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Crossover cascading
julf
post Apr 16 2013, 11:58
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QUOTE (Nessuno @ Apr 16 2013, 12:33) *
Or the other way around: if (as the OP said) the first one is a low-pass with -3dB @600Hz, it most likely will be flat @80Hz (and add no phase shift).


Ah, yes, my fault - thought the 600 Hz filter was a low-pass too.

Pretty confusing, as the OP was first talking about a 400 Hz and a 100 Hz crossover, then 2 80 Hz crossovers, then an 80 Hz crossover and an unspecified 2-way speaker crossover, and then an 80 Hz unspecified filter and a 600 Hz unspecified filter.

I also notice that the OP hasn't answered our clarifying questions.

I think we have to conclude that either the OP isn't quite sure about what he/she is asking, or isn't interested in finding out the real answer.
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dhromed
post Apr 16 2013, 12:36
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Even after this thread I'm still not sure what is meant in this particular case by "cascading" filters. Does that simply mean "put one filter after another"?
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Nessuno
post Apr 16 2013, 13:01
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QUOTE (dhromed @ Apr 16 2013, 13:36) *
Even after this thread I'm still not sure what is meant in this particular case by "cascading" filters. Does that simply mean "put one filter after another"?

I think this was what the OP meant: put them in a series and determine what happens to a full band signal passing through it.


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julf
post Apr 16 2013, 13:42
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QUOTE (Nessuno @ Apr 16 2013, 14:01) *
I think this was what the OP meant: put them in a series and determine what happens to a full band signal passing through it.


I think that is what we are all assuming, but it would have been helpful if the OP had replied to my request to specify what he/she meant with the term.
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Speedskater
post Apr 16 2013, 15:02
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As a side note: Understanding Decibel math is no easy matter, Henry W. Ott in his 850 page very technical book 'Electromagnetic Compatibility Engineering' has a 5 page Appendix on understanding and using the Decibel.

He also has a short overview on his web-page.

http://www.hottconsultants.com/techtips/decibel.html


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julf
post Apr 16 2013, 15:34
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QUOTE (Speedskater @ Apr 16 2013, 16:02) *
As a side note: Understanding Decibel math is no easy matter


It is actually pretty easy if you grew up with logarithms and slide rules (we needed those to fend off the dinosaurs, you know).
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greynol
post Apr 16 2013, 16:07
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We experience much of the world logarithmically. Going at it this way I think it's the multiplication part that is the hard part to understand. The other problem at hand is the use of the word interact in conjunction with the concept of isolation, though this was explained by julf already: if the filters are isolated then they won't interact with one anoher by changing the way in which each other functions. Instead they will act independently and their effects will combine no matter how minuscule or how large.

To insert what will likely be my unwelcome opinion, I hate it when members use our forums to argue by proxy. This is especially shown here when someone is giving advice about a subject he clearly does not understand and then gets annoyed when this is pointed out, likely because it is compromising his credibility. Google the OP's nick and the relevant terms and you will get hits at two other forums.

Someone please explain how a 12db/octave filter of any variety will attenuate 80 Hz by 96dB when the corner frequency is at 600 Hz. Assuming there is no additional attenuation, the math simply does not add up.

This post has been edited by greynol: Apr 16 2013, 17:38


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Yahzi
post Apr 17 2013, 13:47
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The question I asked was "can the speaker crossover be affected by the receiver crossover" and it appears the answer it no, it shouldn't given the crossover frequencies in question are too far apart to interact. The slopes would be too far apart.

I used the examples of 80 Hz or 100 Hz to get my point across. The slope at 80 Hz and the passive crossover of the speaker at 500 hz or 800 Hz or 1 kHz for the woofer - WHATEVER it is, the AVR crossover can't affect it positively or negatively as far as I understand it. Much of what had been posted was sidestepping the questions I posed.
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Yahzi
post Apr 17 2013, 13:49
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The person I was discussing who claimed the passive crossover elements in the speaker still cascade with the receiver crossover, THAT is what I wanted to know. From what I know, this generally can't happen.
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dhromed
post Apr 17 2013, 14:38
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What do you mean by cascade?
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knutinh
post Apr 17 2013, 14:53
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QUOTE (dhromed @ Apr 17 2013, 14:38) *
What do you mean by cascade?

