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Discussion Starter · #1 ·
I'm making some adjustments to my HT speakers. I'll be lowering the surround speakers all around by about 12 inches (they're right up by the ceiling now), and I'll be pointing the two rears towards the main listening position (instead of straight ahead).


My side surrounds are bipole/dipoles (which I use in bipole mode). Can I tilt these toward the main position to, or should bipoles always be left pointing "level"?


Thanks! - Cryo
 

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Discussion Starter · #2 ·
BUMP
 

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I think the closer you can get them to ear level or slightly above the better.

Mine are around 6ft from the floor.
 

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I would not tilt or angle them. They are supposed to produce a diffuse sound field and tilting or angling them reduces that effect.
 

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I disagree. A bipole surround speaker is specifically intended to be placed with the null aimed at the listener. Recommended placement for such a speaker is in line and to the sides of the listener. In this case, the null is pointed at the listener. If the placement must be elsewhere (for example I had to move them forward about two feet in my previous house since the ideal location happened to require placing the speakers IN 14x14" posts), it is appropriate to orient them so that the null is correctly positioned.


Failing to do so would mean that one of the drivers is oriented toward the listener, thus making the sound field less diffuse.
 

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In the Def Tech speaker setup guide that has been linked to a few times on this forum they recommend toe'ing-in their bipolar speakers.


Just thought I'd make note of that.


I have my speakers setup as such. I'm not sure that I have the "perfect" speaker positioning, but I'm not really sure my room allows for it.


Here's a diagram of my setup of anyone wants to offer any suggestions or if you want to use it as a reference for your own speaker setup.

http://barney.gonzaga.edu/~naschbac/Sub_placement.gif http://barney.gonzaga.edu/~naschbac/...ment_small.GIF


Click image for larger view.


-Nathan
 

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Discussion Starter · #7 ·
Quote:
Originally posted by blw
I disagree. A bipole surround speaker is specifically intended to be placed with the null aimed at the listener. Recommended placement for such a speaker is in line and to the sides of the listener. In this case, the null is pointed at the listener. If the placement must be elsewhere (for example I had to move them forward about two feet in my previous house since the ideal location happened to require placing the speakers IN 14x14" posts), it is appropriate to orient them so that the null is correctly positioned.


Failing to do so would mean that one of the drivers is oriented toward the listener, thus making the sound field less diffuse.
They are directly to the sides (maybe back less than a foot), so that's covered. Since they're about 2 feet above the listening position, my question is should they ever be angled downward toward the main position or left to point straight above the heads of the listener?


- Cryo
 

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Quote:
Originally posted by Cryofax
They are directly to the sides (maybe back less than a foot), so that's covered. Since they're about 2 feet above the listening position, my question is should they ever be angled downward toward the main position or left to point straight above the heads of the listener?
I don't think I'd bother. As it stands right now, I think you'd have them pointing away from the listener, and that's what you want. Unlike the L/C/R mains, you do not want them aimed at you (that's why the null is aimed at you!).


I suspect that there might be some secondary considerations as to what walls or ceiling they might fire into, but that would be less important than getting the null correct. And you can try this out, too. See which you like better before you sew up the wall again.
 

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I'm confused by this positioning of the null zone in the firing speaker.


Should I have the BP8's in my diagram turned nearly 90 degrees from how they are orieted now so that the broad-side of the speaker faces the listening position?


-Nathan
 

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Originally posted by blw
I disagree. A bipole surround speaker is specifically intended to be placed with the null aimed at the listener.
[/QOUTE]


Dipoles have a null because the front and back drivers are 180 degrees out of phase. Where they meet at the sides the sound cancels - you can stick your head beside a true dipole playing > 100dB and it's not that loud (I use open baffle main speakers which have a dipole radiation pattern below 1440Hz). THX style dipole surrounds change the phase relationship so that they get reasonable bass in a small package so this demo won't work as well on them.


Bipoles don't have a null because their drivers are in phase so there is no cancelation. However, rigid driver cones/domes become increasingly direcitonal with frequency so you're still getting less treble energy at the side of the speaker which makes it less localizable.


If the speakers are close to ear level I would run them with drivers firing fore and aft. I used to run BP8s for side speakers in that configuration. Compared to having the drivers aligned with the listeners it was more immersive, less gimicky, and the surround field didn't collapse as badly into the nearest speaker when yo usat off center.


A few feet above ear level gives you more options. I now have BP1s hanging from the ceiling upside down, the the "tops" 6' off the floor (ear height is abut 3') ~5' from the listeners. I have them level with the drivers firing over the listeners' heads with no ill effects - you're already listening off-axis and getting roll-off.


Definately don't point them directly at you though.
 

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Quote:
Originally posted by Drew Eckhardt
Definately don't point them directly at you though.
So then you'd say that the way mine are setup is sub-optimal as they are all pointing at the center seating position.


By looking at the diagram do you have an suggestions about front angle, and rear position/angle for my BP8's?


