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Building A Home Theater? Start Here.

Discussion in 'Home Theater Projects' started by Brian Dobbs, Sep 25, 2014.

  1. Bob Bielski

    Bob Bielski Second Unit

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    I just want to know if the sound would improve mounting the speakers with the tweeters closer to the walls, to get reflections off the walls and increase the sense of space, or with the tweeters all together into the center of the room. My first guess would be tweeters on the outside of the 4 speaker circle, but before I make a grave mistake maybe someone with acoustic training could shed some light on the proper set up and explain why one way is better than the other. Brian your forum is so thorough with information that I thought this bit of information might help others as well as me. Thanks for continually adding to the treasure of information for the entire site, very much appreciated.
     
  2. JohnRice

    JohnRice Executive Producer

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    Interesting.

    My main thought is about phase problems and orienting the speakers (as close as possible) to how they are designed, relative to the listener. The drivers, especially the tweeter and midrange, are suppose to be spaced perpendicular to your ears to avoid phase problems in the crossover range. In other words, they are spaced vertically, because your ears are spaced horizontally. There's a reason for that due to the distance between your ears, when those drivers are spaced vertically, both drivers reach both ears at the same time. So, my point is, I suspect the best orientation is for the speakers to be oriented front to back of the room, not side to side.

    Have you considered that despite the logic you're using, you intend to use the speakers for a radically different installation than they are designed for? They simply aren't designed to be installed on a ceiling, and their driver layout it is not created for that use. Depending on the height of the ceiling, I can envision the results just not being exactly ideal.
     
  3. Brian Dobbs

    Brian Dobbs Ambassador

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    Let's take just two of these speakers, say for a front row. If you were to mount them tweeter in, is there sufficient space between the tweeters so that there is some semblance of separation? If so, then go that way. I'm not a fan of reflections that make the sound difficult to localize.

    If you have to go tweeter out, then I would say install some sound dampening near the speaker on the wall closest to it so that you minimize reflections.

    https://www.hometheaterforum.com/community/threads/building-a-home-theater-start-here.334769/#post-4204566
     
  4. Bob Bielski

    Bob Bielski Second Unit

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    Both responses are very interesting. John I was unaware of the phase issue. Maybe I should build custom cabinets like my center channel, using all OEM crossovers and drivers, making the cabinets TS parameter correct, and do woofer mid tweeter woofer as a layout. I have several options to get it done but wish I got the proper information from someone trained in acoustics before I commit. I have ARC for room correction and I am sure it may correct some phase issues but it works better with correct layout.
    Brian the ceiling is 8 feet high and I would be willing to pay a contractor to recess the cabinets into the ceiling. My empty attic is above. There is plenty of space to maintain separation.
    And John I always trust your judgement as I have seen many posts helping others with accurate information, but please clarify what front to back not side to side of the room relates to the seating position. Unfortunately my living room is my theater room and instead of the proper way of setting up, long length speakers placement, it is set up short length because one end has a big picture window. I have to compromise in order for the room to function. I have to do some research, but I am sure this issue has been addressed by now since object based surround has been out long enough. Thanks for the info from both of you gentlemen.
     
  5. JohnRice

    JohnRice Executive Producer

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    Bob, think about it this way. From the perspective of the viewer, the tweeter and midrange should be vertical not horizontal. This is really getting into the weeds of sonics, but when certain frequencies come from two sources, especially when they're close together, they tend to cancel themselves out when the two sources are horizontally spaced. This is because there is a crossover between the sound from each source to each ear. Anyway, it's why midranges and tweeters are always aligned vertically to each other, but not necessarily directly above woofers.

    From what I can tell, the most important aspect of Atmos speakers is that they have wide dispersion. They're supposed to, ideally, be in the ceiling, aimed straight down. So, the wide dispersion eliminates the need to aim them. Think of the sound of rain hitting a roof. That is what Atmos is designed to reproduce. The sound of the rain isn't directed at you, so it sounds a little different when you are directly under it than it does if it's in front of or behind you. That's what Atmos is trying to reproduce. At least, that's a way of looking at it. So, it seems to me that the ideal Atmos speaker design probably has coincident tweeter and midrange (with 3-way) and extremely wide dispersion.
     
