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post #1 of 58 Old 06-25-2013, 06:10 PM - Thread Starter
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Hey AVSers,

 

I have been a longtime fan of the AVS site for years and all the amazing dedicated build threads have finally prompted me to pull the trigger and start my own home theater build. Armed with thirty years’ worth of articles ripped from Home Theater magazines, and a recently purchased copy of “The Home Theater Book” by Warren Peterson, I set out to design and plan a modest home theater.

 

Since none of the rooms in my house would accommodate a home theater, I am adding a small one story addition to the house. After getting the proper variances to build the addition, the dimensions I have to work with are 25’ length x 14’ width x 9’ height. The room will be built on top of a crawlspace and attach to the dining room.

 

I decided to break the room into two pieces. The first area will be about 5 feet and contain the equipment rack in the corner. Breaking the room up this way will provide a nice staging area so as not to walk straight from the dining room into the theater. It will also help keep some of the heat from the equipment out of the theater area. The theater area should be 19’ x 13’ after the room is finished.

 

I want to plan this room correctly right from the start and will focus on the proper construction of the room before deciding on equipment. There is not quite enough room for an AT screen so I will keep my build as simple as possible and have the screen mounted on the front wall.

 

Based on recommended resources from Warren’s book, I contacted Ted White and John Hile at The Soundproofing Company and will be using clips and channels with Green Glue for the walls and ceiling. The floor will be a double layer of subfloor with Green Glue.

 

For acoustics, I can’t really cover the walls with fabric due to some over enthusiastic cats that like to reach up and stretch themselves on the wall. Instead I will be purchasing some base traps and panels from GIK Acoustics based on advice from Brian Pape, who was also a recommended resource from Warren’s book.

 

For HVAC, I will be using a 1.5 ton ductless heat pump (mini-split.) Based on feedback throughout some of the threads on this forum, it seems the Home Theater space might get a little hot, even in winter and I want to be able to control the temperature independently from the rest of the house. The mini-split seems like it will do the job but I do have concerns about the air getting too stale in that environment. It seems the ductless mini-split system have an intake and output vent right on the same unit so air is not really brought in from the outside or from the rest of the house. It will just take in the air from the theater and condition (heat/cool) it appropriately based on the thermostat setting.

 

While I am reasonable confident in the plan so far, I am worried about their being some items overlooked due to the nature of my build. Most threads have builds in basements or in already completed room in part of the house. Since my build will be designed from the ground up for a home theater as part of a new addition, is there some other things I need to do or something I can take advantage of by building on a crawl space?

 

I will not be doing any of the construction myself, since I don’t know anything about construction and have hired a contractor to do all the work. My contractor hasn’t really built a dedicated Home Theater before, but he is very skilled at building additions and houses.

 

Ground was broken two weeks ago and I will be taking pictures to document the build. Below are pictures from the start of construction as well as the layout for my home theater.

 

I would greatly appreciate any and all feedback on the following:

  1. Does the overall layout look ok? Am I making the best use of the space? Are there any suggestions to optimize it?
  2. Is there anything that should be done at this stage of the construction to tailor the structure for a home theater?
  3. Will a simple ductless heat pump keep the theater space comfortable and will there be enough air flow?

 

Thanks in advance.

 

 

Proposed Design -

 

 

Proposed Design updated 6/28 -

Week 1 -

 

 


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post #2 of 58 Old 06-25-2013, 06:16 PM
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I wouldn't waste 5 ft for the equipment room, I go at 4 and leave a foot of breathing room at the back of the room, Seating in that far right seat in the back row is awfully awkward in relation to the side surround.
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post #3 of 58 Old 06-25-2013, 08:48 PM
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I think Warren's book doesn't really get into acoustics much - there are whole books on the subject that don't get to everything you would need to know. So, like BIG is saying, you're putting the back row in a zone of bad sound - the right rear seat especially.

I think you can get 6 seats in there pretty comfortably, but how you distribute the seats and optimize the listening zone's acoustics and the viewing angles may depend on how you expect to use the space. Is it just you? The ocasional party of three or four? Four kids all the time? Football party every Sunday? Without too much theory, let's allow it suffice to say that you don't want any seat to be too close to any speaker - anyone close to a speaker will be overwhelmed by its sound at the expense of the sound from other speakers. It's best for acoustics for the seats to be concentrated nearer the center of the room.

You haven't included any subwoofers in the drawing. There's plenty of time to add them, and you don't have to know exactly where they will go already (notice I refer to them in the plural? wink.gif ), though Bryan at GIK could easily help you there. We could here too, but the conversation about subs can take a while over the internet.