-Nathan
 

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Discussion Starter · #13 ·
Quote:
Originally posted by naschbac
So then you'd say that the way mine are setup is sub-optimal as they are all pointing at the center seating position.


By looking at the diagram do you have an suggestions about front angle, and rear position/angle for my BP8's?


-Nathan
Judging by the "sound waves" in your diagram, you're using bipoles not just for your surround but for your L & R fronts as well? Never heard of that. Also shouldn't the surrounds be to the side of the listening position, with the "waves" coming out toward the front and back, not one side toward the listener and the other toward the wall.


- Cryo
 

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I assume many many people use bipoles for their front speakers.


I mean afterall most of Def Tech's large speakers are bipoles.


I'm not sure how to setup up the rears. I know with monopoles that you aren't supposed to aim the rears directly at you but bipoles make a more diffused sound field because of the rear firing speakers. The bipoles that are designed to fire to the front and rear as rear speakers have drivers which aren't oriented opposite eachother, rather they are arranged at about a 120 degree angle from eachother or less, and also fire somewhat into the sound stage.


My problem is that I don't know how to orient a set of tower bipoles like the BP8's as rear speakers.


Thanks,

-Nathan
 

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For bipolars as rears, I've had good luck with them pointed directly at the seating area, with the tweeters anywhere from 12" minimum to maybe 36" above ear level.


I had BP-30's up front for a while. Liked them a lot.
 

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Quote:
Originally posted by Drew Eckhardt

Bipoles don't have a null because their drivers are in phase so there is no cancelation. However, rigid driver cones/domes become increasingly direcitonal with frequency so you're still getting less treble energy at the side of the speaker which makes it less localizable.

[/b]
This is simply not true. Bibpoles do have a null, or at least a zone in which they do not directly radiate at you.

Quote:


If the speakers are close to ear level I would run them with drivers firing fore and aft.
Precisely. If they are firing up the wall to the front and back the wall to the rear, they have an axis on which the cones don't radiate, and that axis is what should be pointed at the listener. I thought that was called a null, but perhaps this is a terminology problem.
 

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This is driving me nuts.


There doesn't seem to be a definitive (no pun intended) ruling on bipolar speaker placement.


One suggestion is to have the broad side facing the listening position so that the only sound reaching the listener is diffuse or reflected.


Another suggestion is to have the front set of drivers radiating directly at the listening position.


Then yet another is to have the drivers slightly off axis with the listener so that they aren't completely faced with their null toward the listener.


Here's a quote from the Definitive Bipolar setup guide that was posted on this forum a while back:

Quote:
08) Bipolar speakers must be toed in for proper performance. The toe in angle generally ranges from seeing the inner third of the front baffle as you look to the speakers from the listening position to having the front baffles directly on axis with your ears.
Which is confusing in and of itself. For instance what the hell is the "...inner third of the front baffle..."?


I assume it means the front of the speaker, being where the front drivers are mounted. Assuming that much I can't even conceive of how I could be sitting in the main seating position and orient the speakers so that I can only see the inner third of that face of the speaker. I mean the thing is square edged, I'm either going to see the face or not.


Can anybody anywhere come up with what the real answer is?


I'd really like to position my speakers how they are "supposed" to be so I can recalibrate everything, but I don't know if I should face my front speakers at me, away from me, upside-down, etc. and the same goes for the rears. :D

http://barney.gonzaga.edu/~naschbac/Sub_placement.gif http://barney.gonzaga.edu/~naschbac/...ment_small.GIF


Click image for larger view.


-Nathan
 

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If I'm the one confusing you, I was only referring to surrounds, which is what the original question was about. Your front speakers are a different matter. I have personal experience with bipolar surrounds, and I know how they work and how they're supposed to work. I've never even thought about bipolar mains.


I think as far as "the inner third goes", that's referring to a position that is mildly toed in. At least in my room, such a position results in the axes of the speakers - we're talking about front channels now - crossing somewhat behind the listening position.
 

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Okay, then for the fronts I more or less have them positioned properly.


For the rears I should have the speakers running parallel with the walls, or perhaps even have the front pointing at the wall so the rears fire more out into the room and the reflection off the wall from the front driver bounces into the main listening position?


Do I have that right?


Thanks for the help, I was getting highly confused :)


-Nathan
 

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Quote:
Originally posted by blw
This is simply not true. Bibpoles do have a null, or at least a zone in which they do not directly radiate at you.



Precisely. If they are firing up the wall to the front and back the wall to the rear, they have an axis on which the cones don't radiate, and that axis is what should be pointed at the listener. I thought that was called a null, but perhaps this is a terminology problem.
A more precise way of phrasing things is that at high frequencies the bipole does not radiate sound to the sides. At low frequencies it does.


I'm being intentionally pedantic because this difference from dipoles makes optimal bipole surround placement more difficult.


On a pure dipole (drivers 180 degrees out of phase) this behavior is not frequency dependant - at low frequencies you actually have a cancellation (null) at the sides. This means that you can place a dipole much closer to a side wall without a bass boost, or closer to the listener without it calling attention to itself.
 
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