Question about horn db gain

[16hz lover]

Sorry but I'm a newbie on horn system design and was wondering if there is general rule of thumb that can be applied to W style bass bins as far as how many db's of additional gain you achieve over the sensitivity of a woofer?

If I put a 95db sensitivity driver in a W style horn bin, what will the new sensitivity level be?

Thanks in advance and yes, I did a search.;)

[Hoerninger]

what will the new sensitivity level be?...;)
It will rise due to
1. more directivity
2. improving the lower end especially with high Q speakers
and the most important
3. air flow transformation (?) with a smaller throat compared to the cone area.

For real numbers use Horn Loudspeaker Response Analysis Program (http://www.audioheritage.org/vbulletin/showthread.php?t=12810&highlight=mcbean) by David McBean.
__________
Peter