I would personally consider moving the dividing wall back a foot like BIG said, then raising the door and extending the riser, both wall to wall across as well as maybe farther out into the room, then look and think carefully about what that does to your viewing angles. That may just be a homework assignment I'm giving you that doesn't actually lead to improvements - I can't tell at this point if it will be to your advantage or not.

On your second question, I'd suggest you read this thread here. Digione pulled out pretty much all the stops. His thread can give you plenty of ideas - many of which you may not find worthwhile; but there are not very many builds that include dedicated structures like yours, so the opportunity doesn't come up very often.

And I don't know much about ductless A/C, so I won't say much, but I do think you're right to be concerned about exchanging air with the rest of the house - there is a possibility that the theater becomes stale and musty, I think.

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post #4 of 58 Old 06-25-2013, 09:38 PM - Thread Starter
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Thanks for the reply BIG! I am a huge fan of your work :) If only I could have a Bacon Race transported to my space. I think you are right about the extra foot and will update my design accordingly.

 

Fred, thanks for the feedback and the link to Digione's build. Looks like I have some required reading to do. Haven't had a reading assignment in many years lol. As far as the usage of my theater, 95% of it will be for just 2 people (my wife and I) which is why I jammed the last row in the corner like that. For subs, I plan on using 2 of them to even out the base response as suggested in many threads. Placement might be on the front stage, one on each side of the center channel. I would have liked to fit one in the rear of the room and one in the front but I don't know if I have the room.

 

One other thing I guess I forgot to represent was a step down coming thru the front double doors from the dining room. The home theater addition is on a crawl space which will be lower than the rest of the house. With the change in levels going down to the theater, and then having to build a riser to go back up again, I was wondering if there was a way to do something creative with the levels.


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post #5 of 58 Old 06-25-2013, 09:51 PM
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Quote:
Originally Posted by killravenx View Post

The home theater addition is on a crawl space which will be lower than the rest of the house. With the change in levels going down to the theater, and then having to build a riser to go back up again, I was wondering if there was a way to do something creative with the levels.
Just leave the floor the same as the dining room, until you get to the end of the riser. If I'm seeing this right, it just means that the ceiling in the entrance will be around 8 feet instead of 9. You can see how I'm dealing with a similar situation in my build, here.
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post #6 of 58 Old 06-26-2013, 04:20 PM
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I am also planning a new HT, and using a ductless mini-split. My HVAC engineer has spec'ed an outside air intake into the return side of the air handler. We will have vent in the equipment closet drawing air from the theatre, and and exhaust fan in the closet venting it to the outside. The thinking is that this will allow the mini-split air handler to draw in outside air. There is also a small dehumidifier in the system, since outside air here tends to be high humidity.
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post #7 of 58 Old 06-26-2013, 04:55 PM
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Quote:
Originally Posted by killravenx View Post

Since none of the rooms in my house would accommodate a home theater, I am adding a small one story addition to the house.

This is so cool - I couldn't imagine adding a room onto the house for just a home theater. The red tape involved with the wife to get that one through her approvals process would be crazy! I've also come to realize while browsing this forum that I have a different definition of "small"- the addition I just put on the back of my house has a smaller footprint and it almost doubled my living space!

Anyway, I look forward to watching this one go up!
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post #8 of 58 Old 06-27-2013, 09:41 PM - Thread Starter
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Hey Fred, thanks for the response regarding the different levels. I think I will end up using one step down to the first area and keep that the same level in the theater and just use a riser for the back seats. I think in the end it might be too complex for me to make that first area be the same level as the riser. Plus I would be worried about potential changes to the riser once the screen size and height are figured out, and if the floor was the same level I would have to adjust that too. I would also rather walk down a stair in the entrance room vs. walking down a stair in a darkened theater. On a side note, I was looking at your build thread. You sure are busy, keep up the good work! I would love to add some helpful posts to your thread but I have no expertise on any of the things you are constructing with all those cool diagrams. For all I know you could be building a rocket ship. smile.gif If comic books or video games enter the discussion, I will be the first one to reply!

 

Lebon, thx for the reply. I guess I will have to look into the whole mini-split thing further. I had hoped to just hang it on the wall and be done, but looks like more planning will be needed. I will call some more HVAC people and see what they say.

 

Hey javeryh, the approval process wasn't as hard as you'd think. I just brought up wanting a home theater every day for 20 years and next thing you know, construction has started!


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post #9 of 58 Old 06-27-2013, 10:08 PM - Thread Starter
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I updated my Proposed Design to reduce the equipment room area to 4 ft.

 

Today the foundation cinder blocks are being laid out. Based on measurements taken once the blocks were put down, it looks like I will be able to make the ceiling 9 1/2 feet. I have added an extra step from the dining room to the equipment room to account for the extra drop.

