You may have had better luck delaying the forward facing sub for maximum rear rejection.
Actually you will be maximum rear rejection when in the "Cardioid" mode vs the End fire.Cardioid delays the rear sub and has the rear sub inverted polarity.End fire has both in polarity and the front one delayed.Cardiod has the most rear rejection, and has less "punch/impact out front due to the higher freq of the bass region being cancelled.Endfire has the best sonic character (like a single box), but does not have as much rear rejection or as wide a cancellation bandwidth as the cardioid setup.Both need around 4' separation (for a starting point) from the sound source of one cabinet vs the other.
"Both need around 4' separation (for a starting point) from the sound source of one cabinet vs the other."Ivan - This sounds like a conflict of what was discussed above. Essentially you are saying that the setup in the original thread post above won't work?This is why I am confused - there are all sort of theories on this. But I know you know the physics.I really never have the room for endfire array and usually need more cancellation. My focus is on the gradient / reversed-phased-delayed cardioid setup. In that case, the boxes need to begin by being 4ft apart??--Kevin
The "theory" is that the spacing is 1/4 wavelength and the delay match the spacing.4' is 1/4 wavelength of 70Hz. Kinda the "center" of bass-if you are looking at 40-100Hz being the sub region.OF course if you want to move the cancellation lower-you need larger spacing and more delay.As usual-it STARTS with defining what you are "looking for".THEN designing the system towards that goal.NOT, taking a setup and "hoping" it will work for a particular situation.But understanding HOW it works, and what the variables are is VERY IMPORTANT in any sound system DESIGN. Vs the LAR (Looks About Right) method that most people use.
Ivan - So what you are saying is, the setup pictured at the top of this thread would not work to cancel low freq effectively?I'm not looking to stack up a bunch of stuff, make several fancy settings and call it good. I'm trying to find out if what I'm seeing here on PSW and being shown as a way to effectively manage low frequency behind subs is actually effective.If the boxes need to be 4' (or whatever distance per desired cancellation) apart, then also reversed, out of phase and time-delayed, so be it. But that isn't what is pictured and given as the solution in the first thread post. In most cases I don't have the space so I can just forget about implementing that way unless an unusual situation arises.Again, I appreciate the discussion and education.--Kevin
2. A cardiod array has the speakers grouped together in stacks of three ( typically ) with the center speaker facing backwards and the polarity inverted. The typical approach to this method is to delay the rear facing speaker in order to tune for the desired maximum rejection. The downside is that the rearward facing speaker is out of phase with the forward facing ones and does not couple with them.
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