Non-DSP audio upgrade

[sleuth255]

The idea here is to install the DSP Nokia sub box along with a separate amp to power it. This relatively low cost mod will add more bass to the stock system which comes up woefully short in this area. Everything else isn't too bad. The non-DSP amp has a 4 channel output with each front channel delivered separately to high, mid-range, and bass drivers while each rear channel is delivered separately to high and bass drivers. All four bass drivers (two in the front doors and two in the rear deck) are actually handling low-midrange audio but their response really drops off below 40Hz or so. I'm simply going to extend the range a bit lower with this mod.

The Nokia sub box consists of a pair of 8 ohm DVC drivers in a tuned port enclosure. Each voice coil can handle 45W so the entire DSP system delivers 180W at 8 ohms. I'm going to drive it at 2 ohms which means my amp will need to deliver about 400W.

After a quick search through the Crutchfield catalog, I ended up choosing a Soundstream Reserve RSM1.2000D sub amp for this project. It can deliver 480W at a 2 ohm impedance, has a remote power-on feature and adjustable output power along with some pretty comprehensive bass trim/eq controls. Its also the perfect size to go where my 6 CD changer used to live.

[sleuth255]

The rear deck on my 2003 530i has already been pre-cut with mounting holes pre-drilled for this sub enclosure (and also for M-Audio subs). All I had to do was remove the knockouts for the sub ports. Even the sound insulation pad on the other side was precut! So I didn't even need to remove the rear deck.

[sleuth255]

First off, I bread boarded the system together so I could check wire sizing, test out the enclosure, and also pre-adjust the power-amp output. The amp itself appears to be perfectly sized; I was able to drive the enclosure at near maximum power with no noticeable distortion. I'm using the stock enclosure connector and I also took a pic showing how to wire it up for 2 ohm impedance:






Using the CD player shell as a temporary mount it but the final plan is to cut out a custom backing piece that will hold not only the amp itself, but also my BluBus audio module.

[sleuth255]

Waiting on parts currently: fuse block and 8 gauge wire for power, a spool of 12 gauge wire for output, and some BMW mounting parts. This should all show up by Monday and I can connect it up. I'm actually planning to bring the line output from my BM54 radio into this amp. Mine has the newer square connector so I'll take 3 taps off that for line out left, right, and ground. they're on pins 1,3 & 7 of the "B" connector:

[kallekula]

Interesting to hear if it’s some bang in that box. I threw it out and replaced it with a 12” closed and powered Rockford Fosgate. Lost some trunk space but it has a quick connect and is easy to remove if i need to. Keep us updated! Think the Nokia has two 6.5” elements? Definitely gonna save trunk space if it works to you satisfaction.

[sleuth255]

I'm just looking for something better than the (non-existent) bass response from my stock non-DSP audio. I'm thinking I can tweak it pretty effectively with the amp which has tunable low pass and sub bass filters along with adjustable boost. Also looking at pictures of other people who have disassembled their Nokia sub boxes and I noticed the port cavities were filled with some sort of white stuff that looked like white insulation. Mine was made in 2003 and the ports were open. Not sure why anyone would fill a tuned port with anything. I'm also planning on using my spectrum analyzer to help tune it and also look at overall frequency response once I've got it in the car. If all else fails, I can go to M-Audio subs with this setup. The speakers in the nokia box are 5" DVCs. Pretty hefty magnets and very respectable cone travel too.

[kallekula]

Hope it works out for you. The RF I bought was only $300, good alternative if you’re not happy with it.

[sleuth255]

I've got my fingers crossed. I've got about the same amount into my project as well. Which brings me to today's tasks, first of which is to baseline my car.

So, how to tune/test audio response? Why do what old-school audiophiles do of course: use an audio spectrum analyzer. My spectrum analyzer runs on my iPhone and I'll use my PC to send a white noise audio file to my car's AUX input. The lossless WAV audio white noise file contains equal components at all frequencies form 20 - 20K Hz which makes it the perfect test pattern for this exercise.

So here's the baseline analysis of my car's audio and all I can say is "Yikes!" Bass was predictably lackluster below 500Hz but the drop-off at 8KHz is massive! Almost appears to be an intentional filter from the stock amp. To make sure of this, I analyzed the sound coming from my PC itself and response was remarkably flat in that area. Trying to tune it out with the car's frequency controls had no real effect either. Looks like my DSP emulation project has just taken on a whole new significance.

