JBL 2395 lens + baffle

[Lee in Montreal]

I don't know if the question has been asked before. JBL's literarture mentions that the 2395 lens can be used down to 500Hz, providing a vertical baffle is used behind the lens. What size that baffle? I suspect that when the 2395 is placed on top of a 4520 scoop, the surface below acts as a baffle. Is that enough?

http://forum.speakerplans.com/uploads/1547/168043_184378331582846_100000320417952_511019_8979 35_n.jpg
http://www.hifiplaza.co.kr/porc_images/1266918054_jbl%204450a2.jpg

[Ruediger]

The lens is small in the vertical plane, compared to the wavelength of a 500 Hz tone. Sound gets diffracted even to the rear, at low frequencies the lens is almost omnidirectional in the vertical plane. The baffle shall reflect the sound which hits it by diffraction. It functions like a radiating piston, and You want that piston to beam. The piston must have the size of a wavelength or more. The more the better.

Ruediger