fixing radio

My TF suffers from distorted sound when the volume is above about 50%. It is a pioneer 4x50Watt unit, constant power 4x22 watt. 
I tested the radio itself on the bench, and there it works fine, but it needs 14 volts for full power, at 12 volts distortion already is visible on the scope at an output level of 12 watt. 
That is also in the manual in the tech specs. So Pioneer sells a radio of 4x50watt, but looking in the specs, at the standard 12 volt level it only produces 4x12 watt, that is a huge difference and for 4x22 watts it needs 14,4 volt. 

I know that my battery has a voltage of about 13 volt, with running engine. And probably in the interior at the back of the radio it will be less due to resistance in the wires. 
To overcome this, I want to have dedicated radio wiring from the battery directly to the radio : + and -. So I have ordered a few meters of 6mm2 red+black wiring and fuse, next week I am planning to feed the wiring from the battery through an unused bulkhead rubber grommet, and from the inside the wires can be picked up behind the glove box, and from there to the radio. 
Hopefully that will to the job, otherwise I must look how the get the battery voltage to the normal 14,4 volt, or get a radio with better specs, or install an amplifier that really works at 12 volt. 
New pair of wires is for now the easy option. 

 

Ugh! This is going to be  a bit difficult. What is a Watt? What is an Ohm? a 50 Watt output might be about 10 Watts RMS, the only proper measurement. 4x22Watts is actually almost indistiguishable from 4x50Watts  as you should know. Assuming a modern class D amplifier, you will be drawing four Amps at least from the supply at 12 Volts. If you are running off a bench power supply, it will need to be adequate. Are you running into the correct speaker impedance? Have you taken the door cards off  and the T-bar cover likewise and checked the condition of the speaker cones? I have often found them to be pretty tattered. How are you measuring the distortion? Bruel and Kjaer distortion analyser or a scope on the speaker leads? What are you using as a load for these checks ? What is the signal source? Signal generator set to line level?  I doubt VERY much if there is anything wrong with the Pioneer kit. I use it myself in my car and it sounds fine. If your battery is not going flat then the  voltage is correct anyway. Why do you think that something is wrong?  If you are getting distortion, you have either poor speakers or poorly made power connections. The nominal alternator voltage will be over 13.5 volts at the radio's power terminals with the engine running.

Just a note - healthy alternator should produce from 14.1 to 14.4  Volts. 13.5 Volts from running alternator is on the low side, alarming that you might have either higher resistance on alternator terminals and needs cleaning or alternator is on its way out

It should be but allowing for voltage drop through the ignition switch and the usual spindly  connections  to car radios, a hard working  set can easily pull the supply down half a volt at its terminals. it only takes .1 of an Ohm at 5 Amps to do so. after all. I would expect to see above 14 Volts on mine as I use good cable and connectors. (Not the hyped up trash for the gullible, thirteen Amp mains cable is entirely suitable for a hundred Watt load.)
I expect that the unit has been turned up to max and wrecked the factory speakers, if I'm honest..