[Mark Techer]

This is my room design. Normally I charge a fee for this, but I have decided to post it here so that the members of HDT can access it for free. This is not straight out of my book titled “Understanding Surround Sound – 5.1 And Beyond…” but was introduced to my business to try to help those building a dedicated room.

I have added some comments in inverted comers highlighting the points that I have to deal with on a day to day basis whilst consulting in home theatre.

Enjoy, and I hope it help some or you in your next project…

ROOM DESIGN

STEP 1.

Fill out the quick survey to inform the designer of your requirements.

“I generally get the client to circle options so that I have a better understanding of what they actually want or expect from their systems.”

1. How large would you like the room to be?

A. As large as possible.
B. Medium size.
C. Small room.

“This question might seem stupid, but you should see some of the responses I get to it.”

2. How many seats would you like in your room?

A. 1 – 5.
B. 6 – 10.
C. More than 10.

“This question may seem trivial, but face it, if the entire family can not be seated, then there is not much point in going ahead with the project.”

3. How large would you like the screen to be?

A. Up to 100 inch.
B. Greater than 100 inch.
C. Wall to wall.

“Again it just to see what some people are really thinking about.”

4. How many channels of sound would you like?

A. 5.1
B. 6.1
C. 7.1

“This is the point when you have to break it to some of them that the old Dolby Pro Logic system they bought in ’92 just won’t cut it.”

5. How should the room sound?

A. Fixed acoustic environment.
B. Adjustable between reflective, diffuse and absorbent.
“If they answer B to the question their bank account needs be to quite large.:D”

STEP 2.

Choose Acoustic Ratio And Room Volume.

Ratio 1 – 1.0 : 1.3 : 1.6

Ratio 2 – 1.0 : 1.6 : 2.3

Ratio 3 – 1.0 : 1.6 : 2.6

The Acoustic Ratios provided above are proven to work in rooms used for reproduced sound applications. They are calculated where the “1.0” is the ceiling Height, followed by the Width and the Length.
Room volumes should be kept below 56.6 cubic meters (2000 cubic feet) when amplifier power is limited to 100 watts per channel into 8 ohms and when loudspeaker SPL (1w/1m) figures are less than 87dB.

“I have added cubic feet in brackets for all the guys that don't use the metric system.”

Ratio 1 – 1.0 : 1.3 : 1.6

2.40m x 3.12m x 3.84m = 28.75 cubic metres.
(8.0ft x 10.4ft x 12.8ft = 1064.96 cubic feet.)

2.70m x 3.51m x 4.32m = 40.94 cubic metres.
(9.0ft x 11.7ft x 14.4ft = 1516.32 cubic feet.)

3.00m x 3.90m x 4.80m = 56.16 cubic meters.
(10.0ft x 13ft x 16ft = 2080 cubic feet.)

Ratio 2 – 1.0 : 1.6 : 2.3

2.40m x 3.84m x 5.52m = 50.87 cubic meters.
(8.0ft x 12.8ft x 18.4ft = 1884.16 cubic feet.)

2.70m x 4.32m x 6.21m = 72.43 cubic metres.
(9.0ft x 14.4ft x 20.7ft = 2682.72 cubic feet.)

3.00m x 4.80m x 6.90m = 99.36 cubic meters.
(10.0ft x 16.0ft x 23.0ft = 3680 cubic feet.)

Ratio 3 – 1.0 : 1.6 : 2.6

2.40m x 3.84m x 6.24m = 57.50 cubic metres
(8.0ft x 12.8ft x 20.8ft = 2129.92 cubic feet.)

2.70m x 4.32m x 7.02m = 81.88 cubic metres.
(9.0ft x 14.4ft x 23.4ft = 3032.64 cubic feet.)

3.00m x 4.80m x 7.80m = 112.32 cubic meters.
(10.0ft x16.0ft x 26.0ft = 4160 cubic feet.)


STEP 3.

Decide On Number Of Seats.

The width as well as the depth of the seating area will affect the Minimum Seating Distance (MSD) from the screen as well as the Maximum Screen Width (MSW) for a given room.

Consideration to the position of the door(s) is also necessary should the room be designed for stadium style seating. Side entry is recommended for this type of design.

Isles located at the sides of a room should be at least 600mm (2 feet) wide for rear door entry.

Seating row distances should be at least 900mm between centers or a minimum of 300mm (1 foot) between rows when seats are greater than 600mm (2 feet).

STEP 4.

Choose The Desired Screen Aspect Ratio.

Ratio 1 – 1.78 : 1 (16:9) allows for 12:9 and 16:9 from either a stand alone 16:9 projector or a 12:9 projector with an external 16:9 lens.

Ratio 2 – 2.35 : 1 (21:9) allows for 12:9, 16:9 and 21:9 with a
16:9 projector and external 16:9 lens. If 12:9 projector is to used with the external 16:9 lens, 12:9 and 16:9 images are all that is possible.

