Brett's Home Theater

Discussion in 'Home Theater Projects' started by brettJconley, Nov 21, 2005.

  1. brettJconley

    brettJconley Extra

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    First, let me introduce myself. I've been a dreamer for many years, only wishing that some day I'd have the chance to build a custom home theater of my own. I took a baby step about a year ago when I bought a HTIB. (There wasn't much point in going any further than that--nowhere to put it.) I now have an explosive opportunity to do something really awesome, as we have just moved to a new place where we can afford an awful lot more house than we ever could before, and one of the things this house will have is a dedicated basement home theater.

    So with that in mind, please help me with my questions. First of all, most basements (including mine) are about 8 ft high. I want a home theater with a terraced floor. The room is about 13x19, and I've had the architect draw the room 2 ft lower than the rest of the basement, so that you walk in the back of the room at the same level as the rest of the basement, and the top terrace is also on that level, and then step down to a lower terrace, and then finally down onto the floor of the room. Make sense?

    So, my question is, assuming the 13x19 part is unchangeable, is 2 ft optimal? Will I still be looking at the back of someone else's head?

    Also, I'm not sure how deep I need each terrace--my couches are about 3.5 feet deep, so I thought 5 feet per terrace might work out right. Is 1.5 feet of walkway/leg room good enough? And at 5 feet per terrace, a couch on the bottom floor will be about 7 feet away from the screen. Is that too close?

    If there's some how-to home theater site or document out there, I'd love to read it. I'd also entertain the idea of a good descriptive book.

    I've got tons more questions (which is why I just labeled the post "Brett's Home Theater", rather than some specific question). But I'll wait on those and ask them gradually.

    Thanks,
    Brett
     
  2. David Noll

    David Noll Stunt Coordinator

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    Brett,

    Sure makes sense with me, it is exactly how my theater is terraced. My height for each level is 8" (2x8 plus 3/4" Advantec sub-floor). No problem with sight-lines. My middle terrace is 6'6". Remember, if front row reclines and row behind has leg rests up it can be tight.

    Look at my link below.



    I think you should try get back a little more. My front row eyes are at 11'. I have a Runco projector and can sit at less than 9' but picture becomes too big making for eye strain from constantly scanning picture.

    Good Luck,

    David
     
  3. brettJconley

    brettJconley Extra

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    Wow, I guess you're right. And I was thinking of doing an even bigger screen, so there's a real big reason to keep the front row back as far as I can. I was just trying to make it as much like a real theater as I can, and every one I've seen has the screen almost as wide as the room.

    My room (I re-measured) is 13x18, rectangular. I'm thinking maybe the room is actually just a little bit too wide for how long it is. If I go 4 ft per terrace, the back one will be from 18' back to 14' back and the second will be from 14' to 10'. I don't think I'd want to make them less than 4', would I? That's still going to put the front row at 10', assuming the viewer is leaning back all the way.

    Is there a formula or recommendation for the optimal screen size based on a given viewing distance? I think maybe I'd use something like that for the middle row, and then the back and front rows would be less than optimal.

    I also noticed in your pictures that your projector is mounted above the viewing area. I had planned on putting mine behind it, so that it shines through a window that is flush with the back wall, which is right behind the back row of seats. That will maximize my projected image size, so I can get it around 10 or 11 feet wide (I'd like a 2.35:1 movie to fill the width and height of the screen, and lesser movies still fill the height, and just less of the width). Am I sounding reasonable?

    Thanks,
    Brett
     
  4. David Noll

    David Noll Stunt Coordinator

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    Brett,

    Different projectors have different ranges as to where they need to be placed. You'll have to decide on PJ first and see where it needs to go OR find a PJ that meets your distance requirements.


    No! 4' might be a little tight depending on foot rests etc.

    David
     
  5. brettJconley

    brettJconley Extra

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    Okay, well, I've already kind of settled on the InFocus ScreenPlay 4805 for now (it's very budget-friendly, and sounds like a good start for someone who's never had a home theater before). And what I've read tells me it needs to be about 18 feet away from the screen to project the size I want.

    I'll think about the terraces and go ahead and do whatever seems best when the time comes. So now that that's all out of the way, here's some more to think about.

