IMAX Enhanced Design
The THX logo has labeled a
profusion of audio and video product for decades. Yet
many folks wonder, what is THX? THX is simply home
theater standards that manufacturers and installers must
meet to be THX certified. THX, originally a division
of Lucasfilm, is now an independent company. THX is
not a standard such as Dolby or DTS. Yet THX does
outline minimum specifications for amplifiers and speakers
such as flat frequency response, low distortion, and low
noise. In addition, THX makes the following
- Many movie soundtracks mixed with a mid-range boost cause
harsh-sounding playback in a home theater.
- Acoustical reflections from the floor and ceiling smear
sound fields and distort the mid and higher frequencies.
- Compromised speaker placement stimulates room modes that
- Listener placement near room boundaries creates excessive
- Rear channel effects are often unconvincing via dated
surround sound encoding.
As a result, THX standards institute the following
modifications to the electronic processing and the speaker
- THX processing features 'ReEQ' and 'Timbre Match' that
alters high frequency and mid-range output, which results in
less harsh sound.
- THX standards decrease vertical dispersion of the front
speaker system, which should result in less distorting
acoustical-reflections from the floor and ceiling.
- THX specifies smaller front and rear speakers with
processing that re-routes low-frequency sound to a
A single source of low bass, the subwoofer,
simplifies the management of distorting low-frequency room
- THX adds 'Boundary Gain Compensation' that filters
excessive bass for seating near a room boundary.
- THX implements rear dipole speaker designs, which creates
a more-diffused, less localized sound.
- THX offers 'Adaptive De-correlation', which creates a more
spacious image from older rear channel sound mixes.
Interest in THX has waned in
recent years, while IMAX certification has risen as a new
Both seek to provide a commercial theater experience.
But IMAX differs in two fundamental ways.
1. The Speaker
THX prescribes the speaker specifications listed above.
IMAX home theater speaker certification seems based solely on
high fidelity performance.
I said "seems based" because I have yet to find specific IMAX
speaker specs. My conclusion is based on speakers that
have been IMAX certified.
2. The Picture
IMAX commercial theater screens are based on a curved 1.4:1 or
1.9:1 aspect ratio. An IMAX Blu-ray disc offers a
1.78:1 or 1.9:1 aspect ratio.
1.78:1 must crop the original height of the IMAX film on a HD
screen. 1.9:1 will require the return of black bars on
the TV screen.
Therefore, the ideal screen choice is a projector and
taller/larger projection screen with optional masking.
Given the IMAX and THX goal of providing a commercial theater
experience, large horn speakers, as used in theaters, should
also be considered.
Though not THX or IMAX
prescribed, a mid/tweeter horn array can broaden mid and
high-frequency dispersion from the front row to the
last. This is particularly true for a larger room with
many rows of seating. However, this design may also
sacrifice optimum performance at the focal point of the room,
which might be your seat. In any case, if you seek an
IMAX presentation and or accept THX assumptions plus concur
with their solutions, then employ a THX or an IMAX enhanced