Background
My previous room had a layout where dipole surrounds mounted on the side walls worked perfect. Back then they were Paradigm ADP-150’s. These were a very well designed well built dipole speaker. New home and new room dictated changing back to a monopole surround. After a re-model of the room the layout is once again suitable for a dipole surround. Too bad the wonderful 150’s were sold off a long time ago. A little patience resulted in finding a really good deal on some newer ADP-190’s to try out in the new room. Compared to the clunky cabinet of the 150 the 190 is a much sleeker looking unit, score one point for the spouse approval factor, minus two points for their design. I bought them used and upon receiving them I noticed they were not marked left or right as expected. This seems odd. Checking with Paradigm and other owners of these confirmed they are not marked for specific left and right sides. Being the curious type I cracked them open and traced the circuit. They are indeed a dipole design but not a traditional dipole. When mounted on the sides they sound “off” compared to the older adp-150 in my opinion.
Normally a dipole is configured so the drivers facing the listening position are positive or normal polarity. With the ADP190 only the speaker mounted on the left side will be like this. The exact opposite happens for the speaker mounted on the right side of the listening position as shown by the illustration.
But does this really mess with the sound? If your main left and right speakers were wired like this you would not like it. Stereo imaging is completely lost, vocals that should be easy to pinpoint are not and bass response is weak. Reverse the polarity to one of your main speakers and try it out. This analogy of reversing polarity to a main speaker also applies to a dipole speaker. The same sort of effect happens when the rear drivers have reverse relative polarity to the front facing drivers. One other neat thing occurs to create the diffused sound associated with dipole surrounds. When sound is produced from the rear drivers there is some cancellation but much of the sound will reflect off the back wall and radiate forward. By the time the sound travels back to the ears o f the listeners the extra distance traveled has allowed enough of a phase shift to be back in phase with the sound radiated from the front facing set of drivers. This delay helps to trick your ears into making the sound difficult to localize.
Getting back to the question of does this type of design sound good. Since we are dealing with a surround speaker it’s a matter of preference. Due to the opposing overall polarity from the left and right speaker I find the sound more confusing instead of diffusing. If current sound processing was more like Dolby Pro-Logic of old with its mono surround track and limited bandwidth these would be ideal. With current multi channel processing I think the surrounds should have more directivity than the ADP190 provide as designed. If nothing else this design is why the automated sound correction algorithms like Audyssey show the right surround as having reverse polarity when it’s wired correctly.
Super simple thing to try. For the right speaker only, reverse the polarity of wires connecting the amplifier to the speaker. Now you have a more traditional dipole setup.
If you tried this and like it, the internal wiring is quite easy to change making the speakers a permanent traditional dipole and not have to worry about reversing the input polarity to the right speaker. This also opens the door to going a step further and wiring in a selector switch to go from dipole to bipole. Doing any of this means opening them up and monkeying with the internals. By doing this modification you do so entirely at your risk as it is very easy to damage them permanently.
Fortunately the speaker you choose to be the left side does not have to be touched unless you want to wire in the selector switch option. The factory wiring puts the forward drivers with normal polarity and the rear drivers reverse polarity. Only the right speaker needs to be altered. For this speaker all we need to do is flip the wiring leaving the crossover from one set of drivers to the other. From the crossover the red/black and yellow/black wire pairs are the “in phase” or normal polarity set. The red/white and yellow/white wires are the “out of phase” or reverse polarity set.
This is where it gets interesting. These can be wired so you can switch them from dipole to bipole. This can be useful for working with room placement or your current setup forces the surrounds to be mounted on back wall. If you have a 6.1 setup a single ADP190 in dipole mode would be an excellent centre rear speaker.
Drill a 6mm hole between the banana jacks to mount the switch. You want the switch to fit in the terminal cup so it doesn’t interfere with wall mounting. It also has to be in a location so it doesn’t stop the back of speaker from going into place correctly. Keep in mind there are 12 wires connecting to it.
Here is the wiring diagram for the switch. You will have to unsolder the red/white and yellow/white wires from the crossover and solder in some hook up wire in its place. The wires removed will be soldered to the switch and connected once again to the rear facing drivers.
Very important to note here. The wiring diagram shows the red and yellow from the crossover being the positive wires and white is negative. This is in terms of the drivers themselves. The woofer positive is the red wire with the larger spade terminal and the tweeter positive is the yellow wire with larger terminal.
In reality the red and yellow wires coming from the crossover marked as (+) are actually the negative in terms of the crossover circuit. When the selector switch connects these sets together the rear facing drivers are now wired in reverse polarity or dipole mode. When the selector reverses the polarity yet again the rear facing drivers are now wired normal polarity or bipole mode. Phew.That's a wrap for this one. Hopefully someone will find this useful.
lord_darkhelmet at accesscomm dot ca