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Crossover cascading
Yahzi
post Apr 12 2013, 20:39
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Hi,

Just wanted confirmation on something. I was having a discussion with someone about crossovers, especially low-pass filters as we were discussing bass management. I told him that he should disable his subwoofer LPF to avoid interaction from his AVR LPF. His response was that the internal passive crossovers in the speakers would still, in effect, cascade if using an active crossover in the AVR.

I'm not sure how this could be. You guys are the experts, just thought I would get your feedback on this.
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Arnold B. Kruege...
post Apr 12 2013, 22:16
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QUOTE (Yahzi @ Apr 12 2013, 15:39) *
Hi,

Just wanted confirmation on something. I was having a discussion with someone about crossovers, especially low-pass filters as we were discussing bass management. I told him that he should disable his subwoofer LPF to avoid interaction from his AVR LPF. His response was that the internal passive crossovers in the speakers would still, in effect, cascade if using an active crossover in the AVR.

I'm not sure how this could be. You guys are the experts, just thought I would get your feedback on this.



Crossovers need to be designed carefully and intentionally. Because phase relationships in the crossover affect system response everything needs to be considered. Bottom line, crossovers can't be thrown in haphazardly. Cascade does not mean better. The crossovers in the AVR are designed to work as they are. Cascading additional crossovers will usually result in undesired dips and roll-offs.
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Yahzi
post Apr 12 2013, 22:31
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I understand that. But what I am asking is if the active AVR crossover could cascade with the passive internal speaker crossover. Wouldn't the slopes combine if both crossovers were operating in the same frequency range? But if my speakers passive crossover for the woofer is 400 Hz and I use a 100 Hz crossover, wouldn't the speakers crossover be well outside the effective range of the AVR's slope?

What is a typical crossover for a 2-way bookshelf? Wouldn't the passive crossover in a speaker be isolated from the AVR crossover? I guess that is the question I'm asking for but I don't know 100% whether it's true or not.
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Arnold B. Kruege...
post Apr 12 2013, 22:39
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QUOTE (Yahzi @ Apr 12 2013, 17:31) *
I understand that.


If so why are you contradicting the answer you were provided with?

QUOTE
But what I am asking is if the active AVR crossover could cascade with the passive internal speaker crossover. Wouldn't the slopes combine if both crossovers were operating in the same frequency range?


They will combine, but the combination probably won't end up giving you smooth or flat response.

QUOTE
But if my speakers passive crossover for the woofer is 400 Hz and I use a 100 Hz crossover, wouldn't the speakers crossover be well outside the effective range of the AVR's slope?


How do you all of a sudden know this information, or are you just speculating?

QUOTE
What is a typical crossover for a 2-way bookshelf?


Probably, a couple of KHz.

QUOTE
Wouldn't the passive crossover in a speaker be isolated from the AVR crossover? I guess that is the question I'm asking for but I don't know 100% whether it's true or not.


Please post again when you actually have a relevant question based on actual reliable knowledge.
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Yahzi
post Apr 12 2013, 22:48
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QUOTE ("arnyk")
How do you all of a sudden know this information, or are you just speculating?


It's a hypothetical. I'm throwing an example out there to try and make sense of things.

QUOTE
Please post again when you actually have a relevant question based on actual reliable knowledge.


Why are you behaving like this? You think I would be here if I had "actual reliable knowledge? Don't be silly. I asked a few questions that you did not clearly answer to my satisfaction so clearly asking them again was my only alternative. Your initial reply to my questions did not explain anything.

1. If I use a crossover in my AVR would this cascade with my speakers passive crossover? Yes or no? If yes, then clearly explain why it would. If no, please explain.
2. If crossovers cascade only if they are in the same frequency range then in what scenario would this happen in a conventional speaker set up using an AVR?

Please answer without the aggressive tone.

This post has been edited by Yahzi: Apr 12 2013, 23:09
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Yahzi
post Apr 12 2013, 22:52
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QUOTE ("Arnold B. Krueger")
If so why are you contradicting the answer you were provided with?


