Specifications

Metrics Tested on THX Speakers:
Axial Frequency Response Analysis
Directional Characteristics
Sensitivity
Impedance
Harmonic Distortion
Low Frequency Cut Off
Phase Angle
Stray Magnetic Flux
Maximum Output Level
Acoustic Noise Level
Polarity
Myth: "THX speakers only sound good for
one person in the room"
Reality: The opposite is true: while THX
speakers must have a narrow listening
window in the vertical to attenuate
reflections from the floor and ceiling, they
must simultaneously provide a VERY wide
horizontal listening window, ensuring good
sound for everyone in the room.
Starting with the more pedestrian facets of speaker performance, it almost goes without saying that THX
speakers must have no compromise in terms of neutral frequency response, power handling, output
capability, and the often overlooked dynamic, or transient, response.
Any good speaker should be able to make such claims.
THX speakers are designed as such and can, without
hesitation, be driven (by a THX amplifier) to reference
level. However, THX speakers go beyond this by
designing in certain features and characteristics which
put them in a position, as a system, to excel at
faithfully reproducing the program in that "living room
home theater" we keep talking about.
Main/Front Channel Speakers
THX Speakers have to meet very specific design goals in
terms of their radiation pattern: In the horizontal, they
must have a very, VERY wide listening window so that
everyone across the couch hears good sound. At the
same time they must have a limited, or narrow,
listening window in the vertical because reflections off
the floor and ceiling can smear and distort the sound in the time domain.
Again, back to THX realizing people will not likely acoustically treat their ceilings so that conventional
speakers can be used, recently (as of Ultra2) these requirements have changed in terms of emphasis (less
on vertical roll-off, more on off-axis linearity), but we'll talk about that when we cover Ultra2 a little
later.
The other major design characteristic of a THX speaker is that it is a dedicated satellite speaker which
REQUIRES the support of a subwoofer. The THX speaker system therefore is categorically a sub/sat
system.
Full-range speakers are nice. I love full-range speakers, but they have no place in a multi-channel sound
system if we want to have any chance of realizing a flat, uniform reproduction. Again, this goes back to
acoustics: it is very difficult to get a similar low end response from five speakers spread out through a
room, or even just three across the front of it, even if all the speakers are identical, because their
different physical positions in the room are going to result in different acoustical loading (i.e., the bass
response will not be the same from speaker to speaker). By summing all the bass in the sound track and
sending it to a subwoofer, or set of subwoofers (all getting the same signal), the system's reproduction of
bass from each channel will be uniform.
The other benefit of a sub/sat system, known by
experts such as Ken Kreisel long before THX and home
theater, is dynamics. By asking one amp and speaker to
cover the upper audible range (the main speaker) and a
completely different one the bottom, both do a better
job than either could if it was trying to do the whole
shebang.
Remember we said bass management was integral to
the THX controller, long before a time when it was
common in consumer equipment? Now we're getting to
the heart of that. These days, all processors and
receivers offer bass management, but what slopes do they use? What crossover frequencies are offered?
Will it all work with your speakers? If you have a THX Controller with THX speaker, you don't have to
worry about this. Your stuff will work together famously because it was designed as such from the
ground up.
For you Techies: