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post #1 of 22 Old 12-26-2009, 05:10 PM - Thread Starter
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I set up a pair of dipole/bipole speakers yesterday and I'm not sure they are working as they should be.

With bipole the sound is loud from the outward facing drivers and the sound from the other drivers can hardly be heard. The only difference when I switch to dipole is that the inward facing drivers get even more quiet.

Is this how it should sound? If it is should I consider switching the 2 speakers round as there is no wall directly to the right of one of the speakers?

Thank you.
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post #2 of 22 Old 12-27-2009, 10:15 AM - Thread Starter
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Does anyone know if this is correct?
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post #3 of 22 Old 12-27-2009, 01:30 PM
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The problem is that your post is confusing. First, it would help if you posted the brand and model of speakers. Second, I don't know what you mean when you say "outward" and "inward". Bipole and dipole surround speakers (are you even asking about surround speakers?) have drivers that face to the sides - is that what you mean by outward? Real bi- and dipole speakers will not have drivers facing you (inward?) but often times they're not 100% dipoles and have a mono bass driver facing inward. Is that what you are referring to?

Ed
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post #4 of 22 Old 12-27-2009, 03:57 PM - Thread Starter
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Sorry Ed. Reading back on my post I can see how it's very confusing.

The speakers models are Polk LSIFX. They are surround speakers attached to the rear wall with drivers pointing in 2 directions. The drivers that I refered to as pointing inward are the ones that are facing the center of the room (Because of how they are hung they are unfortunately pointing at the seating area.) The drivers that I refered to as pointing outward are the ones that are facing the walls.

Thank you for the response.
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post #5 of 22 Old 12-27-2009, 08:56 PM
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Take the two speakers and switch their positions on the wall. Put the left speaker where the right one is mounted and put the right one where the left one is now. Don't change the orientation of the drivers.

Reason? If they are truly dipoles, you may be creating a null in the center if you have 180 degree out of phase waves propagating towards each other. By changing left/right placement, you would reverse that effect and have in phase signals reinforcing each other and the sound should be dramatically different (louder). The out of phase half of the dipole would then be bouncing off your side walls and creating a sense of diffuse sound.

If your Polks are truly bipoles, reversing them should have no impact as the signals coming out of both sides will always be in phase give or take the arrival time at your ears. If you are seated equidistant from the left & right speakers phase differences should be nil.

Be aware that surround channels are not constantly active in either movies or multichannel music. In fact they are not active much of the time and when they are they may be handling sounds that are much lower in level than the main L/R channels or the center channel. The best way to test a multichannel level trim is with a white noise signal built into virtually every multi channel receiver and pre-amp.
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post #6 of 22 Old 12-27-2009, 10:06 PM - Thread Starter
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So is it ok that one driver is hardly producing any sound?

The speakers have a switch on them which allows them to be used as either dipoles or bipoles. I can not tell the difference between the 2 settings even when putting my ear close to the speaker. One driver gives off a lot of noise while the other one seems to give off the same sounds but much more quietly. This doesn't even change when I play in 5 channel stereo. From what I understand from memory and all the reading I have done in this forum I should certainly notice a difference between bipole and dipole when standing directly in front of the speaker.

I'm pretty sure I'm missing something and being completely ignorant in the subject but I will switch the two speakers anyway. Thanks Magnefied. And thank you for such a detailed response.
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post #7 of 22 Old 12-27-2009, 10:42 PM
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Quote:
Originally Posted by andrewtodd View Post

So is it ok that one driver is hardly producing any sound?

The speakers have a switch on them which allows them to be used as either dipoles or bipoles. I can not tell the difference between the 2 settings even when putting my ear close to the speaker. One driver gives off a lot of noise while the other one seems to give off the same sounds but much more quietly. This doesn't even change when I play in 5 channel stereo.

I'm pretty sure I'm missing something and being completely ignorant in the subject but I will switch the two speakers anyway. Thanks Magnefied. And thank you for such a detailed response.

Something obvious. Are the speakers fused? Is there a blown fuse or circuit breaker?

How do you have the trim set for the surrounds relative to the front and center channels? Turn on the test signal (aka white noise generator) on your receiver or preamp. Cycle through each speaker. Do the levels sound similar subjectively? If not, check the trim (level) in your reciever's setup routine.

