In this blog post I test a new rear cover for the SB Audience 75CDN-T.
3D CAD files can be purchased here.
For technical drawing click here.
Testing
I decided to test the 75CDN-T on the ES-600 Biradial No.1978. This is a low coloration horn which will provide insight into the compression driver's performance.
Conclusion (Rear cover No.3075)
- Rear cover No.3075 improves certain performance aspects
- Upper treble is linearized
- FS lowers from 490Hz to 430Hz
- Burst decay and CSD plots improve (upper treble)
- 3rd and 4th harmonic distortion is reduced
- The rear cover slightly increases 2nd order harmonic distortion
- IMD is unchanged
For comparison's sake let's compare the 65CDN-T against the 75CDN-T with the stock covers.
Conclusion (Stock 65CDN-T vs Stock 75CDN-T)
- The stock 65CDN-T offers smoother frequency response in the treble region compared to the stock 75CDN-T
- Distortion is almost identical between the two drivers, with 75CDN-T having slightly lower H2
- IMD is superior on the 75CDN-T but only at the higher test SPL (95dB).