Now that I have MD100's to go with the 160GT's, its come to the stage where I'm going to run them active. Mainly because I don't have the xovers for them.
Just wondering what crossover points people out there are running?

The wonderful thing about active is the capability to tweek and tune forever.

As a guide,

suggest crossing the mids to the tweeters at the original cut freq,
if you don't know it, check the freq response charts of the tweeter and woofer,
this will give you a good idea how low you can go on the tweeter.

Looking at them myself,

the Midbass has strong response up till 3khz, which after it has a peak then drops off,
the Tweeter has good response from 1.5khz upwards.

My suggestion is something like,

2khz @ 24db,
2.5khz @ 24db
3khz @ 24 or 18db
3.5khz @ 24 or 18db
4khz @ 24, 18 or 12DB

try all of those,
you may also want to do a combo, like Midbass LP 3khz @ 24db and Tweeter HP @ 3khz @ 18db

Try using both 18 and 24 db separately, and run through the Iasca test disk, espcially on stereo image
in some installs using 24 or 18db can make a difference to the staging. (depending on the x/over system too) 24 and 12db work identical and 18db and 6db work identical, it's just that sometimes one or the other can cause the speaker to play out of phase. So play with that. (obviously you can also run phase tests too, but i find stereo image tests it's easier to notice the difference at a instant)

Also, you may need to underlap or overlap X/Over points to achieve the right sound,
IE: LP 2.5khz @ 12db HP 3khz @ 12db ect.

Just play around, you pretty much can't damage the woofer,
but you can damage your tweeter if you go too low, and play too loud.

If the tweeter and mid are mounted together, a lower tweeter x/over point may be of less use,
where as if the tweeter is mounted up high on the dash, a slightly lower x/over point can be nice to enhance imaging and staging up high and in front.

Your going active.. look forward to months of tweeking, tuning playing..

Active is fun

Juls

dyn's X250 xovers are set to 2.8kHz. tweets look to have a 12dB/oct slope and woofers have a shallow 6dB/oct slope. well, that's how i interpret "1st/2nd order".

http://www.dynaudiousa.com/products/car/cross.htm

if you have 12dB/oct slopes, i would look at around 2~2.5kHz, underlapping them slightly.

2.8khz seems a little low for a tweeter with a resonant frequency of 1.36khz.

however the x-over is one octave above resonance (using 12db/oct) which is a minimum requirement for the safety of a tweeter.

personally id look at an x-over between 3k to 3.5khz @ 12db/oct. A x-over @ 3.5khz would ensure better power handling so this might be a smart move when using this tweeter active.

good interpretation shiny

don't forget also, if you use a lower crossover frequency, you need to make it steeper to avoid overpowering the tweeter.

approximately for the same slope,
@ 2kHz, tweeter gets about 25% of total power
@ 3kHz, tweeter gets about 15% of total power
@ 4.5kHz, tweeter gets about 10% of total power

Cheers guys.
The crossover I'm using is an Audiocontrol 4XS - 18dB/oct slopes.
I'll start somewhere around where they are crossed from factory, and work my way from there.
Thanks again

One thing to consider is that you may have to use different slopes on the woofer and the tweeter.

For proper acoustical summation of the sound, what really matters is not the electrical slopes of your crossover alone but the final acoustical roll off slope of the driver + the xover electrical slope.

This is why the Dynaudio factory xover uses 6 db electrical slope for the woofer and 12 db electrical slope for the tweeter, to allow for the different roll off rates of the woofer and the tweeter.

If you look at the Dyn published freq response for the woofer and the tweeter, you will see that the woofer natural roll off is much steeper than that of the tweeter. Hence by using 6 db and 12 db electrical slopes in their xover together with the natural driver roll offs at the xover frequency, the combined overall acoustical slopes Dynaudio is designing for is probably 24db/oct which is one of the better ones to use sonically.

If you simply use 18db electrical slopes for both tweeter and woofer then the combined acoustical slopes with the natural driver roll offs are likely to be non symmetrical which may not sound natural.

Good luck.

I use the MD100s in my own car and run them actively. They have always impressed me with their ability to play down to a very low F3 without undue power handling comprimise. I use a steep slope of at least 18dB per opctave and have no power issues with using a 3.2kHz F3. This way it helps pulling images upwards.

Are the tweeters incapable of playing lower then this with any sort of power handling? I haven't had any experience with this, but I cross my tweeters(diff brand of course) over at 1250hz 24dB slope and have found the tweeters sound much nicer this way...

I guess it's different when you have a mid to 'fill in' between the MB and tweeter though.