 

I also changed the back right corner of the room to reflect a bumped in section where the addition will attach to the house. I guess the back wall of the house is not a straight line and I didn't represent that in my initial drawing. I hope that corner doesn't cause any problems.


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post #10 of 58 Old 06-28-2013, 11:07 PM - Thread Starter
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Cinder block walls are up. I can almost see the home theater in that space.

 

 

Hey LeBon, I saw you mentioned possibly using a ducted mini-split in another thread. Are you still going to use that and what brand/model would it be? Would it be possible to use a regular mini-split in the theater and hook up a return vent to my existing central air? That way air gets pulled from the room whenever the ac/heat is on in the rest of the house and I wouldnt have to worry so much about it getting stale in the theater.


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post #11 of 58 Old 06-29-2013, 12:20 AM
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My guy spec'ed a Mitsubishi Mr. Slim 12000 BTU/hr unit, I have used the regular units in computer rooms, but they are a little noisy. A return to another system messes up the pressure balance of the room. I don't think that will work right, In a "new build" like this, I would do the ductless -- I don't think it costs all that much more. It is similar to my situation, where I am doing a major remodel -- pretty much stripping it down to the studs.
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post #12 of 58 Old 06-29-2013, 07:28 AM
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You may not be happy with the Mr. Slim. You will find that even though it is rated at 12K cooling it will not deliver that unless the fan is on high and that will be noticeably noisy. There are many flavors of these units as well and be damn sure, if you go ahead, to get the 21 + SEER unit and not the lesser. I would also get the heat pump unit and not straight cooling as it is only ~ $100 more. A lot of these HVAC contractors don't actually know very much about this. IN fact most don't. An installed unit should run about $2,100 including permit.

Secondly, check with your power company for a Federally sponsored rebate on the units. The Mitsubishi units will typically qualify ... your contractor may be clueless however. Don't ask him, as the power company yourself. Contractors typically jack the cost up and then show you the rebate so it looks like you're getting a deal - you are not - they are. In FL the rebate for a unit under 1 ton is $750 and it has to be a minimum of 18 SEER ... makes it quite affordable.

Introducing outside air and exhausting via a minisplit as one poster suggests is a VERY bad idea and he has obviously received some bad advice from a less than knowledgeable contractor. His system will be worthless in the end, and in Calif the humidity is not an issue at all. Normal home humidity is desirable at 40% and CA will typically be less.

Not sure why you have concluded that "A return to another system messes up the pressure balance of the room", but that is essentially incorrect. If it were me I would tie into the existing system with a normal supply and return. If you system is short of capacity or you just want more cooling/heating capacity I would then add a minisplit exclusively for the space.

"Your guy" has also incorrectly sized the unit. A 12K unit is too big for the space and I would use the 9K unit instead. Big is NOT better in all cases. You will find that the unit will not run long enough, due to oversize, and as a consequence it will not remove the moisture from the air. I would shop around and try to find someone who actually knows what they are doing for the HVAC work. Your main system will maintain the room and recirculate the air for you. That lessens the load on the supplemental unit and it will work as designed. Natural leakage and infiltration in a residential environment will give the home enough air exchanges to keep it comfortable. You will find in your space that the bulk of your cooling demand will be from warm bodies - not equipment.

Looks like you may have a crawl space. If so, a much better choice is a packaged system that would sit outside the building and run your ducts through the wall under the floor. The packaged system has the air-handler and condenser in one outside unit ready for ducts to attach. You can then duct them up in your eq. room and make a very nice system that will be silent. With that system you could also introduce a bit of outside air in the return and create a positive pressure in the space. That would eliminate drafts and dust, etc from entering. You would only need a small 4" round duct with a damper on it to give you perhaps 50-75 CFM of outside air. You need ~ 15 CFM per person for air quality to maintain a good level of freshness and not cost a lot to condition. I would base it on "normal" room occupancy ... not maximum since it cost $$ to condition outside air.

I only offer this as a suggestion. I also have two of the Mitsubishi units in my home.

Good luck on your build ... I am building this fall.
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post #13 of 58 Old 06-29-2013, 02:29 PM
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1. Why do you say that introducing outside air via a ductless minisplit is a vary bad idea?

2. My understanding is that airfow into and out of a room should be balanced. Where is the makup air coming from, if you have a return to a system outside the "sealed" theatre room? I don't think I want a negative pressure in the theatre room.

3. "My guy" is not a HVAC contractor, he is a mechanical engineering firm. I guess I have faith that they know how to size a unit.

4. I thought I mentioned somewhere that there is also a small dehumidifier in my system -- maybe that was on another thread. Humidity where I live is routinely in the 80%+ range.

