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    SQ: Factory vs. Aftermarket

    This may be obvious, but for those who know, which setup is going to produce the best sound?

    1: Alpine CM5908 with factory amp

    2: Aftermarket Alpine CDE-HD149BT with amp bypass

    How does the factory HU compare to a new HU if the factory amp is replaced with aftermarket?
    Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

    #2
    How about trying it and telling us?

    In fairness to the factory setup, both the head unit and power amp should be electrically restored first. Even then the factory amp used speaker level inputs which will never beat properly shielded line level inputs. In order of quality I suspect the following is true

    1) aftermarket HU, line level to a low THD aftermarket amp
    2) factory HU modded with line level out, low THD aftermarket amp
    3) electrically restored factory premium setup
    4) aftermarket speaker level output to aftermarket amp
    I BUY/SELL REFURBISHED CM5907s & CM5908s

    HOWTOs:
    DB vert plastic bumpers
    OEM Keys
    MTech1 docs

    88 ix Lach/Card
    91 ic Calypso 3.1
    86 Cosmo 2.7

    OEM+ or bust!


    reelizmpro: I will always be an e30 guy.. I still do all of my own labor
    TrentW: There's just something so right about a well-built M20 in an E30
    e30m3s54turbo: I save my money for tuner parts.

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      #3
      I have the original stereo and amp the previous owner cut out. I don’t know what condition they are in as far as if they function properly. I’m going to keep them, but I don’t want them in the car if the aftermarket HU provides better SQ. I’d have to wire them in to test them and I’m not going to do that if I install the aftermarket HU. There is also no point in restoring the old units (if they need that) if they are just going to be sitting in a box. When and if the time came I wanted to use them (or a future owner) then they could be restored if necessary.
      Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

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        #4
        If powering the speakers from a head unit, ANY head unit, the sound quality will be the same (not great). No single-DIN head unit, factory or aftermarket, has a step-up DC-DC converter, so all of them power the internal amp chips from Vbattery. What this means is that, for a 4 Ohm nominal speaker, you are not going to be able to deliver more than ~15W-RMS to the speaker before massive distortion (>10%) sets in.

        So, if an aftermarket HU has some functional features that you like, then there's a good reason to get one. From a sound quality standpoint, do not expect much and certainly don't spend more on any HU that promises to deliver it, because it is physically impossible. The internal amp ICs that HUs use have improved a little in the last 30 years, but not enough to really matter. The "50Wx4" marketing nonsense refers explicitly to the DC power that can be delivered to a 4 Ohm resistor with Vbattery-14.14V, and has nothing to do with audio.

        The only way to get high quality, LOUD sound reproduction in the car is to use an aftermarket amplifier. I have no idea what the specs on the factory amp are, but just based on its size and age (pre-dating high efficiency class-D designs), I would guess that it is not capable of providing much more power delivery than the head unit. Almost any aftermarket amp that is spec'ed at 50W-RMS x 4 should be fine, and is almost guaranteed to deliver vastly better audio performance than driving speakers from the HU. Achieving this also requires some wiring work to make sure that there are no ground loops or alternator noise, but that is usually pretty straightforward.

        Regarding pre-amp signals vs speaker-level signals, you can get good results from both if you are intelligent with how you wire things.
        Last edited by bmwman91; 02-06-2019, 10:42 AM.

        Comment


          #5
          ^^ good advice, info here. Spot on
          I BUY/SELL REFURBISHED CM5907s & CM5908s

          HOWTOs:
          DB vert plastic bumpers
          OEM Keys
          MTech1 docs

          88 ix Lach/Card
          91 ic Calypso 3.1
          86 Cosmo 2.7

          OEM+ or bust!


          reelizmpro: I will always be an e30 guy.. I still do all of my own labor
          TrentW: There's just something so right about a well-built M20 in an E30
          e30m3s54turbo: I save my money for tuner parts.

          Comment


            #6
            Here is another option to consider:
            Run a Dayton DSP-408 with the Bluetooth dongle in the trunk. My experience with this has been the BT streaming directly into the DSP yields equal or better quality than what you get out of most head units. I suspect that it’s a combination of eliminating AD/DA conversions, and how mediocre most head units really are. (The head unit in my E90 is an absolute calamity.)

