[loginfailed]

Hello all. Sorry in advance for the long post. I recently bought a used 2006 325i w/ 40k miles. I like the factory HiFi system for the most part, but I'd like it to have a little extra thump.

I had some products from previous cars so I thought I would give this a shot. I don't really have everything planned out. I'm just diving in and seeing where I end up.

The amp I plan to use is a Rockford Fosgate PBR500X1. The amp is designed to be run at 1-ohm for maximum output.

I have 2 different subwoofer configurations to use but have not decided which to go with yet. I'm open to suggestions. The PBR500X1 is rated at 500 watts RMS which is pretty much right at the bottom of the range of what the 2 subwoofer setups I have will require.

I have a single Alpine SWR-10D2 dual 2-ohm voice coil woofer which with the 2 voice coils in parallel will be a 1-ohm load. The problem is that the Alpine really needs more power than the PBR500X1 can deliver.

I have a pair of MB Quart RLP254 dual 4-ohm voice coil woofers which if wired in parallel will also be a 1-ohm load.

Right now I am leaning toward using the 2 MB Quarts due to it being more cone area and because I can build the enclosure to be more shallow than with the Alpine. But the Alpine is a much cleaner sounding sub. Im not really looking to wake up the neighbors, so going with the Alpine would be fine.

Again, I'm open to suggestions on which route to go. I'm not familiar with the E90 as far as what works the best. The trunk seems pretty well sealed from the cabin, so today after installing the amplifier, I started working on a vent where the arm rest is. My rear seat does not fold down so there is no pass through from the factory.

Here are a few pics of the amp installation and a few comments on how I did it. Maybe this will help some others who are thinking of doing something similar.

First, the car. Base model, with NAV and sport pkg 17" wheels:


There are tons of other threads about amp installs, but I'll go ahead and illustrate what I did. So basically, I unplugged the Hifi amp and disassembled the connector. These are the colors which I originally found in this thread

Originally Posted by crimsone90

SUB LEFT
Red/White +
Brown/Yellow -

SUB RIGHT
Red/Blue +
Brown/White -

I pulled the subwoofer wire pins out of the connector and untwisted them so I had some room to work. I then stripped back a a little section on each wire.


The plan was to cannibalize an old RCA Y-cable to make a set of female RCA outputs at the factory amp. So I started with this:


I cut the black part off and then stripped back the wires and was left with this:


I then attached the RCA cables to the factory wiring.


Soldered them together.


Taped them off.


The I put the pins back into their homes in the connectors. (HINT) I took a picture of the pins before I removed them from the connector and then used the pictures I took to verify I was putting them back in the right locations!


Harness back together.


Then I plugged the harness back into the factory amp, hooked a set of RCA cables up to the female jacks I just installed and ran the RCAs over to the sub amp, securing the RCAs to the factory wires with zip ties.


The amp location is under the trunk floor.


I marked where to drill the screw holes, removed the amp, mades the screw holes and put a dab of silicone sealant over each hole,


Then I carefully placed the amp over the holes and screwed it in.


The PBR500X1 is very small as you can tell from the pics. Its also plenty shallow enough as not to interfere when reinstalling the trunk floor.


I ran the power and ground wires both straight to the battery area, shielding them and the RCA cables with flex loom.


For the ground wire, I crimped on a ring terminal and then soldered it as well to ensure a reliable connection. Then I added some heat shrink to the junction for good measure.


I attached the ground to the battery.


For the positive connection, I chose this terminal. There is not enough room for the original cable and the amp cable and still allow the little flap to close. So there is some material that needed to be removed. See where the screwdriver is pointing to in these pics.



I used a Dremel tool to remove some of the material to make room so that both terminals could fit and allow the flap to close.


Now that everything can fit properly the amp wire went on first.


Then the factory cable and the nut.


Flap closes!


I just zip tied the fuse holder which contains the 80-amp fuse to the factory battery cable.


Everything all nice and tidy.


When I decided to do the amp install, I estimated that I needed about 12 feet of 8 gauge wire. So I went to the local car audio shop and bought 12 feet. When I was done this is how much wire I had left!

[loginfailed]

Here are a series of pics from what will eventually be the vent from the trunk to the cabin.

First I popped off the interior trim panel behind the arm rest.


The back of the seat has some criss-cross pattern to it, so I used that to make my hole by drilling the 4 holes you can see in the pic below.


I then went around to the trunk and used the 4 holes to make a square.


I used a jig-saw to cut it out from the trunk side.



Then I put the trim panel back on and used the hole in the seat as a guide to mark the trim panel.


