1998 Audi A4 (B5) Budget SQ install, pics and plans! by brandontw

By diyauto
( 4 )

18 minute read

1998 Audi A4 (B5) Budget SQ install, pics and plans! 

Compliments of brandontw @ www.diymobileaudio.com


So, ive got a 98' Audi A4, came with the Bose system from 14 years ago when i got it. It sucked. Swapped out the head unit right away when i got it, cheaper JVC unit, decent-ish, and put in some speakers i had around just to hold me over while i figured out what i wanted to do.

I thought a bunch and decided how much work i wanted to put in, and how much money i wanted to spend, and came up with a plan for a better system.

Phase 1 will be running the 6 channels of RCAs, some 2 Ga power wire i had laying around, along with pertinent speaker wire. I'll also be building a nifty little combo sub box/amp rack that will bolt up to the underside of the deck and hang down in the trunk 8" or so. The sub will probably be an 8" Alpine Type R. The amp will be a Clarion APX600.5

Phase 2 will be building some kick panels, and installing some still un-purchased mids in them, and tweeters in the stock locations. They will be running active straight off the Clarion APX600.5

Rear fill off the head unit perhaps.

So anyway... Lets get to the building.

My amp was about 16"x9"x2". I wanted to get a box around .6 Cubes, ported, tuned to around 33-35Hz, and i wanted it all to fit in my trunk with very little space sacrifice...

So i started looking around in the trunk and decided i was going to try to put it on the underside of the deck. I figured i could fit my sub enclosure, and amp all in a fairly compact package up under there. So i started planning and designing:

Ill spare you the whole process, but i ended up here:

This is a screenshot of the design in inventor so you can see that the ports actually extend into the chamber a bit.

This is what it will look like roughly when i'm done, I'm planning to bedliner it black, that silver thing is a rough mockup of the amp... should fit right in there:

So lets build!
I cut the whole thing up(with a skill saw!) and mocked it up to make sure it looked kosher:

I used a hole saw to cut out the 4 holes for the ports... the fit is nice and snug, and they line up good. I also used a jigsaw to cut open an opening that i could get to the adjustments on the end of the amp so i wouldnt have to unbolt the whole thing to change my gains:

Then i went ahead and glued it up and screwed it together and test fit the tubes:

Fits good! lets glue them badboys in!... I roughed up the spots where the glue would go with some sandpaper and used epoxy and just twisted them in. I inset the ends about a quarter inch to give me some bondo room:

That's as far as i got today... next up is cutting those 2 pieces to close up the box, cutting the hole for the sub, Bondo, sand, bondo, sand, and route off all the edges with a quarter round. Then bedliner....

Other note: I plan to use a somewhat fancy mounting system to both isolate the whole thing from the car, and to isolate the amp from the sub enclosure... rubber washers, through bolts... haven't worked it all out yet, but just in case you were wondering...


Well, ive already got some Dayton RS-180's in the mail (7"), and started moving all the wires out of the way yesterday, so i dang well hope i can fit them in there, and im going to do my best to not intrude on my foot-room too much, but we'll just have to see how it goes. Its an experiment after all...!

In case you haven't seen... here's a semi-usefull A4 kick panel thread...
Fiberglass Kickpanel Tutorial - AudiForums.com

I say semi-usefull because i have no idea how he moved all of those wires that far out of the way. I did my drivers side yesterday and it was at least an hour of cussing, and "wtf am i doing" moments, and my results are not as good.

As far as progress on the subbox/amp rack.... Its still underway! i got it sealed and rough bondo last night, and i have the day off today, so ill be sanding that, as well as running my RCA's & speaker wire down the passenger side. I ran my power wire from the battery, and one speaker wire fro the front door down the drivers yesterday. What a pain! Gotta love audis...

More pics hopefully tonight


First task that got done... getting the 2 Awg power wire through the firewall. I ended up drilling a hole into the box that hold the ECU, and dropping the wire right down behind the carpet... worked nicely. Then i sealed it up with a generous amount of silicone.

