My DIY theater build thread: 'Grove Theatre' - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 63 Old 05-26-2020, 04:24 PM - Thread Starter
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My theater build thread: 'Corona Theatre'

Considering the entirety of this HT build is looking like it will be completed during (and thanks to) the COVID19 situation causing me to be working from home for 4 months I think it's only appropriate to update the name of this theatre to 'The Corona Theatre.' I'll find a nice minimalist crown design to paint somewhere in the room. It also works with the purple walls and the fact that my household is bilingual.

Anyway, it's been some time since my last HT build, and even longer since my first build using knowledge from this forum many years ago! But this time it's for real as I finally got myself a blank canvas (1800 sqft unfinished basement). I'll update this post here if anyone wants to chip in thoughts/tips or observations I may have missed. I do have a few questions that may warrant separate threads since I haven't finalized all of my gear decisions yet, but I'll summarize them below.

I've been framing, plumbing and wiring this basement for the past 3 months so I've had plenty of time to read in the forum in the interim and much has changed in the AV world since my last build! Shout out to three individuals in particular who have posted a wealth of great information over the years that has proven helpful for many of my design decisions: @BIGmouthinDC @MississippiMan @LTD02

The Basics
• Theatre is 22'10" long, 14’4" wide and has 9' ceilings with a 7'7" height tray on the perimeter enclosing HVAC, structural beams, etc. I framed single non-staggered stud walls to maximize space.
• I used 450 IB-1 clips, 145 pieces of 10-foot hat channel, double 5/8" drywall, green glue, acoustic caulk is going in the cracks and outlet gaps, and MLV rolled in the gap between bottom plate and floor plate (It's a colorado thing). R20 stuffed in the ceiling throughout the theatre and open adjacent media hallway. (8) recessed LEDs are in airtight 4" cans.
• Adjacent hallway will house all physical media (150 square feet of wall shelving) and is soundproofed to the same spec as the main room
• 2x3' equipment closet in the left wall that will house a wall-mount rack
• I ran four circuits to the theatre off a 100A subpanel in the basement:
  1. 20A serving only the four corners of the room (prewire for active subwoofers)
  2. 20A home run in the closet for one passive sub amp
  3. 20A circuit serving another receptacle in the closet for the second sub amp as well as two projector duplex receptacles, and the riser receptacles, and
  4. 15A circuit serving a third duplex in the closet and the remaining duplex outlets in the theatre itself.

All lighting is on a separate circuit. I put a whole-home arrestor in the main service panel. Putting the four corners on a single 20A will end up being wasted effort since my plan has since switched from powered subs to passive subs with rackmount amps
• Will likely need to build a hush box as I recently discovered that due to living at 6,300ft I have to run the JVC in high altitude mode which is quite loud (58db) even on low lamp mode
• Rear riser at 14", will attempt to set this up as a bass trap. Front stage will be built at ~12" height
• 2 rows of 3 seats, 4-seat bartop behind back row
• Front minimal screen wall will be ~14” out from the finished wall and covered in black velvet
• 150-155” scope screen. Will shoot some images on the wall once drywall is in and narrow this down precisely. Aiming for money seat at 2x screen height
• Room is totally light controlled. We are rocking over the window in the back of the room, and will have blackout curtain on the inside of the door. Planning to mount the pj at 17' (4" beyond it's minimum distance for a 155" screen). Should be getting about 15fL on the screen. HDR is probably a no-go.
• Finish will likely be black carpet and deep purple walls, with black velvet on screen wall and on walls near front of theatre
• The last piece to go in will likely be a star ceiling on 2" foam
• Usage 85% movies, 10% music, 5% games

Areas Prewired
• (3) LCRs (14/4 speaker wire)
• (4) surrounds (12/2)
• (6) Atmos speakers (12/2) – middle row won’t be used initially
• (2) front wides (12/2) - won't be used until Denon's 13-channel amps get cheaper
• (6) subwoofer cables (14/4) - The four corners, with double cables for each of the front corners
• (4) subwoofer cables with RCA cable (one per corner)
• (4) Riser step lighting boxes
• (5) Riser receptacles (on a 20A circuit)
• Adjacent to front right seat I am building out a small "armrest" out of 1x6 wood that will sit just below the height of the actual armrest of the seat. Within that stub out are prewires for (2) HDMI, (1) Toslink, (1) Headphone jack, (1) Component Video, (1) RCA A/V, and (2) USB jacks.
• (2) projector ceiling outlets on a 20A circuit, at 15’ and 18’
• (2) projector CAT6 cables
• (7) additional empty 2.5” conduits with pull string: one behind the screen, three in the ceiling joists (one earmarked for star ceiling fiber), one at the projector, one by the left surround speaker, and one where the riser will meet the wall by the A/V closet

