Unusual 7.1 speaker placement - AVS Forum
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post #1 of 15 Old 12-04-2011, 05:45 AM - Thread Starter
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I am arranging the speaker placement of my 7.1 system and have a couple of questions in regard of the placement of surround back speakers:

1) The manual of my Denon AVR-988 (mostly equivalent of AVR-2808CI spec-wise) recommends 60 degrees whereas Dolby recommends 135 to 150 degrees for the placement of rear surround speakers.

Since the difference seems not marginal, I would like to hear your take on this issue.

2) The distance between me and the rear surrounds is going to be too short because, due to the size of my TV, I can move forward my couch only up to 50 centimeters/20 inches, and generally only when watching content that does not fill the entire screen. When I move forward my couch as such, the gap between the couch and the wall barely accommodates my rear surround speakers.

According to the below article, “one requirement for 7.1-channel surround is sufficient space behind your couch and listening area—at least 5 feet or more. If your couch is jammed up against the rear wall or you have a comparatively small room of less than about 2,100 cu. ft. (length x width x height), the addition of two rear surround speakers will not likely add significant improvements in envelopment, especially if you are already using Axiom’s QS8 or QS4 “multi-polar” surround speakers.” I should note that although I do not have such space, my room is large and my speakers are direct radiating.

http://www.audioholics.com/education...surround-sound

Under these conditions, do you think that it would be better not to use rear surrounds at all?

If you don’t think so, or assuming that I would want to rear surrounds nonetheless, would your answer to the first question be changed?

In all 7.1 diagrams I have seen so far, the rear surrounds are placed behind the most left and right of a 3 to 4 seater-couch. Perhaps I can place them not behind my sofa in a way that my side surrounds and rear surrounds are aligned??

3) If I lean my sofa against the wall, then would it be extremely implausible to use 7.1 where the angle between me and the rear surrounds would be 90 and the side surrounds will be a tad in front of and facing towards me?

Thank you!

PS. I will use all speakers at ear level.
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post #2 of 15 Old 12-04-2011, 07:25 AM
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Quote:
Originally Posted by MG428 View Post

I am arranging the speaker placement of my 7.1 system and have a couple of questions in regard of the placement of surround back speakers:

1) The manual of my Denon AVR-988 (mostly equivalent of AVR-2808CI spec-wise) recommends 60 degrees whereas Dolby recommends 135 to 150 degrees for the placement of rear surround speakers.

Since the difference seems not marginal, I would like to hear your take on this issue.

2) The distance between me and the rear surrounds is going to be too short because, due to the size of my TV, I can move forward my couch only up to 50 centimeters/20 inches, and generally only when watching content that does not fill the entire screen. When I move forward my couch as such, the gap between the couch and the wall barely accommodates my rear surround speakers.

According to the below article, one requirement for 7.1-channel surround is sufficient space behind your couch and listening areaat least 5 feet or more. If your couch is jammed up against the rear wall or you have a comparatively small room of less than about 2,100 cu. ft. (length x width x height), the addition of two rear surround speakers will not likely add significant improvements in envelopment, especially if you are already using Axiom's QS8 or QS4 multi-polar surround speakers. I should note that although I do not have such space, my room is large and my speakers are direct radiating.

http://www.audioholics.com/education...surround-sound

Under these conditions, do you think that it would be better not to use rear surrounds at all?

If you don't think so, or assuming that I would want to rear surrounds nonetheless, would your answer to the first question be changed?

In all 7.1 diagrams I have seen so far, the rear surrounds are placed behind the most left and right of a 3 to 4 seater-couch. Perhaps I can place them not behind my sofa in a way that my side surrounds and rear surrounds are aligned??

3) If I lean my sofa against the wall, then would it be extremely implausible to use 7.1 where the angle between me and the rear surrounds would be 90 and the side surrounds will be a tad in front of and facing towards me?

Thank you!

PS. I will use all speakers at ear level.



If the side surrounds are at 90 degrees, placing the rear surrounds at 150 degrees is 60 degrees further back than the side surrounds. Perhaps this is what Denon means in the bolded reference above? I checked the manual for the 2808 and the speaker layout diagram for 7.1 is exactly like the above diagram, with the seating well forward of the back wall, the speakers separated from the seating by an adequate distance, as well as the speakers at ~150 degrees. (See Page 9 of the manual, which can be downloaded at the Denon website.)

