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Sub setup questions

Discussion in 'Subwoofers' started by michaelab, Feb 18, 2003.

  1. michaelab

    michaelab
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    Apologies as I know this subject has been covered in some detail before but I haven't really found the answers to my questions yet!

    Just got my MJ Acoustics Pro 50 yesterday and started to fiddle around with the setup.

    Connections:
    I mainly want the sub for music duties so I have it connected via the hi-level inputs to my stereo amp's speaker terminals. I use my stereo amp to drive my front AV speakers aswell. If I was just going to use the sub for 2ch music then I'd have the xover at around 50Hz and that would be that. However since I also want to use the sub for movies I appear to have 4 options:

    a) leave xover at 50Hz, set fronts to "large" and sub to "no". The LFE channel would get sent to the fronts and the sub would do it's thing just as it would with any other LF stuff.

    b) connect the lo level input to the 'sub' output on my receiver (Marantz SR4200), wack the xover up to 100Hz (the fixed xover of the Marantz) and set my fronts to "small" and sub to "yes". However, when just listening to music (where the Marantz doesn't come into play) this is less than ideal as my main speakers and the sub would be duplicating between 100 and 50Hz.

    c) connect the lo level input as in b) but leave the xover at 50Hz and set fronts to "small" and sub to "yes". That would solve my problem with music but would mean that in movies I wouldn't get anything between 50 and 100Hz! (because the Marantz would cut the mains off at 100Hz and the the sub wouldn't kick in until 50Hz).

    d) all settings as in c) but leave the fronts set to "large". I can't really see how this would be any different to a) other than the LFE channel would now get sent via the lo and hi level inputs - which seems pointless.

    So far a) seems like the most sensible option to me, leaving the xover to the sub and not letting the Marantz have to worry about bass management at all :) However, when someone (on another forum) asked MJ Acoustics a similar question they seemed to suggest that b) was the best compromise option. Comments?

    Phase setting:
    The Pro 50 is a down firing sub and the MJA manual says that down firers should generally have the phase angle set to 90deg. However, in fiddling with it I found that if I have the phase set to 0deg the sound from the sub is much louder - esp. at frequencies where the main speakers aren't even doing anything yet :confused: Surely the phase adjustment only affects how the sub interacts with other speakers and not when it's working on its own?? I have left it at 90deg for now.

    I guess I'm really only going to get it properly sorted with an SPL meter (I already have a test tone CD).

    BTW, the sub is placed more or less next to the right front speaker, inside the soundstage ie to the left of the right speaker. It's about 40cm from the rear wall and about 60cm from the side wall.

    Michael.
     
  2. S H A D O

    S H A D O
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    Has the MJA Pro got the Mode Switch and seperate Volume controls for the High & Low level connections a la REL??
     
  3. michaelab

    michaelab
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    It doesn't have the mode switch but it does have separate gain controls for hi and lo level inputs.

    Michael.
     
  4. S H A D O

    S H A D O
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    Slightly scuppers me then. The mode switch on the REL´s mean you can bypass the subs internal crossover at low level (lets you set the amp to all speakers small, all bass to sub and have the amp control the cutoff frequency). This works well for movies.

    That leaves you free to set the High level crossover and volume to wherever you want for music, handy for Direct modes etc.
     
  5. S H A D O

    S H A D O
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    Of the options you´ve listed I´d go for Option A. You shouldn´t lose any bass or have any duplicating of bass. Only potential problem might be the volume level difference between movies & music. You may find that once balanced for movies there may be too much (or too little!) bass for music.
     

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