5. The rest of my house has no air conditioning, since we really don't need it here. So I feel that I definitely need an AC unit for the theatre. I am using the heat pump version of the Mr. Slim.
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post #14 of 58 Old 06-29-2013, 02:49 PM
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It will be good to have an old pro from HVAC industry on the forum, especially someone from the design side. We have good representation for acoustics, soundproofing, electrical, lighting, and electronics... but no one that's an expert in HVAC. Are you a mechanical engineer?
Quote:
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Not sure why you have concluded that "A return to another system messes up the pressure balance of the room", but that is essentially incorrect. If it were me I would tie into the existing system with a normal supply and return. If you system is short of capacity or you just want more cooling/heating capacity I would then add a minisplit exclusively for the space.

Pretty sure he meant having a return to another system (without a supply back into the room from the other system). That would be a problem in a room that's built as air tight as possible, no?
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Introducing outside air and exhausting via a minisplit as one poster suggests is a VERY bad idea and he has obviously received some bad advice from a less than knowledgeable contractor. His system will be worthless in the end, and in Calif the humidity is not an issue at all. Normal home humidity is desirable at 40% and CA will typically be less.

So what is the best way to introduce fresh air into the room? Is the answer the same for minisplit & conventional forced air?

 

 

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post #15 of 58 Old 06-29-2013, 03:38 PM
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Quote:
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You will find that even though it is rated at 12K cooling it will not deliver that unless the fan is on high and that will be noticeably noisy.
Quote:
Originally Posted by rexlan View Post

"Your guy" has also incorrectly sized the unit. A 12K unit is too big for the space and I would use the 9K unit instead. Big is NOT better in all cases. You will find that the unit will not run long enough, due to oversize, and as a consequence it will not remove the moisture from the air.

I wanted to put those 2 statements together and ask if it's possible that the 12k was spec'd so they could get 9k worth of cooling while running the system on the ultra low / sleep setting?
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I would shop around and try to find someone who actually knows what they are doing for the HVAC work. Your main system will maintain the room and recirculate the air for you. That lessens the load on the supplemental unit and it will work as designed. Natural leakage and infiltration in a residential environment will give the home enough air exchanges to keep it comfortable. You will find in your space that the bulk of your cooling demand will be from warm bodies - not equipment.

Don't take this as an attack, because we're glad to have any HVAC expertise here, but is it possible you're applying your own experience with commercial structures and residential in general, without considering the specific needs of HT? Most HT rooms will not have windows. Doors use special seals along each edge to make them as air tight as possible. Minimal penetrations are made in walls that compose the room's "shell". All penetrations & seams are caulked. I'm not sure a HT space can be treated the same as the rest of a home.

As far as heat from equipment, unless you know what equipment Lebon is using, isn't it a bit presumptuous to say cooling demand won't come from the equipment? My first 2 projectors used 475w xenon bulbs and sat in the room with me. Even with my HVAC system set to cool continuously (which froze everyone else in the house), I would be sweating by the end of a movie just from the projector + amplifier heat. That wasn't even a high end setup. Some of the highend projectors need 10k - 20k btu of cooling just for the projector. Mini-splits first became popular on this forum as a dedicated cooling solution for the equipment room itself. More recently, people have begun to consider them for cooling people.

 

 

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post #16 of 58 Old 06-29-2013, 09:19 PM - Thread Starter
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Thanks everyone for the replies. Maybe the solution can be found by breaking down the HVAC needs for the Home Theater separately.

 

1) I need to heat and cool the Theater separately from the rest of the house. I was told by the HVAC guy that even with a separate zone I would not be able to turn the AC on in one zone and the heat in the other. So I think using a mini-split in the theater is the most effective way to heat/cool it independently.

 

2) I need to provide some way to circulate the air in the Theater area so it doesn't get stale. The mini-split does not exchange the air with the rest of the house so I will need a different solution for that.

 

What would be a simple solution to accomplish #2? Keep in mind I have a crawlspace under the theater so I should be able to run some ducts in that area if need be. Maybe two dead vents, one to pull air out of the theater into the adjacent equipment room and another to push air from that same space into the theater? Although if I have the heat on in the rest of the house in the winter, wouldn't pushing air from there make the Theater hotter? This is all very confusing, it seems like there should be some way to accomplish both #1 and #2 mentioned above.

 

Again any insight you guys can provide would be greatly appreciated.


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post #17 of 58 Old 06-29-2013, 10:58 PM
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I believe that a Ducted mini-split can be used to bring in fresh air on the return side of the air handler. Then you use an exhaust fan to remove an equal amount of air somewhere (in my case, from the equipment closet). I agree that you may need to adjust the humidity, depending on your local conditions.
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post #18 of 58 Old 06-30-2013, 08:12 AM
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The Fujitsu ceiling cassette mini splits have a fresh air intake option. I'd guess other brands have the option too.


