Thinking about surround speaker types and placement

Discussion in 'Speakers' started by Kevin C Brown, Sep 13, 2003.

  1. Kevin C Brown

    Kevin C Brown Producer

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    Some smart people here, so I want to bounce this off y'all...

    The general consensus seems to be 2 - 3 ft above ear level. And then for 7,1, I've seen either 90 deg from the front (directly to the sides) as well as slightly forward or slightly rear of the listening position. A lot of people like dipoles, but then there are direct radiators and bipoles, omnis too.

    But then some people suggest about 12" above ear level. So I tried that: direct radiators, about 12" above ear level, and I've tried them directly to the side, and slightly behind the listening position. Directly to the side is no good. Waaaay too localizable. Great for multichannel music, but not so good with some elements of some soundtracks. Slightly to the rear (maybe 110 deg) doesn't really improve things much.

    So I have some of the Mirage Omni 50's there now, and a much better effect.

    But the gist of my question is this: if I did choose to use direct radiators 2 - 3 ft above ear level, then I'm mainly getting off-axis sound, which is poor quality in terms of flat freq response. (The largest problem is rolled off highs.) So now I put 2 and 2 and 2 together, and I think I come to the conclusion that: 1) this is why the original spec of DPL rolled off the highs at 7k Hz, and 2) why in a lot of Logic 7 modes specifically, the highs are rolled off. But not enough in my case.

    So I presume that rolling of the highs helps the prevent the ear and the brain in terms of localization. Dipoles rely on the same effect: off-axis sound. But the freq response sucks. (Ever see measurements of a dipole speaker? Bad.)

    So can't I have it all? Non-localizable sound with relatively good (i.e., flat) freq response? Just curious as to your thoughts...

    The Mirage Omnis seem to fit the bill (or maybe any bipolar speaker too), but I think I'd want to mate them with Vandersteens up front, so you see my dilemna. (Mix and match.) I am trying Mirages up front now, but to exaggerate the difference between the Vandersteens up front, which have incredible imaging, but a small sweet spot, with the Mirages, which have a much larger spaciousness and bigger sweet spot, is that the Mirages up front sound like I'm listening to the material down a tunnel. Kind of detached and un-involving (but I'm still working on placement too). Anyways!
     
  2. Wayne A. Pflughaupt

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    Kevin,

    Have you tried direct radiators behind, a few feet above and aimed at the listening position? This is my preference.

    I’m with you – I don’t like side positioning. To me a fly-over doesn’t “get it” unless it ends up behind you. It’s not a “fly over” if it stops at your sides – know what I mean? [​IMG] Same with other effects – voices echoing in a large room, for instance. The reverb comes from all around if you are in the same room. With side-mounted speakers, it sounds like you’re standing all the way at one end of the room with your back against the wall.

    The thing with direct radiators is they can’t be too close. Perhaps that’s what’s happening in your room. Good direct radiators for home theater should be a wide-dispersion design, and they should probably be at least 8 ft. away.

    If that’s not possible, then equalization can work, if it’s done correctly. As you have already noted, off-axis speakers have reduced high frequency response compared to on-axis. So the trick is to place them off-axis where they sound right, then take off-axis response measurements. Then set on-axis equalization to mimic off-axis response.

    Regards,
    Wayne A. Pflughaupt
     
  3. Kevin C Brown

    Kevin C Brown Producer

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    Wayne- I think you hit the nail on the head. I think I have come to the following conclusions:

    1) Bipolars & Omnipolars possibly will work at smaller distances above the ear and you still get flat freq reponse.

    2) Direct radiators will work, but they have to be 2 - 3 ft above, but for flat freq response, see if they can pointed at the listening area. Another way, is that if they can't be that much above ear level, to point them away from ear level (but that does affect freq reponse), or offset them laterally from the ear (forward- less preferred, or backward- more preferred), to the listening position.

    3) Dipoles can obviously work, but you won't really get flat freq response.

    My surrounds are about 7 ft away and actually are wide dispersion. I guess I'm trying to figure out now whether to keep them or go omnipolar.


    Wayne- Since you're watching this thread. I had an epiphany (!) the other day. I still remember your post about "flat" frequency response vs a house curve. What I think of as flat, isn't, and that was your point. That even if I measure a flat curve, with C-weighting on the Radio Shack meter, it actually is a house curve because of the compensation of the meter, just that the human ear is less sensitive to lower freqs and that's where "C-weighting" comes from. Kind of neat.


    One more. I mentioned the Mirage mains and the tunnel like sound I was getting from them. I had them 1/9 the depth of the room out from the front wall. I moved them to 1/7 (~23 inches to ~29"), and it was really neat in that the image moved from behind the front wall (hence the "tunnel") to in front of the speakers where it belongs. Neat!
     
  4. Wayne A. Pflughaupt

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  5. Kevin C Brown

    Kevin C Brown Producer

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    Wayne- The last part is re the 1st post of this thread.

    Yeah, the house curve stuff is from the really long thread a little while ago. [​IMG]
     

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