Are all amps being built wrong?

They have always been ... but why?

Because, for the most part, most speaker drivers are linear to voltage, not current.

Nelson Pass has of course at least one if not more famous papers on how this may not be the right approach with some large drivers. 

If you want to see what a high impedance amplifier, one that is closer to a current source is, then look no further than the Stereophile tube amplifier measurements with a simulated speaker load.  As the amplifier's output impedance rises the frequency response of the amplifier tracks with the impedance curve of the speaker system.

On the VERY opposite end of the spectrum we now even have the top end Technics digital amplifiers who deliberately compensate for the impedance curves and give a near perfect voltage amplifier transfer function.

@wyoboy +1

@erik_squires "Because, for the most part, most speaker drivers are linear to voltage, not current."

Unless I misunderstood what you tried to say ... I thought linear with current.

The loudspeaker uses a moving cone to create air vibrations. The cone is put in motion via a coil (wire length L) inside a magnetic field (strength B). The force (F) that moves the cone is created by the current (I) that flows through the coil, with the linear equation F=BIL. From this it seems only logical to drive the coil with a current source, making the current independent on the loudspeaker impedance? Apparently there are other parameters and phenomenon in play that made/make amp designers choose for voltage output, which does make the current that flows dependent on speaker and cable impedance.

Unless I misunderstood what you tried to say ... I thought linear with current.

Nope. Well, linear is probably the wrong term. Proportional is correct. The output of an ideal driver in dB would be directly proportional to the output in db Volts of an amplifier.

That is, if you increase the V by 3 dB, you should measure 3 dB more acoustically regardless of the final speaker impedance (i.e. drivers + crossover).

Of course most speakers are not ideal and compression artifacts occur but this is the goal so long as we are not overdriving the speaker.

This is also why equalizers work. :) If you reduce output by 6 dB at 40 Hz in your EQ then your speaker’s output will be reduced exactly that much. Because everything is proportional to voltage.

PS, db Volts is calculated this way:

db = 20 x log( V original / Voltage now)

So doubling the amplifier voltage = 6 dB louder in both voltage and sound pressure level (SPL) so long as everything is not over driven.

It is proportional to current.
Just they shove it across a resistor and use voltage amplification from the microphone.

On the output side. the driver is not very linear to current.@rudy It was all cool into the cable impedence was mentioned.