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Bi-Polar vs. non bi-polar speakers

Discussion in 'Archived Threads 2001-2004' started by James_C, Sep 5, 2001.

  1. James_C

    James_C Agent

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    I am a "newbie" and I am looking into buying the Definitive Technology Pro cinema 100 speaker system for my home. When I went to talk to the salesman he asked me if I would rather have Bi-polar or regular speakers for my rear surround. I know what they are but which ones do I buy??? They seem to be the same price either way.
    Thank you!!
     
  2. James_C

    James_C Agent

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    Anyone??
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    The safest thing is to go with mono-pole (normal) speakers.
    Bipoles need to be pulled into the room a few feet so that the back-fire sound gets reflected and hits your ears after a delay. This can fool your ears into believing that the sound source is several feet farther back. For rear-sounds, this is can be a good thing.
    But you need 2-3 feet of space behind the bipole speakers, and the reflecting surface should be smooth, un-broken and symetric on the left and right sides.
    I have bipolar towers in the fronts, but my back wall is right behind my couch, and is broken up by a bay window and a brick fireplace. So I have mono-pole speakers on stands to the sides.
     
  4. John Gates

    John Gates Second Unit

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    I have heard both, and for HT, I like both. I personally prefer direct radiating speakers, however, because I feel they reproduce music more accurately than bi-poles. Personal preference, and since I listen to a lot of music, I wanted my HT to be able to pull double-duty.
    Enjoy the Def Techs!
    John
    ------------------
    System:
    Onkyo 787
    Mains: nOrh SM 6.9
    Center: nOrh marble 4.0
    Surrounds: nOrh wood 4.0
    Rear Center: nOrh prism 4.1
    Subwoofers: 2 x SVS 20-39 CS w/Fidek Amp
     
  5. Bob_A

    Bob_A Supporting Actor

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    Ideally you would want the exact same speakers for front and rear. Still, all Def Tech speakers have similar voicing so you should get good results with virtually any of them. And DT has some wall mountable bipolars (bpx series) which of course don't need space behind them.
     
  6. Ricky c

    Ricky c Stunt Coordinator

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    I have The procinema 100's as mains and surrounds and this setup is great.
     
  7. Kevin C Brown

    Kevin C Brown Producer

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    I have personally found that placement for good sound for bipolar speakers is *less* critical than for direct radiators. I have had good luck putting bipolars anywhere from 6" to 24" or more from the back wall. However, for direct radiators, you usually have to go *at least* 18 inches.
    Bipolars are specifally designed to use the back wall for reflections, and precisely because of that, the distance is less critical. Direct radiators on the other hand, are specifically designed to *not* have the reflections from the back (or any) wall take *any* role in the sound field. That's why they typically have to be placed farther out into the room to avoid any appreciable contribution of these reflections to the overall soundstage. And in fact, for typical direct radiators, 3 feet is generally recommended. (This is why stereo and HT mags typically use 3 ft.)
    The other main difference between the two, in my opinion, is that you get better pinpoint imaging from direct radiators, but the sweet spot is really small. I believe that bipolars sound better *throughout* a room than direct radiators. This is important to some people, less important to others. Another advantage to bipolars, is that you get a "wall of sound." The sound is "fatter" and more robust in my opinion. (Hard to explain.)
    Also, I am a musician. And in general, I prefer the sound of bipolars because they better reflect (!) the live sound you'd get in a concert hall. (A good concert hall!) With direct radiators, you hear the speakers. With bipolars, you hear the room and the environment *in addition* to the speakers. Maybe not necessarily what the artist or producer (or director!) intended, but my preference nonetheless.
    Bottom line? You have to try and hear the differences for yourself and decide.
    I've had (Def Tech) bipolars for going on 10 years now (a couple of different models). A few years ago, just to be safe, I picked up a very nice pair of Paradigm direct radiators. Listened to them for a night, and then switched back.
    ------------------
     
  8. Bob_A

    Bob_A Supporting Actor

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    Kevin, I agree with you about bipolars...I think with proper setup bipolars are just as nice with music as with movies (well at least I think my 2000TL's are!). There is great depth and width to the soundstage. Also there is extra power handling with the extra drivers (the speakers can go real loud w/o distorting).
     
  9. Lou Balch

    Lou Balch Auditioning

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    If you're using your system primarily for music, I would use monopoles. If your primary use is HT, I prefer di/bipole speakers. Here's why:
    1) In the theatrical presentation, which is what we're trying to duplicate, the surround field is created by an array of speakers along the sides (and back) of the auditorium. If you were seated in the "sweet spot" in the middle of the theater, the multiple monopole surround speakers will produce much more of diffused than a direct soundfield, which is the intent of the sound designer. They want to add to the experience on the screen not distract you from it. Since it isn't practical to use an array of multiple monopole speakers for surrounds at home, a single set of di/bipole speakers works best in reproducing that diffused soundfield that we heard in the theater.
    2) 3 out of 4 movies available today are encoded using Dolby Surround (over 12,000). Less than 4,000 titles are presented in Dolby Digital 5.1 (or higher), meaning 75% of the surround information available today is monoaural and bandwidth limited (100 to 7000Hz). This material is best served using speakers that provide a diffused soundfield, like di/bipolars.
    3) Even if you only bought 5.1 titles, 80% or more of the surround information in these titles is ambient information (crickets, wind, waves, streetnoise, etc.), only occasionally are the surrounds called upon to provide direct, discrete information, which brings us back to creating a diffused rather than direct soundfield. And what works best to create a diffused soundfield -- di/bipoles!
     
