Anyone use dual centres?

Discussion in 'Home Cinema Speakers' started by Nic Rhodes, Feb 11, 2009.

  1. Nic Rhodes

    Nic Rhodes
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    It may sound a daft idea but is anyone using dual centre channel speakers? If so, what problems have you hit?

    Thanks
     
  2. Bald Monkey

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    Hi Nic, :smashin:

    For what reason?

    There seems to be a few people on here not using a center at all as it happens.. prefering a good pair of fronts for various reasons.. But I've not read about anyone with more than a single center.

    I presume more than one central speaker is the norm in large theaters?
     
    Last edited: Feb 12, 2009
  3. Nic Rhodes

    Nic Rhodes
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    I am now in the lucky position of owning 6 Genelec 1037s, obviously I short of one still for the full 7.1 system. If you look at their price you will see why though ;) I also have a 208 and a 1032a. Now it makes sense to have 1037 across the front but I could still use Kef Ref 4.2 as rears. This would leave me with a spare 1037 and as the centre channel is all important and my Genelec Di8a balanced box has one channel with dual balanced outs I wondered about 2 1037s up front, tweeters central. It is an important channel but worried by cancellations etc.
     
  4. Bald Monkey

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    Not 100% sure what you just said Nic :D

    But it's sounds like a great idea :thumbsup:

    Although in my very limited experience I can't help but wonder if it would be over kill?? But then I guess that's the point - Excess! :devil:


    {Off to google Genelec 1037s} ;)

    EDIT: Shame you can't swap 2 1037's for a 1038BC, Although I guess with rotating the DCW unit and using 2 1037's it could be even better :D Looks like an awesome set-up on paper !!
     
    Last edited: Feb 12, 2009
  5. Mark.Yudkin

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    Magnapan's MC1 system is based on a centre pair, thus demonstrating that it can be done when properly designed.

    However, if you simply plan on attaching two speakers to the centre channel output, you'll need to consider the consequences of running two speakers from one power amp as well as the possible cross-interference. It sonds like this is your idea, and I'd suggest careful auditioning to determine if it will work with your Genelecs.
     
  6. Nic Rhodes

    Nic Rhodes
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    Each Genelec has three separate power amps driving them so no problems there [Active pro gear, in fact they are pretty well bullit proof hence they are the speaker of choice in many profession recording studios]. They also gave the ability to modify bass, mid and treble levels as well as adjusting the acoustic axis to allow horizontal and vertical positioning via the DCW. So I have quite a bit of flexibility, long before any 'electronic' tweaks. They will be driven by dual balanced outputs.

    Not sure I follow the Maggs plan, is this really dual centres?

    Plan attached, really want to avoid lobing I think.
     

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    Last edited: Feb 12, 2009
  7. eviljohn2

    eviljohn2
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    TBH Nic, I don't think using 2 centre speakers in this situation would provide any benefit and would add unnecessary complexity (along with lobing and gain difficulties). The principal benefit to me would be better controlled dispersion but that's largely covered with the rotating treble/mid section of your speakers.

    It could be of value if you have a large non-permeable screen and used one above and one below to create a notional speaker right in the middle although you'd need a lot of care and control to manage delays between both units. Alternatively; in a very large listening area it may be useful to spread the centre image further but if that were the case the stereo image would be all over the place anyway. :)
     
  8. NonPayingMember

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    Genelecs are active so no probs there. Problems to be aware of are mid-range lobing effects where you will get inaccurate frequency response off axis. Bear in mind centre speakers which are horizontally opposed (i.e. tweeter between two mids) also exhibit lobing effects, you have to take the good with the bad and decide which is the best overall compromise for what you are trying to achieve. I've always been interested in the idea and done it on a small scale a couple of times usually for aesthetic reasons though more than anything. Having very wide LR speakers and narrower to the screen dual-centres, one each side (or in the case of something like the Artison speakers plasma side-speakers which cover LCR).

    I guess the best thing you can do is take the kit you've got and try it out!
     
  9. dj-dulux

    dj-dulux
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    Not a great idea for the reasons eviljohn2 and Joe state, good little set up, but please, please get them calibrated, all those dip switches on the back are there for a reason. You need a FFT style analyser, look at the genelec-ht site and you will find the guide...

    Dupe...
     
  10. Member 96948

    Member 96948
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    Would it not work if the centres were stacked vertically, thus restricting comb filtering effects to the vertical plane where they normally reside?