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post #19 of 58 Old 06-30-2013, 08:20 AM
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Quote:
Originally Posted by rabident View Post

It will be good to have an old pro from HVAC industry on the forum, especially someone from the design side. We have good representation for acoustics, soundproofing, electrical, lighting, and electronics... but no one that's an expert in HVAC. Are you a mechanical engineer?

Ditto!

I've talked to a couple of AC contractors and have been completely underwhelmed with their knowledge. They give wildly different "opinions" about how much cooling capacity I need. None has done anything more than pull a number out of their @$$. My ex neighbor is a mechanical engineer - I'm going to employ him to run some calculations to at least give me a starting point based on science.

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post #20 of 58 Old 06-30-2013, 12:09 PM
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No attack taken.

I am a licensed Mechanical Engineer (PE) and designed HVAC systems for the better part of 40 years including banks, hotels, vaults, hospitals, clinics and schools, offices, as well as pump stations and electrical generation stations. I elected to not explore the credentials because I was trying to be helpful, not start a pissing contest, and it seldom adds to the conversation. Commercial/residential makes no difference other than scale which requires different methods of delivery. All commercial spaces require the introduction (usually recovery as well) of OTA for the occupants. In a tight HT the air should have some exchange as it will indeed get stale and possibly unsafe if it is as tight ans you folks are indicating ... I don't know. The HVAC principals are the same except different occupancies require different factors such as fresh air, air changes and filtration. Since we are on it I also have licenses as an electrical administrator, master plumber and I am a licensed FL real estate Broker - but I am retired! So we can get that out of the way.

If OP has a ME that he "thinks" is competent then that is wonderful and I am sure he can get it resolved. However, based on the information at hand he is not. Just because you are a ME it does not mean you know anything whatsoever about HVAC.

The Mitsubishi mini's are based on newer inverter technology to obtain their efficiency. The "air handler" is the thing on the wall (or ceiling) inside. You CAN NOT introduce outside air to it unless some idiot puts a hole in the back of it and a hole through the wall to do so! The "return is on top of the unit and the discharge is in the front ... it simply circulates air over the coil and drops the temperature about 18-20° in the process. Running the fan on low with an over sized unit is foolish and will likely result in stale air and short lived equipment. You need the temperature differential across the coil to condense the water vapor from the air (dehumidify) when it then drained to the outside by gravity. This unit MUST be installed on an outside wall.

Petew has the right idea if you want the ceiling register type air handler. Mitsubishi also makes one and F or M are the only unity you should consider. Others are difficult to get part for but people will sell you anything. Difficulties with ceiling types in these applications; noise, they have a condensate pump and you will have this "thing" in your otherwise dark ceiling.

I have offered the best solution already. Use a packaged unit ~ 1.5 ton and run it on a lower fan speed. Duct from the unit straight into the crawl space then up in the corner of the eq. room. Depending on final design you could run a continuous register down one side in a soffit and the return on the other side. The system would be silent, efficient and invisible. Or you can put in floor registers for both the returns and the supply. The down side is that I beleive 1.5 ton is as small a unit as you can find = 18,000 BTU.

The package unit uses ducts. You run a supply trunk and a return trunk. You NEVER just blow/suck air from the crawl space.

I di not realize this house had no central air ... never seen one as I can recall that was built since the mid 70's.

@Petew ... you do not need a ME. On average you will need ~ 1 ton of cooling for 600 s.f. of space. For a home theater I would add some capacity and lean to the 450 s.f. spec. If you oversize too much the unit will short cycle and that is not desirable. I already indicated that you need ~15 CFC of OTA per person. You can calculate that for you room volume and that will tell you how many air changes per hour you need. Typically that will be about 8-10, or less with very good filtration. BTW ... good filtration is NOT possible with a mini-split. It is with the packaged unit that uses filters and that uses the return filter grills.. In the alternate, you can go on-line and find a heat calculator free like this ... just look around a little. Heat Calc. Single room load calcs are very simple.

@rabident .... OP shows his equipment in another room so there is no assumption made about it other than the fact that it is not in the room under discussion. 475 watts is only 1,600 BTU. I would be quite surprised to see your HT that requires a 10K-20K BTU cooling device for the projector ... I don't think the commercial theaters require that and we could probably light up the old drive-in movie pretty easy with it. We should not try to outdo things to the e^3 power. In a well designed box for teh overhead with a few holes I thing a 4" CPU fan moving ~ 80 CFM is more than adequate to cool the unit.

A person gives off about 300 BTU/hr. watching TV unless it is a hottie getting naked then maybe 400 BTU/hr. ... LOL.

