Experiments with the new 24ch 1cm element spacing array is too narrow or too wide.

Since it cant be any narrower, because mics' are 1cm wide, I am thinking about going back to 2cm spacing, extending the 16ch array to 24ch.

Why?

Beam radiation pattern for 1cm spacing, puts transmitter pulse frequency around 20kHz. 20kHz is nice, because you cant hear it, or.. at least I can't. (anymore).

But my crappy speaker have a hard time dealing with the max frequency spec'ed (or maybe its my cheap-o-film gaming amp that is garbage. Frequency response is dropping off a cliff fast around 20kHz, so transmitted pulse energy is really weak.

So, either I will go back to my 2cm array, where frequencies lie around 8kHz-14kHz, which is audible (nice for debugging, but annoying in the long run. Maybe I will also have problems with the CW pulse length being too short. 

Or, I buy new amp, speakers.

Or,  go for 40kHz range and use the cheap ultrasonic receivers and transmitters from SR04, which will require some clever arrangement of the receiver elements (and width is 1.6cm) since element spacing need to be 0.5cm.

For now, I will keep the current, and soon I will go back to 2cm element spacing.