was apparent from first hearing and was further confirmed by our measurements. The overall smoothness of its acoustic response surpasses that of many full-size circumaural headphones, a few expensive electret or electrostatic models being the principal exceptions. The acknowledged limitations of any supra-aural phone in the bass region apply, of course, to the MS 100, but it is interesting to note that its sound gives no sense of thinness or lack of bass. No doubt this is due in part to its observed attenuation of the extreme high frequencies, since a balanced frequency response is always more pleasing than one that extends far into either the low-frequency or high-frequency range without a corresponding extension at the other end of the spectrum.

The sound of the MS 100 has virtually none of the unpleasant colorations that afflict many phones. The 2,600-Hz emphasis was not audible as a balance coloration, although it may have contributed to the feeling of immediacy and contact with the sound source that one experiences with these phones. We found them completely acceptable for use with a home music system, and their sensitivity leaves no doubt that they will deliver equally satisfying results with a portable tape player or receiver. The high sensitivity of the MS 100 implies an ability to develop very high listening levels from even the low-power output of a typical portable player. We would caution, however, against indiscriminately playing these phones at their maximum levels. Prolonged listening at the highest levels these phones can develop could be dangerous to your hearing.

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