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Austin DIY HT Projects

Discussion in 'Home Theater Forum Meets' started by Nils Luehrmann, Aug 20, 2002.

  1. Humphrey

    Humphrey Stunt Coordinator

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    Just FYI, anyone looking for a rack enclosure for their equipment (something that can be built into a wall even) I have a enclosure with rackmounts, fan cooling, internal power strip and front and rear locking doors I'm getting rid of. About 50 inches tall. PM me if you are interested.
     
  2. pmeyer

    pmeyer Agent

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    I saw the rack, mailed back and forth, and then ended up missing by a few minutes grabbing it. Oh, well. At least it got me thinking about where I'll put my equipment. It may even be a good thing that I didn't grab it, because I'm thinking I'll put my equipment into a wide/low nook I've got in the back right of my theater and this rack would be just a bit too tall. The nook can be seen in the 6th picture down in the before pictures on my home theater construction page.
    I'm thinking I'll use it as a combination equipment area/bass trap.
    The destruction plans have been submitted to Bee Cave and I should have my permits early next week. May the destruction begin! Once I get it empty and can sit in it and visualize, I'll start thinking about where everything goes.
    When I called Ken Humphrey for the rack, he spent an hour on the phone with me doling out all sorts of useful advice. At this point my biggest challenge is to avoid getting overwhelmed by the options and decisions I need to make! Projectors, screens, sound isolation, acoustic treatment, equipment, cabling, seating, risers, theater style and color, stage, columns, you name it.
    My plan is to keep making forward progress on things I know I'm going to do (like removing the wall, working on sound isolation, etc.) while I slowly work my way through the pile of decisions and turn it into a plan. I don't mind redoing stuff, the journey for me is going to be as much fun as the destination.
    One cool idea Ken had was to open up vents or cloth covered openings into some of the lower ceiling areas and use them as bass traps. The structural ceiling is the 10' middle ceiling anyway, the rest is essentially suspended from it. I'll have to think on that one.
    Paul
     
  3. Chad Anson

    Chad Anson Second Unit

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    I turned a couple of columns into bass traps. Jonathan measured my room and made recommendations as to the size, location, tuning frequency, etc. I highly recommend his services.

    I'm thinking of redoing my rack so that it can be pulled out. Currently, my rack looks nice but is a real pain make changes to. Middle atlantic has a rack that will work, but I'm still evaluating.

    Are you going to be going the "room within a room" route for sound isolation (i.e., framing the interior of the room so that it is physically decoupled from the rest of the house)? If not, its going to be hard to get to true isolation. We did it for everything except for the ceiling (where we used metal Z-clip hangers... I can't remember their real name). Unfortunately we get sound leakage from the theater up to the master bedroom above. It's probably due more to the shared HVAC returns than anything. We have complete isolation from the bedroom that shares the wall with the theater.

    I'll try to host a movie night soon so that you can see it in person.
     
  4. pmeyer

    pmeyer Agent

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    The room is already built and drywalled as a media room room-within-a-room (or two-rooms within a room). I'm just knocking out an internal partition wall.

    It was built into unused attic space, and where it abutted existing rooms, a new 2x4 wall was built with about a 4-6" gap to the other room's wall. Unfortunately, they didn't insulate the new wall in all cases (something I'm fixing). The floor is a 2x10 floor with a 4" gap to the 2x6" ceiling of the rooms below. The ceiling and half of the walls are out into open attic.

    This room has a separate HVAC, so that shouldn't be a transmission path.

    Before I do anything, I need to go up there and blast some bass, then go around and measure the SPL (or just listen) in various places and see where I need the most isolation. I'll pull up as much of the floor as I easily can and make sure it is well insulated under there.

    I'm mostly attacking it now because it will be relatively inexpensive and very easy to do now ($1000 for sheet rock/green glue/pink fiberglass) since I'll have to get texturing/painting done as part of my wall/cabinet removal. It would be much more of a pain to fix it later if I find a problem when I'm done. The way I figure it, the more thorough I am now, the louder I can blast my movies!

    I'd love to come over for a movie night and see what you've done!

    Paul
     
  5. Humphrey

    Humphrey Stunt Coordinator

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    Yeah Chad, I mentioned he needs to see what you've done sooner than later. Also gave Jonathan a plug, as I wouldn't hesitate to use him if I was building a room. I have his (Mirus) speakers, too bad I don't have the luxury of a room I can alter enough to use his acoustical treatment measurements and recommendations. [​IMG] Bring on the movie night. I have a PS3 BluRay if you want to try a HD movie.
     
