TAPE GUIDE (Mar. 1989)

Azimuth Problems

Q. No two tape decks in the universe match exactly in terms of azimuth alignment; even my two Nakamichi decks do not produce a tape that sounds the same when recorded on one deck and played on the other.

What is the use of paying high prices for good equipment if the only tapes one can play satisfactorily are those recorded on the same deck? With high-quality components and speakers, I always hear a difference when a tape recorded on one deck is played on another, no matter what brand the decks are. Tape deck manufacturers devote their efforts to gimmicks such as auto-reverse, tape timers, music search, logic controls, double wells, etc., but they don't solve the fundamental problem of correct azimuth alignment. Other than confining the choice of cassette decks to the $2,200 Nakamichi Dragon, which provides automatic azimuth alignment in playback, what is the answer?

-Anthony Hudaverdi, Santa Monica, Calif.

A. There are several possible answers to the problem, in addition to purchasing the Dragon deck.

Use the treble or equalizer controls of your audio system to spruce up the high end, where azimuth misalignment takes its toll.

Put pressure on manufacturers, through the audio press and by letter-writing campaigns, to equip their units with an easy-to-use azimuth control for the playback head or the record-playback head. This control should be accompanied by a fine scale and a detent that enables the user to return to any setting which he has found optimal, or to the factory setting. Thus, for each cassette, one could find the best azimuth setting and note it on the tape.

Purchase one of the few decks on the market with a PlayTrim control. This supplies treble boost only at the very high end, to compensate for treble loss due to azimuth misalignment.

Learn to live with the situation. Treble response is not the same in all concert halls or in all seats in a given hall, and audio engineers at a recording session do not ignore their sophisticated equalizers and leave the controls at a flat setting at all times. The azimuth problem is just one more in a whole group of deviations from that chimerical notion of perfect frequency response. Try to listen more to the music and less to the sound.

Speed Mismatch

Q. I recently purchased an Onkyo cassette deck and found that tapes I record on the Onkyo and play back on my Akai deck sound speeded up. Conversely, tapes recorded on the Akai and played back on the Onkyo sound slow. Tapes recorded and played on the same deck sound fine when compared to the source. Why do tapes exchanged between decks sound fast or slow? Could adjustments be made to correct this?

-Jesse R. Bishop; Dundee, N Y.

A. Cassette decks frequently vary from exact speed by 0.5% to 1%, and sometimes by as much as 2%. If one deck is running fast while a second is running slow, a tape made on one and played on the other will sound a bit high- or low-pitched to a keen ear. Either your Onkyo, your Akai, or both are off-speed. (The Onkyo would appear to be slow and/or the Akai fast.) Some cassette decks have internal adjustments to fine-tune speed, and the procedure is usually simple. Check with the manufacturer or an authorized service shop. Further, your new deck should still be under warranty, so there should be no charge.

When using the same deck for record and playback, even it speed is incorrect, the same error occurs in both record and playback, thereby cancelling itself out. For example, if the recording is 1% slow and playback is also 1% slow, pitch will remain correct.

Dubbing and NR Systems

Q. I use two decks to make copies with Dolby B noise reduction of cassette master tapes encoded with dbx NR. I play the master on a Proton 740 and make the dubs on a Realistic SCT28. The signal from the Proton is fed through an equalizer to improve sound quality. The problem I have is over-processing: How can I possibly avoid this? I have tried recording without Dolby NR but still have experienced great treble loss.

-Ryan Tamares; San Bernardino, Calif.

A. For best results, your dubbing and equalizing procedure should be as follows: Play the dbx-encoded tape with the dbx decoding of your Proton on. This will produce a nominally flat output signal from the Proton. Feed this signal to the equalizer but try to avoid more than a modest amount of bass and/or treble boost, in order to prevent overloading the Realistic deck. The signal from the equalizer then goes to the Realistic for recording, with Dolby encoding applied if desired.

It might be best if you avoided the equalizer during recording, using it only in playback. A general rule is that an equalizer should be used in recording only to correct gross defects of the source tape.

How High the Treble?

Q. I am wondering why my car stereo, which is rated 30 Hz to 12 kHz, plays my homemade tapes with crystal-clear highs, despite its narrow frequency response. When I play a friend's homemade tapes, recorded on a unit with frequency response of 30 Hz to 15 kHz, they sound worse than my tapes. Shouldn't they all sound the same?

-Name withheld

A. I do not know your age, which tends to have an inverse relationship to high-frequency perception. Also, hearing can be damaged by excessive exposure to high-amplitude sounds: Many under the age of 30 have suffered permanent, partial hearing loss due to everything from rock music concerts to jackhammers. Thus, for many audiophiles, young and old, the hearing limit is well under 20 kHz, and often uncle' 12 kHz. Therefore, an audio system which plays substantially flat to 12 kHz will sound good to most persons.

Another factor to be taken into consideration is that in many music sources, there isn't all that much content above this frequency.

It appears that the playback azimuth alignment of your car's deck is in close agreement with that of the home deck you used to record your tapes, but your friend's tapes were made on a deck with somewhat different azimuth alignment. Thus, the treble response of your tapes is better preserved.

(Source: Audio magazine, Mar. 1989, HERMAN BURSTEIN)

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