PrestonTom:

I do not see that rapid flare in your graph for the Klipschorn. I thought the Klipschorn also had a comparable rapid flare in the initial section.

There are a couple of possible explanations.
- First, I didn't measure a Klipschorn; I measured a Speakerlab K from a set of 1980 plans that I have. It is possible that the Speakerlab was not a completely accurate copy of the KHorn. It is also possible that the KHorn internal design changed with time. Or it is possible that the KHorn didn't actually use a rubber throat.
- Second, in the KHorn (Speakerlab K), the woofer opening is 39in², but that dumps directly into a horn whose throat is 78in². Perhaps that is what someone has called a rubber throat?

Greg

The original Klipschorn had a woofer baffle opening of roughly 6" X 12".  The baffle opening was cut in half at some point (probably in the 50's) to improve the upper frequency response of the bass horn.   

I believe the first horn section in the Klipschorn (between the baffle opening and the first bend) does flare faster than the last two sections, but I can't be sure.  My understanding of the purpose of a "rubber throat" was to control the horn resistance in a way such that it results in a flatter passband repsonse, but I've never seen any experimental evidence to suggests that it actually works. 

dbspl     

Excuse me

Why the hornresp parameters of pag 1 and 2 for k-horn are differents (see for ex Vtc)?

thanks