  6. pmeyer

    pmeyer Agent

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    I know this thread is sort of dead, but I'm going to post info here I think will be useful for future Austin HT'ers. Maybe we'll liven things up a bit.
    I found a cotton insulation source in Austin: Ecowise (www.ecowise.com) on south Congress. They've got r11-r13-r19 (1.5", 3.5", 5.5" 1.5 lb/ft3, comparable to fluffy fiberglass). It'll make great bass traps, etc. And it's cheap. $50 for an 80 sq ft roll of the 3.5" stuff.
    I would actually like some 1.5-2" thick denser cotton insulation (maybe 3-4 lbs/ft3) for wall treatment. I'm exploring how to use the thicker stuff in this thinner/denser application. I can either compress it with the covering material (GOM or equivalent), or attempt to heat it and densify it. It's made of recycled denim mixed with some polyester and baked. The polyester melts and holds it together. I'm thinking of running it through a heated roller (a torch or heat gun and some metal pipe) and thinning it down to what I want. A quick sample on the stove wrapped in aluminum foil compressed down just fine.
    The destruction on my HT proceeds. Check out http://www.meyerzone.net/meyerht for the latest pics and plans.
    My latest problem is that I've made the mistake of viewing SandmanX's home theater thread over on AVS, and now I have visions of mega screens, fine veneers, and dropping $20k on speakers. Drool.
    Paul
     
  7. Leroy R

    Leroy R Stunt Coordinator

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    Looks like the destruction is coming along nicely. I always like that part, the problem is that when your done, typically you have to put it all back together again.
     
  8. pmeyer

    pmeyer Agent

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    Darn, really! I guess I hadn't thought that far ahead.

    I am having a blast with this (although it's going slowly as my wife is out of town and I have the kids). I've started eyeing other parts of the house with a different eye (do we really need that wall? I wonder what is behind it... Honey, pass me the measuring tape and the sawzall)

    Fortunately, I'm in no hurry at all. Superbowl 2008, here I come!
     
  9. Humphrey

    Humphrey Stunt Coordinator

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    Didn't I tell you that was a awesome thread? But more importantly, you thinking about a SMX screen now with your speakers behind it?
     
  10. pmeyer

    pmeyer Agent

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    I've got a small foot gash from walking around barefoot in the back yard to flip off the power, and a couple of split finger tips from pulling down drywall without gloves.

    I am looking at SMX for a transparent screen. My only problem is that I don't really want to give up room length for a false wall. There is eight feet of empty space behind the screen wall: putting the main speakers behind that wall and framing arbitrary sized holes wouldn't be a problem. The center speaker is an issue, however: a support beam runs vertically through the center of the screen. The center would need to be in front of or next to that.

    Another option is to use a pair of center channel speakers, one on each side of the beam.

    I'm not there yet. Once I get the room cleaned out and start shopping for speakers I'll figure that out.
     
  11. Jonathan DA

    Jonathan DA Screenwriter

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    A pair of center channels would not be good, you'll end up with comb filtering effects that will create a very lumpy freq response and interfere with dialog intelligibility. If you use a center speaker that has the tweeter offset to one side, then you can push that side up against the beam such that your tweeter is likely to only be about 4-5" off center. With the speaker behind the screen, the brain is going to localize the sound to the visual image on the screen rather than the visual image of the speaker cabinet. Chances are no one would ever realize the speaker was off center.

    Alternatively, you could tear out the beam and replace it with a beam on each side of a perfectly centered speaker.
     
  12. pmeyer

    pmeyer Agent

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    So no dual speakers then.

    I guess my thinking is colored by my current horizontal center (woofer-tweeter-woofer). If I mounted it (or my new center) vertically, the offset wouldn't be too bad.

    As for the beam, my only hesitation is that I would be into structural work (structural engineer or architect: $$). I'll hold off on that until the current round is done.
     
  13. Henry Gale

    Henry Gale Producer

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    Found what I think is a real bargain today.
    There's a new consignment shop over at the Galleria, near Hwy. 71 & Bee Caves Rd. Behind the Backyard.
    So, I'm in the back of this big cluttered store and I spot a Bell'Ogetti component rack, with a matching TV stand.
    They were asking $199.99 but when I hesitated they immediately went to $175.00.
    Uh, I didn't buy it, it's still there (I guess, possibly, perhaps).
    It was tempting as hell but the fact is I've got a real nice 6 shelf Bell'Ogetti rack and I'm not planning to build a new little HT upstairs anytime soon
    It's a 4 shelf adjustable rack, the TV stand has 2 glass shelves.
    Go get it! Somebody!
     
  14. pmeyer

    pmeyer Agent

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    Weird, I live about two blocks from there. I'm tempted to run over, but I'm resisting. From what I can see of Bello racks, they are attractive furniture designed to be out in the room. I'm looking for more along the lines of bolt on rack mount equipment closet stuff that will not be visible.

    By the way, for anybody looking for that store, I think it is called 'World Market' and it's to the left of the Petsmart and across the way from Best Buy in Bee Cave.
     
  15. pmeyer

    pmeyer Agent

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    Actually, the one I was thinking of is called the "Home Consignment Center" in Bee Cave. (World Market is a few stores to the right). I stopped by just for the heck of it to take a pic in case anybody wants it, but they are open 10-8 on weekdays. I can stop by there tomorrow night on the way home if anybody wants a better description.
     
