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Double bass and bass management - Page 7

post #181 of 238
Quote:
Originally Posted by Bill Fitzmaurice View Post

There's only one way to find out if your system works better running the mains full range, and that's to try it.
That's user error, pure and simple. A man's got to know his limitations, and those of his speakers as well.
I thought you were Yoda not Dirty Harry. biggrin.gif
post #182 of 238
Quote:
Originally Posted by Ed Mullen View Post

.....................legacy AVRs which only have one global XO for all channels.
This reminds me, Ed, do you know whether your (and mine) 3803's global crossover imposes a low-pass on the LFE channel at the particular crossover setting being used? I remember this being a concern years ago.
post #183 of 238
I just have to see how much further this can go...

I know I'm sick, sorry. tongue.gif

James
post #184 of 238
Thread Starter 
Quote:
Originally Posted by craig john 
Examine this graph closely. It contains your answer:
Quote:
Originally Posted by OllieS 
So they are overlapping? Then what is cascading? Does that mean when two filters combine or something else? My friend told me that any crossover you setup on a receiver or a processor is in effect still/also cascading with the speakers passive crossovers. If this is not the case, I would like to understand this a bit more.

?
post #185 of 238
Quote:
Originally Posted by OllieS View Post


?
http://www.wikipedia.org
post #186 of 238
Thread Starter 
I really would prefer if it is explained to me in simple terms. Please don't direct me to Wikipedia. I suppose I could have bypassed this entire forum and just wikipedia everything but it doesn't mean I'll understand it!!!
post #187 of 238
Quote:
Originally Posted by OllieS View Post

I really would prefer if it is explained to me in simple terms. Please don't direct me to Wikipedia. I suppose I could have bypassed this entire forum and just wikipedia everything but it doesn't mean I'll understand it!!!
I thought it might give you some helpful information while you are impatiently waiting for someone to type out another paragraph that is the same as before but worded differently in hopes that you might understand it.
post #188 of 238
Thread Starter 
But nothing was explained!!! I just got a graph ... I asked a question .. in the hopes that I might understand it better and then you direct me to Wikipedia. No wonder I don't learn anything. rolleyes.gif
post #189 of 238
Quote:
Originally Posted by OllieS View Post


?

The crossovers inside speakers are used to direct the appropriate frequencies to the drivers in the speakers.

Read it again.

If you have a 2 way speaker, the crossover blends between the woofer and the tweeter so the tweeter isn't dying from trying to play bass and the woofer isn't resonating and beaming from trying to play high treble.

Crossover to a tweeter is typically around 2000 Hz. 2000 Hz. two thousand hertz.

If the speaker is three way, it might have a crossover from woofer to midwoofer in the 500 Hz range.

There is no crossover inside any typical speaker that is intended to blend between the drivers in the speaker and some other drivers elsewhere. So there's not a crossover sitting there so you can connect a supertweeter and reproduce sound up to 40,000 Hz even though you could not hear it.

There's also not a crossover in a normal speaker that would blend between the speaker's biggest woofer and a sub.

When you apply a crossover in a receiver, the crossover is intended to blend between the main speakers, as a whole, however many woofers it has plus its tweeter, and the sub. From speaker to sub. Typically, folks suggest keeping that crossover to 80 Hz but many receivers allow settings up to 200 Hz.

Okay, let's say you set the receiver's crossover at 200 Hz. That means the receiver starts turning down (rolling off) the signal going to the speaker somewhere above 200 Hz and the input to (and output from) that speaker (the main speaker not the sub) is decreased by either 3 or 6 dB at 200 Hz. It's doing the same basic thing to the signal from the sub, turning it down from some frequency below 200 Hz so that it is at -3 or -6 dB at the 200 Hz crossover point. Ten the sub and main speaker add up the way the crossover topology is intended to work. They add correctly according to the topology not only at the 200 Hz crossover point but also below (as the sub gets louder and the speaker gets quieter) and above (as the spekaker gets louder and the sub gets quieter).

Sooooo, if your lowest crossover in the speaker is 500 Hz, and the receiver's crossover keeps out (essentially) 200 Hz and BELOW from going to the speaker, do you see how not having any 200 Hz material to roll off is irrelevant to the crossover that's already down 3 or 6 dB more than an octave higher at 500 Hz?

Can you see how a rolloff for a 200 Hz crossover is not relevant to what a crossover centered at 2000 Hz is doing? That's over three octaves above the sub's crossover. So the sub's output is rolled off (assuming typical 24 dB per octave slope) by well over 70 dB at frthe tweeter crossover's center frequency. that's less than one ten-millionth of the power present in the signal getting into the subwoofer at 2000 Hz. Depending on the topology inside the speaker, the tweeter may be electrically reduced by anywhere from 30 dB 1/1000 of power present in the signal) to over 72 dB (less than one ten-millionth of the power present in the signal) They aren't cascading because their significant effects are in different places. LIke vacuuming the bedroom doesn't change what you have to do to vacuum the living room.

