# pb13 ultra adjustment



## bone215 (Dec 15, 2006)

Just to play around, I turned on the crossover on the sub and lowered it to around 90 ish to see if any change in sound.
Slight change, seems a little tighter, with more emphasis on the lower stuff.
I will have to listen to a variety of music and movies to see.
Most advice I have read was NOT to do this, use both AVR crossover and sub crossover, but hey, it's time to play.


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## E-A-G-L-E-S (Sep 15, 2007)

If I am not mistaken it will only use the lowest x-over, not both.


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## bone215 (Dec 15, 2006)

Eagles
what do you mean? I thought the AVR's crossover was not a brick wall type of thing. E.G. if I set it to 80 Hz isn't there a slope which determines how much over 80 Hz rides along with it?


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## E-A-G-L-E-S (Sep 15, 2007)

You are correct, an 80Hz x-over point in your AVR is a gradual slope below that, not a cut-out filter.
But....say you have your avr @ 90Hz and your subs active x-over at 80Hz.....it will roll off from 80Hz not 90Hz.

I could be wrong, but that is what I think is correct.
Someone with more knowledge than I will come along soon to help, I'm sure.


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## salvasol (Oct 31, 2006)

E-A-G-L-E-S said:


> You are correct, an 80Hz x-over point in your AVR is a gradual slope below that, not a cut-out filter.
> But....say you have your avr @ 90Hz and your subs active x-over at 80Hz.....it will roll off from 80Hz not 90Hz.


I think EAGLES is correct ... that's why I've seen that is recommended to set the crossover at the AVR @ 80Hz and at the sub higher than 80Hz to avoid that the sub crossover takes over :yes:

We'll wait for an answer from the experts :bigsmile:


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## tonyvdb (Sep 5, 2007)

If you are using the crossover in the receiver then set the crossover switch to off on the PB 13 do not use both.


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## bone215 (Dec 15, 2006)

Eagles
at Avr set at 80, isn't it a gradual roll off above, not below??, the crossover sends stuff above 80 hz to the sub, but rolled off? So, therefore a 90 hz crossover on the sub cuts those above 80 frequencies even at a more rapid roll off?


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## E-A-G-L-E-S (Sep 15, 2007)

You are approaching this from the opposite angle of normal which is confusing.
Just use one(typically avr) and place it wherever you like it best...don't use both. 
But yes, it rolls off the frequencies above it's point not below....sorry about that.
But it will still go by the lower one of the two..it can't utilize both at the same time I don't believe.


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## Ed Mullen (Jul 28, 2006)

The more accurate description for that control on the subwoofer is a low pass filter. The slope of the filter is 12 dB/octave. 

The slope of the digital low pass filter in the AVR crossover network is 24 dB/octave. 

When both filters are enabled, they will cascade (combine) above the higher of the two settings. So if the AVR crossover is set to say 80 Hz, and the PB13-Ultra low pass filter is set to 120 Hz, the initial slope of the subwoofer roll-off will be 24 dB/octave above 80 Hz, increasing to 36 dB/octave above 120 Hz.


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## bone215 (Dec 15, 2006)

Thanks for all who jumped in here with comments, I appreciate it.
Ed, you have a very good knack for writing about this stuff, brief and to the point, you clarified what I was trying to think and express. Theoretically there could be a situation where the both controls could be utilized to create a better listening experience.
I do think in my case, it is all good, I just like to play. I also think the next expenditure will be on bass traps to reduce the room's influence on the sound.
Thanks again all.
SVS did a really good job with this sub, I guess you can't tell us what is next on the sub drawing board?????:whistling:


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## 57an0baby (Jun 18, 2008)

Crikey ! :unbelievable: I did not know about not using both crossovers. I set my subwoofer and the avr. But that is not correct. :coocoo:

Ok. An evening of tweaking again.


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## pbc (Sep 3, 2007)

Ed Mullen said:


> The more accurate description for that control on the subwoofer is a low pass filter. The slope of the filter is 12 dB/octave.
> 
> The slope of the digital low pass filter in the AVR crossover network is 24 dB/octave.
> 
> When both filters are enabled, they will cascade (combine) above the higher of the two settings. So if the AVR crossover is set to say 80 Hz, and the PB13-Ultra low pass filter is set to 120 Hz, the initial slope of the subwoofer roll-off will be 24 dB/octave above 80 Hz, increasing to 36 dB/octave above 120 Hz.


Finally, I think I get it!


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## bone215 (Dec 15, 2006)

so, there is no problem with using both, it just introduces a different slope


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## atledreier (Mar 2, 2007)

And a lot of group delay too.


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## Ed Mullen (Jul 28, 2006)

bone215 said:


> so, there is no problem with using both, it just introduces a different slope



Right - it won't hurt anything; it just might not produce optimal results. Of course the in-room FR is really all that matters in the end. Get the transition flat between the speakers and the subwoofer and you're there.


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## Ed Mullen (Jul 28, 2006)

atledreier said:


> And a lot of group delay too.


While cascading the filters will always add GD, the in-room FR is more important than looking at the phase effect of filters in isolation. 

The goal is a smooth transition between the speakers and subwoofer - something which is exceedingly difficult to achieve even under the best of circumstances. 

The original THX standard required a sealed speaker with a 12 dB/octave acoustic roll-off starting at 80 Hz. The 12 dB/octave high pass filter in the AVR is cascaded with the acoustic roll-off of the speakers, resulting in a 24 dB/octave roll-off. The subwoofer low pass in the AVR is 24 dB/octave. So in theory the transition between the speakers and subwoofer is phase-correct. 

Of course these days most enthusiasts use vented speakers which are flat to frequencies lower than 80 Hz and then roll-off more steeply than 2nd order below the system tuning frequency. So this presents an entirely different in-room speaker response which is often inconsistent with the subwoofer roll-off and the original intent of the THX standard. 

In some cases, it might actually be useful to roll-off the subwoofer more steeply than 4th order, if the speakers are not acoustically rolling off 2nd order at the selected crossover frequency. So that's why I recommend looking at the system as a whole (speakers/subwoofer/room) rather than individual sub-systems and components. Very good results can often be achieved with unconventional approaches and techniques.


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## bone215 (Dec 15, 2006)

I have tried system with settings of avr at 50 hz,80 hz and 100 hz. A little tighter at 50 and a little fuller at 80.

Also listen with two ports plugged and running sealed.
I also tried 20 and 15. I prefer 80 hz and running at 15 hz with one port plugged.
It is great to be able to play around and hear the system in different configurations.
It is all good.


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## bone215 (Dec 15, 2006)

I am now trying fronts and surrounds to large with sub x over on the avr set to 50hz.
I love playing with this sub.:whistling:


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