Dipol-Cardioid subwoofer

[Leo K]

Hi,

do you want to know more about the Dipol or Cardioid speaker?

In our photo story we do explain the acoustical shortcut and the sound waves.

With our experiments we show a new Dipol – Cardioid subwoofer with the efficiency of a normal subwoofer.

To download at

http://www.kirchner-elektronik.de/~kirchner/DIPOL-CARDIOIDeng.pdf

Leo K

[ThomasW]

Interesting stuff thanks for sharing...... :T

[seattle_ice]

Very interesting.

How much is the response dependent on the actual dimensions of the enclosure?

[brianpowers27]

The FR i s absolutely dependent on the path length from the front to the back of the enclosure. As you make the cabinet larger(in scale) the LF response will improve at the expense of focused directivity.

[Rudolf]

With our experiments we show a new Dipol – Cardioid subwoofer with the efficiency of a normal subwoofer.

Leo,
I see virtually no hint to anything like a cardioid -it's all purely about dipoles. And I do not see any valid comparison (under common measuring conditions) between your subwoofer and a normal subwoofer. So you don't show what you claim IMHO.
But thank you for the interesting (and comparable) measurements of a dipole with a "pressure" microphone and a pressure gradient microphone (by no means these are true "velocity" measurements).

[Piotr]

I can't see no cardioid behaviour either.

Feels like emperors new cloths since the design is almost identical to the dipole W-baffle Siegfrid Linkwitz published years ago.

Interesting reading none the less.


/Peter

[Leo K]

Rudolf,

the subwoofer is a dipole speaker with the high efficiency of 91dB 1W/1m. That’s new. Because there is also a small cardioid characteristic we named it Dipol-Cardioid.
The discussion about pressure gradient and velocity we have to make at another place.

The difference to the Siegfrid Linkwitz sub is the high efficiency.

Leo

[Rudolf]

... the subwoofer is a dipole speaker with the high efficiency of 91dB 1W/1m. That’s new.

Sorry, I failed to find a measurement in the PDF showing that. Where is that free field measurement with 91dB 1W/1m?

Because there is also a small cardioid characteristic we named it Dipol-Cardioid.

Sorry, as long as the 90° SPL is less than the 180° SPL, it can't by definition be cardioid. I don't think that we should be allowed to name a cow a bird, when it doesn't even have wings. Dipole and cardioid are mutually exclusive.

The discussion about pressure gradient and velocity we have to make at another place.

Sure. From my side it's more about naming than about function anyway.

[john k...]

Oh my!

[dlr]

Oh my!

I was wondering if you'd find this thread. :E

Dave

[Piotr]

Rudolf,

the subwoofer is a dipole speaker with the high efficiency of 91dB 1W/1m. That’s new.

As mentioned there are several identical designs published allready with the same W-baffle. The sensitivity of the sytems obviously depends on the drivers you pop into the baffle. Really nothing new here.

Because there is also a small cardioid characteristic we named it Dipol-Cardioid.

I think that's erroneous and confusing. I tend to agree with earlier poster about the 90deg. vs. 180deg. radiation. If anything I think the design should be called hypercardioid but really it is a dipole with less than perfect symetry.

The difference to the Siegfrid Linkwitz sub is the high efficiency.

Which as mentioned is not about the design as such but about the drivers used in the design.


/Peter

[Space]

Oh my!

Hey John K, as someone who knows a few things about this subject, maybe you could elaborate on that comment?

[john k...]

Hey John K, as someone who knows a few things about this subject, maybe you could elaborate on that comment?

I don't want to go into this very far so I'll just point out that if you look at the last figure in the pdf file (fig 7.1) you will see that the woofer is basically an asymmetrically loaded W frame. That is, the rear of the drivers are loaded by a finite volume exiting through a slot. The front side is loaded by the V shaped volume. The point being that unless the front and rear loading is identical there will be asymmetries in the between the front and rear response SPL magnitude and phase due to resonance peaks and the summing will reflect this. Since there appears to be no attempt to damp these resonances (as in a damped U-frame, for example) one would expect a dipole like pattern at low frequency and a filling of the side nulls as the frequency rises. If you look at the polar plots, Fig 5.6 of the pdf, note the similarity to the undamped U-frame between 20 and 50 Hz at the upper right of the figure below.



