DIY HT room

hello everyone.
it's been a while.
well more than a while. it's been years. yeah. that long.

well i've been busy. with life. doing something else that's not HT.
built this. DIY. because, why not?




as you can see, it's not yet complete. a work in progress.

and that has this in its floorplan:


this long MCO has allowed me to give the HT room a bit more time to work on.
so this is a placeholder to post the progress so that it's not lost to oblivion.

it'll be a while. because again, it's DIY.
DIY HT room. because, why not?

this is the planned room setup. quad (or more) subs at each corner.
curved 120" screen.
2 rows of seat. elevated rear row using riser.

room size is 16'x20'
side wall is double walled with an air gap to reduce LFE from affecting the adjacent guest room.
other walls are single brick.

still have 2 thin windows at the side facing the porch area because it's not a fully cinema room.
it's main purpose is as a study room.

well that's the plan anyways

this is a simulated and measured room response at my old house.

this is the simulated response:


this is the actual measured response:


and this is the simulated and measured response overlapped with each other:


while it doesn't perfectly predict the response, there's some correlation there for the peaks and valleys.
it does give some insight if there's gonna be huge problems to be solved later from the room size, speaker and subs placement and ceiling height.

that is from the old house, old setup at the living room.

this is the floorplan.


HT room is designed to be out and away from living quarters, bedroom and family area. minimized distubance
so best location is in front of the car porch, next to the guest living room.
adjacent to the guest room since guest room is gonna be empty most of the time.

if there's guests around, don't blast the sub. unless the guest is a likewise HT lover.

the HT room length is pretty much fixed at 20'
longer than 20' gonna eat into the guest living room. wife will get mad.
and at 20' is just nice to fit in 2 cars at the front porch with ample room to open doors and all. that box there at the porch is a measured car dimension 

so HT room width can be varied to get the best sub response.
time for some simulation.

Excellant work. Wish I had spase like that!!! Enjoy your hard work when done.

room length is fixed at 20'
actual (useable) inner room length is 19' 3", since it's converted to mm then back to feet. minus wall size.

ceiling height i don't want it too high as to avoid requiring too many subs to pressurize the room.
wife wants the room to be a bit higher to make it airy and less claustrophobic to be in.
the rest of the house have 11'-13' high ceiling, some area is as high as 26' with sloped ceiling. she wants it like the rest of the house.

lower ceiling = less subs, less power to pressurize the room.
higher ceiling = more subs, higher power needed to pressurize the room, less ULF to be felt. harder to reach single digit frequencies.

this is 19' 3" with 15' wide. quad subs located at the expected room position.
9' high ceiling.


at the listening positions got some huge nulls that affects the main position, left position, right position and rear position.
and these nulls happen at the worst possible frequency which is at around 100hz and 140hz, right smack in the crossover transition frequency.

from experience these kind of nulls at the xover transition frequency from sub to speaker is really hard to compensate electronically.
it'll mess around with the phase timing and hard to solve with electronic correction since it'll affect both the speaker and sub simultaneously.
hard to get the phasing and and sound response to play nice with each other.

so i try to avoid this kind of response.
15' wide with 9' high ceiling is a no no.

panda wrote:Excellant work. Wish I had spase like that!!! Enjoy your hard work when done.

thanks. when it's done, which is dunno when. 

at 9' high ceiling i've simulated a few room width.

simulation:

going above 14.5' flattens the predicted room response.
15' and 15.5' has the most predictable response with 15.5 being the best.

also simulated the response at 9.5' high ceiling.

simulation:

the same outcome.
14' has that jagged response above 80hz. and huge null at ~150hz
the best is at 15.5' wide

and simulated response at 10' high ceiling.

simulation:

again, the same outlook.
15.5' has the best predicted response at most of the listening positions.
very predictable response and i think easier to correct electronically later on.