Now one reason you don't want to have speaker-frequency crossovers inside receivers (although there are real potential benefits from active biamping) is because the speaker already has a crossover. If I have a receiver crossover set for 2000 Hz and the speaker's crossover is 2000 Hz, I've potentially doubled the effective slope of the crossover. Instead of being reduced by 3 or six dB at the crossover point, both the tweeter and the woofer may down by 6 or 12 dB. That means that at the crossover point (where hearing is pretty darn sensitive) there's going to be too little sound, and things will sound dull and unexciting.

Like this poost.
post #190 of 238
Quote:
Originally Posted by craig john View Post

Examine this graph closely. It contains your answer:

Quote:
Originally Posted by OllieS View Post

So they are overlapping?

What is overlapping in the diagram, OllieS, is the high and low pass filters of the 2 crossovers that are shown in the diagram.

Do you know what a crossover is?

The subwoofer, btw, if it were shown in the diagram, would be at the far left of the diagram.
post #191 of 238
Thread Starter 
Quote:
Originally Posted by sivadselim 
What is overlapping in the diagram, OllieS, is the high and low pass filters of the 2 crossovers that are shown in the diagram.

Where the red dots are it shows two little black lines intersecting. I assumed that was the overlap point.
post #192 of 238
Quote:
Originally Posted by OllieS View Post

Where the red dots are it shows two little black lines intersecting. I assumed that was the overlap point.
The diagram shows where the high and low pass filters of each of the 2 crossovers shown in the diagram overlap. That is how a crossover works. The high and low pass filters overlap one another. But you can also clearly see that the 2 individual crossovers shown in that diagram do NOT overlap with one another at all. In that same way, neither would an AVR's subwoofer's crossover overlap with the crossover between a speaker's woofer and midrange driver in a 3-way (or more) speaker and certainly not the crossover between a woofer and tweeter in a 2-way speaker.
post #193 of 238
Quote:
Originally Posted by OllieS View Post

Please explain this for me. Why don't they cascade? Wouldn't they cascade in the bass region then?
Because there is no passive crossover in the bass region. The picture posted really didn't address the question, which had to do with cascading the sub low pass filters, and had nothing to do with the passive crossovers present in the main speakers.

There are two active low pass filters present, one in the AVR, the other in the sub amp. Assume that you have the AVR filter set at 80Hz, and it's a 2nd order/12dB octave filter. If you also set the filter in the sub amp at 80Hz and it's also a 2nd order filter the net result will be 4th order/24dB filtering at 80Hz. Steeper filtering slopes have the benefit of removing more of the directional frequency content above the subwoofer pass band.
post #194 of 238
Quote:
Originally Posted by Bill Fitzmaurice View Post

Assume that you have the AVR filter set at 80Hz, and it's a 2nd order/12dB octave filter. If you also set the filter in the sub amp at 80Hz and it's also a 2nd order filter the net result will be 4th order/24dB filtering at 80Hz. Steeper filtering slopes have the benefit of removing more of the directional frequency content above the subwoofer pass band.
Not that it is hugely relevant to what OllieS is asking about, but, FYI, most AVR's low-pass filter slopes are 24dB/octave. And their high-pass filter slopes are usually 12dB/octave. And most sub's internal low-pass filter slopes are 24dB/octave if not even steeper.

This IS relevant to your recommendation of the usefulness of intentionally cascading an AVR and sub's low-pass filters. 24dB/octave should, normally, be plenty. Cascading an AVR's 24dB/octave low-pass with a sub's internal 24dB/octave low-pass is going to result in a 48dB/octave slope which is pretty steep. Sure, it could possibly get rid of some sort of weird anomaly in or near the crossover region but there are probably better ways.
Edited by sivadselim - 4/9/13 at 3:21pm
post #195 of 238
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice 
There are two active low pass filters present, one in the AVR, the other in the sub amp. Assume that you have the AVR filter set at 80Hz, and it's a 2nd order/12dB octave filter. If you also set the filter in the sub amp at 80Hz and it's also a 2nd order filter the net result will be 4th order/24dB filtering at 80Hz. Steeper filtering slopes have the benefit of removing more of the directional frequency content above the subwoofer pass band.