            Then you can either run a blank plate, install gauges, or leave the factory unit intact. In fact, the Dayton will accept analogue inputs from your factory head unit, so it will even be functional!

            Edit: This does, of course, require installing an amp in the trunk.
            2006 GMC Sierra 2500HD 4WD LBZ/Allison
            2002 BMW M3 Alpinweiß/Black
            1999 323i GTS2 Alpinweiß
            1995 M3 Dakargelb/Black
            - S50B32/S6S420G/3.91
            1990 325is Brilliantrot/Tan
            1989 M3 Alpinweiß/Black

            Hers: 1996 Porsche 911 Turbo Black/Black
            Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

            sigpic

            Comment


              #7
              Hey thanks for the recommendations! That DSP looks enticing. One thing that I don't like about the aftermarket Alpine units is that they're kind of bright which is a little annoying at night. So that's a plus for the factory HU, but I'd like HD radio, BT, and a CD player and I don't want to install a bunch of separate things. Maybe the aftermarket HU will be best then.
              Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

              Comment


                #8
                Originally posted by Andrew325is View Post
                Hey thanks for the recommendations! That DSP looks enticing. One thing that I don't like about the aftermarket Alpine units is that they're kind of bright which is a little annoying at night. So that's a plus for the factory HU, but I'd like HD radio, BT, and a CD player and I don't want to install a bunch of separate things. Maybe the aftermarket HU will be best then.
                I currently have four of the Daytons. They are really, really good for the money. The iphone app is great, they hold their memory through battery disconnection, and the sound is good.

                Pretty much unbeatable value. Literally my only complaint is that in a perfect world, they'd have 10 outputs.
                2006 GMC Sierra 2500HD 4WD LBZ/Allison
                2002 BMW M3 Alpinweiß/Black
                1999 323i GTS2 Alpinweiß
                1995 M3 Dakargelb/Black
                - S50B32/S6S420G/3.91
                1990 325is Brilliantrot/Tan
                1989 M3 Alpinweiß/Black

                Hers: 1996 Porsche 911 Turbo Black/Black
                Hers: 1988 325iX Coupe Diamantschwartz/Black 5spd

                sigpic

                Comment


                  #9
                  Awesome.

                  I didn't realize there's an adapter harness from BMW for the original stereo to connect a newer BMW HU like the CD43. So I'll restore the original wiring and use that. Then I can make another adapter to connect that to the aftermarket radio. That way I can switch between them as I feel like it. :)
                  Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

                  Comment


                    #10
                    I wired in the original CM5908 radio and amp and it looks like the radio does need to be repaired. It hisses and crackles. The display is good though and all the buttons seem to work.
                    Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

                    Comment


                      #11
                      Could someone help me figure out the amp bypass wiring while leaving the original wiring intact? I know, needlessly complicated.

                      Someone gave me a stock amp that apparently is no good, so I thought I could use it to do the amp bypass mod while leaving the wiring to the amp intact. One thing that is confusing me are the common ground speaker wires coming from the radio. I read there shouldn't be common grounds for the speakers for the aftermarket HU. So do I just connect the positive wires together inside the amp and leave the grounds connected as they are in the amp? Does the amp need to be powered on for the grounds to do whatever they need to do or should I terminate the power and remote turn on wires?
                      Last edited by Andrew325is; 02-21-2019, 12:57 PM.
                      Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

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                        #12
                        Maybe I can install a floating ground adapter inside the amp. Except, it would be wired backwards, hmm.
                        Last edited by Andrew325is; 02-21-2019, 01:31 PM.
                        Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

                        Comment


                          #13
                          Okay, so the grounds are combined at the radio too. So the original wiring goes from common ground, then separated, to common ground at the amp, and then separated again to the speakers. Will it work if I install the floating ground adapter at the radio and then combine the grounds going to the speakers?
                          Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

                          Comment


                            #14
                            Well forget that, haha. I’m just going to run RCAs to a new amp. :)
                            Plug and Play Wiring Harness Adapters for S54, S50, M54 and more.

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