Personal project. I measured the bass module, designed a TL074 filter with three selectable corners, and built the board and enclosure.
The challenge
The module’s existing bandpass ruled out the original crossover plan. Bench testing also caught a missing bias path and, later, a fault between the level pot and output jack.
Results
- Measured corners: 94.9, 136.9, and 179.0 Hz, within 0.2 dB of the model.
- Filter-stage noise: 58 µV rms, instrument-limited.
Current status: Filter and polarity stages verified. The output-jack fault and in-room acoustic measurements are still outstanding.
