What is the name of the tool?
Watts don’t come out of speakers. That's your prob. Are you trying to measure loudness, i.e. debibels? Either way, enjoy that KILL A WATT. https://www.amazon.com/dp/B01EZZ8B5Q/ref=cm_sw_r_cp_apa_fabc_8Vm6FbCMBYRTQ?_encoding=UTF8&psc=1 |
Again, forgive my ignorance. I want to measure the Watts my amp puts out, not the speakers and I misspoke. I have no meters on my power amp so I want to know how many watts I am sending to my speakers at any given time. I hope that makes more sense. The decibel meter would be something I would be interested in as well, though. Thanks. |
Amps don’t put out watts, they put out voltage. Speaker cables deliver voltage to speakers where it goes through crossover and coils all of which adds impedance, or resistance, which is good since without it the circuit would be a dead short and fry the amp. So we have voltage, and we have resistance, which is good because this means we have amps which is current flow. Which brings us to watts. You wanted to know about watts. Watts are units of power or work. Volts times amps equals watts. Its a silly thing invented by a guy James Watt who wanted to quantify the power of his new invention called the steam engine. Started with horsepower, how many horses it could replace. Wouldn’t happen to be interested in measuring that, would you? Too bad, its a fascinating story. They all are. Anyway, watts changes with impedance. Speaker impedance varies from speaker to speaker. Impedance even varies within the same speaker depending on frequency. You see the problem, surely? In order to measure watts in any meaningful way we are going to have to know the impedance. Now you know why every amp power rating is such and such watts at such and such ohms. Its never just watts. Its always watts into ohms. How in the heck are we gonna measure that?! Well, we’re not. We’re gonna measure the voltage and call it good. Which is what they do. Because really when it comes right down to it none of this has the least little thing to do with sound its all about cool stuff for guys who drool over cool stuff to have something to drool over. So you hook up a volt meter across the speaker wires and watch the needle swing. The more old-timey the meter the better. And there’s a whole lot of things in this world I know, more even than you can imagine, but why guys drool over these meters is one I never will understand. They just do. And the more old-timey the better. The current gold standard for old-timey is Steampunk, which if you can nail that you can get a cool five figures for your three figure amp just like Danny D'. So go for it. And don’t forget to regale everyone with your new found encyclopedic knowledge of speaker power measurement. Preferably sans drool. |
Hey Ricky, They did sell them a long time ago at your average Radio Shack. Terms to search for are "RMS Power meter" or "speaker power meter" Today your chances of finding one are best if you DIY them. You may also want to see this thread: https://www.forums.stevehoffman.tv/threads/any-such-thing-as-external-vu-meters.502537/ It is true that for the most part, the accuracy was questionable due to the varying impedance of loudspeakers. Even built-in amp meters assume (incorrectly) that the speakers are perfect 8 Ohms, and extrapolate from the output voltage. The only way to make an accurate watt meter, without significant computing and speaker measurement, is to put some resistor in series with the speaker. Anything that connects in parallel will only offer an approximation. On the other hand, these meters are usually good enough to tell you how close you are to exhausting your amp's output, so long as your speaker impedance isn't too low for the amp. The limits of amps at high speaker impedance is voltage. They cannot exceed their voltage rails. So if you have a 100 W amp, and you have a meter (inaccurate as it is for Watts), keeping the amp from reaching 100 W on output will keep you from exceeding the voltage rail limits. "Good enough for jazz" as they say. It is a good experiment though, I think for most music playing you'll be surprised at how little power you use most of the time. Best, E |
It’s called a VU power meter. Realistic APM-100 or Realistic APM-200. They were popular many moons ago. You might find one on Ebay if you do a search. This video shows how it works. Happy hunting! Analog VU Power Meter Realistic APM 200 Review - Bing video https://www.youtube.com/watch?v=hnkGRBKD6Eo |
