Bass management question

Discussion in 'GENERAL AV Discussions' started by Goliath, Apr 7, 2013.

  1. Goliath Full Audioholic

    Goliath
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    Just wanted to ask a question. If you have set all speakers to Large in a HT system there is no crossover involved. So if you are using a subwoofer and the LPF is between 70 Hz - 180 Hz, if you select 70 Hz would that be the best option using this configuration?
  2. Grador Audioholic Field Marshall

    Grador
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    If you're receiver has bass management and you're going to use it, the subwoofer's LPF should either be set to it's highest position or disabled if possible. Your receiver will be doing the crossover for you, the subwoofers low pass filter would just be getting in the way.
  3. Goliath Full Audioholic

    Goliath
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    I'm trying to help my friend out, but I'm having difficulty understanding how he has set up his system. He has a Rotel RSP-1065 processor and has run all speakers as large apparently.

    He told me that the subwoofer lpf has been set to 40 Hz with all speakers set to Large. At the back of his subwoofer he is using the lowest lpf available, which is 70 Hz. But I looked in the RSP-1068 manual and I can't find any user adjustable lpf for a subwoofer unless speakers are selected as Small.

    Either he is confused, or I can't find this user adjustable lpf. He is happy with his sound, but I'm trying to help him get better sound out of his system. Can someone help me out?
  4. twoeyedbob Audioholic

    twoeyedbob
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    The general consensus is that even with the best spkrs on the planet..they should be set to small...that'll give you full control
    Of your sub..and give the amp/receiver an easier time..
    Sub's are designed specifically to deal with
    stuff under 60-80 hz...normal speakers aren't..at
    Least not to the same degree.
    If he's got really good spkrs then set it to small and 40/50hz


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  5. Pyrrho Audioholic Ninja

    Pyrrho
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    The only time it makes sense to run the main speakers as "large" is when they are at least as capable of deep bass as the subwoofer. Otherwise, one will be losing some of the deep bass in the main channels that one would get if one would redirect the deep bass to the subwoofer.

    The way the processor should work is that all of the LFE channel (the ".1" in a 5.1 or 7.1 system) goes to the subwoofer, and consequently there would be no bass management selection if one sets all of the other speakers to "large" ("large" means that the entire frequency spectrum of the channel is sent to the speaker, so there is no bass management used in this case). So I think you are reading the Rotel manual correctly, and that your friend is confused, and is in fact diminishing bass above 70 Hz in the LFE channel with his system set up as you describe.

    In other words, your friend is missing out on bass (that he could get from his system) in every channel with things set up the way he has it, unless his main speakers are as capable of reproducing bass as his subwoofer, in which case he is only missing the upper bass of the LFE channel. But unless he has great main speakers (or a really lousy subwoofer), his main speakers are worse at reproducing deep bass than his subwoofer.

    Edited to add:

    If you want advice on the proper settings specific to your friend's system, we would need to know what speakers (including subwoofer) we are discussing. Generally speaking, one should select a crossover frequency above the -3dB point of the bass response of the main speakers. For example, I use bookshelf speakers with a frequency response of 50-40,000 Hz +/-3dB, and therefore I should select a bass management frequency above 50 Hz. I have mine set at 80 Hz. If my speakers had a -3dB point of 30 Hz, I would probably select 60 Hz for the crossover point, though 80 Hz would still be okay. It is best to not go much higher than that, because otherwise one may be able to locate the subwoofer by sound alone. But if the main speakers cannot go that low, either one sets the subwoofer to go higher, or one diminishes the bass between the crossover point and the low end of the main speaker. The former is preferable (i.e., setting the crossover higher, so that one gets all of the frequencies at approximately the correct level, insofar as one's system is capable of reproducing them).
    Last edited: Apr 7, 2013
  6. Goliath Full Audioholic

    Goliath
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    Thanks for the comments. I was hoping someone could work out for me on this Rotel processor (RSP-1065). If you select Large speakers can you select a subwoofer low pass? Its a little confusing for me.

    Here is pdf : http://www.rotel.com/content/manuals/rsp1068.pdf
  7. twoeyedbob Audioholic

    twoeyedbob
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    Did you actually read any of the above ?
    Set spkrs to small...end of

    You dont need a low pass x-over for sub...there will be a already be one on rear of sub

    If i've not even bothered to read my own pdf manual
    (On a smartphone) i'm certainly not reading your's

    Sent from my HTC Vision using Tapatalk 2
  8. Goliath Full Audioholic

    Goliath
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    I'm just asking for help so I can understand my processors settings. What is the problem? If you don't want to help then don't post, simple as that. :rolleyes: I'm aware of the "Small/Large" debate. I am trying to understand how the processor is functioning with Large and the low-pass filters to the sub, hence why I sent the PDF.