15.5' effective (indoor useable width), plus the wall thickness so room size is decided at 16' wide.

so the room was built according to these dimension:
16'x20' with a planned ceiling height of 10'
effective inside dimension is a bit lower because of wall size.


and this particular wall is doubled walled with an air gap.
not double bricked, not double thickness; but double walled.




the 2 inch air gap goes all the way down and you could see the floor from the top.
the plan is to reduce disturbance especially from ULF/LFE from the subs to the adjacent guest bedroom.

using double thickness or double brick have an added mass advantage, but sound could still travel through vibration across the brick.
an air gap could reduce the sound penetration power considerably by having it go through 3 different material brick -> air -> brick.

maybe it'll work. maybe not.
but since it's DIY, well why not? hey it rhymes

in the future can measure the difference in sound pressure since the air gap is only at 1 side wall.
and visually it's not noticeable.

sorry been a while.
i've been busy. it's early season and busy time for farmers.


other than doing all these DIY audio/ht stuffs i'm also doing DIY rice.

Spoiler:

anyways not to bore you guys with agriculture stuffs


this is how the HT room used to look like.
filled with stuffs and turned into a store room while waiting for construction to finish.

i thought of a few possible ceiling designs.
the easiest is always to have a flat ceiling. but where's the fun in that? right?

so considered to have the ceiling staggered in steps from front to back. like so..



having a rising ceiling would help in distributing the soundwave from the front and avoid any standing wave issues.
like having a natural diffuser at the top. don't need to hang any additional diffusers since the wave won't be reflected to the same point.

flat ceiling in staggered steps also allow overhead speakers to point straight downward, allowing for predictable response.
and light distribution from the downlights at the top is also even across the entire room.
all the good stuffs.

but gonna be a real pain to build.
the support trusses are gonna be quite complicated and more welding joins that i need to consider.

yes.
welding. DIY. welding. overhead.
on a hanging structure 10 feet from the floor.
probably welding on a scaffolding to a hanging structure.

gonna be fun.
sigh

You clearly put in a lot of effort into your audio/HT experience!

Happy to see this and keep it up!

Hi-Fi 4 Sale wrote:You clearly put in a lot of effort into your audio/HT experience!

Happy to see this and keep it up!

thanks.
it's DIY. so it takes a while.

after further design with the staggered ceiling, the support structures are like so:


looks quite complicated since the ceiling is spread to 3 steps:

• 6' in the front
  
• 8' in the middle
  
• 6' at the back
  

for a total span of 20'
and that 3 steps need to be supported since the joins are gonna be a source of vibration and squeaking during bass hit.

also need to think about the ceiling joins especially here:

where the ceiling panels meet, one isn't going to be supported well enough and will vibrate with huge bass hits.
need to add an additional support trusses to screw the panels into.

wow. so much complication.
unnecessary complication.

after discussing among friends and showing the complicated staggered design and my concerns about it,
the staggered ceiling idea had to be scrapped.

too complicated.
too many support trusses.
too hard to keep silent and vibration free.

a flat ceiling had to be adopted.
wait... what?

a friend pointed out that all those staggered ceiling benefit could be had with a simple slope added to a flat ceiling.
just that the lights will be at an angle, which can be corrected by using a hanging light or an angled base.
and overhead speakers at an angle shouldn't be much of an issue after calibration.

a flat, sloped ceiling at an angle retains most of the staggered ceiling benefit, and avoid all the complication.

well why didn't i think of that?

so here's the new plan:


yeah.
flat. with a slight inclination towards the back.
i've tried marking different inclinations on the wall. 1 feet drop is too much.
6 inch is better looking. not as noticeable.

after all, it's supposed to be dual function also as a study room.
so 10.5' at the front, 11' at the back.

but man it's so flat and uninteresting and obvious and cliché.
nope. too unimaginative and dull. no fun.

since i'm a fun DIY adventure guy, challenge accepted..

this is the proposed ceiling trusses:


wow that's a lot of trusses for just a simple, flat plaster ceiling, no?
because it's not gonna be using normal plaster ceiling.
not even your normal ceiling panels.


