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Old 17th April 2007, 03:59 AM   #1
JinMTVT is offline JinMTVT  Canada
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Default Ultimate home theater rooooom ..NEED UR HELP NOW! :)

As a few of you migh know by one of my last thread,
i am currently completing my new house plans.

I have a special place in wich i will construct my home theater room, wich will be of maximum 30' by 20'
with a height of 9' maximum.
I am building my house with ICF ( isolated concrete forms ) So i have the possibility of making all the walls and ceiling out of polyestyrene foam on a concrete back,
wich would isolate almost completly this room from the rest of the house ( it will help with the bass alot i presume )

Since i didn't wanna hear about Surround setup, for the last year i had planned on going for a ultimate stereo setup in this room ..as i didn't understand the benefits of the surround setups . But as i read and was directed to information from kind users of this community,
i now what to make this happen as a surround system.

Now that is where i will need you help !!

I need to know what to do, and how to do it ...since i have seriously limited experience and konwledge about room accoustics and it's implications with surround sound.

I have no compromise for looks as i dealt this room with my wife for other stuff she wanted ...
so it can look very ugly but sound perfect and i won't care at all .

What i have planned is to use multiple 15 or 18" woofers in the front in concrete cavities for the sub bass section ..and alot of high quality drivers for all the rest of the system . but i do not want to discuss specific drivers for now ..what i need to know is how all this works to get the magic out of the surround sound.



So lets attack surround sound ...
is 5.1 enough ? do i need to setup for 6.1?
I guess that all drivers need to be timbre matched
( i will probably use the smae drivers all around neway)

Do we want to absorb as much sound as possible through the walls to limit all possible reflections and leave only the direct sound hit us ?

How do i calculate and achieve the required dispersion for all the seats in the room ? ( probably 6 or 8 places in 2 rows )i'll probably be using dome tweets and cones
for mids ...

should i limit the quantity of drivers as much as possible to get better imaging , or use line arrays to get as much volume as possible ?

And i can make the room of almost any configuration ,
angled walls ( porbably rear and 1 side ) or even rounded , i can include angles so that the front drivers are reflected back when hitting the side walls ..

Neway i'll let you all knowledgeable users tell me what we are looking for when designing such room

thanks all for your time
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Old 17th April 2007, 10:39 AM   #2
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Ok, If you have the oportunity to start from scratch, I would suggest that you mount all the boxes flat into the wall, use a dampening material on that wall so that early reflections are minimised.

Mounting the speaker flat in the wall is the basis of THX in the cinemas, It allows the speaker to work as a piston and with the air is controlled, no need for baffle step compensation and allows a far more acurite wave to be created, than possible from a regular box.

A large sealed inclosure will sound better than bass reflex in this mounting. The flat baffle wall will boost the lowest frequencies. So bass reflex designs would sound very boomy and usually need to be cut back by eq.

As you are constructing your options for breaking up the sound on the rest of the walls is up to you, curtains like in cinemas, 3d patterns with the brickwork would all help, or some movable fiberglass baffles on frames can do the job very well.

I would also suggest 15"duel concentric speakers like tannoy or altec (the very best that I have heard) others make cheaper options such as p.audio and eminence ect. The single point sourse does sound far more natural than conventional split designs from my experience.

As for the suround channel, the more speakers the better, 8 ideally or 4 would be good, bi polar designs should be considered, frequency range is 100hz to 7,000. 4 inch full range speakers can cover this range very very well. Speakers start 2/3 down the side walls and behind on the back walls for best seperation.

Ive designed and custom built several large cinema speaker systems over the years and this is what I would do for my own pleasure in your place.

Good luck on whatever style of system you choose, and on the rest of the house.
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Old 17th April 2007, 11:33 AM   #3
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Surround channels in DD/DTS and newer are all descrete and full range, they were only bandwidth limited in Prologic
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Old 17th April 2007, 12:53 PM   #4
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um no there not, What do you think 5.1 means? Six channels or 5 channels? or 5 channels with one split @ 100 hz to equal 6, Now if thats the Left surround thats split, do you think the sound mixer is going to put deep bass on the right surround only ? or put the deep bass for both the surround channel into LFE channel which has a stack of 18" speakers on stage mounted into a Baffle Wall?

Cinemas and Mixing suites set up to either DOLBY or THX standards use an academy curve on the surround chanel. ie 3 db roll off from 2K to create a more defused and less directional effect with the multiple speakers.

So if you want to have a surround effect like the way the movie was mixed and was intended to sound like, um my suggestion was fine and a bit cheaper than what a salesman would try to sell you.
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Old 17th April 2007, 02:59 PM   #5
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Calm down mate

What you're saying may be true for cinema installations, but home theatre systems are different.

