will and eq do?

Posted: Sun Sep 16, 2007 5:24 pm

A question:
If I have a build up of a certain frequency in my control room, that is building up right at my sweet spot, can I insert a simple 1/3 octave eq and cut the frequency until the build up has been lessened? Or is my only option to kill the frequency (or frequencies) by acoustically treating the room?

Posted: Sun Sep 16, 2007 7:45 pm

Can you use an EQ to do this... sure. SHOULD you do a cut with an EQ... maybe, but probably not.

(I would not put the EQ in as an insert (per se') but in line (series) with your monitors. (Not sure if you really meant as an insert or not))

The real problem is that with virtually any/every EQ you put in the audio signal path WILL induce phase shifts. Depending on the frequencies involved, how much of a build-up, etc... the phase issues can be minimal to almost catastrophic.

I would try a high end parametric and see what the results are.

After that... you'd be better off treating the room, IMHO.

Posted: Sun Sep 16, 2007 10:50 pm

That is pretty much what I figured...

Posted: Mon Sep 17, 2007 6:28 am

This is off our education page which Rod had wrote. I think it pretty much answers your question.

EQ VS. ROOM TREATMENT

There is a trend that is growing in popularity – with the speaker manufacturer’s jumping onto the bandwagon, and that is the use of Narrow Band Parametric EQ for dealing with modal issues in listening rooms.

I would stress to you that this is not an effective manner in which to deal with these issues.

The concept is this: an analysis is made of the room effects at the microphone location. If the analysis were to indicate (simply as one example) a 10dB peak at 40Hz you would apply a narrow band inverted signal at 40Hz, increasing in amplitude, until the 40Hz signal leveled out.

This is fine for amplitude – but doesn’t deal with ringing (which is the reverberation effect of the room itself). That also has to be dealt with in order for the room to translate your music into exactly what it was you recorded – and the effects you are adding during mixdown.

By the way – 10dB is about the maximum adjustment you can make through the use of PEQ – and it isn’t unusual to see peaks in the area of 20 or even 30dB.

Likewise for dips, you would apply a boost to the signal - but in the case of dips – boosts are generally even smaller – a maximum of 3 to 6dB (depending on the manufacturer of the speakers. Some manufacturers don’t even add boost for dips because they realize that this can be problematical.

If you should happen to be sitting in a true null………. You would actually be experiencing a case where the signal amplitude is 0dB – in which case a 100dB boost would still leave you with 0dB in signal.

The bottom line is this – after dealing with all of this through PEQ – you will find (in the end) that you still have to apply room treatments to tame down the room as a whole, to deal with all the other issues that exist – and once you apply them, you will screw up everything you did with the EQ’ing of your system.

So save yourself a lot of time and effort and treat your room properly to begin with – use PEQ after treatments, mostly to fine tune your speakers themselves.

Hope that helps,
Glenn

Posted: Mon Sep 17, 2007 6:33 am

Switchblade,

you can (indeed) kill it at your sweet spot - BUT - does this mean that the signal (left) at your sweet spot is going to be what you want in your mix? Remember that you are changing this globally.

Suppose you are sending out an 80dB signal at this particular frequency - and the boost takes it to 90 dB - you can cut it to 80 at the listening spot - but then it is probably around 70 to 71 coming out of the speaker - and is this where yuu need it in your mix? Not if it is supposed to be the original 80dB.

PEQ works for rooms where you are listening to finished products - it does NOT work for rooms where you are producing them.......... and even then - it's limited to about 10dB cuts off peaks and you can't do a thing for nulls using PEQ...........

In a control room - a mixing room - you have to fix the room so you can hear what is coming out of your speakers............

I don't disagree with Max often - but this is one of those times that i have to........

Rod

Posted: Tue Sep 18, 2007 5:17 am

Rod,

I don't think we're really that far off from each other... (the student says to the teacher) If I'm wrong, I'm wrong and you KNOW I hate spewing off bad info!

I was under the impression from a couple of threads in which you and Eric discussed that if there was an isolated frequency which was problematic, that it could POTENTIALLY be dealt with by using a narrow Q parametric to minimize it's effects... but that it should be checked for phasing.

AND!

That in ALL cases adding an EQ indeed did cause phasing issues, but the relative amount of phasing may be insignifcant in the overall scheme.

But IIRC the final outcome was that these would be somewhat rare occasions and that it usually ended up better to just fix the room.

Sorry about not making that point clearer.

Posted: Tue Sep 18, 2007 9:22 am

Max,

In any case you cannot do anything (with PEQ) to correct a dip or a null.

The more that I have thought this through - in the case of a mixing room - the more i realize that it cannot work - even if it does make it "sound" right.

the one thing that is critical is that you hear what is coming out of your speakers - and thus correction of that signal is not acceptable to get a comfortable listening range in any particular frequency.

I say this because it still puts you in a position where you have to make it sound wrong to make it translate right.

I only accept this approach in critical listening rooms - ones where it doesn't matter becuase I am already listening to the finished product - and not trying to produce it.

You always need to "learn your room" to correct for anomolies - why then bother to change them to a different anomoly that you need to correct for?

For Control/mixing rooms- the only correction that is meaningful is to treat the room to make the anomolies go away.....

Sincerely,

Rod

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