Specs: Useful or misleading?
Today’s A/V receivers — even the budget models — are packed to the brim with all kinds of bells and whistles. But what good are fancy features if the receiver doesn’t sound good, right? With so many makes and models on the market, you need to weed out the bad units right off the bat. Otherwise, you just might go crazy trying to keep them all straight. To sort out your short-list, you can start by looking at some product specifications (specs) to get an idea for what you do and don’t want to spend your time auditioning. Specs, though, can be highly suspect, as you’ll see.
Fortunately, the FTC mandates that testing conditions be disclosed.
The sad truth is that manufacturer specifications are not as indicative of product quality as they once were. Many of the companies that make receivers have figured out how to “cook the books” to make their products look attractive, even if they sit at the bottom of the product line. While high-end brands don’t tend to dabble in this game, most big-name brands do to some degree. Have you noticed that almost everything pushes 100 watts per channel these days?
Still, it is possible to read between the lines and get a better idea of whether a given receiver is worth further investigation, or should be cut from the list of contenders right away. Here’s our explanation of some crucial specifications and clues on what to look for.
This is where most of the deception takes place. Manufacturers know buyers are looking for big numbers, since it is commonly assumed that more watts means more power and, therefore, better sound. So, they’ve figured out ways to achieve the numbers that look good to buyers by making the tests less stressful. If the test is super easy, then everyone can get an “A,” right?
Fortunately, the FTC mandates that testing conditions be disclosed. So, with a little know-how, it is possible to differentiate a legit power rating from one that has been fudged. The key is to look at those testing condition disclosures.
RMS: Power should be expressed as RMS and not peak power. Peak power could mean the receiver puts out X watts for well under one second. RMS (root mean squared) refers to continuous power that can be sustained for long periods of time, and is a more revealing indication of power capabilities.
All channels driven: A lower quality receiver might claim to output 100 watts per channel (WPC) in stereo mode, yet the rating will fall considerably (80 WPC or less) in surround mode. This indicates that one amp’s power is being split up among several speakers, and that usually results in poor power availability when you need it most. Instead, look for the statement “all channels driven,” which indicates amplification is equal to all of the receiver’s channels.
Bandwidth: A high power rating might also have been attained by driving a single frequency for a short amount of time. If you see 100 x 5 ( @ 1kHz), this is a sign that the receiver’s power ratings were achieved under low stress conditions and the rating on paper is much higher than what the receiver can pull off in the real world. Look for (@ 20Hz-20kHz) as an indication that the receiver was rated while driving a full range audio signal to be sure the rating is accurate.
Impedance: Impedance is a measure of electrical resistance. Most (but definitely not all) home audio speakers have impedance around 6 to 8 ohms. Manufacturers know this is the case, so they should publish power ratings established while driving an 8-ohm load. However, since power ratings can as much as double when established by using a lower impedance load, some receiver makers will use this to make their power ratings look better. Ironically, these receivers are nowhere near capable of driving a 4-ohm speaker in the real world. In fact, trying to do so will probably result in speaker and receiver damage. Bottom line, if you do see a 4-ohm power rating, there should also be an 8-ohm rating right next to it.
If you see any of the warning signs of wattage rating fudgery, we recommend you just move on to other options, since it is likely that other disclosures are less than forthright as well.
Total Harmonic Distortion (THD)
While power ratings are a valuable indicator of a receiver’s capability, they don’t tell the whole story about its sound quality. The THD rating can help round out the picture as it describes how faithful the sound signal remains to the original as the receiver amplifies it. THD less than 0.1 percent is considered to be inaudible, and 0.08 percent or lower is certainly very good. On the other hand, if you see anything higher than 0.1 percent, you can bet that the wattage ratings are way overblown. In that case, steer clear.