If you haven't got them out of phase and it's not a trim problem and fuses aren't blown, check the speakers and amp channels by taking the surrounds and hooking them up to the front outputs for a minute. If they sound more lively, it's not the speakers. It may be the rear channel amps. Now take your front speakers and hook them up to the surround channels for a minute. Do they seem to have the same problem as your surrounds? More evidence that something is amiss with the surround channels other than your speakers.

Are the speaker wire connections for the surrounds well terminated and solidly attached on both ends? How long a run of wire did you use for the surrounds and what is the gauge of the wire? I use 12 gauge wire for all connections because it's pretty much an all purpose solution unless you have a really long run. A long run with light gauge wire may increase resistance to the point that your receiver can't deliver enough current to power the speakers effectively. Solution? Get a bigger pipe/wire.
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post #8 of 22 Old 12-27-2009, 10:45 PM
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Dipole: one driver sucks while the other driver blows

At the center line, between the two drivers, the sounds cancel each other and you have a null. Although I don't like dipoles at all

for home theater, this would be the configuration that THX recommends for SIDE surrounds.
Bipole: both drivers suck or blow at the same time

At the center line, between the two drivers, the sound is reinforced instead of cancelled and the net result

(in a properly designed unit) is a hemispherical soundfield, equal in all directions. This would be the proper setting for REAR surrounds. Even THX recommends this for Dolby 7.1. (This is also the configuration *I* would use for SIDE surrounds and is also the Dolby recommendation!)

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post #9 of 22 Old 12-27-2009, 10:56 PM
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Quote:
Originally Posted by ekb View Post

The problem is that your post is confusing. First, it would help if you posted the brand and model of speakers. Second, I don't know what you mean when you say "outward" and "inward". Bipole and dipole surround speakers (are you even asking about surround speakers?) have drivers that face to the sides - is that what you mean by outward? Real bi- and dipole speakers will not have drivers facing you (inward?) but often times they're not 100% dipoles and have a mono bass driver facing inward. Is that what you are referring to?

Ed

In a surround application you're right but there are planar dipoles like Magnepan and Martin Logan that do indeed point one side of the dipole output directly at the listener and reflect the 180 degree out of phase back wave off the room boundaries behind the speaker. I use Maggie 3.6's as my main speakers in a 7.1 channel setup and I love em.
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post #10 of 22 Old 12-28-2009, 09:42 AM
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Quote:
Originally Posted by Magnefied View Post

In a surround application you're right but there are planar dipoles like Magnepan and Martin Logan that do indeed point one side of the dipole output directly at the listener and reflect the 180 degree out of phase back wave off the room boundaries behind the speaker. I use Maggie 3.6's as my main speakers in a 7.1 channel setup and I love em.

Yes, I realize that - in fact, that's why I added the question in parentheses about whether the OP is talking about surround speakers.

Ed
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post #11 of 22 Old 12-28-2009, 07:44 PM - Thread Starter
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Thank you for all of the responses. They are much appreciated.

I understand the difference between bipole and dipole which is one of the main reasons I'm questioning if these are working correctly. I would certainly expect to hear a difference when standing in the center of the 2 drivers. I've spent hours reading through other threads and articles trying to work this out.

The speakers do seem to produce a lot of volume; Just not in the way I was expecting. When I set the speakers as bipole I was expecting the volumes levels being produced by each driver to be similar and there is no comparison. (You may tell me that was an incorrect assumption.) I set the speakers up using Audyssey on my Integra 40.1 (via emotiva UPA5) and during setup the volume produced by the rears speakers as a whole seemed to be similar to that of the fronts.

I'm not sure if the speakers are fused but would it not be slightly coincidental for the fuses of both speakers to have gone at the same time? Additionally, if the fuse had gone would they be producing any sound at all?

I also use 12 gauge wire for my speakers. The cable length is approximately16 feet to each speaker.

I have already tested the rear speakers using the amp output from the fronts. I have not, however, done this with the front amps connected to the front outputs on the processor. I shall try this tonight.

Thanks again for all of the responses.