I'm not contradicting anything. You said crossovers needed to be carefully designed. That's a truism and it makes sense, but it DOES NOT answer my question to you. If you read what I wrote the answer you supplied did not answer what I asked. I did not ask what the consequences would be of a cascading crossover. I merely asked if and when it would occur.

This post has been edited by Yahzi: Apr 12 2013, 22:53
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julf
post Apr 13 2013, 11:35
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QUOTE (Yahzi @ Apr 12 2013, 23:48) *
2. If crossovers cascade only if they are in the same frequency range then in what scenario would this happen in a conventional speaker set up using an AVR?


What exactly do you mean with "cascade". If you apply one filter, and then another filter on the filtered signal, the signal will be affected by the transfer functions of both filters. If the crossover frequencies are far apart, the interaction will be small, but it will be there nevertheless.
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Arnold B. Kruege...
post Apr 13 2013, 16:06
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QUOTE (Yahzi @ Apr 12 2013, 17:52) *
QUOTE ("Arnold B. Krueger")
If so why are you contradicting the answer you were provided with?


I'm not contradicting anything. You said crossovers needed to be carefully designed. That's a truism and it makes sense, but it DOES NOT answer my question to you.


Sure it does. Just answer one question: "Am I using this speaker and crossover in a way that fits in with its designers intent?"

What you seem to be suggesting is mixing and matching speakers and crossovers like socks in a drawer.

QUOTE
If you read what I wrote the answer you supplied did not answer what I asked. I did not ask what the consequences would be of a cascading crossover.


Fooled me.

QUOTE
I merely asked if and when it would occur.


Obviously, you can cascade crossovers whenever you are able to and actually do so. That is a truism. Since you don't seem to like truisms, I don't know why you ask questions that have only truisms as logical answers.

Part of your problem seems to be that you don't appear to know enough about your speakers to ask properly formed questions about them.
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Yahzi
post Apr 13 2013, 16:58
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QUOTE ("Arnold B Krueger")
Obviously, you can cascade crossovers whenever you are able to and actually do so. That is a truism. Since you don't seem to like truisms, I don't know why you ask questions that have only truisms as logical answers.


Do you have a reading comprehension problem? You aren't actually answering my questions ... again! Who cares when you are supposed to cascade crossovers. That is not what I asked. I asked you specific questions and I had hoped you would actually answer them but you sidestep AGAIN with useless babble.

QUOTE
Obviously, you can cascade crossovers whenever you are able to and actually do so. That is a truism. Since you don't seem to like truisms, I don't know why you ask questions that have only truisms as logical answers.

Part of your problem seems to be that you don't appear to know enough about your speakers to ask properly formed questions about them.


Part of your problem is that you don't seem capable of answering logical questions and instead question the reason why I asked them. I don't need a psychoanalysis from you, I need answers and you have provided none. You just babbled on and gave me useless information for a second time. It boggles the mind why you can't just answer with constructive advice instead of dodging the questions and wasting time. You've been very unhelpful.

This post has been edited by Yahzi: Apr 13 2013, 17:05
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Yahzi
post Apr 13 2013, 17:09
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QUOTE ("julf")
If you apply one filter, and then another filter on the filtered signal, the signal will be affected by the transfer functions of both filters. If the crossover frequencies are far apart, the interaction will be small, but it will be there nevertheless.


Thank you, at least someone who can stick to the topic. So if I use 80 Hz low-pass in my receiver and another 80 Hz low-pass the slopes would combine. But if I use a crossover of 80 Hz and I have a bookshelf speaker, a 2-way, would the crossover of 80 Hz interact with passive crossover in the speaker?
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Soap
post Apr 13 2013, 19:29
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QUOTE (Yahzi @ Apr 13 2013, 11:09) *
. But if I use a crossover of 80 Hz and I have a bookshelf speaker, a 2-way, would the crossover of 80 Hz interact with passive crossover in the speaker?


Yes.

A filter is a filter is a filter.

Unless you mean something other than how julf described "interact" ("the transfer functions of both filters").


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Yahzi
post Apr 13 2013, 19:33
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QUOTE ("Soap")
Yes.

A filter is a filter is a filter.


Please explain how it would interact.
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Soap
post Apr 13 2013, 19:53
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QUOTE (Yahzi @ Apr 13 2013, 13:33) *
Please explain how it would interact.



