If I understand it correctly, an impedance corrections curcuit (Zobel?) can be calculated quite precise when the driver’s Qes and Qms are available. But that is usually not the case when the driver is a compression driver, as in my case.

However, at the link given here:

http://www.the12volt.com/caraudio/crosscalc3.asp#zobel

there is an online Zobel-calculator that based on the description seems to do what I search for.

1. The calculator asks for the “Nominal resistance”. In my case, is that the 16 Ohm (because it is said to be an 16 Ohm driver), or the Re = 8.9 Ohm provided by BMS, or…??

2. Is the formula in the link the way to go, or should I rather do something else - and in that case what?

I would really appreciate your help – thanks!

Regards
Peter

• BMS 4592 ND

Thanks a lot for your reply!

I will look into your document, and I am sure I will learn from it - thanks!

I would really like to attend to your seminar at the Great Plains Audiofest, but since I live in Denmark, its quite a few miles a way:-(

I see that the Spice program is a zip-file. Do you happen to have link to an un-zip program at hand? Thanks!

Regards
Peter

Duke

While I think that your crossover paper is useful for the novice it is highly over-simplified and if naively applied would not yield the desired results.

Specific points are:

Driver inductances are never ideal - Leach and Vanderkooy both point this out, and your Spice model simply does not represent the actual impedance variations found in real drivers. This can be quite a pronounced effect. In my computer simulations I use the Leach model which works quite well.

Spice models only give electrical performance. In the real world we have to add in the acoustical performance of the drivers which adds a great deal of complexity, but ignoring it is highly erroneous. Thats why I don't use Spice for acoustical problems. For instance, any CD device must have a falling axial response which must be corrected in the crossover. This is not reflected in your designs or discussion.

The multiple impedance peaks in a compression driver are caused by reflections in the horn. A properly designed waveguide does not exhibit these higher peaks and as such allows for a much better crossover design as well as a much better directivity control. In short, if you have these peaks in your impedance curve then the horn is poorly designed and no crossover approach is going to fix that.

• Speaker Crossover Document
  
• Spice executable with crossover and driver models

I think that you are missing my point again.

The drivers Le CANNOT be done correctly in SPICE - read Leach and Vanderkooy.

The acoustic radiation effects - not simply the effect of the resonance on the impedance, but directivity and acoustic load (which has no electrical analog) cannot be done in SPICE. SPICE was never intended to do acoustics, and it can't.

• A two-port analogous circuit and Spice model for Salmon's family of acoustic horns. by W. Marshall Leach, Jr., Professor Georgia Institute of Technology

I use Spice to model the crossover, and that's it. My models do take account the transformation of mechanico-acoustic properties into the electrical circuit, but this is purely done to get a better model of the electrical circuit. It's not intended to model things like acoustic radiation pattern. The Spice models I made are used to give a better view of what's happening in the crossover circuit than simplified resistor-load models provide. But again, it's not an acoustic model nor was it ever intended to be one. If you took the time to look at what I've done before replying on it, you would see that.