Harman Kardon hk300xm Cassette Deck Review

The Harman Kardon hk300XM is a front-loading, two-motor, two-head cassette deck whose features include full solenoid control, a sophisticated automatic program-search function, and the Dolby HX “headroom-extension” system.

Available in relatively few cassette decks thus far, Dolby HX is an addition to—rather than a substitute for—normal Dolby-B noise-reduction circuitry. While Dolby-B reduces low-level high-frequency hiss, the HX system is designed to use the Dolby-B’s internal control signals to increase the high-level, high-frequency capabilities of the recorder by simultaneously varying the bias and record equalization to meet the momentary demands of the signal being recorded. Any HX-recorded tape is completely compatible in playback with all Dolby-B equipped decks.

Cassettes are inserted, tape openings downward, into slides behind the smoked-plastic front cover of the hk300XM. Rear illumination is provided to gauge how much tape is left on a side, and the cover is removable for routine head cleaning and demagnetization. Directly beneath the cassette well are light-touch pushbuttons, with LED indicators, that control tape motion. Four pushbuttons activate the eject, record mute, power on-off, and electronic auto search functions, the last of which puts the deck in fast-forward operation, stopping and playing about eight seconds of each recorded selection before going on to the next. Individual pushbuttons set the bias/equalization for metal, CrO2, ferrichrome, and ferric-oxide formulations, and a bias fine trim control, together with a pushbutton-controlled bias tone generator, permits the user to compensate for the bias differences between different brands of the same tape type. To adjust for different tape sensitivities, a 400-Hz recordcal tone is provided, together with small openings for left- and right-channel screwdriver-adjusted controls. Separate controls are provided for microphone and line levels, as well as an output-level control that also affects the level fed through the headphone jack. Additional pushbuttons activate the Dolby-B and HX circuitry, a multiplex filter for taping from stereo FM, and a memory rewind and reset, as well as selecting either a slow or a normal decay time for the record-level indicators.

The record indicators are twelve-segment LED displays, calibrated from —40 to +8 dB, with 0 dB corresponding to the standard cassette Dolby-level of 200 nanowebers/meter. In addition, three LED indicators (color coded in green, yellow, and red) are provided to assist the recordist when he is using the HX system. These are sensitive to frequency as well as level, so the user is appropriately warned when the treble content of the signal becomes excessive for the HX circuits.

The rear panel of the hk300XM contains the usual line-in/line-out phono jacks, together with a DIN connector for an optional remote-control accessory. Overall, the deck measures approximately 4-3/4 x 17-3/8 x 13-1/2 inches; it weighs 19 pounds. Suggested retail price: $449.

Laboratory Measurements

Our sample of the hk300XM was factory-adjusted for TDK AD (ferric), Sony FeCr (ferrichrome), TDK SA (CrO2-type), and 3M Metafine (metal) formulations, so we used these as our primary basis for evaluation. Checking other tapes, however, we found that the newly introduced JVC MEp metal tape gave marginally better results, so we substituted it instead. The Metafine had a slight (0.8 dB) advantage in signal-to-noise ratio, but it had less high-frequency response, sensitivity, and ability to handle overloads.

Playback equalization, as shown in the accompanying graph, was checked using Teac MTT-216 (ferric) and MTT-316 (CrO2-type) test tapes. Both showed a somewhat elevated bass response that was just audible in our listening tests of prerecorded material, but both extended out smoothly to the 14-kHz limit of the test tapes.

Record/playback frequency response was excellent with all but the ferrichrome tape, which fell off slightly at the highest frequencies. The TDK AD (ferric) and JVC MEp (metal) were within +0.5, — 1.5 dB from 20 to 20,000 Hz, and TDK SA reached the — 3-dB point at 18,000 Hz. This is exceptional performance in a two-head deck. The responses of the tapes below 1,000 Hz differed by less than 2 dB and were averaged for clarity.

With a 1,000-Hz, 0-dB input, the third-harmonic distortion measured 1.2 per cent for TDK AD, 1.8 per cent for TDK SA, 0.8 per cent for JVC MEp, and 2.15 per cent for Sony FeCr. To produce 3 per cent third-harmonic distortion required an input level of +3, +2, +5, and +2 dB, respectively, for the four tapes, and their unweighted signal-to-noise ratios at this output measured 48.2, 51.4, 54.3, and 50.7 dB. Adding Dolby-B noise reduction and using CCIR/ ARM weighting increased these figures to the very good values of 64.6, 67, 68.2, and 68.2 dB, respectively.

Wow and flutter, measured by recording and replaying a 3,150-Hz tone, measured 0.04 per cent according to the customary weighted-rms rating and 0.05 per cent when using the stricter DIN standard. To produce a 0-dB indication required a 0.17-volt input at the high-level jacks and 0.4 millivolt at the microphone inputs. Microphone overload occurred at a reasonably generous 85 mV. Accuracy of the Dolby-circuit calibration was exact, and tracking at a — 30-dB level was within 2 dB. With a C-60 cassette, fast-forward time measured 68 seconds, 72 seconds for rewind.

Comment

The extended high-frequency response and high signal-to-noise ratio of the hk300XM practically guarantees that the deck is able to make virtually impeccable copies of existing program material. The Dolby HX system does, indeed, make ferric tapes sound very much like metal tapes in terms of high-frequency potential, but some distortion of strong mid-frequencies is occasionally audible in the presence of equally strong high-frequency tones. Such a situation is extremely rare, however, and we had to search to find recordings with which the HX system did not work perfectly. We have no hesitation in recommending the hk300XM for both performance and value.

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