Playing warble tones I can not "see" the driver unload (in my favorite speaker) until the freq. is below audibility........but I know it happens.

Bob,
Thanks, The TL's I have built seemed much as you described.......they did unload, but the freq. was low enough it did not seem to matter.

I was under the impression this is a much bigger problem with a BR.......and also I am opposed to "wasting efficiency" with compensation networks or notch filters, when a single driver is used. Limiting the response below resonance seems reasonable to me in some cases. I don't do it as a general rule., however, because I seldom use a sub and simply prefer the sound of the speakers with no filters or components in the signal path, at least in the case of my "favorite" speaker. I do use a HP filter on my TV system........but those are ONE INCH full range drivers! They MUST be rolled off at about 200 Hz to have any power handling at all!
Thanks, guys
Ed