  16. pmeyer

    pmeyer Agent

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    Jonathan, total noob question here:
    My current horizontal center has a single tweeter and a matched pair of mid-range drivers, one on each side, with a crossover around 2KHz. I would estimate the two mids are about a foot apart. How do they avoid comb filtering issues? Is it more of an issue above 2 KHz (hence the single tweeter)?
    I'm not really proposing anything, just trying to learn, but if I had three separate drivers: a tweeter just to the right of the beam and a pair of mid-ranges a foot to the left and right of the tweeter, what would be the issue? Both mid-ranges connected to a single amp off the same (or matched) wires.
    Specifically, is it a case of:
    1) It would not work because...
    2) In theory, one could build such a weird custom speaker, but in practice it would be difficult to avoid problems, or
    3) It would work, it's just a lot easier to move the beam and put in a single center.
    Just curious. If I decide to go center behind the screen, I'll likely build a false wall, center the screen slightly to one side or the other, or move the beam.
    By the way, new pictures are up. The old room is out. I have some more ceiling destruction to do, then it's time to start rebuilding. http://www.meyerzone.net/meyerht/
     
  17. Jonathan DA

    Jonathan DA Screenwriter

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    Paul,

    The answer is...the speaker doesn't avoid comb filtering! In order for two drivers whose centers are 12" apart to minimize comb filtering (aka lobing), the drivers would have to operate below the frequency of a 12" wavelength. A 12" wavelength is roughly 1000Hz. You will rarely find a two-way speaker with a 1000Hz crossover. The only ones I can think of are the Linkwitz Pluto, and a few pro-sound speakers that use large horns.

    So you might be wondering, "if a horizontal MTM with a 2kHz crossover causes a loss of dialogue intelligibility, why do they sell them like that?" The answer--Marketing! The vast majority of speakers are sold on wow factor, and one of the biggest elements to wow factor is visual appeal. Most people think symmetrical horizontal speakers are much more visually appealing than odd designs that manage to vertically squeeze a tweeter and midwoofer into a horizontal form factor. So even though the engineers know its a compromised design, they create them so that marketing can actually sell them to a buying public that's more interested in looks that actual performance.

    If you go with the acoustically transparent screen, I'd suggest using a traditional upright speaker design rather than something that's marketed as a "center channel" speaker. There are exceptions, but in general this will yield the best sound.
     
  18. pmeyer

    pmeyer Agent

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    Very cool. Thanks for the useful information.

    Assuming the two woofers are matched and in phase, I assume that the center-line wouldn't have this problem. The primary listening spot (assuming it's centered on the speaker) wouldn't see any effect. Sketching it out, 5" off the center 10' away would see the first null at ~13KHz, out of the woofer range (the woofer spacing is actually 10"). At 4' off center, the first null is at 1.8 KHz. Cool, I actually get it! With a 2KHz crossover, this center channel has a bit more then a 6ft wide spot with no comb filtering at 10'. Beyond that, I'll start to get peaks and nulls down to about 1KHz (all the way around at the front wall).

    I take it this applies to all speakers with multiple drivers in the same frequency range? I see lots of highly rated tall vertical speakers that appear to have multiple vertical woofers. They would have a vertical comb filter problem. However, looking at them, they tend to be three way speakers. I suppose the woofer->mid crossover must be low enough to eliminate the issue.

    --------------------------

    I was thinking about audio the other day. The conclusion I came to:

    With the theater construction, I have enough to think about without digging into the intricacies of speaker shopping right now. I'm going to start with my Marantz SR8000 and my 5.1 paradigm setup (non-ideal, but works for me).

    Once I have the theater in and have a baseline performance expectation, I'll start listening/measuring my sound, and auditioning alternatives. I'll see where to go from there.

    In the meantime, I'll keep reading and learning (and listening if I get the chance)

    Paul
     
  19. Jonathan DA

    Jonathan DA Screenwriter

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    Sticking with your current speakers will work fine for now. The Paradigms are nice little speakers. For an easy center channel fix, just take your existing speaker and turn it vertical, centering the tweeter at your ear level behind the screen. Then you're pointing the nulls at the ceiling and floor. It still monkeys with your power response, but that's a secondary concern at this point.
     
  20. pmeyer

    pmeyer Agent

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    I need advice:
    As you can see in this picture, I have three cabinet cavities across the screen wall and one on the front of the right wall. The right front corner (where the TV hole is now) is going to be squared off.
    [​IMG]
    Options:
    a) remove the cabinets completely and drywall the wall.
    b) remove the cabinet fronts and leave them flush to the wall. Fill them with cotton or 703. They'll be covered by GOM or equivalent when I treat my front wall. Essentially free bass traps in non-ideal positions. No implication that they would be the only bass traps (I'm still looking at soffit and corner possibilities).
    Thoughts?
     

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