club.liberty.asn.au

Thought id post my planned setup once my lib comes back:

Edit - seeing as things have changed a fair bit for my car and build, the following has been amended as follows:

- Double Din fascia panel from Phat
- JVC Headunit (a few years old but never used - bought for a previous car I owned). Four RCA pre-outs plus 2 sub preouts. USB input \ aux input jack and mp3 capable

Now going with 07 gtb mcintosh headunit

AudioControl lc6i 6 chan line convertor with sub output

Feeding into the following:
- Twin Cerwin Vega 12" dual voice coil subs, in custom bandpass box - driven by 800wrms @ 1ohm mono block JVC amp
- Response 6.5" splits up front with 18db\octave crossovers (24 once stepped with inbuilt amp xover)
- Alpine 6" Coaxials in rear
- Motorola dual stage Piezo compression drivers (rated to handle 500wrms each @ 4ohm)
- Above drivers will be run off Response 4x100wrms @4ohm amp
- 2 gauge cabling down to passnger side floorpan (fused at battery) into splitter then 2x4gauge to amps
- Gold Plated RCA cabling

System will be tuned as follows:
subs <100hz
Splits > 100hz
coaxials > 250hz
Horns > 1000hz

Subs made 144db in my old celica running only 300wrms each (using the above response 4ch in bridged mode @ 2 ohm). Will be interesting to see what these will achieve with the additional power. Excursion on these things is superb and bass is nice and tight yet lower frequencies literally shake the car with the right tunes.

Im too old for SPL and doof doof now so i doubt I will ever really take the system to its limitations - will only be installing as I have them around so why not.

Mick

Sounds good, however I'd run 1/0 gauge and then split to 4 gauge instead of 2 gauge split to 4 gauge.

This will allow better current flow and also more room for expansion in the future (if you choose to).

Nice gear, I didn't think anyone knew who cerwin vega were anymore.

Try crossing the subs over at 80hz, the splits/coaxials at 80. You will find those crossover points will more naturally align with the speakers natural curve and give a far easier tune, also remember you will get a +3db (2x more volume aprox) spike at the 80hz crossover point as subs and normal speakers will be producing that particular frequency so you may need to roll that off a bit on your eq. Remember frequency is a logarithmic scale like decibels. ergo the note of Middle A (440hz) is exactly double the frequency of Low A (220Hz) as we as exactly half of High A (880Hz). I suspect your system is missing some serious Mid-Bass (100Hz -300Hz) which is roughly the higher notes of a bass guitar and the lower notes of an electric guitar.

By crossing off your subs at such a high freq, your sub will be producing some un-naturally high notes and sounding a little 'woofy', and the same with your splits/coaxes, they are probably sounding just a little tinny? 250hz is phenominally high to cross over when most coaxes and splits will happilly produce a flat response down to 80Hz providing they are powered properly. Musically speaking you've chopped off 1/3rd of an electric guitars notes! And scene as your running exactly the same amps I am, I doubt power is an issue .

If your experienceing distortion at those freqs then I would be looking at your gain structure, most noteably the gain sensitivity settings on your amp, your really need to get an oscilliscope to set this properly. But the basic rule of 3/4 Volume at the head unit with a flat EQ and the wind up the gain till distortion is heard, then back it off slightly will give you a fairly close match. Then you can eq, if you experience distortion from there, you have it too loud or expect too much from your system. If you want to know what your speakers produce and want to know good natural crossover points, look at the freq response chart that comes with the speakers. If you need help interpreting them I'd be more than happy to help. Essentially your looking for the Knee (where the frequency begins falling away from teh 0db line) and the slope (how many db per octave that fall creates). Food for thought anyway. Experimentation is always the best way to know for sure, I've gone as high as 160hz for some weak coaxials before but I rarely like putting a sub over 100hz as as any sub over 10" doesn't like moving fast enough to produce those freqs and usually burns the motor out pretty quick.

Peace

Thanks for the detailed post and advice.

In terms of cabling, to be honest I have the two gauge lying around so thought id put it to use.

The cerwin Vegas are one of the best subs I've heard (although I havent been into audio for a few years so I'm sure latest developments have changed). 500wrms into dual voice coils is pretty good for subs I purchased in 1999!

Thanks for your advice re tuning. I built the bandpass box myself using bassbox pro, tuned to 80hz. I think I may have mixed up my crossover settings above as I'm pretty sure I used to set low to 100 and mid to 100 plus. Will take your advice though.

What do you think of the compression drivers?

I think Motorolla Compression drivers are a VERY interesting concept for car audio, they are by far one of the most efficient tweeters out there, not only can they take a lot of power but they can effectivly convert it into sound with a very wide spread so you will find alignment less of an issue with them. I havn't used them in cars before but I have used them in P.A. and bass guitar applications with great success.

As for the band pass box, it will naturally boost certain freqs, but it will not change the electro-mechanical characteristics of the sub itself, so still try 80hz and see if it improves, if it doesn't then turn it back Experiment a little

Thanks mate

Yeah I used to have the compression horns mounted underneath the dash trays (near pedal box on drivers side and under glovebox on passenger side) in my celica, facing into the cabin. These gave exceptional presence and front staging without a hint of distortion. I was running a dedicated 2 ch amp for these at 150wrms each (thd of .005%).

You're right about the subs. I just checked my old notebook and the subs were crossed at 90hz and mids were crossed at 85 (focals).

Haven't installed the setup yet so will see how it pans out.

Thanks again for the advice gents

Mick

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