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Thread: 97 540i w/ dsp sound subwoofer questions

  1. #1
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    97 540i w/ dsp sound subwoofer questions

    I've got the factory Dsp sound system...including factory subs. The subs sound a little weak though,not a whole lot of bass.
    I've got a Jl audio 8" Microsub in a one foot sealed box that I think would augment the Dsp system rather nicely.
    I've got a line out connector, rca's and a 500 watt amp that is bolted to the top of my Microsub box.

    I'm assuming that I'll need to tap into the factory sub input wires coming from the amp to use the LOC,plus the white(?) power remote wire.
    Will I need to completely disconnect the factory subs? or, can i simply turn down the base from the radio controls and then turn up the bass on the microsub? I feel that this would basically result in a slightly higher low end frequency from the factory components and a much lower, more powerful bass from the separately tuned Microsub.

  2. #2
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    What is the brand and the model of the sub amp? Some sub amps have speaker level inputs. If yours doesn’t have those inputs you’ll connect the amp via the LOCs to the wires going to the factory subs. The sub amp’s positive cable should be wired directly to the battery via a fused cable. Having a fuse in the cable protects the cable in case the insulation is damaged. The fuse should be as recommended by the amp manufacturer. The ground cable should be wired to the factory audio ground, if it exists. If not, keep the ground cable as short as possible. It needs to be the same gauge of wire as the positive cable. Do not connect the ground cable to the battery as that’ll induce a huge amount of noise.

  3. #3
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    Quote Originally Posted by MarcoZandrini View Post
    What is the brand and the model of the sub amp? Some sub amps have speaker level inputs. If yours doesn’t have those inputs you’ll connect the amp via the LOCs to the wires going to the factory subs. The sub amp’s positive cable should be wired directly to the battery via a fused cable. Having a fuse in the cable protects the cable in case the insulation is damaged. The fuse should be as recommended by the amp manufacturer. The ground cable should be wired to the factory audio ground, if it exists. If not, keep the ground cable as short as possible. It needs to be the same gauge of wire as the positive cable. Do not connect the ground cable to the battery as that’ll induce a huge amount of noise.
    It's a pro sound labs (250 watt x2) bridged into one channel...that I've used for about 10+ years through multiple cars.
    I've also got a 500 watt install kit that I've used with it through multiple past BMW's.
    It does have the inline fuse that you're talking about...I actually paid more ($50) for the install kit than I originally paid ($20) for the amp...cause I'm a baller on a budget.?
    It looks like I've identified the wires ( output to factory subs) that I'll need to tap into...my amp only has rca input.
    But what about the power remote wire...which one is it?

  4. #4
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    Great question! PM DennisCooper as he’s the 5 series guru.

  5. #5
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    Hi,

    Thanks for the kind words Marco !!

    Jwwetzel - The issue I see is that the OEM setup is 'weak'. The low end from the DSP setup isn't what I'd call 'sub bass' at all! Another issue is that the oem amp isn't very powerful and also runs higher distortion levels. If you take that 'low' output from the oem amp, then it's quite easy to push it into distortion and then that in turn is passed to your amplifier which then amplifies that distortion even more and passes it to your subwoofer. In turn, this simply heats up the voice coil and the number one reason for speaker failure is overheated voice coils. To reduce the chances of that, owners thinking or who've gone the route you mention here turn the bass and gains down on their amplifiers, which then reduces performance and kinda defeats the object.

    I run that same JL Audio 8W3-V3 subwoofer in my E39 Touring and it absolutely pumps out some fantastic clean, tight, controlled, musical and punchy/low sub bass that simply astonishes many enthusiasts who hear it! to the point that 'most' are absolutely convinced they're hearing a 'meaty 10 inch' sub, a good proportion more convinced it's got to be a 12 and a small but surprising number who think they're hearing a 15 inch ! when I show them the 8 inch the look of surprise/astonishment/shock/dropped jaws is hilarious! - I run it from an excellent quality head unit and then onto a Class D Arc Audio amplifier at 300W RMS, so a nice clean, musical input that's very much distortion free, or at least a lot less than compared to the the amount of distortion the oem setup sends out.

    Turning down the bass on your oem setup then turning up the bass on your amp won't really be the way to go - it'll work and you might well find it's enough for you but in terms of best practice for audio, it's a long way off. Another factor is that with that decent amount of power for the subwoofer will possibly overwhelm the cabin speakers so another 'mismatch' there. Again, to compensate, you'll turn down the subwoofer amp/levels and again negating the whole point of the project.

    There's many E39 audio threads around, you might find that what you want to do is ok for you in which case press on ahead and don't listen to anything I or anyone else mentions! if you then find this route isn't for you / misses the mark of audio performance you'd like, then keep in mind that when done properly, that JL 8 inch sub (assuming it's the 8W3-V3) can provide awesome sub bass, then with the right setup you'll have fantastic, balanced and musically excellent performance in your E39

    Cheers, Dennis!

  6. #6
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    he, see, I told you he’s the E39 audio guru!!!

    Dennis, check out my updated garage!

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