Phase Shift Reference
Use this card when you need the simple answer to "how much phase movement should I expect from this filter?" without digging through the full theory first.
Tiny Version
Higher-order filters rotate phase more. That is normal. The important question is whether both sides of the handoff still meet each other cleanly.
| Filter order | Type | Phase at crossover | What to remember |
|---|---|---|---|
| 1st (6 dB/oct) | Butterworth | plus or minus 45 degrees | Gentle overlap, small phase rotation |
| 2nd (12 dB/oct) | Butterworth | plus or minus 90 degrees | Common, but needs polarity awareness |
| 2nd (12 dB/oct) | Linkwitz-Riley | plus or minus 90 degrees | Same angle, different acoustic target |
| 3rd (18 dB/oct) | Butterworth | plus or minus 135 degrees | Stronger separation, more rotation |
| 4th (24 dB/oct) | Butterworth | plus or minus 180 degrees | Very steep, needs clean alignment |
| 4th (24 dB/oct) | Linkwitz-Riley | plus or minus 180 degrees | Popular because the acoustic sum is usually easier to manage |
Why LR4 Keeps Showing Up
LR4 is common because both high-pass and low-pass sections are down the same amount at crossover, and the pair usually sums into a flatter handoff than a casual Butterworth setup. That does not remove the need to check polarity and time alignment. It just gives you a more reliable starting point.