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You've all seen the low mid and high knobs on cheap mixers (if you haven't, I provided a pic below).

To my knowledge, the low one corresponds to a low shelf filter, the high one to an hi-shelf filter and the mid one to a peaking filter.

What I was wondering was: what are the frequency bands these filters tipically affect? i.e.: if you see one of these mixers, what range of frequencies do you expect these filters to operate on?

mixer

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Moving this to AVP. Pretty sure the low and high knobs are usually around 80hz and 8kHz though. –  datageist Jan 25 '13 at 13:11
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I deleted the other one since this one has answers and the other did not. –  Friend Of George Jan 25 '13 at 14:34

2 Answers 2

up vote 7 down vote accepted

The Mixer pictured above, publishes its equalizer characteristics in the manual as: Hi- 13KHz Mid-1KHz Low-70Hz

with 6dB gain and infinite cut on all controls (infinite cut is questionable).

Typical controls have symmetric boost and cut.

Typically in this kind of eq system (having only 3 bands), the Hi and Low bands are implemented with shelving controls, and the mid control is a low Q bandpass filter. The filter skirts typically overlap at the 6dB rolloff points to offer a flat response at mid settings. To meet this goal (flat response) the frequencies listed by the manufacturer may be interpreted as corner frequencies for the Hi and Low bands and center frequency for the Mid band.

You should probably contact the manufacturer if you want exact specifications for these controls, or run a plot with each knob in each of the following (min, center, and max) positions to varify the manufacturer's eq implementation.

I had posted a general link to the typical three band tone control used on amps. The link was removed as the information was a bit off topic.

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Hi Bruce - that doesn't really help answer the question. First off, answers that are just links may suffer link-rot, and also the page doesn't actually provide the information requested - what are the typical frequency bands? –  Rory Alsop Jan 26 '13 at 9:58
    
Nonsense! Follow the link. The article explains in detail. The topical frequency bands are listed and plotted along with written explanation. I see no reason to regurgitate the work of someone else in my post. That would be silly and pointless. –  Bruce Zenone Jan 27 '13 at 14:43
    
But you do have a point. I misread the question as being more general and the amp tone stack is different than what is used in mixers. –  Bruce Zenone Jan 27 '13 at 15:39
    
Hi Bruce - that update makes much more sense - I was having trouble matching what was on that original page to the question. Upvoted! –  Rory Alsop Jan 28 '13 at 10:25

The typical values are going to depend entirely on what the subject on the channel is. It will be different based on what kind of instrument or tone of the voice being EQed. The full answer to this is probably beyond the scope of a QA format question as it is extremely broad and there are literally books written about the topic.

In general, you are trying to bring out both the tone and "crispness" of the input without making it sound distorted. The best way to figure out the ideal values is really to learn by ear. For voices, listen to what they sound like normally (without a mic) and try to get it to sound as close to that as you can through the system. For instruments, potentially use the same approach. Then, when listening to the mix as a whole, if a particular input sounds "muddy" try turning up the mid or high and if it seems to be hollow and lacking tone, try turning up the low or mid.

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I think the OP was interested in which frequencies a typical 3-band EQ acts upon, rather than the subjective topic of how to EQ something. –  JoshP Jan 28 '13 at 15:50
    
@Josh - oh yeah, wow, completely misread that. Oh well. –  AJ Henderson Jan 28 '13 at 16:10

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