Discussion in 'Home Cinema Speakers' started by Jacob, May 23, 2005.
Can someone please explain what a bi-polar speaker is and its advantages?
From memory and limited knowledge, bi polar speakers have two cones, one in phase one out of phase. Usually, the speakers are quite flat and can be hung on the wall, fairly flush. The objective of a bi polar speaker is to create a non directional diffuse sound stage - i.e, you cannot really locate a sound, unlike direction speakers which tend to push/direct out the sound.
I used to own Mission M77ds and the produce an enormous, quality rear sound stage that fills the rear of the room...worth demoing each speaker type is it is a unique sound that some love, some hate...
Hope this helps,
Actually Captain Benefit has described a dipole speaker. A bipole speaker has a very similar mechanical design but the drivers are connected (wired) in phase. This prevents cancellation of bass signals but the sound is less diffuse (compared to a dipole).
BTW: Normal speakers are sometimes also referred to as monopoles.
Using dipole, bipole or monopole speakers is usually a question of personal preference and/or placing.
Thanks, I don't fully understand some of the jargon but as i've got a pair of Eltax mini bi-polars as rears, I was just wondering whether I was losing out by using them or whether I should go for conventional speakers (which I now know are called monpole!)
I forgot to add that if it's just personal preference as Reiner syas then i'm happy to keep using them.
Thanks for the replies
It depends on what you are listening to. Common opinion is that di/bi pole speakers are best for movies where you want to be 'surrounded' by the sound stage but mono-poles are better for multichannel music where the music is 'designed' for pin point placement of sounds. The most important thing is though, if they sound good to you then they are doing their job well.
The question here is whether you want to hear where the rear effects are coming from (bipolar) or you just want a diffuse sound (dipolar).
A well designed and properly positioned di-polar speaker will create a good sense of ambience in the room, but you will not be able to tell where it (the speaker) is positioned. One negative of this being that front to back effects, or stereo rear effects, will appear very watered down (or indeed non-existant). So, if you're after a really well-defined steering of the sound (such that you could point to that X-wing fighter as it flies around the room), then a dipolar speaker won't be for you. If you favour a predominantly front focussed sound stage with lots of non-location specific ambience in the room, then a dipolar speaker would be for you.
Bipolar speakers - such as the Mission 77ds as a very good example - were designed to try and create a compromise between the two. Just like a conventional speaker, you will have no problem locating the position of a bi-polar speaker. Therefore, you will be able to point at the X-wing as it circles the room. Where it differs from a conventional speaker is in its spread. Normal speakers are quite 'beamy' and this is no good for generating lots of reflected sound in the room. The wide spread of a bipolar speaker will generate more reflections in the room which, when the reflections arrive at your ear (delayed compared to the direct sound) will be perceived as ambience. Sometimes that ambience is going to appear to be coming direct from the speakers (which is a bad thing), but you'll still be getting the 'real' ambience (the delayed reflected sound) too - just the same as a di-pole.
In my opinion it is a shame to throw away the stereo information in the rears, so FWIW I favour a bipole speaker - of which the Mission is a splendid example. I don't really like multi-channel music.
But hopefully there's enough of a overview in there to make up your own mind as to which you would prefer.
That is a good answer. I was trying to say that!
I suppose in summary it is about whether you want to dodge bullets or not
A good idea of the difference between bi- and dipole speakers is the phase tests on any THX Optimiser as it's very easy to tell the difference between the "spaced out" sound and the centralised sound.
Of course then there are other varieties such as tripole speakers like Kef Q2DS and M&K K4's. I've also come across so-called "adaptive dipoles" such as those in the Rocket speaker line where the main drivers are in phase but the tweeters are out of phase. Apparently this is an excellent compromise between the 2 main varieties although I've not heard them myself.
Personally I'd love a pair of 77ds to go with my front Mission 77 series speakers.
Thanks all, (especially Lost Cause)
I do prefer being able to pinpoint rear surround sound so I guess my bi-polars are the correct choice.
Going even further, a lot of people suggest using bi/dipoles as the side speakers in a 7.1 system but with direct radiating (monopole) speakers as the surround backs.
As with everything in this hobby it all really comes down to how your room is laid out, what amplification you're using and of course your own preference.
I use these as rears, would I be better changing them to direct firing speakers to get a more in your face surround sound
I havn't heard those but something like the Q Compact might well have that effect. Based purely on design and spec.
One of those people suggesting this is George Lucas, so it cant be an altogether terrible idea.
The Q2ds is a di-pole speaker with an auxillary bass driver. Di-poles are inherently a bit bass light (the out-of-phase driver arrangement cancels at low frequencies). The auxillary bass driver is there to try and help overcome that, it it operates from around 220Hz downwards - according to their website.
If you are running a 5.1 system with these as the surrounds, then certainly you will get a more in your face surround sound (in the sense of steering) were you to swap to some bipoles or more ideally -as KEF don't make any - the KEF compact speaker.
The compact won't have the full spread of a bi-pole, but it does have a wider spread than a conventional speaker due to (in very simple terms for the purposes of here) the horn loading effect on its tweeter.
Lost Cause - thanks
I have a 7.1 set-up
Fronts Kef ref 2.2
Rears Kef Q2ds
Centre Rears Kef Q60s
Sub Rel Stadium III
Do you think Kef compacts could be a little light weight. Would Kef TDM34's be better if I could find a pair.
