Monopole or Dipole surround speakers?

[Sir Terrence the Terrible]

I thought side di-poles were supposed to do the opposite. With the sound radiating front and rear an ambient or surrounding effect should be the result.

I've use Klipsch RS-3 side surrounds in my 5.1 system. I also use them as side surrounds in my 7.1 system with monopole rear surrounds. A wall of sound has never come to mind when thinking or listening to the surround channels.

The RS-3s are specifically designed (as well as many other models) with the mid driver facing the listening area and two tweeters (horn-loaded in the case of the RS3s) facing front and back. The result is a null region facing the listening area with diffuse ambient sound front and rear. Diffuse, ambient, surround all sound to be more omnidirectional than a more specifically dimensional wall of sound.

Bfalls,
The RS-3 are a bipolar design, not a dipolar. Their forwards and rearward tweeters are both in phase at all of the frequencies they cover. There is no null in their outputs, just 120 degrees of sound coverage over the operating range of the speaker.

[bfalls]

Bfalls,
The RS-3 are a bipolar design, not a dipolar. Their forwards and rearward tweeters are both in phase at all of the frequencies they cover. There is no null in their outputs, just 120 degrees of sound coverage over the operating range of the speaker.

Well, you learn something new everyday. I did some research and found an explanation of the surrounds on the Klipsch site. They've always performed very well. I can't say I've found any fault with them.

I thought about purchasing the Emotiva ERD-1 surrounds since they're on sale @ $249/pr, but can't see how they would make an improvement. I may purchase them anyway to complete a 5.1 system with my ERM-1 mains and center.

W.D.S.T.


1) Klipsch Wide Dispersion Surround Technology surround speakers take a different approach to surround coverage than dipole and bipole surrounds.

a) Dipole models place drivers out of polarity to create a null on one axis of the speaker. It is popular to sit in the null, thus the loudest sounds come from indirect radiation from the speaker. A dipole, used in this manner creates a diffuse and non-localized rear sound field.

i) Some drawbacks to dipole surrounds include that the rear sound field is not confined to the rear. As much radiation is radiated forward as rearward.

ii) A dipole also depends on other surfaces in the room to reflect the sound to the listener.

iii) A dipole can only create a diffuse rear sound field.

iv) Finally, a dipole is very inefficient at low frequencies, as the out of phase bass cancels.

b) Bipole models place drivers on several faces, with the idea that the radiation is equal in all directions, like a point source.

i) The problem is that the drivers interact, and actually radiate sound very erratically, with a different frequency response in each direction.

ii) The sound field created is not coherent and as a result is not very realistic.

c) Klipsch WDST surrounds are very much like a professional concert array. The high frequencies, made directional by the horn, are arrayed at the proper angles to provide even coverage, or with the same frequency response in all directions. The single woofer is crossed over where it is omni directional, thus creating a system which truly radiates sound equally in all directions.

i) WDST models provide balanced direct and reverberant sound field to listeners. Since the response is the same in all directions, the reverberant sound filed reaching the listeners from other directions, is balanced spectrally with the direct sound, creating a coherent, realistic rear sound field.
Trey Cannon
Klipsch Audio Technologies
Associate Engineer

I use these for the sides in one 7.1 system with monopole rear surrounds.