Gear (in italics is not yet purchased but what I'm leaning towards)
• Projector: JVC X790R
• HDMI: Ruipro 8GBPS Fiber (15’)
• Screen: DIY 155” scope Seymour Center Stage XD AT screen
Receiver: Denon X6700H
• Amp: Marantz MM7055 (LCRs only)

• Amp: Denon AVR-3803 (repurposed pre-outs as amplification for Atmos only)
• Subs: (4) LaVoce 21" (SAN214.50)
• Sub amps: (2) Behringer NX6000D
Tuning: MiniDSP 2x4HD, UMIK-1, REW
• LCRs: Titan 615LX
• Surrounds: Klipsch R-5650-S II
• Surround backs: Klipsch R-3650-W II

• Atmos: RSL C34E
Door: Simpson 4948 solid hickory 1.75” exterior door with IG glass
• Seating: Palliser Techno or Flicks (2 rows of 3)

• Rack: 29RU Middle Atlantic Slim 5
Media: Panasonic DP-UB9000, Apple TV 4k, nVidia Shield, Playstation 5, and will be building an updated HTPC
• Raspberry Pi runs emulators, MAME arcade controls will be integrated into rear bartop
• Chief RPMA281 projector mount + Peerless EXT002 short drop tube (had to chop one end of this off since only one side was threaded). This allowed me to thread the Chief mount all the way into the ceiling mount plate.


Undecided Items
1) Subwoofer configuration - I am leaning towards shallow subs all around - such as one of the shallow 18's in the links below, as I could then put these behind the screen wall. For the rear I am considering building them into the riser to save more space, but realize this will be more difficult. Or I could fit three shallow 18s behind the screen wall and ditch rear subs altogether...
- https://www.avsforum.com/forum/155-d...l#post38691441
- https://imgur.com/a/KWFxYLu
- https://www.avsforum.com/forum/155-d...l#post55871030
- https://www.avsforum.com/forum/155-d...ld-thread.html
- https://www.avsforum.com/forum/155-d...you-ltd02.html
UPDATE: I went with four 21s in custom cabs, noted in a later post in this thread.

2) Screen Size - Will be a scope screen (probably 2.40:1), but in my original design there was no screen wall so I was sitting 12' from the screen - this put the money seat 1 screen width from a 155" diagonal screen (143" wide). However, building the screen wall out 14" will put me at 136" - incidentally this is a around 2.25x screen height, as the screen will be 60" tall. This seems potentially too close, but I do like immersion. I'll know more once I have drywall up and can test some sizes but am I right in thinking that 'on paper' 2x screen height is a commonly used distance?
UPDATE: Went with Seymour XD material as planned, sized for 155" 2.40:1 screen.

3) Room Modes - I believe I'm correct in assuming that as long as the screen wall I build is acoustically transparent that all of my seating distances that were carefully planned to eliminate nulls will still be good since the subs will "see" the room dimensions as being where the actual drywall is, not where the screen wall is? Front row is 54% of room length and row two is 82% back, pretty close to the ideal 55/80% marks. Width wise, I am placing the prime seat at 45% of room width (left aisle will be wider than right aisle as seats are shifted a few inches right). I am hoping that the combination of 2" foam on the ceiling (star ceiling) plus a riser acting as a bass trap will mean I need very little or no other room treatments except for possibly treating first reflections on the side walls...

Pictures of progress so far are below. Comments and suggestions on the above, or otherwise, are welcome.
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post #2 of 63 Old 05-27-2020, 08:31 AM
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That's an awesome space and the framing is looking good. Personally I would wait until the Titans or 1099's are back in stock but that's just me and probably overkill - still if you have three Titans across the front it'll be epic. Any reason why you aren't going DIY for surrounds also? The HTM's make great surround speakers...