Maybe despite his brashness Arnold is right. I believe I answered how they would interact by quoting julf's description of how they would interact.

You don't seem to understand this answer, and that's cool. So I'm not dodging the question but we need to step back a second and figure out exactly what you're asking and also what you think julf's answer means.

Please rephrase your original question in a more verbose manner and talk a bit about how you understand julf's answer.


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Yahzi
post Apr 13 2013, 20:02
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Actually just forget about. I said "if a speaker crossover would interact with an AVR crossover" and "julf" said a filter applied to another filter would be effected. Now while that was infinitely more useful than Arnold's babble it still did not answer my question directly.

I'm asking about a speakers passive crossover between the drive units, and the AVR crossover - so if I use an 80 Hz AVR crossover in a 2-way speaker, that has a woofer low-passed at 800 Hz, how the fuck are the filters going to combine or interact? Will the slopes interact and if so, how?

If you understood basic English you would have gathered what I had asked. I'm losing patience when people have fuck all answers to give me and instead question and analyse why I have asked questions that should have been answered. If you can't answer my questions then you have demonstrated your incompetence and I'll go somewhere else.

This post has been edited by Yahzi: Apr 13 2013, 20:10
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Soap
post Apr 13 2013, 20:11
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QUOTE (Yahzi @ Apr 13 2013, 14:02) *
If you understood basic English you would have gathered what I had asked.


Sorry I can't read minds.



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julf
post Apr 15 2013, 09:58
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QUOTE (Yahzi @ Apr 13 2013, 21:02) *
I'm asking about a speakers passive crossover between the drive units, and the AVR crossover - so if I use an 80 Hz AVR crossover in a 2-way speaker, that has a woofer low-passed at 800 Hz, how the fuck are the filters going to combine or interact? Will the slopes interact and if so, how?


The problem is that you are using very inexact and ambiguous terminology, so I can understand why people are asking you to explain how you understand our answers.

The filters won't "interact" in the sense that they would somehow change each other's function. But the end result (the frequency and phase response of your speaker) is affected by both filters. That's the "combine" part. Of course their effect combines, because the signal has to pass first one and then the other filter.
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Arnold B. Kruege...
post Apr 15 2013, 15:25
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QUOTE (Yahzi @ Apr 13 2013, 15:02) *
Actually just forget about. I said "if a speaker crossover would interact with an AVR crossover" and "julf" said a filter applied to another filter would be effected. Now while that was infinitely more useful than Arnold's babble it still did not answer my question directly.


I guess that we have an example of the idea that if a person is poorly informed enough, any answer no matter how carefully formed, is undecipherable.

QUOTE
I'm asking about a speakers passive crossover between the drive units, and the AVR crossover - so if I use an 80 Hz AVR crossover in a 2-way speaker, that has a woofer low-passed at 800 Hz, how the (immature verbiage removed) are the filters going to combine or interact? Will the slopes interact and if so, how?


The filters won't interact because they are electrically isolated from each other.

Their electrical amplitude responses will be multiplied. Their responses given in dB will add.

If one filter passes one half of its input at a certain frequency and the other passes one quarter of its input at the same frequency the total response will be 1/8.

If one filter has a loss of 6 dB at a certain frequency and the other has a loss of 12 dB at the same frequency then the total response will show an 18 dB loss.

If one filter has flat response over a range of frequencies and the other has flat response over the range of frequencies then the total response will be flat.

If one filter has flat response over a range of frequencies and the other has sloped response over the same range of frequencies then the total response will be sloped the same as the sloped one..

If both filters have sloped response over a range of frequencies then the total response will have response that sloped by a slope that is the sum of the two slopes.

If one filter has response sloped up over a range of frequencies and the other has response that is sloped down with the same slope over the same range of frequencies then the total response will be flat.

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Yahzi
post Apr 15 2013, 16:55
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QUOTE
Their electrical amplitude responses will be multiplied. Their responses given in dB will add.


How?
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greynol
post Apr 15 2013, 17:43
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There's a point where you either enroll in a course in electronics or take what people say on faith.


