Car radio question.

[Roscoe458]

My 2002 Z3 has two amps. one to drive the speakers, and the other for the sub. My question is if you install an after market head unit. Does the after market head unit's pre amp even do anything, is it just wasted?

[Blacklane]

By definition, the pre amp drives the power amplifier(s).

Most head units have modest power amplifiers built-in. Those are strong enough to drive speakers, or they can be used to drive separate power amplifiers that have "Line" inputs. The negative side of that idea is that any noise out of the head unit amplifier gets further amplified in the power amplifier, and head units tend to have somewhat poor Total Harmonic Distortion. However, it's hard to get as bad as the BMW head unit and amplifier with an astounding 10% THD. Most aftermarket head units and amps are around 1.0 to 0.1% THD.

The pre-amp outputs from a head unit are simply output connections between the pre-amp and the power amp sections.

The preferred method is to use RCA cables out of the head unit pre-amp to drive a healthy power amp. That should provide good sound reproduction. In that case, yes: the head unit power amps do nothing. However, they literally cost pennies to incorporate.

[Roscoe458]

By definition, the pre amp drives the power amplifier(s).

Most head units have modest power amplifiers built-in. Those are strong enough to drive speakers, or they can be used to drive separate power amplifiers that have "Line" inputs. The negative side of that idea is that any noise out of the head unit amplifier gets further amplified in the power amplifier, and head units tend to have somewhat poor Total Harmonic Distortion. However, it's hard to get as bad as the BMW head unit and amplifier with an astounding 10% THD. Most aftermarket head units and amps are around 1.0 to 0.1% THD.

The pre-amp outputs from a head unit are simply output connections between the pre-amp and the power amp sections.

The preferred method is to use RCA cables out of the head unit pre-amp to drive a healthy power amp. That should provide good sound reproduction. In that case, yes: the head unit power amps do nothing. However, they literally cost pennies to incorporate.

Thanks Black, so if I'm understanding correctly if I installed a new after market head unit, and it pushed 40 Watts RMS per channel like the Sony MEX-XB100BT. Would I be able to use that power along with the BMW factory amp towards the speakers where it would not be wasted/lost? Sorry I'm kinda new to these things.

[z3forlife]

It's totally wasted. The head units are actually fairly clean it's the amps that have high distortion ratings. I used the factory head originally and it sounded great through a good quality amp. The only real improvement was switching to line output via rca cable...but then you have to replace the amp. I'd keep the stock setup and look for a interface that uses the cd changer input and ho with some poly coned speakers to keep things simple but full upgrades are not that hard on these cars.

[Roscoe458]

It's totally wasted. The head units are actually fairly clean it's the amps that have high distortion ratings. I used the factory head originally and it sounded great through a good quality amp. The only real improvement was switching to line output via rca cable...but then you have to replace the amp. I'd keep the stock setup and look for a interface that uses the cd changer input and ho with some poly coned speakers to keep things simple but full upgrades are not that hard on these cars.

I already have a Kenwood HU that came with the car. Never had the original radio unfortunately. When I play through the blue tooth in the car it actually sounds decent. All highs though with not much bass. If I wanted to keep it simple, could I just put this behind the passenger seat for a little extra kick since I already have pre amp outputs?? https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

What's your opinion?

[z3forlife]

That should do the trick if you have the room and a means to connect. You should have the stock 6-6.5 " sub which does a decent job. I went the 8" sub in stock location route with a alpine amp powering all.

[Blacklane]

Do not drill holes behind the passenger seat. The fuel tank is right there behind the back wall of the cockpit.

[CoconutPete]

The roof of the trunk should provide a decent mounting spot for an amp. You have the mat that the top folds onto on the other side of that.

I'm wiring mine up right now. I'm powering the small 4" rear speakers off the headunit and using a 4 channel amp for the front component speakers and the sub.

[TommyMaddox]

I already have a Kenwood HU that came with the car. Never had the original radio unfortunately. When I play through the blue tooth in the car it actually sounds decent. All highs though with not much bass. If I wanted to keep it simple, could I just put this behind the passenger seat for a little extra kick since I already have pre amp outputs?? https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

What's your opinion?

https://www.bimmerforums.com/forum/s...anger-location

I mounted my amplifier in what I felt was the best possible spot. Write up is in this thread, I took into account everything from cabin heating, footwell space, parcel shelf space, trunk location, wire routing, etc... when I chose that spot.