DefTech Mains w/ "Dead" Front of Room - Bad Combo?

Discussion in 'Archived Threads 2001-2004' started by Scott-C, Sep 16, 2001.

  1. Scott-C

    Scott-C Supporting Actor

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    I wasn't sure if this post was more appropriate here or in the "Building a Home Theater" area, but since it is ultimately a question about speaker choice, I chose to post it here. Moderators, if you disagree, please feel free to move it elsewhere.
    This is a question that has been on my mind lately as I ponder building a dedicated home theater at some point. Some of you have indicated that it is imperative to make sure the front of a HT is acoustically "dead". By that I mean taking measures to ensure that there are no room-based reflections from the front of the room. I've visited many HT sites and read posts where some HT enthusiasts have taken measures to ensure this, such as putting a thick curtain behind your screen, putting sound absorption materials on the walls, and packing your front stage with sand. As I understand it, this is done to ensure no reflections from the front soundstage.
    Assuming you agree with this notion, can it be argued that DefTech bipolar speakers for the front L/C/R are a bad choice in this kind of room, since these speakers rely on reflections off of the front wall to help create a diffuse soundstage? Would monopole (direct radiating) speakers be a better choice if the front soundstage is "dead" this way? Are DefTech speakers effective with this type of room setup? I would think they would be a bad choice since you would be taking away on of their advantages, but am very anxious to hear what you think!
    Thoughts? Opinions?
    ------------------
    Scott
     
  2. Bob_A

    Bob_A Supporting Actor

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    IMHO the DT bipolars should sound great in almost any room, especially for home theater. Will it be possible for you to try out these speakers in the room?
     
  3. Scott-C

    Scott-C Supporting Actor

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    Thanks for the response!
    Well, I haven't built the room yet, so trying them out in the actual space isn't possible. However, I could try to fashion something similar in my current room (hang a large rug on the wall behind the speaks or something). Before I went to any trouble, I was curious to hear what members of HTF thought of this theory in general for bi-polar speakers.
    Wouldn't it make sense that the advantage of bi-polar speakers as front L/C/R would be negated in this kind of room? Why or why not? In my mind, I keep thinking there has to be some sort of negative to using bi-polars in this environment but I'm not sure.
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    Scott
     
  4. Bob McElfresh

    Bob McElfresh Producer

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    Hi Scott.
    You dont want to deaden the back wall with bipolars. You are correct in that this would defeat the purpose. In fact, for a HT system, you WANT some room reflections to give you that "Movie Theater" sense of spaciousness. (Some of the reviewers even say that they prefer some "liveness" to the front).
    With bipolars (and I feel most speakers) you are not trying to surround everything with sound-absorbtion material. The goal is to reduce what is called "early-reflections".
    Your speakers radiate some sound at 90 degrees. This can reflect sound off of the nearby side walls, and that nice, big RPTV sitting between them. These are the sounds you are trying to reduce. (Dont forget that your ceiling can reflect sound as well as the floor, but the floor usually has carpet to diffuse things.)
    Try this: get a mirror tile or some such and invite a friend over. Sit in your usual listening position and have the friend slide the mirror along the side-walls. You are watching the mirror and trying to find the location where you can see the tweeter on your speakers. Mark this location with masking tape.
    These are the places you will get "early reflections" from.
    For about $30, you can order a dozen panels from www.partsexpress.com that you can stick to the walls/ceiling at these locations. These are not absorbtion panels, but they are diffusion panels. The goal is to make the sounds reflect 2-3 times before they hit your ears, and increase the distance they must travel.
    You can do this for the wall behind your equipment as well, but my advice would be to use a laser-pointer and find the 90-degree reflection point and treat just these areas. Leave the wall directly behind your speakers alone because you WANT these sounds.
    A good book on this topic is "Sound Studio Construction on a Budget" available from Amazon.com.
    Good luck.
     
  5. Hubert

    Hubert Second Unit

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    Scott, my entire room is dead except for the top, back walls where the Def Tech rear surrounds are........and it sounds incredible. So, ultimately you have to tailor the sound to your liking. There is no one correct way for everyone. Experiment and set it up the way that sounds best to you.
     
  6. Doug_B

    Doug_B Screenwriter

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    I auditioned the BP2002TL at one dealer who had diffusion panels for the entire wall behind the speakers. The soundstage was bigger in this setup than for any other setup I had heard with these speakers (although I think the clarity suffered a bit toward the high end).
    Doug
    ------------------
    "Today is a good day to die." ...Old Lodge Skins
     
  7. Hubert

    Hubert Second Unit

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    Of course, with a dead room, the speakers emit a sigter sound than they would in a live room. If you're mainly going for home theater, I'd recommend a dead room. For mostly music, I'd recommend a much more lively and reflective room.
    As for the clairty issue, I've never seen or heard any clarity problems with Def Tech speakers. All the ones I've heard are extremely clean with tremendous clarity.
     
  8. Scott-C

    Scott-C Supporting Actor

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    Thanks guys. I'm primarily interested in home theater applications as opposed to music listening, and am thinking ahead to the day when I go to build my dedicated HT (not for a while yet, unfortunately).
    I'll be honest and 'fess up here - I was hoping there was a definitive (no pun intended) answer here, but it makes sense that to a certain extent, it's dependent on what satisfies the listener. I've heard many people talk about what a great acoustic benefit there is to things like curtains covering the entire front wall in a dedicated HT, but I did have a concern over what that would do to the performance of my BP10Bs and C1 center channel (old and probably needs to be upgraded!).
    Thanks again!
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    Scott
     
  9. Scott-C

    Scott-C Supporting Actor

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    Quote:
    "Try this: get a mirror tile or some such and invite a friend over. Sit in your usual listening position and have the friend slide the mirror along the side-walls. You are watching the mirror and trying to find the location where you can see the tweeter on your speakers. Mark this location with masking tape.
    These are the places you will get "early reflections" from.
    For about $30, you can order a dozen panels from www.partsexpress.com that you can stick to the walls/ceiling at these locations. These are not absorbtion panels, but they are diffusion panels. The goal is to make the sounds reflect 2-3 times before they hit your ears, and increase the distance they must travel."
    Interesting idea. At what height would I place the diffusion panels? Ear level and above (meaning multiple panels from ear level on up), or just where I would mark the wall with the tape (one panel, exactly where I see the tweeter through the mirror)?
    ------------------
    Scott
     
  10. Bob McElfresh

    Bob McElfresh Producer

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    Scott: As far as the placement of the panels go, you want the panels at the height you see the tweeters.
    Then consider your family. Taller/shorter? Go up down from there. Then repeat for people sitting next to you on the couch. This should give you positions in the horizontal range.
    This should give you an area to cover with panels. Since the ones I mentioned are 12" x 12", you may use 4 of them to cover the area, or you might have to go in a grid of 3 x 3.
    If you are an experimenter, I'd suggest the following:
    Mark the places on the walls where you see the tweeters now. Cover these areas with some folded blankets and try listening to some music. Do you hear much difference?
    (Music is a much better material to use in these tests. It has a lot more information than most movie soundtracks so it will reveal more. Make sure you use 2-channel mode on your receiver and turn off all DSP effects.)
    If you tie the blankets up with string, you can try a A/B comparison by listening for a few minutes with the blankets up, then suddenly dropping them in the middle of a song.
    This is a inexpensive way to test things to see if it's even worth buying a box or two of sound-diffusers.
     

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