Looking at the phase response in Figure 6.3 of the pdf, there appears to be indication of the enclosure resonances in the 100 to 300 Hz range.

There is certainly no reason to suggest that anything here would act in any manner differently than a conventional dipole woofer aside from the artifacts due to the asymmetries.

And of course, any claims about sensitivity have to be tempered by the fact that gradient sources (dipole, cardioid) have a sensitivity that is frequency dependent droping at 6dB/octave as F drops.

[EssiB]

Dipol-Cardioid

Hello everyone,
the introduction of the Dipole-Cardioid from Leo Kirchner has caused a heated-up controversial Discussion especially here in Germany.

Another German technician named Axel Ridthaler has a patent on a similar looking Sub-Woofer, he calls Ripol. And his “invention” is very similar to the the Linkwitz Sub-Woofer.

Obviously though many have not completely understood the Kirchner Paper. So what's the Buzz, what's so new about the Kirchner Dipole in comparison to to the Linkwitz or Ridthaler Dipole-Sub-Woofer ?

Well first of all Kirchner calls his Sub-Woofer Dipole-Cardioid, because it's a Dipole that has a Cardioid tendency. So far the kind of Cardioid-Sub-Woofer with the best cardioid behaviour, (meaning the highest front to back radiation ratio), is probably the combination of dipole with monopole. Although the Kirchner Sub-Woofer has only a small cardioid tendency it still makes a difference as far as the excitement of room modes go.

As well as the Ridthaler Dipole, the Kirchner Dipole achieves a lower Cabinet resonance by rising the the air-load that the speaker sees when mounted in the cabinet. The Linkwitz Dipole is not as pressed together as the Ridthaler Dipole, which is the main difference there and probably why Ridthaler could get a patent on it decades later.

The big difference between the three types is the sensitivity. Where as the Linkwitz and Ridthaler constructions have a low sensitivity, (The Ridthaler has about 77dB), the Kirchner experiences no loss in sensitivity due to cabinet mounting.

[john k...]

Here is my look at this.

[AJINFLA]

It isn't exactly sliced bread, is it?
May be tricky to XO to the mains too.

cheers,

AJ

[Rudolf]

Here is my look at this.

John,
did you actually build and measure such a "Dipole-Cardioid type woofer"?

There will be a shootout between Kirchners proposal and Ridtahlers Ripole in Germany. A member of the Monacor test and development team will build two cabinets - dimensioned by the rivals for the same driver - and measure them.
I will report the results in this place.

[dlr]

John,
did you actually build and measure such a "Dipole-Cardioid type woofer"?

Here's the first sentence from his page:

The above figures show the measured front and rear response from a "Dipole-Cardioid" type woofer and a typical H frame

I believe that the first drawing shows the actual dimensions as built, though he doesn't say that explicitly.

The last paragraph starts with:

To further verify the dipole behavior of the "Dipole-Cardioid" woofer the figure below shows phase of the front and rear radiation measured at the exit planes

Dave

[john k...]

John,
did you actually build and measure such a "Dipole-Cardioid type woofer"?

Hi Rudolf,

As drl pointed out, yes I build and measured the system, D-C against H frame. The results are basically exactly what I said they would be in my post, 13 above. The figures show the dimensions. The same driver was used, Peerless 12" SLS, for both. I really don't know why there is all this "panties up in a bunch" response over these different configurations.

Starting with a flat baffle and going from H to W to N to Ripole to D-C all that is changing is the loading of the front and rear sides of the driver. This may shift the dipole null slightly to the rear as the frequency increases and before SPL magnitude symmetry is lost, but cardioid? I don't think so. Of course it's only a name, not a radiation pattern.

If you make a symmetric enclosure like an N then you will have true dipole response with symmetric loading of the driver. With the N you can control the loading to increase Qts and decrease Fs, just as you can with a Ripole or D-C woofer. But if the front and rear loading are not the same asymmetries are introduced and the dipole behavior only exists at low frequency. What ever, symmetric or asymmetric loading, if the loading increases the effective air mass load on the driver, compared to free space, Fs will go down and Qts will increase. The higher Qts/lower Fs does increase output at low frequency (for obvious reasons).

[Rudolf]

John,
thanks for the clarification.
I couldn't quite believe that you would actually take the time to build a prototype of the Kirchner proposal.

I do completely follow your above explanation of the differencies between the diverse dipole configurations. So I too don't understand how Kirchners pretenses, which are not even backed by his own measurements, could make such a fuss here in Germany. :roll:

[john k...]

