Stock BMW head unit conversion to add RCA low level outputs !??!?!

[tominizer]

Ok, I've honestly spent hours trying to find an answer here to this by searching the internet and forums and I don't have a full answer. Either I missed it or I'm blind (?!!?) I want to know how I can use the stock head unit that comes with the car (has DSP) and get a set of full range RCA's out of it AND keep the Factory NAV operational (Mark IV). I want to keep the factory head unit and NAV but go aftermarket with everything else. I guess that means only eliminating the DSP amp. The idea is to get a pair of full range RCA's to my aftermarket processor (x-over, DSP, AUX in, etc) and I will take care of the rest of the system from there with aftermarket gear and wiring.


So far this is what I think I have found but I'm not sure. The stock head unit provides a low level signal pair to the DSP amp. That DSP amp splits up everything from there. So how can I snag that pair of low level inputs and stick a set of RCA ends on them!?! I need to understand wiring location and colors to tap into IF it's available and are these low level BMW inputs usable into an aftermarket setup if I put RCA end on them??


"IF" I can resolve this, I'm off to the races to having a audio setup that I believe shall make me smile again. I will not require any fading as I'm going with a 3-way front stage and a single big-azz free air sub in the trunk..... keeping it simple ......... IF I can get this last bit figured out.

[DennisCooper]

Hi,

What you need is a Signal Summing unit and then a Sound Processor which 'cleans' the signal up to provide an acoustically flat, voltage boosted, non distorted no matter how hard you drive that oem low RMS output amplifier - signal to be passed to your high quality amplifiers and speakers that are then all installed well and properly using good enclosures/baffles.

Have a read of this install in an E39 of a previous customer of mine (not for the audio, as this was done by a good friend at his local shop almost a decade ago now)

https://forum.bmw5.co.uk/topic/43926...t-saloonsedan/

The fundamentals of getting excellent sound in a BMW saloon are here, the customer wanted the sound deadening and show level aspects, but to save money you can omit those.

The signal summing unit will take the 'split' frequences output by the OEM DSP and 'Sum' them together to provide one full range signal. The Processor then cleans the signal up so that you get the 'best' signal if going this route. You can get a cleaner signal by 'extracting' the audio if you go the Intravee/Alpine Processor route which takes the signal prior to the amplification stage, it all depends on the level of SQ and spend you want. Both ways won't provide as good a signal source as an excellent car audio brand head unit say from Pioneer, Alpine, Kenwood, Sony etc and the Intravee/processor route starts to get significantly expensive. Have a look at the JL audio site, I think they do an all in one Signal Summing unit and Processor so should save you some cash.

If you want a 3 way setup in the front, you'll need to search for drivers that will fit in the OEM locations, there's not many out there at all. Morel do some small(er) soft dome Midrange drivers, but they're relatively pricey, so it'll depend on how you design the setup, if for excellent sound quality, then do consider them. An alternative is to build custom door builds that will allow 3 way front components to be installed and you can then tweak mounting angles etc for getting the best from them.

Downsides to this route is that you need to spend more money longer term keeping the OEM modules working. Each has multiple points of failure too, so fixes/upgrades will be done multiple times as things fail and over the last 5+ years, these failures are becoming more common. Also, if you want to increase fuinctionality, it'll be more spend as well.

Cheers, Dennis!

[tominizer]

Hey Dennis. Yeah I actually looked at that install in the E39 and did note they used speaker level outputs. Around that point I stopped. As noted I was wondering what if at all can be had with the signal prior to the DSP amplifier. If the BMW system is not "modifying/degrading" that signal, one should be able to get a good quality source from there. I've found once an OEM system starts manipulating the signal with x-over points, sound fields, EQ-ing, then it's a bit of a lost cause and I'd then move towards a complete aftermarket. I'm still on the fence right now though as I'm still unsure of these original head units and what's happening before the DSP unit. Is the signal in normal wiring that can be tapped into or part of the BMW BUS system or !?!?

