I am about to add monopoles to the rear of my theater for use only with DVD-A/SACD. My room is such that I cannot get both speakers at the ITU-recommended 120°. And the room is also built with a setback at the entryway that could place the left rear speaker a few feet further from the "sweet spot" than the other rear speaker when they are at ~135°. If I increase the angle I can get them equidistant and equiangular - at about 145°.

Should I go for the "smallest" angle and handle the different distances in the speaker setup, or mount them equidistant, but further from the recommended 120°? I'm thinking that the sound of the speakers might be a bit different - timbre? - with different distances.

I think you'd have to try it and see. But I'd rate angular symmetry as most important, then a trade-off between distance symmetry and angle. Presumably your player/receiver can attempt to correct for different distances.

I think you'd have to try it and see. But I'd rate angular symmetry as most important, then a trade-off between distance symmetry and angle. Presumably your player/receiver can attempt to correct for different distances.
"Trying it" would involve drilling holes through the plaster walls into studs. I think I will go the priority being getting them as close as possible to 120 degrees and deal with the distance difference with the Denon 3910's analog out speaker setup. I was concerned about a possible timbre difference with the speaker being at a different distance.

Hi Jeff,

Do you have a reference for the "ITU-recommended 120°"? I've never seen this recommendation. Dolby recommends 135° to 150° for the back speakers. 120° seems pretty extreme, especially if you mount them facing directly forward. This would place the LP at 60° off-axis of the tweeter. Also, it would place them very close to the side speakers.
I'm thinking that the sound of the speakers might be a bit different - timbre? - with different distances
Unless you're using bipole speakers with broad dispersion patterns, I think you'll get more timber mis-match if the angles are different than the distances. You can account for the distance mis-match in your pre/pro. Being at different angles would place you at different positions to the monopoles' dispersion patterns. IMO, you would be better off with the 145°, equidistant, *equi-angular* placement, as this would put you at the same "off-axis" placement for each speaker, at least at the "sweet spot". OTOH, you could toe them in to account for the angular difference.

Sanjay Durani has a formula for back speaker separation. He recommends you take the distance to the back wall and multiply times 1.2. This is the distance the speakers should be separated. It also puts them close to 135°.

BTW, how are you planning to wire this? Since you already have your back speakers connected in the THX ASA arrangement, will these be an additional set of back speakers that will be switched when listening to DVD-A or SACD?

Let me know if you want some help with the installation. Maybe we could rig up some kind of tempoary arrangement to try different locations before the holes get drilled. :)

Craig

Hi Jeff,

Do you have a reference for the "ITU-recommended 120°"? I've never seen this recommendation. Dolby recommends 135° to 150° for the back speakers. 120° seems pretty extreme, especially if you mount them facing directly forward. This would place the LP at 60° off-axis of the tweeter. Also, it would place them very close to the side speakers.

Unless you're using bipole speakers with broad dispersion patterns, I think you'll get more timber mis-match if the angles are different than the distances. You can account for the distance mis-match in your pre/pro. Being at different angles would place you at different positions to the monopoles' dispersion patterns. IMO, you would be better off with the 145°, equidistant, *equi-angular* placement, as this would put you at the same "off-axis" placement for each speaker, at least at the "sweet spot". OTOH, you could toe them in to account for the angular difference.

Sanjay Durani has a formula for back speaker separation. He recommends you take the distance to the back wall and multiply times 1.2. This is the distance the speakers should be separated. It also puts them close to 135°.

BTW, how are you planning to wire this? Since you already have your back speakers connected in the THX ASA arrangement, will these be an additional set of back speakers that will be switched when listening to DVD-A or SACD?

Let me know if you want some help with the installation. Maybe we could rig up some kind of tempoary arrangement to try different locations before the holes get drilled. :)

CraigHi Craig,

In finding the the link you requested (http://www.soundstage.com/surrounded/surrounded200307.htm), I see that it is actually 110°. The ITU recommendation is for multi-channel music with five identical monopoles aimed directly at the "listener" (and the .1 subwoofer channel), whereas the layout recommended by Dolby (and THX) is for movie soundtracks. THX's ASA scheme - side dipole surrounds and rear monopoles WITHIN inches of each other (like my configuration) - is their attempt to have ONE layout for both music and movies.

