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The Hi-Fi Power Rating Hassle
October 1972 Popular Electronics

October 1972 Popular Electronics

October 1972 Popular Electronics Cover - RF CafeTable of Contents

Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics, published October 1954 - April 1985. All copyrights are hereby acknowledged.

President Ronald Reagan once stated that the nine most terrifying words of the English language were, "I'm from the government and I'm here to help." I share the sentiment generally while acknowledging that there are some areas where government oversight and regulation is needed. Problems arise where the opinions and beliefs of a self-appointed group of "experts" are allowed to impose subjective standards toward the creation of objective standards. Such was the case in the 1970s when the Federal Trade Commission (FTC) sought to publish a set of rules by which high fidelity (hi−fi) stereo equipment manufacturers must publish performance parameters. The Electronic Industries Association (EIA, now called the Electronics Industries Alliance) had their own ideas for how equipment specs should be reported. Popular Electronics magazine published hundreds of product reviews for receivers, recording and playback devices, power amplifiers, equalizers, speakers, etc., usually as reported by a testing facility called Hirsch-Houck Laboratories. what they didn't usually bother to include in the reports was that the company was bought by Ziff-Davis Publishing (owner of Popular Electronics) in 1960 - something that was news to me when I just discovered it on Wikipedia. 

The Hi-Fi Power Rating Hassle

The Hi-Fi Power Rating Hassle, October 1972 Popular Electronics - RF CafeEditorial By Milton S. Snitzer, Editor

About a year and a half ago the Federal Trade hearing Commission (FTC) held an open hearing on hi−fi amplifier power ratings. Their idea was to issue a rule on how the ratings were to be promoted and advertised. Long overdue, the rule would be a giant step forward in clearing up the confusion that exists.

We've all seen ads and catalogs giving amplifier power in terms of instantaneous peak, peak, dynamic, music, IHF, EIA, and continuous or average (incorrectly called "rms") power. Depending on which power is given, a stereo amplifier with a continuous power rating of 10 watts per channel could be rated at 20 watts continuous power (total power of both channels), 30 watts music or dynamic power, 60 watts peak music power, 80 watts peak power at some lower impedance load (say 4 ohms rather than 8 ohms), or 100 watts peak power with only a single channel driven rather than both channels. If the distortion is permitted to be 5 percent rather than say 1 percent, even higher power figures, can be quoted. With this ten to one power ratio possible and with all the figures describing the same amplifier, it is no wonder that the consumer is baffled and confused.

What the FTC was proposing is a return to the conservative continuous power per channel rating, with all channels driven, and at a given load impedance and specified distortion. They also want the power bandwidth to be expressed by quoting the minimum power output of the amplifier over the band. Other power ratings could be disclosed but these would have to be less prominently advertised and promoted.

We are bringing this up now since it was expected that the new FTC rules would be issued by June in time for the Consumer Electronics Show. Instead Federal Courts decided that the FTC had exceeded their authority by publishing any such trade regulations. The FTC is appealing the ruling and they may wind up in the Supreme Court for the final decision. In the meantime any rules promulgated by the FTC are advisory rather than mandatory.

The EIA, in the meantime, went on record as opposing the disclosure of the amount of distortion provided it was 5% or less. "For most consumers" they said, "there will be little or no perceptible improvement in the sound they hear as the total harmonic distortion is reduced below this point." They would like to see as the advertised ratings the sum of the output of each channel rather than a per-channel figure. They also object to the FTC's proposal that the minimum power over the bandwidth be quoted rather than the maximum power.

We feel sure that some sort of ruling will come out but that it won't be effective until next June at the earliest. In the meantime we expect to see more and more manufacturers coming around to the FTC's proposal. As for us, we will continue our practice, which has never changed, of specifying loads and distortion and of quoting only the continuous power rating of all the amplifiers we test or that are tested for us by Hirsch-Houck Labs.



Posted September 12, 2019

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