# Custom crossover for Hertz Dieci DSK 130.3



## bob808 (Oct 5, 2015)

Hello
I got two pairs of Hertz Dieci DSK 130.3 to install in my Renault Laguna II. Front and back doors allow only for 13cm speakers so I have to live with this.
After I installed them I must say I really like the mids that come out of this thing but the tweeters are killing me.
Now, the crossover that comes with the set is total crap. A second order passive crossover only for the tweeter. The crossover box has both outputs for tweeter and mid/woofer but the mid/woofer connection is just a straight wire from the input. The whole thing is a joke, using a ferrite core inductor and an electrolytic cap.
Now, the datasheet does state that the mid/woofer has a SPL rating of 93 and the tweeter of 94 but there's absolutely no attenuation/l-pad for the tweeter. As you can imagine, since the mid/woofer also reproduce the high frequency there's a highs nightmare in my car.
Now I took it upon myself to design a proper crossover for this thing, and I went for a second order Linkwitz-Riley alignment for both mid/woofers and tweeters.

I used the information presented here by Rod Elliott (great guy!):
(can't post links yet) will edit later if possible.
I will use air-core inductors from Jantzen (cheap and good) and a mix of film caps. For the capacitors that are inline with the signal for the tweeter I am going with a polypropylene cap - Jantzen Cross Cap (cheap and I buy them from the same place where I get the inductors).
For the caps in the mids section I'll go with Wima polyester caps (real cheap).
I decided to make an L-pad for the tweeters so I can tame them a bit. I haven't decided on the values yet as even if it's just a 1dB difference between the units, either the mid/woofer speaker is rated higher or the tweeter is rated lower. (yes, they don't say if the SPL is rated at 1W/1meter or 2.83V/1 meter. even so, doesn't matter as either way there's 1dB difference between them).
I did measure the tweeter and I found that it has a reasonably flat impedance. Wasn't expecting that but for sure it doesn't need a correction network.
The mid/woofer does need a Zobel network and it's calculated at about 3.1-3.3ohms/21-22uF. I did measure it's impedance and +3db frequency and the excel sheet spits out these values.
Since the original crossover has 3.5KHz crossing point I chose the same value for mine.
With the Zobel network in place the mid/woofer has an impedance of 3.25ohms at 3.5KHz and the tweeter has a nominal impedance of 3.97 at the same frequency (pretty accurate).
Now, with these values and the crossover frequency the components values came out like this:

For a 12dB/octave filter:

Tweeter: 5.73uF (5.6uF+0.1uF should do)
361uH (370uH inductor with one turn unwounded).

Mid/Woofer: 7uF(6.8uF+0.22uF should do)
295uH (300uH should do)

For the L-pad I will get 3 sets of simulated values.
For the nominal 1dB difference (with mid/woofer inductor losses accounted for):
Series resistance: 0.57ohms (0.56R available)
Parallel resistance: 18.74ohms (18R available)

For 2dB difference:
SR - 0.86R
PR - 11.04R

For 3dB difference:
SR - 1.12R
PR - 7.55R.

I will get the next standard values I find and make some tests and see how much I need to kill the highs.

Even with a separate amplifier there will be no need for higher than 5W rating resistors (for Lpad/Zobel).

The L-pad must be after the filter on the tweeter so there's no extra heat dissipated for no reason.
What I don't know for sure is...should the Zobel be before or after the filter on mid/woofer?
I attached the schematic for both filters.
Since on the front the mids are in doors and tweeters on the corner of the dash I need to make separate units for each driver. Hope I get to post some pictures with the finished product. I need to design the pcbs now.

- damn, can't attach pictures. need more posts. 
- double damn, can't link any pictures as well.


----------