While the multi-channel music - DSOTM - that we listened to on your system recently had the quality and impact you'd expect from such a system, I've grown accustomed to the five identical monopoles in my TL and the (more or less) pinpoint imaging that they provide. (That's the only thing I like about them over your HT system, but it is enough to make me want the quality and impact of your system with the directionality and timbre-match of the TL.) My 7.1 THX Ultra2 ASA system, while doing a somewhat better job with MC music than a dipole-surround 5.1 system, is still lacking the directionality and clarity of my TL. With MC music, the artist/engineer/producer is likely to place much more than background vocals in the surrounds and a trumpet solo reproduced by a dipole just doesn't cut it.

So I will mount the "extra" pair of M&K S-150s that I have in the rear as far apart as possible and manually swap speaker connections at the wall plates with the rear surrounds when I want to listen to 5.1 DVD-A or SACD sources. When I connect my Denon 3910's 6-channel analog outs I will be sure that the two rear channels go to the pre/pro's rear surround channels (instead of side surrounds). Since the pre/pro will be essentially "out of the loop", no ASA processing will occur. If the rear channels coming from the 135° angle is not pleasing, I could try the monopoles next to my side surrounds, but that would be 90° and no longer "rear." I'm betting that 25° too far to the rear will be more satisfying than 10° too shallow.

Anyway, I think I'm on the right track and that once I've listened to DVD-A's the way they were mixed the inconvenience of swapping speaker connections will be trivial.

Jeff

P.S. Thanks for the offer of assistance, but I've got spackle and paint if the rear location turns out to be wrong. :eek: I'll post my results (and email you with an invitation to have a listen}.

Anyway, I think I'm on the right track and that once I've listened to DVD-A's the way they were mixed the inconvenience of swapping speaker connections will be trivial.

After setting my media room up for HiRez surround, I never bothered moving my rear surrounds back to the 'movie' location for flicks.. it works fine.

After setting my media room up for HiRez surround, I never bothered moving my rear surrounds back to the 'movie' location for flicks.. it works fine.
I'm still wedded to the THX Ultra2 ASA layout for movies and am fortunate enough to be able to have dual speaker layouts. Of course, unfortunately, it results in a rear wall that is festooned with speakers. :o

But your experience suggests I'm on the right track.

Hi Jeff,

Do you have a reference for the "ITU-recommended 120°"? I've never seen this recommendation. Dolby recommends 135° to 150° for the back speakers. 120° seems pretty extreme, especially if you mount them facing directly forward. This would place the LP at 60° off-axis of the tweeter.



The ITU recommends all speakers be identical monopoles , same height (ear level), and firing directly at the listening position, so off-axis is not an issue. This is pretty such my setup, though mine are 'small' stand-mounted NHT SuperOnes + a 12" subwoofer, rather than the recommended full-range speakers all around.

I've found that as long as the surrounds are aimed at the LP, the angle can be from ~110° - 160° and still sound quite good, and distances can be compensated in the AVR (though I tend to keep mine all at ~9ft from the LP 'because I can', and at ~145° due to room constraints). With the ITU setup movie surround fx are probably more 'localized' than intended, but I give music playback priority and movies seem to sound pretty good too.

With the ITU setup movie surround fx are probably more 'localized' than intended, but I give music playback priority and movies seem to sound pretty good too.
That was/is the whole point of dipoles for the surrounds on movies. I forget who the "designer" was (Tomlinson Holman?), but the thinking was to NOT pull the audience's attention off the screen. A bullet flying off screen and going somewhere over your left shoulder and hitting something is OK, but a bullet on a trajectory four feet from your head over your left shoulder and striking a metallic object precisely six feet behind you tends to distract from the screen.

edit: I caught your edit and understand.

