Home Theatre EQ'ing suggestions

Posted by erik olson on February 20, 1998 at 15:25:14:

In Reply to: You need the rest of the equipment to use equalizer 
correctly posted by MikeW on February 20, 1998 at 14:58:37:

I have a Rane THX44 EQ and I am quite happy with it.
Either it needs to be professionally calibrated or you need
a 1/3 octave spectrum analyzer and a pink noise source.
The EQ is utterly worthless without the proper tools and
knowledge on how to set it up.

EQ is not a cool tone control. It is for fixing specific
problems with the physics and dimensions of the room.

Audio Control also makes a THX EQ that looks nice.

The point of EQ'ing is to tame the problem of rooms modes.
Using absorbative materials, bass traps, moving the speakers to ideal
locations, ... all helps, but you can fiddle all you want but you
won't be able to completely cure the standing wave problem.
Anyone who says differently hasn't studied this problem with
several real rooms and doesn't know what they are taking about.
Heck, even Toole says EQ'ing out bass humps is good because
makes it easier on the amplifier which results in more
dynamic headroom. Why not take advantage of those room modes!!!

The sub woofer standing waves are the worst, but to 80 - 800Hz
range also makes quite a difference. Using and EQ on the subs
and front speakers really helps to blend the two.

The sub EQ on the Rane is 2 channels of parametric which I think
is superior to the 1/6 octave sub EQ on one of the THX
Audio Control EQ's. Both do the jobs but I really think
THX screwed up on there EQ spec, some rooms need more
than -6dB in the bass region, but they did this so
people couldn't hurt themselves as much.

The Rane oesn't have EQ for the surrounds but you can buy
the ME-22? 2 front channels from the THX44 or just
get a pro 31 band from Rane. The Audio Control has a 2/3 rds
octave section for the surrounds. Might work but I'd
prefer have 1/3 octave.

Can't wait to EQ my side and rear surrounds.
I think it'll make the timbre match better.
The THX average surround timbre matching curve is bunk.
Who has an average room? Dipoles on walls do weird things
to the freq response.

Also moderation is key here. Don't be too drastic on the
sliders, and average the response over a couple locations.
This is what the THX EQ document says and it seems like
a real good idea. Remember it is all about compromise.
You're EQing the direct and the reflected sounds, since
standing waves are all reflected sounds, fixing them
hurts the direct sound. Moderation, compromise, average.

erik olson


Posted by erik olson on February 23, 1998 at 15:56:23:

In Reply to: Re: You need the rest of the equipment to use equalizer
correctly posted by Michael A. Sills on February 21, 1998 at 12:14:43:

: At the end of the day, one has to subjectively
: judge whether the compromise ultimately arrived
: at is an improvement. Even more subjectively, one
: generally also decides whether the magnitude of
: the improvement (if any) justifies the expense.
: In my case, after initial enthusiasm for it, I
: ended up returning the Rane.

Good point, it is an investment for the EQ itself ,and
the analyzer, and time required to learn how to use
it. That all adds up.

: While I think it
: can definitely improve some system/room interfaces,
: it is not a panacea that will please everyone who
: tries it. Just my two cents.

I have to disagree. The good of EQ'ing 160Hz and
up I have to admit is debatable. Since EQ'ing effect
direct and reflected sound at lot of harm can be done
to the sound. But for the below 160Hz range, I believe
EQ'ing works wonders. Bass really isn't reflected,
it is more of a standing wave situation. So with
bass it isn't a reflected vs. direct dilema, it is just
a room pressure issue. All rooms have standing wave
humps, some more than the -6dB that the THX EQ's allow
too! These standing waves can dramatically change
the tonal natural of any subwoofer. Actually I 
believe the room plays more of a role in the
bass response than the subwoofer does!!!!! That
is off course assuming you have a decent quality
sub to begin with.

Also turning off the LPF and HPF of the sub and the
front channels of the crossovers in the DC-1 allow
you to EQ into the "blending zones". Yes the sub
cross in the DC-1 has a 24dB/octave roll-off typically
at 80Hz, but EQ'ing it up one octave past the -3dB
point I feel does wonders for blending the sub to
the satellites. Same is true for the front speakers
with their -12dB/octave rolloff.

Only allowing -6dB cuts in the sub woofer channel
and only allow EQ'ing up to and not past the F3 zones,
in my opinion is a mistake Tomilson Holman made when he
wrote the THX EQ spec that Rane and later Audio Control 
followed. You really need to be able to EQ one
octave past the F3 cut-off frequency. Surprisingly
this rule is also followed by some professional
speaker builders in that they like the F3 frequency
cut-off to be one octave away from the crossover
frequency they choose for their mid-range or tweeters.

Still a THX EQ is a good bargin and its also nice and
compact. The best solution in my opinion is to go with
a 31 band pro EQ for each channel. But with quality
constant Q equalizers that will run you about $4000 for
a 7.1 setup! Is it worth it? Good question, it won't be
as good of a value as that DC-1 was to purchase! Thats
for sure.



Posted by erik olson on February 20, 1998 at 21:07:14:

In Reply to: Re: You need the rest of the equipment to use equalizer 
correctly posted by erik olson on February 20, 1998 at 15:25:14:

Here are a couple comments I wanted to add to what I said:

: Audio Control also makes a THX EQ that looks nice.

I prefer the Rane, they are known for their build quality 
and Rane has an excellent reputation in the pro EQ market.

: The Rane oesn't have EQ for the surrounds but you can buy
: the ME-22? 2 front channels from the THX44 or just

Opps, the SSE-22 is the Rane model I meant.
I think the ME-22 is the 31 band pro EQ that also is an option
for two channels.


Someone asked:
> How much money are we talking to get an equilizer
> that would do a decent job with all 5.1 channels?

The THX44 is about $1200 but that is only for the 3 fronts and sub.
The SSE22 for the surrounds is about $500. And you will probably want
two of them since I think you are 7.1? Is that true?

So about $2200 for a Rane 7.1 setup.

Someone asked:
> Are spectrum analyzers out of the question to
> purchase also?

You can buy a cheap-o-one for about $400, but I'd spend the extra
for the $1000 Audio Control unit. You really should get one with 
averaging, but those cost thousands.

Also a spectrum analyzer on a PC is an option, but software plus
calibrated mic will probably cost you about as much as a separate box.
I like having a separate box, it is more convenient for me.

Most important thing is learning how to properly use it, you have to 
be dedicated to the quest and try to read as much as you can on the
subject. Hiring a professional to calibrate it could cost you a couple
hundred bucks, or maybe the store you buy it from will come out and
calibrate it for free, some do that.


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