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Discussion Starter · #1 ·
I'm thinking of adding an amp and subwoofer to my professional audio system. I've started looking at the components in the car and have concluded it will be reasonably challenging. For a start the input to the stock amplifier is fibre optic, so options are limited, but I'm confident my electronics background will help me achieve the what is needed.

The best place to mount the amp would seem to be between the parcel shelf and the chassis, making the amp 'invisible', but to do the job properly will involve removing the back seat, parcel shelf and all covers / cowlings from the trunk / boot. If enough people are interested I'll write a guide showing how to do it. Like I say the job is likely to need a level of practical skill, but the hardest part will be working out what wires to tap and the best way to interface with the amplifier. I'll work that out and publish the method if there are enough takers. Anyone?
 

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Sounds great.
 

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Diver624
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I'm thinking of adding an amp and subwoofer to my professional audio system. I've started looking at the components in the car and have concluded it will be reasonably challenging. For a start the input to the stock amplifier is fibre optic, so options are limited, but I'm confident my electronics background will help me achieve the what is needed.

The best place to mount the amp would seem to be between the parcel shelf and the chassis, making the amp 'invisible', but to do the job properly will involve removing the back seat, parcel shelf and all covers / cowlings from the trunk / boot. If enough people are interested I'll write a guide showing how to do it. Like I say the job is likely to need a level of practical skill, but the hardest part will be working out what wires to tap and the best way to interface with the amplifier. I'll work that out and publish the method if there are enough takers. Anyone?
Would it be easier to just replace the existing subs under the seats with JL's or something like that and maybe interface a new sub amp into the system if necessary.
The BMW profesional system is the best oem system I've heard short of the upgraded Panamera system but the subs are the weakest part of it so maybe just try swapping them out first.
Personally with so much outside noise in a car the professional system is plenty good enough for me.
 

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Discussion Starter · #4 ·
Would it be easier to just replace the existing subs under the seats with JL's or something like that and maybe interface a new sub amp into the system if necessary.
The BMW profesional system is the best oem system I've heard short of the upgraded Panamera system but the subs are the weakest part of it so maybe just try swapping them out first.
Personally with so much outside noise in a car the professional system is plenty good enough for me.
The short answer is no. The trouble with the stock subs is that the enclosure simply isn't large enough. It sits in the floorpans under the front seats. To get a decent low end under 150Hz you need larger speakers with an enclosure to match. To drive larger speakers you need a larger amp. The rated 600w of the system is over exaggerated. It's certainly not 600w RMS. Chances are it's 600W PMPO, which equates to around 150W RMS in total for all speakers. A decent sub woofer needs around 100W RMS. This is nothing to do with how loud it gets. It is to do with the power required to drive a larger cone against a powerful magnet (needed to properly control the cone). I agree that for an OEM stereo to professional / premium system is good. It is however no where near as good as a properly designed and installed aftermarket system. If you think otherwise, you've not heard a decent system. That said, it does depend on what you're looking for. Personally I like to feel the bass. One major issue with the stock system is that when you have it up loud, the sound is noticeably limited. This isn't necessarily a bad thing as it prevents distortion, but it does limit what the system can do.
 

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Diver624
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The short answer is no. The trouble with the stock subs is that the enclosure simply isn't large enough. It sits in the floorpans under the front seats. To get a decent low end under 150Hz you need larger speakers with an enclosure to match. To drive larger speakers you need a larger amp. The rated 600w of the system is over exaggerated. It's certainly not 600w RMS. Chances are it's 600W PMPO, which equates to around 150W RMS in total for all speakers. A decent sub woofer needs around 100W RMS. This is nothing to do with how loud it gets. It is to do with the power required to drive a larger cone against a powerful magnet (needed to properly control the cone). I agree that for an OEM stereo to professional / premium system is good. It is however no where near as good as a properly designed and installed aftermarket system. If you think otherwise, you've not heard a decent system. That said, it does depend on what you're looking for. Personally I like to feel the bass. One major issue with the stock system is that when you have it up loud, the sound is noticeably limited. This isn't necessarily a bad thing as it prevents distortion, but it does limit what the system can do.
I agree it's not an audiophile system but it's certainly a very good oem one, you probably should not have spent the $ on the professional system and just built a system from scratch but i guess it came in a package.
 

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I had a Jl audio box installed in my 2008 750 li which had that fiber optic problem. I had installed the high performance jl audio box, jl audio 500/1 amp and a bass control knob. Utilized stock system for highs and mids. Car thumped in a huge way and sounded great. I'm about to do it to my 550.
 