nope, not even gypsum board.
even tho gypsum board is probably one of the best material for HT ceiling.
they're good, good insulation, good vibration characteristics, good this good that, but they still vibrate with bass hits.

a friend had even used thicker partition boards used for wall partition as ceiling panels, something like this:

and it still vibrate with his multisub LFE.

the best is to have a solid reinforced concrete floor slab as a ceiling.
because the best ceiling is no ceiling. because ceiling will vibrate.

but i can't pour an RC slab on top of the HT room.
there's no second floor there.
not having a ceiling meaning exposed roof structure meaning too much bass power required for room compression.

your normal ceiling looks like this:


where the ceiling are flat on the bottom and the trusses are on top.


the ceiling panels are (usually) screwed to the support trusses using flat head flush screw. then painted over.
or nailed to the trusses if wooded supports are used.

since i love going the unconventional route, i'm gonna invert the ceiling and make my life harder.


i give you guys the DIY inverted ceiling. sloped.
DIY inverted sloped ceiling ala DIY style.

a few things i'm trying to minimize (in order to avoid rattling and flexing):

• as less joins as possible
  
• largest panel size to avoid shifting panel movement.
  
• as rigid as possible, especially for the trusses.
  

all things considered, the best is to have the ceiling on top.
the support trusses will naturally support the ceiling with little nailing/screwing and allows for larger gaps to be used in between the panels.

all the good stuffs.
so DIY inverted sloped ceiling ala DIY style it is.

tldr; i'm gonna build a floor to replace the ceiling.
because ceiling vibrate.

enough of the design.
(it's booooring)
let's build something.


the trusses are gonna be built using these 3"x2" square metal tubing.

i've worked with 3x2 wood trusses before, and did considered them.
but to have the best strength i need to have them lap joined at all the connections.


55 lap join is no fun.
prolly will take me another 10 years to finish.
nope.

so a DIY flexible wood truss support system (heh) are dropped in favor of
a DIY rigid metal truss support system using square metal tubing

tldr; i'm gonna build the ceiling truss using metal tube.

since the square tubing is pretty thick, you can't use regular knife to cut it.
so using a blowtorch or a plasma cutter, cut the tube to required length.




ok joking you don't need a plasma cutter.
it's thick but not that thick. and it's a straight cut, cut it off using a simple cutoff saw.


i sprayed the trusses using automotive paint.
1st layer using 2k epoxy primer.
2nd & 3rd layer using the flat black autocolor paint.



then mount the sides first as a guide for all the other beam.

oh and since it's metal, you need to weld the stuffs together.

i'm using these:


the larger WIM migweld 210s for on the floor welding for the wall mounts.
and the smaller multiprocess MasW MIG-201 for off the floor welding.

both are configured for GMAW gas metal arc welding process, aka (DIY style) MIG metal inert-gas welding.
i really much prefer the WIM unit as it produces better deposition with better current regulation, but at 100kg i can't take it off the ground.

both are configured for

• 0.8mm ER70S-6 carbon steel wire
  
• 7lpm CO2 shielding gas rate
  
• various voltage/current/wire speed according to material condition.
  

didn't use (DIY style) GTAW gas tungsten arc welding for this too slow i get tired.
also didn't use (DIY style) SMAW shielded metal arc welding for this hard to control weld pool while you're hanging on the ceiling

it doesnt look as DIY ...
more like to profesional ..

very technical regardless of room sound analysis and construction work
really a good job here with your detail sharing information..

please keep on updating here the progress.. very exciting DIY project

Excellent DIY work!
Just a small observation, the metal tubing may cause some ringing problems with certain frequencies (just like metal stands that need sand filling) so probably you would have thought about having a fabric layer to solve that potential problem.
Please keep posting your progress and best hope you will realise your dream.

this is a truly impressive work!

well done sir, i am following the thread and looking forward for the next episode!

where are you based?

Nice work... great to see the progress.

Hi
Wanted to know how is the room now, is it completed?