Hi Craig,

In finding the the link you requested (http://www.soundstage.com/surrounded/surrounded200307.htm), I see that it is actually 110°. The ITU recommendation is for multi-channel music with five identical monopoles aimed directly at the "listener" (and the .1 subwoofer channel), whereas the layout recommended by Dolby (and THX) is for movie soundtracks. THX's ASA scheme - side dipole surrounds and rear monopoles WITHIN inches of each other (like my configuration) - is their attempt to have ONE layout for both music and movies.
Ahhhh.... I see. I thought you were adding two *rear* channels for 7.1. If you're going 5.1, then, yes, 110° is correct. In fact Dolby recommends 90° to 110° for the side surrounds as well. The 135° to 150° was for the rear channels in a 7.1 system.
http://www.dolby.com/consumer/home_entertainment/roomlayout.html

While the multi-channel music - DSOTM - that we listened to on your system recently had the quality and impact you'd expect from such a system, I've grown accustomed to the five identical monopoles in my TL and the (more or less) pinpoint imaging that they provide. (That's the only thing I like about them over your HT system, but it is enough to make me want the quality and impact of your system with the directionality and timbre-match of the TL.) My 7.1 THX Ultra2 ASA system, while doing a somewhat better job with MC music than a dipole-surround 5.1 system, is still lacking the directionality and clarity of my TL. With MC music, the artist/engineer/producer is likely to place much more than background vocals in the surrounds and a trumpet solo reproduced by a dipole just doesn't cut it.
Just FYI, my surrounds are bipoles, not dipoles. They have 90° offset horns with wide dispersion patterns. They cover a wide range, as opposed to dipoles, where the listener sits in the null. Klipsch has a good explanation their website:
Klipsch Wide Dispersion Surround Technology™ (WDST). The Tractrix Horns deliver a 90-degree wide by 60-degree high dispersion pattern. By aligning two horns at 90-degrees with respect to each other, WDST smoothly covers a 180-degree horizontal arc. In other words, the surround sound is pointed at you no matter where you are seated.

So I will mount the "extra" pair of M&K S-150s that I have in the rear as far apart as possible and manually swap speaker connections at the wall plates with the rear surrounds when I want to listen to 5.1 DVD-A or SACD sources. When I connect my Denon 3910's 6-channel analog outs I will be sure that the two rear channels go to the pre/pro's rear surround channels (instead of side surrounds). Since the pre/pro will be essentially "out of the loop", no ASA processing will occur. If the rear channels coming from the 135° angle is not pleasing, I could try the monopoles next to my side surrounds, but that would be 90° and no longer "rear." I'm betting that 25° too far to the rear will be more satisfying than 10° too shallow.
Agreed. Will you "aim" them at the LP?

P.S. Thanks for the offer of assistance, but I've got spackle and paint if the rear location turns out to be wrong. :eek: I'll post my results (and email you with an invitation to have a listen}.
I need to get you back over to my house too. I have a new sub for you to hear.

Craig

Jeff,

If you are going to do a 5-speaker set-up for multi-channel music listening, then I would place the surround speakers by ear rather than use some prescribed angles. With your current set-up you have separate pairs of speakers providing coverage at your sides and coverage behind you. With only one pair of surrounds, you have to find a location that provides a decent compromise between side and rear imaging.

I would start by placing the (monopole) surrounds on temporary stands (use speaker stands, step-ladders, stacks of boxes, whatever). Start with the surrounds along the side walls, slightly behind you. Play mono content through both speakers and keep moving the speakers rearward until you get a phantom image behind you. Then play something with strong stereo content and adjust the speakers forward until you hear good left-vs-right stereo separation along your sides. Somewhere in there will be the best compromise between side and rear imaging. At that point you can nail them to the wall (so to speak).

Even with a 5.1-speaker set-up, you still should get left-vs-right-vs-rear imaging in the surround field. The only way I've found to guarantee these results, considering that each of us has slightly different hearing, is to experiment with placement and listen.

Sanjay

Ahhhh.... I see. I thought you were adding two *rear* channels for 7.1. If you're going 5.1, then, yes, 110° is correct. In fact Dolby recommends 90° to 110° for the side surrounds as well. The 135° to 150° was for the rear channels in a 7.1 system.
Got the 7.1 monopole rears at 180° 2" apart as per THX Ultra2 ASA. Side dipole surrounds are at 90°. They are M&K SS-150 and are switchable - monopole, dipole, bipole, tripole and a few things in between - but are NOT identical to the LCRs, which is the ideal for hi-rez multi-channel music. I've got no more room at the 90° locations - the entryway setback interferes on the rear left - so I need to got to the back wall with the dedicated DVD-A/SACD rears.

Will you "aim" them at the LP?
Yep, with my handy dandy laser alignment tool!