In the final I think OP will have some difficult getting this done right because it is an after-the-fact project in a home without central air. Might be a good time to upgrade teh home or a room or two with a nicer heat pump unit and a little duct work. All cost $$$

Good luck on your build ... I am gone.
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post #21 of 58 Old 06-30-2013, 03:10 PM
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Originally Posted by rexlan View Post

@rabident .... OP shows his equipment in another room so there is no assumption made about it other than the fact that it is not in the room under discussion. 475 watts is only 1,600 BTU. I would be quite surprised to see your HT that requires a 10K-20K BTU cooling device for the projector ... I don't think the commercial theaters require that and we could probably light up the old drive-in movie pretty easy with it. We should not try to outdo things to the e^3 power. In a well designed box for teh overhead with a few holes I thing a 4" CPU fan moving ~ 80 CFM is more than adequate to cool the unit.

I don't want to derail the thread, so last post from me as well. The Barco 23B used in this theater has specs listed here which are 19,000btu for the projector with 4k lamp. I don't think Chris is using the 4k so listed half that for the minimum range.

Wolfgang is using 2 x Barco 4k 32B here. He runs 2 projectors in parallel for 3D. Specs for each projector are here and listed at 30,000btu per projector.

There are others. The raw lumen output looks high, but enthusiasts trade off high light output for better contrast ratio using combinations of high contrast lenses and aperture plates fitted into the light path. Many will dump half their light output for CR that can only really be appreciated in the blackness of a HT without code restrictions requiring lighted exit signs, stairways, etc. Calibration and bulb aging will reduce peak light output. Watching 3D movies also significantly reduce the brightness each eye sees.

My questions was more general about the best way to bring in fresh air to a theater room. That question comes up a lot. It's something OP is considering, LeBon is working on, and I took a run at.

 

 

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post #22 of 58 Old 06-30-2013, 04:04 PM - Thread Starter
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No attack taken.

I am a licensed Mechanical Engineer (PE) and designed HVAC systems for the better part of 40 years including banks, hotels, vaults, hospitals, clinics and schools, offices, as well as pump stations and electrical generation stations. I elected to not explore the credentials because I was trying to be helpful, not start a pissing contest, and it seldom adds to the conversation. Commercial/residential makes no difference other than scale which requires different methods of delivery. All commercial spaces require the introduction (usually recovery as well) of OTA for the occupants. In a tight HT the air should have some exchange as it will indeed get stale and possibly unsafe if it is as tight ans you folks are indicating ... I don't know. The HVAC principals are the same except different occupancies require different factors such as fresh air, air changes and filtration. Since we are on it I also have licenses as an electrical administrator, master plumber and I am a licensed FL real estate Broker - but I am retired! So we can get that out of the way.

If OP has a ME that he "thinks" is competent then that is wonderful and I am sure he can get it resolved. However, based on the information at hand he is not. Just because you are a ME it does not mean you know anything whatsoever about HVAC.

The Mitsubishi mini's are based on newer inverter technology to obtain their efficiency. The "air handler" is the thing on the wall (or ceiling) inside. You CAN NOT introduce outside air to it unless some idiot puts a hole in the back of it and a hole through the wall to do so! The "return is on top of the unit and the discharge is in the front ... it simply circulates air over the coil and drops the temperature about 18-20° in the process. Running the fan on low with an over sized unit is foolish and will likely result in stale air and short lived equipment. You need the temperature differential across the coil to condense the water vapor from the air (dehumidify) when it then drained to the outside by gravity. This unit MUST be installed on an outside wall.

Petew has the right idea if you want the ceiling register type air handler. Mitsubishi also makes one and F or M are the only unity you should consider. Others are difficult to get part for but people will sell you anything. Difficulties with ceiling types in these applications; noise, they have a condensate pump and you will have this "thing" in your otherwise dark ceiling.

I have offered the best solution already. Use a packaged unit ~ 1.5 ton and run it on a lower fan speed. Duct from the unit straight into the crawl space then up in the corner of the eq. room. Depending on final design you could run a continuous register down one side in a soffit and the return on the other side. The system would be silent, efficient and invisible. Or you can put in floor registers for both the returns and the supply. The down side is that I beleive 1.5 ton is as small a unit as you can find = 18,000 BTU.

The package unit uses ducts. You run a supply trunk and a return trunk. You NEVER just blow/suck air from the crawl space.

I di not realize this house had no central air ... never seen one as I can recall that was built since the mid 70's.

