Need HELP! with JVC X30 - Screen size, placement and PJ placement - AVS Forum
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post #1 of 8 Old 10-21-2012, 11:49 AM - Thread Starter
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And yes I have seen the "Official JVC X30..." thread, and it is over 300 pages and almost 9,500 posts right now and I was getting kind of lost, so I thought I would just ask my questions here.

I have never owned a projector, so after settling on a Mits HC4000 over the last two years and never getting around to pulling the trigger for various reasons, (summer, wakeboarding, busy with work, backyard projects – Ok so my wife wanted her kitchen finished…) I finally today pulled the trigger at our local Big Box store and on the 20th, I will pick up my new JVC DLAX30.

The X30 will be used for;
  1. Movies – 2D as 3D just doesn’t excite me right now
  2. Sports
  3. Inputs to an AV receiver – Just bought a Marantz SR7007
  4. Dish Network STB ~20% of the time
  5. PS3 (or some other standalone BD player) 75% of the time
  6. An HTPC – yet to be built, but have been looking at cases, dual video cards and motherboard/processors
  7. AV receiver output through an appx. 25’ to 30’ HDMI cable to the X30
  8. In a 20’ wide x 22’ deep HT room
  9. That has windows (soon to be with thick dark curtains)
  10. Used mostly at night



I still need to:
  • Pick and get a screen, I want a 16:9 120” ceiling mount (not recessed) motorized screen
  • Or should I go to 2.35:1?
  • What gain? Looking at the Elite Cinetension2s
  • Screen color/type (white,grey etc)?
  • Length of ceiling mount
  • Suggestions on what and where to buy?


With a 120” 16:9 screen,
  • What height off the floor should I shoot for? Dimension “D” in my drawing below
  • I have a coffered ceiling that drops down about a foot, the projector will be mounted to the upper ceiling and the screen will be mounted the lower ceiling height, what distance from;
  • Dimension “A1” upper ceiling to the center of the lens
  • Dimension “A” center of lens to top of screen
  • Dimension “B” upper ceiling to the top of the screen
  • Dimension “C” lower ceiling to the top of the screen





HT Section - JVC X3.pdf 20k .pdf file
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post #2 of 8 Old 10-21-2012, 12:33 PM
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There is a sticky thread that contains a calculator for determining your riser height, but it can also be used to determine how high you need to mount your screen so the people in the back row have an unobstructed view. The main link in the sticky doesn't work, but try this:
http://calc.xn--f5a.net/

Do you already have a riser built for your back row? If so, you kind of need to work backwards through the calculator, plugging in trial and error screen heights (distance from floor to bottom of screen) until it spits out your current riser height. This will give you measurement "D" in your sketch.

Once you have selected a screen size and determined measurement "D", your top of screen height is a given, so ignore B & C in your drawing. If you plan on using the JVC's motorized zoom and lens memory features to move between aspect ratios, you will need to mount the projector's lens so that it falls within the screen area (not above as you currently show in your elevation). So A1 will need to be long enough so the lens is at least level with or slightly below the top of the screen.

Once that is all done, give it a quick check to make sure your eyeballs in the front row fall somewhere in the bottom 1/3 of the screen and the viewing angle to the top edge of the screen does not exceed 15 degrees.

A few questions:

1. Will your speakers be to the sides and above/below the screen or are you looking for an acoustically transparent screen that will allow you to hide all of your speakers behind the screen?
2. What percentage of your overall viewing will be movies? This should point you in the right direction regarding 16:9 vs. 2.35:1.
3. What made you decide on ceiling mount vs. fixed frame on the wall?
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post #3 of 8 Old 10-21-2012, 06:19 PM - Thread Starter
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Quote:
Originally Posted by Spaceman View Post

...Do you already have a riser built for your back row? If so, you kind of need to work backwards through the calculator, plugging in trial and error screen heights (distance from floor to bottom of screen) until it spits out your current riser height...

I have not yet built the rear seating riser and am not really that interested in it (yet) as that will come later and I will be able to "field measure" what I want. I already raised the power outlets along that portion of the room to allow for up to a 12" riser.

Quote:
Once you have selected a screen size and determined measurement "D", your top of screen height is a given, so ignore B & C in your drawing. If you plan on using the JVC's motorized zoom and lens memory features to move between aspect ratios, you will need to mount the projector's lens so that it falls within the screen area (not above as you currently show in your elevation). So A1 will need to be long enough so the lens is at least level with or slightly below the top of the screen.
Once that is all done, give it a quick check to make sure your eyeballs in the front row fall somewhere in the bottom 1/3 of the screen and the viewing angle to the top edge of the screen does not exceed 15 degrees.[\quote]

After talking to my wife, and looking at a set of windows that currently fill that wall, I now want a 2.35:1 138" screen and have come up with the revised layout shown below. Again, kind of ignoring the rear seating.
But sitting in our HT chairs, the dimensions seem to work well.
Quote:
A few questions:
1. Will your speakers be to the sides and above/below the screen or are you looking for an acoustically transparent screen that will allow you to hide all of your speakers behind the screen?
2. What percentage of your overall viewing will be movies? This should point you in the right direction regarding 16:9 vs. 2.35:1.
3. What made you decide on ceiling mount vs. fixed frame on the wall?

My answers;
  1. The speakers will be to the side, so I don't need a perferated screen
  2. Mostly BD movies and that is why I now want a 2.35 - plus I need to one-up my buddy's 80" Sharp panel tv!
  3. I am using a ceiling mount screen due to the existing windows, that I wish I hadn't put in for the HT, but would have looked funny from the front "money shot" of the home's exgterior.


So I guess now my question is;
  1. Will the 2.35:1 138" Elite CineTension 2 work with this layout? I beleive the screen gain is 1.1
  2. Do I mount the PJ's lens at the top of the screen?