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post #3 of 63 Old 05-27-2020, 09:11 AM - Thread Starter
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Originally Posted by p3bham View Post
That's an awesome space and the framing is looking good. Personally I would wait until the Titans or 1099's are back in stock but that's just me and probably overkill - still if you have three Titans across the front it'll be epic. Any reason why you aren't going DIY for surrounds also? The HTM's make great surround speakers...
It's funny you should say that - I spent the next several hours after my OP reasearching and measuring and came to a better solution entirely (see attached).
When the Titan 15's are restocked I am going to use three of those, and instead of putting subs in the four corners I'm going to attempt to put all four at the 1/4 points of the front wall behind a 14" screen wall. There are several shallow cabinet options out there that will allow this. In the attached diagram the four cabinets are 11 cuft each (before displacement for bracing and woofer).

I just need to know port dimensions and locations. I was thinking of porting the bottom two on the bottom edge of the front baffle by using AT fabric on the face of the stage step area. Then porting the top two on the sides so the ports fire into the empty space above the center channel or above the L/Rs.

I suspect also that these cabinet sizes may allow me to use four 21s instead of four 18s. Anyone care to take a shot at two ported build diagrams for these? @LTD02 ?

To your question about DIY surrounds, there are two reasons I'm not doing that: 1) Aesthetics. In walls look cleaner and are less intrusive in a room that will already only have 32" of walking space on the aisle where the surrounds are, and 2) The right side surround by virtue of rack and stud placement, cannot be mounted directly beside the MLP, it is going to be at about 120 degrees behind, pretty much right between the two rows of seats, so I like the Klipsch 5650 because it has two tweeters each aimed in opposing directions so one will shoot at each row.
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post #4 of 63 Old 05-27-2020, 02:27 PM
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Sounds like a cool build. I'm going with all DIYSG audio system in my theater including two Stonehenge's behind the screen.

Currently building the Quarterdeck Club
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post #5 of 63 Old 05-27-2020, 02:35 PM
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When you mount your projector mount you don't want to drive lag bolts into the plywood you mounted to the joists, that will defeat the decoupling. Instead substitute a layer of 5/8 plywood for drywall as the first layer hung on the channels in that location
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post #6 of 63 Old 05-27-2020, 02:39 PM
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this


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post #7 of 63 Old 05-27-2020, 02:44 PM
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This is going to be an incredible space... your acoustic isolation efforts with green glue and MLV will go a long way!

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post #8 of 63 Old 05-27-2020, 03:01 PM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post
When you mount your projector mount you don't want to drive lag bolts into the plywood you mounted to the joists, that will defeat the decoupling. Instead substitute a layer of 5/8 plywood for drywall as the first layer hung on the channels in that location
Big you are the man. I knew I had missed something somewhere and you would be the one to catch it.
By the way if anyone is looking at this picture and noticing another error I made in the sound isolation efforts - I built back boxes for the Atmos speakers early this morning after a 6:30am Lowes run and got them hung before the drywallers got here at 8. Fortunately they came without the proper length drywall screws for the HT so the ceiling is still blank leaving me just enough time to implement the suggestion you made above!
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post #9 of 63 Old 05-27-2020, 03:06 PM
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don't see the putty pads
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post #10 of 63 Old 05-27-2020, 04:32 PM - Thread Starter
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Ted White recommended acoustic caulk around all of the outlets
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post #11 of 63 Old 05-27-2020, 04:34 PM
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I think you misunderstood him, it is not instead of, it is in addition to.
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post #12 of 63 Old 05-27-2020, 04:34 PM - Thread Starter
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I think you misunderstood him, it is not instead of, it is in addition too.
That's odd - I wonder why he didn't sell me those too

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post #13 of 63 Old 05-27-2020, 04:37 PM - Thread Starter
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Also odd - the installation manual SoundproofingCo provided makes no mention of puddy pads, only to seal all outlets with caulk.
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post #14 of 63 Old 05-27-2020, 04:42 PM
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post #15 of 63 Old 05-27-2020, 04:52 PM - Thread Starter
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Darn, suppose it is too late now, acoustic caulk will have to do. Fortunately there are only two receptacles on the ceiling and that is primarily where I'm concerned about sound exiting from and entering into the theatre. The walls are adjacent to rooms that will rarely be occupied at the same time as the theatre. Considering I'd never even heard of green glue 4 months ago I am overall pretty happy with the extent of my soundproofing efforts.

Thanks again Jeff for jumping in with observations and feedback. I will update the thread this weekend with completed drywall pics, and hopefully a mounted pj if my RPMA gets here this week.
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post #16 of 63 Old 05-27-2020, 04:55 PM
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You can actually put the putty inside the critical boxes, not advised but you can do it if there is room.
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post #17 of 63 Old 05-27-2020, 04:58 PM - Thread Starter
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You can actually put the putty inside the critical boxes, not advised but you can do it, "after inspection"
Interesting, I will look into doing that then.

