[versus rider]

Why is the simple question, maybe I have this wrong but surely sound from the back of a driver is the last thing needed except in the case of backloaded horns or bass reflex. Everyone batters on about keeping open baffles away from the back wall to reduce reflections and then some use dipoles. I have read on AE's website and there is very little about the case for a dipole. Someone enlighten me

[Rocket_Ronny]

Air and realism, if you have the room behind them.

Rocket_Ronny

[versus rider]

are you sure they give realism or the opposite, if you are correct then would that be right for a woofer? I run 15" alphas in an open box, a kind of folded baffle with a top and bottom if you like, 200Hz tractrix horn and Raals give me all the air and realism I need. I will have to take your word on this as I doubt I will get to hear any dipoles and wanted a technical answer if possible, thanks for your reply btw

[Rocket_Ronny]

Is that your rig in the avatar picture? If so, why worry.

Rocket_Ronny

[versus rider]

Is that your rig in the avatar picture? If so, why worry.

Rocket_Ronny

not worried just interested in the concept of dipoles and how it contradicts the norm. I guess there is more than one way to skin a cat.

[Davey]

One could argue that dipoles are the "norm", and horns...closed-boxes...etc, etc, are the abby-normal examples. 

Cheers,

Dave.

[Rocket_Ronny]

Can you describe your speaker system? Looks pretty wild.

If I were running dipoles in your room I would not put them where you have your speakers now, but pull them out as far as possible. You might want to try that with what you have now.

Rocket_Ronny

[FullRangeMan]

Why is the simple question, maybe I have this wrong but surely sound from the back of a driver is the last thing needed except in the case of backloaded horns or bass reflex. Everyone batters on about keeping open baffles away from the back wall to reduce reflections and then some use dipoles. I have read on AE's website and there is very little about the case for a dipole. Someone enlighten me

keeping open baffles away from the back wall to reduce reflections and then some use dipoles.

All Dipole speakers need free space around to form the 3D soundstage they are capable.
As monopole boxed loudspeakers emits sound to the front only they dont need free room around, unless the BassReflex duct is in back as in the Klipsch RF line.

[JohnR]

wanted a technical answer if possible,

You may find this worth reading: http://www.linkwitzlab.com/rooms.htm

[Davey]

keeping open baffles away from the back wall to reduce reflections and then some use dipoles.

All Dipole speakers need free space around to form the 3D soundstage they are capable.
As monopole boxed loudspeakers emits sound to the front only they dont need free room around, unless the BassReflex duct is in back as in the Klipsch RF line.

Actually, conventional monopole speakers radiate sound also to the rear......up to a certain frequency.  This power response discontinuity is inherent and can't be corrected/addressed with normal modes of equalization.....or even room treatments.

Dipole speakers have an inherent controlled directivity advantage (or "difference" if you prefer.)  This characteristic, along with proper placement, can yield a "presentation capability" not possible with conventional speakers.

Many variables of course.....so mileage may vary.

Cheers,

Dave.

[FullRangeMan]

Actually, conventional monopole speakers radiate sound also to the rear......up to a certain frequency.  This power response discontinuity is inherent and can't be corrected/addressed with normal modes of equalization.....or even room treatments.

Dipole speakers have an inherent controlled directivity advantage (or "difference" if you prefer.)  This characteristic, along with proper placement, can yield a "presentation capability" not possible with conventional speakers.

Many variables of course.....so mileage may vary.

Cheers,

Dave.

Maybe you are referring to Bipolar loudspeakers que had drivers in front side and in the back side too, as the Dephinitive Technology brand:
http://g-ecx.images-amazon.com/images/G/01/electronics/detail-page/BP3000TLCutaways.jpg

[JohnR]

Hi FRM, there is a helpful diagram at the link I provided, section B. The difference in radiation pattern at low versus high(er) frequencies is why conventional speakers have "baffle step compensation." Conventional boxed speakers (drivers on the front) are not monopoles, except at low frequencies. Bipolar speakers like the one you linked are much closer (to a monopole).

With regard to the OP's comment "sound from the back of a driver is the last thing needed" - in actual fact, what a dipole speaker does is not to add sound at the back, but to remove it from the sides. That is assuming that you started with a monopole.

[versus rider]

Hi FRM, there is a helpful diagram at the link I provided, section B. The difference in radiation pattern at low versus high(er) frequencies is why conventional speakers have "baffle step compensation." Conventional boxed speakers (drivers on the front) are not monopoles, except at low frequencies. Bipolar speakers like the one you linked are much closer (to a monopole).

