Bass management question

[Goliath]

I really don't know what you want here, you asked about passive crossover's cascading with AVR bass management. I informed you mine do and you informed me that I made things confusing... What exactly do you want to know?

I thought my friend was wrong in what he said. He said passive crossovers in a speaker will cascade with an AVR. He said the slopes would combine. I thought in order for the slopes to combine the frequency range would have to be the same and I thought the effective range of the active crossover that people would typically use would fall outside the range of most speakers where the passive crossovers are concerned. I thought the passive crossovers were largely isolated from the active crossovers in the AVR.

I thought he was wrong and so I sought out an explanation and I've received many explanations. But so far the answer I've been given is : not necessarily, maybe, or yes it will.

 

[Grador]

I do see that I have some room in the above to explain a little better, so I shall. On your hypothetical, I agree with steve that you are correct. There would be very little interaction to speak of. What I was trying to say though was that on a 2 way system the crossover point would be much much higher than 300 hz putting the crossovers well out of the way of eachother.

I then used my speakers as an example to show that they could be very close.

 

[Goliath]

I then used my speakers as an example to show that they could be very close.

Okay, well I'm learning things every day. I don't know your speakers and I did jump to conclusions, so I was clearly in the wrong.

 

[Pyrrho]

Since there still seems to be some confusion about "cascading" crossovers:

I mentioned to my friend that if you use both processor LPF and subwoofer LPF that they will cascade. But he tells me that speakers have passive crossovers so any crossover you setup on a receiver or a processor is in effect still/also cascading and that in some cases you will effectively be creating a bandpass xover of x+y order..

Is that true?

Since this is actually a new question I'll tackle it. Almost no speakers have a high pass for the woofer, so this is not true at all. The first crossover in the speaker will be the one from the woofer to tweeter [or mid] well above the sub crossover point.

Grador is correct.

The crossover for the subwoofer, if set at the same frequency on both the subwoofer itself and the processor, will cause the high end of the subwoofer's frequency reproduction to drop off faster than it would if only using the processor's crossover. Thus, if the processor was not designed by an idiot who got it completely wrong, there will be a dip in the frequency response at the crossover point if someone uses both crossovers at the same point. With a competently designed processor, using just its crossover (and also properly setting the levels of the various channels) will result in a proper bass response (insofar as the speakers and room effects allow). Thus, using both results in improper frequency response and inferior sound. Of course, some people like things set improperly, and they are free to do that if they so desire. But if one wishes to have as accurate reproduction of the sound as possible, one should set things properly.

Correct me if I'm wrong but the speaker crossovers are usually WELL outside the operating bandwidth of a processor/receivers crossover? So it's also never going to cascade or interact.

Not always, the crossover from the woofer to mids on my EMPs occurs at 120 hz.

My friend is saying : the passive crossovers in the main speakers do not magically disappear the typical passive (having designed and built some myself even) will have a lowpass and a highpass right there on the pcb...
many home theatre receiver have highpass of 12db/oct and lowpass of 24db/oct because the assumption is that most hifi passives are 12db/oct, thus creating a sum total of 24db/oct, thus keeping the
phase in-line ..

What is he saying?

The reason I found your example perplexing is that I assumed most speakers did not cross the woofers over so low.

I thought it was closer to something like this :

Let us consider an example of a speaker with a crossover at 150 Hz in the speaker itself: The Carver AL-III Plus:

CarverAudio.com - AL-III Plus | Speakers

Even if one uses such a speaker with a subwoofer and sets one's processor for a 150 Hz crossover (and bypasses the subwoofer's crossover), there is still not a problem from this (though it would not be good to set the crossover that high due to being able to locate the subwoofer by sound alone, and the main speaker is capable of much lower than 150Hz). This is because the speaker, taken as a whole, still goes beyond the 150 Hz range. It would be a different matter if one disconnected the woofer in the Carver AL-III Plus yet still used the crossover in it along with the processor's crossover. But without doing that, there is no concern about interaction of the crossovers. The reason is that the woofer is still going to produce some sound with such a setting due to the fact that none of the crossovers are of infinite slope; the speaker's crossover may be ignored and one may view it as if it were one driver covering the entire range that the speaker as a whole covers.

Now, with the processor and the subwoofer both applying a crossover at 150 Hz, it is an entirely different matter. This is because the subwoofer is not a full range speaker and is playing less sound above its crossover point than below it (unlike a regular speaker, which, if designed well, produces the same amount of sound both above and below the crossover point; that is, if there is a crossover at any frequency X, the sound just above X and just below X should be at the same level, whereas with a subwoofer, the sound above its crossover is diminished relative to the sound below the crossover). So when both crossovers (from a subwoofer and processor) are employed in such a fashion, the slope at the crossover frequency will be greater and will affect the sound adversely.

 

[PENG]

Okay, well I'm learning things every day. I don't know your speakers and I did jump to conclusions, so I was clearly in the wrong.

You are probably right about most book shelf and many floor standing speakers, but there are some, tend to be larger, floor standers that do crossover in the neighborhood of 120 Hz. So far you have been given one example of such speaker, but there are more.

 

[Goliath]

Thanks Peng. This is why this topic is confusing. Just when you think you know something ... you get conficting information and it ends up confusing you. Well it does for me, anyway. Some people tell me some things and other people say the exact opposite. I appreciate you confirming my suspicions. You put things into perspective for me.

 

[fuzz092888]

Thanks Peng. This is why this topic is confusing. Just when you think you know something ... you get conficting information and it ends up confusing you. Well it does for me, anyway. Some people tell me some things and other people say the exact opposite. I appreciate you confirming my suspicions. You put things into perspective for me.

I admit to only skimming through this thread, but I'd like to reiterate one thing that has been said. IMO, you're not getting conflicting information. You are getting specific answers to specific questions (in most cases) which you sometimes tend to apply to the broader topic at hand, which is adding to your confusion. Now I'm not saying some of the answers you got weren't a little ambiguous, but for the most part everything seems fairly accurate.

One thing to keep in mind is that if you ask a specific or seemingly specific question, it is always best to clarify things, or at least ask if the answer applies to everything or just your example.

Cheers

 

[Grador]

Just reread this and have a comment

My friend is saying : the passive crossovers in the main speakers do not magically disappear the typical passive (having designed and built some myself even) will have a lowpass and a highpass right there on the pcb...
many home theatre receiver have highpass of 12db/oct and lowpass of 24db/oct because the assumption is that most hifi passives are 12db/oct, thus creating a sum total of 24db/oct, thus keeping the
phase in-line ..

What is he saying?

Your friend seems to think that having the crossovers both present is still an issue even if they're operating in different frequency ranges.. This really isn't the case.

 

[PENG]

Just reread this and have a comment



Your friend seems to think that having the crossovers both present is still an issue even if they're operating in different frequency ranges.. This really isn't the case.

I see that too, that's why I thought Goliath has been mostly right in what he's saying, it's his friend who might have been confusing him.

 

[Goliath]

Thanks guys for everything. Sorry again for being difficult earlier on in the discussion. I really do appreciate all the help and advice.