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<blockquote data-quote="Peter Morris" data-source="post: 147988" data-attributes="member: 652">Re: FIR filtersI don’t have a background in signal processing&nbsp; … so this thread has made my head hurt trying to remember all my university mathematics … Hilbert transforms and all that stuff …&nbsp; but on the plus side it’s given me a few new ideas regarding processing the DIY&#039;s ... so thanks everyone for a great thread; can’t wait to see what Michael and Frank finally come up with.Just to add a bit more to Arts post …. If you look at how a FIR filter is implemented using a bunch of delay taps, intuitively a crossover (FIR) will require a delay of more than the period of the crossover frequency. If you want the slope of the filter to be steep, you will require even more time.I assume your question is to some extent relating to the DIY&#039;s you have built / processing.&nbsp; What I have done is use a short FIR time of 2.5ms in the Lake. This allow FIR linear phase crossovers as low as 500 Hz for the low/ mid and mid/hi. A FIR crossover for the subs required too much time so I have used a standard IIR LR crossover. I processed the subs separately and it’s important to remember the high-pass filter protecting the excursion limit of the bass drivers as well as the crossover slope and frequency will affect the time alignment.&nbsp; I also used some all-pass filters to match the phase response shape / slope of the sub to the phase of the DIY at the crossover. By doing that you will get the correct LR summation at, and either side of the crossover.</blockquote>

[QUOTE="Peter Morris, post: 147988, member: 652"] Re: FIR filters I don’t have a background in signal processing … so this thread has made my head hurt trying to remember all my university mathematics … Hilbert transforms and all that stuff … but on the plus side it’s given me a few new ideas regarding processing the DIY's ... so thanks everyone for a great thread; can’t wait to see what Michael and Frank finally come up with. Just to add a bit more to Arts post …. If you look at how a FIR filter is implemented using a bunch of delay taps, intuitively a crossover (FIR) will require a delay of more than the period of the crossover frequency. If you want the slope of the filter to be steep, you will require even more time. I assume your question is to some extent relating to the DIY's you have built / processing. What I have done is use a short FIR time of 2.5ms in the Lake. This allow FIR linear phase crossovers as low as 500 Hz for the low/ mid and mid/hi. A FIR crossover for the subs required too much time so I have used a standard IIR LR crossover. I processed the subs separately and it’s important to remember the high-pass filter protecting the excursion limit of the bass drivers as well as the crossover slope and frequency will affect the time alignment. I also used some all-pass filters to match the phase response shape / slope of the sub to the phase of the DIY at the crossover. By doing that you will get the correct LR summation at, and either side of the crossover. [/QUOTE]

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