Another Subwoofer setup question...

Discussion in 'Subwoofers' started by SergioRZ, Jun 24, 2005.

  1. SergioRZ

    SergioRZ
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    Hi all! :hiya:

    I have this setup:

    - Yamaha RX-V650 receiver.
    - Pioneer DV-575A DVD player.
    - Two pairs of Wharfedale 9.5 floor standing speakers (front and surround)
    - One Wharfedale 9.CS center speaker (placed directly below the TV).
    - A pair of Wharfedale 9.0 front presence speakers.
    - One Wharfedale SW150 subwoofer.
    - Profigold Subwoofer cable (rca-rca).
    - Chord Carnival Silver Plus cables on all other channels.

    My receiver has these settings:

    - Center speaker set to SMALL
    - All other speakers set to LARGE
    - Bass Out: SWFR
    - Crossover at 60hz

    - Subwoofer Phase, that can be set to NORMAL or REVERSED.

    The sub has its own crossover, currently set to 85hz (maximum), and volume control (set at around 45%). And it has a phase control with two options: 0 or 180.

    I'm having real trouble setting the right phase for the subwoofer.

    - First of all, how do the phase controls from the receiver and the subwoofer interact? They cancel each other?

    - How can I tell if the subwoofer is in phase?

    I tried all possible combinations with the phase controls on the receiver and on the subwoofer. I get two possible results:

    1 - Louder bass, but a lot more "boooom" effetc, and the bass sound lasts longer (it seems). If I touch the subwoofer cone, and one front speaker bass cone, they don't seem to be quite in synch with each other.

    2- Quieter bass (just a little), almost no "boooom" effect, and a more instant sound (bass lasts less time). If I touch the subwoofer cone, and one front speaker bass cone, they seem to be more in synch with each other.

    Which would represent "in phase" situation? 1 or 2?

    I like the impact of situation 1, but not the boooominess...

    By the way, my subwoofer is placed on the side of the left front speaker, in perfect alignment with the front speakers, It has a wall behind (like the front speakers). I'm sitting by the opposite wall.

    Thank you very much for your help! :thumbsup:
     
  2. Jules Tohpipi

    Jules Tohpipi
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    If you have been making your observations whilst sat at your typical listening position then, technically, result one is the correct setting. However, the extra bass being generated (around the crossover frequency) might possibly be upsetting the room - by inducing standing waves - so ultimately there is no fail-safe formula here. Choose whichever setting you prefer.
     
  3. SergioRZ

    SergioRZ
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    Thanks for your reply :)

    Ok, so it's down to my listening preferences.

    I might go for the option with less boominess. Still, I've read about possible frequency cancelation is the sub is out of phase with other speakers in the room, meaning some sounds would be lost. Does this make any sense? Is that a risk if I choose the setup that makes the sub out of phase?

    Thank you! :smashin:
     
  4. Jules Tohpipi

    Jules Tohpipi
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    To explain what's going on here:

    You have your crossover set at 60Hz. Frequencies below 60Hz will go to the sub, those above will go to the main speaker set. However, it isn't a sharp knife cut at 60Hz - the changeover is a short but gradual one. Hence you'll find that at 65Hz both the main speakers and the sub are working. Similarly, at 55Hz, both the sub and main speakers will be working too. Either side of the crossover point (60Hz), the levels of both speakers are reduced such that the correct overall volume levels are maintained. Away from the crossover point, then each speaker is given the full monty. So it's a blend rather than a sharp cut.

    If the subwoofer is out of phase with the main speakers, then there will be bass cancellation through the 'blend' part - their respective outputs become equal and opposite (he said simplifying things) resulting in no perceived sound, at those frequencies, at the listening position. This is the mild bass drop you have witnessed. It is only a mild drop because it only effects a very limited frequency range (the crossover region) - not the entire bass output.

    The boominess you're hearing is probably as a result of a frequency being generated (around the crossover region) that's setting off a standing-wave (drone) in your room. This is a bad thing - hence you might want to run the sub out of phase to rid yourself of it.

    Once you have found a 'correct' phase setting, then you tackle your volume setting for the sub i.e. the phase ought to be set before choosing a final volume setting.

    HTH
     
  5. SergioRZ

    SergioRZ
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    Thanks for your explanation Lost Cause :thumbsup:

    Let's forget the crossover, because all my speakers are set to Large (now they are), meaning they get all the frequencies they should for their own sound channels and nothing is diverted to the subwoofer.

    That was the recomended setting by the YPAO system of the Yamaha RX-V650 receiver, and it makes some sense because the speakers are floorstanding and they seem to be able to cope just fine with all the frequencies...

    The Subwoofer is geting only the LFE (.1) sound channel, which ranges from 0hz to 120hz according to Dolby specs. This means there could be, and probably is, some frequencies output simultaneosly from the sub and other speakers, as they are all set to Large and they can output sounds as low as 20hz.

