2005 BMW Z4 2.5i E85 Aftermarket Build Log/Install With Pictures

I purchased the car about a year ago & the first thing I did was completely overhaul the entire system. When I bought the car it did already have some audio upgrades which was quite convenient. It had an alpine bluetooth radio with mic installed, a kicker 2 channel amplifier and a set of focal 2 way component speakers(crossovers were hidden behind the midranges in the kick panels, pretty small). However what was interesting is the prior 2 way speaker install tapped into the factory bmw stock amplifier. It was quite strange.This car came factory with a 3 way speaker system in each door, two 6.5 "subs" behind the seat, and two 4" midranges above that. The car sounded terrible for several reasons:

1. The new focal's and tweeters were powered by the 2 channel kicker amp, but the factory midranges were powered off the head unit. (dumb)
2. I'm not even sure it was wired up correctly.
3. The stock subs are a complete joke.I mean everything was a joke, but still.
4. The kicker amp was like 10 years out dated and put something like 30w per channel

So as you can see, it did not sound good.

Pros: All of the amplifier wiring (the power/ground/remote, and 1 set of rca's was already wired from the front to the rear.

I ultimately ran another 4 channel to have 6 channels(even though at the moment I am only using 4) and I ran a 9 wire to the rear, even though I only needed a 5 wire.

I kept the 6.5 Focals to use as the midranges, threw in an old set of dome powerbass 3" midranges from an old 3 way set I had laying around, and seas neo tweeters. I found a really beefy 3 way passive system crossover from china with crossover points I thought would be suitable. The crossovers nearly weighed a pound! Total out of pocket cost for this 3 way setup was about $50 for the crossovers. AIYIMA LX GM1 3 way crossovers : US $25.45 18% OFF|AIYIMA Crossover Board Tweeter Midrange Bass SubWoofer 3way Frequency Divider Enthusiast DIY Car Modification Stereo Crossover|crossover board|bass board|diy subwoofer - AliExpress (I bought mine on eBay, cant seem to find them on eBay anymore)

I decided to swap out the older alpine unit for a Pioneer DEH-S6120BS that was about $60. Interestingly enough these newer pioneer units seem to be really darn good for the money. I'm still eyeing a DEH-80PRS though...I really don't think I need it though! Even though it is my all time favorite head unit.

I swapped out the rear 6.5" "subwoofers" with Skar Audio EVL-65 D4 6.5" Subwoofers. I wired these up to 2 ohms each. They were a DIRECT fit! I think I paid $60 each for them new. There's a couple of them on eBay refurbished now for $45 a piece. Considering the cabin is so small, this adds quite the punch!
Skar Audio EVL-65 D4 6.5" 400 Watt Max Power Dual 4 Ohm Car Subwoofer:Amazon

The amplifier I chose for this setup was recommended to me by one of the members here. It's the JAD800.4 4 channel. This thing is certified to put out 750~ watts @ 4 ohms, and nearly 1200~ watts at 2 ohms for all 4 channels! The footprint of the amp is also really small. I was looking for a recommendation to an amp similar to the PPI P900.4, apparently this is near identical. I paid $175 for the amp new: JAD800.4 | Full Range Class D 4-Channel Car Amplifier | NVX

Oh yeah, I ended up selling the factory amplifier on eBay for $350! Which seemed on the higher end of what they were selling for. I fully expected to sell this thing for closer to $200, so I'll take the win!

So I paid 175 for the NVX, 50 for the crossovers, 120 for the skar 6.5 subs, 60 for the new pioneer headunit, $40 for 4 more channels of rca and 9 wire. = $445
Re-used the focals, brought in older dome midrange & seas neo's(amazing tweeters)
Sold the stock amplifier for 350
So all in I paid a little over $100 to have a completely rejuvenated system properly wired.

I couldn't be happier with the results. If anything, I may add a larger subwoofer in the trunk at some point in the future. I just have not been able to figure something not only practical for space reasons, but budget friendly, and loud!

I also still have all of the stock speakers I removed to resell on eBay. So ultimately when I get around to selling those everything should pay for itself. Oh yeah, and the kicker amp sold for like $50-100 as well.

I've included a bunch of random pictures of the install here. If anyone has one of these cars and needs any help figuring anything out I will do my best to answer.

If anyone has any comments, or suggestions, I'm all ears. Always looking to learn. Thank you to everyone who has helped me over the years learn this incredibly fun hobby!

2nd set of pics

3rd set of pics

4th set of pics

5th set of pics

Seeing as I am running the 6.5" subwoofers off the headunit subwoofer RCA out, I am only able to use the LPF on the headunit, so I had to set the HPF with bandpass on the NVX amp. I've tweaked it over the last couple of weeks and I'm confident I have set it to a level where the subs wont bottom out with those really low frequencies...maximizing output where they really shine

With that being said, for $45 each, these subwoofers slam! (For what they are). The Z4 cabin is so small, it definitely fills up the sound more than I expected...

Most of my life I have run 15" sealed subs in hatchbacks. I wouldn't consider myself a "basshead", but I am a fan of larger subs, and have been known to crank it from time to time. It's unfortunate I wouldn't be able to go much bigger with such a small cabin. I think I could create a larger mounting bracket to fit 8" shallow mount subs without too much effort. I think that may be my next project sometime this spring/summer.

I would be going from the Skar EVL-65's to the shallow mount VD 8's.

Cone area Two 8" = 100~
Cone area Two 6.5" = 66~

That's a 51% increase in cone area, and an extra 400 watts of power (200w each woofer increase from the 6.5's)

6.5's Recommended Sealed Volume : 0.25 ft^3
8's Recommended Sealed Volume : 0.35 ft^3

Hmm.... I'd also be opening myself up to potential vibrations, and right now I have NONE!