# Rotel RSP-1068 bass management



## Doctor X (Apr 3, 2007)

Hi,

I need some help figuring out this processor. I looked at the manual but I need a second opinion as it is very confusing to me.

http://www.rotel.com/content/manuals/rsp1068.pdf

If I select Small options, it says it will apply a low pass filter to the subwoofer and to the main speakers. But what if I select Large for the main speakers and small to the center and surrounds? 

Could someone please double check for me?


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## Doctor X (Apr 3, 2007)

Anyone?


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> Hi,
> 
> I need some help figuring out this processor. I looked at the manual but I need a second opinion as it is very confusing to me.
> 
> ...


The wording is poor.
It will apply a *high*-pass filter to any channels that are set to Small. The low-frequencies that are removed from those channels will be routed, via *low*-pass filters, to the subwoofer (or to the front L/R speakers if they are set to LARGE and there is no subwoofer). 

Do you have a sub?


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## Doctor X (Apr 3, 2007)

My friend has this processor but he tells me that he has set all speakers to Large and a low-pass filter to 40 Hz. He does have a subwoofer, but I don't know how he is able to do that. He said he set the processor low-pass to 40 Hz in the subwoofer menu.

The manual doesn't say that the low pass is adjustable if speakers are all set to Large, unless I can't read the manual properly. If all speakers were set to Large, wouldn't that mean the subwoofer only handles the LFE? So there is nothing else that it could low-pass


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> My friend has this processor but he tells me that he has set all speakers to Large and a low-pass filter to 40 Hz. He does have a subwoofer, but I don't know how he is able to do that. He said he set the processor low-pass to 40 Hz in the subwoofer menu.


Again, this is poor wording. The low-pass for the subwoofer is different from what I described above. It affects only the LFE input and not the rerouted channel information. In his case, there is no rerouted main channel info and the sub is playing only LFE. Therefore, I recommend that he reset it to 120Hz in order not to miss any of the LFE information.



> The manual doesn't say that the low pass is adjustable if speakers are all set to Large, unless I can't read the manual properly.


 See above.



> If all speakers were set to Large, wouldn't that mean the subwoofer only handles the LFE? So there is nothing else that it could low-pass


Yup.

Now, if some of the speakers are set to small, the bass below their crossover settins is rerouted to the subwoofer where it is combined with the LFE signals. Their crossover settings are entirely independent of the LP filter for the LFE (which should be set at 120Hz).


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> Therefore, I recommend that he reset it to 120Hz in order not to miss any of the LFE information


Like you said, if his speakers are set to Large then a 40 Hz low-pass setting wouldn't even take effect since the sub is only handling the LFE. I don't see any LPF of LFE on the Rotel, which is a separate story. 

The subwoofer preout is low-pass filtered to ...? Not sure. I imagine 120 Hz since that is the limit for the LFE.


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## Doctor X (Apr 3, 2007)

I mentioned to him that if you do not disable the low pass in the sub that it may cascade with the receivers low pass. His reply is that most speakers have passive crossovers within... so any crossover you setup on a receiver or a processor is in effect still/also cascading...

Any truth to that?


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> Their crossover settings are entirely independent of the LP filter for the LFE (which should be set at 120Hz).


That makes sense. But where in the manual does it state the LP filter of LFE?


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> I mentioned to him that if you do not disable the low pass in the sub that it may cascade with the receivers low pass. His reply is that most speakers have passive crossovers within... so any crossover you setup on a receiver or a processor is in effect still/also cascading...
> 
> Any truth to that?


No. Those crossovers are between drivers in each speaker box and do not apply to their overall low-pass or high-pass characteristics.



Doctor X said:


> That makes sense. But where in the manual does it state the LP filter of LFE?





Doctor X said:


> My friend has this processor but he tells me that he has set all speakers to Large and a low-pass filter to 40 Hz. He does have a subwoofer, but I don't know how he is able to do that. He said he set the processor low-pass to 40 Hz in the subwoofer menu.


I don't have a manual but why not ask your friend where he set his?


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> No. Those crossovers are between drivers in each speaker box and do not apply to their overall low-pass or high-pass characteristics.


Could you elaborate on this? Why do they not apply to the low-pass and high-pass characteristics? 



> I don't have a manual but why not ask your friend where he set his?


The manual is here : http://www.rotel.com/content/manuals/rsp1068.pdf

I've asked my buddy and he tells me all speakers are set to Large with a 40 Hz low-pass for the sub. I can't find anything in that processor that allows you to set the LPF of LFE. It's an old processor that does not decode DTS Master HD or Dolby True HD.