Taken straight from the Dolby Website...
"* The sound information contained in each of the six available channels is distinct and independent. These six channels are described as a "5.1-channel" system, because there are five full-bandwidth channels with 3 Hz to 20 kHz frequency range for Front Left and Right, Center, and Surround, plus one "Low Frequency Effects" (LFE) subwoofer channel devoted to frequencies from 3 to 120 Hz"

If you done believe me (or Dolby ) try setting your system up so it doesn't redirect bass from the 5 main channels to the sub and play Saving Private Ryan at reference level. Then watch as your 4 inch full range surrounds fire their cones across the room
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Old 17th April 2007, 05:25 PM   #6
JinMTVT is offline JinMTVT  Canada
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Quote:
Originally posted by Cameron Glendin
Ok, If you have the oportunity to start from scratch, I would suggest that .......... style of system you choose, and on the rest of the house.

Ok so why suggesting bipolar units ?

What do we want to achieve with the side and rear speakers ? do we want point source or a lot of reflections ? ( cause my guess is that bipolar will induce alot of reflections ? )

do i set everything up so that all the loudspeakers send direct waves to the listeners, or are the requierements
for th side and rear different from the front ?


Then explain why concentric 15" ??

for surround..more would be better...

do you mean more drivers per loudspeaker or more lousdpeakers ???




my question on the size of the source is more toward..
should i consider using alot of drivers in arrays or to use as less as possible to get more location from all the drivers ??
my guess is that it is the same as with regualr stereo setup , as the perfect driver would radiate from a point source all the time at all frequency ??




about dolby thx and all ..
are there papers i could read that would give me definite pointers into the requirements and definittions of all the goals ??
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Old 17th April 2007, 07:56 PM   #7
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Personally, I use a LEDE type of setup, with the surround speakers at the live end.
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Old 17th April 2007, 08:01 PM   #8
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Quite a few people prefer bi-polar surround speakers, myself included. In general the surrounds in movies are used for ambience most of the time, so a difuse sound is what you're mostly after. You still need some ability to pin point the surrounds though for effects you are supposed to be able to locate, so the design is a compromise. I'm going to have a go at some M&K'alike tripoles in the future, as they look to be a good mix of difuse and directional radiation.

Usually the surround speakers are best setup high on the side walls slightly behind you, Dolby suggests between 90 and 110 degrees to the screen. In a 7.1 setup the surrounds stay where they are and the two surround back speakers are placed close togeather and directly behind you, similar height to the side surrounds.

Dolby Digital and DTS are encoding standards, THX is a reproduction system standard, basically a set of specifications a setup must comply with for THX certification. The ideal setup would be 7 full range speakers with dipole radiation for the surrounds, each capable of producing 100db peaks at the listening position and a subwoofer able to produce 115db+. The advantage of having all speakers full range is extra cone area and therefore potentially low distortion bass, and hopefully no sub localisation. The disadvantages are all speakers would require EQ to counter room modes and very large main speakers.

THX specifies main/surround speakers with a 12db/octave rolloff at 80Hz, handing everything below that to the sub. The surround processor/amp adds a 12db/octave, 80Hz rolloff to the main speakers and a 24db/octave linkwitz riley lowpass to the sub, netting a 24db/octave crossover . This is a far more sensible idea as getting you main speakers down to 80Hz in a sealed box and able to output 100db is dead easy and would result in much more domestically acceptable speakers. Usually a single 6-7" woofer per speaker is sufficient, which means you can put more of the budget into the sub/s

To playback at reference level is very demanding for the sub, usually a pair/quad of 15's is required depending on your room and amplifier size. The two things to remember are... 1:- More cone area is better and 2:- You need some form of room EQ.

The front speakers are pretty free choice, some people prefering TM layouts, some prefering MTM's. Again it's one of those things you usually have to try and then decide what you like best. The most important things to remember about the front three speakers are that they are all identical and all placed at the same height. I can't help but laugh when you see pictures of peoples systems with the centre speaker either 10ft above the left and right on top of their projection screen or on the floor below

I have a fairly small room and not many seats so I don't bother with a centre speaker, just the left and right. Unless you have people sitting pretty far off axis a centre isn't really that nessesary.
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Old 17th April 2007, 09:31 PM   #9
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Run, do not walk, to a nearby "home theatre" specialist. It might cost you a little but IF you mess anything up it'll cost you a heck of a lot more to correct it later!
You're going to need equipment anyway so let them help you through the entire process. Win, win.
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Old 17th April 2007, 10:47 PM   #10
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Insulated concrete forms?

Are we talking basement here?

Then I hope this means an hydronic heating system with piping in both the floor below and the floor above. Good for you if that's your plan. You'll get the most efficient heating system and the ability to isolate most of the HT sound from the rest of the house.

Aside from having some concrete forms onsite when the flat work is poured (for sub boxes), I can imagine any other built in design features would be very costly and just be confining for future changes.

"Flat mounted speakers" make sense in many ways, especially to go with flat displays, but this can be done easily utilizing typical stud-wall construction against its interior. Are you planning this anyway? If that's the case and you're going to have plasterboard sidewalls, you might consider framing them in four foot sections, and installing them sawtooth style. If you built that to a soffit you'd have a raceway for future wiring and a unique placement for spot lighting.

One idea I would consider, is to have a utility room behind your entertainment wall to provide access to the component wires, with good lighting.
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