impedance detector->help

[csl113]

i need to build a impedance detector....

this waht i what to build more exactly:

i neet to make the amplifier to"know" if the loudspeakers at the exit are 2,4,or 8 ohm... and in each case to activate a diffrent relay...


this is what i was thinking:

a comparator that compares the voltages at the output, and the amp's but i don't know how i can make that...(i don't know to biuld the schematic)

and also i don't know if it will work,because of the phase shift .....


does anyeone have any ideea how can i do that(not with pic's) or any link's or schematics...???


help,please..

 

[soongsc]

The speaker load is not constant throughout the audio range, it could vary to twice or three times the nominal value.

 

[ocool_15]

I think JL audio car amps (at least the non e-class entry) do that and have a regulated supply. I believe they internally switch supply rails.