With the COVID19 situation inspections here are virtual and are lasting approximately 2 minutes. I think I passed my framing inspection and my plumbing and electric rough inspections in less than 5 minutes combined, so I could put them in now if only there was a place that sold puddy pads locally - I doubt it, as I'd never heard of them before jumping down this rabbit hole despite being on this forum for two decades
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post #18 of 63 Old 05-27-2020, 05:08 PM
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Actually the electrical inspection is done. Next time all the covers will be on so do what you want.
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post #19 of 63 Old 05-27-2020, 07:34 PM
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Quote:
Originally Posted by cyan View Post

...

I just need to know port dimensions and locations. I was thinking of porting the bottom two on the bottom edge of the front baffle by using AT fabric on the face of the stage step area. Then porting the top two on the sides so the ports fire into the empty space above the center channel or above the L/Rs.

I suspect also that these cabinet sizes may allow me to use four 21s instead of four 18s. Anyone care to take a shot at two ported build diagrams for these? @LTD02 ?

...
joe built the first set of such subs that i am aware of. it looks like you and he have about the same amount of space. it also looks like avs wiped out all his pics.

https://www.avsforum.com/forum/155-d...sub-build.html

i'd suggest the lavoce 21's for drivers. they have all the low end of um18's but much better/more efficient mid-bass. they do cost more though.

i'd also suggest firing all the cabs out the sides. that seems to work fine and will keep your design down to just one plan. if you have dimensions, i can suggest port configuration.

another one in the same spirit:

https://www.avsforum.com/forum/155-d...4-drivers.html

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post #20 of 63 Old 05-27-2020, 07:51 PM - Thread Starter
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if you have dimensions, i can suggest port configuration.
Thanks John! I will check those two threads when I get back to a computer. For dimensions on my sub box idea they’re very similar to what you came up with a while back in the Skinny Marty thread, mine would just be a little taller: 38.5” wide, 44” tall and 12.5” deep. I could go slightly deeper but am concerned about some of the high excursion drivers possibly hitting the screen wall so in shooting for 12.5” depth. Single baffle.

I’ve played around a bit today in WinISD and am getting some weird port length dimensions for a 4x11 port so I must be doing something wrong.
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post #21 of 63 Old 05-27-2020, 08:26 PM
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Is there a reason the LCRs are 14/4 wires vs 12/2 everywhere else?

Just wondering if I should be planning the same thing!


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post #22 of 63 Old 05-27-2020, 08:42 PM
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for this one, instead of a port brace down the center of the port, you may wish to double up the bottom if possible.

bracing not shown. doesn't really matter how, just make sure it is well braced.

these are about 7.25 or so cubic feet net and tuned to roughly 16.5-17.0 hz depending on how much volume is reduced by bracing.

4.5" tall port keeps air velocity under control with SAN214.50 driver and 99 volts of amp power (nx style amp).

first port resonance is on the low side around 115 hz or so. but with your mains, an 80hz cross should be fine, so the low resonance shouldn't matter.









if you can find some straight 2x3's, bracing the baffle in this way will allow four driver mounting screws into the 2x3's, which will be super strong.



it is kind of tough to say what the output will be in your room, but these model at 127db at 20hz, extension into the mid teens and that's before room gain and baffle wall gain.

i think they will be 'loud enough'. :-)

importantly, ensure that they are somehow tied to the wall so they can't fall over. these cabs are pretty narrow so won't have the stability of some of the other hulks.
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post #23 of 63 Old 05-27-2020, 09:09 PM - Thread Starter
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Quote:
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Is there a reason the LCRs are 14/4 wires vs 12/2 everywhere else?

Just wondering if I should be planning the same thing!


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Nothing super important really.
Monoprice 12/2 CL2 was sold out everywhere but still had 14/4 (I wired the 12/2 stuff weeks later when it was restocked)

14/4 doubled up to a single speaker gets me two 11 gauge wires which is a bit better than two 12 gauge wires, so it was a case of “well it can’t HURT so why not”

Also gives me the option of using the wire that’s already installed to run two separate speakers so if mid-left and mid-Right ever become prevalent in home audio formats I am set with existing wiring.
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post #24 of 63 Old 05-27-2020, 09:12 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
i think they will be 'loud enough
Thanks John, I really appreciate it. I’m about halfway through the second thread you linked above. Inspiring! I have drywallers coming at 6:30am so I’m going to bed and will dig into what you provided here tomorrow and try and make Sophie’s choice on the two drivers you recommended 😉

One question I do have that jumps out immediately is: would using a port brace in this design significantly change output? I actually can’t double the bottom as the 44” height takes me all the way to the soffit with two of these stacked together.

