Please help with unknown crossover

[norriemal]

I picked up some homemade crossover boards that I thought were decent. Van den Hul wiring with just a large air core inductor on the LF. I have no way of measuring it. The HF has a Philips 6.8K 100 MKC capacitor in series, a JTM 4R7 5% wire wound resistor in series and a 10W 10 ohm wire wound ceramic resistor in parrallel.

For someone with experience in crossover manipulation what is the ballpark crossover frequency in such a simple crossover with a 6ohm or 8 ohm tweeter. I have the crossover in a little sealed box with a Monacor SPH-174 KE which sounds good enough to try mated with a better tweeter than the cheap one I threw in to test it out.

I have a nice SEAS that will cross low but I'd like to try an Emit K that would have to be crossed a bit higher.

Any advice on ball park crossover as is. If I know roughly how high the inductor is letting the mid bass work I can mess around with a dedicated HF for the tweeter at a later stage.

 

[davidsrsb]

The REW impedance measurement jig is simple to setup and will measure your inductor

Impedance Measurement

This sounds like a really minimalist crossover, no baffle step correction and Epos like tweeter

 

[norriemal]

Thanks for that, looks like that jig will come in handy. I was just playing with bits I have lying around and this mid bass driver was previously in a transmission line and I wasn't convinced by it. It is said to work well in a small sealed enclosure and has a very flat response so I thought it was worth a try in a very small enclosure. I am really enjoying it even with tizzy mismatched tweeter so I want to give some more effort to getting the best out of it. Cabinet is 20 x 22 x32 cms. So very small.

 

[irb]

Have a look at the crossover calculators on the MH Audio website. But bear in mind these kind of calculators give a very rough estimate only. The impedance of real drivers isn't a straight line (except in very few special cases). The tweeter cap (6.8 uF surely) would probably give a 4kHz 1st order roll off with a 6 ohm tweeter.

 

[norriemal]

Thanks for that. Am I right in thinking that the HF has 2 components in series so will be a 12db rolloff?

 

[sailor]

From your description you have one reactive component in the tweeter circuit which mean it's Ist order = 6dB/octave. The series/parallel resistor combo are to attenuate the output to the SPL of the woofer.

XO design is a bit more complicated than just wiring in a different tweeter. If you want to try something else then choose a tweeter that provides an impedance plot then go online and find a simple notch filter to flatten its impedance. A text book calculation will now work predictably. If you don't notch out the rising impedance the TBC will be way off.

 

[norriemal]

Thanks to those who have tried to give me a bit of guidance, it is much appreciated.

I can feel myself entering the rabbit hole. What started as a simple experiment now has me trying to design a crossover with all that learning curve to slide down.

I have a couple of pairs of Allison AL-100 and Al-110 that have the 6.5" woofer that is the same in higher end models. It is run with no crossover in the 100 and a simple inductor in the 110. The 110 has the "nipple" tweeter. So I thought that putting the "better" crossover I had lying around in the 100 would at least improve the woofer and I could mess around with the tweeter. I then replaced the Allison 4 ohm woofer with the 8 ohm Monacor and the speakers have come to life to the extent that I now want to improve the tweeter and make myself a nice pair of small speakers. So I will be taking measurements and having a go at a tailored crossover design and see if I can do them justice.



Allison AL-100 crossover

Allison AL-110 crossover