Dedicated home theatre

Rajesh,

He is not suggesting to keep L/R at 21 ft apart. Just spread them enough to make the perfect 60 degree or so. With a listening depth of 10 ft, you may have to spread these around 12~13 ft. This configuration is suggested to get a wider sound stage compared to what you would get with speakers spread out max 10 ft wide.

If you do want to put the screen on 10 ft wide wall, then to get a wider sound stage, you would have to spread those max possible, that means at corners. Baffle wall is recommended to get rid of the room boundary interference.

One point to note - I checked out the speakers you planning to build. They have the port on the back. Since you will have these speakers close to the wall (irrespective of baffle wall or not), move the port to the front. Having the port in the back may cause issues.
 
hi manoj

I meant baffle wall on the front and 2ft insulation (if you can afford) on the back wallThis you don't have to do right away or during build. You can add the absorption on back wall later or when you have money

now i got it,initially i thought insulation was in the front wall behind along with baffle wall , having a baffle wall is a good method especially when you have a less room width,i will certainly will go for it but ofcourse when things get settled,and placing around 1inch absorption on it,will not add to the cost,if the result is great.

I got my transparent screen from SeymourAV. They have a DIY material option which is fairly cheap. Another factor with baffle wall is - you need to place around 1" or so absorption on it. It will also add to the cost.

At what price did you get your transparent screen and size and hows the clarity i mean picture quality.i was thinking for fixed screen from carl's screen i can go either for a 120in or max 130 in screen.

If you have space behind, the best bass trap is to just pile up 2 ft thick insulation all over the back wall. You don't even have to take it out of covers etc. just pile it up and cover it. That will take care of all the standing waves. That's how I would do it. Smaller bass traps don't do much absorption.

By insulation you mean placing using 2ft thermocal sheets right,???if yes they are reflective and produces echo..if rear wall with 2ft insulation can overcome the standing waves what about the front wall esp.. the corners??

By smaller bass traps you meant the 4in ground to ceiling bass traps for all the four corners,say if i put a 6in thick glasswool wont they be effective...

Do you have an idea as to what type of material that can be used to cover the entrance door from inside to make the ht room sound proof,can i have another door for exit to the outside gallary,i know reading your earlier posts to others you prefer air tight room for ht..if this is followed then what about air circulation in the room.

r/s
 
Rajesh,

He is not suggesting to keep L/R at 21 ft apart. Just spread them enough to make the perfect 60 degree or so. With a listening depth of 10 ft, you may have to spread these around 12~13 ft. This configuration is suggested to get a wider sound stage compared to what you would get with speakers spread out max 10 ft wide.

If you do want to put the screen on 10 ft wide wall, then to get a wider sound stage, you would have to spread those max possible, that means at corners. Baffle wall is recommended to get rid of the room boundary interference.

One point to note - I checked out the speakers you planning to build. They have the port on the back. Since you will have these speakers close to the wall (irrespective of baffle wall or not), move the port to the front. Having the port in the back may cause issues.

i dont deny sdurani suggestion of getting a wider soundstage,but i prefer your method (baffle wall) since it does justice to both audio and video.

thanks for going through all the links i provided,clearwave are world famous Loudspeaker Designers,there configuration is to produce all the freq in one box like (low,lowmid,mids,highs) result being sound closer to real life experience,the same i am trying to implement using the peerless drivers.

good suggestion of placing the port in the front,i will do it,only draw back is it will increase the height of the box,at present the main box height is 49in,if 4inch port is placed in front, now the Height will be 53in.

r/s
 
should i go in for the 27ft room depth or 21 would be good enough
21ft will be fine.
what type of acoustic material/thickness should be placed on the door to make it sound proof as well as absorbtion/difussion
Soundproofing requires a solid-core door and a tight seal. Placing treatment on the door doesn't make it soundproof (treatments are for shaping the sound in the room, not preventing the transmission of sound through the walls).
 
Build a baffle wall, house your Left/Center/Right speakers in there. This will remove SBIR issues your room presents. As a bonus, you can use the space behind baffle wall for subwoofers and get yourself a kick-ass infinite baffle subwoofer.

Interesting Manoj! Subwoofer driver would be fitted on the baffle wall I presume.

If you have space behind, the best bass trap is to just pile up 2 ft thick insulation all over the back wall.

But won't that further reduce the length physically available in the room!

Sub at the centre of room width will cancel the 1st width mode at 52Hz. If you can raise the sub to the centre of room height, you can also cancel the 1st height mode at 57Hz.

Could you kindly elaborate?
 
At what price did you get your transparent screen and size and hows the clarity i mean picture quality.i was thinking for fixed screen from carl's screen i can go either for a 120in or max 130 in screen.
I think I paid $295 for 13 ft wide material including shipping. Mine is xD material. Its quite fine material, but you can see the weave around 10 ft or so against white background. I seat about 11 ft away, so no issues. My screen is 11 ft wide (I tilted material to avoid moire). They now have even a finer, 4K material and does not need tilting. It however needs a black material as backing.