Okay. But as far as the passive crossover in the speaker interacting with the active crossovers in the receiver, that's a completely different thing and there is no interaction going on there? Just so I'm clear...
post #196 of 238
Quote:
Originally Posted by sivadselim View Post

Not that it is hugely relevant to what OllieS is asking about, but most AVR's low-pass filter slopes are 24dB/octave. And their high-pass filter slopes are usually 12dB/octave. And most sub's internal low-pass filters' slopes are 24dB/octave if not even steeper.
Most manuals that I've seen don't say what they have for slopes. In any event this is a try-it tweak. If it sounds better with cascaded filters, it is better; if it doesn't, don't bother.
post #197 of 238
Thread Starter 
Quote:
Originally Posted by sivadselim 
This IS relevant to your recommendation of the usefulness of intentionally cascading an AVR and sub's low-pass filters. 24dB/octave should be plenty. Cascading an AVR's 24dB/octave low-pass with a sub's internal 24dB/octave low-pass is going to result in a 48dB/octave slope which is pretty steep. Sure, it could possibly get rid of some sort of weird anomaly in or near the crossover region but there are probably better ways

I understand this now. Two active low-pass filters combining negatively will double the steepness of the slope. The high frequencies above the crossover would be so soft using a 48 dB low pass that it would not matter.

Something interesting I learned about this Rotel processor (well the bigger brother model, but I think it may apply to the 1068) is that the low-pass and high-pass filters are both 4th-order!
post #198 of 238
Quote:
Originally Posted by OllieS View Post

Okay. But as far as the passive crossover in the speaker interacting with the active crossovers in the receiver, that's a completely different thing and there is no interaction going on there? Just so I'm clear...
There shouldn't be, OllieS. It would, of course, depend upon how low the speaker's woofer in question is crossed with the next driver above it as well as the slope of the speaker's crossover's low-pass filter. As well as how high the crossover in the AVR is set. But in most circumstances, the two crossover points (the AVR's and the speaker's) should not be close enough to one another to interfere (overlap) with one another. It is hard to imagine a situation where someone would be using a really high crossover in the AVR (i.e. 200Hz) with a speaker that had a woofer that was crossed in low enough with a midrange driver such that the two crossovers interacted. A speaker with a dedicated woofer crossed to a midrange driver would most likely require or dictate a more standard crossover point such as 80Hz in the AVR.
post #199 of 238
Quote:
Originally Posted by Bill Fitzmaurice View Post

Most manuals that I've seen don't say what they have for slopes.
Many do, if you look closely enough. Or that information IS available somewhere. That they have a 24dB/octave low pass yet a 12dB/octave high pass probably goes back to the original THX recommendation of a 4th order low-pass with a 2nd order high-pass and specific use of sealed speakers with a 2nd order roll-off at the high-pass point (80Hz in this case) to achieve the matching 24dB/octave slope at the speakers. Unfortunately (or maybe fortunately?), this asymmetric crossover is something that has remained in AVRs for years, since. It may also be steeper at the low-pass to help reduce subwoofer localization and/or the same sort of anomalies that your recommendation of intentionally cascading the low-passes can help alleviate. Honestly, I do not know why it has remained like this (24/12) as most people use ported speakers. But it has.
post #200 of 238
Quote:
Originally Posted by sivadselim View Post

Many do, if you look closely enough. Or that information IS available somewhere. That they have a 24dB/octave low pass yet a 12dB/octave high pass probably goes back to the original THX recommendation of a 4th order low-pass with a 2nd order high-pass and specific use of sealed speakers with a 2nd order roll-off at the high-pass point (80Hz in this case) to achieve the matching 24dB/octave slope at the speakers. Unfortunately (or maybe fortunately?), this asymmetric crossover is something that has remained in AVRs for years, since. It may also be steeper at the low-pass to help reduce subwoofer localization and/or the same sort of anomalies that your recommendation of intentionally cascading the low-passes can help alleviate. Honestly, I do not know why it has remained like this (24/12) as most people use ported speakers. But it has.
If it is it's wrong. Subs don't have to contend with excursion and power issues above their operating bandwidth, whereas mains and surrounds do have to contend with those issues below their operating bandwidth, so if anything the high pass should be a higher order, not lower, but at any rate at least the same. From a phase standpoint 4th order Linkwitz-Reilly for both would work best, and in pro-sound that's the most common configuration with electronic crossovers.
post #201 of 238
Quote:
Originally Posted by Bill Fitzmaurice View Post

If it is it's wrong.
I don't know. For some reason (and I assume there IS some reason) most manufacturers have steadfastly stuck to this convention (that being a digital crossover with a 4th order low pass and a 2nd order high pass). Honestly, I haven't looked into this in a few of years but I do not think it has changed.
post #202 of 238
Quote:
Originally Posted by OllieS View Post

So they are overlapping? Then what is cascading? Does that mean when two filters combine or something else? My friend told me that any crossover you setup on a receiver or a processor is in effect still/also cascading with the speakers passive crossovers. If this is not the case, I would like to understand this a bit more.
Quote:
Originally Posted by Bill Fitzmaurice View Post

The picture posted really didn't address the question, which had to do with cascading the sub low pass filters, and had nothing to do with the passive crossovers present in the main speakers.
Re-read the question. It had nothing to do with cascading subwoofer low pass filters. He's asking about interaction between the receiver's subwoofer crossover and the passive crossovers in the speakers.

