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Using 2 Subs

Discussion in 'Subwoofers' started by Northmoorblue, May 28, 2004.

  1. Northmoorblue

    Northmoorblue
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    Other than the obvious answer are there many reasons that you would have two subs set up in a system?

    I have a KEF PSW2500 & a Rel Strata 3, and was thinking that I need to sell one of them, as I wouldn't need two.

    Does it add much to the overall effect?

    Is it worth me trying my set up with the two, if so how would they both be connected up ?

    Northmoorblue
     
  2. Ian J

    Ian J
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    The improvements are subtle rather than dramatic if you get it right. Many people seem to have problems positioning one sub though but two gives rise to even more problems as if you get the positioning wrong the bass will be cancelled out and you will end up worse off and not better.

    You will need a Y connector from the sub output on your amp to feed the two subs
     
  3. chrisgeary

    chrisgeary
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    what are you trying to achieve? what are the characteristics of your room?

    i have had moderate success using two subs in my room. i currently use one, but im thinking about revisiting two again. my room is horrible: reverberant and rented (so i can't do anything structurally about it!), but when i had a strata III, i also had (have) a quake, and i had some success evening out the room response. its really hard work though, its hard enough with one sub integrating it with your mains, but add another, and a BFD and you have too many variables to deal with.

    i would be interested to know what your thinking is for using the other sub - depending on your room, your Strata may well be better off on its own.

    Chris
     
  4. Ed Selley

    Ed Selley
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    My 2 (located for the simplicity of description at opposing corners) work rather nicely but I suspect that blind luck played a role as very little tweaking was required to get a flat response out of them. You may not be as lucky.
     
  5. Northmoorblue

    Northmoorblue
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    Chrisgeary

    I am not trying to achieve anything in particular, I Am a novice in home cinema and am just trying to get an understanding of why you would use 2 subs. If the improvements are subtle, then i probably would not appreciate the difference, and would be better off selling one of my subs and spending the money towards upgrading my system elswhere.

    Northmoorblue
     
  6. swartzy

    swartzy
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    My system

    Tannoy M3 Fronts
    Tannoy M3 rears
    Tannoy MC Centre.....Tannoy MX10 sub linked to the centre High Level
    Tannoy MR Front Effects
    MJ Acoustics Ref 100 Sub low level phono cable
    Yamaha DSP-AX2 Amplifier

    I too just bought an mj acoustics Ref 100 sub and was intially thinking of replacing my Tannoy sub until I read and article on their site which I followed up by a phone call and they were very helpful.....they suggested hooking up one of my subs to the centre speaker via speaker wire i.e. high level connection and one on low level phone connection to my amp....I am very pleased with this as it has not only brought my centre speaker to life but has had a sharper more detailed sound on my overall system and I also found the bass was very much more controlled...I am very pleased with the result

    hope this may be of help

    thanks
    swartzy
     
  7. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    The reasons to use two subs are:

    To get increased sound pressure.
    or
    To get even response in listening positions. If it's not possible to position one sub in the spot where it give the flatest response you may be able to position two in such a way as to create a "virtual sub" in that correct location. For instance it might be that the best place for one is 5ft out from left corner of room and then another 5 ft off wall. Most folk wouldn't want a sub in the middle of the floor......by understanding how bass works you could position two subs and calibrate them to behave as if there was a sub in that location even although the subs would be against the walls,.....clever eh?

    Gordon
     
  8. Northmoorblue

    Northmoorblue
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    Thanks for your tip Swartzy might try that.

    Gordon is there an art to positioning a sub to give the best performance, or is it trial and error? You mention positioning a sub to give the flatest response. What does this sound like? I presumed the sub should be placed in a corner of a room or near to one wall. Does it sound that much different if it is moved around. What type of response am I listening for?

    I have a rectangular room approx 5mts x 3.5mts. The TV above the fireplace in the middle of one of the 3.5mtr walls.
     
  9. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Positioning subs has been discussed on the forum before I think. Here's a synopsis.

    You will find that in your room there will be areas where one or two or more frequencies will be exagerated or diminished relative to the rest. These will be peaks and troughs caused by the room dimensions you have and how the sub-woofer interacts with the room itself(they are called room modes). Ideally you want to be able to sit anywhere in the room and hear all frequencies played back at the correct level. This is never going to happen though. So ideally you then would want to get it even over as large a listening area as possible...or just at your own listening position. You may find that once you have it nice sounding at your listening position if you then sit 3ft away it could be a boomy mess.....so how do you do this.

    Well it's not that simple. To hear the difference in levels do this, stick a pink noise full frequency test tone through the sub and turn volume up to a decent level. Now get up and walk around the room. You'll find that in some spots it's louder and in some spots it's quieter......Put the sub in a corner to do this then go and stand in a corner and I bet it's LOUD. Then walk along a wall and you'll hear the effect the room has.

    With test tone generators and Real Time Analysis you can pin point what frequencies are the problems and work out methods to position sub or subs effectively. Without these tools try this.

    Get a long interconnect. Put the sub on your chair at your listening position and send it the test tone again. Walk around the room listening for the peaks and troughs. If you have a pressure meter you could use that I suppose. Find the area's that are not quiet or boomy. Mark them. These are the areas where you could put the sub and you would hope to get the same sort of response at your seating position.

    Hope that's some use.

    Gordon
     

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