Electrical vs Acoustical Crossovers: What Every DSP User Must Know

• ›• ELECTRICAL crossover = what you program in the DSP (HPF/LPF with frequency and slope)
• ›• ACOUSTICAL crossover = what you actually measure with the mic (RTA/REW)

98% of the time, they are NOT identical. This is normal and expected.

The speaker has a NATURAL roll-off that adds to the DSP filter:

Concrete example:

• ›• Tweeter natural roll-off at the bottom: -18 dB/oct (physical characteristic)
• ›• HPF in the DSP: LR4 = -24 dB/oct (electrical filter)
• ›• Measured ACOUSTIC slope: -18 + (-24) = -42 dB/oct (what the mic sees)

Another example:

• ›• Woofer natural roll-off at the top: -12 dB/oct
• ›• LPF in the DSP: LR4 = -24 dB/oct
• ›• Acoustic slope: -36 dB/oct

The acoustic slope is ALWAYS steeper than the electrical slope.

In calibration, we care ONLY about the ACOUSTIC crossovers (what the mic measures). The electrical crossover in the DSP is a tool to reach the acoustic target.

Goal: each driver's measured response should match the target curve (typically acoustic LR4 at the crossover point = -6 dB).

Practical consequence:

• ›• The electrical HPF must be set to PROTECT the speaker (safe frequency), nothing more
• ›• The acoustic slope is shaped by combining the DSP filter + EQ + the driver's natural roll-off
• ›• Two identical systems can have very different electrical crossovers and sound the same — it's the acoustic response that determines the sound

The #1 beginner mistake: wanting the electrical crossover in the DSP to exactly match the acoustic target.

Example of the mistake:

"I want an LR4 acoustic slope (-24 dB/oct) at the driver's crossover point, so I set an LR4 HPF at that exact frequency in the DSP."

Reality: with the tweeter's natural roll-off, the acoustic slope will be much steeper (-42 dB/oct or more). To get -24 dB/oct acoustic, you might need a BW12 or even LR2 filter in the DSP.

The only way to know: measure and iterate.