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Bass issues (small versus large and stereo vs 5.1)

Discussion in 'Hi-Fi Stereo Speakers' started by darren204, Apr 28, 2003.

  1. darren204

    darren204
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    Hi guys,

    I have a pair of mission 780s set to large on my yamaha amp. The centre and rears are set to small and sub is on.
    The sub (Rel q150) is connected by both the hi and lo level inputs.

    The problem I have is this. When using the amp in stereo mode I get some nasty boom from the front seakers at around 50-60hz (This is probably due to them being in a bay window).

    So, I thought I would set them as small and let the sub do the bass. This does improve things from the 5.1 point of view. But when I switch the amp to stereo mode, the output from the sub increases by about 10db.

    If I turn down the sub level in stereo mode, I get the desired effect, but I don't want to have to keep changing levels and settings just to change between cd and dvd listening.

    Does any of this make sense? ...and can anyone help?

    Any ideas appreciated (although I don't want to spend anything!!!)

    Thanks

    darren
     
  2. nathan_silly

    nathan_silly
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    Your Mission LF corner is 65hz. Can you set the bass crossover to 60hz on the AV amp?

    And try 65hz crossover on your subwoofer.

    With your speakers I'll set them to small.

    You could use high-level for music, low level for AV. Set high-level volume alot lower.

    Perhaps the subwoofer is getting dual-inputs- for stereo does the LFE pre-out still send a signal out?

    [edit] what have you set the sub crossover to?
     
  3. darren204

    darren204
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    Thanks for the reply.

    Unfortunately, I cant adjust the x-over on the amp (Yamaha, fixed at 90hz)

    The missions' freq. response is indeed 65hz (but, in the real world they go a tad lower).

    The problem is with boom in the bay window at around the lowest freq the speakers produce and not from the sub.

    My sub's hi level crossover is set to 57(ish) hz.

    With amp in stereo mode and speakers set to large the amp does not output any signal to the sub out.

    However, if I set speakers to small, I lose the boom from the bay window, but the output from the amp to the sub is higher (by about 10db) than it is when I switch it to 5.1

    What I am trying to avoid is having to remember to change settings on my amp when I change from stereo to surround.

    I hope I am making sense, but I am now beginning to confuse myself!

    Thanks
     
  4. Jase

    Jase
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    Which Mode have you got the sub set to? Ideally, you want to be using Mode 2 or 4. This ignores the sub's crossover at the low level input. This will then leave you free to set the High Level volume and crossover to the ideal settings.
     
  5. darren204

    darren204
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    The sub is set to mode 2.

    There isn't really a problem with the sub per se.

    The problem is with deciding whether to have main speakers set to large and live with the bass boom they produce in the bay window.

    or

    setting the main speakers to small and having to adjust the the level of bass sent to the sub via the lo level feed when I switch between 5.1 and stereo.

    ...Calling uncle eric?...
     
  6. nathan_silly

    nathan_silly
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    I would go for ...... "setting the main speakers to small and having to adjust the the level of bass sent to the sub via the lo level feed when I switch between 5.1 and stereo."


    I even had problems using Kef Q55's set to large- so I would guess small standmounts like the Mission 780's will strain when setting to large.
     
  7. Jase

    Jase
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    I'd go for the latter option as well, rather than suffer boomy bass.
     
  8. Triggaaar

    Triggaaar
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    Sorry to butt in, but an off topic question for you Darren. I'm planning on putting an av system in a bay window, but its not my only option. How close are your speakers to the bay, and are you getting more boom than if they were the same distance from a standard wall?

    Thanks
    Mike
     
  9. uncle eric

    uncle eric
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    Darren,
    This is another classic example of small speakers trying to do too much. To explain.
    By design, Mission tried to squeeze a fair amount of bass from this small speaker and really have not been successful as far as quality of bass is concerned. The vast majority of todays standmounts, including and especially these missions, should be set to small and crossed over higher up the frequency range before they make a mess of the lower frequencies. Each standmount varies but THX's 80Hz mark is a good starting point for many.

    Also, when set to large, your Missions produce (not very clean) mid bass which interacts badly with their environment, and particularly with your problematic bay window placement. Higher freqencies are much less effected by room interaction hence the cleaner sonics you are hearing when set to small.

    I would experiment with your sub and amp and try to find a way to overcome the 10dB difference you are getting in Stereo mode. Have you tried disconnecting the high pass?

    Heres a thread explaining in depth the pro's and cons of small and large speakers and settings.
    http://www.avforums.com/forums/showthread.php?s=&threadid=62508&highlight=small+or+large
     
  10. darren204

    darren204
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    Uncle Eric,

    Thanks for your reply. This is pretty much what I feared you would say!
    I think my problem is wanting a "one size fits all" solution for both stereo and surround.

    When you say disconnect the high pass, do you mean the speaker-level feed to the sub?

    Have you encountered this problem (different levels of bass being sent to sub in different lstening modes) before? If so, do you have any solutions that will enable me to just switch between stereo and surround with out having to adjust the sub level?

    I have tried various ways of getting the sub level right with all speakers set to small.

    1. Set the amp to stereo mode. (Speakers small, bass out: SW) Play a bassy cd and adjust bass to taste. This sounds good in stereo. But, in 5.1 the bass redirected from front, centre, surround is weak. (Although I can get the .1 channel to a respectable level)

    2. Set amp to pro logic. Play same cd as above. Adjust sub to approx same level of bass as before. (All redirected bass in surround modes is good and .1 has to backed off a bit). But, when I switch to stereo, sub output is overblown and needs to be backed off 8-10db.

    Is this something to with my amp setting the bass output in line with the level of the quietest speaker (surrounds are set to -8db) when in surround mode?


    Triggaaar,
    sorry for not getting back to you sooner.
    I would certainly try bay window placement if that is your preferred location.
    My room is boomy anyway, but the bay window placement pushes it over the edge. It may not be such a big problem for you.
     

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