This may not be the right place to ask this question but I'll give it a shot anyways. Maybe someone here is an audiophile.

I'm using a DSP called Audison Bit One HD which uses FIR filters for crossover and EQ. They recently included all-pass filters which allows me to adjust the phase of the crossover point. I'm wondering if anyone here knows how this will benefit for room correction.

I know what an all-pass filter does but I'm not sure how it could be useful with FIR filters which is a linear phase filter. Why would I want to adjust the phase of the crossover point for?

The manufacturer is no help.

  • $\begingroup$ Isn't there an option for infinite impulse response (IIR) crossovers? $\endgroup$ – Olli Niemitalo Aug 3 '19 at 10:18
  • $\begingroup$ Yes. I could choose between using IIR or FIR $\endgroup$ – Tony N. Aug 4 '19 at 13:25

Allpass filters are very helpful in automotive mainly for getting the imaging dialed in. You often need to time align the contributions of different driver groups (left, center , right) at a specific listening position. Due to the complicated acoustics of the cabin. the delays are often dependent on frequency and so all passes can be very helpful in correcting this. Allpasses in cross overs are typically not that useful, since the range of overlapping frequencies is pretty narrow and you can typically get by with a single delay

  • $\begingroup$ Aki Mäkivirta, Juho Liski, Vesa Välimäki, "Modeling and Delay-Equalizing Loudspeaker Responses", November 2018, Journal of the Audio Engineering Society 66(11):922-934 found that, for a three-way system, FIR group-delay equalization at mid and high frequencies worked better than a bulk delay or full-range group-delay equalization. $\endgroup$ – Olli Niemitalo Aug 4 '19 at 19:47

Audison Official video "New bit One HD 2019 edition unveiled at CES 2019" explains about Channels EQ:

All-pass filters have been introduced, very useful for matching phase response between active speakers.

  • $\begingroup$ I saw that video. It would be nice if someone here could elaborate on how I go about doing so. What steps should be taken to utilize an all-pass filter. I have REW and UMIK-1 mic. $\endgroup$ – Tony N. Aug 6 '19 at 8:13

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