I need to get you back over to my house too. I have a new sub for you to hear.
Certainly! Something from Dr Joseph?

Certainly! Something from Dr Joseph?
No, something from JL Audio, (F112). I've been playing around with the Velo EQ and JL's internal "Acoustic Room Optimization". Pretty interesting stuff. The JL's ARO does just as good a job with 1-band of parametric EQ as the Velo with 8:
http://www.avsforum.com/avs-vb/showthread.php?t=809299

Back on topic, if you want to try Sanjay's suggestions, I'll re-extend the offer and say I'll be happy to help.

Craig

Jeff,

If you are going to do a 5-speaker set-up for multi-channel music listening, then I would place the surround speakers by ear rather than use some prescribed angles. With your current set-up you have separate pairs of speakers providing coverage at your sides and coverage behind you. With only one pair of surrounds, you have to find a location that provides a decent compromise between side and rear imaging.

I would start by placing the (monopole) surrounds on temporary stands (use speaker stands, step-ladders, stacks of boxes, whatever). Start with the surrounds along the side walls, slightly behind you. Play mono content through both speakers and keep moving the speakers rearward until you get a phantom image behind you. Then play something with strong stereo content and adjust the speakers forward until you hear good left-vs-right stereo separation along your sides. Somewhere in there will be the best compromise between side and rear imaging. At that point you can nail them to the wall (so to speak).

Even with a 5.1-speaker set-up, you still should get left-vs-right-vs-rear imaging in the surround field. The only way I've found to guarantee these results, considering that each of us has slightly different hearing, is to experiment with placement and listen.
Thanks, Sanjay. I am restricted as to where I can mount the rear left speaker. I suppose I could use a beefy stand and move the speaker in and out of its ideal location, but I envision someone going to the WC knocking it over. With ITU recommending 110°, I can't imagine any rear phantom image being supported or, for that matter, phantom side images (between, say, front left and rear left). Am I mistaken on this?

Anyway, the realities of my room are going to be the determining factor in locating these rear "mains." Even so, I imagine it will be worlds better than using either set of my "movie" surrounds for hi-rez MC music.

I suppose I could use a beefy stand and move the speaker in and out of its ideal location, but I envision someone going to the WC knocking it over.The surrounds don't have to end up in the ideal location. I would first find the ideal spot for reference. This way, when you deviate from it due to logistics, you have an understanding of what's being compromised. Who knows, your final locations may not be as far off as you think. But you'll never know unless you start from some reference point. With ITU recommending 110°, I can't imagine any rear phantom image being supported or, for that matter, phantom side images (between, say, front left and rear left). Am I mistaken on this?No, you're correct. However, I use those recommendations as a starting point and tweak by ear. I don't like having a sonic hole behind me in the surround field, since some multi-channel music does take advantage of rear imaging that is distinct from sounds along the sides. I imagine it will be worlds better than using either set of my "movie" surrounds for hi-rez MC music.What if you used both sets to get virtual surrounds between them? Before reflexively dismissing the idea, try an experiment. Make sure your side speakers aren't configured as dipoles.

Use some good multi-channel music ('DSotM', Beatles 'Love' DVD-A, etc), choose the DD or DTS track, select PLIIx Music mode, and take a listen. It won't have the resolution of the MLP track, but it is the same mix. Listen to the surround imaging. Does it sound like separate speakers at your sides and behind you? Or is the surround field a continuous arc? IF you get the latter, do you think using only two surround speakers will be an improvement?

Sanjay

Before reflexively dismissing the idea, try an experiment. Make sure your side speakers aren't configured as dipoles. Use some good multi-channel music ('DSotM', Beatles 'Love' DVD-A, etc), choose the DD or DTS track, select PLIIx Music mode, and take a listen. It won't have the resolution of the MLP track, but it is the same mix. Listen to the surround imaging. Does it sound like separate speakers at your sides and behind you? Or is the surround field a continuous arc? IF you get the latter, do you think using only two surround speakers will be an improvement?
I would be able to easily configure my system to use any of my existing pairs of surrounds for the hi-rez DVD-A tracks simply by plugging the analog outs for the rear channels into the appropriate analog inputs on the pre/pro. It would be easy to set it up and alternate between the 90° SS-150s (as monopoles) and the 135° S-150s, though there's be recalibration time as they'd need different speaker distance and level settings. Is that what you meant?