    So, if I understand correctly, the setting where the subwoofer is louder, and also booomier, should be correct phase.

    If I change phase on the subwoofer, I will loose frequencies because of mutual cancelation between sub and speakers when they output the same frequency range...

    Well, then I should keep the phase correct, and then maybe just try to lower the subwoofer output level to a setting that causes less booominess?

    By the way, if I move the subwoofer to the opposite side, in the back, inline with the surround speakers, phase seems to invert... it goes booomier with reversed phase, and quieter in normal phase. When the subwoofer was inline with the front speakers, it was boomier in normal phase, and quieter in reversed phase. Does this mean the correct phase depends on the subwoofer location? How can this be?
     
  6. Jules Tohpipi

    Jules Tohpipi
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    The 9.5s will start rolling-off around 40Hz (as the specs quote -6dB at 30Hz), so there's going to be about a 45Hz range where they overlap with the sub. Therefore there's no danger of losing deep bass - which is why you're not hearing all your bass go. Whilst the LFE channel should - in theory - just contain 'overspill' bass, in reality most directors spread deep bass across fronts and sub, rather than use the full potential of the fronts.

    "So, if I understand correctly, the setting where the subwoofer is louder, and also booomier, should be correct phase."
    Yes. (The test must be done with all speakers playing simultaneously - as you are currently doing).

    "If I change phase on the subwoofer, I will loose frequencies because of mutual cancelation between sub and speakers when they output the same frequency range..."
    Yes.

    "Well, then I should keep the phase correct, and then maybe just try to lower the subwoofer output level to a setting that causes less booominess?"
    Yes. However, if the boominess is due to a standing-wave being generated (which causes a massive hump in the response), then you'll have to turn the sub down so low that you'll hardly be able to hear it. Conversely, if it's not a standing-wave problem, then turning the sub down will help - because no bass is always going to sound 'faster' than bass (!)

    "By the way, if I move the subwoofer to the opposite side, in the back, inline with the surround speakers, phase seems to invert... it goes booomier with reversed phase, and quieter in normal phase. When the subwoofer was inline with the front speakers, it was boomier in normal phase, and quieter in reversed phase. Does this mean the correct phase depends on the subwoofer location? How can this be?"
    Bass frequencies have a long wavelength, therefore moving the position of the sub will alter what part of the wave hits you (a compressional peak or a trough). This is why the phase switch is there on the sub - to alter for phase inverting amps, and to correct for position differences between the mains and the sub.
     
  7. SergioRZ

    SergioRZ
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    Do you think I could benefit from setting the speakers to small, and crossover point to around 60hz? :confused:

    If the 9.5 speakers really can't play anything below 45hz, maybe I should divert some of the sound to the subwoofer... I think it could result in less stress to the speakers and the receiver.

    Well... on the other hand, maybe the front/center/surround channels in movies don't carry that much sound below 45hz... :suicide:
     
  8. Jules Tohpipi

    Jules Tohpipi
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    Your last line is the important one, I think. So, I'd keep the 9.5s set to large - I really wouldn't set them to small.

    Your set-up is 98% of the way there. Subwoofers do take a bit of playing around with because they interact with the room so easily. Start off with the sub correct phase, then see if you can find a level you are happy with - which doesn't cause an boom.

    If you can't get rid of the boom, then experiment with the positioning of the sub in different parts of the room - evaluate the results from the listening position. Due to the long wavelengths, bass levels will vary in different parts of the room - it's easier to move the sub than your listening position.

    If that fails, then you've tried all you can, and need to get rid of the frequency that's setting the room off. As you've already discovered, you can achieve that by playing the sub out of phase.

    Give that a try :)
     
  9. pedritopt

    pedritopt
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    Hello,

    My configuration is :
    9.5 in Front;
    9.4 Surround;
    CM as Center;
    SW150;

    So the 2 diferences from you :
    a) CM as Center;
    b) 9.4 Surround;

    My AV is Pioneer 2016...well I'm waiting for it...I've ordered last week and I think it would arrive at the begining of next week.

    I'm a little bit confused....
    in "theory" I think that front speakers and surrond should be set as large but I read that in "practical", the best choice is :

    9.5 Front as SMALL;
    CM as LARGE;
    9.4 as SMALL

    Why ? Because I think that this way the low frequencies will pass through the sub.
    If you put 9.5 (front) as LARGE The sub will have less impact I guess...On the other side I think if I put 9.5 as SMALL I will lost some 9.5 bass performance...

    But remember this is only in theory : things I've read from manual, opinions, it's not my experience...For that I will have to wait 2/3 more days :)

    Of course after that I will post my results here. Thanks for your opinion too.



    Best Regards,
    Pedro Santana (Portugal)
     

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