Should I use dipole surrounds with no near rear wall?

Discussion in 'Speakers' started by David Hoffman, Feb 17, 2004.

  1. David Hoffman

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    Will dipoles still work as they're supposed to (proper reflected sound) if my rear wall is non-existent? The rear of my family room simply opens up into walkspace and the kitchen, with the division between fam. room and kitchen being the peak of cathedral ceiling and a 7" thick beam running along the "seam"
    Here are family room dimensions:

    width: 15' 3"
    length: 13' 3"
    height: 7' 6" at front wall, rising to 8' 6" at the peak at boundary between fam rom and kitchen.

    I'm thinking of Paradigm ADPs mounted to my sidewalls above and ro right of listening positions.

    I'm worried that the dipole driver firing to the rear won't have anything nearby to reflect off of. Is it okay that the rear-directed sound would have to travel another 14 feet to reach the walls of the kitchen? Or rather are the dipoles reflecting off the of the side walls of my theater, which bounces the sound around to the listeners (and thus I'm okay)?
     
  2. Michael__M

    Michael__M Stunt Coordinator

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    I have a similar setup and would love to know the answer to this one. I am considering dipoles for my surrounds as well as I move up to 7.1 from 5.1. I will have direct rads for the rear. Will I get the dipole dispersion if I don't have a rear wall? My room open up as a loft over the lower level.
     
  3. David Hoffman

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    Since I still can't post URLs, I cannot send you to this similar thread I started on the AVS Forum (Speakers).

    I can, however, post what was said on it here...(In short, it convinced me to go with dipoles)...
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    DMF:
    You optimally want a side surround directly to the side of the listener, since that feeds only one ear making location difficult. Dipoles are used in large rooms with many listening positions because you can't depend on the "one ear" effect in those setups. If you're going to have several positions one behind the other, then dipoles might still be appropriate.

    (Dipoles cause a diffuse effect because they have two radiators operating out of phase with each other, one pointed forward, the other aft. This effects the sounds waves making it difficult to localize the source. Not sure I can explain how the effect works, except that the listener is getting direct radiation from both drivers, not primarily reflections. I think it makes the sound seem like a reflection even though it's not.)

    BTW, the side surround is placed 1 meter above the listeners ear, so it's not blasting right into the ear. That would be annoying. Also affects side-by-side listeners better.

    The Klipsch sides that I have are actually bipole/tripoles. There is a small woofer pointed at the listener (actually above his head). Lows are more difficult to localize. There are two mid/tweeter horns in phase pointing one 45' fore and one 45' aft. I guess this also makes the more easily localized highs ambiguous to the ear. Whatever, the effect is excellent.

    BTW, my room is about the same size as yours, although I actually have walls about 10' behind the listening position.
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    I (Eyleron) write:
    How important do you feel it is to match the surrounds to the fronts & center?

    If I'm going to be using all Paradigms up front, would it be outrageous to look for a bipole or a selectable bipole/dipole surround that's not a Paradigm?
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    DMF writes:
    It would be nice, but not that important. Most people can't afford in surrounds what they will pay for fronts, so there aren't many that have a match. I suppose it is possible to get a bad mismatch, but chances are you won't. It won't matter much for HT anyway.

    Others have reported that they only hear a difference in timbre when listening to music, but I rarely use the surrounds for music.
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    Tuskenraider writes:
    I didn't have an opinion about dipoles until I decided to demo some in my house for the exact reasons you mention and for the fact my DVD-A collection was going nowhere. Are they great for mulit-channel music? Not really, but they do OK. Strong localization is the one of the reasons I switched from Monitor 7's in the rear to ADP-370's. Since they were 3ft. from the listeners on the outside of seats, it could be very annoying. Dipoles aren't for everyone, but the do what they are intended to do great. For movies they are superior IMO because they disperse the sound enough to envelope you but you can still localize sounds, but they don't distract you like direct firing speakers may. If you could be 8ft. from the speakers, the direct firing may be better, but in our situation, we can't. I also don't think room is too small to use them. My room is about 13x20 and they work great. On one side the bac, wall is 2ft. from the speaker, on the other side it's about 7.
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    I write:
    Tusken, when you say you can still localize sounds...

    Does that mean when there is a gunshot that's supposed to occur behind and to the left, you can hear it as such with your dipoles?

    I worry that the recommendations for surround speaker types will change, as more movie soundtracks contain more discrete sounds and fewer ambiance-only effects (like, other than rain, thunder, crashing waves, insects twittering, etc.).

    But I suppose regardless of the above, I'm still stuck with my room dimensions and trying to support people who'll be too close to the speaker.
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    Fatbottom writes:
    You still get audio being reproduced from a dipole. It is neither distracting (ie like someone tapping on your shoulder) nor blurry. It's hard to explain. It's still part of the soundstage though.

    So when you get a action pan (ie Star Trek Borg fly-by's) there is still the ships zooming from back to front, front to back sides etc- but it's part of the whole movie experience. With monopoles it's like "Hello I'm a distracting speaker and playing back this bit-turn around" :-P

    Even reducing the gain [volume of the surrounds] ... to below calibration... has little effect (in my room) as it's still they're from a small point source.
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    I write:
    Interesting. Well, that does put some of my fears to rest.

    I just kept thinking about the DVE or THX audio tests where they produce vocals or test tones out of phase, and we hear the sound all around us. I worried that if the dipoles are out of phase thusly, I wouldn't be able to localize anything. But I s'pose with the dipole surrounds it's more a case of: "enveloping field to my right-ish and an enveloping field to my left-ish."

    So, what is the reasoning behind mono-pole surround back (centers)? Is that a stopgap recommendation by THX for while we don't have as much discrete surround back channel stuff? And thus that'll change when we have more true 7.1 discrete tracks in the future?
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    Fatbottom writes:
    Only the back facing treble/midrange is out of phase. The front facing treble/midrange is in phase. When you output the test tone it sound exactly like the front soundstage (not a mushy sound). But it fills the side walls up alot more than a monopole could ever do.
     
  4. David Hoffman

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    Also, I had my own conceptual problem where I was thinking of my family room as one carpeted "room"...and the tiled kitchen that was at the "back" of the family room a separate "room."

    This was incorrect thinking, though.

    In reality, for the purposes of sound propagation:
    It's one long, narrow room, with the home theater at the "front" of it (in what I call the family room). Naturally, there ARE walls, else I'd have snow drifts inside! So it's one room 15 feet wide and 28 feet long.

    Many people have theaters that use only that portion of the great room. I had nothing to fear.

    Also, the wide dispersion technique is mostly achieved, I think, through the dipole's out-of-phase drivers. If you play the DVE or THX test tones that are out of phase (like the front right and the center), you hear the sound envelope you. So it doesn't totally depend on the walls.
     
  5. Adam.More

    Adam.More Auditioning

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    Okay so dipoles work...what do you guys think about dipoles as rear and sides in a 7.1 setup?
     
  6. Dennis Gardner

    Dennis Gardner Stunt Coordinator

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    I used bipoles on the back wall when running my HT in 5.1 and found them to be great. During my upgrade to 7.1 I used them as dipoles to the side of my theater and use monopoles for the rears(now facing my sweet spot from the back corners). This was decided upon since using the monopoles on the sides left me really sensing where the sound was coming from (less than 6 feet away on the sides)and was distracting for me. I didn't have 2 sets of dipoles to use all around but I believe that each time this is brought up for discussion, it comes down to personal preference and how much multi-channel music listening is done on your 7.1 setup. Monopoles are preferred by many for music.

    Try different configs yourself if possible,

    DG
     

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