Zaph|Audio - SB Acoustics 2-Way : Crossover Software Alternatives
Crossover Software Alternatives
I haven't paid much attention to covering specifics of the software used to design the crossover itself. There are good reasons for that. Each software package has its own advantages/disadvantages. There are many capable software products available. I've used several during the course of this design for various aspects. Some packages can almost do it all.
My intent here is not to provide any sort of detailed review of any of them. It is to show some details of certain software used, demonstrate equality of results and to provide some files that you may download. You may use them to either reproduce some of what has been shown or to make your own changes if you care to do so. They should be usable by many other software packages. You aren't limited to those discussed here, but the PCD will be the focus, since it is the freely available software.
This has two benefits to all of this. One, you may get some hands-on experience if you so desire. Two, and more importantly (!), it will help relieve me of requests for changes that often arise when designs are posted. With the files that you'll find here you can do it yourself!
The older software, though still available, is likely not going to be used by more recent DIYers. The results will still be very similar if the target is the same. The software that I used for optimization, CALSOD, has more flexibility than the Passive Crossover Designer (PCD) that will be shown here. It is an excel spreadsheet made freely available at a site that sponsors it for the auther, Jeff Bagby. However, it does most of what is needed and as we'll see, yields results that are very, very close. Another software package used, SoundEasy, is as flexible if not more so and has the added benefit of including a measurement capaility. I used it primarly to audition the crossovers using its Digital Filter funtion. This circumvents the need to build the crossover until the final design is ready. You'll see comparisons of the results of all of these here that should make it clear that any of them will do the job as the goal was defined here.
Crossover Example
Consider the 2000Hz LR4 crossover. The values obtained were then put in to SoundEasy for autitioning. They were also entered into the PCD. All of those software packages can export the summed response. We'll compare all of the results.
First let's look at the CALSOD results since this is where most of the crossover design was done. This is close to a standard Linkwitz-Riley 4th order acoustic crossover.
Now let's look at the same schematic when set up in the PCD. It looks fairly close, but we really can't tell with certainty compared visually. Coincidentally, the graphics output by CALSOD and the PCD in one of its modes is close to the same dimensions, making visual comparison easier.
Finally, let's look at the same schematic in SoundEasy. Again, it looks pretty close, but given the difference in scale, it's harder to compare visually. SoundEasy could be altered by window sizing, but that just takes up more time.
So how close are they? The summed responses were exported from CALSOD and the PCD, then imported and overlayed using the free version of Praxis (hint: it has one of the best GUIs I've seen in speaker measurement/post-processing software). The CALSOD output is yellow, the PCD output is blue. The results show nearly identical response. Nearly.
Why is it "nearly" and not "exactly" the same? The only difference in the components is in the inductor resistances, primarily traps. Due to real estate issues (the PCD GUI is pretty much filled up), the resistance of the inductor cannot always be entered. Jeff would add it if it didn't require so much change. This will have an effect on both the trap and the total insertion loss. The impact will vary, but in this case it's minimal and likely will be for most crossovers that use a parallel trap in series. It's a minor issue most of the time so don't be concerned with that.
David L. Ralph © 2009