Thanks for any help, Eric.

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post #4 of 8 Old 10-22-2012, 09:28 PM
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Some questions I have

1. Why wouldn't you want to determine the dimensions of the riser now? Seating placement is critical at this stage. You can't determine anything until you decide where the seats must go for best low frequency results.

2. Why wouldn't you want a perforated screen? Biology kinda takes over on this one regarding comb filtering of speaker placement and the way our ears are designed.

3. What about noise and heat? Projectors put out lots of heat and lots of noise...especially the JVC units in high lamp mode where I prefer it.

Just a few thoughts. Yes, you place the lens at the top of the screen.

Shawn Byrne
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HAA Design Certified -THX Certified Professional

Design-Video & Audio Calibration Information

The original Pro Theater Layout
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post #5 of 8 Old 10-23-2012, 10:20 AM - Thread Starter
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Quote:
Originally Posted by SierraMikeBravo View Post

Some questions I have
1. Why wouldn't you want to determine the dimensions of the riser now? Seating placement is critical at this stage. You can't determine anything until you decide where the seats must go for best low frequency results.

Because that is not where I will be sitting and we havent even purchased or decided on the seats that will go there. They may be addtional HT chairs or my wife wants a couple of day beds.

Quote:
2. Why wouldn't you want a perforated screen? Biology kinda takes over on this one regarding comb filtering of speaker placement and the way our ears are designed.

Just dont need it with the speakers in the corner of the room. There is a large (screen size) window that the screen will come down and cover. The speakers are to the side of those windows.


Quote:
3. What about noise and heat? Projectors put out lots of heat and lots of noise...especially the JVC units in high lamp mode where I prefer it.
Just a few thoughts. Yes, you place the lens at the top of the screen.

Heat; the room is very well insulated and cooled - the house has two 5-ton HVAC zoned units.
Noise; Isn't that what the Marantz SR7007 is for?

So now I am trying to read through all the conficting posts on whether or not the X30 and a 2.35:1 138" Elite CineTension 2 with 1.1 gain will work with this layout? Or if the projector should be closer

Eric.
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post #6 of 8 Old 10-23-2012, 10:38 AM
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For me, the purpose of a perforated (Acoustically Transparent) screen is to be able to place the center channel speaker so that the dialogue (virtually all of which comes from the center channel) comes from the screen, not above or below it.

Be careful about your HVAC thinkng. Don't assume that the theatre is the same as other rooms in the house. It is a closed space with heat-generating sources (equipment and people), and will tend to be hot even on cold days.
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post #7 of 8 Old 10-23-2012, 05:21 PM
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The questions were really rhetorical. They were asked to get you thinking. Placing a speaker below the screen is the worst possible thing you can do due to the design of our ears. There is a reason commercial movie theaters place speakers behind the screen. Further, the noise of the projector as well as background noise in the room can be as much as 60 dB....yes even in the quietest of neighborhoods. Insulation in the house is basically irrelevant. Movie sound tracks go down to 22 dB. If you have a 60 dB noise floor, well, you've just lost almost 40 dB of soundtrack due to the background noise...including the projector. The reason for a quiet room is to increase dynamic range. Ever play the volume game? Kids screaming in the background or lawn mower running, or your wife talking on the phone? You increase the volume so you can hear...most often the dialogue. ou're marantz will overcome this to a point, but as soon as that explosion happens it'll cause damage to your speakers, and or your wife screaming at you to turn it down. This is ALL due to background noise...including the projector. You'll have to calculate the amount of heat in your room. You can start by multiplying the maximum number of people you plan on being in the room by 500 btu per person. That's just where you start. Not the final value. You should determine now what type of seating you'll have and where it will be placed. Deciding later on is a definite no-no. Planning it that way will only lead to a room that is used very little down the road. These are the things that were meant to generate thought by the questions I asked. Hope it helps!

Shawn Byrne
Erskine Group
HAA Design Certified -THX Certified Professional

Design-Video & Audio Calibration Information

The original Pro Theater Layout
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post #8 of 8 Old 10-23-2012, 05:57 PM - Thread Starter
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Quote:
Originally Posted by SierraMikeBravo View Post

Placing a speaker below the screen is the worst possible thing you can do due to the design of our ears. There is a reason commercial movie theaters place speakers behind the screen.

I dont have a choice on this one really as there is a window that the speaker will sit at the bottom of. I built the room prior to doing any research or thinking of screen/speaker placement. Is it optimal?, obviously not but it is a comprimise that comes with the room, a front yard, a wife and what I have to deal with.

Quote:
Further, the noise of the projector as well as background noise in the room can be as much as 60 dB....yes even in the quietest of neighborhoods. Insulation in the house is basically irrelevant. Movie sound tracks go down to 22 dB. If you have a 60 dB noise floor, well, you've just lost almost 40 dB of soundtrack due to the background noise...including the projector... This is ALL due to background noise...including the projector.

My god! I hope that new projector doesnt put out anywhere close to that much dbs!

Quote:
You'll have to calculate the amount of heat in your room. You can start by multiplying the maximum number of people you plan on being in the room by 500 btu per person. That's just where you start. Not the final value. You should determine now what type of seating you'll have and where it will be placed. Deciding later on is a definite no-no. Planning it that way will only lead to a room that is used very little down the road..

My point earlier was that the rear seats are what will not be used, me and my boys will be sitting about 12' from the screen and my wife will be the one yelling!!

This home theatre will be constantly changing as one of the next projects will be a set of DIY speakers, and I definately have not even begun on that design. It may not be ideal, but I certainly do not want to wait another three years to start enjoying it.

What I really need help with at this point is the screen and the PJ placement.

Thanks, Eric.
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