Speaker Wattage

[JoeWawaw]

I dont know if this is the right site to post this question, but i have a speaker made up of a tweeter and a mid to low speaker.
I measured the ohmage of the speaker with a multimeter, and got around 4.3Ω. I want to find out its wattage. is there a way of finding out its wattage from the impedance only? like running different powers to find out its RMS?
I cannot open it in any way, and i do not have its brand. Here's a picture... could we estimate it from the size of the speakers?

 

[kubeek]

No, there is no way to tell, unless you´re willing to test the speaker until it breaks.
Wattage rating means how much power you can put into it without the speaker melting, so there really is no way to simply judge this. Maybe you can guess by looking at its size an year of make and comparing it to others.
My guess is about 20W.

 

[audioguru]

It appears to be a low power cheap speaker. To find out its power handling then you will probably destroy it.
Its woofer in the center is probably only 4" or 5" at 2W to 5W.
Its tweeter on the left is probably 2" at 1W.
I do not know what the things on the right side are.

 

[JoeWawaw]

hmm... it seemed like a 30W one to me
so how could i know whether 30W would be too much for the speaker if i plug it in? like if there was too much distortion or something?

 

[Nigel Goodwin]

hmm... it seemed like a 30W one to me
so how could i know whether 30W would be too much for the speaker if i plug it in? like if there was too much distortion or something?

Yes, distorted and the speaker would be destroyed - how loud are you wanting it to be?.

 

[audioguru]

A speaker fed too much power either smashes its voice coil against the magnet structure or it melts.
Luckily, speakers are usually not driven at full power continuously. Instead they are fed with music or speech that produces full power occasionally. The average power is 1/10th the peak power.

Years ago, RadioShack sold the Minimus 7 speaker. It had a 4" long throw woofer with a low resonant frequency, a pretty big magnet and a real rubber surround (not cheap foam plastic).
It had a 1" dome tweeter.

The enclosure was usually white or black cast aluminum but here is a photo of one with a (fake?) wood enclosure.
The enclosures were sealed (no port).

It was rated at 40W each and produced sounds very well from about 70hz to 20kHz. One pair of speakers costed $30.00 on sale.

I had a pair for 10 years when one woofer burned out. It was stamped, "5W Korea". The replacement woofer was also stamped, "5W" but a different country.
A few years later the other woofer burned out but the replacement was not available. I tried a Chinese woofer that looked the same but it sounded awful.

 

[JoeWawaw]

ok, i have a 14 watt amplifier ic, i think i will try with this amp first, and if the sound is loud enough and not distorted, i'll stick with it.
what would happen if i were to connect a LM386 with a higher wattage speaker than what it can provide? would it burn my ic?
also, how can i measure the voltage and current going from my amp to the speaker? would it work witha normal multimeter?

 

[kubeek]

Lm386 produces about a watt of power, so no damage should happen.
Normal multimeter will not work properly above say 200Hz, so you can´t meausre abovet that, you would need an oscilloscope to get a proper idea.

 

[audioguru]

With a 9V supply and an 8 ohm speaker an LM386 produces 0.56W when it begins to clip. It heats with 0.6W.
With a 9V supply and a 4 ohm speaker an LM386 produces 0.38W when it begins to clip. It heats with 0.85W. Less power and more heat.

With a 12V supply and an 8 ohm speaker an LM386 produces 0.66W when it begins to clip. It heats with 0.8W.
With a 12V supply and a 4 ohm speaker an LM386 produces 0.38W when it begins to clip. It heats with 1.2W which might damage it. Less power and much more heat.

 

[JoeWawaw]

so if i were to put a say 30W speaker, 6 ohms it wouldnt try to pull more watts than the lm386 can provide? the ic would simply just heat up a lot?

 

[crutschow]

The watts into a speaker are not directly determined by the maximum power the amplifier can provide. The power to the speaker is determined by the volume setting and the music content of the sound source. So as long as you keep the volume setting to a reasonable loudness output from the speaker (especially below the point of audible distortion) then you likely won't blow it.

 

[Nigel Goodwin]

so if i were to put a say 30W speaker, 6 ohms it wouldnt try to pull more watts than the lm386 can provide? the ic would simply just heat up a lot?

The wattage of the speaker makes no difference, the amplifier will only try and supply what it can - the only difference with higher wattage speakers is that they can withstand higher powers, it doesn't affect the amp at all.

 

[audioguru]

so if i were to put a say 30W speaker, 6 ohms it wouldnt try to pull more watts than the lm386 can provide? the ic would simply just heat up a lot?

Why don't you look at the graph of P-P Output Voltage Swing vs supply voltage vs speaker impedance on the datasheet like I did?
The LM386 works best with a 9V supply. There are lines for a 4 ohm speaker and for an 8 ohm speaker. 6 ohms is halfway between them.
The amplifier output when it begins to clip is only 0.52W even if the speaker is rated at 500W!
A 500W speaker is rated to survive 500W but can still play only 0.52W.

Other graphs on the datasheet show the heating of the amplifier.

Speakers don't "pull" power from an amplifier. Amplifiers provide as much power as they can if the volume is turned up.