    I was reading about soundproofing here and there and somewhere I heard about the idea to completely isolate the room. The guy's recommendation involved putting some kind of foam directly on a recessed floor, covering that with two layers of 1/2" plywood, then building walls on top of the plywood that were isolated from the adjoining walls (using some kind of isolation connector things), with a ceiling and everything. Then the whole room is isolated. Is that the best way to go? I have the room for it, and since I'm still in the planning stages, I don't have a problem if that's the way to go. I'd still go with the double layer of sheetrock with the rubber sound membrane stuff in between them. Is there more I can do without getting ridiculous or fanatical?

    And I'm also wondering about the ceiling. I'd really like a smooth sheetrocked ceiling with recessed lights. Is there a reason I should go with a hanging ceiling instead?

    Thanks again,
    Brett
     
  6. David Noll

    David Noll Stunt Coordinator

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    Brett,

    I personally think a completely isolated room is not necessary. First, since most of your room will be terraced, no need for anything fancy to be done to your floor. Second, my room is built with double layer sheetrock, nothing in between, and not really any sound transmission problems. The rest of my basement is used only for storage so the little bit of rumbling heard there does not bother anyone. Just make sure all walls are stuffed (double the usual) with insulation. Third, the ceiling can be sheetrock, double layer, joists double-stuffed with insulation. I used Armstrong acoustical tin-look ceiling tile(real tin not good). Upstairs you can hardly hear a thing when my theater is blasting! Just an occasional rumble.

    No need to get "ridiculous or fanatical".

    David
     
  7. brettJconley

    brettJconley Extra

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    Yeah, you're probably right. The floor is going to be recessed already, 2 feet lower than the floors for the adjacent rooms. Also, since the adjacent floor are higher, then the walls for those rooms will also start higher. So out of necessity, I will actually have the walls inside my theater isolated from the adjoining walls (I gotta have something to screw the sheetrock into).

    But actually, it's up that I'm most worried about. The occasional rumble is what I'd like to avoid if possible. No one worries about the quiet scenes annoying the people upstairs. So maybe just a little extra attention to the ceiling area might be in order. I think I might go ahead and isolate the ceiling from the joists to have that extra degree of separation and avoid kitchen disturbances.
     
  8. Greg Monfort

    Greg Monfort Supporting Actor

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    Greets!

    Cinemas are basically designed back-to-front since screen size is dictated by how far away and how high the last sight line is. Assuming the standards/guidelines haven't changed since I researched this stuff, max viewing distance is 11 deg (~5.2 screen widths) before the average person can't read captions or lose too much detail.

    For SMPTE it's a 30 deg (~1.866 screen widths) minimum viewing angle, THX/26 deg (~2.166 screen widths), with 36 deg (~1.54 screen widths) recommended. Minimum distance is one screen width or whatever yields < 35 deg off the vertical axis viewing angle to the top of the screen, but in HT it's of course whatever your eyes/system resolution dictates, which usually means limiting this angle to < 20 deg.

    WRT terrace spacing, it's whatever works for your seats plus at least 26" walking space and the max horizontal sight line is < ~80% of the screen height.

    WRT room design, since this is a dedicated HT, might as well do it up ~right from the get-go IMO, which means tapering the walls/ceiling at a ~1":12"/side (~9.53 deg included) to reduce eigenmode (standing wave) amplitudes to a relatively benign level and using high mass, softly sprung walls/ceiling as huge diaphramatic bass absorbers, like in a real cinema. Using the same ratio to splay the rear wall in a 'V' will help with the problematic primary axial ones. Blocking off the corner 'points' to keep from developing acoustic 'hot spots' creates a good place to flush mount the surrounds/storage racks/whatever, while sloping the ceiling with a soffit 'step' over the screen makes a good place to put the FOH channels.

    Isolating the floor would be a nice touch, but a poured concrete floor doesn't transmit much if the 'absorbers' combined with the dead air space works well enough. For sure, don't rigidly attach any portion of the HT's walls/ceiling to the main structure or the ceiling to the HT's walls.

    So at a glance, with a nominal 13 ft x 18 ft, the available width would be reduced by ~11" thick construction/air space minimum on all sides and ~24" due to wall taper, so call it a ~120"available screen width. That ought to make a 2.35:1 movie a near Cinerama! experience if the projector can handle it. With a nominal 8 ft ceiling, the front 'pit' will need to be pretty deep to get the desired ceiling angle/line of sight though , but you can graph it out easily enough with the limits given once you know how close you can sit based on eyesight/system resolution, etc..