@Petew ... you do not need a ME. On average you will need ~ 1 ton of cooling for 600 s.f. of space. For a home theater I would add some capacity and lean to the 450 s.f. spec. If you oversize too much the unit will short cycle and that is not desirable. I already indicated that you need ~15 CFC of OTA per person. You can calculate that for you room volume and that will tell you how many air changes per hour you need. Typically that will be about 8-10, or less with very good filtration. BTW ... good filtration is NOT possible with a mini-split. It is with the packaged unit that uses filters and that uses the return filter grills.. In the alternate, you can go on-line and find a heat calculator free like this ... just look around a little. Heat Calc. Single room load calcs are very simple.

@rabident .... OP shows his equipment in another room so there is no assumption made about it other than the fact that it is not in the room under discussion. 475 watts is only 1,600 BTU. I would be quite surprised to see your HT that requires a 10K-20K BTU cooling device for the projector ... I don't think the commercial theaters require that and we could probably light up the old drive-in movie pretty easy with it. We should not try to outdo things to the e^3 power. In a well designed box for teh overhead with a few holes I thing a 4" CPU fan moving ~ 80 CFM is more than adequate to cool the unit.

A person gives off about 300 BTU/hr. watching TV unless it is a hottie getting naked then maybe 400 BTU/hr. ... LOL.

In the final I think OP will have some difficult getting this done right because it is an after-the-fact project in a home without central air. Might be a good time to upgrade teh home or a room or two with a nicer heat pump unit and a little duct work. All cost $$$

Good luck on your build ... I am gone.

 

Hey rexlen, thanks for your post. I think I will explore the packaged solution. If I go this route, should I run suplies and returns to both the home theater area and the 4' x 13' equipment area? The equipment area is next to my dining room and I expect the double french doors to be open all the time. It is possible that the packaged system would be on cool in the winter to cool down the theater and the equipment area might get hot air from the rest of the house when the heat is on as the same time. Would that be a problem?

 

The layout for the theater can be seen in the top post.

 

If you don't want to post anymore on this topic would it be ok if I sent you a pm?

 

Thanks.


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post #23 of 58 Old 07-01-2013, 01:02 PM
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Your time is short if you want to do work under the floor while it is very simple.

If it were mine I would Probably put the (9,000 BTU Mitsubishi mini-split in - it has to be on an outside wall. Then add 3 decent size grills (14 x 20) in the back wall into the eq. room near the floor. They make those grills as a filter unit also and here is a real good place to buy stuff ... http://www.atlantasupply.com/register-grille.htm It will make no difference in sound unless you are so pure you need an oscilloscope to detect the frequency shift of the sound ..... IMO people get much too carried away with themselves, but that's just me. NO light will come through the grills if the are low and the vent slits are angled down. You can also mount a couple of small computer fans inside the wall to push air into the room ... it only take a small amount and you will never hear them. You will need to pre-wire the cavity and line it and you will need a wall wart from Wal Mark since they are 12Vdc.

Set the Mini on auto and let it do its own thing. It will automatically cycle the fan speed to maintain the temperature and they are very good at that. Downside is that these units NEVER turn off the fan, but on their lowest speed they are very hard to hear ... I think ~ 17dBm whisper stuff. This will give you a god job overall with a very efficient unit. This is the right one MSZ-GE09NA-8 - MSY-GE09NA. This unit is qualified for a Federal Tax rebate of $300 and probably your local power company has an additional program. You will need a contractor to install them and it will require a 15 Amp (#14 wire) 220V local disconnect.

If you want a better solution (recommended if you are really going to use the room) I would put a packaged unit outside. It contains the air-handler all in one handy unit. Downside is the size, smallest being ~ 1.5 Ton ... a lot more than you need. Additionally, the smaller units are not real efficient compared to what is available these days. I would recommend a Trane XB13C 9model 4WCC3018) This is a std. 13 SEER heat pump unit and about as good as you will do. DO NOT buy a junker for cost, you will regret it in 5 years. Stick with Trane, Lennox or equal. This unit should give you trouble free service for 10-15 years, cost $2K. The upside - you can install the entire system yourself. All it will require is a 220v 30 Amp (#8 wire) circuit with a local disconnect. There is no plumbing, ie., packaged. This unit puts out 675 CFM on low and 1100 on high. Set it up for low, but the duct size is OK for high and you do not want to under size the ducts because as the velocity increases so doe the noise. That is also why you want 7" boots and not 6".

I would put a 14" flex supply line as shown and about half way down the run towards the screen you can reduce it to 12". Same for the return side. I'd keep it simple with just two sizes. These are flex ducts, real easy to use. You will need a takeoff w/damper for each register and a 3 1/4 x 10 x 7" boot for the floor register. Put them as shown. Google the duct and be sure to install it with the correct straps and no sags. You will need some 7" flex duct as well to connect the boots to the trunk line.

