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Re: time aligning tweeters/mids question

Posted by patentguy on January 18, 2000 at 15:12:08:
Your efforts are commendable, and considering the scientific background that you possess, certainly not in vain or impossible. One of the inherent difficulties in time-alignment is the difficulty of determining where the acoustic center of the voice coil is. The problem, though not obvious, is that it is not always possible to determine where the voice coil is within the driver, hence my comment about iterative development. I have over the years built a few systems, but that was before the advent of MLSSA.
Back then I did as you have, but I used an iterative process. I used a flat baffled box and iterativly adjusted the tilt-back angle until the voice coils were essentially in-line (7 degrees). With the Dynaudio drivers I used, the off-axis response was quite good, so I did not need a stepped baffle to realize a time-alinment benefit.
I would highly recommend the addition of MLSSA analysis to your project because it will provide you with real-time feedback on phase through the impulse and step responses (when the system is phase-coherent you are there). As to digital implementations, you could probably use an of-the-shelf program like Matlab to design your filters, without extensive background research or education (I suggest "Digital Filters and Signal Processing" by Leland B. Jackson because it covers matlab and any book by Leon Couch because he is a genius).
Since you are probably comfortable with high-level description languages, I would suggest using Maple or matlab to write the code for the filter then dump it on an FPGA or an eprom. If you rely on your computer to run the filters you must consider that the noise and limitattions of the PC power supply will limit the outcome of your speaker system. This is a project worthy of your efforts much more so than a passive cross-over correction would be. Post your efforts over the months it will be fun to hear how its comming. My prior comments obviously did not dissuade you so Good luck-- sometimes the challenge really is the whole point. ;)