Cutting a plastic trim panel with a jig saw does not work very well. The blade gets hot and then as you cut, the area behind the blade melts itself back together. In the end I used a razor knife to score the plastic until the piece popped out. Then I used a mini die-grinder to smooth it all out.


This it what it looks like right now. I'll have to go get some speaker grille cloth from the fabric store tomorrow so that I can finish trimming out the vent. I have a few ideas on how I want to do it.



Tomorrow I can hopefully build the speaker cabinet and finish trimming out the vent.

Thanks for reading! Comments, criticisms, praises, ideas, questions are welcomed and encouraged!

[Denny347]

I'm going to do this with mine. It will be an IB subwoofer set-up. I'll use one of the harnesses built by Technic to allow me to power the subwoofer and then add a separate amp for the underseats so I can cross them over as mid bass. I have to cut the rear seat for the IB. Looks good so far.

[WilliamS]

Looks good, I always love build threads it brings me back to my old installer days. Only thing I would have done different. This might be cutting hairs as once its sealed and out of sight its only ever known by you is I would have pulled the wire from the harness to use a shrink heat tubing instead of tape. Also custom RCA but using what you have worked just fine too.

Keep up the pictures.

Also have that same amp in my other ride, what a great little amp!

[kaigoss69]

The pass through hole is a little on the small side. Are you planning an IB install? What size sub?

[loginfailed]

So yesterday I had a little time to make a box. I decided to use the Alpine Type-R sub and do a ported box. The spec sheet from Alpine is a little confusing when it comes to vented box construction, so I decided to design my own. I downloaded WinISD and used it to design the enclosure. After taking into account the port volume, speaker volume and a double 3/4 front baffle the box design ended up at 1.69 cubic feet. That seems on par with the 1.3 that Alpine recommends since there is a giant port stuffed in there.

So I had a bunch of scrap 3/4" MDF laying around from an old cabinet I built in my garage that I tore down a few years ago. It was spray painted black and had a bunch of screw holes in it. So I decided to make this a budget box. No new wood. It won't be the most beautiful thing Ive ever made, but its going to be stuffed in the trunk. Here is the material:


I designed the box the night before on some graph paper and had all of my cuts figured. So the cutting process went pretty quick. Here are all of the pieces ready to assemble:


I didn't take many pictures along the way, but hey its a bunch of MDF glued and nailed together. I did manage to take a couple shots of the port design before I closed it up. I wish I hadn't forgotten to router the edge of the inside end of the port, but oh well.





I went through a long process with my belt sander, sanding off all of the old black spray paint and smoothing out my shoddy craftsmanship. I think it came out reasonably well considering my sloppiness, haha. I'm not sure what that stain is on the one side. I think some oil or something spilled on that panel at some point over the years it sat in the garage. Oh well, gives it character!



After softening the edges with a roundover bit and some MacGyvering to make a hole for the speaker. I sort of fudged up the port a little on one end because I'm an idiot and forgot how to operate a router I guess, lol. The holes you see on the front are only superficial since there is another layer of 3/4" MDF behind that.




The enclosure, though not one of best things I've ever built fits really well in its intended spot. Its just shallow enough that the trunk floor compartment opens and closes without any interference from the box.

The sound is pretty good. I ended up revering the polarity on the sub because the bass sounded a bit delayed, and that seemed to help quite a bit. I think I still need to experiment with the crossover to get it sounding as good as it can. Currently, the crossover is set at about 65hz. I'm thinking I need to raise it a little.

I went ahead and installed the little bass knob from the amp and ran it up to the front so I can turn it down when needed. On some music with deep bass, its just too damn loud. On other music, its not loud enough. The knob has helped with that.

The trim over the rear shelf, and on the c-pillars rattles on certain notes. I think some sound dampening may be needed. Its not that bad though and can only be heard at lower volumes. At high volume its not that noticeable.

Originally Posted by Denny347

I'm going to do this with mine. It will be an IB subwoofer set-up. I'll use one of the harnesses built by Technic to allow me to power the subwoofer and then add a separate amp for the underseats so I can cross them over as mid bass. I have to cut the rear seat for the IB. Looks good so far.

Thanks, I considered doing an IB setup and I still may do that. I like to tinker around and try different things.

Originally Posted by WilliamS

Looks good, I always love build threads it brings me back to my old installer days. Only thing I would have done different. This might be cutting hairs as once its sealed and out of sight its only ever known by you is I would have pulled the wire from the harness to use a shrink heat tubing instead of tape. Also custom RCA but using what you have worked just fine too.