I started to dig into the wires on the drivers side. There is a huge bulky connector filled with other huge bulky connectors and i spent forever disconnecting every one, removing the connector-housing, and reconnecting. You can see the 2Awg wire coming through the ECU area into the cabin.

Right about here i got to a "WTF am i doing?" moment:

Got them all disconnected and out of that black plastic cage:

Passenger was pretty much the same but without the deadpedal to hide the wires and connectors under, it actually worked out better:

Drivers side with wires as moved as i could get them, with some tape for now to keep me from messing with the connectors with my feet not very satisfied with how far i got them moved, but i really dont see a way to improve it for now, i think it will work:

Anyway, so I got my power wire run, along with the run of speaker wire for the kick and tweets, then moved to the other side and ran the speaker wire and 6 channel RCA (i only got a 12'er... its to short. I guess ill just use some extensions. Stupid.

Ok... so anyway, back to the sub box project:

I sealed it up, cut the hole, sanded some, then bondo'd then sanded some more...

Then i test-fit it in the car... it fits! I picked some mounting holes that were already existing, drilled them and countersunk them.

Im working on a combination of hardware that will suspend the box a bit down from the deck, and isolate it from the deck, i found some rubber stoppers, drilled holes in them, and will use them in conjunction with 1/4" bolts, nuts, washers, and pieces of sound deadener turned into "washers" to mount it, hopefully rattle-free.

Then i primered it:

Then i used spray bedliner from wal-mart (7.50 a can or so) I used 2 cans

A few regrets about this bedliner:

1. It doesn't cover near as good as i thought it would. I would have sanded A LOT better if i would have known that it would show off my laziness as bad as it does:

2. Its really touchy stuff. You want to get it on there thick, but if you go too thick, it will start running. I learned a little too late to hold the can further away and do lighter dustings.

3. Ventilation! I did it in my garage with the big door open, and with one coat of primer, and 3-4 coats of bedliner, my floor had a dusting on it, along with everything else in the garage. Plus my head wasnt feeling to great. Haha. Its probably a good thing i dont do this type of stuff all the time.

Some parts turned out ok, others you can see my construction flaws (i cut the whole thing from scrap wood i had laying around, and with a skillsaw) So all in all, i think it looks OK, it will serve it purpose for now, and look mediocre doing it, and that's fine with me. I may end up re-doing the whole arrangement later on.


Well, i got a bit more work done on saturday, then an sudden ski trip got in the way of further progress, but i got a little work done on the amp rack (no pics yet) and got the initial lay-up done for the kick panels.

Tape job:


Tape peeled off and speaker mocked up just to look at. they are big drivers! its gonna be a squeeze!

Passenger side similar:

A lot more room over here... less wires to move, no deadpedal, and no hood latch. this one should be no prob.

Well, thats all for now, this week im hoping to make some speaker rings (I may have to jigsaw them  thats gonna be fun. and finish the speaker pods.Then ill be figuring out the mounting for the tweeters, and hopefull will be fully installed, finished, and operational by next sunday.


Well, im back at it... Put in entirely too many hours on the kick panels last night.

Disclaimer... This whole this isn't turning out quite how i expected, as expected.

So far my biggest disappointment is how bulky they are gonna be. I knew they were gonna be big, and i chose big speakers, but dang! the things i do for good sound...

Smaller dissapointments are my build quality. Ive never done a project like this before, so im not being to hard on myself... but F! this fiberglass stuff is pretty hard sometimes. The initial layup went pretty good. Trimming it down was a nightmare. I ended up using a jigsaw, combined with my (useless) harbor freight dremel tool.

Then getting my rings into position was even worse... they had to allow the speaker to fit without hitting bottom on the fiberglass, clear the door closing, clear the hood latch handle, and not look to retarded... I dont mind them too bad, but they arenet pro quality whatsoever. I guess we'll see when i get them finished.

