Don't know anything about the Townshends. But when WHF reviewed the Tannoy ST50 Super Tweeters years and years ago, they reviewed very well. Even at £700.
I believe that they remarked about the percieved extension in the bass, an unexpected finding for a super-tweeter.
Whether this trait would apply to all S.Ts, or is specific to the Tannoy's, I couldn't say.
I'm sure others will chime in in due course.