    Of course, the arrangement might obscure the screen through sheer height, but that wasn't specified as a restrictive criteria.:)

    Russell
     
  11. dj-dulux

    dj-dulux
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    It would certainly be better than having them side-by-side, but it depends a lot on the listening room and position of seating etc. You would still get time domain anomalies related to having 2 HF drivers doing the same thing and covering the same area. How noticeable this would be in the real world is still up for debate mind..... I can see a research project here….

    Dupe...
     
  12. eviljohn2

    eviljohn2
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    But how would that be a benefit Russ? Aside from doing it for a giggle of course. :smashin:

    By sticking them both directly next to each other you'll get a gain boost but with this level of equipment that's really not a big deal and would most likely cause more of a problem in balancing the gained centre pair to the other units. I think that uniformity is the key for surround sound really (especially across the front) and keeping everything as similar as possible would be the ideal. I use 3 identical active monitors across the front and even though the centre is on it's side and although I could add another if I wanted I really won't be bothering. Changes to a "perfect" system like this should be done for a reason or experimental purposes only. I think that the seamless front end is far more valuable than anything an additional centre could provide - of course with the caveats from my earlier post where they may in some rare circumstances be a reason for it although throwing in another centre speaker probably wouldn't be my first suggestion in any case. :)
     
  13. Nic Rhodes

    Nic Rhodes
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    I have tried an above and below system before but it didn't work out then. Genelec have got back to me with what I need to do so will will 'have a go'. My reservations are the same as eviljohn2 ones but like Liam I have always wanted to give it a go!! Probably just for the sheer hell of it, but if any speaker was going to work it was going to be the Genelecs here.

    Out of interest when I tried speakers above and below my fixed (non perforated projection screen), it didn't work out too well but I did prefer the just speaker above the screen rather than the one below when run individually (I now have it below just for convenience by the way, have you seen the weight of 208s let alone 1037s!!!). It worked really well in my 'A shaped' cinema room (barn).

    Calibration etc is always taken as read. Re a research job, guess the day job? :D

    Listening area is one seat ;) Mine :)

    Re dip switches etc, I am a long term Genelec user and pretty clued on on them (and room interactions etc), just didn't want to get too technical at this stage. Recently added 4 1037s and 1032 to my 2 1037s and 208.

    1038BC well a lovely dream, I think it might stay at that for the time being.....I wish......very hard.....very often as I drool over the Genelec brochure in bed.

    Excellent thoughts guys MUCH appreciated.

    Edit:

    Even though Genelec say it can be done they think a single 1037 will still be best.
     
    Last edited: Feb 12, 2009
  14. BlueWizard

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    Just throwing in my two cents.

    Horizontal placement of speakers, whether a common stereo speaker or a midrange speaker, is a less that stellar idea. When speakers are placed in a horizontal array, there will be a dip in the frequency response at the crossover points for various reason.

    Ideally, the center speaker should be the exact same speaker as the left and right, and in the exact same orientation. In other words vertical.

    But, for most people a vertical center is difficult to achieve; most simply don't have room. So, we compromise and place the center on its side. Everything we do in life is a compromise, and this is just one more practical consideration that is forced on us by circumstances.

    As to the lobing effect, that is based on the distance between the speakers, and probably to some extent, the distance from the listener. So, place the two centers side by side, in a vertical orientation, with the tweeters as close together as possible. That will give you the best possible results from these two speakers.

    If you do choose to place them horizontally, then again, place the tweeters in the center as close as possible.

    If the distance between the tweeters, midranges, and woofers represents a frequency higher than the speaker usable range, then you have nothing to worry about. For example, if the frequency wavelength represented by the distance between the midranges is above or below the operating range of the midranges itself, then you are probably OK. If not, then you just have to live with it.

    For what it's worth.

    Steve/bluewizard
     
  15. Nic Rhodes

    Nic Rhodes
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    and in practice :D It has taken a while but I am getting there thanks to Elliot and PJ HiFi who showed me the way.
     
    Last edited: Feb 12, 2009
  16. Member 96948

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    To be honest, I don't see that it would be much of a benefit, but it's the only configuration I can think of that would produce little no destructive interference in the off axis horizontal plane. It would in effect just be a double height 1037. By comparison, I can't think of a satisfactory way of positioning them horizontally.

