Home Theater tips
Simple ideas for improving your Home Theater Systems
Not all of us have the perfect room available for our Home Theater. Doorways, windows, and fireplaces can all mean compromises in where equipment can be placed. Here are a few ideas that don't cost the earth...
The room...
Rear speaker type and placement
This room is wider than it is long, meaning that the seating position is up against the back wall,
and the surround speakers will be to the left and right of the seating position.
Being so close to the back wall, bipole speakers
would tend to have echo problems with the rear firing driver.
Upfiring speakers work well in this situation but the Hallway and window is in the way.
The solution was to use conventional speakers mounted on the roof,
initially aimed at the seating position
DIY Diffuser Panels
After reading some articles on Dolby 5.1 and THX processing, I decided to try and de-localise the sound coming from the surrounds. I had some polycarbonate roofing left over from an earlier project and made up these diffuser panels
By turning the speaker around and bouncing the sound off the panels, I have been able to generate a more ambient sound. It works particularly well for background sounds such as rain and crowds, and will tide me over till I build some proper diffusers. If I had to come up with a corny name for these, I think I would call 'em Sound Waves
Finally finished writing QRDude, a QRD calculator
and doing a proper writeup.
Will shortly be using this to build some decent diffusers
Reflected sound treatment
The wall behind the seating area is a hard surface, so some absorber is worth having. Foam is mounted behind the seating area to cut down on reflected sound from the main and centre speakers. This makes no difference to the subwoofer
Instead of Acoustic foam, use Eggshell foam which is around 90% as effective. (for high frequencies anyway..)
This is best sourced wholesale from your local rubber and latex dealer
who will charge you about 1/3 what an audio shop would
The new plan...
The screen and chair have been swapped. The absorbers are done. Getting closer to building some QRD diffusers...
Absorbers are 3 layers of 50mm CSR Bradford
Ultratel
- At 48kg/m^3, it's the Aussie equivalent to the popular OC703 used in the USA
50mm * 1200mm * 2400mm sheets @ $80.99aud per sheet (Sept 2009) for the unfaced variant from Insulation Industries. It took 3 sheets
to do the absorbers shown here.
More advanced acoustic treatment
For more advanced treatment of room acoustics, such as the construction of bass traps, see the following external links:
- Building a better bass trap
- Modex commercial bass trap
- Ralph's Aeropanel: A nice DIY wideband absorber panel
- Acoustic damping discussion thread at HTGuide
- Auralex white paper on room treatments (4.4mb pdf)
- Forum on treating recording studios
- Bob Gold's Coefficients for both US and Australian materials, plus tips incl tuning slat and Helmoltz absorbers
- Measuring acoustic absorbtion
- Treatment of room nodes (pdf)
- Rives Audio - specialists in soundproofing
- For Aussie builders, here's a discussion on building bass panels using local materials
- If you want to tackle room nodes to get a more even frequency response, you will need some extra gear:
The Behringer Feedback destroyer is the easiest way to obtain a heap of parametric equalisers. - You can analyse your room using the free Room EQ Wizard software written by John Mulcahy. You will have to become a member at Home Theater Shack to access the software. (Membership is free) They also have a well supported set of discussion forums. The software will even upload the new settings into the BFD via the MIDI port on your computer. See here for a guide on using it.
Bias lighting
Bias lighting is the technique of placing a light behind your TV screen.
This will provide background light via the wall behind the TV, and done correctly,
will increase contrast and reduce eye fatigue by moderating changes in brightness in the room.
Ideally, the spectral output of the light should be of a certain composition, which can be achieved
if you order your light from Cinemaquest who are the experts in this field.
Providing a small amount of light behind the set biases the iris (reducing the range of motion in the iris muscle), resulting in more relaxed viewing...
Glare and reflections are then dramatically reduced, by eliminating any light source from striking the front of the set...
Colors appear richer and blacks are darker...
Contrast and brightness controls can be turned down. Doing this will prevent over-saturation of the phosphors, thereby preserving maximum sharpness and detail...
Here's a discussion thread at AVSForum on bias lighing if you want to see what others think ....
And another one at DTV Forum Australia...
The recommended brightness is 10% of the peak white level of your TV.Being on a limited budget and not wanting to import stuff from the other side of the planet, I had a go myself.
A cheap light dimmer from the local K-Mart was mounted in a box with a lead and an outlet socket. A lamp with one of the "bendy" necks, was used to illuminate the curtains behind the TV and the results were great.
Of course, before you make your own mains powered dimmer box, make sure that you are competent,
lest natural selection improve the species...
Some other sites with tips on Home Theatre design
- www.diy-home-theater-design.com
- Listen to the Music, Not the Room
- John Sayers Recording Studio design forum
- Room response calculator (Excel based)
- HDMI Australia All you need to know about these cables