Dipoles, bipoles, or monopoles for surround speakers?

We recommend using dipoles for surrounds for the reasons you mention. They have nothing to do with Dolby Surround--that's just an encoding method for the content. The purpose of dipoles is to reproduce the diffuse ambient sound that one gets in a movie theater with multiple speakers playing the same content (and thus sounding diffuse).

Bipoles are not recommended because they don't really achieve the diffuse sound needed. I guess they are a compromise between dipoles and direct radiators. Yes, some surround music content was mixed with direct radiators as surrounds, but since that is a dead format at this point I would recommend going with dipoles.

What about placement of Dipoles, aren't they the trickiest to place?  You have to be seated exactly at the null which rules them out for multiple seating locations and rear channels?

Hey marshall check these surrounds out they are awesome speakers and work well with both movies, music and their design is extremely forgiving  for odd placements  http://axiomaudio.com/surroundspeakers.html

I'm sure they are nice speakers, but that doesn't really answer any of the questions posed.

 Dipoless are the easiest to place. If there is one row of seating the center of the dipole should be parallel to that row. If there are two rows, it should be between the two, approximately 2/3 back from the first row. Dipoles can either be ceiling mounted or wall mounted. Wall mounted is generally preferred and the dipole should be at approximately the listener's ear height or sometimes slightly higher. In these cases we do want the reflective surfaces near the speakers as this reinforces this channel, and it is not designed to have much in the way of clarity. It is really designed for effects. Does this help? Quoted from here http://www.audioholics.com/tweaks/speaker-setup-guidelines/loudspeaker-placement-guide

Yes, except the part about them being "easiest to place".  Having the rules for their placement so precisely dictated seems to fly in the face of  "easy" unless you have a rectangular room with no obstructions on the wall.  Directs, on the other hand, I've has success with placing everywhere from the floor to the ceiling.  Are some locations better than others?  Sure, but with a less than ideal placement, in-phase monopoles are easier to calculate the behavior of.

Don't get me wrong, I think dipoles are great properly placed, but for a lot of people without dedicated home theaters (don't know if this includes the original poster or not), I think that placing directs will be more forgiving.

Also, and once again I think Axiom speakers are quite nice, there method of simply filling the entire room with sound with a quad pole design is quite the in-exact science and would seems to remove all trace of directionality in the side channels.  Maybe that what some people like, but I'd rather preserve directional cues, even if they are beside/behind me.  I've never understood why we would strive to preserve directionality of our fronts, and try to accomplish the exact opposite with the sides and rears.

I am, however, open to enlightenment.

oh I get exactly what you are saying,  but thats why I went with the quads because of my living room. One thing I have learned from this hobby is try A/B comparisons of both dipoles and directs in your house. They both have their pros and cons. In my own home depending on my furniture arrangement dipoles mostly worked best, but their were times when direct worked better, but that also depended greatly on the speakers themselves. I found better made dipole speakers tended to handle both multi-channel movie's and music quite well. This article has a great face-off of both dipoles and directs http://www.hometheatermag.com/bootcamp/25/index.html

Chris - I know you meant surround music formats like SACD using the ITU speaker layout in your reference.  But, not so fast in declaring it dead.  Unlike DVD-A, SACD is still alive and kicking while delivering the best reproduction of live classical music on the planet.  New releases keep coming.

Incidentally, I use 7 Martin Logan electrostat hybrids, which are dipolar above the bass frequencies.  I do not sit in the null, however.  The fronts of all of them point directly at the sweet spot.  The sound is the most lifelike I have heard anywhere.  Audyssey has a tremendous amount to do with that.

Hi Carl,

Yes, I was exaggerating a bit...  Believe me, I wish multichannel music was really "here".  It's been trying for 10+ years, but has unfortunately not made it big.

I like to use both dipole and monopole surrounds. We can hear stereo imaging behind us but not panned from front to rear. With dipoles a small bird in the front sounds like a huge dragon when panned to the rear but if  you have a pair of monopoles in back and a separate amp and preamp powering a pair of dipoles to the side and one to the rear it seems to give the best blend of envelopment and directional ques and allows for adjustment according to personal taste. what do you think of bipolar speakers being used for the height channels in audessy DSX or in dolby prologic IIz?