    I suppose there might be some headroom gains in using double the number of drivers on the channel that is oft quoted as carrying the 'heaviest load', but with speakers of this stature, I'm pretty damn sure that's a non issue anyway.

    Nic, apart from the 'urge' to utilise the dual balanced outs on the Di8a, why aren't you considering just running 6.1?

    Russell
     
    Last edited: Feb 12, 2009
  17. dj-dulux

    dj-dulux
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    Calibration engineer! I thought you were a Genelec breeder judging by the number you have!

    Sounds good, I see many in both pro and domestic use which are all set to off and it drives me mad!!!!!

    We can all dream, maybe my next demo rooms....... I only have 6020 and 206s at the mo….

    Agreed, are you speaking to Finland on this?


    Dupe...
     
  18. Steve.EX

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    Nic. (Hi)

    I used to use 2 centers. My reasons were that at that time i was using extremely large main pair. I used one above and one below the screen. This greatly improved the very obvious perception of transition between a huge baffle area and a much smaller one. Tonally matched drivers are one thing, but you cannot imo escape the realisation of the small/big speaker. Whilst i am sure there are numerous reasons for not doing it, in that particular set-up the gains were to obvious to ignore.

    Hope all is well with you and yours.

    Steven
     
  19. Nic Rhodes

    Nic Rhodes
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    It is one of the options Russel but the sixth speaker is not in a very convenient position, sitting on a record rack unless I mount it high on a wall!

    Hi steven, long time mate! Good info to think about! Nice to hear from you. What are you using nowdays?

    dj-dulux. :shocked: don't they use the dips? Re Finland, yes in contact, very helpful as ever Genelec, as has been Steve in this country in the past. One of the reasons I am a fan of their kit and it;s awesome performance of course.

    Felt it might make an interesting test (and discussion point) as I was trying something 'diffeent'.

    Did I mention I have been using these as my rears for years ;)

    Kef Reference 4.2s!!

    to be replaced by the 1037s
     
    Last edited: Feb 12, 2009
  20. Bald Monkey

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    :thumbsup: Indeed :D

    I hope you keep us updated with your progress... and even the stuff that isn't :D

    I'd try the above and below technique first, unfortunately with my lounge install my PJ screen is higher than I'd like it and my center is to far below, and it is one of them little niggles. Reading about the gains others have heard from changing from below to above it's something I'd personally want to try, but above and below must be the best of both worlds.. :D if you can get it to work I'm thinking this may offer more benefits to your set-up than a wider side by side solution??? How wide is your screen Nic?

    Oh and BTW :devil:

    [​IMG]

    :devil:
     
  21. eviljohn2

    eviljohn2
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    I know I mentioned it before but I just want to reiterate - if you're doing above and below (or anything where the distances may be quite different) please be careful with delay between them.

    From what I can gather so far, everyone's said that it's quite possible to use 2 speakers and there may be reasons to do so but in general it would be preferable not to bother. :)
     
  22. Nic Rhodes

    Nic Rhodes
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    always liked a challenge :devil:
     
  23. cribeiro

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    :rotfl::rotfl::rotfl:
    Bring them on!
     
  24. Nic Rhodes

    Nic Rhodes
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    tbh I am more worried about a 1037 above the screen falling, or even getting it there in the first place. These buggers are big and heavy!!
     
  25. eviljohn2

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    The official Genelec wall mount uses the M10 holes in the side of the unit to keep it steady along with a cradle to take the weight. Obviously that won't help if your wall/ceiling isn't up to the job. :)
     
  26. Nic Rhodes

    Nic Rhodes
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    for the initial testing I will have to forgo the wall mount, so it makes it an interesting prospect how to lift and support those 37Kg! Did look at some 1037 official stands however the only one I found was almosy £700 per speaker!
     
  27. Nic Rhodes

    Nic Rhodes
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    well just about killed myself today just for you forum members. 1037 all in place and I am running with a single centre below the screen. Do you know how much pain it takes to get 37Kg of baby 1037 10' up in the air?

    Efficiency of 1037s is less than the 208 and I will tweak much more in the future, but still have much work to do re moving stuff around to their final locations.

    Initial results are very positive but boy are these big. 1037s on Kef Ref 4.2 as 'stands' are one hell of a rear speaker ;)
     
  28. jon1

    jon1
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    NIC
    true to your sig:D


    jon
     

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