OEM crossover frequency

[Morrison]

Does anyone know what the factory crossover frequency is to the tweeters? I believe its 6 db/octave, but not sure where it starts to drop off. I'm looking to put in different tweets but keep my oem mids and crossovers for now. Also, I want to keep with an 8 ohm version since that is what the Nokia tweets are. Right now I am thinking LPG 26NA.

[StereoInstaller1]

IIRC it is a 3.3uF cap, so that's what, 6Kish?

I have hacked the coil on my wifes car to use as the inductor in a 12db/oct for her tweets, leaving the mod running full (high passed actively, of course, like 120Hz) using the stock tweet...it sounds pretty damn good overall!

[Morrison]

If it's 6kish then I may also consider this smaller aurasound tweeter that I saw on madisound. That's interesting info about being able to let the mid roll off naturally on the top end. Do you recall what frequency you set up the 12 db version at?

[Jean]

Correct, 3.3 uf if the driver is 8ohm = 6k, pretty damn high and will result in a 12k crossover point if you are putting a 4ohm tweeter instead.

Pretty high crossover points, but not uncommon since these are first order and basic/oem stuff... 1st order has a shallow roll off vs higher order, so if you step up to 2nd order you can bring the crossover point down. Benefit might be smoother sound, less cone break up from the mid as it's probably also crossoved over high. But, another thing that matters is the positioning of the tweeter in relations to the mid and the crossover point / polarity (phase) plays it's role here a well.

If you want to play with different crossover points, buy NP caps (non polorized) .

Here is a quick / easy online crossover calculator

http://www.the12volt.com/caraudio/crosscalc.asp#cc

For more serious work usually crossovers are emulated using software (such as Leap for example) to take into consideration various other drvier parameters and then measured with a calibrated mic / system to verify the freq. response and of course by ear.

[StereoInstaller1]

For more serious work usually crossovers are emulated using software (such as Leap for example) to take into consideration various other drvier parameters and then measured with a calibrated mic / system to verify the freq. response and of course by ear.

and for way less serious work you hack on it with a radio shack soldering iron and hope for the best and really don't give a shit the whole time, but got lucky this time.

In my case it was "Hmmm. Speakers are already out, iron is hot, WTF, lets try it".

Ever hear a really bright co-ax in the stock location on an E30, like a Memphis PR or a Diamond? You can't hear jack over about 5.5K, and it is drastically rolled off above even 3.5Khz...so letting the poor little 20 year old mid thrash around from 120Hz to whatever it thinks it wants to roll off at works amazingly well.

35X2 of Alpine mid-90's (MRV-F350 IIRC) power from a Kenwood high-volt deck, BTW.

Jean, I swear...I will drag your crazy ass up here, one of these days. Another "one of these days" I am gonna be able to do full FFT in my shop. You, me and a couple other guys from here will spend a day or three audio tweaking, just for fun.

[Morrison]

Yeah, I pretty much just wanted to try something different without going all out and spending a lot of money. On that note, the tweeter I decided to try is the Dayton ND20FA-6. It's a 3/4" soft dome rated at 6 ohms and 90 db sensitivity. Also they are only $7.96 ea. so even if they are awful I'm not out much. I'll try them with a 4.3uf cap and see how they do.

[Jean]

Let us know what you think of it. 3/4 will have a wider "sweet spot" usually over a similar "1" but will require a higher crossover point (look at the Fs # and multiply it by 3 to be on the safe side). If it's too bright, calculate a simple Zobel circuit using 2 resistors to quite the tweeter down.

Luke - haha, not sure if it's a good idea as I'll want to put a system in my car and it's been difficult not having any tunes in the e30, m30 makes up for that to an extent lol.