    If someone can help it would be appreciated. Sheesh.
  9. twoeyedbob Audioholic

    twoeyedbob
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    Page 37

    When a speaker is set to LARGE on the SPEAKER SETUP menu or on this MENU, the crossover setting is not available since, by definition, a LARGE speaker plays fullrange with no bass redirection to the subwoofer and no crossover. Likewise, the OFF setting for the subwoofer crossover is not available for SMALL speakers, since SMALL means that the speaker will redirect its bass below a given crossover point to the subwoofer. In addition, the CROSSOVER setting is not available for the MULTI INPUT
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  10. Goliath Full Audioholic

    Goliath
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    If I had to set front speakers to Large and all other speakers to Small (let's say 60 Hz) would the subwoofer low-pass still be set for speakers set to Small, at 60 Hz? Or does it only apply if all speakers are set to Small? Thanks.
  11. Goliath Full Audioholic

    Goliath
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    Sorry just to add : if I select all speakers as Large then the subwoofer will ONLY handle the LFE channel? So there will be no low pass filtering going on besides the LPF on the subwoofer preout, which is 120 Hz in most cases?
  12. twoeyedbob Audioholic

    twoeyedbob
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    Spend some time mucking about with the receiver itself
    ,and most of this stuff will become clear..
    There's so much going on in receiver's these days
    That unless your actually hands on ,it's very difficult to get a grip on exactly how things work.


    Sent from my HTC Vision using Tapatalk 2
  13. Goliath Full Audioholic

    Goliath
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    I may be a complete idiot, but looking at the manual I don't see any mention of the LFE low pass filter. There is a low-pass for the subwoofer from 40 Hz - 200 Hz but that does not affect the LFE according to the manual. So if all speakers are selected as Large, what would the LFE be low-passed to? I have no idea.
  14. Pyrrho Audioholic Ninja

    Pyrrho
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    If the processor allows different settings for different channels, then the bass for the channels set to "large" will be sent to those channels (and not the subwoofer) and the ones set to "small" will be whatever crossover frequency is selected and the deeper bass from those channels will go to the subwoofer.




    If you select "large" for all speakers, the subwoofer will only get the LFE. Since the LFE channel is limited in frequency response already, there is no need for the receiver to filter out high frequencies from it; they simply do not exist in the channel. So there is no filtering of frequencies at all in such a case.


    There is one further complicating factor in this, and that is that many processors allow one to select sending the bass to both a subwoofer and to the main speakers; typically, this is in the setup where for subwoofer one selects "both" rather than "yes" or "no." Usually, it is a bad idea to make use of this feature, but many people like things set to alter the original frequency response, so such features are often included.
  15. Goliath Full Audioholic

    Goliath
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    Thanks, and makes sense. Do you know what the low pass of the LFE would be? Because I don't see any mention of it in the manual. It's an old processor.
  16. Goliath Full Audioholic

    Goliath
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    Sorry, please correct me if I'm wrong but if I select 70 Hz low-pass on the subwoofer, then you are throwing away information in the LFE? The LFE is 120 Hz and down is it not?
  17. twoeyedbob Audioholic

    twoeyedbob
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    Crossover is the dividing line...above goes to spkrs..below goes to sub..
    The only time you'll lose anything (as such) is if your spkrs
    Arent capable of dealing with some of the bass they are
    Being asked to reproduce.


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  18. Goliath Full Audioholic

    Goliath
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    Yes but the LFE has information up to 120 Hz. I would imagine if you set the sub low-pass to 70 Hz that you would be throwing information from 70-120 Hz. Wouldn't that be the case?
  19. twoeyedbob Audioholic

    twoeyedbob
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    80hz is the standard ...are you suggesting that everyone on here has a big chunk between 80-120hz missing ?


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  20. Goliath Full Audioholic

    Goliath
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    I read that LFE has a upper limit at 120 Hz. So if you set 80 H for the low-pass on the LFE channel then you ARE chucking away bass in the LFE from 80-120 Hz. Does that not make sense?

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