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5CH Amplifier Setup For R230 SL

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by joe2612, Oct 16, 2020.

  1. joe2612

    joe2612 New Member

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    Your Mercedes:
    SL55 AMG 2003
    Hi all,

    I'm in the process of replacing my bose amp with a JL audio XD700 and retaining the bose speakers.

    Does anyone who has installed this amp ( or any 5ch amp for that matter) have any tips or advice on the best setup/ settings for the amplifier with the stock speakers? I know that the gain must be turned down for the 2ohm impedance of the Bose speakers.

    My plan is to:

    - Door mid-high and mid-low to CH1 and CH2,
    - Centre speaker to the aftermarket head unit and the rears, I'm not sure yet.
    - Rear mids, again they are tiny so not sure if wiring to CH3 + CH4 would be overkill.
    - Sub to Sub

    Obviously audio is subjective, but I'm sure many others have this amp/speaker setup so it would be helpful to have a baseline to start with.
     
  2. Alfie

    Alfie Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
    A150 manual, smart forTwo, W205 AMG line premium plus.
    Dont forget the sub. That needs to be fed too!

    I assume you are changing the head unit too?
     
  3. OP
    joe2612

    joe2612 New Member

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    @Alfie Yep, considered the sub aswell and command 2.0 is going, I'm yet to decide on its replacement but whilst I decide I'm planning the speaker to JL amp integration.
     
  4. OP
    joe2612

    joe2612 New Member

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    Your Mercedes:
    SL55 AMG 2003
    If anyone else is interested, here is how I set the system up. I am by no means a car audio installer ( this is the first install I've done in over 10 years), but it sounds very nice.


    FRONTS
    Left+Right RCA Out from Headunit into 2* Y splitter to feed CH1,2,3,4 IN on JL Amp.

    Used Channel 1 + 2 on the JL amp to drive the mid-high range door speakers.
    > High Pass Filter at 5000HZ
    > Gains set at roughly 11 O clock

    Used Channel 3 + 4 on the JL amp to drive the mid-low range door speakers (woofers).
    > Band Pass Filter set at 80HZ - 5000HZ
    > Gains set at roughly 12 O clock


    REAR
    Rewired the rear mono speakers to stereo and ran them directly from the Headunit
    > Highpass filter at 250HZ ( IIRC)
    > Shifted the balance of the system forward so as to act as rear fill.


    CENTRE
    Bridged Right front and Left left from the head unit to create a centre stage speaker.
    > Experienced much speaker farting in testing, and creating a HPF on the headunit would affect the main channels to the amp. So I wired in a 330uf Capacitor to filter out bass frequencies below 250HZ ( Will probably change to a 44uF to shift the filter up to 1800HZ).


    SUB
    Sub RCA Out into Y Splitter into SUB Input on JL Amo
    > Low Pass Filter set at 80HZ
    > Gains set at roughly 1 O clock

    Headunit
    I wanted something that had a large screen and looked as OEM as possible. I wasn't keen on the android unit that looks like the stock command unit, so I eventually opted for a differed android unit from China designed for a facelift R230. I have spent quite a bit of time testing various models on my desk for durability and reliability. (my background is s/w / hw engineering) and was happy to take the plunge for this model:

    https://www.aliexpress.com/item/1005001499809095.html?spm=a2g0s.9042311.0.0.7f7f4c4dE4zIGy

    It's the largest screen size you can fit in an R230 facia and I have to say the fit and finish is very good.

    I had to cut the 2003 trim panel to make it fit, and source some 2mm aluminium bar to carefully cut and bend to the correct curvature to create the trim piece.

    It supports carplay and has a UI that looks very similar to that of the 2014 ish Mercedes UI. The radio works perfectly provided to hook the radio amp output into the R230 input. I also have all the steering wheel controls ( although I need to perhaps change the canbus box to one that doesn't skip the track unless I am on the audio menu in the instrument cluster).

    Crucially, it has a DSP which I needed for the next stage:


    System Setup

    I used(using) a Dayton UMM-6 calibration Mic positioned on the driver's headrest and REW software to analyse the frequency response of the system, by playing mono pink noise from each speaker and then in stereo to increase or attenuate any frequencies ( using the head unit equaliser) that were either too high or too low according to the target curve I was aiming for. (I used Audiofrogs target curve then tweaked according to my preferences).

    Overall the response rate was pretty good, I have a dip around 200 - 500hz which I couldn't seem to correct but the frequencies from 500 up were pretty flat before falling off from around 10K.

    I set the delays according to speaker distance to create a 'centre stage' on the dash with a touch of rear fill.

    Next Steps

    Continue tweaking the system to get a flatter curve and boost the 200-500 range. More bass at 30h-50hz would be nice, but I have distronic so not sure what I could fit in the subwoofer space to help with that.

    The gains were finicky to set. I used JL's method of playing 1KHZ Sine wave at 3/4 volume and hooking up an AC multimeter to the speaker terminals to get the voltage to max 14.4v for the main channel and 24.5v for the sub. This resulted in quite a bit of speaker hiss so presume there is a mis-match of the source units output volume. Turning the gains down too far led to less speaker hiss but more audio distortion, so I've found a balance that works for now, but if anyone has any advice on this topic that would be helpful.
     

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