What's the difference? 2.83V/1m - 1W/1m

[1Time]

What's the difference between 2.83V/1m and 1W/1m?

For example, if the SPL is 90dB 2.83V/1, is that more or less efficient than SPL of 90dB 1W/1m?

Thanks.

[JoeBob]

At 8 ohms 2.83V will translate to 1W while at 4 ohms it will translate to 2 watts. So at 8 ohms they are equal, while sometimes a 4 ohm speaker will be quoted the sensitivity at 2.83V/1m to sound more efficient or just because it's easier to match driver sensitivity knowing the 2.83V sensitivity when you have drivers of different impedences.

[seangoesbonk]

With an 8ohm speaker, 1w/1m is the same as 2.83v/1m.
With a 4ohm speaker, 2.83v will get you 2w. So in a 4ohm speaker, 90db @ 1w/1m is more efficient than 90db @ 2.83v/1m.

Edit: beaten by Quickdraw "Joebob" Mcgraw. Fast hands.

[1Time]

Very fast reply guys. I was comparing two 8 ohm woofers so they're the same SPL. Thanks.

[SY]

Unfortunately, it's even more complicated than that. Because NO speaker has a flat impedance curve (i.e., constant impedance), to compare sensitivity and efficiency, you have to specify the test signal (e.g., 1kHz sine wave, pink noise, whatever) and the impedance curve of the speaker.

[kelticwizard]

Sy: Technically true. Also, since most speakers have a tendency to be above their rated impedance much of the time, who is to say what is a 4 ohm or an 8 ohm speaker?

Bass reflex speakers have an impedance minimum at the tuning frequency, usually 1 or 2 ohms above the DC resistance of the woofer. Time was, they rated a speaker where the minimum was. So if the impedance minimum is 6.8 ohms, they would rate the speaker as 8 ohms, because the minimum was a lot closer to 8 than to 4 ohms.

Now, some speakers with impedance minimums of 4.7 ohms or so are being marketed as 8 ohm speakers. So it is tricky.

Still, with the advent of even 2 ohm speakers for cars being rated by 2.83V, getting a speaker whose impedance minimum is reasonably close to 8 ohms is something of a blessing. Considering what the makers of 4 ohm speakers and 2 ohm speakers are getting away with by using the 2.83V standard, a manufacturer who pushes a 6 ohm speaker as an 8 ohmer looks good by comparison.