In audio crossovers, an octave refers to a frequency range where the upper frequency is twice the lower frequency. For example, an octave above 500Hz is 1000Hz, and an octave below 500Hz is 250Hz.
Octave and Crossover Slopes
Crossovers (both passive and active) have slopes that determine how quickly frequencies are attenuated (reduced) beyond the crossover point. These slopes are measured in decibels per octave (dB/octave).
Common Crossover Slopes in dB/octave:
- 1st Order (6dB/octave) – Gentle slope, allows a smooth transition but may cause frequency overlap.
- 2nd Order (12dB/octave) – Steeper slope, reducing overlap between drivers.
- 3rd Order (18dB/octave) – Even steeper, providing better separation.
- 4th Order (24dB/octave) – Very sharp cutoff, used in high-performance systems.
Octave Example in a 2-Way Speaker Crossover
- Suppose a 2-way crossover is set at 3kHz with a 12dB/octave slope:
- 1 octave below (1.5kHz) → The signal is attenuated by 12dB.
- 2 octaves below (750Hz) → The signal is attenuated by 24dB.
- 1 octave above (6kHz) → The signal is attenuated by 12dB.
Why Are Octaves Important in Crossovers?
✅ They determine how smoothly or steeply the sound transitions between drivers.
✅ Affect phase alignment and frequency overlap, which impact sound clarity.
✅ Help avoid distortion or unwanted resonances by ensuring each driver operates within its ideal range.
Would you like more details on designing a crossover with a specific octave slope?
