After more investigations it seams to be a common understanding that placing two woofers vertically to each othre is no good idea when it comes to comb effects if both woofers play above 250hz.
Refer to MeyerSound
“The X-800 houses two Meyer Sound long-excursion 18-inch drivers in a tuned, vented cabinet. The X-800 output rolls off well below 250 Hz, avoiding any adverse comb filtering effects that could be generated by the proximity of the dual drivers.”
Calculated the frequency response using Tolvan caluclating program shown no dip and very little effect on the frequency response abov 300hz at a 4m distance to seat due to comb filtering effect ? No dip could be seen.
Tolvan also show that the dB effect of using 2 woofers instead of one on a baffle 96cm width compared to 48cm which will be increased about 2-3dB at 30hz and also lowering the start of the baffle step about 100hz, from about 350hz to 250hz.
By using two woofers instead of one will the speaker be more directive i.e will the horisontal directivity be more pronounced. This is what JBL claim and mentioned as the reason for crossover one woofer at 150hz. The midrange/tweeter JBL horn have about 90 degree dispersion as the Altec 511B.
Any problem with the disperison when using two woofers compared to the horn ? How much will it change ?
Are there any other Acoustic Elegance options than the Dipole 12,15 or 18” that may be considered in these application.
I.e open baffle below 1000hz an Acoustic Elegance Woofer/Midwofer, and above 1000hz Altec 511B horn.
What I am looking for is the best Acoustic Elegance unit with the best midrange up to 1000hz in an open baffle but I am not looking for
maximum SPL. (One or two EA units in an open baffle).
I read about the LO15 with cloth surround for better midrange.