What is the FTC?

The Federal Trade Commission (FTC) was established under President Woodrow Wilson in 1914 to protect consumers against trusts via the elimination and prevention of anticompetitive business practices, such as coercive monopolies. Section 5 of the Federal Trade Commission Act, 15 U.S.C. § 45 grants the FTC power to investigate and prevent deceptive trade practices. According to their own commission, federal law states that an “ad must be truthful, not misleading, and, when appropriate, backed by scientific evidence”. This sounds similar to our very own mission statement of "Pursuing the truth in audio".

The same standard is said to apply to all forms of media, be it print, online, mail, or on billboards, etc. The FTC supposedly closely examines advertsing claims that can affect consumers’ health or their wallets – claims about food, over-the-counter drugs, dietary supplements, alcohol, and tobacco and on conduct related to high-tech products and the Internet.

This all sounds great. We have an advocacy in our own government to keep the manufacturers honest. But do they really? The focus of this article is to determine that answer in the narrow scope of how it relates to the consumer audio industry, particularly power claims in amplifiers and AV receivers. This article does NOT attempt to judge sound quality of different products based solely on power ratings.

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FTC on Amplifier Power Claims

On May 3, 1974, the FTC instituted its Amplifier Rule to combat the unrealistic power claims made by many hi-fi amplifier manufacturers. "Unrealistic" meaning manufacturers specifying power solely as peak, dynamic of summed two or more channels would not be tolerated. This rule prescribes continuous power measurements performed with sine wave signals for advertising and specifications of amplifiers sold in the US. This rule was later amended in 1998 to cover self-powered speakers such as those commonly used with personal computers or portable devices.

Editorial Note on Powered Subwoofer Claims by Steve Feinstein There is a very legitimate point to be made that power ratings are irrelevant in a ‘closed’ system—a system that is self-powered, to which external speakers cannot and never will be connected. Power ratings are really only relevant in ‘open’ systems, those where external 3rd-party passive speakers will be connected to the amplifier in question. Still, above a certain price/performance/sophistication level, the customer (say, an SVS sub owner) wants to know what the product really does.

Typically, an amplifier's power specifications are calculated by measuring its output voltage (RMS), with a continuous sine wave signal, at the onset of clipping, stated as a percentage of total harmonic distortion (THD), typically at 1% into a specified load resistance of 8 or 4 ohms (depending on how the amplifier is rated). Continuous power measurements do not actually describe the highly varied signals found in audio equipment but are a reasonable way of describing an amplifier's maximum output capability. For audio equipment, this is nearly always the nominal frequency range of human hearing, 20 Hz to 20 kHz.

=> Example: 100 watts/ch, 2 channels-driven at 8 ohms from 20 Hz to 20 kHz < 1% THD+N

As a quick refresher using Ohm’s Law we get: P = V*I where Vrms*Irms = Pave = V^2 /R. So for an amplifier to be rated 100 watts/ch into an 8-ohm load, it must be able to swing 28.3Vrms unclipped.

Power vs Distortion Graph for Denon AVR-X3300W AV Receiver

It's important to understand how to read a power vs distortion graph when assessing amplifier power. The region where the lines are horizontal represents clean (unclipped) amplifier power. As the traces begin to go vertical, distortion goes up dramatically and anything to the right of the vertical lines represents gross distortion. With just two channels driven, the AVR-X3300W exceeded its 105 watts/ch rating. But with five channels driven, the receiver was unable to deliver rated power though it still managed an impressive 88 watts/ch (1% THD+N).

When you see AV recevier companies rating power at 1% or 10% THD, just realize they are rating power out of the linear operating portion (horizontal line) of the power vs distortion curve and are either doing it at the knee or where distortion dominates and increases exponentially as it goes up vertically on the curve.

Editorial Note about Peak Power Peak momentary power output and peak music power output are two different measurements with different specifications and should not be used interchangeably. Manufacturers may often use their own standard system of measurement or nomenclature to derive peak or max power but usually with an unknown method of how they derived it. The Federal Trade Commission attempted to put an end to this with Federal Trade Commission (FTC) Rule 46 CFR 432 (1974), affecting Power Output Claims for Amplifiers Utilized in Home Entertainment Products.