  10. James_C

    James_C Agent

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    The bipoles that would be included with this system are wall mounted. How far should they be mounted away from the back wall??
     
  11. Mario_C

    Mario_C Stunt Coordinator

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    I have tried both and I prefer direct radiating speakers.
    They just sound better and two properly set direct radiating speakers can produce a phantom back center channel.
    ------------------
    My Music & Home Theater System
     
  12. Mario_C

    Mario_C Stunt Coordinator

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    The following comes from The Audio Perfectionist Journal
    Dipole Surround Speakers
    If re-radiated room sound is a delayed,
    out-of-phase distortion of the original signal, does
    it make any sense to use dipole surround speakers
    positioned so that the listener sits in the null area
    insuring that all he hears is reflected sound off the
    room boundaries? This idea comes from the
    ridiculous assumption that we should be trying to
    duplicate the mediocre sound of the local commercial
    cinema instead of striving for the highest
    fidelity possible in the home.
    In a commercial movie theater there are
    arrays of surround speakers at each side of the
    auditorium to provide a diffuse sound field. This
    isn’t done because diffuse sound is somehow
    desirable. It is done in order to provide a similar
    (albeit mediocre) experience for those seated in
    less desirable positions relative to the speakers.
    Movie theater sound is always adjusted to the
    lowest common denominator. Why would you
    want diffuse, unfocused sound in the rear of your
    room at home? Wouldn’t it be better to have clear,
    precise sound at the rear that matches the sound at
    the front of the room?
    Don’t use THX-style dipole surround
    speakers if you want the best possible sound. It’s
    just that simple.
    Dipolar speakers
    A dipole speaker has a figure-of-eight dispersion
    pattern with the rear wave out of phase
    with the front wave. Little energy is radiated
    directly to the sides. Full-range planar speakers
    are usually true dipoles.
    Full-range speakers with real dipolar radiation patterns, like planar-magnetic, ribbon and
    electrostatic designs (not hybrids), are especially
    critical of position relative to the front wall. The
    rear wave from these speakers will reflect directly
    back from the wall and interact with the speaker
    causing a greater sonic effect than what you’d get
    with conventional designs. Moving the speakers
    closer to or farther away from the wall can have a
    profound effect on the midbass and lower
    midrange frequencies as well as bass and you’ll
    have to devote more time to experimentation.
    True dipoles radiate little energy directly
    to the sides but tonal balance is very different on-and
    off-axis, so the wall directly to the side of the
    speaker is of less concern, but the first side-wall
    reflection coming off the wall forward of the
    speaker position becomes more critical.
    Dynamic speakers with open-back
    midrange drivers can’t be treated like real dipolar
    radiators. They have a quasi-dipolar radiation pattern
    in the midrange (depending on cabinet struc-ture)
    and remain point source radiators in the bass
    and treble. They simply splash more midrange
    energy off the front wall behind the speakers and
    behave more like bipolar designs in this regard.
    Less midrange energy is radiated directly to the
    sides of each speaker but the bass and treble portions
    of the spectrum are strongly radiated to the
    sides, so side wall reflections will have a very different
    tonal signature than the direct sound from
    the speakers.
    Some speaker designs use open-back
    midrange drivers and a second tweeter aimed to
    the rear and wired out of phase with the forward-directed
    tweeter. This type combines all the worst
    characteristics of dipole and bipole designs. Try to
    absorb everything but the direct radiation from the
    front for the best results.
    Dynamic speakers with open-back
    midrange drivers are often touted as being less
    room-sensitive than other types but in my experience
    just the opposite is true. Lots of sound-absorbing
    material on the walls is called for. After
    you absorb all that rear-directed energy and hear
    how much better things sound, you may wonder
    why you bought a speaker that created that energy
    in the first place.
    Bipolar speakers
    A speaker with a bipolar radiation pattern
    directs sound forward and rearward with both
    waves in phase as they leave the speaker. A bipole
    is like two conventional speakers placed back-to-back
    and has very broad dispersion.
    Dr. Bose has demonstrated that many
    undiscerning listeners like the sound of artificial
    ambience as provided by speakers that purposely
    direct lots of energy towards the walls. This conclusion
    was confirmed by those infamous listen-ing
    tests done at the NRC in Canada. Be that as it
    may, this is, in my opinion, the antithesis of what
    is desirable for high-fidelity reproduction.
    Speakers with a bipolar radiation pattern
    direct at least half the acoustic energy to the room
    boundaries where it will be reflected back to the
    listener from all angles with varying time delay.
    This added “ambience” smears definition and
    detail. An artificial sense of spaciousness is created
    at the expense of a focused, dimensional image
    and any real resolution.
    Here is my advice: If you don’t own bipolar-
    radiating speakers, don’t buy them. If you
    already have, try to soak up as much of the rear-and
    side-directed energy as possible with absorptive
    room treatment. Positioning the speakers even
    farther from the room boundaries helps.
    In my experience, bipoles work better than
    dipoles because bipoles have similar tonal balance
    on- and off-axis. At least the reflections mimic the
    tonal balance of the direct sound with bipoles,
    which is not the case with dipoles. In general,
    dipoles image better and bipoles have better in-room
    tonal balance. Neither type offers completely
    satisfying performance in my opinion.
    If you want to read more go to http://www.audioperfectionist.com you can download issues 1 and 2 for free. This should help you make your decision.
    ------------------
    My Music & Home Theater System
     