Andrew
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post #12 of 22 Old 12-29-2009, 10:03 AM
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Quote:
Originally Posted by andrewtodd View Post

When I set the speakers as bipole I was expecting the volumes levels being produced by each driver to be similar and there is no comparison.

I think that they should be the same volume. Sounds like the speakers are broken or defective.

Ed
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post #13 of 22 Old 12-29-2009, 10:17 AM
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Quote:
Originally Posted by Magnefied View Post

Take the two speakers and switch their positions on the wall. Put the left speaker where the right one is mounted and put the right one where the left one is now. Don't change the orientation of the drivers.

Reason? If they are truly dipoles, you may be creating a null in the center if you have 180 degree out of phase waves propagating towards each other. By changing left/right placement, you would reverse that effect and have in phase signals reinforcing each other and the sound should be dramatically different (louder). The out of phase half of the dipole would then be bouncing off your side walls and creating a sense of diffuse sound.

Say what?

Speaker design is rather an art. There is no such thing as the perfect painting. Likewise there is no such thing as a perfect speaker. It's part science and part personal preference.
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post #14 of 22 Old 12-29-2009, 10:21 AM
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The Polk LSiFX is a strange design. I have never seen a dipole/bipole like it

Usually one set of drivers are direct radiating (meaning, pointing at the listeneres head) These don't appear to be setup this way.

Speaker design is rather an art. There is no such thing as the perfect painting. Likewise there is no such thing as a perfect speaker. It's part science and part personal preference.
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post #15 of 22 Old 12-29-2009, 10:30 AM
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Quote:
Originally Posted by DigitalGriffin View Post

Again,

Say what?

The drivers generally are opposed to each other (at least 90 degrees offset), but in the same phase. So when one pushes out, so does the other. This is what creates the null space. (Imagine two people pulling on a rope with equal opposite force, the net effect is no movement in the middle...creating your null space)

What you're describing is a bipole where both waves are generated in phase. Bipoles can be placed in either the left or right position since they are exactly the same.

A dipole on the other hand generates two waves that are 180 degrees out of phase and a null 90 degrees off axis where the out of phase waves meet. Dipole surrounds are mirror image pairs that have a specified left and right placement. So, if you aim two out of phase waves at each other and you're situated equidistant from the two sources, you've likely just generated a null where the waves meet which also happens to be where you're sitting. By reversing the speaker positions, you might put two drivers that are in phase facing towards the listener as intended by the dipole design. Assuming you had it reversed in the first place.

Since the OP specified these are mounted on the rear wall with one side facing the listener, the dipole phasing issue may be the problem. If they were on side walls, it wouldn't be as much of a problem.
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post #16 of 22 Old 12-29-2009, 11:07 AM
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Quote:
Originally Posted by Magnefied View Post

What you're describing is a bipole where both waves are generated in phase.
.

You're right there. I had a morning brain lapse. :-D I already deleted it before your post when I realized my mistake. I knew better than that. I knew they had to be 180 out of phase, but reversed the image in my head when I typed it out.

But I still didn't understand your previous post. Although from what I understand these Polk LSiF/X do have a left/right side labeled on the back of them near the serial number. Like I said, I never seen a setup like this before. Its unconventional for a dipole/bipole mixed design.

Only the speakers pointing directly at the listeners head should be firing in bipole mode.

I would imagine all speakers would fire in dipole mode.

Speaker design is rather an art. There is no such thing as the perfect painting. Likewise there is no such thing as a perfect speaker. It's part science and part personal preference.
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post #17 of 22 Old 12-29-2009, 01:22 PM
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Quote:
Originally Posted by DigitalGriffin View Post

You're right there. I had a morning brain lapse. :-D I already deleted it before your post when I realized my mistake. I knew better than that. I knew they had to be 180 out of phase, but reversed the image in my head when I typed it out.

But I still didn't understand your previous post. Although from what I understand these Polk LSiF/X do have a left/right side labeled on the back of them near the serial number. Like I said, I never seen a setup like this before. Its unconventional for a dipole/bipole mixed design.

Only the speakers pointing directly at the listeners head should be firing in bipole mode.

I would imagine all speakers would fire in dipole mode.