Understanding AV Receiver Power Ratings YouTube Discussion

16 CFR Part 432 is the Trade Regulation Rule Relating to Power Output Claims for Amplifiers Utilized in Home Entertainment Products. In this section, it is declared that all "associated" channels be driven at full power and bandwidth for up to 5 minutes. A preconditioning period of one hour shall be done prior to measuring full power by driving ALL channels at 1/8th rated power at 1kHz.

Editorial Note on De-rating Power Ratings by Steve Feinstein This was originally 1/3 rated power, in 1974. The FTC had no idea that 1/3 power was smack dab in the middle of a Class AB amp’s least efficient operating range and as a result, all the amps under test ran extremely hot during the preconditioning—even before the actual testing! Many of these amps failed during the preconditioning! The manufacturers either had to de-rate them so they wouldn’t run as hot at a lower power level or they had to redesign them with additional heatsinking. The Dynaco SCA-80—a very popular integrated amp at the time—had to be de-rated from 40 wpc to 30 wpc, because 1/3 of 40 was too hot for the amp to handle. Be wary of bureaucratic interference, even when well-intentioned!

The ruling recognizes that multi-channel amplifiers beyond two channels exist but leave it up to the manufacturers to decide which channels are "associated". In fact, the ruling even recognizes that running ALL channels simultaneously may be too taxing on an AV receivers common power supply. However, it still is implied that at least two of the channels (namely left/right front stereo pair) should be associated and tested as such. In fact, back in 2002, when the Consumers Electronics Association (CEA) noted that presently there was no industry consensus on testing, measuring and specifying power output of multi-channel amplifier products. In the absence of a voluntary industry standard that adequately addressed multi-channel amplifiers, the CEA suggested that "associated" channel groups could be tested, though not all groups simultaneously. This was left for further study to be revisited in 2008.

As of 2008, the FTC acknowledged that although the CEA issued a voluntary standard designated CEA-490A, which pertained to measuring multi-channel amplifiers with "associated" channels, wide spread adoption of the standard in advertisements of product specifications was not achieved and as a result there was no further ruling. Thus, the FTC would NOT enforce multi-channel amplifier power testing beyond two "associated" channels.

A HTIB with a claimed "1000 watts" of power

Editorial Note from an Industry Veteran about HTIB Power Claims The industry has been playing the power game for years. Also as explained in this article, so many things have changed that is impossible to come up with a consistent standard especially with the appearance of multi-channel amplifiers and receivers that offer 9,11, or more channels of amplification. "ACD" is becoming a nearly impossible standard to achieve unless a manufacturer wants to cut their power claims by 50 to 60%. And so it has become a free for all where every company plays with the conditions in their declaration of watts. The power game was actually worsened a few years back by some big box mass merchandisers. in the glory days of HTIB's (Home Theater In a Box). In one brutal example, a number of manufacturers were asked to submit samples of a complete 5 speaker, subwoofer and control section HTIB that delivered 1000 total watts. The retailer required that the 1000 watt power be printed on the display box in large print along with the other features of the system. The entire system was going to sell for $249.00! Due to manpower, workload and budget restrictions the FTC was powerless to do anything about these false declarations. The spillover from those declarations has had its effect on unsophisticated consumers who were astounded to see power ratings on real AV receivers that were on display in legitimate hi-fi retailers, especially when the brand names of the HTIB's were the same as the brands in the smaller hi-fi shops.

So Where Are We at Now with Power Ratings?

Best I could tell is all work has ceased as of 2008 from the FTC and CEA regarding how to measure multi-channel amplifiers beyond two channels. However, it seems clear that the ruling of at least two channels rated should be enforced and agreed upon by amplifier manufacturers regardless of whether or not their products have 2, 5, 7 or more amplifier channels. One would assume that when a consumer buys such a product, the power ratings specified by the manufacturer should be with at least two channels driven at full bandwidth under a specified load impedance (8 or 4 ohms, typically) and under 1% THD+N. This assumption would have been correct when two channel amplifiers dominated the audio marketplace, but is it still a safe assumption today when we've got manufacturers cramming 7 or 9 channels into an Atmos receiver for under $1000 retail price? What about the new crop of efficient Class D power amplifiers?

Join our Movement by signing our TiP (Truth in Power) Petition NOW!