  13. Marc H

    Marc H Second Unit

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  14. GordonL

    GordonL Supporting Actor

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  15. Mario_C

    Mario_C Stunt Coordinator

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  16. Timmy

    Timmy Stunt Coordinator

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    I went from in-ceiling speakers to bipoles. WOW; the bipoles (in my specific setup) increased the ambience greatly. Front to rear pans sound seemless.
    Rear surrounds are not supposed to be so directional. Well... unless you listen to music alot.
    You need to decide which format you will most likely be playing the most and pick your surrounds accordingly. Since my HT is mainly for movies, I went with the bipoles.
    Here is a look see:
    hometheater.home.att.net/speakers.htm
     
  17. Bob McElfresh

    Bob McElfresh Producer

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    This issue seems to divide along the same lines as MUSIC vs HT systems.
    A salesman once told me:
    "Music speakers are about accuracy, but HT speakers are about impact!"
    The quote from the Audio Perfectionist Journal makes sense from a Music perspective: bouncing sound off of a wall is NOT accurate, therefor speakers that do this are no good.
    But Movies are full of artifical sounds. Ever fire a real handgun? Does it sound anything like the shots from Terminator 2 or The Matrix? Of course not. (Dont even get me started on outer-space battles [​IMG])
    But bipolar speakers ENHANCE the movie experience by giving you an artifical sense of space:
    One week I had everything pulled out of my living room while we had wall paper removed and new texture/paint put up.
    I kept all furniture out and moved just the HT equipment back in. My bipolar towers were pulled into the room about 1/3 of the way, everything in a circle around the chair, SPL adjusted, laser-pointer alignment, etc. (Hey, this IS my hobby [​IMG] ).
    Movies sounded great. But what shocked me was the sound when I played U.S. Marshals. In this movie there are 2 scenes that toggle between a cell phone outdoors in the swamp, and a stuffy office. As the scene toggled, I had the sensation of my walls blowing away, and then collapsing back in. I expected my ears to pop! It was almost un-pleasant as the speakers gave me a LARGE space, then a SMALL space sense of sound.
    (Sad part of the story; my SO wanted to use the living room for ... living, so I only had a day or two to play before putting stuff back. Sigh)
    James: This was with bipolar FRONT speakers, not rears. There is a LOT more signal on the front speakers to work with.
    Although I have just defended bipolar speakers, my advice is still to go with direct-radiators/regular speakers for the rears. They ARE dependent on smooth, un-broken rear & side walls, and they DO want 2-3 feet of space around them to have good effect.
    Good Luck.
     
  18. Mario_C

    Mario_C Stunt Coordinator

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    You know when I changed my speakers to direct radiating speakers ( I was using Mirage Om-7's fronts and OM-R2 Rears) I was amazed by all the detail In the movies that I had never heard before. I have to agree with Richard Hardesty that bi-polar speakers muddy the detail. My speakers have excellent imaging (Mirage HDT-F) and the sound envelops my room. The other thing I mentioned was the phantom back center channel. You can never reproduce this with a Bi-polar speaker. I can hear sounds comming right from behind. Somentimes I have to look back to remind myself that I don't really have a speaker back there. Of course to each his own. Use what you like.
     
  19. Bob_A

    Bob_A Supporting Actor

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    quote: I have to agree with Richard Hardesty that bi-polar speakers muddy the detail[/quote]
    I think amp choice and setup is particularly important with bipolars/dipolars. Martin Logans are dipolars...have you ever heard anyone complain about muddiness or lack of detail with them? I have never had any muddiness or lack of detail with my DT's. They are very detailed, clear, and crisp. They also image very well, and the soundstage (and sweetspot) is huge.
    [Edited last by Bob_A on September 06, 2001 at 07:54 PM]
     
  20. Kevin C Brown

    Kevin C Brown Producer

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