I think Sanjay is saying to temporarily ignore the DVD-A track, (which is 5.1) and use the DD or DTS tracks. Use your existing surround setup exactly as you have it but employ PLIIx processing. This will extract the 7.1 from the discrete mix, giving you "virtual surrounds" located between your existing side speakers and your rear speakers. His sugestion is to see if that isn't just as convincing a surround setup as the potential DVD-A 5.1 system, without all the inconvenience, (but minus the high resolution of the DVD-A/SACD formats).

Actually, it would be interesting to try this with DSotM and compare the actual 4.1 discrete DTS/DD track to the processed 7.1 PLIIx version. The processing extracts the center channel from the L/R's and the rear surrounds from the R & L SS channels. It will be interesting to see how much differently they image. Will the PLIIx extracted "hard" center be a more realistic image than the "phantom" center created by the L/R's in the 4.1 mix? How much differently will the SS/RS PLIIx "processed" channels image than the "hard" SS channels in the 4.1 system? It will be a good test of "discrete" 4.1 vs. "processed" 7.1.

Craig

I think Sanjay is saying to temporarily ignore the DVD-A track, (which is 5.1) and use the DD or DTS tracks. Use your existing surround setup exactly as you have it but employ PLIIx processing. This will extract the 7.1 from the discrete mix, giving you "virtual surrounds" located between your existing side speakers and your rear speakers. His sugestion is to see if that isn't just as convincing a surround setup as the potential DVD-A 5.1 system, without all the inconvenience, (but minus the high resolution of the DVD-A/SACD formats).

Actually, it would be interesting to try this with DSotM and compare the actual 4.1 discrete DTS/DD track to the processed 7.1 PLIIx version. The processing extracts the center channel from the L/R's and the rear surrounds from the R & L SS channels. It will be interesting to see how much differently they image. Will the PLIIx extracted "hard" center be a more realistic image than the "phantom" center created by the L/R's in the 4.1 mix? How much differently will the SS/RS PLIIx "processed" channels image than the "hard" SS channels in the 4.1 system? It will be a good test of "discrete" 4.1 vs. "processed" 7.1.
I'd be up for setting up a listening test like you describe with, maybe, even another member or two. Extra ears/brains to say what they hear and what they prefer. The five identical monopoles will be available for audition as well. I am inclined to opine that being faithful to the original mix at a high bit rate will smoke any processed and compressed version of the mix. :)

I think Sanjay is saying to temporarily ignore the DVD-A track, (which is 5.1) and use the DD or DTS tracks. Use your existing surround setup exactly as you have it but employ PLIIx processing.Exactly. Or, if you want to hear the hi-rez track, use Y-splitters on the surround outputs of the player and send each surround channel to its respective side and rear speaker. The processing extracts the center channel from the L/R's and the rear surrounds from the R & L SS channels.It will extract surround-back info (in stereo, no less) from the surround channels, but PLIIx doesn't touch the critical front soundstage of discrete multi-channel sources.

Remember that PLIIx always processes only 2 channels, irrespective of the number of channels in the source material. When fed stereo content, the circuit sees 2 main channels and selects processing that will steer that information over 6 or 7 speakers. When fed 5.1 or 6.1 material, the circuit sees only 2 surround channels and selects processing that will steer that information over 3 or 4 speakers. Of course, those are two very different processes. How much differently will the SS/RS PLIIx "processed" channels image than the "hard" SS channels in the 4.1 system?I've had pretty good luck playing discrete multi-channel on a 7.1-speaker system using LOGIC7 processing. I don't hear many sounds image directly to my sides, even though that's where my side speakers are. Instead, those speakers tend to expand the front soundstage beyond my front L/R speakers. Surround imaging often localizes along the sides, but clearly rearward of where the side speakers are. Keep in mind that all four of my surrounds are monopoles. Personally, I haven't felt the need to go back to using a single pair of surrounds. Worth experimenting with before adding another set of surrounds specifically for music.

Sanjay

Personally, I haven't felt the need to go back to using a single pair of surrounds. Worth experimenting with before adding another set of surrounds specifically for music.
I want five identical monopoles for reproducing hi-res audio. :)