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TMREQ with two subs

Discussion in 'TAG McLaren Audio Owners' Forum' started by Emmanuel, Jul 20, 2004.

  1. Emmanuel

    Emmanuel
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    What is the best procedure to follow to set up TMREQ with two subwoofers ? Thank you in advance for the explanation.
     
  2. Teejoo

    Teejoo
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    I suppose the same as with one sub, since they both get the same signal and you measure and correct the result of both subs.
     
  3. Emmanuel

    Emmanuel
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    If I remember correctly it's not that simple because interaction between each sub and the room is huge and very dependant of their placement (which is different for each sub). I think I read on the old website forum that it was better to measure them separatly but I'm not sure. If I'm wrong, then I'll try your advice. Thanks.
     
  4. Stevesky

    Stevesky
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    My strategy for twin sub setup.

    1. I measure each sub individually, without the main speakers on. My first point of attack is to ensure that the subs are suitably position as no amount of EQ'ing will compensate for bogus positioning. Basically keep on moving them around and remeasuring inspecting the decay times across the spectrum, you want to aim for as consistent as possible. Once you're happy with each individuals speakers position measure with both of them on and again fine tweak positioning. Remember that large peaks you can EQ out, huge cancellations you can't!

    2. Do the following low frequency measurements:
    Left + Subs
    Right + Subs
    Left+Right + Subs
    Subs only.
    Left Only
    Right Only
    Left+Right Only

    I personally do waterfall measurements at listening position and at various distances away so to get a better picture of whats really going on in the room. Single point measurement can be problematic and can have you over compensating for things that are just a localised issue.

    3. I then print them all out and mark out the frequencies that have excessive decay times and from all the permutation of measurements you can also work out the best speaker to apply the compensation to. There are some frequencies where it becomes complicated as it's a mixture of your mains and subs interacting together.

    4. Launch the TMREQ wizard with the Subs only plot and I manually pick the frequencies that my subs are stirring up. Use the wizards auto feature to pick the correct Q and gain and then manually adjust them if you don't like the fit its done. I then load them into the AVP and individually switch each one on and off when playing music - if I can't hear any difference then I use the filter for something that I can hear.

    5. Do the same for your left only and right only measurements.

    6. You're now left with the tricky ones that are a mix of sub and mains. What I do with these is based on trial and error of 1/2 correcting on the subs and then remeasure. If things haven't got any better then remove the correction and re-apply to your left/right. It's then a case of recursing around finding a sensible balance between the two.

    7. Remeasure Left+Subs, Right+Subs and left+right+subs and view it as a waterfall plot. Ideally the decay times should be more consistent. If not start examing your filters to work out where you went wrong!

    8. And finally make sure it sounds ok to your ears by listening to some music or playing your fav movie. You may find that a bit of under correction around the 70-90Hz area may be more pleasing to the ear as some modern recordings use typical room resonances to give a perceived fuller sound from small speakers as found on consumer systems. ... it's your call!

    To get real improvements doesn't take that long, to really optimise things turns into a part time hobby!
     
  5. Stevesky

    Stevesky
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    One other thing I forgot to mention, it's worth looking at the low frequency roll off of your systems. If your subs can go very loud but are starting to roll off a bit early a strategically placed low shelf filter set at about +3 to +4dB can extend the inroom frequency response at the expense of maximum SPL. You don't want to clip the amp or make the drivers in the subs hit their end-stops though.
     
  6. Emmanuel

    Emmanuel
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    Thanks Steve, very useful and complete explanation. It looks like I'll spent the next week ends playing with ETF...
     

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