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Discussion Starter · #8 ·
I agree it's not an audiophile system but it's certainly a very good oem one, you probably should not have spent the $ on the professional system and just built a system from scratch but i guess it came in a package.
I went for the pro system because I'd rather not have to upgrade everything. All I want to do at the moment is add a sub. Had I gone for the standard issue, I'd probably want to upgrade all the speakers plus the amps too. The pro system was well worth the extra for me.
 

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I am also currently researching this project, and have also come across the dilemma of finding a suitable place to "tap" the input signal for an external amp. As another forum member has previously pointed out, the output of the amplifier (to the subs) is approximately 50 volts peak to peak, which is effectively too high for a normal amplifier input, even with a line voltage regulator. One solution for that could be the use of a voltage divider; I also wanted to look into tapping into the input (fiber) to the amp, with maybe a device having a fiber optic input, and combination fiber optic and RCA/line voltage output. I am extremely interested in both finding a plausible solution, as well as helping anyone to come to a common solution; I already have the subs and amp selected for my system (JL audio) and am checking the forum everyday to see if anyone has made any progress; if anyone would like to email me with suggestions or more info on what I've found so far, my email address is [email protected]. By the way, I spoke to several car audio shops here in town (Las Vegas) and they all pretty much said the same thing; if they attempt to connect an external amp to this system, it would VOID THE WARRANTY...something to keep in mind!
 

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Discussion Starter · #12 ·
Time permitting, I'm hoping to continue with my project this weekend, so watch this space for part 2.
 

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Okay, I may be way off-base with this suggestion, but what about this; if I remember correctly, you said the F10 amplifier had a fiber-optic digital input. How about if you use a digital audio splitter on the INPUT side of the amp, with two outputs; one for the OEM amp, and one to be used with the new Sub amp. Then, with the digital input for the Sub amp, use a digital-to-analog decoder, which will take a fiber input and yield an RCA left/right output...does this sound like a feasible solution? Here are links to some possible components for this setup:

Digital-Analog Converter:
http://www.ramelectronics.net/audio...converter-gtv-digaud-2-aaud/prodGEF00232.html

Digital-Analog Decoder:
http://www.ramelectronics.net/audio...-analog-decoder-gtv-dd-2-aa/prodGTVDD2AA.html

Fiber Optic Splitter:
http://www.ramelectronics.net/audio...ters/toslink-splitter-pof-810/prodPOF810.html

I realized at the last minute that one of these was basically designed for home systems, thus it has an AC power supply with a 5 VDC output, but I'm sure we could find a simple transformer/voltage divider to step-down the voltage from 12 VDC. Just trying to add my input to help us all come to a working solution!
:angel:
 

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Discussion Starter · #14 · (Edited)
Good suggestion, however there are several technical considerations...

1, the connector is proprietry and does not resemble a TOSLINK connector used with the kind of devices your talking about.
2, The fibre will carry multiple channel audio since there would be no way to fade otherwise. It is unlikely that the signal is an industry recognised format such as AC3 or ADAT since these would require royalty payments to the patent holders. Since this is a closed system, there would be no point in paying the royalties so the signal is likely to be proprietary.

Like I say - nice idea, but defenately not worth the hassle pursuing. If I really felt it worthwhile sourcing a line level signal, I would be looking to tap from inside the amplifier after the DA convertors. This probably would also require some form of electronics. Since my aim is simply to add a sub amp there would be no benefit in doing this over utilising the speaker outs on the amp.
 

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You need to read the entire thread to get caught up on our issues; the signal coming off the amp at the speakers is up to 50 Volts peak to peak; that would blow just about any amp I have ever seen, without some sort of voltage divider or line input adapter; not to mention, all the speaker signals "appear" to have high/low pass filters internally in the amp. I think that is still being determined, but I think that the sub input signal FROM the amp had a bandpass filter, with the low-end rollloff around 170 hz...I would love to see a usable signal with freqs down to at least 30hz, 20 ideally.
 

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Discussion Starter · #20 ·
Happy to report have now finished the install of an additional amp into my F10. Used a FLI line driver which at 38 volts peak to peak was outputting 2.7 volts. This is a transformer based device which is better (and safer) than a resistor based voltage divider.

Using a JL XD series amp. Don't have a decent enough enclosure yet though. Tested the setup with a 10" pioneer sub in a box I had lying around. Doesn't have enough oomf to travel through the F10. Will be trying some different speakers over the coming weeks. At 3 volts into the amp I was getting a perfect sine wave at 101 volts peak to peak on my scope so not troubles there. The only challenge might be getting the new Sub(s) to go low enough since the sub out on the F10's amp rolls off. Will need some electronics if it becomes a problem, but I'll be demoing a few speakers first to see how I get on.

Will try and write part 2 of my install guide this weekend
 
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