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Author Topic: What hipass filter to use  (Read 5605 times)

John L Nobile

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Re: What hipass filter to use
« Reply #10 on: June 14, 2016, 10:32:55 am »

Whatever happened to "close enough for rock and roll?"
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Ivan Beaver

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Re: What hipass filter to use
« Reply #11 on: June 14, 2016, 11:19:12 am »

Whatever happened to "close enough for rock and roll?"
Or Jazz-------
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Ivan Beaver
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Frank Koenig

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Re: What hipass filter to use
« Reply #12 on: June 14, 2016, 07:44:15 pm »

Filters named after people are useful mathematical abstractions that possess certain properties, such as maximally flat magnitude (Butterworth), equal-ripple pass-band magnitude (Chebyshev), or maximally flat phase (Bessel). For our practical purposes, where they are cascaded with the unruly transfer functions of loudspeakers, I see them as somewhat arbitrary stopping points along a transition rate (from pass-band to stop-band) continuum. There is nothing sacred about Butterworth filters, just as there is nothing sacred about exponential horns.

Folks not conversant in filter design might find it useful to look at the frequency and time responses of second order filters, which have the property that the transition rate is a single parameter, often represented by "Q" or a lower-case zeta. First order filters all have the same transition rate, so they're boring, and third and higher order filters have more degrees of freedom that make their behavior complicated. Second order filters are a nice pedagogical case.

Not surprisingly, filters with sharp transitions in magnitude have correspondingly sharp transitions in phase (all are minimum phase) and impulse or step responses with much ringing. Filters with slow transitions have less ringing.

--Frank
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Ivan Beaver

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Re: What hipass filter to use
« Reply #13 on: June 14, 2016, 09:23:19 pm »

There is nothing sacred about Butterworth filters, just as there is nothing sacred about exponential horns.


But L/R filters used to be sacred (as in every crossover used them as standard).

Funny that they were popular at the same time as exponential horns--------
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Alex Rigodanzo

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Re: What hipass filter to use
« Reply #14 on: June 14, 2016, 09:51:40 pm »

But L/R filters used to be sacred

They still are to some of us who "grew up" with them and don't "know no better".  Like many other things discussed here, they're such an insignificant link in a chain full of pitfalls that can actually be audIble. I guarantee exactly ZERO people in any audience can "hear" your choice of filter.
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Frank Koenig

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Re: What hipass filter to use
« Reply #15 on: June 14, 2016, 10:44:05 pm »

But L/R filters used to be sacred (as in every crossover used them as standard).

Indeed. L/R makes for a "perfect" crossover -- as long as there isn't a speaker involved  :P
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Ivan Beaver

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Re: What hipass filter to use
« Reply #16 on: June 15, 2016, 10:01:28 am »

Indeed. L/R makes for a "perfect" crossover -- as long as there isn't a speaker involved  :P
Or if you use "perfect speakers".  Which we don't.
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Alex Rigodanzo

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Re: What hipass filter to use
« Reply #17 on: June 15, 2016, 12:39:56 pm »

So please enlighten me, what is the AUDIBLE issue to listen for with L/R?  That's all I've used since I put together my first DJ rig in 1990 (TDM xover, Peavey Deca amps, homebrew cabs)
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Ivan Beaver

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Re: What hipass filter to use
« Reply #18 on: June 15, 2016, 01:09:49 pm »

So please enlighten me, what is the AUDIBLE issue to listen for with L/R?  That's all I've used since I put together my first DJ rig in 1990 (TDM xover, Peavey Deca amps, homebrew cabs)
It depends on a number of factors.  How flat are the cabinets above and below the crossover point for one?

If they are flat (most aren't) then LR filters will sum together to provide a flat response.

If they are not flat (most cabinets), then you could have a hump in the response or a dip-it depends on the particular cabinets.

It also depends on whether or not you can separate the filters (high and low pass being different freq).

And then the phase issue comes into play.

It is not just the phase of the filter combination, but also the phase of the particular drivers that combine with the filter phase.

Without specific details, it is hard to say what the end result was.

And yes-I was there and did the same thing as everybody else.  We didn't have much choice back then
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Alex Rigodanzo

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Re: What hipass filter to use
« Reply #19 on: June 15, 2016, 10:57:07 pm »

Ok, but since most live rock/pop/country etc, the subs are typically run about 10db higher than the tops, is this really relevant?  And for an hpf on the subs, you're not crossing over to another speaker so again, is it relevant?
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Re: What hipass filter to use
« Reply #19 on: June 15, 2016, 10:57:07 pm »


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