Infinity Kappa 120.3dvc 12" Dual 4-ohm Voice Coil Component Subwoofer at Crutchfield.com

Is the 92db/2.83v/m with one coil driven so into 2watts at 4 ohms or with the coils in parallel so into 4 watts or in series so 1 watt into the coil?

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- Thread starter maggiesnmacs
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Infinity Kappa 120.3dvc 12" Dual 4-ohm Voice Coil Component Subwoofer at Crutchfield.com

Is the 92db/2.83v/m with one coil driven so into 2watts at 4 ohms or with the coils in parallel so into 4 watts or in series so 1 watt into the coil?

That is a terrible specification. So much is not said, that it leaves the door open for many rediculous claims to be made on performance.

Since it is so bad I will hazard a guess at what I think they mean with: sensitivity 92dB.

92dB / 2.83Vac @ 1m, when both 4ohm voice coils are connected in parallel?

That would be equivalent to 86dB/W @ 1m, if they are telling the truth !

You need to go to the Infinity web site and download a proper datasheet.

Since it is so bad I will hazard a guess at what I think they mean with: sensitivity 92dB.

92dB / 2.83Vac @ 1m, when both 4ohm voice coils are connected in parallel?

That would be equivalent to 86dB/W @ 1m, if they are telling the truth !

You need to go to the Infinity web site and download a proper datasheet.

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Is the 92db/2.83v/m with one coil driven so into 2watts at 4 ohms or with the coils in parallel so into 4 watts or in series so 1 watt into the coil?

Almost always with coils parallel and 2.83V input.

I hear a lot where people call out something as "true" sensitivity or whatever.

Sensitivity is the sound produced for a given input. In the infinity woofer case, this is specified in the data sheet as SPL for 2.83 Volts at 1 meter. This is not any less honest or "true" than a 1Watt figure.

If you take two speakers, one with a 16 ohm impedance and 90dB/2.83V sensitivity and one with a 1 ohm impedance and 90dB/2.83 V sensitivity, they will play at the same volume when hooked up to the same amp with the same volume settings.

If you connect a 90dB/watt 16 ohm woofer and a 90 dB/watt 1 ohm woofer to the same amp with the same settings, the 1 ohm woofer will make 10*log10(16)=12dB more sound.

Amps are voltage sources, not "power" sources - the voltage sensitivity reading makes more intuitive sense in most cases.

Almost always with coils parallel and 2.83V input.

I hear a lot where people call out something as "true" sensitivity or whatever.

Sensitivity is the sound produced for a given input. In the infinity woofer case, this is specified in the data sheet as SPL for 2.83 Volts at 1 meter. This is not any less honest or "true" than a 1Watt figure.

If you take two speakers, one with a 16 ohm impedance and 90dB/2.83V sensitivity and one with a 1 ohm impedance and 90dB/2.83 V sensitivity, they will play at the same volume when hooked up to the same amp with the same volume settings.

If you connect a 90dB/watt 16 ohm woofer and a 90 dB/watt 1 ohm woofer to the same amp with the same settings, the 1 ohm woofer will make 10*log10(16)=12dB more sound.

Amps are voltage sources, not "power" sources - the voltage sensitivity reading makes more intuitive sense in most cases.

OK ya I figured they would give the figure that sounds the best i.e. in parallel and at 2.83v, and that makes sense to me compared to other ratings I've seen and the sub itself. Thanks!

All you need to do to check is to run the calculation:

eta_0 = 9.6e-10*Fs^2*Vas/Qes - this is so-called "reference" efficiency.

SPL=112.1+10*log10(eta_0) - this is Sensitivity Spl at 1W into Re

to get sensitivity at 2.83Volts, just add 10*log10(8/Re)

Good to know on the equations but they quoted their efficiency at 92db/2.83v and my question was whether that's measured with the voice coils in parallel, series or with one coil driven and it seems the consensus is that it's with the coils in parallel. thanks for the equations!

I am saying all you need to do is stick the values in from the data sheet and you can figure out how the number is generated.

btw, I mistyped. It is Fs^3, not Fs^2

Efficiency is the same series or parallel, but sensitivity is 6dB more for parallel than series.

Ah OK I see what you're saying. Thanks for the help!

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