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Bipole or not

Discussion in 'AV Receivers & Amplifiers' started by guyb, May 20, 2001.

  1. guyb

    guyb
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    Dolby/THX suggest using bipole speakers for the surrounds however DTS suggest using normal speakers for the surrounds. What are everyone opinions on this. I was going to buy bipole surrounds to use with the 3801 but since it is based around DTS decoders do you think I should for the standard speaker type.
     
  2. Guest

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    I think you will find the THX spec refers to Di-pole rather than Bi-pole.
    That said it's all a matter of taste. If you are buying a fully THX compliant set-up and enjoy? the THX processing then Di-poles are probably the way for you.
    I have found that Di-poles are very fussy about room size/position/acoustics and can either be an HC nightmare or VERY good in their mannerism's. I use two pairs of the Kef TDM 34DS THX Di-poles and for all their non-localised characteristics have ABSOLUTE authority over their surround duties and ARE an ABSOLUTE joy. That said they are not overly cheap.
    DTS on the other hand recommend mono-pole (standard or direct radiating for want of a different name) speakers.
    If you are going to buy the 3801 and want to be pedantic the 3801 will allow you to drive 2 pairs of surrounds, each of which can be independantly selected depending on program source and i think you can even set it up so it automatically selects rear A for (i.e) DD and rear B for DTS programs in the set-up menu.

    Regards

    SteveEX
     
  3. guyb

    guyb
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    Thanks for the info Steve EX. I have the my dipoles and bipoles mixed up. What is the difference. I was going to use 4 Mission m7ds Bipole surrounds http://www.mission.co.uk/m70_ser.htm#m7ds along with the matching m7c1 and a pair of m73's. Do you think these will work well with the Denon 3801 bearing in mind that the rooms is not very big or do you think I would be better off with 4 m71 loudspeakers for the surrounds http://www.mission.co.uk/m70_ser.htm#m71
     
  4. Matty N

    Matty N
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    If the room is small, I would think carefully about bipole/dipole speakers as you could end up muddling the soundfield considerably due to unwanted reflections. It may be an idea to try and borrow some to have a listen using various placements.

    Bipoles basically operate both their drivers in phase, such that when one pushes (firing sound to the left of the speaker) the other one pushes (firing sound to the right). This creates increased spatiality supposedly and makes listeners less aware of the speaker itself. This could well be personal preference.

    Dipoles on the other hand operate their opposing speakers out of phase such that when one pushes, the other pulls. When positioned at 90 degrees to the listener, this creates a null at the listening position that appears to deliver a 'wrap around' surround effect. Some like it, others don't. As such, both speakers are sensitive to placement, but the dipoles much more so. The ideal set up will have all dipole surrounds arranged at 90 degrees to the listening position::
    ________________
    :......^.....^......:
    :.......................:
    :<.[ COUCH ]..>:
    :......................:
    :......................:
    :......................:
    :.\/.{screen}.\/.:
    :________________:
    (ignore the dots!! couldn't get it to work any other way)

    Hope that helps

    Matt

    [ 20-05-2001: Message edited by: Matty N ]
     
  5. Guest

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    Bi-polar speakers have two opposing (one either side of the listening axis or sweetspot) drivers firing in phase with each other and are far more directional. Di-polar speakers are similar in appearance and design but the drivers fire out of phase and if positioned correctly (also the seating position) then they become almost invisible as a point source is and the THX "wall of sound" is produced. The main (probably) argument against Di-poles is that they herald from the Pro-logic era when a diffuse surround was the order of the day and with THX decorrelation processing applied it was IMHO THE 2nd to none Pro-logic experience.
    THX today STILL fully endorse Di-polar technologies for their digital decoding technologies and i do prefer them. There are many who DON'T like them but personally i feel that the KEF TDM and MK SS surround speakers to name 2 are some of the very best around and they are Di_pole and Tri-pole!!!!
    IF you have a small room you may well struggle with Di-poles as from my experience anyway you require at LEAST 3-4 feet either side of your side surrounds free of any obstructions i.e rear wall, chimney breast etc etc other wise reflections and the like become apparent and ruin the non-local image this then means you need a rear wall (if 2 surround backs are used) of at least 16 feet (ish), of course 1 could be used.
    Seating position is absolutely critical with no compromise. All that said it works for me but not for all.
    Hope this helps.

    Regards

    SteveEX
     
  6. MarkB

    MarkB
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    I personally use direct radiating speakers because I listen to a lot of music, esp. multichannel and although my amp (like your 3801) can make use of 2 sets of surround speakers, I am more than happy with the sound field. In any case, I personally prefer dts 6.1 ES discreet over THX Surround EX.
    It really is all a matter of personal preference.
    Mark
     
  7. pavlos

    pavlos
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    HI Steve, well can you clarify something else for me too? well I was told that the recommended height for di-polar surround speaker should be 2-3 feet above the listener's ears, well others told me that is better to put the di-polar surrounds closer to the ceiling,my question is if I put my surrounds lets say 5-6 feet above the listener's ears will that be bad?

    Thanks in advance


    pavlos

    [ 21-05-2001: Message edited by: pavlos ]
     
  8. Guest

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    MarkB
    I too have a "soft spot" for 6.1 discrete but as there are only 5 or so dvd's with this format against 3 or 4 times this quantity in the Dolby EX flavour (and the likely hood that this ratio will INCREASE) I have always tended to follow the THX ideals regarding HC. Who know's perhaps DTS (or another format?) will go from strength to strength, but i don't see it just yet! Say what you like about THX, Yes it's expensive, yes certainly there are non THX branded products that are the equal and better but i do feel that if you still too THX (ultra as it's refered to now) you are getting a good standard of performance (provided all components compliment each other) and at the end of the day THX's goal (obviously after making money) has been solely (but not of late perhaps - THX spec PC's????? but then probably this is not aimed at a a serious HCinephile) to "improve" the HC experience.

    Pavlos
    I have searched long and hard MANY times and have come to the conclusion that there is (Home THX at least) NO official guide line or white-paper released regarding exact speaker placement (and i doubt there will) Whilst eager to sell it's "exacting" equipment i suspect ther are just too many variables involved to give specifics - Room size, Room shape, Room height, Construction materials used, Fittings, Furniture etc etc etc.
    The most "common" belief is approx 3-4 feet above listening position with the surround backs being marginally lower, HOWEVER personal experimentation is the only guarantee for success there is really no "hard and fast" rule, simply guides and a little time may well reap dividends performance wise (particually where Di-poles are concerned.
    One last thought - Personally i am not too keen on the idea of placing Di-poles near the ceiling! as i have a 9 feet tall ceiling. If you look at some of the professionally installed set-ups featured in HCC i suspect you would find the heights more or less uniform to the listening position (3-4 feet) but further along the side walls (towards the front) as required when using Di-poles than perhaps you would if using a mono-pole type speaker.
    Sorry, not much help but there are no "rules"

    Regards

    SteveEX
     
  9. MarkB

    MarkB
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    SteveEX,
    Couldn't agree more but I would like to hope that more discreet stuff does hit the shelves. I'm a firm believer in the picture and sound quality over extras (unless they are on a second disc), and I hate to think that a dts 6.1 soundtrack has been left off only to accommodate 7 or 8 foreign languages, 3 trailers and an hour long "making of". Se7en R2 is a good example of a well made R2 disc, basically because it is a R2 copy of the R1 release.
    Perhaps 24bit/96kHz 6.1 discreet capability of dts may change the stance of the studios.
    Mark.
     

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