If you stub a line and put one floor register in the dinning room that will serve as your fresh air. It will draw air from the house. Use the damper to minimize the flow as you do not need a lot of air. You can also do the same thing outside on the return side but it is more complicated ... and cost money to condition the air.

Unless you have one hell of a lot of equipment I don't thing your eq. room offers any issues. If you don't want the heat in there simple close the French doors while in use! If the house does not want cooling and the doors are open then some will go to your dining room - close the doors. This system does have enough capacity that you might consider running an additional lateral to a bedroom or, family/TV room. if you have access under the floor. All it cost is the small $$ for the additional ducts which can be a 7" line for return and supply.

Here is your drawing: I just did a quick line in Illustrator so you can see the concept. That give you all the information you need to make a decision with at this point. Keep it simple and trade that for a tiny bit of noise or go deluxe which always adds cost and complexity.

I'll add today ... I said use #8 wire for the 30 amp circuit because I do not know the run distance to your main panel and you don't want a voltage sag when the compressor starts. A #10 is the proper size for a 30 Amp circuit if it is not too long of a run.

Additionally, same for the mini split. It requires a 15 amp circuit - if it were mine I would run a 20 amp and use #12 wire. Then you will never have a power issue, cost adder is minimal.

The flex duct is an R6 insulated duct. Your crawl space can not be exposed to the outside and I assume your plumbing is in there too.
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post #24 of 58 Old 07-02-2013, 04:26 AM
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Might I suggest that you do the back wall semi-acoustically transparent to help dampen the long room dimension standing waves? I've got one that about a foot and a half thick stuffed with insulation with 50% opening/diffusion on each side.

Under construction: the Larch theater
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^This is a very interesting idea. For a variety of technical reasons, professionals may not recommend it, but I would consider it or something similar.

By way of background, let me elaborate a little. Sound reflects from walls, obviously. Some sound will be transmitted through walls. Some sound will be absorbed or dissipated within walls. The amount and frequency rages over which any of that happens is strongly linked to the wall construction, and is variable based on wall mass, rigidity, size, and materials. It would be exceedingly difficult to predict that with any accuracy, even with good modeling, due to variations in actual construction - things like the number of screws in a sheet of drywall.

When a pro designs a critical listening space, he wants all the walls to behave the same way - what's known as equal impedance. This allows all the reflected sound to have the same character in terms of phase and intensity at each range of frequencies. If a space is constructed with all six surfaces having equal impedance, precise calibration is simpler and has better results.

So why would we throw away that benefit? Nightlord is suggesting that the low-frequency sound that would bounce off the rear wall if it were built normally could be absorbed if the wall were built lightly. This is true, and could provide a very specific and useful benefit in taming the modal interactions of standing waves. Again, the precise benefit is very difficult to predict, even with powerful purpose built software, but we can fairly safely say that lighter construction will decease the portion of low frequency sound that is reflected, accomplishing the goal of minimizing the longitudinal modal resonance. Then, we need to consider what happens to that sound energy. Nightlord's recommendation to add fiberglass insulation points to a solution, at least a partial one: we try to absorb the energy that is transmitted through the lightly constructed wall. This is important, obviously, because that energy will be bothersome when it's allowed to enter the structure of the main house. So, the cost of this approach is forgoing the ideal of equal impedance, and the risk of noise, especially low frequency noise, contaminating the house. And then there's the extra space occupied by the fiberglass.

There is a continuum of techniques that could be employed here, from using thinner, lighter drywall, to wider stud spacing, to fabric and fiberglass partitions without hard surfaces at all.
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Therefore you include the equipment room as part of the whole room wall wise, and you'll have your equal impedance, you just introduce the dividing light wall as an absobent/diffusor inside it. Handling both spaces as one with regards to transmission of noice to the rest of the house solves that issue too.

Now, drawback can be that any noisy equipment might penetrate this kind of wall easier and distrub the cinema of course.

Btw, my cinema's (in-room) acoustical design is by a pro, so I don't intend to take any credit what so ever for the concept.

Under construction: the Larch theater
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to fabric and fiberglass partitions without hard surfaces at all.
...not a good idea due to the very real potential of over absorption of the high/mid frequencies.

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...not a good idea due to the very real potential of over absorption of the high/mid frequencies.

That's why a large portion of the inner surface in the room needs to be hard. In my setup it's 50% of the surface ( 2x2:s with 2" spacing ).

Under construction: the Larch theater
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In my setup it's 50% of the surface ( 2x2:s with 2" spacing ).
Wow. No real diffusion and scattering over a very narrow bandwidth.

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Wow. No real diffusion and scattering over a very narrow bandwidth.

Well, that's what the doctor ordered for my room. wink.gif And it worked fantastically well too, had I just not had to tear most of the room down to please the neightbours.

Under construction: the Larch theater
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