    GM
     
  9. brettJconley

    brettJconley Extra

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    Okay, this is getting good now. I have a modest understanding of what you're talking about with standing waves and bass absorption, but to clarify what you're suggesting, tapered walls? So the walls are slanted in toward the room as they go up to the ceiling? 1":12" would mean that a 10' ceiling would mean the top of the wall sticks into the room 10" more than the bottom of the wall. Is that what you mean? How do you build a slanted wall? (Sorry, I'm not a carpenter, but I've been planning on doing the framing and other construction myself.)

    What is a high mass, softly sprung wall? High is relative--double sheetrock might count, or you might be talking about adding further mass. I don't think I'll be adding anything like MLV--I checked the price and $4000 is too much for this project.

    FOH channels?

    That's about it. Thanks again guys.

    Brett
     
  10. Greg Monfort

    Greg Monfort Supporting Actor

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    Greets!

    Sorry, 'FOH' is prosound speak for 'front of house', i.e. stage PA speaker stacks, cinema screen/LFE channel speakers.

    Tapered front (screen wall) to back, like an amphitheater, not top to bottom.

    'Massive/sprung' as in a wall thickness with a density of at least 180 lbs/ft^3, such as a bonded pair of 49" x 97" x 3/4" and 5/8" MDF mounted with isolation channels sufficient for the weight. IOW, ideally you want ~16 Hz transmission to be > -25 dB, which equates to a sound transmission curve of at least 80 (STC-80). The easy way is to use THX approved QuietRock.

    Hmm, building a successful low frequency isolation chamber isn't a casual DIY project since any screw-up can mostly defeat it, like not properly sealing a vented design tunes it way too high, so I recommend either studying up on how to do it right or pay a licensed sound contractor to at least generate detailed plans/material specs, if not the actual install. For sure, don't expect a general contractor to be knowledgeable enough to do it right and/or warranty it.

    GM
     
  11. brettJconley

    brettJconley Extra

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    MDF? For walls? I would never have thought of that. Is that a better material for sound than sheetrock? That would actually work better for what I'd want to do, I guess. I want to use carpeting and cloth to cover most of the walls, and I think that would be an easier job if they were MDF rather than sheetrock.

    As far as the low frequency isolation, I don't think I'll be doing anything about that. Not consciously, anyway. This is a limited budget theater, as most are I'm sure, and I'm not going to hate it if the bass isn't a perfect reproduction.

    I like the tapered wall idea. Another thing I hadn't and wouldn't have thought of by myself. Even though that skinnies up the screen wall a bit, if it leaves me 120" wide, that's 130" diagonal for a 2.35:1 screen. I was shooting for 144", but 130" is great--way better than any TV.

    Where do you buy stuff like isolation channels online? I'm nowhere near any kind of supply store or warehouse. And where's the best place to buy a fixed screen? Everywhere I've seen seems to concentrate on portable or hideable. I'd rather not even pay for a nice-looking frame. I have other plans.

    Thanks,
    Brett
     
  12. Greg Monfort

    Greg Monfort Supporting Actor

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    Greets!

    It's all about density when trying to isolate low frequencies, so it doesn't matter what the material is as long as there's enough to get the job done.

    Do a Google search for the hardware.

    Make your own screen, they're super easy to do and cost only a small fraction of a Stewart or similar. There's plenty of info on the various HT forums and IIRC, there's an excellent one on this site, complete with various coatings comparisons. The biggest problem is moving/installing one > a single MDF sheet wide. Frankly, since this is a dedicated HT, I'd just make sure the screen wall was super flat/smooth and paint one on it, plenty easy to do with MDF walls. I doubt the wall would move enough damping the LF to visibly blur the image, but even if it did it would only be during an action scene where it would already be blurred. [​IMG]


    You're welcome!

    GM
     
  13. brettJconley

    brettJconley Extra

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    I used to work at a movie theater and helped once with a complete renovation of the place. I noticed then that real movie screens are some kind of stretchy plasticky material that is stretched over a really big frame. Can this fabric be purchased anywhere? I noticed it has little holes in it, and maybe that would be inappropriate in a home theater where the people are really close to the screen, so they might be close enough to see the holes. But is there something like it that could be stretched over a rigid frame? Is there a disadvantage to doing a screen like this?