Also - if I replace my Q2ds's would these be suitable as centre rears or should I stick to monopoles in this position as others suggest
In the context of your system - the big Ref 2s - then the compacts may indeed be a little lightweight. For centre back duties, I certainly would not be using a pair of di-poles (such as TDM34ds or the Q2ds). This role requires a direct radiating speaker of some description, such as a monopole (conventional speaker), or a bipole. Perhaps a pair of RDM1s or more ideally the RDM2s might be perfect for this if you can find a secondhand pair (they are a rare beast though), otherwise go for a bigger bookshelf set in the Q series or XQ range. That's assuming you want to change your Q60s.
If you are happy with your Q2ds on the sides then please don't let me discourage you. However, if you are looking for more 'in your face surround', so that things whip diagonally across the room good enough to point at, then I wouldn't be using di-poles anywhere in the system - particularly on the sides (in the case of a diagonal effect). Others may disagree and prefer a more diffuse ambient approach - but that's for you to decide.
Therefore, in your shoes, to fulfill my own preferences for good steering, I would be using some conventional Uni-Q speakers all around the system - for sides and rears. The Uni-Q system is well suited to such a role as they do have a wider dispersion than most normal speakers. At this point you will have excellent steering and plenty of ambience going on in the room.
A di-pole can do the ambience a degree better than a straight Uni-Q, but you will be sacrificing all positional and stereo information. It will just all go into a big pot called ambience - reveberating in the room.
As I say, the latter is exactly what some people are looking for. However, those looking for flashes across the room, and across the back, will need to abandon their di-poles.
How about rewiring the Kef dipoles so that the drive units are in phase?
There's a good article on surround speaker choices here:
Thanks for your help and advise.
What a great article that is. I didn't know the 6/7 channel on a 6/7.1 set-up was not discrete but matrixed from the rears.
My amp can matrix a 5.1 to give me my 7.1 but I assumed DVD's stating 6.1 ES had a discrete track for this channel.
I was also convinced that monopoles must be best in this position but they were unamimous in going for dipoles.
How do I wire my Q2ds to try the monopole option you suggested. I read about the M&K's in the article but my eyes glazed over. Could you explain in simple terms - I don't want to screw my amp up.
There is actually a DTS ES discrete format and from I've read this is the only true 6.1 format available but I still have not seen this format on a DVD as yet.
Just thought I'd complicate things a bit
I think the article really emphasises that there's no right way to go about choosing your surround speakers, you just have to try and hear the different types and go with whichever flavour you prefer. The M&K's weren't too complicated, by flipping some switches on the back of them it changes the internal wiring so they can be used in whichever mode you like best.
I'm not sure how possible it would be to get into the Q2DS to actually do the rewiring but it would just be a case of switching the speaker leads that attach to one of the drivers around so that it's out of phase from it's original dipole arrangment - bringing the drivers back into phase. It may be tricky to pick the right speaker to do this to so it would be important to run the THX optimiser afterwards in case you've made both drivers act out of phase with the input terminals. It's really simple to visualise but a pain to describe I'm afraid.
Also, skinny's right that there is a discrete 6.1 DTS format available although it's worth remembering that there is also a matrixed version like DD.
Most rear speakers are able to be config to di/bi pole. Go with the sound that floats your boat
Personally if you are are close to the rear wall and speakers and are (listening position)just a fraction ahead them then dipole would be my first choice.
Living room layout?
My layout is as you suggest - the settee has to go against the back wall with the centre rears directly above.
I was using Mission 78ds' here, which were ok. Always wanting to improve, I read some opinions, including from Kef that strongly recomended monopoles in this position.
I sold my Missions (on this forum) and put up some Kef Q60s that I had stuck in a cupboard years ago.
These were not an improvement.
I know this position is the least important one for speakers but its still nice to get it right.
I had it in mind to get something weightier than my Q2ds as rears and use these as the centre rears but they stick out somewhat and would look like shelves directly above our heads. Therefore, asthetically, I like missions in this position as their dipoles are relatively flat (and available in white/silver which is less obtrusive over your head)
I am committed to going back to dipoles in this position. Anyone got any other reccomendations bearing in mind I want good quality but unobtrusive.
Also, still interested in suggestion as to what I could do to significantly improve on my Q2ds' as rears, bearing in mind they must integrate reasonably with my front 3 (Kef ref 2.2s' and ref 200c)
Cheers - Steve
Have you considered some 'in walls' ? M&K's ? Kef's are switchable between Di and Mono pole ( as are others, just using these as eg. ) so might be something to look at ? http://www.kef.com/products/ciseries/ci130ds.html
I hadn't thought about that.
Can you get the same quality out of 'in walls'.
Can they perform as well as speakers in specifically designed boxes/casings.
When you read manufacturers literature they go on about the 'structural integrity' and 'super dense, vibration deadening materials' etc, etc
I can see this opening a whole can of worms and lengthy debates.
IMO if you are prepared to spend the money you will get excellent sound. M&K have an undisputed pedigree and my bet would be that their 'in walls' would out perform many 'box/cabinet' speakers. I havent heard the kefs but have seen them and look well constructed like all their others.
This gives a more technical look at the 'in walls'
Anyone else got first hand experience ??
Sorry Steve N
One more thing, check this post I found on this forum.
Thanks again. Looks like ive got some homework to do.
Cheers - Steve
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