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<blockquote data-quote="Peter Morris" data-source="post: 148273" data-attributes="member: 652"><p>Re: FIR filters</p><p></p><p></p><p></p><p>Here’s a simple answer –</p><p></p><p>The phase of the low pass and high pass bands of a LR crossover will match each other perfectly.</p><p></p><p>The frequency and phase response of the speakers will not be perfect. Accordingly the real world amplitude and phase response of the crossover plus speakers will not look like your picture.</p><p></p><p>This is one reason to use out of band PEQ. You can get each driver to behave correctly before applying the crossover.</p><p></p><p>There are further complications when you combine a horn with a cone speaker. The horn diaphragm is pressure load and the cone speaker is mass loaded – mathematically there is roughly 90 degrees of phase difference between these two.</p><p></p><p>As a rule of thumb (IIR) crossovers with slopes of 24dB per octave or less sound fine, crossovers with slopes higher than this e.g. 48 dB octave don’t sound as good. </p><p></p><p>In my experience, all things being equal (other than phase), both IIR crossovers and FIR crossovers both sound excellent. If the speaker has a flat phase response it will not really sound noticeably better, just more real.</p><p></p><p>One thing the FIR approach to processing speakers does is give you more power to correct things, you can make the amplitude and phase response more ideal and hopefully find a better compromise.</p></blockquote><p></p>
[QUOTE="Peter Morris, post: 148273, member: 652"] Re: FIR filters Here’s a simple answer – The phase of the low pass and high pass bands of a LR crossover will match each other perfectly. The frequency and phase response of the speakers will not be perfect. Accordingly the real world amplitude and phase response of the crossover plus speakers will not look like your picture. This is one reason to use out of band PEQ. You can get each driver to behave correctly before applying the crossover. There are further complications when you combine a horn with a cone speaker. The horn diaphragm is pressure load and the cone speaker is mass loaded – mathematically there is roughly 90 degrees of phase difference between these two. As a rule of thumb (IIR) crossovers with slopes of 24dB per octave or less sound fine, crossovers with slopes higher than this e.g. 48 dB octave don’t sound as good. In my experience, all things being equal (other than phase), both IIR crossovers and FIR crossovers both sound excellent. If the speaker has a flat phase response it will not really sound noticeably better, just more real. One thing the FIR approach to processing speakers does is give you more power to correct things, you can make the amplitude and phase response more ideal and hopefully find a better compromise. [/QUOTE]
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