Rear surround sound speakers

[cmoyer]

I want to buy a Dolby Digital/DTS receiver, but I'm not sure if I need to invest in new rear speakers also. I have Cambridge rear speakers, but they are about five years old. They sound great on a Pro Logic system, but I'm not sure they'd work with a Digital system. The reason I'm skeptical is because they are bipolar instead of dipole, so sound isn't pointed in a specific direction, just ambient. Can anyone help?

[DigIt]

They will work - in fact some people prefer them. Doesn't Dolby or THX specify non-direct-radiating speakers? Anyhow, even though the surround information is discreet, it is not always directional - you'll still be getting a lot of ambient sound. If anything, you should be more concerned with their performance in handling the full frequency range (as opposed to the limited range of Pro-Logic). I'd say to hold off until you've demoed the system a few weeks, then decide if you're not satisfied with performance.

EDIT
FYI, here's the official Dolby answer:
16. Should I use bipolar, dipolar, or tripolar surround speakers?
Surround speaker placement, room acoustics, and personal preference are as important as the speakers’ radiating characteristic. These factors vary greatly, so Dolby Laboratories cannot recommend a particular speaker for home theater use.
Bipolar, dipolar, and tripolar surround speakers use speaker drivers aimed towards the front and back of the room to achieve a diffuse soundfield like that created by the multiple surround speakers used in movie theaters. Your room’s acoustics will effect these designs more than conventional direct-radiating speakers, which, when placed properly, can also make effective surround speakers.
www.dolby.com/tech/l.br.0011.DDFAQ.html#q16 (http://www.dolby.com/tech/l.br.0011.DDFAQ.html#q16)

A bit of a cop-out, but food for thought.

[This message has been edited by DigIt (edited December 13, 2000).]

EDIT
Just for the sake of completeness, I also checked THX and found this:
Surround Channel Loudspeakers
The purpose of a surround channel is to surround you with sound. The problem is that this is tough to do with just two speakers. Decorrelation takes care of Left/Right spaciousness, but what about wrap around envelopment? If a director chooses to place you in a wind storm, conventional speakers leave you with the impression that you're hearing the windstorm through two open windows.
The Home THX Diffuse Surround Speaker is designed to provide you with a "movie without walls" experience. It does this by painting the walls and the ceiling with sound. It sends very little sound towards the listener. The sound reflecting off the rooms walls and ceiling provides you with an enveloping soundfield, immersing you in the movie experience.
www.thx.com/consumer_products/home_speaker.html (http://www.thx.com/consumer_products/home_speaker.html)

They're selling their own speakers, but the analogy is appropriate for any speaker.

[This message has been edited by DigIt (edited December 13, 2000).]

[drmoze]

I also have a pair of Cambridge surrounds (the Surround II's) and they sound great with DD. They give a good sound fill and there is still directionality when intended (such as when a bullet in one movie scene bounces around the room!). One speaker is about a foot in front of the rear wall, mounted high up (6" below the ceiling), and the other is mounted on the opposite wall, similar position, but there's no rear wall so I mounted an angled sheet-metal baffle about 6" behind it. Both surround speakers are about even with the main listening seat (futon against the back wall).

You could always go with switchable dipole/bipole surrounds, but the bipoles work just fine, and have enopugh frequency response range to blend well with my front speakers (NHT SuperZeros).

[cloud]

I have the CSW Ensemble IV set up for my front, center and rear speakers. While they may not be the best speakers in the world they do a pretty good job and will do my fine until I can afford better speakers. They are actually pretty good for the price and quality, http://talk.dvdtalk.com/ubb/smile.gif

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