Chris,

Do you recommend dipoles for all the surround speakers (sides and back)?

Craig - I do not want to detract from anything Chris might say, and, as always, his opinions carry a lot of credibility with me.  I think to dipole or not to dipole depends on a lot of things.  Number one would be for what sources do you want to optimize?  I think there is a good case to be made for the more diffuse dipole surrounds aimed front/rear with movies.  Dipoles would not appear to be the best choice for the main speakers, unless they are planar dipoles.  But, I am interested in Chris's thoughts.  What do the movie mastering/mixing engineers  typically do in their control rooms?  Whatever that is is what would be optimal for home theater, in my view.

For primarity SACD music listeners like me, the ITU standard used for most SACD's specifically discourages dipoles. And, that's the way Mch music recordings, classical ones at least, are typically monitored in the control room. with all direct radiators.

Having said all that, I use 7 Martin Logan electrostat hybrids, which are dipolar from the mids on up.  But, I do not face the surrounds front/rear, as in a typical home theater layout.  The fronts of mine all face the sweet spot - that's me sitting there.  But, I do not think I am inconsistent  with ITU, because I think they were talking about diffuse front/rear facing dipoles only.  They just did not say so.  So, you could say I get a little of both worlds with my setup.  Incidentally, it requires planar dipoles like mine to do what I do.  The typical angled box with two sets of direct radiators for home theater just will not work properly as I have described.

Be that as it may, my Audyssey Pro EQ'd sound is utterly amazing.  With music on SACD or Blu-ray, for which I have an excellent real world standard in all the live concerts I attend, it's the closest thing to a live performance I have ever heard anywhere.  No stereo, no matter how costly comes close.  And, I have heard quite a few of the very best stereos costing hundreds of $ thousands.  It also sounds really great with movies, but I  typically do not have any real world reference for most sounds in movies.  So, perhaps there is a better movie sound setup than mine.  I just would not know.

Carl summarizes the dilemma nicely: movies require diffuse surround and music requires direct.  Since the vast majority of existing surround content is movies, I think it's wise to concentrate on that.  Some, have the luxury of doing two surround setups--one for music and another for music.  Some AVRs even give you an easy way to switch between Surr A and Surr B.

Diffuse surround playback for movies can be achieved in two ways: (1) an array of direct radiators on either side playing the exact same content.  It becomes diffuse because of the array.  This is what is used in dubbing stages where movies are mixed and in theaters;  (2) a single dipole speaker per side that points its null to the listening area.  This is often the most practical way to get diffuse surround as it's difficult to put up 4-6 direct radiating speakers per side in a home listening room.

The Back Surrounds are another story.  No original movie (for theaters) had been mixed for 7.1 until earlier this summer.  Toy Story 3 was the first to take advantage of the new Dolby discrete 7.1 format.  So, to my knowledge there is no standard on whether the Back Surrounds should be diffuse or not.  

Don't be fooled by the numerous so-called 7.1 Bluray discs out there.  These were not mixed for 7.1 theatrical release.  Instead, they are re-mixed (most often not by the original mixers) for 7.1 by using some sort of matrix encoding method to artificially derive the Back Surround content.

Thanks Carl and Chris.   I have been using bipole for my sides and direct for my backs.   I have been toying with going dipole, but my speaker manufacturer does not make their own dipole.    Would you recomment switching to a different brand for the sides?  I can't justify buying all new speakers yet. 

Thanks again.

By the way I just moved up to a Onkyo 1007 from an 805.   I love the improvement that Dynamic EQ has brought.   My room is probably too narrow to accomodate the wides (11.5' l x 25' w).

Craig - I have zero experience with bipoles.  I have not heard of a bipole-only speaker since the old, old Mirages.  Most surrounds that are bipole have a switch to choose either bipole or dipole operation.  But, it seems yours do not.  I would hate to suggest going inside the speakers to reverse polarity to one set of drivers, because that might also affect the designed-in tonal balance or other parameters of the speakers.  Maybe the manufacturer could advise you on this.  If he says it's OK, then it should not be too hard to include a polarity reversal switch on a DIY basis as long as you are inside, anyway.