  6. Bob Bielski

    Bob Bielski Second Unit

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    Most of the layouts have the height speakers directly above the front L and R and surround L and R. My speakers have a wide dispersion pattern the mids and tweeters are domes, and I just got off the Dolby site and sent them my inquiry about whether or not to aim the tweeters in or out and whether to change the driver layout to woofer mid tweeter woofer or not. I hope they will let me know. Some sites suggest wall mounting half way up the wall from floor standers to the ceiling. You would think by now they have hard and fast rules with explanations as to why.
     
  7. JohnRice

    JohnRice Executive Producer

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    In line with them, yes, but I find an awful lot of people locate them on the wall or on/in the ceiling far too close to the wall, or directly over the viewers' heads.

    You've probably seen THIS from Dolby, which shows that they should be in line with the front speakers, and roughly 45 degrees in front of and behind the viewer.
     
  8. Bob Bielski

    Bob Bielski Second Unit

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    Just an update on my research for heavy duty ceiling mounts. I have bumped into a company that supplies commercial installers, and they have a bracket that looks very heavy duty. I had to register in order to buy and now I am waiting for an approval. I have done a lot of reading and what I have gathered is that reflections are not advised from the height speakers. The brackets that I have my eye on can swivel and tilt. I will leave the link, and will update with new information as I have some. Hopefully this will help other DIYs who are crazy enough to mount floorstanders on their ceilings LOL.
    http://www.zuummedia.com/
     
  9. Message #69 of 74 Feb 20, 2020
    Last edited: Feb 20, 2020
    Jeffreybomb

    Jeffreybomb Stunt Coordinator

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    Our home theater is being built in the basement. I think the room-within-a-room build would be overkill, since the basement doesn't see nearly the amount of use as the ground floor.

    However, I'd like to keep the noise from getting through drywall and joists in the ceiling. Would I benefit from mounting drywall on resilient channel around the entire room, or would it only really be beneficial if I installed it in the ceiling and attached the drywall to the wall studs as normal?

    I would assume I'd need resilient channel around the entire room, but I've been surprised before.
     
  10. Bob Bielski

    Bob Bielski Second Unit

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    I would just do the ceiling with resilient channel and double drywall, like quiet rock. The walls I assume are concrete since it is the basement. How high is the ceiling? Also I would stuff the cavity between the joists with Rockwool, https://www.rockwool.com/?utm_source=google&utm_medium=cpc&utm_campaign=brand&gclid=Cj0KCQiAnL7yBRD3ARIsAJp_oLY8H2wIQfGhZASOvsuugLJoppKW3HYvunRHyHcV7yA14bcEqRJaCvUaAg-WEALw_wcB
    I would also put a nice thick rug in the room above the theater. There is a material called Acoustibloc I hope the spelling is close enough, and you could put that down first, then a pad, then a nice super thick rug and with all that you should be good. I used safe and sound but if you have the room or the depth in between the joists I would go with a higher R factor, that is the same stuff as safe and sound just a lot thicker thus better sound reduction. Good luck and let the forum know how you make out. And please post some pics for everyone.
     
  11. Brian Dobbs

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    The question is, would anyone potentially be walking around above the home theater while you're in there? Wife who stomps around? Kids? Dogs? My neighbor across the street has mentioned a number of times how his ceiling-mounted projector always needs realignment after his kids upstairs stomp around directly above.

    If you truly want to minimize noise pollution, mechanical separation should not be considered overkill, but rather paramount. I have a room within a room, plus mass loaded vinyl, plus cellulose insulation and I can still hear activity upstairs.

    If there is wood that is screwed to other wood, even just with one screw, and that wood is part of a wall, you will hear noise from upstairs.

    If you can't mechanically separate the rooms, then you'll definitely need resilient channel everywhere, insulation, MLV (Acoustiblok) and the special sound dampening drywall.
     
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  12. George_W_K

    George_W_K Screenwriter

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    How well does Acoustiblock work with blocking out low bass frequencies?
     
  13. Brian Dobbs

    Brian Dobbs Ambassador

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    https://www.acoustiblok.com/acoustiblok-noise-solutions/

    Think of it this way. The more mass you can add to a wall, the better. Mass loaded vinyl turns sound waves into heat. It's just one tool in the bucket. A 1-2 foot thick wall filled with sand would be even more effective, but let's not get carried away...;)

    p.s. more power to you if you choose to do this.
     
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  14. Eve Babcock

    Eve Babcock Stunt Coordinator

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    Thanks for this.
     

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