The graph was intended to show that the speaker crossovers are well above the range of the subwoofer crossover and that they don't "cascade" or interact with each other. I guess I should have explained it better.

Craig
post #203 of 238
Martin and Logan people discuss this very subject:

https://www.youtube.com/watch?v=uzCIMufCQLk
post #204 of 238
Thread Starter 
Quote:
Originally Posted by craig john 
Re-read the question. It had nothing to do with cascading subwoofer low pass filters. He's asking about interaction between the receiver's subwoofer crossover and the passive crossovers in the speakers.

The graph was intended to show that the speaker crossovers are well above the range of the subwoofer crossover and that they don't "cascade" or interact with each other. I guess I should have explained it better.

So the speaker crossover won't cascade with the subwoofer because the frequency where the mid-bass/bass driver crosses over is too high. It's outside the effective range of the subwoofer. And if I use a 60 Hz active crossover in my receiver then it won't cascade with the passive crossover of my speaker because the mid/bass woofers would not be crossed over at 60 Hz, but much much higher.

If I'm correct on both counts then I'll be happy. Then my friend is clearly confused about what a crossover is or how it works if he thinks the passive crossover would cascade with the active crossovers in the prepro.
post #205 of 238
Quote:
Originally Posted by OllieS View Post


So the speaker crossover won't cascade with the subwoofer because the frequency where the mid-bass/bass driver crosses over is too high. It's outside the effective range of the subwoofer. And if I use a 60 Hz active crossover in my receiver then it won't cascade with the passive crossover of my speaker because the mid/bass woofers would not be crossed over at 60 Hz, but much much higher.

If I'm correct on both counts then I'll be happy. Then my friend is clearly confused about what a crossover is or how it works if he thinks the passive crossover would cascade with the active crossovers in the prepro.

Yes you are correct and your friend is not.  :-)

post #206 of 238
Quote:
Originally Posted by sivadselim View Post

I don't know. For some reason (and I assume there IS some reason) most manufacturers have steadfastly stuck to this convention (that being a digital crossover with a 4th order low pass and a 2nd order high pass). Honestly, I haven't looked into this in a few of years but I do not think it has changed.
I don't either, I design speakers, not AVRs. But if I did design AVRs I'd be using 4th/4th L-R filters.
post #207 of 238
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice 
don't either, I design speakers, not AVRs. But if I did design AVRs I'd be using 4th/4th L-R filters.

Funnily enough the Rotel RSP-1098 has exactly the configuration you speak of. 4th-order high-pass and low-pass as measured at Sound and Vision. I don't know what kind of effect that would have.

But if all speakers are all set to Large then the slopes would not have any effect on the speakers, right? Because there is no crossver?
post #208 of 238
Quote:
Originally Posted by OllieS View Post

Funnily enough the Rotel RSP-1098 has exactly the configuration you speak of. 4th-order high-pass and low-pass as measured at Sound and Vision. I don't know what kind of effect that would have.

But if all speakers are all set to Large then the slopes would not have any effect on the speakers, right? Because there is no crossver?
That's where it gets confusing. Ideally if you wished you could send everything below, say, 80Hz to the subs and at the same time send everything above 35-40Hz, or whatever they're able to handle, to the mains. What a particular AVR is capable of doing you'd want to determine before buying if you intend to go this route. I'm sure some will only give a one or the other signal routing option, as opposed to one or both.
post #209 of 238
Thread Starter 
To my knowledge - and this is iffy.... because I'm not clued up here, what little I have learned from you guys is that if Large speakers are used then NO crossover is used in the processor. So then it doesn't matter if the low-pass/high-pass slopes are 4th-order or 8th-order, it wouldn't have any effect since all speakers are Large and hence no crossover. If there is no crossover, then there is no crossover slope.

I could be wrong, but that is what I gave gathered.I just want confirmation.
post #210 of 238
Quote:
Originally Posted by OllieS View Post

Rotel RSP-1098
It is likely that that processor has some capabilities that more standard AVRs do not possess. It may even allow separate and different high and low passes to be applied to a speaker channel. And it may offer some non-conventional bass management schemes.
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