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I need a Primer... HT Construction quesitons inside

685 Views 8 Replies 6 Participants Last post by  JamesBoyd

I have a ton of newbie questions specific to HT constuction. Unlike many of the other forums I participate here at AVS, I cannot find a primer. That said, here are my questions.

  1. Are there any basic, wiring rules of thumb? Dedicated circuits? Speaker wire runs and material? Use of coax? etc.
  2. What is RSIC and HAT Channel?
  3. What are the purposes and benfits of a stage?
  4. Are the ideal room dimensions? How about dimensions to avoid?
  5. Why do you put columns in a Home Theater, especially with the space constrained?
  6. How do you build columns? For what purposes?
  7. Are there any rules of thumb regarding lighting? (Cans? Ropes? Soffits? Ambience? Etc.)
  8. Why build a soffit? Any tips? What effect on the HT?
  9. Wood studs versus aluminum?
  10. In a given rectangular room, would you build or put angles of some kind in the corners?
  11. How do you do one of those cool, star ceilings?
  12. Any other tips/tricks?[/list=1]

    Now, I think I know some of the answers, and at the same time I am sure I am not the only one with these types of questions.

    Thank you all for the help!
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For starters no square rooms or rooms with evenly divided dimensions, like a room 8'hx16'wx24'L. Bad for low frequencies.

Columns on long walls break up reflected sound waves. Heavy, full pleated drapes on windows will do the same thing as well. As will bookcases loaded with different sized books.

Hat channels are aluminum ceiling and/or wall framing members to which sheetrock is screwed to.

I have a vaulted ceiling, it eliminates one set of parallel surfaces(floor/ceiling) which cause reflected waves.

Placing subs on corners increases the sub's output, and using multiple subs, up to 4, will smooth out the low frequencies. This greatly enlarges the "sweet spot".

Here is a white paper from Harman International about subwoofer placement.

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First of all, I'm no expert, there are plenty of them here, all knowledge I have is pretty much gleamed from them.

I'd suggest you try to break up your questions - you're asking too many at once (IMO), ergo fewer responses.

One thing I can tell you is what RSIC clips are & hat channel. RSIC clips are attached to studs or joists, because the part of the clip touching the stud (or joist) is a rubber foot, this clip has the effect of decoupling attached walls from the studs/joists, thereby reducing the transference of sound from room to other rooms. Hat channels attaches to RSIC clips - it provides a surface to screw drywall into. They work in concert, if you have one, you use the other.

Here's a picture of the products:
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Are there any basic, wiring rules of thumb? Dedicated circuits?
Follow electrical building code.

Speaker wire runs and material? Use of coax? etc.
You might want to have a glance through these

http://www.roger-russell.com/wire.htm - talks about distance vs guage vs ohms of speaker (as well as wire comparison).

http://www.avsforum.com/avs-vb/showt...hreadid=455838 - is my own recent experience with wire guage questions. I ended up using 12 guage for a 41' run.

There's a couple of threads about coax. I used RG6 to my subwoofers because that's what I found. Search for 'Beldon' and you'll find some good stuff.

What is RSIC and HAT Channel?
http://www.pac-intl.com/products.html explains it all, but you have to click around a bit. Note that HAT channel is different from RC (resilient channel), in that HAT is just a tiny support beam and is not meant to be flexable on it's own from a soundproofing point of view.

What are the purposes and benfits of a stage?
There are two purposes. #1 so that visiting parents can tell their kids not to go up on the stage, giving you an extra second to keep their sticky chocolate covered fingers away from your white screen. #2 is that when the stage is built DE style, it decouples the subwoofer on top of it from the floor a bit, which reduces coupled structural noise through the floor into the rest of the house, without suffering from non-rigid supporting structure issues (i.e. the sub does not move) on the reproduced sound.

Are the ideal room dimensions? How about dimensions to avoid?
You can use software like RPG's Room Sizer which assumes some absorbtion and does prediction differently than the spreadsheets (there's a several page explanation in the PDF linked about halfway down http://www.rpginc.com/products/roomsizer/ ). There are a couple of spreadsheets around to help with room size, just make absolutely sure they do all three: axial, tangental and oblique modes. The issue is to try to keep the modal resonance frequencies from overlaping as much as possible, particularly below 200hz where it's harder to apply in-the-room treatment. Predefined room sizes are used less and less due to an increase in computing power in the last two decades, but you can read a reasonably complete list here: http://forum.studiotips.com/viewtopic.php?p=5570

Why do you put columns in a Home Theater, especially with the space constrained?
They can be used to hide surround speakers. They can be used to reduce front reflections. They can be used to minimize holes in the wall by containing both 120V wire and receipticals and lights. You can also build membrane traps into them for LF absorbtion at a given frequency plus Q.

Why build a soffit? Any tips? What effect on the HT?
Same as columns, except they are also used for HVAC ductwork.

Wood studs versus aluminum?
Wood warps, and you can only carry a few at a time. Steel is straight and can be stored forever and won't burn and you can carry a bunch. Wood can support huge loads and is easy to screw lights and cupboards and things to. Steel needs to be reinforced whenever you want to do those things. If you're not good with steel it can rattle (for which the solution is to tear down the wall and start over). Steel offers higher STC values than similar wood construction due to its resliency, but I don't know about it's LF TL effects due to it's lower stiffness.

In a given rectangular room, would you build or put angles of some kind in the corners?
If you do this you can't use any of the predictive software for modal analysis, so all your testing will have to be done after the room is built. Angles offer more paths for first reflection, which can cause image confusion or direction shift in the sound. Angles that are full of absorbers (such as a corner trap of mineral wool) don't suffer from that, but be cognisant of RT60.

How do you do one of those cool, star ceilings?

Any other tips/tricks?
Have a glance through this: http://www.avsforum.com/avs-vb/showt...21#post4158721
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Excellent response Bob - Bless you for taking the time to answer all those questions :)
PAP - I skipped #7 lighting... :eek:

I don't think anyone would approve my current technique:

a) When the projector is on there's enough light in the room to walk around, although reading some DVD boxes is hard.

b) I know the room well enough to walk around in the pitch black

c) I hand out flashlights to visitors

A little more on the stage. I assume you are placing all of your speakers on the stage? I understand the sub being on the stage. I thought you could perfectly dampen a sub by placing it on an acoustic mat or by using super balls cut in half. ... sticky chocolate fingers... very funny.

Regarding the columns, would you please clarify how they hide the outlets, etc.? Can I do that after the theather is completed and still accomplish those goals.

Sweet link on the star ceiling...

I was hoping for a bit more on lighting a wiring. A few examples... pros and cons of using cans. Would you put one set of lights on the screen and the others around the room? I saw some people put a nice light in the middle of the room. I heard people have used coax for in-wall speaker wires... that seems strange. Is a tray ceiling with rope lighting worth it? How important is it to consider IR dimmers in the constructions stages? I saw another thread where a whole panel was being used for the HT. Each run had a "dedicated" purpose (i.e. one for the projector, one for the amp., etc.).

How much should you stuff your soffits?

Thanks again. This is getting fun!
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Would anyone care to comment on fabrics, both on the wall, in front of speakers, and on columns?

Benefits of in-wall and/or hidden bookshelf speakers versus floor-standers?

Thanks again!
This was brought up on a previous thread, but I never really saw a reply. If you wanted to choose between Green Glue and RSIC, which would be better? I recall that some were bagging the use of RSIC and going with nothing but Green Glue and double drywall.

Is this OK? Is using both redundant?

Thanks for the facts / opinions

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