Not really unusual. These Polks are not the first dynamic driver, box surround speakers to offer both. There's usually a simple switch built into such a design that allows you to flip the phase on one set of drivers in each box 180 degrees to create a bipole or dipole as you wish. Once set to dipole mode, you just have to make sure you've got them mirrored correctly to avoid nulls.

I wish I knew how to upload a sketch. You'd get it instantly from a picture.

Planar speakers like my Maggies on the other hand are natural dipoles. When the front side is generating positive pressure the back side must generate negative pressure and vice versa. Dipoles can be very useful in a real world room. The back wave can provide a sense of space with 2 channel material and the nulls at the left and right side can minimize room boundary interactions with adjacent walls.

Definitive Technology has made a living out of bipole only main L/R box speakers with dynamic drivers as have many other speaker companies dating back to at least the 70's.

And then there's surrounds like mine that don't fit any of these categories but are also set up as a mirror image pair. But I'm too lazy to go into that description.
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post #18 of 22 Old 12-30-2009, 02:09 PM - Thread Starter
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Hi,

I have an update on this issue after following Magnefied's suggestions. I hooked one of the speakers up to the front right output using different speaker cable. When I ran a white noise test in dipole setting, the outward facing driver produced a lot noise and the inward facing driver produced about half as much. When I switched it to bipole, the inward facing driver volume was practically reduced to a whisper.

I think I am going to have to take these speakers back to the store and switch them out for another pair of LSI15s.

thanks
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post #19 of 22 Old 12-31-2009, 12:52 AM - Thread Starter
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I have now returned the speakers. They did not have any others in stock and would not be getting any so now I'm left with no surrounds. I think I'm going to stick with direct radiating speakers for now.

The strange thing was that when we hooked them up in the store although one driver was still lacking it was no where near obvious. Maybe there is also an issue with my processor configuration.
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post #20 of 22 Old 12-31-2009, 08:34 AM
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Quote:
Originally Posted by andrewtodd View Post

I have now returned the speakers. They did not have any others in stock and would not be getting any so now I'm left with no surrounds. I think I'm going to stick with direct radiating speakers for now.

The strange thing was that when we hooked them up in the store although one driver was still lacking it was no where near obvious. Maybe there is also an issue with my processor configuration.

It's hard to imagine a setup issue causing this behavior in a surround speaker. And if the speaker demonstrates the same behavior in your rear channel, your front channel, and the store's setup, it's a safe bet there is something wrong with the speaker.

Don't be put off unconventional radiation patterns because of a defect in one sample of one product. Dipoles and bipoles can be very useful in some situations.

Happy hunting!
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post #21 of 22 Old 12-31-2009, 11:02 AM
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Quote:
Originally Posted by Magnefied View Post

It's hard to imagine a setup issue causing this behavior in a surround speaker. And if the speaker demonstrates the same behavior in your rear channel, your front channel, and the store's setup, it's a safe bet there is something wrong with the speaker.

Don't be put off unconventional radiation patterns because of a defect in one sample of one product. Dipoles and bipoles can be very useful in some situations.

Happy hunting!

I can't say that I have personally heard the polk LSiFX but looking at them physically I would say they are a poor design for a bipole/dipole mix.

Bipoles should directly radiate to the sides of the ear. With the angled speakers of the LSiFX, even directly pointed at the head, you would be hitting the rear outside of the ear at a steep angle. This will cause roll off in the upper frequencies.

Most dedicated bipole bipole mixed speakers have a center firing high frequency driver which points at the side of the head, not the rear quarter. This is why I said the polks are an unconventional design.

I never liked mixed designs. bipoles should be at ear level, dipoles 1->2 feet above. It's really a sub optimal solution even for those with dedicated bipole drivers in the center firing at the sides of the heads.

Speaker design is rather an art. There is no such thing as the perfect painting. Likewise there is no such thing as a perfect speaker. It's part science and part personal preference.
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post #22 of 22 Old 12-31-2009, 01:56 PM
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I googled the speakers, and one thing I noticed is that they are not only Bi/Di Pole switcheable, but Bi-Wire able. I was wondering if the straps connecting the upper and lower portions of the x-over were all tightened properly. It could also easliy have been that the Bi/Di Pole selection switch was bad. Good luck with your next set of speakers.

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