Determining speaker wattage - Electronic Circuits Projects Diagrams Free

BuffaloEngineer · 25th April 2009, 11:39 PM

Is there a way to determine the power rating of a speaker if you don't have the part number? My only idea was to send a sine wave to the speaker, keep increasing the volume until the speaker blows, measuring the applied voltage and current.

Sceadwian · 25th April 2009, 11:44 PM

Use a sine wave as you said, start very slowly increasing the amplitude, but use a microphone to determine the point where the sine wave starts to distort past your cutoff point. It should start to distort past 1% well before the speaker blows, then you know the 'practical' wattage of the speaker. Audiophiles use absurdly low distortion values. But 1% is roughly the limit of where a human will notice the distortion occuring, depending on how well the speaker produces the harmonics involved.

BuffaloEngineer · 25th April 2009, 11:59 PM

Quote:

Originally Posted by Sceadwian

... but use a microphone to determine the point where the sine wave starts to distort past your cutoff point. ...

How do you mean use a microphone?

Do you mean record the output of the speaker using a mic and compare input and output curves for distortion?

Thanks! I was hoping there was a way where I didn't have to blow the speaker.

audioguru · 26th April 2009, 12:22 AM

Good speakers have a detailed datasheet complete with plans for a recommended enclosure. Garbage speakers don't. I guess your speaker is ....

Sceadwian · 26th April 2009, 12:25 AM

The point at which you can 'see' the distortion on a scope is just about the point you want to stop for ears as well. Like audiguru said though, you're going to find out just how crap those crap speakers you have are =) Mind you they need to be tested in the enclosure you're going to use.

Leftyretro · 26th April 2009, 01:38 AM

A more basic problem is that speaker 'wattage rating' is a pretty loosy goosy measurement that is rarely accompanied with the necessary parameters needed to understand it's meaning.

While consumer stereo amplifiers at one time required giving the parameters of their output power ratings (60s era FTC regulations) I've never seen many speaker manufactures qualifying their speaker 'power ratings' let alone stating any measurement standards. At best you get sometime like maximum recommend power rating, nothing about at what frequency, at what wave shape, at what duration, at what distortion value. It's a crap shot really.

Lefty

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25th April 2009, 11:39 PM	#1
BuffaloEngineer	Determining speaker wattage Is there a way to determine the power rating of a speaker if you don't have the part number? My only idea was to send a sine wave to the speaker, keep increasing the volume until the speaker blows, measuring the applied voltage and current.

25th April 2009, 11:44 PM	#2
Sceadwian	Use a sine wave as you said, start very slowly increasing the amplitude, but use a microphone to determine the point where the sine wave starts to distort past your cutoff point. It should start to distort past 1% well before the speaker blows, then you know the 'practical' wattage of the speaker. Audiophiles use absurdly low distortion values. But 1% is roughly the limit of where a human will notice the distortion occuring, depending on how well the speaker produces the harmonics involved. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har." Last edited by Sceadwian; 25th April 2009 at 11:45 PM.

26th April 2009, 12:22 AM	#4
audioguru	Good speakers have a detailed datasheet complete with plans for a recommended enclosure. Garbage speakers don't. I guess your speaker is .... __________________ Uncle $crooge

26th April 2009, 12:25 AM	#5
Sceadwian	The point at which you can 'see' the distortion on a scope is just about the point you want to stop for ears as well. Like audiguru said though, you're going to find out just how crap those crap speakers you have are =) Mind you they need to be tested in the enclosure you're going to use. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har." Last edited by Sceadwian; 26th April 2009 at 12:26 AM.

26th April 2009, 01:38 AM	#6
Leftyretro	A more basic problem is that speaker 'wattage rating' is a pretty loosy goosy measurement that is rarely accompanied with the necessary parameters needed to understand it's meaning. While consumer stereo amplifiers at one time required giving the parameters of their output power ratings (60s era FTC regulations) I've never seen many speaker manufactures qualifying their speaker 'power ratings' let alone stating any measurement standards. At best you get sometime like maximum recommend power rating, nothing about at what frequency, at what wave shape, at what duration, at what distortion value. It's a crap shot really. Lefty __________________ Measurement changes behavior Last edited by Leftyretro; 26th April 2009 at 01:39 AM.