With regard to the OP's comment "sound from the back of a driver is the last thing needed" - in actual fact, what a dipole speaker does is not to add sound at the back, but to remove it from the sides. That is assuming that you started with a monopole.

Hi John would you mind expanding on that. I assume you are talking about a flat baffle r.e. sound from the sides. Are you saying that the back wave cancels the front wave at the sides. I can have my open box close to the rear wall without any noticeable difference than when its pulled out away from the wall. But then that may be my secret trapezoidal designed open box.

[FullRangeMan]

Hi FRM, there is a helpful diagram at the link I provided, section B. The difference in radiation pattern at low versus high(er) frequencies is why conventional speakers have "baffle step compensation." Conventional boxed speakers (drivers on the front) are not monopoles, except at low frequencies. Bipolar speakers like the one you linked are much closer (to a monopole).

With regard to the OP's comment "sound from the back of a driver is the last thing needed" - in actual fact, what a dipole speaker does is not to add sound at the back, but to remove it from the sides. That is assuming that you started with a monopole.

I thought bass freq could reach the back of the speaker, as low bass tends to spread in all directions, and I thought hi freq were highly directional.
Anyway dipole loudspeakers do a wonderful soundstage, much better and rich than the regular front firing speakers.

[JohnR]

Hi John would you mind expanding on that. I assume you are talking about a flat baffle r.e. sound from the sides. Are you saying that the back wave cancels the front wave at the sides.

Yes, that's how an open baffle works. The theory is here: http://linkwitzlab.com/models.htm Or for a less technical summary the "open baffle theory" section of this article may help.

It doesn't have to be a flat baffle though e.g. the popular H-frame. With something like a box open at one end as you have it doesn't quite work like that, see the JohnK explanation here: http://musicanddesign.com/u_frame.html

I can have my open box close to the rear wall without any noticeable difference than when its pulled out away from the wall. But then that may be my secret trapezoidal designed open box.

I'd like to see some measurements

[versus rider]

sorry John not much chance of that this side of Christmas as the speaker system is stripped for painting. The it will be installed into my new listening room thats nearing completion. As I use DEQX to correct phase and timing errors measurements are not needed. This thread has slipped off course, I still don't see the point of a dipole woofer.

[rjbond3rd]

...I still don't see the point of a dipole woofer.

Hmm, from your description, what you have is already a dipole woofer (unless I've misunderstood).

I run 15" alphas in an open box, a kind of folded baffle with a top and bottom if you like...

[JohnR]

As I use DEQX to correct phase and timing errors measurements are not needed.

I don't have a DEQX but I've watched two people use and demonstrate them... and all of the processing done by the DEQX is done by taking measurements, isn't it?

This thread has slipped off course, I still don't see the point of a dipole woofer.

Well, as just pointed out, you have one, more or less. So why did you do that?

[studiotech]

I thought bass freq could reach the back of the speaker, as low bass tends to spread in all directions, and I thought hi freq were highly directional.
Anyway dipole loudspeakers do a wonderful soundstage, much better and rich than the regular front firing speakers.

You are correct and the other description of monopole behavior was backwards.  As we drop in frequency, the sound waves get longer and wrap around the sides of the cabinet.  Below a certain point based on the wavelength and width of the baffle, the sound becomes omnidirectional, rather than unidirectional.  This is why the power response(in other words, the total sound radiation sent into the room) of traditional box speakers is so different from low to high frequencies.  An perfect dipole loudspeaker(which very few are) sends the same energy out the front and the back at all frequencies, which as a secondary effect cancels some of the sound directly to the sides, hence a figure 8 radiation pattern if viewed from above.  Get this too close to the front wall and you do NOT get a better, more spacious soundstage.  Instead, the front combines with the rear wave after bouncing around and destroys all of the delicate spatial cues that were hopefully captured in the original recording.  The rear wave needs to be delayed AND lowered in level before it gets to your ears to be beneficial.  Even then, there is always a sameness to the sound with most dipoles in average listening rooms.  Not my cup of tea.

My own personal preference is to achieve something closer to a cardioid radiation pattern to eliminate as much of my rooms sound as possible.  Taking the rooms effect OUT of the equation is the only way to hear what was actually recorded.  Not to say that this is the only solution, but to me is sounds more "right".

Greg

[JohnR]

You are correct and the other description of monopole behavior was backwards.  As we drop in frequency, the sound waves get longer and wrap around the sides of the cabinet.  Below a certain point based on the wavelength and width of the baffle, the sound becomes omnidirectional, rather than unidirectional.

Err... just so we're clear on the definition, what you are describing is not a monopole. (?)

http://www.linkwitzlab.com/rooms.htm#B