Ok, pics:

Cutting out my rings, trusty ole' jigsaw and sand. I didn't worry a ton about the inside and spent more time on the outside edge.

Mocking up the rings... i used hot glue and chunks of paint stir-ers from Home depot. Trial and error, and error, and trial:

What i finally ended up with:


I chose bright orange fleece. Not sure if it was best for the job of not... but it stretched fairly nicely, except for one spot where i noobed it.

Slime them up and hit the sack

This morning they were hard and sturdy. On tonights agenda is adding fiberglass. I was thinking i'd try to do it all on the inside so i can keep my semi smooth surface... we'll see.


Got the inside fiberglass done last night and bondo this morn... they are starting to look like speaker pods!

Sanding, trimming, and painting tonight! Along with jamming the Morel mdt-12s into the factory locations.

And tomorrow... install all day!Is anybody watching this? Haha


Ok... well 10 hours yesterday and another 3 today and its done... for now.

Im just gonna trow some pics up real quick and bail. im headed to the ocean for a victory lap/ tuning trip.

They should be fairly self explanatory. Ive got a few more pics of the install process and ill answer questions if there are any later on.

Anyway.. let me know what you think! and ill let you know how i think it sounds in a bit when i can wrap my head around it.

Dirty sub from underneath:

The seats still go up!

You can see it with the seats down...

Passenger mid view from drivers seat:

There are Morel MDT-12s hiding back there in the stock locations

Left mid:

Left mid with my big foot in there next to it. Its definately less roomy than before but i think i can live with it. I definately need to get some grilles figured out or im gonna trash those speakers tho.

Amp rack and sub from the back:

I sure was wishing i gave myself an extra inch in the design when i was making these connections:

Amp from underneath:

Ok, thats all for now... it works! That amp leaves a bit to be desired... my left side wasnt working at first, and i had to get in there an mess with the switches on the back of the amp untill it started working. :/ Future upgrade opportunity? i think so...

Initial impressions. sounds good. ill let you know later.

To the ocean!


Ok... more from me again.

I'm calling this install failed for now...

The Clarion amp has some sort of little quirk where i cant get the left side to work properly when the bandpass filters are enabled.

The switches are on the back... And the back of this amp is VERY hard to get to in this install.

Im just going to go ahead and give up on that amp for now.

But the problem is, the options on that amp (BP crossovers) allowed me to go active, And i dont have any other way to process the signal right now... im just using a cheap JCV HU.

So, my Revised plan is thus:

Sell of the cheap JVC HU, Replace it with JVC Kd-sh1000 that i just found on here from a member last night. This is an active capable HU that i got for a great price from a member here at just the right time.

Sell of the iffy clarion amp (make me an offer if you want it, its supposedly a decent amp, ARC guts, its just need fiddling that i cant handle right now.)

Purchase a different 5 channel... and with the space restrictions ive created for myself, that pretty much limits me to some of these new full range class d amps. So, im in the process of looking now. Hopefully i can get this install working sooner than later...


Oh, well i've got a JVC KD-SH100 In the mail, ordered a Kenwood XR-5S Refurb for the amp.

Sold the Clarion amp to a member here for cheap, and requested an RMA from crutchfeild for the cheap JVC i bought from them last month.

So... total additional investment: More than i wanted, but less than i feared.

Now the waiting game, and another install day to come...

Well, an update... I got my JVC sh1000 and my XR-5S in the mail last night. So after work i got in there and wired all that stuff up (somewhat sloppily) and got it working.

A bit of a sigh of relief was had, because everything worked, and sounded fairly decent on my initial test setting, and slightly more decent with another 5 mins of tweaking... When i can get in there and do some serious tuning I think ill be pretty happy with the setup.

Also... i'm working on getting some custom speaker grills for the RS-180's made.

Heres the thread for those if anybody wants to chime in:


Figured i'd add the speaker grills i got made for them to the build log...

Drew them up in Inventor and got them laser cut from Stainless Steel. 30$ for the pair....