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Old 20th July 2004, 08:50 AM   #1
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Default Why is active equalization "bad"?

I'm not trying to fill the forum with my posts or anything, but questions generate more questions and... I hope I am in the right thread.
This one is on my mind for a long time: why is considered active equalization "bad"? Or, worse than passive equalization at least. The mentioned reason is the phase response, but, from my modest knowledge, phase response depends only on filter type/order, where type means Bessel, etc, not active/passive. The same transfer function can be obtained with a passive filter, or an active one. What am I missing here?
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Old 20th July 2004, 10:46 AM   #2
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Hi,

Quote:
why is considered active equalization "bad"
Is it?

Well, the two questions "Why is active equalization considered bad?" and "Is active equalization really bad?" are actually two completely different topics, I think.

I don't consider active signal manipulation worse than passive. Actually, I prefer the "active" way in order to avoid the complex and difficult behaviour of capacity and inductivity depending on the loudspeakers (complex) impedance.

IMHO the prefered use of filtering should depend on the actual purpose. E.g. a simple notch or boost filter to correct a tweeter's response doesn't neccessarily need an opamp circuit (yet can be done with only two inexpensive passive components).

To conclude that and contribute to your question, I'd say:

I consider unneccessary (e.g. too much, too expensive, too difficult to implement) equalization bad.

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Sebastian.
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Old 20th July 2004, 10:46 AM   #3
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hi

push - pull i have missed out on some topics - by your active equalisation are you referring to

1 - active c/overs to passive c/overs

2 or active tone control circuit to a passive tone boost circuit

3 or to usage of parametric / graphic equalisers etc.

suranjan das gupta
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Old 20th July 2004, 10:51 AM   #4
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I think, push-pull is trying to find the best way to implement a newly developed crossover filter design here: http://www.diyaudio.com/forums/showt...736#post439736
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Old 20th July 2004, 11:01 AM   #5
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Quote:
Originally posted by hunter audio
hi

push - pull i have missed out on some topics - by your active equalisation are you referring to

1 - active c/overs to passive c/overs

2 or active tone control circuit to a passive tone boost circuit

3 or to usage of parametric / graphic equalisers etc.

suranjan das gupta
Well, the question is as general as it can be.
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Old 20th July 2004, 12:38 PM   #6
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Default Re: Why is active equalization "bad"?

Quote:
Originally posted by mr_push_pull
I'm not trying to fill the forum with my posts or anything, but questions generate more questions and... I hope I am in the right thread.
This one is on my mind for a long time: why is considered active equalization "bad"? Or, worse than passive equalization at least. The mentioned reason is the phase response, but, from my modest knowledge, phase response depends only on filter type/order, where type means Bessel, etc, not active/passive. The same transfer function can be obtained with a passive filter, or an active one. What am I missing here?

In the professional ranks active EQ is not considered bad; it is the standard. When the only form of active EQ available was analog circuitry it was not embraced because it was noisier and had more problems with phase than passive circuits. Digital EQs do not have those shortcomings and digital EQ is rapidly driving passive crossovers and correction circuits from the scene. In the most current high end speakers for professional usage (speakers $10k and up) passive crossover and correction circuits no longer exist.
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Old 20th July 2004, 10:01 PM   #7
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I don't think active EQ is bad. There are bad active EQ's however, and I think thats where the problem lies. In case your looking, the Ashley protea digital EQ is a very good one as far as sound quality is concerned.


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Old 20th July 2004, 10:08 PM   #8
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any crossover which doesn't take into account phase differential is going to be problematic. If you just take the cookbook formulas from Lancaster or Tedeschi's book (or the interactive websites at Analog Devices or Filter Pro from Texas Instruments) you might get an XO which looks pretty on paper, but which doesnt' sit nicely with the operative drivers.

Nelson has a good white-paper on the Pass Labs website -- less is (maybe) more.
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Old 20th July 2004, 10:30 PM   #9
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Nothing wrong with Active EQ in the low registers, it's the Midís and Highs that have a problem with all Equalization if you use too much or donít know what you are doing. At least that my understanding of it.
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Old 21st July 2004, 06:19 AM   #10
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Default Re: Re: Why is active equalization "bad"?

Quote:
Originally posted by BillFitzmaurice



In the professional ranks active EQ is not considered bad; it is the standard. When the only form of active EQ available was analog circuitry it was not embraced because it was noisier and had more problems with phase than passive circuits. Digital EQs do not have those shortcomings and digital EQ is rapidly driving passive crossovers and correction circuits from the scene. In the most current high end speakers for professional usage (speakers $10k and up) passive crossover and correction circuits no longer exist.
OK, this clarifies most of my questions, the ephasis should've been put on "considered bad". This is what I thought too, a digital filter doesn't have the phase problems of analog filters, why shoudl digital equalizing be bad?
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