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PhilS

What are the principles for setting up a car audio system?

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I recently found this thread, and it got me back to thinking about properly setting up (or trying to) my system in the Exige. When I installed the system I had a go at doing this, but got a bit lost, so reverted to factory settings and just tweaked the tone controls a bit. However, reading this, I'm keen to have another go, and wondered if any members have expertise that could help.

First off, I have the following installed in my car:

Head Unit: Alpine IDE-178BT

Front Speakers: Infinity Kappa 42.9i (frequency response 75 -25khz, sensitivity 93db)

Rear Speakers: Infinity Kappa 52.11i (frequency response 55 -25khz, sensitivity 94db)

Subwoofer: Pioneer TS-WX 120A located in the passenger footwell. (frequency response 30-160hz)

The head unit setup options are very similar to the unit in the Evora guide, above, and this is what I'd like help with. Of course, some of the settings are absolute and easy to setup, but the ones I'm not sure about are the Cross-over and EQ settings:

Firstly, the Cross-overs. I can set the cross-over frequency (defined steps that include 40, 50, 63, 80, 100, 125Hz), slope (flat, 6, 12, 18, 24db/Octave) and level (0, -1, -2db etc) for front, rear and Sub-Woofer. The Evora guide uses the same frequency for HPF and LPF, which makes sense, but that is just for fronts, for our cars with front and rear, would a good principle be to set front and rear to the same point (the higher of the two lower frequency response limits, so 80hz in my case), or individually to suit each speaker pair (63 and 80hz respectively)? If the latter, then should the sub match the lower of the two? How about the slope, what factors do you consider when setting either a soft or abrupt cutover?

Secondly, for the EQ, on the Evora setup, I was surprised by how much variation there is across the frequency spectrum. How the hell does one go about getting to that point?!

Sorry for the long post - any help / advice / pre-defined configurations (!) gratefully received.

Thanks in advance,

Phil.

 

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Hi Phil

I'll give this a go. Let me say you are asking fairly reasonable, technical questions but are skirting the edge of overthinking it :)

The response curves of the speakers are theoretical and will vary substantially once housed in the car. The graphs/numbers are probably based on an idealized scenario. IRL they will tend to have odd resonant behaviour that means you will end up tuning by ear to some extent. I got myself a plug in reference mic for the iPad which is helpful in smoothing out the crossover from sub to fronts, particularly, adapting the sub parameters to the front speakers and avoiding big resonances in the foot well. I use SpectrumView, but any spectrum analyser app will generally do, and you can probably use the built in mic at least for finding odd booms and spikes.

Your approach is sound, cut over at 80Hz, i.e. as low as you can match, and I'd pick a reasonably soft roll off, so that you don't get obvious transitions on sweeps. So if you intend to use the crossover features of the H/U, I'd use 6dB/octave.

HTH

Martyn

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