The Maximum Screen Width will be affected by two things –
1. The Minimum Seating Distance.
2. The type of projector and use of the external 16:9 lens.

The minimum seating distance is chosen to allow –
1. An image that dominates the field of view without the audience members having to move their head.
2. No visible pixel structure seen on the screen from the projector.

This depends of the type of projector and the use of an external 16:9 lens.

A Stand alone 16:9 projector will be able to produce all images from 12:9 to 16:9 at the same height. Images wider than 16:9 will be displayed in a “Letter Box” format at the same width. Stand alone projection devices should be set up to display a Maximum Screen Width image no wider than 26 degrees from the back of the room. This is found by dividing the Room’s Length by 2.2. The Minimum Seating Position should be no less than 36 degrees or the distance of 1.7 times the Maximum Screen Width.
RL / 2.2 = MSW. MSW x 1.7 = MSD.

A 16:9 projector used with an external 16:9 lens will be able to produce images from 12:9 to 21:9 at the same height. When a 16:9 projector is used with an external 16:9 lens, the Maximum Screen Width of 36 degrees is found by dividing the room’s length by 1.7. The Minimum Seating Position should be no less than 1.7 times the Screen Width for an image of 16:9 not 21:9.
RL / 1.7 = MSW. RL / 2.2 x 1.7 = MSD.

A 12:9 projector used with an external 16:9 lens can be made to perform the same as a true stand alone 16:9 projector as MSW and MSD should be calculated as described above .

STEP 5.

Finding The Best Loudspeaker Locations.

The 3 LCR speakers across the screen will be symmetrically spaced Left and Right from Centre. They should be the SAME make and model and positioned at the same horizontal plane. For MUSIC applications, the Left and Right speakers may be placed as wide as 30 degrees form the Centre speaker. For FILM SOUND the speakers should be kept close to the edges of the screen. Less than 4 degrees is preferred, but 15 degrees is acceptable. Screen channel speakers should be direct radiating, and feature a degree of Controlled Vertical Dispersion.

The number of Surround speakers may vary from 2 to 4 depending on the type of format decoder. Today’s 7.1 systems feature a fixed Adaptable Surround Array™ comprising of 4 surround speakers, 2 at the sides of the room and 2 at the rear of the room. Their exact locations will depend on the width and depth of the seating positions in order to produce the most enveloping surround experience possible.

All Surround speakers should be the same make and model, be symmetrically spaced from the Centre speaker and be mounted at the same height. Surround speakers may be mounted as high as 45 degrees above seated ear height. Surround speakers may be either Diffuse radiators or Direct radiators, or a combination of both.

The Subwoofer(s) should be able to produce loud clean bass at levels as high as 115dB. They may be placed where ever a flat in-room response is obtained.

STEP 6.

Acoustic treatments.

There are 2 main objectives with rooms used for film sound playback–
1. controlled reverberation.
2. sound isolation.

There are 3 main types of acoustic treatments –
1. absorption.
2. diffusion.
3. reflection.

The requirements for multi channel sound differ from conventional 2 channel stereo. 2 channel stereo works well in rooms that are 50% absorbent and 50% reflective/diffusive to help re-create the balance between direct and reflected sound energy.

Multi channel sound (FILM SOUND) requires control over reflections that are not part of the original sound mix. Therefore room surfaces must be less reflective and more absorptive.

Control of Reverberation and Sound Isolation may be obtained from sound deadening material such as acoustic grade plasterboards with resilient mounting systems, air spun concrete wall materials and compressed fiber glass panels.

The use of resilient mounts works to minimize sound transmission through walls for timber frame construction. Acoustic grade fiber glass bats are also recommended to help reduce sound transmission.

Doors seals should be considered along with seals for the light and electrical fittings.

Air conditioning units need special low noise vents.

Step 7.

Example.

The following example takes all specification to their maximum limits.

An ideal room shall have a acoustic ratio of 1.0:1.6:2.6. Based on a standard 2400mm ceiling, the dimensions are 2.40m x 3.84m x 6.24m. The internal volume is 57.5 cubic metres. Room volumes less than 56.6 cubic meters are preferred when amplifier power is less than 100 watts per channel. THX Certified products are available in categories, THX ULTRA 2 and THX SELECT. “SELECT” products are specifically designed for such rooms.

Side entry will allow for stadium style seating and the seating shall consist of two rows of four seats with the back row raised by no more than 300mm. Apart from the main entry, the room should not have any other external openings unless required by law. Equipment racks may be built in and should allow adequate ventilation.

The full front wall and lower half of the side and rear walls shall be treated with a sound absorptive product. This product may be covered in acoustically transparent covers or thin curtains to appear more cosmetically attractive. Carpet with thick underlay should be used on the entire floor. The room should be capable of total black out and the internal colour scheme should not bias any colour in the video system.

The video projection device is a true 16:9 stand alone unit. The screen aspect ratio is to be the native HD ratio of 1.78:1. The screen width is to no greater than 2.83metres. The screen height is therefore 1.59m. The minimum seating distance to the screen is 4.8m. The back row will be 5.7m from the screen.

