use OEM AMP with 3rd party radio

[RZomerman]

I have a Tradesman from 2017. The previous owner removed the cheap radio and replaced it with a Sony AX8000 and some aftermarket amplifier.. the sound however is horrible and seems to be coming mostly from the small dashboard speakers..

I wanted to see if it would be possible to put in the premium OEM amplifier and connect that to the SONY AX8000 pre-out connections.. another option could be to go to the 2020 UConnect, but that is going to be a really expensive endeavour and the advantages are not that much I guess (current radio already supports CarPlay, backup camera etc etc)

 

[crash68]

The dash speakers if stock are wired in parallel to the door speakers, there is also a built in crossover capacitor on them. Chances are the previous owner replaced the door and dash speakers and unknowingly is overdriving the amplifier.
As for using the OEM amplifier, it doesn't work like a typical amplifier as the volume is controlled via LIN bus not a variable audio signal.

 

[Atcer2018]

Just like Crash68 said. The stock front speakers are an odd setup and the premium factory amp is not all that great. Your tradesman probably had the smaller 5 inch radio leading the previous owner to go aftermarket. The factory 8.4 radio and an aftermarket amp is a sweet setup for interfacing with the other factory systems but you state that the Sony head unit works well so all is not lost. Do you know what kind of aftermarket amp you have? Is it bi-ampable? In other words can it accept one channel input and produce 2 or 4 channels of sound. If it is capable run one front channel output from the Sony head unit to the amp and feed the four front speakers separately from the aftermarket amp. Drive the rear speakers from the rear channel outputs of the Sony head unit. The dash speakers are physically small and most small speakers don’t preform well when driven hard. Pull the front dash speakers and add a capacitor to each to block signals below 600-1000hz. Little 3.5 speakers don’t produce bass so cut those frequencies out and let the door speakers handle that. Does the system sound good at low volume levels?

 

[RZomerman]

hi!.. thanks for the quick response..

on low volumes it sounds more like the dash speakers are the only ones working.. so perhaps a capacitor might not be such a bad idea.. any idea on the type I should add?

The previous owner put in a Herz amp (I'm suspecting the HCP 4DK by the connectors).. which has all 4 inputs configured (2 front/2 back). Then there is also a Pioneer active sub (TS-WX130DA) with variable volume and cut off point..

perhaps I should take the pre-out from the herz and rewire that to a new amp to drive the smaller dash speakers so I can configure them for high output only?

Or are you saying to run the door speakers (4x) from the Herz amp.. and then the 2 dash speakers from the Sony head unit?

 

[Atcer2018]

hi!.. thanks for the quick response..

on low volumes it sounds more like the dash speakers are the only ones working.. so perhaps a capacitor might not be such a bad idea.. any idea on the type I should add?

The previous owner put in a Herz amp (I'm suspecting the HCP 4DK by the connectors).. which has all 4 inputs configured (2 front/2 back). Then there is also a Pioneer active sub (TS-WX130DA) with variable volume and cut off point..

perhaps I should take the pre-out from the herz and rewire that to a new amp to drive the smaller dash speakers so I can configure them for high output only?

Or are you saying to run the door speakers (4x) from the Herz amp.. and then the 2 dash speakers from the Sony head unit?

Your system is complicated. You will need to actually find the aftermarket amp. Investigate its specifications and determine if it’s the amp you want to use. Then determine the speakers you have in the truck. You’ll need to inspect them individually for damage including being overpowered and having damaged drivers. While you are doing this disconnect the sub, it’s just more sound and electronics being added into the mix. If you determine that all the speakers are functional and in good repair add in the front dash speaker capacitors. Some small 3.5 inch multi-way speakers already have capacitors added but you won’t know until you physically inspect them.

Lastly I suggested using your aftermarket amp in Bi-amp mode. You’ll have to find out if it’s capable of being used in bi-amp mode. An amp that can operate in bi-amp mode takes ONE input and makes 2 or 4 outputs. In reality you would take the four channel outputs from the Sony head unit and use only ONE of the front channels, say the left front channel output from the Sony. You run that left front channel to the high level input on the aftermarket amp and it produces FOUR output channels. You use these four output channels to power the front dash speakers and front door speakers. Now back at the Sony head unit you still have three unused output channels. You use the left and right rear outputs to power the back door speakers and just tape off the right front wires because you won’t be using it. Not all amps are capable of doing this so it may not be an option for you. Configured in this mode gives you the most power on the front speakers where the soundstage is created. The rear door speakers don’t do much except provide fill for the front speakers so running them off of the Sony head unit makes for the most efficient operation.