Failing that, you might see if you can get a dealer to lend you some dipoles to see if you like them before buying.

I really have not heard of bipoles having a major role in multichannel.  I am led to believe they are less diffuse sounding than dipoles.  Unlike planar dipoles, box biploes would usually be hard to aim one side at the sweet spot, but you might also try that if you can. 

Also understand that there are some dissenters in the industry against dipole surrounds.  Gary Reber at Widescreen Review magazine consistently rails against the "fuzzy wuzzy" sound of dipole surrounds or of THX and prefers direct radiators. There are many like-minded in the industry.  But, the key question is what sounds best to you on a wide variety of program material that you actually listen to.

Good day to all and Happy New Year!

I am presently in the process of an almost total rearrangement of my (dedicated) Home Theater space, which is 9m (29.5ft) L x 5m (16.4ft) W x 2.7m (8.9ft) H, mainly because there is a newer AV pro (Onkyo PR-SC5507), some more sources (BD and HD-DVD players) and a newer HD projector. As you know, the Onkyo sports the Audyssey Multi EQ XT as a room correction and speaker set-up system.

The system speakers are:

- 2 x Mirage M3-si (floor standing-bipolar) Front L-R main

- 2 x Mirage MC-si (bookself-same series as main L-R)) Front Center (powered by two separate power amps, driven in parallel by Onkyo's Front Center Output with a Y-connector)

- 2 x Mirage M5-si (floorstanding-bipolar) Surround L-R

- 2 x Mirage OM-C2 (bookself-omnipolar) Front Height L-R

- 2 x Paradigm ADP-190 (bookself-dipole) Back (or Rear) Surround L-R

The Main Front L-R are placed on the floor, at the sides of the screen, facing the sweet spot.

The Front Center speakers are placed on the rack, in front of the screen, horizontally side-by-side. I've chosen this 2-speaker configuration for front center, to expand the sound field and cover the gap between the two main L-R speakers better.

I intend to place the two Front Height speakers at the upper L-R corners of the screen and slightly wider than screen width, hung from the ceiling and with a slight inclination towards the "sweet spot".

The Surround L-R speakers are placed on the floor, behind the sweet spot, facing it, at a distance almost equal to that of the Front L-R ones.

There are two rows of seats, one with three and one with two seats. The front one is a three-seat couch, the center of which I consider as the "sweet spot", and the rear is a two-seat couch. The (main) surround speakers are placed just behind the rear coach and at an angle of about 30-40 degrees, firing towards the "sweet spot". In fact, there is no space (especially at left side) to put them at the sides, this is why I have chosen that position. Their distance from the rear couch is about 4-5 feet and about 6-7 feet fromthe "sweet spot".

I intend to place the dipoles behind the seet spot, hung from the ceiling, in the center of the room, with a distance between each other of about 1-1.2m (3 to 4 ft). The placement shall be in parallel with the back wall of the room, and at about 1.5 to 2 ft down from the ceiling, with the speaker back, facing the back wall of the room, just behind the two couches, at a distance of about 8-10 feet from the rear couch. As we all know, the design of this kind of speakers, as most of the dipoles, has its drivers in two side levels, slightly inlined 30 to 45 degrees to the vertical level, facing oposite. Therefore, their drivers will "fire" nor directly to the seats, neither directly to the side walls, but at an angle (left and right), facing forward and at the sides.

My question is if this kind of placement of the rear (back) surrounds will work or not.

I would appreciate your opinion. Thanks in advance.

Χρονια Πολλα και Καλη Χρονια Παναγιωτη,

The rest will be in English :-).  First, it is a big, big problem to use two speakers for a Center channel.  You will have terrible problems with the dialog and other sound in the center because both speakers are playing the same thing.  This leads to something called "comb filtering" that causes voices to sound like they are in the bathroom... Very bad idea.  The placement of the Back Surrounds as you suggest is fine.

Χρόνια Πολλά, και Καλή Χρονιά επίσης, Χρήστο!