I take it to mean "if multiple units are connected in series, will the output be affected by only one component, or all components". The answer is that the output will be affected by all components.

If you AVR has room correction, I would try using it. If it is any good, it should align phase along crossover-points no matter what filtering is applied later on.

Passive loudspeaker crossovers tends to be designed tightly with the loudspeaker - both filters and both drivers (for a 2-way unit). They can be part "ideal, theoretical filtering", and part phase/eq correction adapted to loudspeaker drivers/enclosures.

Active loudspeaker filters should probably be designed by the loudspeaker designer, or based on good measurements and some target response.

-k
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Propheticus
post Apr 17 2013, 15:06
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If the two slopes are in the same range they will add up... the resulting slope will be a product of both (steeper slope). If they are far apart.... either one is useless but won't affect the other.

The way I see it:
If your AVR cuts of from lets say 100Hz and the slope is below -96dB at 150Hz and your sub cuts from 200Hz....there's nothing left to cut. The other way round the AVR would cut of a piece of the range which is then followed by the sub cutting of more. You then might just as well disable the AVR filter, because the result is the same.
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julf
post Apr 17 2013, 15:14
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QUOTE (Yahzi @ Apr 17 2013, 14:47) *
WHATEVER it is, the AVR crossover can't affect it positively or negatively as far as I understand it.


Then you have totally misunderstood what allmost of us have been saying.

This post has been edited by julf: Apr 17 2013, 15:15
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julf
post Apr 17 2013, 15:16
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QUOTE (Yahzi @ Apr 17 2013, 14:49) *
The person I was discussing who claimed the passive crossover elements in the speaker still cascade with the receiver crossover, THAT is what I wanted to know. From what I know, this generally can't happen.


Again, can you *please* define what you mean by "cascade"? The output will be affected by both filters.

This post has been edited by julf: Apr 17 2013, 15:17
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dhromed
post Apr 17 2013, 15:26
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QUOTE (knutinh @ Apr 17 2013, 15:53) *
I take it to mean "if multiple units are connected in series, will the output be affected by only one component, or all components". The answer is that the output will be affected by all components.


I figured it would mean that in this particular case the two lowpasses will simply superimpose and the final result is always the one with the tightest filter. Therefore, stacking the two LPF's would be harmless as they will "cascade".

But Arnold's usage in his first post clearly means "put the filters in series", which is very different.

I'm also not entirely sure any more what Yahzi's position is. In the OP he warns that the filters will affect eachother, but later he doesn't believe that they will affect eachother anymore.

In any case, Arnold said that stacking the filters will have undesired consequences, so it appears that Yahzi is right and his friend is wrong, but for the wrong reasons.
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krabapple
post Apr 18 2013, 04:37
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QUOTE (dhromed @ Apr 16 2013, 07:36) *
Even after this thread I'm still not sure what is meant in this particular case by "cascading" filters. Does that simply mean "put one filter after another"?


Cascading filters is a common enough term in popular audio literature -- it's what happens when you have bass management happening in your AVR (applying a low pass filter with a crossover frequency of X hz to the signal, and directing the output to the subwoofer channel) AND your subwoofer applies its own lowpass filter too. Typically one is advised to turn off the LPF of the sub, or set the sub's crossover frequency to maximum (which hopefully is well above the crossover frequency used for the AVR's LPF).

This post has been edited by krabapple: Apr 18 2013, 04:39
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Yahzi
post Apr 19 2013, 14:15
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QUOTE
I'm also not entirely sure any more what Yahzi's position is. In the OP he warns that the filters will affect eachother, but later he doesn't believe that they will affect eachother anymore.


