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Hello, I am trying to build a 7.1 home theater. Nothing special, I'm just converting my Basement (family room) into a nice theater.. I actually have 2 questions, hope you could help.

1st- I'm planning of buying Bipole speakers for my surrounds. I was originally going to use Bipoles from klipsch or Paradigm as both my surround sides and rears. However, I recently read that for the rear speakers, its better to use Monopole speakers and use bipole speakers as my sides.. Is this necessarily true? Will 2 Bipole speakers be too over whelming and will not give the surround effect?

2nd- I want to know how far apart can the rear speakers and side speakers be?

in my basement if I set up the 7.1 system how it's supposed to be ( with the sides being about 90 degrees to the listener) the rears would be about 6 feet apart.. Is that too close to each other that the two set of speakers will cancel each other and not create a good surround ? Or should I just do a 5.1 set up?
 

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Hello, I am trying to build a 7.1 home theater. Nothing special, I'm just converting my Basement (family room) into a nice theater.. I actually have 2 questions, hope you could help.

1st- I'm planning of buying Bipole speakers for my surrounds. I was originally going to use Bipoles from klipsch or Paradigm as both my surround sides and rears. However, I recently read that for the rear speakers, its better to use Monopole speakers and use bipole speakers as my sides.. Is this necessarily true? Will 2 Bipole speakers be too over whelming and will not give the surround effect?
Generally you want the bipoles for the side surrounds, and direct radiators for the rears. However, the bipole is a compromise on the dipole concept, which was intended to provide a sense of diffused surround while limiting the ability of the audience to localize the two surround speakers. Bipoles don't do that as well, they do provide a wide coverage area and a degree of diffusion while still providing a direct field that is localizable. This isn't all bad, especially for 5.1 music. Another compromise is the tripole idea. Any way you go, the idea is a big surround field without picking out where the speakers are. The rears contain effects that are meant to be localized, so there are more speaker options. The choice depends on how close to the LP the speakers are. Farther away, you can use direct radiators, closer you may want bipoles or tripoles.
2nd- I want to know how far apart can the rear speakers and side speakers be?

in my basement if I set up the 7.1 system how it's supposed to be ( with the sides being about 90 degrees to the listener) the rears would be about 6 feet apart.. Is that too close to each other that the two set of speakers will cancel each other and not create a good surround ? Or should I just do a 5.1 set up?
Hard to say without dimensions. Check the 7.1 speaker layout plans from Dolby, or THX. You'll see a radical difference. The THX placement works with THX processing, so if you don't have that, try to match the Dolby plan.
 
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It doesn't matter. This is one of the countless trivial factoids in home audio.
Yup. So trivial, the concept of dipole surrounds was patented by the inventor of THX to solve a specific problem.

Pat. # 5,043,970 and 5,222,059
 

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Yup. So trivial, the concept of dipole surrounds was patented by the inventor of THX to solve a specific problem.

Pat. # 5,043,970 and 5,222,059
One patents an invention to protect future earnings. What does that have to do with importance of dipole speakers in home audio? Tell me about this specific problem and why I have been lucky enough never to encounter it.
 

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One patents an invention to protect future earnings. What does that have to do with importance of dipole speakers in home audio? Tell me about this specific problem and why I have been lucky enough never to encounter it.
The problem was/is localization of surround speakers when the intended effect is a diffuse field, envelopment effect. Theaters get it with multiple surround speakers, at home two direct radiating surrounds won't do it, listeners easily pick out the location of the speaker. Hence, the dipole, null pointed at the LP. It's an effort to replicate the theater/dub stage presentation in the home. Might not matter to someone who doesn't care to replicate the theatrical experience.

The invention also included decorrelation of mono surround tracks. Correlated mono surround tracks would "cluster" about the nearest surround speaker. The decorrelation was a slight pitch bend, which spread the mono surround track around the room. Something we no longer have to worry about, since we don't have mono surround tracks any more, but wasn't a small deal in the 90's.

The actual "inventor" never got a dime of "future earnings" for any of it.
 

