Advice: DIY 7.5.4 Theater Design Setup - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 11-30-2019, 04:23 PM - Thread Starter
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DIY Dedicated Home Theater - 7.5(20).4 build

The Story:

I told my wife I was going to spend $10k on a home theater and she made fun of me for about two weeks. So I dragged her to Audio Advice and the Best Buy Magnolia center to let her experience some really high quality speakers and projector setups. She loved it but was still not ok with spending so much money. So the next week we went to the movies and the theater just happen to be the worst one I have ever been in. It was in the back of the building, it hadn't been updated in 15-20 yrs, all the seats squeaked when you moved, it smelled, you could constantly hear the theater next to it, and there were a lot of loud people. It was an overall horrible experience. As we were leaving I said $10k for a home theater doesn't look so bad now does it? That is when we agreed we could convert our bonus room into a home theater. I have spent the last 6 months researching things and have finally started buying things. I am going the DIY route with the speakers.

Goal:

Replace my 1080p 65" TV with damaged screen and soundbar with fully immersive home theater that I will never want to leave!

Current Plan:

4K Projector with 125" Diagonal Screen - 16:9 ratio - 7.5.4 Surround Sound - Going the DIY route

Usage:

-90% Home Theater / 10% Music - Almost all the content will be streamed from Netflix, Disney+, Hulu, Prime Video, or HBO Now. Currently using a Roku Premiere but I am about to buy a Nvidia Shield Pro 2019.
-Normally 1-2 people viewing at a time but max would be 4 if friends come over.

Room:

- Completely light controlled since the windows will be blacked out
-304 sq. ft. - 2443 Cubic ft.
-Already wired room with Ethernet
-Lowish attic above but still fully accessible
-One 15 Amp breaker but no way to easily run another line without a lot of drywall work. If needed I can do.
-The couch can be moved around some depending on speaker placement and screen size. I usually like a full view experience since it feels more immersive.
-I was thinking of mounting the projector at 14' from where the screen would be and sitting 10' from the screen.
-The boxes, tubs, pictures, bed, ceiling fan, and bookcases are being removed. I might put one bookcase on the other side of the room or angle them in the corners.
-I do not have to worry about disturbing the neighbors.



Purchased:
Projector - Epson Home Cinema 5050UB
Receiver - Denon AVR-X4500H
LCR - 3x DIYSG 1099
Subwoofer - 20x JBL 12" GX1200

Need to Purchase:
Side - 4x Volt 10s
Atmos - 4x Volt 10s
Sub Amp - Recommendations?
Ch10/11 Amp - Recommendations?
Speaker Wire - Belden 5T00UP 10 AWG 2C Speaker Wire CL2 250 ft.
Plugs - Banana Plugs
Video - Fiber HDMI Cable 50ft
Paint - Recommendation?
Sound Proofing - Recommendation?
Screen - Recommendation?
Mount - Recommendation?

Any recommendations on what I should do or buy is highly welcomed!


To-Do List:
-Remove excess stuff from room
-Replace ceiling fan with flush mount light
-Determine exact speaker placement
-Wire room
-Paint walls, ceiling, trim, doors, & A/C registers black
-Blackout Windows
-Prepare Garage for speaker building




Current Situation
-The things I have purchased will be arriving this week
-I will most likely be making the speaker boxes from scratch. I have never done this before but I am somewhat confident in my woodworking skills and already have the tools.
-I will need help with the box designs.




Current Situation/Questions about the subwoofers:
-I have 20 of the 10" JBL subs
-I was thinking about building 5 sub boxes - One for each corner of the room and one to sit the center channel on. I don't know the best configuration.

-Is there a lower and upper limit to how many I can put in one physical box?
-Is there a limit on how big the box can be?
-Do I want the space inside the box to be open between all the speakers or closed off so each speaker has their own sealed section?
-Is there an upper and lower limit to how big that inside space should be?
-Does it matter what configuration I make the box? (Tall and narrow vs short and wide vs not a rectangle at all)
-What exactly does the SLAP do?
-If I am supposed to have 1x SLAP per 2x Speakers does it matter where I put the SLAPs and where I put the speakers?
-How many of the speakers/boxes should I have wired together to go to say 1xNX3000 or 1xNX6000 or any other recommended AMP?
-I don't need the D model of these amps because I will have the miniDSPs right?
-I understand that a DSP is needed for EQ'ing the speakers but I have never used one so which of those miniDSP models should I get?
-With the amount of air being moved or pressurized in my room from the large surface area of 20 of these subwoofers and my other speakers will that case pressurization issues with my ears or wind noise issues?





