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Magnepan MG-20 loudspeaker Planar Imaging

Sidebar 2: Planar Imaging

I find planars to be the only speakers inherently capable of properly reproducing image size. I'm just as impressed as the average card-carrying audiophile with the soundstaging capabilities of a good minimonitor. Such a point-source speaker can be adept at fleshing out a convincing soundstage with excellent width and depth. However, its portrayal of image outlines tends to be too specific. Thus was born the cliché of "pinpoint imaging." Ironically, this is bandied about as a positive attribute, when in fact it's totally artificial.

[Actually, DO is only…

Magnepan MG-20 loudspeaker Measurements

Sidebar 3: Measurements

On the face of it, the MG-20 is not very sensitive, 2.83V raising an estimated 80.5dB at 1m (B-weighted). In practice, however, the speaker's line-source radiation pattern will partially compensate for this. (The level of a true line-source speaker doesn't fall off as quickly with distance as that of a point-source speaker—see later.) As DO said above, the MG-20's impedance is moderately demanding. Fig.1, taken with the passive crossover in-circuit, shows that it drops to just below 4 ohms in the bass and to 3.35 ohms in the high treble. The phase angle, however,…

Audio Dynamics ADC-1 phono cartridge

We tested two samples of the ADC-1 phono cartridge, both of which were taken from a dealer's stock. One was a demonstrator that had been in use for some months. The other was brand new, right off the shelf. Both were tested in an Empire 98 tonearm and in a Gray 108-C tonearm with its damping lightly adjusted, but results with both cartridges were for all intents and purposes identical in both arms.

The ADC-1 requires the standard 47k-ohm input termination, and its output voltage is about ideal for all current preamp designs. We adjusted the ADC-1's tracking force for the cleanest possible…

Audio Dynamics ADC-1 phono cartridge Specifications

Sidebar: Specifications

Description: Moving-magnet stereo phono cartridge. Frequency response: 10Hz–20kHz, +2dB. Separation: 30dB, 50Hz–7kHz. Output: 7mV at 5cm/s. Stylus: 0.6-mil diamond. Compliance: 20 x 10–6 cm/dyne in all directions. Recommended tracking force: 0.75–3 grams.
Price: $49.50 (1963); no longer available (2019).
Manufacturer: Audio Dynamics Corp., New Milford, Connecticut (1963). Company no longer in existence (2019).

Futterman H-3A power amplifier

It is not at all unusual these days to find manufacturers producing "matched" speakers and amplifiers that are designed specifically for one another. But it is very unusual to find this being done by an amplifier manufacturer who doesn't make loudspeakers. The Futterman H3-A is one of these rarities—an amplifier designed primarily to complement one of the best, and one of the hardest-to-drive loudspeakers on the market: the KLH Model Nine.

The H-3A is unusual in another respect, too. It is probably the closest anyone has come to combining tube and transistor technology, for although it…

Futterman H-3A power amplifier Manufacturer's Comment

Manufacturer's Comment
We did not design the H-3A specifically for use with the KLH Nine. In fact, monophonic versions of the basic design were in use 15 years ago, mainly with the RCA LC-IA loudspeaker, with which it gave superb results.

There is one coupling capacitor in each channel of the H-3A; computer-grade 800µF capacitors are used to isolate each loudspeaker from the output tube circuitry. In our opinion, direct-coupling a power amplifier to a loudspeaker (especially with transistor amplifiers) is inherently dangerous to the speaker system. In fact, some of the latest high-…

Futterman H-3A power amplifier Specifications

Sidebar: Specifications

Description: All-tube output-transformer-less stereo power amplifier. Output: 90Wpc with 16-ohm load. Frequency response: 5Hz–90kHz, +0, –0.5dB; –3dB at 200kHz. IM distortion: <0.05% at 90W (continuous sinewave) into 16 ohms. Damping factor: 200. Stability: Unconditionally stable with any kind of load. S/N ratio: better than 93 dB below 90 watts. Sensitivity: 2.0V in for 90W out. Input impedance: 270l ohms.
Dimensions: 17" W by 1O.25" D by 7.5" H. Weight: 29 lb. (Relatively light weight due to absence of output transformers.)
Price: $288, including cage…

Subjective Loudspeaker Testing

One of the most firmly-established audio platitudes is the one which says "The specs don't tell the whole story." One reason for this, of course, is the fact that most manufacturers, preferring to sell their products on the basis of emotional appeals in ads rather than on hard, cold performance claims, do not attempt to make their specs tell the whole story. They publish only the most basic, and the most impressive-looking of their specs, although they are no doubt fully aware that what they do publish is only a very small part of what even the most astute buyer would need to know in order…

Subjective Loudspeaker Testing Page 2

Now, let's seat them both in a living room and play them a perfect reproduction of the same performance. If the reproducer delivers to their ears exactly the same pattern of air vibrations that reached them in the concert hall, each listener will perceive an exact replica of the original sound. Each can choose to "tune in" to whatever aspects of the sound he normally listens to, and as long as they are delivered to his ears in exactly the same proportions as they were originally, the sound, to each listener, will be a perfect reproduction.

Now, suppose the reproducer is not perfect. (We…

Telarc's Jack Renner Remembered

I was saddened to learn that Jack Renner, renowned recording engineer and cofounder with producer Robert Woods of Telarc Records, died on June 19, 2019, age 84, at his home in Rhode Island. Mr. Renner is survived by his wife, Barbara, three children, and six grandchildren.

Renner trained as a trumpet player and received a BSc in Music Education from The Ohio State University. In 1990, he was recognized as an outstanding alumnus. He was awarded an Honorary Doctor of Musical Arts degree from the Cleveland Institute of Music, where he taught for 30 years.

I first saw Jack's name on…