Inevitably, the rest is in English, too.

Thank you for verifying my thoughts regarding the placement and use of the dipole speakers, as back (rear) surrounds. To tell you the truth, this has been and still is my main concern, mainly because these two speakers are from different manufacturer than every other speaker in my HT room (both are Canadian makers, though).

Let's have a little discussion about the two center speakers and the comb filtering effect. First of all, let me state that I value your opinion and I take it very-very seriously. But I need to clarify my initial idea about using two center speakers, the way I have made it in my mind.

As I already wrote, the main Front L-R speakers are two floorstanding "giants", measuring 134 x 46 x 24 cm and 61 kg, requiring 100-300 WRMS of amplifier power to be driven. These two speakers will be driven by two NAD S200 power amplifiers in bridged mode, acting as monoblocks. The distance between them is about 3.4 to 4 metres and the same for each one from the so-called "sweet spot" is almost the same. It means that these three points form an equilateral triangle.

Between the two main speakers, three racks are laid on the floor in line, carrying all the HT devices. The center speakers shall be placed on the top surface of the center rack, just under the center of the screen and in front of it. The height of the rack is 77 cm, meaning that it has almost the same height with the head(s) of the person(s) seating at the front couch. This means that the center speaker (or speakers)  will be "firing" almost directly to the face of the front seaters.

The MC-si speaker is a small bookself speaker, but perfectly matching with the main L-R speakers, because it's from the same series and made exactly for this purpose. However, due to its size, it has its own limitations: smaller amplifier power handling, lesser SPL and much more limited frequency range. Therefore, because of its size and limitations, my thinking is that it may still not be able to bridge the "sound gap" between the two main speakers.

As we all know, the ideal solution for the center is always a third speaker, identical to the two L-R mains. But, in 99% of the cases, this is impossible. This is why the speaker manufacturers are making smaller, horizontal speakers, to match the mains, mainly in timbre and perhaps in other parameters. In my case, I came up with a simple thought: two identical speakers, placed on the same rack, side-by side, driven by two identical power amplifiers and by the same AV pro signal. It seems to me like having one larger (or longer, if you prefer) speaker, not in one but in two cabinets, with double SPL capacity and power handling.

As far as I know, the comb filtering effect happens when two (sound) signals arriving at the same location at different times. Because of the differences in the arrival times, the sound waves will have additions when they perfectly overlap and reinforce each other, and also have cancellations or nulls where they cancel each other out (the latter is called destructive interference). This occurs in virtually all speaker systems whose musical ranges overlap, where both drivers are reproducing the same sounds, as in stereo or surround sound, and because of multiple drivers with different physical locations used to cover the same frequency range. But, as I understand it, this happens when the two signal are "geografically" oposite (or almost oposite) or when the sound sources (speakers) are quite distant and the sound waves have at least a significant angle between each other. In this case, certainly, there can be cancellations, nulls or reinforcements, especially when the sound sources transmit sound waves with time difference.

In my case, this cannot normally happen. The two speakers shall reproduce exactly the same sound wave, at exactly the same time and exactly the same level and the waves shall be parallel, not meeting each other under any circumstances. Its like having a large speaker doing the same job like its smaller brother, but louder and wider.

Am I right or not? I would appreciate your opinion. Thanks and XRONIA POLLA!

P.S.:

I will try to attach a file in PDF here. It contains pictures and specs of the Mirage M-si series floorstanders, which includes the M3-si and at the end of it are the MC-si specs. Pictures are included.

-

Actually, that's not the case. Comb filtering happens any time you have the same signal coming from two speakers.  The closer they are, the more you will hear the effect.  In voices it will sound like a hollow cave sound.  This does not happen in a single speaker with multiple drivers because of the crossover networks that limit the range of each driver and make sure there is proper overlap.  If you just want to double the SPL then that's fine, but I think you will be disappointed after listening for a while.  The single speaker you have selected should more than adequately handle the required SPL.

Thanks, Chris, for your reply. Your advice is higly appreciated. But before having my system finally set up, I will try to experiment for a while to see what happens. I promise to publish the results of the experiment at the end.