Bi-Polar vs. non bi-polar speakers (1 Viewer)

[James_C]

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!!

 

[James_C]

Anyone??

 

[Bob McElfresh]

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.

 

[John Gates]

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
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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

 

[Bob_A]

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.

 

[Ricky c]

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

 

[Kevin C Brown]

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.
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[Bob_A]

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).

 

[Lou Balch]

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!

 

[James_C]

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

 

[Mario_C]

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.
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[Mario_C]

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.
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[Marc H]

I have heard both types alot. Same speaker front and rear is the way to go in my humble opinion.
Also,
Check the FAQ at Dolby's website too (points 15 and 16): http://www.dolby.com/tech/co.br.0103.DDFAQ.html#q16

 

[GordonL]

Neither type offers completely satisfying performance in my opinion.

This guys rantings is just that - an opinion. And in the context of the article, it's a personal preference. I wouldn't make my decision based on one man's opinion, I would make it based on personal preference, as should you.
Back in the days of Dolby Pro-Logic, it was desireable to use di-poles in the rear (sides) to create a more diffuse, enveloping surround sound. Movie soundtracks were mixed that way, there were no directional effects. Nowadays, with Dolby Digital, we are seeing movies with intentional directional surround effects which makes mono-poles more desireable. So, if you used di-poles with DD, you wouldn't get the desired directional effects, but if you used mono-poles with DPL, you wouldn't get the diffuse enveloping sound. It seems that bi-poles gives you the best of both worlds. And, given that the number of DPL source material still outnumber DD by a wide margin, it makes more sense to go that route. But, that's just my opinion...

 

[Mario_C]

This guys rantings is just that - an opinion. And in the context of the article, it's a personal preference. I wouldn't make my decision based on one man's opinion, I would make it based on personal preference, as should you.

The why come to this forum asking for peoples opinions? You take all the information you can find, demo the equipment and make a decision. Right?

 

[Timmy]

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:
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[Bob McElfresh]

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 )
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 ).
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.

 

[Mario_C]

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.

 

[Bob_A]

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]

 

[Kevin C Brown]

The other thing I mentioned was the phantom back center channel. You can never reproduce this with a Bi-polar speaker.

"Never" is too strong a word here!
I have a Sony TA-E9000ES pre/pro. Last software upgrade included support for a Virtual 6.1 soundfield, using a 5.1 setup. Me with my bipolars front and back. I certainly *did* get the phantom rear center channel in the back.
I liked the phantom channel so much, that I added a separate Dolby Pro Logic processor to get a real rear center channel.
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