Current Situation/Questions about the surrounds/atmos:
-My current plan is to buy 8 Volt 10s but they are currently out of stock. I emailed Erich and he stated he has ordered the parts for more.
-If there is a different speaker I should be buying for these that are timber matched please let me know.
-I was planning on ordering the angled flatpack boxes for each of these speakers and mounting them flat on the wall/ceiling. This would allow me to angle them at the main listening position. If any of these should not be the angled boxes please let me know.







Pictures:







Messy Room:









Messy Room:



Messy Room:











Side Speaker Placement - Boxes underneath are just to hold up test box






Side Speaker Placement - Boxes underneath are just to hold up test box



Atmos Speaker Placement:






Atmos Speaker Placement:


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Last edited by Cotton1; 11-30-2019 at 07:53 PM.
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post #2 of 7 Old 12-02-2019, 02:00 PM
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You're off to a good start here, and that room will be absolutely rocking when you're done. I wanted to ask what you felt the Nvidia Shield would provide over and above the Roku Premiere. I had planned to go with a Shield for our basement theatre, but the Roku I have (Premiere? Plus? I can't remember) has been pretty flawless so far, and I may just stick with something similar when the time comes.
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post #3 of 7 Old 12-02-2019, 05:08 PM - Thread Starter
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@OJ Bartley I have the Roku Premiere currently and I will be upgrading to the Nvidia Shield simply due to the fact that I want to have a wired connection instead of a wireless connection. I also want the ability to stream/display my PC games to my projector which is on the other side of the house.

I am currently stuck on which AMPs and MiniDSP to buy.
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post #4 of 7 Old 12-03-2019, 10:02 PM - Thread Starter
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I have a question about power requirements. So am building 5 subwoofer boxes and each box will have four 12" subwoofers in it. They are 4 ohm and 250 watts RMS. I am going to wire 2 set in series and then those sets in parallel to keep the impedance at 4 ohm. I used a calculator to determine that if I sit 10 ft away, have a target SPL of 100 dB, with 90dB sensitivity and want 3 dB of headroom I will need 185 watts of power. I read that the amp I power it with should be rated for twice that required power to help eliminate clipping for the 4 ohm impedance that my speakers are wired.
Now my question is do I need an amp that will provide 370 watts of power (185 * 2) to the box or do I need an amp that will provide 185 required power * 2 * 4 speakers = 1480 watts?

https://www.jbl.com/on/demandware.st...al_English.pdf
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post #5 of 7 Old 12-05-2019, 07:43 PM - Thread Starter
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Test image with a cat. Also some of the things that have arrived. Those 4 big boxes are all full of the jbl speakers.
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post #6 of 7 Old 12-06-2019, 11:06 AM
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So, what kind of screen are you looking at and what kind of budget? I love my Stewart Cima Neve but previously had a Silver Ticket screen that was good when the budget was a bit tight.
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post #7 of 7 Old 12-06-2019, 05:03 PM
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Quote:
Originally Posted by Cotton1 View Post
I have a question about power requirements. So am building 5 subwoofer boxes and each box will have four 12" subwoofers in it. They are 4 ohm and 250 watts RMS. I am going to wire 2 set in series and then those sets in parallel to keep the impedance at 4 ohm. I used a calculator to determine that if I sit 10 ft away, have a target SPL of 100 dB, with 90dB sensitivity and want 3 dB of headroom I will need 185 watts of power. I read that the amp I power it with should be rated for twice that required power to help eliminate clipping for the 4 ohm impedance that my speakers are wired.
Now my question is do I need an amp that will provide 370 watts of power (185 * 2) to the box or do I need an amp that will provide 185 required power * 2 * 4 speakers = 1480 watts?

https://www.jbl.com/on/demandware.st...al_English.pdf
I am powering 9 of the JBL's with an Inuke 3000D in a "magic square" setup I am copying from this thread..https://www.avsforum.com/forum/155-d...fer-array.html So far there is plenty of power but I am still getting them dialed in. Theoretically you could wire 16 of them to a 4 ohm load in a larger magic square and power them all from a 6000 and place a 4 woofer box in each corner but it would limit your ability to EQ each corner separately. You may get more input in the main JBL thread https://www.avsforum.com/forum/155-d...y-bestbuy.html
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