By insulation you mean placing using 2ft thermocal sheets right,???if yes they are reflective and produces echo..if rear wall with 2ft insulation can overcome the standing waves what about the front wall esp.. the corners??

By smaller bass traps you meant the 4in ground to ceiling bass traps for all the four corners,say if i put a 6in thick glasswool wont they be effective...

No, I meant the fluffy insulation. They come in rockwool batts and are quite fluffy. You don't take those out of their packing and just stack them.

As for the bass trap you suggesting, I take those are the chunky, triangular shaped, right? 4 to 6" thick won't absorb lower subwoofer frequencies. If you plan to build a 6" thick then build it like a normal rectangular absorber and let it straddle the corner. Combined with the cavity behind, it will be better. Like this
corner-bass-trap-L.jpg

Do you have an idea as to what type of material that can be used to cover the entrance door from inside to make the ht room sound proof,can i have another door for exit to the outside gallary,i know reading your earlier posts to others you prefer air tight room for ht..if this is followed then what about air circulation in the room.

r/s
Like Sanjay said, to make it sound proof, use sturdy door and get it completely sealed. If air escapes, so will sound.
 
Interesting Manoj! Subwoofer driver would be fitted on the baffle wall I presume.
Yes. There are multiple arrangements on how to install the drivers in infinity baffle arrangement
But won't that further reduce the length physically available in the room!

Every room treatment costs real estate. He has length to spare, hence the suggestion to add it on the back.
 
21ft will be fine. Soundproofing requires a solid-core door and a tight seal. Placing treatment on the door doesn't make it soundproof (treatments are for shaping the sound in the room, not preventing the transmission of sound through the walls).

As suggested in page 1 by naturelover:

From what I have read, this 2:1 ratio is bad for sound. Maybe you could check this out on the net.
But, as raghu has pointed out, this may not affect the average listener so very much. Like the King's Durbar bit

As per your suggestion go for room size 10/20,dont you think that ratio is bad being (2:1.),why cant i go for depth of 27ft..in future it can be of benefit for audio upgrades like atmos,dtsx,aero

good suggestion to go for solid core door,i.e door thickness counts and also being air tight sealed,i will think about it.

one more thing can i use 2 doors in my HT,since my ht room is located at the rear/back end of my house,so that if anyone comes to the room he has to cross all the rooms from inside of my house,so by having another exist door which leads to back yard, it will be easy to come and go,but that should not creat problems for room acoustics and sound proofing.

thanks
r/s.
 
Interesting Manoj! Subwoofer driver would be fitted on the baffle wall I presume.



But won't that further reduce the length physically available in the room!



Could you kindly elaborate?

hi capt,

There is a very good article about sbir issues and how to over come them by using baffle wall.

baffle wall is recommended for ht room which has min depth of 25ft or more,so one has enough space in the front to build them,width no issue as anyone can build baffle wall, but for ht atleast 10ft width is recommended.

i think we can mount our ready LCR boxes in the baffle wall in such a way that the baffle of the speakers are flat on the wall.wherein our L/R mains can be kept to the extreme ends of the front wall,but the wall should be acoustically well treated..manoj correct me if i am wrong.

http://arqen.com/acoustics-101/speaker-placement-boundary-interference


R/S
 
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Could you kindly elaborate?
Placing a subwoofer at the null location of a mode will cancel that mode. The midpoint of room width is where the first width mode nulls. Placing a sub there cancels that mode. It works the same in the vertical dimension.
 
No, I meant the fluffy insulation. They come in rockwool batts and are quite fluffy. You don't take those out of their packing and just stack them.

any source of getting them in india & cost factor.

If you plan to build a 6" thick then build it like a normal rectangular absorber and let it straddle the corner. Combined with the cavity behind, it will be better. Like this

how effective it will be compared to your suggested insulation method for rear back walls,and again is this 6" rectangular absorber to be effective has to be placed on all 4 corners of the room or only at the rear walls.

r/s
 
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What's bad about it? You can go for any depth you want. It's your room. Room length has nothing to do with Atmos, DTS:X and Auro.

Ok so i can consider both the room dimension options,why i was thinking of
a bigger depth was for better seating placements (2 rows) if required in the long run,convenience to adjust the 1st row seating according to the screen size,my screen will be max 130in,so 1st row seating has be at min 15 to 16feet ,the balance of 10 feet can be left for placing the surround channels (7.1ch/7.1.2) for better realistic soundfield by adding more depth to the surround experience.

Room construction cannot be redone often esp.if your ht setup is ready to use.Thats my main worry to ask you if i can increase the depth.

r/s.
 
