vu meters

[2325fan]

hey guys i have a set of wattage meters out of a dead no name amp. was wonderin the best way to hook them up to my reciever. to monitor the watts my speakers are pushing. any info would be greatly appreted!!! thanks

[JoeE SP9]

First of all speakers don't push watts. They use watts. Amplifiers "push" watts. Meters of that type are essentially useless. They are not accurate and there is really no way to calibrate them so they can give accurate readings.:ihih:

[2325fan]

i kno that speakers dont push its just the way i typed it. so what would be the best way to check what my reciever is is pushin for wattage then?

[Resident Loser]

i kno that speakers dont push its just the way i typed it. so what would be the best way to check what my reciever is is pushin for wattage then?

...the "...way i typed it..." is the way it came out, and I really, really want you to "kno" that...we can't provide correct answers to wrong questions.

Best way? Probably math...and you'll need to "kno" a few incidental things like output voltage, etc...

If you know the rated RMS output into the given load and your speakers are relatively efficient, and your average SPLs are say 80 dB or so, you can "ballpark" your normal cruising output at probably <5% of that value, generally speaking...Obviously, loud peaks will increase that number...

jimHJJ(...BTW, VU meters don't measure Watts...it's Volume Units...relative to 0dB...)

[2325fan]

i kno that but im looking at the meters rite now an on the bottom it say watts @8 ohms so id say it measures watts

[E-Stat]

i kno that but im looking at the meters rite now an on the bottom it say watts @8 ohms so id say it measures watts
Nope, RL is correct. The meter has been nominally calibrated for the donor amp's output running at a particular impedance to convert the voltage to display average power. Similarly, speedometers don't measure miles per hour. They count revolutions and convert the nominal diameter of the tire to display MPH. That's why changing the diamater of the tire affects the accuracy.

rw

[Resident Loser]

Nope, RL is correct. The meter has been nominally calibrated for the donor amp's output running at a particular impedance to convert the voltage to display average power. Similarly, speedometers don't measure miles per hour. They count revolutions and convert the nominal diameter of the tire to display MPH. That's why changing the diamater of the tire affects the accuracy.

rw

...bada-boom...a tire analogy that actually works...


i kno that but im looking at the meters rite now an on the bottom it say watts @8 ohms so id say it measures watts

But then it's an output meter, not a VU meter...which is why I took issue with your terminology...The two terms aren't interchangeable...as E-Stat stated, those meters are calibrated for a specific output into an idealized load...a VU meter is used primarily for sound recording, to prevent media saturation/distortion and hi-freq anomolies and is calibrated to an industry standard which at one time was, as I recall, referenced to a1kHz signal @1.0mW into 600Ohms, but is now rated at an RMS voltage of roughly .77v...and then you get into the difference between dBm and dBu...and the meaning and ratio of decibels with regard to SPLs...and cheez it get's boring...

Suffice it to say, once one factor in the equation changes (that pesky math I mentioned earlier) the results change...

So are your loudspeakers rated @nominal 8 Ohms, or are they something else? Those meters...optimized for that idealized load...are they calibrated for a level that matches the RMS power output of your amplifier?...What about their ballistics? Are they averaging-type or peak-reading? As Joe said earlier, they are pretty useless...other than to look way cool that is...much like aftermarket wiring, heh-heh...

jimHJJ(...so you can do the math, or simply listen to the music...)

[2325fan]

ok i give up on the ones i have but is there a web site for what im lookin for ?

[spasticteapot]

Not really. It's somewhat tricky to wire meters.

Try putting a 500 ohm resistor across the leads, and connecting it to a AA battery - many of these actually measure current. If you don't get anything, try the resistor in series with the leads.

Keep trying with progressively until you get down to about 50 ohms - below this, the meter's probbably just dead.

If you can find a value that gives you a swing that's all the way across the meter, you're set. Get a potentiometer roughly equal to the value of the resistor (a screw-turn trimpot is ideal), and turn it up to the maximum impeadance (the value of the resistor). Use an op-amp as a buffer on the input ( you don't need anything fancy here), and feed the output through a diode and the meter to ground. If the needle swings the wrong way, reverse the diode; you can adjust the sensitivity by adjusting the trimpot.

This worked for me with a cheapie ammeter; it should work with some VU meters as well.

[2325fan]

sweet thanx it does work thanx for the info