Dipole speakers

[oon_the_kid]

Hi,

I've come across a few speakers where the tweeter is placed to face both front and back. I am not sure what the advantage is, can anyone care to enlighten me on this.

Thanks.

Oon

[gainphile]

Not only back-to back, they are reversed in polarity to be a dipole.

Good read here:
http://linkwitzlab.com/orion++.htm

Personally I have found this as required for dipole speakers (OB) to sound correct.

[eeyore]

Have done this with my Fostex FE127e MLTL. Only two drivers, mounted back to back. I have not hard wired them together, so there are two sets of posts on the back, which allows me to test in phase and not in phase and even not connected.

Have found that not in phase better, and also found that the speakers need to mounted well away from a wall so that you don't get weird reflection and time-delay in sound. Makes it rather disturbing to me.

[Warning: Basic understanding only!]
But from my understanding, the bipole/dipole helps to reduce the problems associated with Baffle Step errors, and acts as a BSC circuit. Again, my basic understanding is about the diffraction of the sound waves around the baffle (the front surface of which the speaker is mounted) which varies with frequency. I think, the higher the less diffraction and the lower the more. It also depends on the width of the baffle.

[Rudolf]

Originally posted by oon_the_kid
I've come across a few speakers where the tweeter is placed to face both front and back. I am not sure what the advantage is, can anyone care to enlighten me on this.

In dipole applications woofers and midrange drivers radiate to both sides - front and rear. Most tweeters only radiate to the front. If you equalize for a linear direct (front) response with only a front tweeter, the power response will be treble shy. You need a backward tweeter to make the power response resemble the direct response.

There is one exception: If your front wall is heavily damped (live end, dead end), the radiation from the rear tweeter wouldn´t reach you anyway.

Originally posted by eeyore
But from my understanding, the bipole/dipole helps to reduce the problems associated with Baffle Step errors, and acts as a BSC circuit.

This is only true for bipoles. Dipoles don´t have a baffle step, but a constant 6 dB roll-off.

[LineArray]

Originally posted by Rudolf


If you equalize for a linear direct (front) response with only a front tweeter, the power response will be treble shy. You need a backward tweeter to make the power response resemble the direct response.

Hi,

this is exactly my experience. Even when using an equalized
fullranger as dipole which has a flat response in the
SPL radiated to the front.

Depending on the size of the cone and construction of
spider/basket there will be a drop in the highs above a few
Khz in the sound radiated backwards with every fullranger.

This is why i compensate for the drop by using backward
radiating tweeters in my dipole 08 design.

www.dipol-audio.de

To keep radiation as symmetric as possible between front
and back is very advantageous IMO.

Symmetrical direct/indirect radiation makes an OB more
independent from positioning and avoids the typical
"treble shy" sound you mentioned, especially when listening
at larger distances, where the power response gets more
important.

Best

[oon_the_kid]

Thanks for all the response.

I just bought a Mark and Daniels AMT recently which goes down to about 750Hz. The interesting thing about it, is it has holes at the rear too. So I am considering using it as dipole speakers, since no additional tweeters are necessary. open baffle if you like to think of it.

Another interesting approach mightbe the use f wideband tweeters from jordan, bandor, markaudio or any other FR in open baffle configuration, with an additional woofer in a box to provide the bass, Would that work?

Is it absolutlely neccesary for them to be situated far from the wall?

Oo

[eeyore]

That is something similar to what I am doing, using a Jordan (or Markaudio) FR speaker in a smallish box (ported, sealed and/or MLTL) and then supplementing that with a woofer.

However, Martin King has done this with OB and a woofer, Check out his site.

I have found with dipole that they do need to be position well away (at least 0.5m) from the wall behind and also have some distance from the side walls (at least 1.0m).

[oon_the_kid]

Hi eeyore,

I built a satelite sub system using the J6T from markaudio. Subs were commercial, the satelite were built on flower pots with a wooden front. The sound is pretty good, but one thing lacking was a punchy bass. The J6T didn't go low enough, but using the subs to fill it causes the bass to be a bit muddy, since sub bass is not very fast.

The J6T benefits from using a small super tweeter, makes the sound more airy.

I will probably be using the markaudio alpair 6 for my next project. BTW, i am sure you are aware but there is an additional cousin to the Jordan, and that is the Bandor, if you ever decide to consider them.

Oon