I agree with the audioholics article that, if you can't get the rear surrounds in the recommended positions, they aren't worth doing. Stick with 5.1, or consider using the 6th and 7th speakers in the Wides or Heights positions. Of course, the later would require a receiver update, but that would be the only way to use more than 5 speakers in your system.

On a final note, it is definitely not recommended to place the side surrounds "forward" of the seating. 90 to 110 degrees is the recommended placement for the side surrounds.

Craig
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post #3 of 15 Old 12-04-2011, 07:46 AM
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Nothing weird. I guess you are talking about the audyssey dsx 7.1 placement:

Audyssey 7.1 Wides and Heights



Denon avrs have both Dolby and Audyssey surround systems, in case you don't know. The audyssey 7.1 wides configuration claims to widen the front soundstage compared to the Dolby 7.1 system, which focuses on the back soundstage that is less important to the human perception
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post #4 of 15 Old 12-04-2011, 08:10 AM
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Originally Posted by tigerstripe View Post

Nothing weird. I guess you are talking about the audyssey dsx 7.1 placement:

Denon avrs have both Dolby and Audyssey surround systems, in case you don't know.

His current Denon AVR doesn't have Audyssey DSX or Dolby Heights. He would need a new receiver to get those technologies.

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Originally Posted by tigerstripe View Post

The audyssey 7.1 wides configuration claims to widen the front soundstage compared to the Dolby 7.1 system, which focuses on the back soundstage that is less important to the human perception

Dolby also has Dolby PLIIz Heights, but the Height speaker placement is different than the Audyssey DSX Height speaker placement:



The PLIIz Heights are directly above the L/R mains, and in the same vertical plane.

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post #5 of 15 Old 12-04-2011, 08:32 AM - Thread Starter
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Originally Posted by tigerstripe View Post

Nothing weird. I guess you are talking about the audyssey dsx 7.1 placement

No I did not. I am sorry if I mis-described. Thank you for your comments anyway.
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post #6 of 15 Old 12-04-2011, 08:35 AM - Thread Starter
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Originally Posted by craig john View Post

I agree with the audioholics article that, if you can't get the rear surrounds in the recommended positions, they aren't worth doing. Stick with 5.1, or consider using the 6th and 7th speakers in the Wides or Heights positions. Of course, the later would require a receiver update, but that would be the only way to use more than 5 speakers in your system.

On a final note, it is definitely not recommended to place the side surrounds "forward" of the seating. 90 to 110 degrees is the recommended placement for the side surrounds.

Craig


Thank you, Craig.

If I insist on using surround back speakers (perhaps only when I move my couch forward and may be limited to 6.1 or 7.1 encoded titles), where would you recommend me to place the speakers in the attached diagram, considering that the gap between the wall and the couch will only be 50 centimeters/20 inches? To the red, blue or yellow box?

Although I placed the boxes to the left side of the diagram, please assume that I will apply the same to the right side for the right back speaker.

I should note that the distance between the center of my sofa and the left surround side and rear speakers can be at most 215 cm/85 inches, whereas I can extend the distance for right surround side and rear speakers as much as I can, though, I believe I should not do that in order not to lose equidistance.
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post #7 of 15 Old 12-04-2011, 08:52 AM
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Originally Posted by MG428 View Post

Thank you, Craig.

If I insist on using surround back speakers (perhaps only when I move my couch forward and may be limited to 6.1 or 7.1 encoded titles), where would you recommend me to place the speakers in the attached diagram, considering that the gap between the wall and the couch will only be 50 centimeters/20 inches? To the red, blue or yellow box?

Although I placed the boxes to the left side of the diagram, please assume that I will apply the same to the right side for the right back speaker.

I should note that the distance between the center of my sofa and the left surround side and rear speakers can be at most 215 cm/85 inches, whereas I can extend the distance for right surround side and rear speakers as much as I can, though, I believe I should not do that in order not to lose equidistance.



One of the features of 7.1 systems with rear surrounds is the ability to "phantom image" sounds between the sides and the rears. With the red position, that effect will be essentially lost. The yellow position places the rears very close to the listeners ears. They will be overwhelming and highly localizable, (and very distracting) in the yellow positions. The blue positions would be the "least worst" by default, but I would probably forgo them if they are only 20" behind the listening position.

Edit: What speakers are you thinking of using in these positions? That will also make a difference.

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post #8 of 15 Old 12-04-2011, 08:57 AM - Thread Starter
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Originally Posted by craig john View Post

One of the features of 7.1 systems with rear surrounds is the ability to "phantom image" sounds between the sides and the rears. With the red position, that effect will be essentially lost. The yellow position places the rears very close to the listeners ears. They will be overwhelming and highly localizable, (and very distracting) in the yellow positions. The blue positions would be the "least worst" by default, but I would probably forgo them if they are only 20" behind the listening position.