Screen material should provide “gain” of no more than 1.3 for lamp driven, solid state devices. Preferred gain is less than one. Conventional acoustically transparent films screens are not recommended unless specified as home theatre grade. If an acoustically transparent screen is used, the LCR speakers should be placed mid height with Centre placed at centre of the screen and the Left and Right placed just inside the edges of the screen. They should be “infinitely baffled” and the surrounding area treated with sound absorptive material. This material should be painted or dyed black to prevent a double image from the projector being seen.

For fixed “solid” screens, the front LCR speakers shall be placed just below the screen at the same height. The Centre speaker is placed at centre of the screen with the Left and Right placed at the edges of the screen. All three speakers should be the same make and model vertically orientated unless specified in the design.

The Surround speakers shall be mounted on the walls higher than the screen channel speakers. The Left and Right Surround speakers will be mounted at +/-90 degrees to distance half way between the front and rear rows of seating positions. The second pair will be mounted on the back wall at same width as the seating area. All four Surround speakers should be the same make and model. They should not be aimed at the listening position but rather aimed to fire across the room. Depending on the type of program to be played, the Surround speakers may be either Direct radiators or Diffuse radiators or a combination of both.

Both LCR and Surround speakers should each be able to produce sound pressure levels of 105dB from 80Hz to 20KHz.

The Subwoofer(s) may be placed where ever a flat response is obtained. The Subwoofer must be able to produce sound levels of 115dB in all frequencies in the band up to 80Hz.

Sound pressure levels for all channels in the system should be set using minimum of a sound pressure level meter and the internal test tone generator from the AVR. With the master volume set to a “0dB” level, the level on the meter should read +75dB per channel when set to “C” weighting and “slow” response.

A part of the THX certification program is to measure the exact output of the test tone generator. With some non-certified products, the output of this tone may be as much as +/-4dB, resulting in inaccurate level settings and levels of playback.

Video test patterns should be used to ensure correct values of Contrast, Brightness, Colour (Tint) and Sharpness. The video projection device should be able to be set to D6500 Kelvin.

This information remains the property of CINEMATIC AUDIO VISUAL EXPERIENCE (does anyone else think my business name is too long?). It is not to be copied or distributed in any way - not that I can stop anyone now.
:cheers:
Mark

[LeeS]

C.A.V.E., hmmmm, I've been told that my HT is like a cave.... :)

[Mark Techer]

I abrieviate the name to CAVX over the phone, where the X is for experience.
I also have a registered trade mark too. It is a styalized word mark "cavx cinematic audio visual experience". The number is 889441 registered with the Commonwealth of Australia. Its mine for at least the next 7 years. You can look it up, but I'm not sure about the URL though.

My theatre - the SRT (Small Room Theory) gets called "the cave" by family as well...

Mark

[MJC]

The one thing I don't agree with THX is the 80 htz crossover to the sub. That frequency is too high, the subs will produce sounds that can be located. 60htz is a much better crossover point.
Of coarse most satellite speakers can't do 60htz because they follow THX's 80 or cross at even 100.

[Mark Techer]

Research suggests that originally the crossover was going to be 120Hz. 80Hz is a bit of a compromise. It was chosen to represent the widest range of sources, and in the end, the male human voice was a deciding factor, because your right, certain musical sources sound better when crossed at a lower frequency, yet again some need a higher one, so 80Hz is somewhere in the middle I guess...

Mark

[bru87tr]

I agree with MJC.

[LQQK]

I wanted to vote for this Review...But it's not on the list:confused: :confused:

LQQK

[Mark Techer]

Thanks LQQK

It's really not a product review(though room design is one of my products/services), more of an informative review, but thanks anyway...

Mark

[LQQK]

Mark if you have the time check out my situation::::

PJ Questions

LQQK

[Mark Techer]

LQQK, I have posted my response on the link that you have provided. I hope this helps...

Mark

[LQQK]

Quote

Originally posted by Mark Techer
LQQK, I have posted my response on the link that you have provided. I hope this helps...

Mark

Mark

Thank you for the info..I'm still trying to digest it.

LQQK

[Mark Techer]

Good luck with that. If you need more help send me a PM...

Mark

[Mark Techer]

Hello HTD,

They say a picture is worth a thousand words, so I have added an image to hopefully better explain my room design...

Mark

[LQQK]

Mark Techer said:

They say a picture is worth a thousand words,

You'r right..These are the best long term HT chairs..
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LQQK

[Mark Techer]

Ha funny so where are the 1000 words :D...

Mark

[eazyepps]

I was going to post something like, "I'm going to be building a house this summer (of cousrse with a home theatre in the basement), does anyone have any suggestions," but I think you covered it all!

Thanks Mark!

Eric

[Mark Techer]

Your wecome Eric, I hope it all works out for you and we can see the results here soon...

Mark