Presumably NOT using the right speakers.
Measuring for the wrong speakers is pointless.
What RMS power output is it?
Divide that by 10 for approx (max) current.
Anyone has idea how much current it will draw from 12V line? I tried to measure with multimeter during it pay loud music, connected to 2 set of dual 70W/6Ohm speakers (something which I have close by and can use for testing purpose) at maximum volume (right before this little amp shuts down itself) and was getting less then 1 amp on the power line? Am I doing something wrong?
You cannot just divide the output power by 10. Different types of amps have different efficiency ratings, meaning some power going in is wasted as heat.
You also cannot measure maximum current using a pair of speakers that have a varying load dependent on frequency, and also using music as your signal.
Are you trying to conduct a science experiment or did you just want to know? The manual states 3.5A with a 12V supply.
That's where I confused. I ran very loud music, at maximum volume, connected fairly large speakers... and never got even 1amp on 12V bus.
Anyway their output sounds like is not great for OEM Nissan speakers, so I thinking if I lower input audio with resistors and connect trough large amplifier, so I use them as pre-amp... would this work?
yes, this was an original plan... until I read about line drivers, as I have both units (for 4 speakers) and don't want to waste another $70, I would like to see if this is going to be possible.
I am learning during the install, so this is my problem
It is merely a guideline, but I find it beneficial knowing a 100W output amp will generally consume approx 10A at 12V-14.4V.
Conversely, at 3.5A in, I'd assume 35W output. (Unless the 3.5A is a peak etc.)
I'll leave impedance to the impedance matchers. (I misread the original impedance as being tenfold - ie, 60 or 70 Ohms! )