Tweeter Crossover Development

The obvious place to start is by using a crossover that someone else has developed. In this case ORCA, the manufacturer of the Raven tweeters, has provided a 6th order crossover at 2000Hz that I decided to try. Putting the circuit into Calsod we see that it does a fairly good job of matching the ideal target response, except that in its lower octaves the output is a little depressed. It is actually very hard to tell at this point whether the lower end is depressed or the upper end is too bright. The target response level (the dotted line) is arbitrary and if it was lowered the data would look a lot better.

If we remove the 1 ohm resistor that is in series with this circuit, then the response looks a lot better.

However,looking at the filter shape and the resulting impedance we see that the filter transfer function (dashed line below) has a lot of boost at the low end, which can cause ringing, and the minimum impedance drops from an already low 1.7 ohms to an amplifier melting 0.8 ohms.

This crossover could be used with the resistor, and of course we don't know yet what it will sound like, so I filed it away for future use. If matching the phase of the mid requires that a 6th order crossover be used, then we can pull it out. Remember that the tweeter has a phase angle at the crossover frequency that is 90 degrees higher than that of the mid. Using different order filters on the two drivers is a very effective way of adjusting that phase difference.

October 15, 2000

I'm sorry, it has been nearly a year since I wrote the information above. I then put it aside and never got back to it. I am still waiting for my final dipole bass drivers, so then I can finish the real baffles and then remeasure them. My plan is to carefully record each step of this process and use it to complete this article. Meanwhile I have been listening to them on the temporary baffles with the Shiva for upper bass and the "Ugly" for deep bass. I have been very happy with this settup. I keep changing the level of the mid bass. One week I will run it up 3 or 4 db then I will decide it is to boomy and lower it again. Since this is coming out of the Shiva, and I intend to replace it with a Lambda when they become available, it has stalled this project. There is hope, as Nick says the dipole drivers are coming real soon.

Someday we will go build a fourth order crossover from scratch.