    I was also thinking about speaker placement. In a real theater, the auditorium is so big that no matter where you're sitting, there's always a left surround speaker to the left of you, a rear surround behind you, and a right surround to the right of you. In a squishy home theater, where the back row seating is right up against the wall, with a 6.1 surround system, someone sitting on the left of the row would have a left surround to the left of them and a rear surround to the right of them. Someone sitting on the right of the row would have a right surround to the right of them and a rear surround to the left of them. Would there be a benefit in spreading the center surround output from the amp out over 2 or 4 different speakers, spaced evenly along the back wall (matching resistance, of course)? Then the rear surround would be behind everyone.

    Are there any other suggestions to evening out the sound for everyone (short of investing in some big expensive 9.1 system or something like that)?

    Thanks again!
    Brett
     
  14. Greg Monfort

    Greg Monfort Supporting Actor

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    Greets!

    Sure! Stewart, etc., will sell you just the material. WRT mounting speakers behind the screen, cinema screens have only ~5500 perforations/ft^2 that are large enough to pass the high SPLs required, ergo they are too large to be ~invisible (at least from the front row) and too few to get enough transparency for the typically low efficiency speakers used in a HT app, so THX developed a >30 k/ft^2 standard using much smaller perforations. Stewart, etc., can perforate any of their screen materials for an additional fee ($$). This is the only way to do a dedicated HT right IMO and I'm amazed so few folks (especially DIYers) do.

    Ditto using prosound horn loaded studio monitors to scale the 'sound' of a cinematic experience. I mean I was looking at some pics of a local's new HT that easily cost more to build than replacing my home (even before the electronics are factored in!) and his sound system was at best, college dorm quality! Oh well, we each have our priorities. For me it's about the sound first, then the pic size, then the room's style.

    A standard multiple rows mixing/dubbing stage will typically have a surround channel for every two rows, but the more spread out rows of recliners and/or ample walking room dictates one/row if the correct controlled directivity speaker is used instead of the typical bi- or di-pole required when only one/channel is used. Anyway, the surround channels are strictly for special effects 'fill', so you can use as many speakers as you want since we rapidly reach a point where our internal processor overloads from too many inputs and just ~sums them into one.

    GM
     
  15. brettJconley

    brettJconley Extra

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    Okay, on to something else. I've decided that I'm going to computerize my house. Everywhere in the house will be networked, and all my DVDs will be accessible through the network. At each location that has a TV, there will also be a computer connected to the network and equipped with DVD playback software. This way, nobody has to tromping around the house looking for a DVD that's at some other TV.

    So, the thing I'm concerned about is quality. Doing everything through electronics only, you have your DVD player, and perhaps a video processor to maximize the clarity of the picture. Doing it all through a computer, the DVD playback software handles all the scaling, typically scaling everything to fill the screen.

    My question, then, is: Is the scaling done by a computer inferior to the scaling done by a video processor (or a capable DVD player)? And are some DVD programs better than others (or the drivers used by the programs)? Are there some that can do a constant-height picture, stretching a wide-screen movie vertically so that I could flip on the wide lens?

    If it's way better to go with specialized electronics, I could just keep my DVD collection in the home theater, and use the network for everywhere else, since I'm not terribly worried about quality elsewhere.

    Thanks again,

    Brett
     
  16. brettJconley

    brettJconley Extra

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    Actually, now I'm not sure I want to use a computer for the source. I'm aiming for a constant-height setup, with a 2.35:1 screen. If I can get a computer to stretch all the images to fill the full height of the display, I can use a lens to stretch it back out.

    But I don't see any way to do it. One possibility is to just use the output resolution of the video card. Just choose a resolution that's the same as 2.35:1. But the closest thing to that I have on this PC is 1280 x 720, which is only 1.77:1, the same as 16:9.

    The other way would be to have a DVD playback program that can stretch the image vertically. Then the lens stretch would only apply to the wide aspect movies. But Windows Media Player and PowerDVD don't do that.

    So, does anyone know of any good software that will do this? Alternatively, does anyone know of a video card with drivers that support a 2.35:1 resolution?

    Thanks,
    Brett
     

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