Gentle Slope
6 dB per octave overlaps a lot. It can sound smooth, but it does not protect a small driver very much.
Filter Slope Comparison Chart
Filter slope tells you how fast unwanted sound is turned down once it passes the crossover point.
Tiny Version
A steeper slope blocks unwanted sound faster. That helps protection and separation, but it usually needs cleaner crossover planning and better phase awareness.
6 dB/oct = gentle
12 dB/oct = common
18 dB/oct = strong
24 dB/oct = very steep
Attenuation Below Crossover
| Slope | 1 octave below | 2 octaves below | 3 octaves below |
|---|---|---|---|
| 6 dB/oct | -6 dB | -12 dB | -18 dB |
| 12 dB/oct | -12 dB | -24 dB | -36 dB |
| 18 dB/oct | -18 dB | -36 dB | -54 dB |
| 24 dB/oct | -24 dB | -48 dB | -72 dB |
Real Example At 80 Hz
If you cross a subwoofer at 80 Hz with a 24 dB per octave low-pass, then 40 Hz is one octave lower than the handoff and will be 24 dB down on the high-pass side. That is why steep slopes are useful when you need to keep unwanted sound out of a tweeter or midrange quickly.
Good Starting Zone
12 to 24 dB per octave is the normal car-audio range because it balances protection, handoff control, and practical setup.
Do Not Forget Phase
Steeper filters often need cleaner phase and polarity checks. The slope alone does not guarantee a smooth handoff.
Use Next
Pair this card with Crossover Frequency Quick Reference, Reading DSP Levels, Q, and Headroom, and the Q and Bandwidth Converter when you move from the picture to the actual DSP settings.