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Yahzi
post Apr 15 2013, 17:55
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QUOTE ("greynol")
There's a point where you either enroll in a course in electronics or take what people say on faith.


But no one has even attempted to explain anything! If two filters at two completely different frequencies can't interact because they are isolated then how could the filters combine? If one is at 12 dB octave at 80 hz and the other is at 600 Hz then how the effing hell can these filters combine?

Explain that to me? Or must I be an EE to understand something? All I for is an explanation because NONE HAVE BEEN GIVEN.

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ktf
post Apr 15 2013, 18:09
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QUOTE (Yahzi @ Apr 15 2013, 18:55) *
If two filters at two completely different frequencies can't interact because they are isolated then how could the filters combine? If one is at 12 dB octave at 80 hz and the other is at 600 Hz then how the effing hell can these filters combine?


You asked something different?

QUOTE (Yahzi @ Apr 12 2013, 21:39) *
I told him that he should disable his subwoofer LPF to avoid interaction from his AVR LPF. His response was that the internal passive crossovers in the speakers would still, in effect, cascade if using an active crossover in the AVR.

Of course crossovers can 'interact' (they'll be around the same frequency) and LPF's can 'interact'. (they'll be around the same frequency) Not really 'interacting' as responses would just be multiplied. 'Interaction' of an LPF with a crossover is a different matter.

This post has been edited by ktf: Apr 15 2013, 18:12


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Propheticus
post Apr 15 2013, 18:46
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The filters add up! The end result will be input - filter1 - filter2 = output... Why is that so ffing hard to understand? /agree with Greynol

If the internal (passive) crossover in the subwoofer can be bypassed/disabled, I'd go with the option where the AVreceiver manages the crossover (actively before amplification). If it can't... have faith that the engineers that designed the sub knew what they were doing when calculating the passive crossover.

Some light reading: http://en.wikipedia.org/wiki/Audio_crossover

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greynol
post Apr 15 2013, 19:14
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They add because decibels are logarithmic.

So in addition to knowing something about electronics, understanding math is also important if you really want to better understand the "how" part.

http://en.wikipedia.org/wiki/Decibel

I call bullshit on "no one explained anything to me."

This post has been edited by greynol: Apr 15 2013, 19:24


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julf
post Apr 16 2013, 10:04
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QUOTE (Yahzi @ Apr 15 2013, 18:55) *
But no one has even attempted to explain anything!


We have. And we have answered your question several times. The problem seems to be that you don't understand the answer.

QUOTE
If two filters at two completely different frequencies can't interact because they are isolated then how could the filters combine? If one is at 12 dB octave at 80 hz and the other is at 600 Hz then how the effing hell can these filters combine?


I don't think cursing will help get your message across - it is pretty much like the typical American reaction to someone not speaking English - shout louder.

QUOTE
Explain that to me? Or must I be an EE to understand something? All I for is an explanation because NONE HAVE BEEN GIVEN.


OK, we have said a number of times that the signal will be affected by the transfer functions of both filters. It is pretty clear that you don't understand the answer.

Arnold tried to explain by giving the extremely simple explanation of "Their electrical amplitude responses will be multiplied. Their responses given in dB will add." Seems you didn't understand that one either. So let's try one more time:

You have a 12 dB/oct filter at 600 Hz. Down at 80 Hz that filter will provide approximately 96 dB attenuation. From that point on, your 80 Hz filter will add even more attenuation on the frequencies below 80 Hz, so at 40 Hz the attenuation is 120 dB instead of the 108 dB you would get with only the 600 Hz filter.

Of course that example is simplified and assumes a perfect filter, but you ought to get the idea.

Can we now agree that someone has attempted to explain things to you?
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Nessuno
post Apr 16 2013, 11:33
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QUOTE (julf @ Apr 16 2013, 11:04) *
You have a 12 dB/oct filter at 600 Hz. Down at 80 Hz that filter will provide approximately 96 dB attenuation. From that point on, your 80 Hz filter will add even more attenuation on the frequencies below 80 Hz, so at 40 Hz the attenuation is 120 dB instead of the 108 dB you would get with only the 600 Hz filter.

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).


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