Error in SPL calculated by BoxSim?

[Ronkel]

Hi everybody,

In BoxSim, one FRS 8 4 ohm produces an SPL of 85 dB at 2.82 V, which is correct (82 dB @ 1 W, 2.82 V @ 4 ohms = 2 W, so + 3 dB). According to BoxSim, 2 FRS 8 4 ohm in series would also produce 85 dB at 2.82 V. Correct me if I'm wrong, but 2.82 V @ 8 ohms = 1 W, so I believe that means that the SPL should be 82 dB. If the SPL would be 85 dB, it would mean that simply linking two drivers would make them twice as effective (same output at half the input power). Who is wrong here?

[UweG]

Boxsim is correct here. If you have two drivers you have the double equivalent volume and so also the double efficiency. Two parallel drivers have the double power consumption and +6dB more amplitude, which normally would require four times the power. Two drivers in series have have of the power consumption and +-0dB of amplitude.

[Ronkel]

I'm still not quite understanding that. If you would keep on linking, would the efficiency go up and up again while keeping the input power at 1 W? If so, it would be possible to create a system that would have more output power than the input of 1 W... Or am I wrong again??

[CheGuevara]

you're not wrong!
aus genau diesem grund werden bei PA auch gerne große lautsprecherzeilen eingesetzt, da durch erhöhung des strahlungswiderstandes der wirkungsgrad zunimmt!
dies funktioniert solange die abgestrahlte wellenlänge größer ist als die abmessungen des arrays!

gruß
Che

[Ronkel]

Thanks Che, it's all clear to me now.