One point to note - I checked out the speakers you planning to build. They have the port on the back. Since you will have these speakers close to the wall (irrespective of baffle wall or not), move the port to the front. Having the port in the back may cause issues.

hi manoj,
one more solution i can implement is if the port is placed at the rear of the speaker box,i can place the LCR say 2 feet away from the back wall wont that solve the issue,coz by placing the port in front as i already mentioned will increase the height of the already tall towers creating screen viewing problems,i also cannot install as you suggested 6" rectangle bass absorbers at the front corners that will eat up the width of the front wall by 410mm (1.3ft)x2=2.5ft.i have to use them only for the rear walls.

i am planning to install the projector either ceiling or on the rear wall which depends on how the projected picture adjusts to the screen width,also see that the projector is placed in such a way from the top wherein the main L/R speaker boxes does not come in its projection path,so that i can use the entire width of the front wall.

r/s
 
convenience to adjust the 1st row seating according to the screen size
That's backwards. What if screen size forces the seating at a location that is acoustically terrible? The entire row of listeners will be stuck with bad sound.

The normal approach to home theatre design is to pick room locations that are acoustically good, THEN pick a screen size that gives you the viewing angle you want.
 
Placing a subwoofer at the null location of a mode will cancel that mode. The midpoint of room width is where the first width mode nulls. Placing a sub there cancels that mode. It works the same in the vertical dimension.

Using height in deciding room placement is a new perspective to me which I never thought about. Thank you for pointing me in that direction.
 
any source of getting them in india & cost factor.



how effective it will be compared to your suggested insulation method for rear back walls,and again is this 6" rectangular absorber to be effective has to be placed on all 4 corners of the room or only at the rear walls.

r/s

I do not know the source & price in India. Start with the contractor of HVAC systems for insulation material. They would have it way cheaper. Same material will be sold by acoustic cos at a huge margin.

As for 6" thick broadband bass trap, it will absorb down to 560 hz or so. If you leave an air gap of 6" behind it, then it will be around 280 hz. It can absorb some of the energy from frequencies below that, but not all.
You can do this calculations yourself.
Absorption thickness (in ft) =0.25(1130/frequency)
 
hi manoj,
one more solution i can implement is if the port is placed at the rear of the speaker box,i can place the LCR say 2 feet away from the back wall wont that solve the issue,coz by placing the port in front as i already mentioned will increase the height of the already tall towers creating screen viewing problems,i also cannot install as you suggested 6" rectangle bass absorbers at the front corners that will eat up the width of the front wall by 410mm (1.3ft)x2=2.5ft.i have to use them only for the rear walls.

i am planning to install the projector either ceiling or on the rear wall which depends on how the projected picture adjusts to the screen width,also see that the projector is placed in such a way from the top wherein the main L/R speaker boxes does not come in its projection path,so that i can use the entire width of the front wall.

r/s
That's the choice you would have to make. Just keep in mind - you wont be able to make use of the ports if you decide to put these speakers in the baffle wall later. If your intention is to use baffle wall, then front ported or sealed speakers is the way to go.
 
hi capt,

There is a very good article about sbir issues and how to over come them by using baffle wall.

baffle wall is recommended for ht room which has min depth of 25ft or more,so one has enough space in the front to build them,width no issue as anyone can build baffle wall, but for ht atleast 10ft width is recommended.

i think we can mount our ready LCR boxes in the baffle wall in such a way that the baffle of the speakers are flat on the wall.wherein our L/R mains can be kept to the extreme ends of the front wall,but the wall should be acoustically well treated..manoj correct me if i am wrong.

Speaker Placement 101: How to Fight Boundary Interference


R/S
There is no requirement of 25 ft length min. You can certainly build a baffle wall for smaller rooms.

yes, speakers are flush mounted on the wall. Think of it as in-wall front speakers. Except, you can stick in the normal speakers there.

if one was using baffle wall just for audio, then there is no need to put insulation on the baffle wall. But if you are using it for video and there is an acoustic screen in front of it, then high frequencies bounce off from the back of screen. Those needs to be absorbed hence the insulation. That insulation will also absorb the reflections from rear surround speakers making the front sound stage dead and very clear.
 
That's backwards. What if screen size forces the seating at a location that is acoustically terrible? The entire row of listeners will be stuck with bad sound.

The normal approach to home theatre design is to pick room locations that are acoustically good, THEN pick a screen size that gives you the viewing angle you want.

100% true in your saying,now my main concern is to setup the ht room go step by step or else there will be no starting point,when the above issue comes of seating placement etc..then will refer you and manoj..

by next week i should complete the room partition wall breaking for more depth taking into account for future baffle wall setup,side by side box building,then comes wall treatment like putti,paint,false ceiling,etc..long way to go..

thanks
r/s.
 
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