Horn vertical spacing

SoundRight

Member
2010-07-28 10:47 am
Wasn't sure wether to post in exotics or this forum. Clearly even with relatively large mid horns (around 800Hz) it is impossible to get the acoustics centres close enough from say a 15" driver to avoid lobing.

I know a LR crossover will give me "0" degs polar tilt at crossover with time alignment but I am sure I have seen articles that explain how to use the dispersion angles of the horn to minimise vertical spacing problems when you can't get the drivers close enough?

Anyone point me in the right direction?

Cheers....
 

SoundRight

Member
2010-07-28 10:47 am
Thanks but not about matching horizontal dispersion, it's about lobing from not being able to get the horn centre close enough to the lf driver acoustic centre.

Having looked again I see that Pi speakers has written about this using the -6dB of the vertical dispersion...
 
You can use phase offsets between drivers to direct the output through the crossover range - delaying the woofer a little will direct the sound downwards a little.

Given that, when mid horns are in use, the system can safely be considered far-field, you can probably design for a ~20 degree vertical window and live with the fact that those standing right under the stacks won't hear a bit of lower midrange. The people standing right under the stacks don't care, anyway.

FWIW, large mid horns will reach down to 200Hz. 800Hz is almost compression driver territory.

Chris
 

SoundRight

Member
2010-07-28 10:47 am
Thanks...These are cd horns and for more near field application, 90 x 40, 500Hz cut off, so actually rather more than 40 degs at these frequencies! Pi speakers talks about using the "edge" of the dispersion and to put the crossover in the nulls? They will be dsp controlled so no problem with true delays, phase angle or filter slopes. Guess measure it with the horns at different heights could be a way forward....!