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The problem was/is localization of surround speakers when the intended effect is a diffuse field, envelopment effect. Theaters get it with multiple surround speakers, at home two direct radiating surrounds won't do it, listeners easily pick out the location of the speaker. Hence, the dipole, null pointed at the LP. It's an effort to replicate the theater/dub stage presentation in the home. Might not matter to someone who doesn't care to replicate the theatrical experience.

The invention also included decorrelation of mono surround tracks. Correlated mono surround tracks would "cluster" about the nearest surround speaker. The decorrelation was a slight pitch bend, which spread the mono surround track around the room. Something we no longer have to worry about, since we don't have mono surround tracks any more, but wasn't a small deal in the 90's.

The actual "inventor" never got a dime of "future earnings" for any of it.
Like I said, it is trivial. So is THX.
 

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PMJI....

... or THX. You'll see a radical difference. The THX placement works with THX processing, so if you don't have that, try to match the Dolby plan.
The THX diagrams for various content types indicate some differences in how the speakers should be aimed. THAT seems to be the "problem" they're addressing.

I remember some inordinately expensive little Cambridge Soundworks "THX certified surround speakers" that fired out both sides ... and for the old layout (?) in which surround left & right were slightly behind you (this is in Dolby Surround days, before DVD and DD 5.1 in the average home), I thought this was overkill. Not for a modern 7.1 arrangement, it seems.
 

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The problem was/is localization of surround speakers when the intended effect is a diffuse field, envelopment effect. Theaters get it with multiple surround speakers, at home two direct radiating ...



The invention also included decorrelation of mono surround tracks. Correlated mono surround tracks would "cluster" about the nearest surround speaker. The decorrelation was a slight pitch bend, which spread the mono surround track around the room. Something we no longer have to worry about, since we don't have mono surround tracks any more, but wasn't a small deal in the 90's.
.
Actually my old SEX, LIES, AND VIDEOTAPE dvd has 2.0 Surround, and 4.0 DD audio tracks. I like playing the 4.0 just to see what the mixer had in mind.

Aside:

People scoff and guffaw at my near-ludicrous surround arrangement (Bose 301 Series III speakers, aimed to the side and the back by using the 180º tweeters to bounce off the side walls), but ... it works. Surround effects come from an area behind and to the side of my sofa. Sure they bounce and sound a little echo-y, but it's acceptable with my limitations (would have to go wireless to put surrounds where Dolby and THX now recommend). IF someone said "Ooh, I'll have to try that" I'd emphatically discourage it.
 

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Hello, I am trying to build a 7.1 home theater. Nothing special, I'm just converting my Basement (family room) into a nice theater.. I actually have 2 questions, hope you could help.

1st- I'm planning of buying Bipole speakers for my surrounds. ...
2nd- I want to know how far apart can the rear speakers and side speakers be? ...
There's a nice and timely discussion found here. It's conclusion isn't surprising:
"...the room and the surround technology you’ve embraced will dictate what speakers you should use... you have to consider what is the most appropriate for your specific application. There is no “best” surround speaker, but there may be a best surround speaker for you."

For me, it depends on available space. Direct radiators are ideal if you have the room to sit far enough away. Bipoles might have advantages in long, thin theaters, but for my money, it's dipoles or direct in home theater. The reason is in the sound field.

Direct radiators can be thought of as having a hemispherical wavefront coming off the front baffle, in phase. Sound level is primarily determined by the direct sound, which falls off according to the inverse-square law - 2x distance is 1/4 as loud. So we have a very predictable sound field with intensity that varies strongly with distance to the ear.

Dipoles have a pair of those hemishperical wavefroms coming off each side. These wavefronts are out of phase, so they cancel on-axis - there is no sound in the specific direction they're aimed, but lots of sound to the sides. That means they will not follow the inverse square law as you move away from the on the auditory axis, because the sound you hear isn't coming directly from the speaker, but rather its reflections. That means you can place dipole surrounds a lot closer to the listening area, without inducing a lot of seat-to-seat variation in loudness.

BTW, my 7.1 system uses front wide locations, befitting a screen on the long wall, so I have lots of room for direct surrounds to integrate into the sound field. If you room's narrower, or there's no space to the sides, I'd consider a dipole in the surround location. Just plan for it... don't treat the nearby walls with acoustic absorbent, for example.

Have fun,
Frank
 
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