What I gather from your input is that a phas plug is pretty useless for midrange frequencies and below.

But, may beneifit a wideband driver intended to be used above 3kHz, like a Lowther 6" in the Azura horn.

Is there any benifit in using a phase plug for a driver intended to be used from around 150Hz and up to around 2kHz in a horn?

Looking at several pro drivers that use a phase plug. I see that they are mostly midrange types like the Beyma 6M180, that have a fairly high frequency extention of 6kHz or more.

Are there any specifications for a midrange, or midwoofer that would help indenify possible use for horn loading?

Thanks

Norris