Keep up the pictures.

Also have that same amp in my other ride, what a great little amp!

I probably should have used some heat shrink there, but I forgot I had any heat shrink tubing until later on in the day. The 3M Super 33+ is some really great electrical tape though, so I think it will be fine.

I have some nicer RCA cables to use, but I figured its most likely going to be only a temporary thing since at some point I would like to do a complete system replacing all of the speakers and maybe one of those 8-channel Match amps with the built-in DSP.

Originally Posted by kaigoss69

The pass through hole is a little on the small side. Are you planning an IB install? What size sub?

I keep thinking the same thing about the hole. Most likely I will enlarge it before I make the grilles to cover the hole. I considered IB, but not sure the amp I have chosen will be enough power. Maybe at a later stage, I may try some different setups, IB being one of them.

[cdgatti]

I see for the signal you are getting the speaker level outputs from the hifi amp. I believe that is 40w/channel. It is unusual to put that much power through rca connections to an amp input. Most people would use a LOC for that application. Have you checked if you sub amp works? Editing - I looked at the spec sheet for your amp, it does allow for high level inputs, you are probably ok.

[loginfailed]

Yes, that is correct. I'm catching the signal on the output side. Like you said in your edit, the PBR500X1 accepts low level or high level on the same input. There is an adjustable LOC built in. All you do to enable high level input is press the little switch. Then use the little potentiometer to adjust input sensitivity. The gain control is a separate knob from the LOC sensitivity.

Here is a detail pic of that portion of the amplifier:

[loginfailed]

OK, so kaigoss69, you got me thinking about an IB setup. I'm really not that satisfied with the way my ported box sounds anyway and its pretty damned heavy and takes up too much room in the trunk.

So today I started tinkering a bit with making a baffle. Im sure a 12" or 15" would be better, but for now I'm going to see how my Alpine 10" will work out in IB firing directly through the arm rest hole.

So I cut out a bit larger hole in the back of the seat, but still kept the mounting holes for the arm rest hole trim:


I started with some USPS flat rate boxes to make a template:


Once I was happy with the fit, I traced it onto a piece of 3/4 birch plywood. I decided to go with birch this time around because its pretty strong but quite a bit lighter in weight. Its a lot less dust when cutting too vs. MDF:


Once I cut the shape out, I brushed on a coat of wood glue:


I then nailed the cut out piece to another piece of 3/4" birch for a total thickness of 1.5". Should be pretty strong!


Then I used the router to make the 2nd piece match the 1st piece. I also ran a round over bit on both sides so it slips into position in the car without gouging the trunk liner:


This is as far as I got with it today. I'm pretty impressed with my handiwork, the way it fits in so snugly.

I have a few ideas I'm kicking around on how I want to mount it to the back of the seat. But first I need to cut the hole for the speaker. Maybe I'll get some more garage play time tomorrow and get it in there and playing to see how it sounds.

[bmw325i]

The main problem is your bass is trapped in the trunk. I'm sure ib will work better for you even with the same sub since you don't have folding seats. Nice work so far I'm interested in seeing how it turns out.

[Rosetta Stoned]

What didn't you like about the ported box? Did you try repositioning it in the trunk, facing backwards, or would it only fit behind the seat as built? I know sedans can get quite a good low end bump with rear or side firing subs in the trunk and leaving that vent hole helps too. I've always wondered about IB setups though so like to see how that turns out for you.

[loginfailed]

Rosetta Stoned, the sound just never seemed right to me. The enclosure and sub themselves sounded great outside the car. Super loud and super clean. But like bmw325i above you said, the bass is just trapped in the trunk. The price you pay for such a solidly made vehicle.

[WilliamS]

Still great looking setup, I cant wait to see the finished product!

I know it would be a lot of work, but would a 4th order setup with the port coming through the ski pass have a huge amount of volume and accuracy.

2 sealed 12's will overcome the bass trap, Im going IB soon though and removing the rear seats completely.

[bmw325i]

Originally Posted by WilliamS

Still great looking setup, I cant wait to see the finished product!

I know it would be a lot of work, but would a 4th order setup with the port coming through the ski pass have a huge amount of volume and accuracy.

2 sealed 12's will overcome the bass trap, Im going IB soon though and removing the rear seats completely.

I have 2 12" Alpine Type R's in a ported box but I have them facing forward sealed off from the trunk and I retrofitted folding seats. They are powered by an Audioque 2200d. It works great since the bass is going exactly where I want it and no rattles at all from the trunk. With the seats folded up I usually keep the ski pass open.