I'd really be interested to see somebody else perform this test in a DSP equipped BMW. The white noise WAV file I'm using is a free download at Big Soundbank and the spectrum analyzer I use is called "Audio Spectrum Analyzer Pro" in the app store. Search for "audio spectrum analyzer" and it will come right up.

[kallekula]

I tossed all bmw original modules and put brand new stuff in, even speaker cables. It’s possible to put back the bmw stuff without problem, didn’t even jack in to any existing cable. It’s a complete separate system and it sounds beautiful.

- - - Updated - - -

That white stuff has some acoustic effect, not sure what im no expert. It sits behind the 5.25 elements in the doors too.

[TiesTorN]

you'd be surprised how much bass that nokia unit could produce when it was brand new. these things deteriorate over the years. 99% of people saying that it is not enough are actually commenting on its deteriorated state. my nokia unit was exactly like that. I was always thinking "is this supposed to be the mighty dsp? it sounds like crap!"

then I decided to restore the entire (stock) system. replaced worn out parts... new diaphrams, cones, isolations, fix air leaks etc. you couldn't believe the difference it made.

[sleuth255]

If either of you two would like to run a spectrum analysis I'll buy beers... Really interested to see what the DSP baseline as well as a full replacement looks like...

Anyway, on to today's construction project. Mounting the amp/BluBus modules. Its actually quite simple using the CD player as a template. Everything fits right in. Just needs a coat of flat black..

[sleuth255]

Moving over to the other side of the trunk now. The plan here is to install a new unloader relay that will switch 30A over to the sub amp when IGN is on. BMW Green relays are 30A so I'll be using a spare slot on the trunk fuse block for it. Not sure if I'm going to need to go up to 40A or not. The breadboard test showed everything drawing well below 30A. So I'm building connectors while waiting on parts currently; lots of stuff (wire, mounting hardware, connectors) arrive tomorrow....

Its a real pain to crimp 8 gauge wire!



...building the sub connector...

[sleuth255]

Spent time researching BMW relay ampacity values today. Looks like the light green and pine green relays are actually good to go up to 50A. This is excellent because it means that I can tap power for my sub amp off an unused 50A fuse in the fuse block above the positive battery terminal. I've posted a pic of this below. I'll need to crimp a 1/4" ring terminal onto my power lead and also cough up a M5x.8 nylock nut to hold it on, but everything else is already there. From there I'll go to a new unloader relay mounted in one of the spare relay slots on the trunk fuse block, then over to the sub amp. Unloader relays are designed to provide 12V IGN switched power to accessories except when the starter motor is active. The rationale here is to provide maximum battery reserve power to the starter motor when its needed. Since a sub amp can draw 40-50A, this is absolutely critical to have if the car kills say on a set of railroad tracks and an express train is bearing down on you. So many people don't do this when they put in aftermarket sub amps.... I wonder how many of them ended up in a no start situation when they needed it the most.

Now there are other ways to do this of course: All of the audio components in the electronics bay are powered by an unloader relay in position K3 so it would be fine to switch the sub amp power off sensed output for speaker level inputs (test how fast your sub amp responds here; it has to be instantaneous) or better yet, connect the sub's remote power input to an IGN wire there. However, a separate unloader relay isolates always hot +12V to a short run going only to the fuse box in the electrical bay instead of having an always hot lead capable of drawing 50A running over to the other side where it can potentially be chafed through over time. Call me AR I guess...

[JimLev]

I didn’t use a relay, my sub turns itself on/off when it senses the present of an audio signal.
Nice Klein crimper.

[sleuth255]

Its pretty handy. I considered just powering my sub from IGN on the electronics side (it has a remote power input that turns on the amp when it senses 12V) but just couldn't get past having an always live 50A capable +12V cable terminating there.

[kallekula]

I have that audio sense thingy on my sub too but for some reason hooked up to the remote-on cable since it was already there.

[sleuth255]

Whatever it takes to get the sub amp to kill when you turn over the motor...

More installation work today. I mounted the nokia box and connected the electronics bay power/speaker wiring. I'm using silicon insulated 8GA for the power connections. Its really flexible and easy to work with! I must say I'm glad my car has fold down seats though... Made the physical sub-installation work a lot easier! Having a 15" tall box (the thing with the art supplies) to prop it up with helped too. Next up is going to be tapping the line-out left/right channels and wiring up the inputs followed by a power-up only test. My relay mounting bracket shows up on Thursday.