Last edited by cyan; 05-27-2020 at 09:17 PM.
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post #25 of 63 Old 05-28-2020, 07:12 AM - Thread Starter
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Hey @LTD02 ,
Sorry to be a bother but I just noticed that the xmax on the LaVoce driver is less than an inch (less than half than the xmax of the UXL18 I was trying to account for when I initially measured out my available box space). So this means I could probably get away with a 13.5" depth cabinet instead of 12.5". I assume this would change the port dimensions appreciably? (and may also be a worthwhile change to the build for output reasons)?

Also - when you model in WinISD am I correct in assuming that for port length calculations to be correct you include the port volume in the total box volume you key into the 'Box' tab? When I model the 12.5" deep enclosure you posted without including port volume (7.25 ft^3 at 16.5 hz) it is telling me the 4.5x11" port in your drawing needs to be 61.49" long
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post #26 of 63 Old 05-28-2020, 05:51 PM
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cab volume is net of everything.

slot ports get a port height added to the effective length for tuning purposes, so if winisd tells you 48" and the port is 4" tall, then build the port 44" long as measured down the centerline.

1 inch makes your cabs a lot better. approx. 8 cubic feet net. tuning of 16.5-17hz or so.

i added a traditional slot port brace. as a result the ports aren't growing as fast as the cab, so the port can be a hair shorter, which will increase the first port resonance by hair (to around 120hz). this is a good thing.





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post #27 of 63 Old 05-29-2020, 08:30 AM - Thread Starter
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A special shout out to @EndersShadow ! I must say you have outstanding timing. Pointing out in the other thread that I may not have enough dedicated 20A circuits for four 21" subs on the very morning that the hombres are hanging drywall in that part of the basement. A sudden realization that I had some leftover 12ga Romex, a quick run downstairs and voila - one more 20A circuit in the closet! This guy literally started hanging this area as soon as I got done wiring up the additional receptacle. Now I've got enough juice for 7200watts just to the amps. Hopefully more than enough.
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post #28 of 63 Old 06-01-2020, 05:11 PM - Thread Starter
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Drywall is now finished (pictures to follow) and in doing some testing on the room for sound transmission I realize that while the double drywall and GG was a great solution, I am getting a ton of noise through the HVAC ducts. The noise floor of the theatre is 35db. Playing music in the upstairs bedroom at 80db I am getting 55 of those decibels in the theatre, almost entirely through the HVAC supply vent. Covering the three vents in the bedroom with thick pillows dropped that number to 45db.

I see there are options out there for wrapping the ducts with liner but these all seem to either be for the outside of the duct, or they require fastening with screws inside the duct, both of which are impossible now that all duct work is covered in drywall. Is there a product that can be applied inside the ducts with adhesive rather than fasteners?

I am also building a baffle/hush box for the projector that will enclose this vent fully on four sides, and will help reduce some of the sound transmission but it's clear I've got to treat these supply vents upstairs in some way, as removing or covering them isn't an option.
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post #29 of 63 Old 06-03-2020, 07:12 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
cab volume is net of everything.

slot ports get a port height added to the effective length for tuning purposes, so if winisd tells you 48" and the port is 4" tall, then build the port 44" long as measured down the centerline.

1 inch makes your cabs a lot better. approx. 8 cubic feet net. tuning of 16.5-17hz or so.

i added a traditional slot port brace. as a result the ports aren't growing as fast as the cab, so the port can be a hair shorter, which will increase the first port resonance by hair (to around 120hz). this is a good thing.
John, I grabbed the MDF for these yesterday, hoping to get them built and hit you up to order drivers in the next couple weeks. My only remaining question is what's your recommendation on filling? One pillow? Two? Line the entire thing with something?
Thanks

And hey kids, if anyone ever says you can't fit 225 square feet of MDF in a Subaru with two 12s in the back you can call bull**** on them.
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post #30 of 63 Old 06-03-2020, 07:24 AM
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that is 1260 lbs, depending on the model right at the weight capacity. Hope your suspension survived the trip!
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