I might be a total idiot and overlooked it somewhere in the manual but I couldn't find it. BTW thanks for chiming in Kal. I love your work on Stereophile. Excellent reports as always.:clap:


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> Could you elaborate on this? Why do they not apply to the low-pass and high-pass characteristics?


The high/low pass characteristics of a speaker are consequences of its physical design. Its speaker only apportions the frequencies within that range among its drivers.



> I might be a total idiot and overlooked it somewhere in the manual but I couldn't find it. BTW thanks for chiming in Kal. I love your work on Stereophile. Excellent reports as always.:clap:


See pages 12 and 37.

P.S.: It is one of the worst-written manuals I've seen.


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> See pages 12 and 37.


I did and perhaps I misunderstand what they are saying. On page 37 it says :

_CROSSOVER (40Hz/60Hz/80Hz/100Hz/120Hz/150Hz/200Hz/OFF): This setting specifies a master low-pass filter for the subwoofer and a corresponding high-pass filter for all SMALL speakers in the system at the selected frequency._

So if speakers are set to Large then there is no low-pass in effect. If you select a 40 Hz low pass for the sub then there is a corresponding high-pass as well for all "Small" speakers. So the sub low pass only works when speakers are adjusted to Small, as I understand it from the manual.

I still don't see any mention of the low-pass filter for the LFE. If all speakers are set to Large and you have a subwoofer in the set up, what would the LPF of the subwoofer be? Because the above does not affect the LFE cut-off as I understand it.


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> I did and perhaps I misunderstand what they are saying. On page 37 it says :
> 
> _CROSSOVER (40Hz/60Hz/80Hz/100Hz/120Hz/150Hz/200Hz/OFF): This setting specifies a master low-pass filter for the subwoofer and a corresponding high-pass filter for all SMALL speakers in the system at the selected frequency._
> 
> ...


Read the small print. There is an option to customize the filters.


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## Doctor X (Apr 3, 2007)

*NOTE* : "_The master crossover point can be over-ridden with a custom crossover frequency for the front, center, surround, or surround back speakers in the ADVANCED SPEAKER SETUP menu; _"

Is this what you were referring to? If it was then I still don't understand because speakers are set to Small here. I am referring to the low pass of the LFE.


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> *NOTE* : "_The master crossover point can be over-ridden with a custom crossover frequency for the front, center, surround, or surround back speakers in the ADVANCED SPEAKER SETUP menu; _"
> 
> Is this what you were referring to? If it was then I still don't understand because speakers are set to Small here. I am referring to the low pass of the LFE.


Set this for LFE (120Hz) and then go to the ADVANCED SPEAKER SETUP menu and set what you want for those.

Again, I appreciate your concerns as this is a really dumb arrangement.


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> Set this for LFE (120Hz) and then go to the ADVANCED SPEAKER SETUP menu and set what you want for those.


This is all very confusing. I assumed the low pass filter for the sub could only be adjusted if speakers were set to Small. I've never encountered a processor that could allow you to adjust the LFE low-pass to 40 Hz. That would be the dumbest thing that I've ever heard of as it would truncate the LFE channel from 40 Hz to 120 Hz. 

Hence it doesn't make any sense. Hence my concerns that the 40 Hz low-pass thing couldn't possibly work. According to what I see, there should be nothing for the sub to low-pass if all speakers are set to Large. Hence my second opinion from you.


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> According to what I see, there should be nothing for the sub to low-pass if all speakers are set to Large. Hence my second opinion from you.


LFE.


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## Doctor X (Apr 3, 2007)

So you are saying that the 40 Hz low-pass for the subwoofer is for the LFE, assuming all speakers are Large? If that's true then that's bonkers. :unbelievable:


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## Kal Rubinson (Aug 3, 2006)

Doctor X said:


> So you are saying that the 40 Hz low-pass for the subwoofer is for the LFE, assuming all speakers are Large? If that's true then that's bonkers. :unbelievable:


????? I do not know why we are not communicating. I gathered from your/our previous posts that you understood the relationship of LFE to bass management.


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> I do not know why we are not communicating. I gathered from your/our previous posts that you understood the relationship of LFE to bass management.


Apologies, I misunderstood. So the sub is then only handling the LFE low-pass. That makes sense, but the question remains, at what frequency. In most modern receivers you are able to adjust the low-pass for the LFE. 

Sorry for this back and forth, I just find this whole processor set up fascinating and also irritating at the same time!


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## Doctor X (Apr 3, 2007)

Kal Rubinson said:


> The high/low pass characteristics of a speaker are consequences of its physical design. Its speaker only apportions the frequencies within that range among its drivers.


So what you are saying is that the passive crossover between the drivers are so outside the operating bandwidth of the amplifiers high-pass/low-pass filters that there is no interaction or cascading of filters.

Correct?


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