[sleuth255]

My relay mounting part showed up today



sooooo (new relay is light green, 8 gauge red wire is power feed)....



Its ALIVE!!!



Getting close now: all that's left todo is wire positive relay trigger to IGN then tap into BM54 line out for RCA connectors. This is possibly the toughest job; its hard to tell if there really is line out where the diagram says it is. Lots of conflicting info on the BM54 square connector pinouts. If necessary, I can patch into audio out at the amp but I really want to pick it up from the head unit instead. Finally, clean up the +12V run going through the spare wheel well. Its been properly wrapped but needs to be wire-tied in place. Still waiting on a short 3.5mm male-male audio cable to connect the remote to the amp which will be here on Sunday.

[RosieE39]

I'd really be interested to see somebody else perform this test in a DSP equipped BMW.

Here you go.
(The only thing is I’m using a Siemens CID radio in my car instead of a BM53 or the original C23BM)

[sleuth255]

Awesome. Many thanks! Its clear to see how much better the DSP solution is. I'm going to be very interested to compare my low end after-installation results to this. I already know that I have more work to do to fix my high-end drop off. It may actually be driver related. Tweeters don't necessarily hold up well over time. Or it could be as simple as spraying contact cleaner on the poweramp output connector. Or it could be my non-DSP amp itself... Maybe I can locate somebody with a non-DSP E39 to try the test with.

edit: Just noticed that your car is an M5 so this would be the M-Soundsystem audio profile. Best stock system and actually pretty impressive. M-Soundsystem adds enhancements to mid and high-end audio drivers as well. I've been considering replacing my rear deck speakers with the dual driver components from this audio option group.

[RosieE39]

edit: Just noticed that your car is an M5 so this would be the M-Soundsystem audio profile. Best stock system and actually pretty impressive. M-Soundsystem adds enhancements to mid and high-end audio drivers as well. I've been considering replacing my rear deck speakers with the dual driver components from this audio option group.

It doesn’t have M Audio - it’s a ‘99 with the std DSP and the Nokia Sub box.

[sleuth255]

Thanks for the clarification!

[sleuth255]

So I was able to tackle the remaining tasks today. Powering the new unloader relay is simple. Just tap the Purple/Red IGN wire for the existing unloader relay that's right next to it:



Getting line audio to the sub was a bit more complicated. It turns out that the diagram showing line out on BM54 square connector's "B" plug is incorrect. When I inserted three pins into the unused connector slots 1,3, & 7 I got nothing. Too bad as well because that would have made for a very professional install. So I ended up tapping off the line level speaker outputs. The BM54 sends 4 channel line-level output over to the power amp on the "A" connector pins 1 - 8. I tapped the 4 rear speaker outputs on pins 1 & 5 (brown/orange & blue/black) along with pins 4 & 8 (yellow/black, brown/orange), spliced them onto two RCA phono plugs and plugged them into the sub amp. You can see the RR splices in the pic:



Finally, I disconnected the power amp connector (always a chore), and sprayed it down with contact cleaner. Then I fired everything up and I'm here to tell ya, the results were no less than spectacular! I was easily able to tweak the sub output range with the amp controls using the spectrum analyzer and white noise generator.

But don't take my word for it, here's where it ended up (bass control dead center, treble control at about 65%):

Before upgrade:



After Upgrade



So there you have it. For about $350 in parts and some dedicated DIY electrical work, an E39 non-DSP audio system can be taken up to the factory DSP system spec.

[philly98540]

That’s pretty innovative and impressive fix for not a lot of cash! How does it sound overall? Is the base crisp and decent punch? Any rear deck funky noises?

[sleuth255]

I'm really happy with it. No rear deck buzzing at all (was worried that I'd have to take the deck apart and stuff in insulation). Bass is really crisp to my ear, and with the low pass filter set at around 200Hz the nokia took over very smoothly from the stock rear deck drivers. I'm not throwing much power at it either.

Bass is always subjective though. I like it clean and not overpowering but at a level where you can feel it. I'm definately not a fan of the big kickers that you can easily hear in a so-equipped car when it pulls up next to you at a stop light. However I really think that this solution could easily be tweaked with the amp controls to send the bass in that direction though. Drop the low pass filter down to 40Hz or so, twist up the subsonic boost then adjust amp output to taste. The Nokia box is a pretty good ported design example IMO. Running the VCs in parallel for 2 Ohm overall impedance also matches it well to a modern class D sub amp.