The ONLY reason I'm thinking of a OEM head unit is to keep the original look. I don't like any of the Chinese built aftermarket stuff (quality wise) and the Alpine's and Kenwood's (for my tastes) don't integrate very nicely (or even fit). But I'm new to the whole BMW E38 world and not yet understanding how/where the signal travels from the OEM head unit to the DSP amp and if I can relatively easily (without huge expense) pull that signal out. Some past vehicles I've done, there was a low level signal coming from the factory head unit to the factory amp that you could just cut into those wires and solder on a few RCA ends ......... and Bob was your uncle !!

Gear wise, I already have an Alpine processor and a few others kicking around to choose from. For the 3-ways I've already test fit and should be good to go with a tweet/4"/6.5" in the doors. The 6.5" will be housed in a custom pieces that will take the place of the lower third of the door skin that can be removed (pocket portion). I have a second set of door skins to be able to build these pieces off of so the original door skins remain spotless and undamaged. I've built a few custom systems over the years and I'm fairly familiar with builds. Right now I'm taking advantage of the interior of my e38 being totally gutted to get all my wiring in that I will need or may need in the future!!

But before I get started, I want to have workable plan on the table to follow and not be doing this by trial and error with regards to keeping the factory OEM head unit. If it becomes too much of an issue, I will just source out an aftermarket piece and be done with it. But once again, preference is to try and stay with the OEM look.

[DennisCooper]

Hi,

You'll need to start building up your Googley and Yahooy Fu and search out threads from 5/10/15+ years ago and work out how and where to get at the signal prior to amplification. The Intravee and Alpine PXA-H100 or H800 processor route I believe is the 'easy' way to do this, but do that research. You won't be able to 'tap' into a signal wire, it is I believe at iBus level and then decoded as it were at the amplifier. The simplest way is to use the signal summing / audio processor route as I mention above. The JBL MS-8 is now discontinued, but that took each of the speaker level outputs of the OEM amp, did the clever processing and then it also had an 8X30 W RMS amplifier built in so that the OEM DSP speakers could be individually driven. I heard an M5 done that way, I personally wasn't impressed compared to the SQ from a good aftermarket head unit, but that particular owner was happy as he didn't want 'excellent' audio, just a bit louder and a bit more oomph from the standard speakers. Take a look at the Mosconi ONE 60.8 DSP, the Helix V Eight and/or Helix P Six.

For aftermarket head units then all the chinese units have low SQ and low quality everything else in comparison - so count that idea out.

There are Shallow depth premium brand head units but as you say, they don't have OEM looks, which is why I designed and manufacture the OEM look fascia/fitting kit for the E39. I do have plans for an E38 version, but will do the E46 before that.

I'd say keep the tweeters in the original door/window corner locations, assuming that's the same as the E39 - I'm not so directly familiar with the E38. Some years back now, an E39 owner I knew went for a mid level SQ build and wanted to get involved with competing. He'd had custom door builds made and he did very well in the class he was in. Soon, he sold the car and I purchased the door cards. They were fibreglassed and the air vent was blocked for the mid range driver from an Audison 3 way component set, looks like this




It sounds as though you have some plans for the door builds though

Cheers, Dennis!

[tominizer]

@ Dennis ........ I played with the MS8 many years ago in my Mini Clubman S. Horrible experience for the amount of work I did. Eventually gutted out the dash, ran ribbon cable to relocate the OEM head unit deep in the bowels of that dash (AFTER removing the head unit from the big round speedo that it attaches to.....brutal stupid design) and went to an aftermarket head unit. Sounds like based on what you are saying, if I keep the stock head unit, I may just be walking down that "MS-8" experience of much unhappiness again. That leads me to thinking I should just by-pass all that grief and just go right to the aftermarket and build something up front that will match as best as possible. Not a problem with that. I can make that work. Right now I haven't been able to find anyone having much success with making that stock head unit work like I want it to anyways. I'm not looking for a NAV setup either as I use WAZE on my phone.

Like that mid and tweeter up high in that door and that they are so close to each other. That must have brought the stage up nice and high. The E38 has the tweeter in that location and the mid down mid-front door, so it's sort of very similar from the factory.

Do you have any pictures of this "kit" you make for the E39. Just curious to see what you are talking about.