Common HT mistakes/misconceptions
Here is a list of common Home Theatre (HT) mistakes / misconceptions that I've
seen, heard, done, or once thought myself:
- Subwoofers and surround speakers are too loud.
Calibrate them with a SPL meter and a noise source.
When people first get into HT they are all excited about their new toys so
they have a tendency to crank the levels for the subs and surrounds way
too high. I've seen instances of subs being +20dB louder than they should!
- TV's set to the cool color temperature.
The "warm" setting on most TV's is much closer to the 6500 degrees K
level that most people consider "standard".
So set it to "warm" or better yet hire an ISF technican to come
out and calibrate your TV.
- Surrounds blasting in the ears.
This is just plain obnoxious, especially when their volume levels are also too
high. Put those surround speakers higher up and farther away. You don't want
to be easily distracted by surround effects. Envelopement should be the goal.
- Turn the sharpness on your TV down.
Sharpness is bad, it causes ringing, and in excess it actually lowers the
resolution instead of increasing it!
So turn it down or better yet get Video Essentials and calibrate your TV
yourself! Caution on Sony TV's, turning sharpness down to its lowest point
engages a smoothing / blurring filter that totally trashes the picture,
keep it a notch or so above the last tick and this "feature" will remain off.
- Too much ambient light washes out the picture.
Close the drapes and turn off the lights, make it dark.
You'll see more picture detail and complete darkness will make it more of an
event. Rear projection televisions (RPTV's) like darkness, front projectors
require absolute darkness. Remember on a FP, the blackest black is only as
dark as the white of the screen (ambient light hitting it). So the darker
the room the blacker the darkest black.
- Not having enough subwoofers.
Getting a sub that can play 20Hz at the 105dB C reference level is no easy
task. Dolby and DTS upped the ante with discrete digital multi channel audio.
DTS and AC3 both are 5.1 and have the LFE (low frequency effects) channel
which has +10dB more dynamic range than than the 105dB reference level.
That's 115dB of bass. To play 20Hz at 115dB will require 4 high quality
18" drivers in a sealed enclosure. Personally I'd want to go an octave below
that to 10Hz. Fact is that you never can have too much bass!
Check out my piston excursion calculator to
get a feel for how low frequency high dB SPL's are a function of cone excursion.
- Bad room layout symmetry.
Not having the TV centered or having the front speakers all akimbo is a
very common mistake. Putting the TV in the corner is bad.
Putting the left front speaker on the floor and the right front on
top of the bookshelf is bad. Putting those satellite sized surround speakers
on the floor behind the plant is bad. Most of us can't have a dedicated movie
room, usually a room needs to maintain its multifunctional value. While many
home theatre compromises are a fact of life, lack of symmetry is one
compromise that is not allowed. Having to turn your head to view the TV is
bad. Also a fairly reasonable 2 channel stereo image is a good starting
- Bad subwoofer placement or sub not EQ'd.
Many subwoofers have been described as slow, loose, boomy, or mushy.
Unfortunately quite often this has been because of improper setup.
Yes, even a few "professional audio journalists have been guilty of this
mistake." I'm not talking about different subwoofer design methodologies.
Granted sealed and vented alignments sound different. What I am talking about
is more dramatic and much more of a problem. Room modes are the cause,
experimenting with layout or bass equalization is a cure.
This is not a simple solution, knowledge and patience are key here.
Read up on the subject as much as you can.
My room modes calculator is a good tool.
- Shrill high end hurts my ears.
In my opinion the most important part of a THX receiver/pre-amp is the
THX re-equalization circuitry.
It rolls off the high frequencies because movies are mixed too bright.
This is because movie theatres are big open spaces and the speakers are
behind the screen.
Movies can be painfully bright if you don't account for some sort of high
frequency gain reduction. THX has been licensing its "Re-EQ" name/technology
to manufacturers, so look for this badge or just buy a THX receiver/preamp.
A good example of this painful shrillness is the Wow! disc, when Darth Vader
throws the emporer into the pit in the Death Star. When played back at loud
volume levels this couple second scene is painful without re-equalization.
- THX speakers are just fine for music.
Because of a THX speaker's horizontal radiation pattern many high end
audio journalists have been slamming THX speakers by saying that they
don't sound good for music.
These same journalists hype up front bi-pole speaker and electrostatic
headphone technology like it is the greatest thing since ...., you know.
So a bi-pole radiating sound at the backwall is OK while THX speakers
radiating less sound towards the floor and ceiling in not. NOT! These audio
journalists must not be listening to the same kind of music I listen to
in order to make such a claim. Listen for yourself and buy the speakers you
like. For more information read the
controversy about THX speakers and music.
- Dipole surround speakers work better than direct radiating
The dipole vs. direct radiating surround speaker debate is a hot and flamable
topic. Many opinions differ on this topic and one speaker manufacturer has
even made a "tripole" surround speaker that is a mix of direct and dipole.
Some people even swear by bipole surrounds.
So why do I think dipoles are better?