That sounds reasonable.

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Originally Posted by craig john View Post

Edit: What speakers are you thinking of using in these positions? That will also make a difference.

I will use Aperion 5B bookshelf speakers. They are not bipole/dipole. All of my speakers are 5B, except the center is 5C.
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post #9 of 15 Old 12-04-2011, 09:11 AM
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I will use Aperion 5B bookshelf speakers. They are not bipole/dipole. All of my speakers are 5B, except the center is 5C.

With monopoles in the surround positions, I would suggest aiming them at the primary listening position.

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post #10 of 15 Old 12-04-2011, 09:21 AM - Thread Starter
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Originally Posted by craig john View Post

With monopoles in the surround positions, I would suggest aiming them at the primary listening position.

Craig

In any case they will all be aimed at the primary listening position and at ear level as they stand on the same speaker stand with the exact same height.

I believe you meant you would use the yellow box in terms of the placement of the rear surround speakers and aim it to the primary listening position, right?

Also, would you place the rear surrounds to the yellow box if they were bipole/dipole? I guess you would place them differently as you asked the type of my speakers. The reason why I am asking this question is because I can use a friend's speakers if they would serve under my room's layout.
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post #11 of 15 Old 12-04-2011, 09:29 AM
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Originally Posted by MG428 View Post

I believe you meant you would use the yellow box in terms of the placement of the rear surround speakers and aim it to the primary listening position, right?

No, I said the blue positions would be the "least worst". None of those positions are "good" if they are so close to the listeners ears. The blue positions would allow some phantom imaging while the yellows would be way too close. If you absolutely *must* have rear surrounds, then place them at the blue positions, aim them at the primary LP and be sure you calibrate them properly.

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post #12 of 15 Old 12-04-2011, 09:40 AM - Thread Starter
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Originally Posted by craig john View Post

No, I said the blue positions would be the "least worst". None of those positions are "good" if they are so close to the listeners ears. The blue positions would allow some phantom imaging while the yellows would be way too close. If you absolutely *must* have rear surrounds, then place them at the blue positions, aim them at the primary LP and be sure you calibrate them properly.

Craig

Sorry. I meant blue. Thank you.

Would dipole/bipole speakers further worsen the situation? Or would they be better than monopoles in my "least worst" condition?
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post #13 of 15 Old 12-04-2011, 09:52 AM
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Sorry. I meant blue. Thank you.

Would dipole/bipole speakers further worsen the situation? Or would they be better than monopoles in my "least worst" condition?

Dipole surrounds are designed with a "null" that is supposed to be aimed at the listening position. This makes them less localizable and if you can aim them properly, they could be beneficial, at least at the primary LP. At other positions, they won't have the null aimed properly and they would be just as detrimental as monopoles.

Bipoles don't have a null, but they have a wider dispersion pattern. They would be just as localizable as monopoles, but they would provide better coverage to more seats.

Seriously, if you have the extra monopoles, and you really want to use them, I suggest you consider getting a receiver with DSX/PLIIz. That would be a much better use than trying to shoehorn a set of speakers where they don't really work.

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post #14 of 15 Old 12-04-2011, 10:42 AM - Thread Starter
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OK so for the time being I will use my monopoles in a 7.1 setup only for 6.1 encoded Star Wars and LOTR EE blu-rays as they contain discrete sound for surround back channel and their aspect ratio allows for me to move my couch forward. Then I will put them to their packages for future use.

I may use them in future as surround back speakers in a permanent 7.1 setup if I move to a room where there would be sufficient space between my couch and wall. Or I can follow your suggestion of upgrading to PLIIz, including buying 2 more speakers for 9.1 system, depending on which room I will use them. Currently we have two living rooms, one is small and cosy, with L-shaped couch and a 42 inch TV. My surround sound system and my 52 inch TV is located in our bigger living room where we, for instance, host a dinner for friends&family/guests. It would not be proper to hang speakers on wall especially at that height.
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post #15 of 15 Old 12-04-2011, 01:50 PM
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Quote:
Originally Posted by MG428 View Post

Under these conditions, do you think that it would be better not to use rear surrounds at all?

Yes, you will have no meaningful separation between your side and rear speakers. Better to stick with a proper 5.1 set-up than shoe-horning a poor 7.1 layout when you have no room behind you for the rear speakers.

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