A slight increase in upper bass response was made to 3.2.1 compared to earlier versions by changing the 100-200Hz shelving high pass filter. This filter compensates for the woofer to midrange transition, since the woofer radiates into 2π space and the midrange into 4π space.
The bass output was increased by lowering the center frequency of this filter. A single capacitor change is all that’s needed. The result is a 0.5db increase in bass output at 100Hz, tapering off in either direction.
ASP response following the filter: 3.2.1 response (blue), earlier version's response (green), my preferred response (yellow)
After considerable listening time, I found the upper bass emphasis to be too unnatural, too insistent, too overpowering. The ideal setting for me is shown by the yellow trace in the graph, found by trial and error and extensive listening and woofer driver level changes.
Even so, a very few recordings still sound very muddy and dull with the new filter response. These are usually not very good recordings to begin with. I added a switch that toggles the response between the original response and my favored one, using it as a corrective filter for bass-heavy, boomy or muddy recordings.
Here is a list of recordings that benefit from the pre-3.2.1 filter response. I’ll add to this list from time to time.
- J.J. Cale – Naturally
Always a murky recording, perhaps intentionally so for a thick, oppressively hot and humid southern feel. With the mid-upper bass reduced, more of the lyrics can be heard clearly and finally deciphered. - Basia – Time and Tide
I’ve always wondered how this would have sounded loud in a dance club back in the 80s. In a clean system, the bass is overpowering. - Bruce Cockburn – High Winds White Sky (Rounder)
Bruce’s guitar sounds like a baritone guitar with the bass boost. - Schubert Octet, Atlantic Ensemble
Two double basses, or one plus a cello? Should we change the score with our equalization choices? - Holly Cole – Don’t Smoke in Bed
Overwhelming bass, booming, with the added bass. Don’t boost in bass. - Elis Regina & Antonio Carlos Jobim – Elis e Tom
This is one album that benefits from the midbass boost. Without it, the rhythm isn’t as punchy as it seems it should be.
Orion Gateway 