I agree that two filters will combine or cascade if operating within the same range. If a 80 Hz low pass was operating with a 100 Hz low pass then I imagine there would be a phase shift of some kind. But there should be some interaction of some kind with the filters so close to each other.

What I disagreed with is the idea that a speaker crossover could be affected by the receivers own crossover, which is what my friend was saying. But I do not disagree that filters can combine if operating in the same range.
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greynol
post Apr 19 2013, 14:58
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They combine regardless of whether they operate in the same range, FFS!

Here's a question to ponder: what if the content creator includes material in the LFE channel that has frequencies well above the x-over in the sub which the AVR doesn't filter out because it isn't part of that AVR's bass management?

This post has been edited by greynol: Apr 19 2013, 15:27


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pdq
post Apr 19 2013, 15:21
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How about this explanation:

If the crossover frequencies of the two low pass filters are far apart then one of them will make no audible difference over the effect of the other. Only if they are fairly close together will the addition of the second filter make an audible difference over the other one by itself.

The lack of an audible difference does not mean that the second filter has NO effect.
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julf
post Apr 19 2013, 16:17
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QUOTE (Yahzi @ Apr 19 2013, 15:15) *
I agree that two filters will combine or cascade if operating within the same range.


And how do they know if they operate in the same range or not? If nobody tells them, they might just not realize they aren't supposed to combine...

Seriously, one more time - they *will* combine in *any* case. That result might not cause an audible difference if their ranges are far enough apart. That doesn't change the fundamental fact that they do combine, even if you don't want them to.

QUOTE
If a 80 Hz low pass was operating with a 100 Hz low pass then I imagine there would be a phase shift of some kind.


Not only that, but the steepness of the response curve would be pretty much twice the steepness of that of one filter.

QUOTE
What I disagreed with is the idea that a speaker crossover could be affected by the receivers own crossover, which is what my friend was saying.


So please accept that you were wrong and your friend was right. Can we move on now?
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greynol
post Apr 19 2013, 16:23
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That's funny since the original post appears to say something quite different than what was just quoted.


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Yahzi
post Apr 19 2013, 19:58
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QUOTE ("julf")
So please accept that you were wrong and your friend was right. Can we move on now?


But I don't understand how filters can combine if they are operating in two different ranges! How can the slopes combine if one is at 80 Hz, for eg, and another is at 500 Hz? I refuse to believe my friend is right. Speaker crossovers CANNOT cascade with the amplifier crossover. Goodness, I had a discussion with a few EE's in another thread and they agreed that the filters cannot cascade. Now you are saying my friend is correct. WTF?
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Yahzi
post Apr 19 2013, 20:03
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QUOTE ("julf")
And how do they know if they operate in the same range or not?


If you set one to 80 Hz in the receiver and the other on the subwoofer to 80 Hz, then they will operate in the same range.

QUOTE
Seriously, one more time - they *will* combine in *any* case. That result might not cause an audible difference if their ranges are far enough apart.


You keep claiming this, but you aren't EXPLAINING to me how this is so. How do passive crossovers in a speaker combine with a receiver active crossover when the operating range is miles apart? Please explain that FOR ONCE, instead of just making me accept it.

This post has been edited by Yahzi: Apr 19 2013, 20:03
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Yahzi
post Apr 19 2013, 20:06
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QUOTE ("dhromed")
In any case, Arnold said that stacking the filters will have undesired consequences, so it appears that Yahzi is right and his friend is wrong, but for the wrong reasons.


Now you have lost me. I'm right one instance, then I'm wrong in the other. Perhaps this place is just not a good source of information. rolleyes.gif
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greynol
post Apr 19 2013, 20:13
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http://www.hydrogenaudio.org/forums/index....st&p=831271

I won't be surprised when the rest of us simply ignore you after too long.

This has gone beyond silly.

This post has been edited by greynol: Apr 19 2013, 20:14


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