- Dipoles are a closer match to the surround speaker arrays found in movie
- Studios mix movies for movie theatres, not home theatres. This trend
does not look like it is going to change.
- Ambience and envelopment are the goals of surround speakers not 3D
holographic rear stereo images. Dipoles do a better job at envelopement due
to the sound being directed away from the listener. Having the forward and
backwards firing sounds out-of-phase, which is the difference bewteen a dipole
and not a bipole, makes the speaker harder to pinpoint.
- The surround speakers should not distract and attention away from the
screen. As Mr Holman says "they should help to draw you into the film."
- Dipoles have a bigger surround sweet spot than direct radiating
- Read some of my rantings on the
issues of surround speaker height and the dipole question.
- Putting the center channel speaker behind the TV.
The resulting sound is 100% reflected and 0% direct. "Di" and "bi" pole front
speakers are one thing but putting the center channel speaker behind the TV
is an altogether different level of sound degradation. It will muddle the
sound and trash the intelligibility. This is about as non THX in concept as
you can get. Some audio journalists actually recommend doing this.
- A center channel that has a sonic coloration different than the L and
Having matched LCR speakers is important since most movie sound comes from
the front. When the center channel isn't sonically matched; pans and
dialogue will seem un-natural. So using "any old speaker" for the center
channel is not a good idea. Many speaker companies have jumped on the center
channel bandwagon, some centers are good matches for a company's brand of main
speakers, others aren't. I tend to like the THX style of perfectly matched
centers that are identical to the L and R mains. In any case, matching drivers
are necessary and watch out for ported center speakers of different sizes than
Use caution, trust only your ears. Be aware that placing a speaker on top
of a TV does change the sonic qualities due to room physics but that is
a different problem with a different solution (see EQ).
- Placing a subwoofer next to the couch that is in the center of the
Putting a subwoofer in the center of a room is the worst possible place you
could put it. Some people think it is cool to use their down firing subwoofer
as an end table. I've heard of someone having two Velodyne ULD-18's, one on
each side of the couch that is in the middle of a large room, away from all
walls. This person even put thick granite slabs on top of the subs as a tweak.
And they wondered why the bass sounded weak? While it might look cool, the
reason this is bad is because putting a sub in the center of the room doesn't
take advantage of any of the side or corner loading. More output could of
been achieved with one ULD-18 placed in the corner, and at $3000 a pop that
is some savings. Since useable output at 20Hz is always a premium and
requires significant cone excursion, it is always a good idea to take advantage
of room gain whenever possible, even if you have to EQ down any humps. The
reason is that you never can have too much bass headroom and the center of the
room gives you the least. If you don't like the corner, then put it against a
wall and you still will get some gain. And some gain is always better than no
- Even owning a VCR!
A device of such poor video fidelity has no place in any respectable home
Ultimate HT equipment additions
- Unfortunately Prologic just doesn't cut it anymore. If you have DVD
then you really need a Dolby Digital (AC3) receiver / pre-amp / decoder.
- More amplifier power. You never can have too much wattage.
Excess amplifier power increases headroom and prevents distortion and clipping
which can destroy speakers. It is my opinion that the major differences
heard in amplifier reviews are based on different clipping sounds, it is just
a variation of the tube vs. transistor argument. So more watts means
clipping is less likely to happen and chances are it will be less audible.
How much power? I'm talking kilowatts and having your own PG&E feed.
- Third octave equalizer or parametric EQ for the subwoofer and the front
speakers. An EQ for the surround is also a good idea too. You will need a
pink noise source and a spectrum analyzer
to properly setup an EQ. An EQ is not a toy and it is not a fancy set of tone
controls. Think calibration.
- Go 7.1 channel. 3 fronts, 2 side, 2 rear, plus sub. The result is
improved ambience/envelopement and special steering logic enhances the front
to rear pans. You now feel surrounded. Also prologic encoded films can be
made to have increased rear channel separation like AC3 with some processors.
Check out the Lexicon DC-1 and the Merdian preamps. Not to be confused,
Yamaha's 7 channel side fills are something else altogether.
- DTS, can you hear a difference? I can. Jurrasic Park, Vertigo, and the
English Patient all sound awesome. Despite the level mismatch of the LFE
and the surround channels there is a subtle difference between DTS and AC3.
Listen to voices and high frequency foley effects for the clues.
The difference is subtle.
- Front Projector and a line doubler (or quadrupler).
Check out my quest for the FP page.
- Tactile Transducers, feeling the bass is better than just hearing it.
Caution though, tactile transducers have some tricky problems that need to be
overcome. Check out my bass page and look for the
Tactile Transducer FAQ.
- Enough subs to be able to play 14Hz at 115dB!
- Wipeout XL, Doom 64, or Goldeneye on a big screen played loud.
It simply rocks!
- Three foot thick concrete walls for your HT bunker, this way you can
play at 0dB levels without annoying your neighbors and in case of enemy
bombardment you are covered there too!
Check out my home theatre tips page.