Everyone wants more power. More power is better, right? Unfortunately, most advertising claims are bullshit. Buyer beware.
In the early days (1970's), boombox manufacturers published fairly accurate technical specs. They told you not just the output, but also HOW they measured it. But later, in the 1980s, the data became less accurate. Competition had increased, forcing the manufacturers to brag and make false claims.
There are four major ways output was calculated. Each produced dramatically different results. Let's look at them:
"FTC Method"
The FTC Method was created by the United States. It was the most conservative and honest way to measure output. If you took the vast majority of vintage 80's boomboxes and measured their output this way, they'd produce only 2 to 15 watts per channel.
FTC stands for Federal Trade Commission. In 1974 they established a set of testing parameters, with the goal of reducing misleading claims. Most respected hifi manufacturers obeyed these guidelines. But most boombox manufacturers didn't, because they wanted more impressive numbers for advertising purposes.
If the FTC method WAS used, your service manual will say something like this:
"Power Output: Minimum of 7 watts per channel, into 4 Ohms, from 100Hz to 20,000Hz, both channels driven, with no more than 10% THD (total harmonic distortion)"
That means:
- That it produced a MINIMUM of 7 watts per channel across the given frequency range (which in this case was 100Hz to 20,000Hz).
- The "4 Ohms" tells you the type of speakers used during the test. They tell you this so you can feel confident they used the same type of speakers that actually come with the boombox. If they didn't tell you, they could have cheated by secretly using lower ohm speakers to boost the power output measurements.
- That distortion was limited to 10% during the test. Or sometimes they say 5% or 1%, in which case you shouldn't compare that data with another boombox that was tested at 10%.
- The words "per channel" mean that both channels were driven during the test. If those words are missing, the manufacturer could have cheated by measuring output with only one channel connected, which often results in higher output.
The full FTC document is quite long and complicated. It can be viewed here: http://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=94887053abbdb19fa0689f9f44b5761c&ty=HTML&h=L&r=PART&n=pt16.1.432
"RMS Max"
This is another method of measuring output. It's not as conservative as the FTC method. Here's how it works: Remember the boombox we described above, that makes a minimum of 7 watts per channel between 100Hz and 20,000Hz? Well, that's just the minimum. There's got to be a maximum, right? It's not going to stay 7 watts all the way across such a wide frequency range. There has to be a high point somewhere. For example, maybe it peaks at 10 watts per channel at a frequency of 1,000Hz. Then the manufacturer will say 10 watts per channel "RMS" or "RMS Max". In Germany, they say "Sinus" or "Sinusleistung" instead.
"Music Power"
This is the third way of describing output. "Music Power/MPO" (or "Musikleistung" in Germany). I don't quite understand how it's calculated. But it's always higher than RMS or FTC. Usually 50% to 200% higher. That makes me suspect it's bullshit.
"PMPO"
This means "Peak Music Power Output", or "Peak Momentary Power Output". It's total bullshit. Something invented by the marketing department. I have seen some ghettoblasters claim 1,000 watts, like the Pyle PBMSPG200, shown HERE. It's ridiculous, meaningless, and silly. And unfortunately, the government doesn't care.
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OTHER HELPFUL HINTS:
There are many things that affect power output. For example, the more distortion you're willing to accept, the higher your power output can be. Boombox manufacturers often measured output at 10% distortion, to achieve more watts for marketing purposes. The problem is, if you actually listened to a boombox at 10% distortion, it would sound horrible. Premium brands like Marantz and Technics were more honest -- They usually used 5% or 1% distortion. But the cheaper brands like Conion and Lasonic used 10%, because they were trying to achieve the biggest wattage number they could, so they could brag about it.
Another thing that affects output is impedance. This is one of the numbers written on the speakers, and it's expressed in Ohms (Ω). Think of it as the resistance the speakers place on the amps. Theoretically, the lower the impedance, the more power the amps can put out. But of course, if you push the amps beyond what they're designed for, they might blow.
Finally, the power source you're using will affect the power output. AC power (wall outlet) is the best choice. The difference is usually dramatic. I have seen many, many boombox service manuals, and most of them say that AC will give you more power than you could get from batteries. Oh, and the age of your batteries is important too, because the more you use them, the more their voltage drops. When new, they might have 1.5 or more volts each, but that will decrease over time. And that will affect how many watts your boombox can deliver.
Pro-Tip:
If you can't find any information about your boombox, then look at the amplifier chips inside. There is a code number printed on them. Do a Google search on that code number. You will find the data-sheets from the company who manufactured those chips. It will tell you the power output under a wide range of conditions.
Also, look at the label on the back of your boombox. If it says "50 watts consumption", then how the hell is it going to make 100 watts, much less 1,000? You cannot make more energy than you consume.