toastyghost: Yes, that is one way to do that. And if it burns down for some reason, and it isn´t caused by operator, then one can conclude that he didn´t want such poor driver anyway. :-)

Of course, I meant highest power density with some fixed requirements like frequency range, or total output in some way. If there were no boundaries, most power would be achieved very different way. Two 18IPALs would definitely outdo one 21DS115 in the same box volume for SPLmax, no doubt.

MarjanM:

I haven´t seen simulator software capable of showing all in one graph, so I will pick WinISD and I will pick discrete frequency to compare and see.

We feed both speakers exactly one watt of real power at 80Hz( real power = power burnt as heat, that´s what we should count when we are after speaker output and performance and loading capabilities).

How do we do that? We set Power P at 1Watt.

P = U*I*cos(θ).

We do not know current “I” in the advance, we count it from the equation I = U/Z. We put that in our first equation.

P = U*(U/Z)*cos(θ).

We want to feed one watt of power. Therefore P = 1W, therefore:

1 = U*(U/Z)*cos(θ).

We know Z and Cos(θ) from the simulation. It is shown in the “Impedance” and “Impedance phase” graphs.

At 80Hz, Z is 14,54 for 21DS115 and 11,98 Ohms for 18SW100. Cosinus(θ) is function of phase angle. 64° and 54,55° means cos(θ) for these speakers is 0,438 and 0,58 respectively.

So, for two speakers

1 = U*(U/14,54)*0,438 for 21DS115 and

1 = U*(U/11,98)*0,58 for 18SW115.

For 1Watt of power, the voltage needed to go into the each speaker is:

5,77V for 21DS115 at 80Hz.

4,55V for 18SW100 at 80Hz.

Now let´s look at graphs with this value set (21DS115 is green). Don´t forget to look only at 80Hz, because in different frequency points, the situation is different.

At some frequencies, 21DS115 would not run away or win, in some frequencies it runs further:

Interesting thing is, what Winisd thinks is the power in watts, down in the window. It says 3,9W for 18SW100, while it says 6,5W for 21DS115….

//I see different outcome between my first and second try. First time I didn´t put that much effort into describing general thing and counting with tiny fractions. There is still room for mistakes, things take time, which I don´t have in the required amount...

I would be very afraid of such simplistic view, and very careful with conclusions based on these.

 For example B&C drivers are known for that the suspension is the main mechanical limit of the cone excursion.

Therefore at some point, mostly Cms eats up the whole force developed by the voice coil (which is not that high, with 50% or more coil out of the magnetic field).

The Qms and Qes relations only work with small signals, and relations can get absolutely different in not that high excursion.

Also carefully about ignoring certain elements in the math, as their chronology is important for the outcome. Rms is not just static parallel element to the Cms and for all frequencies. You cannot deduce one from each other and count with it like that to reach the right outcome.

But I´m happy to see that communities are diving into this science deep stuff.. J