John,
thanks for the clarification.
I couldn't quite believe that you would actually take the time to build a prototype of the Kirchner proposal.

I do completely follow your above explanation of the differences between the diverse dipole configurations. So I too don't understand how Kirchners pretenses, which are not even backed by his own measurements, could make such a fuss here in Germany. :roll:

I had the H frame (screwed together) prototype hanging around. All I had to do was to cut a new baffle, a piece to block off the front chamber and screw the pieces back together.

Nothing in audio surprises me. Most people don't understand the physics so they believe what they read. There are numerous inaccuracies in the PDF as well.

[Leo K]

Hello John k,

thank you for testing the Dipol-Cardioid. You are very experienced in speaker.

Your measurements comparing the Dipol-Cardioid and H-frame do look fine. If you do use a speaker with the right parameters for the Dipol-Cardioid it will look better. The Qt of the speaker has to be 0.35 and the Fs 30Hz. The q of the mounted speaker will be 0.5. Then you get the best performance.

Best Regards

Leo K

[john k...]

Hello John k,

thank you for testing the Dipol-Cardioid. You are very experienced in speaker.

Your measurements comparing the Dipol-Cardioid and H-frame do look fine. If you do use a speaker with the right parameters for the Dipol-Cardioid it will look better. The Qt of the speaker has to be 0.35 and the Fs 30Hz. The q of the mounted speaker will be 0.5. Then you get the best performance.

Best Regards

Leo K

Well I would not find it so simple. Any driver will produce the same radiation pattern. What will change is the amplitude vs. frequency. And it is not simply a matter of Qts and Fs. More important is the moving mass of the driver. A driver with Qts = 0.35 and Fs = 30 Hz and a very heavy cone will not show a significant shift in Q or Fs. A driver with lighter cone will show greater shift.

The other thing I might add is that any time there is a loss of front to rear symmetry of the radiation pattern, that is, a moving of the nulls off the 90 degree position, it is a result the phase differences between front and rear not being 180 degrees. If the phase differences is 180 degrees but the front and rear amplitudes are different then the symmetry remains but the null at 90 degrees is shallower. For example, if the rear response is -3dB compared to the front but the phase differences is 180 degrees then the radiation pattern will remain symmetric but at 90 degrees the response will be -10db rather than complete cancellation.

[Leo K]

Hello

Here are more information fort he Dipol-Cardioid.

http://www.kirchner-elektronik.de/~kirchner/DIPOL-CARDIOIDeng.pdf

Best Regards

Leo K

[john k...]

So what ever happened to the "Shoot Out" between Ripole and "Dipole- Cardioid" :lol:

[Deward Hastings]

So what ever happened to the "Shoot Out" between Ripole and "Dipole- Cardioid" :lol:

You just had to, didn't you :rofl: (somehow I'd put it in the "that's settled, why bother" catagory . . .)

[Rudolf]

So what ever happened to the "Shoot Out" between Ripole and "Dipole- Cardioid" :lol:

It did not happen - yet.
The original 'volunteer' had reasons to withdraw his offer. And there has been no brave man to step in. Sort of ''you don't want to enter the lions cage just to entertain the crowd"

[john k...]

It did not happen - yet.
The original 'volunteer' had reasons to withdraw his offer. And there has been no brave man to step in. Sort of ''you don't want to enter the lions cage just to entertain the crowd"

Better to look a fool that to be proven to be a fool? ops:

[PhilDSP]

The other thing I might add is that any time there is a loss of front to rear symmetry of the radiation pattern, that is, a moving of the nulls off the 90 degree position, it is a result the phase differences between front and rear not being 180 degrees. If the phase differences is 180 degrees but the front and rear amplitudes are different then the symmetry remains but the null at 90 degrees is shallower. For example, if the rear response is -3dB compared to the front but the phase differences is 180 degrees then the radiation pattern will remain symmetric but at 90 degrees the response will be -10db rather than complete cancellation.

If you must have cardioid or even hyper-cardioid radiation pattern then you may want to consider a TL. I was recently very surprised on listening closely to my 3.6 meter long TL prototype. I haven't measured it yet (because my mike cables aren't long even to reach and the cabinet is so heavy I don't want to move it). But clearly at 90 degrees the back wave radiation from the side panels is greater than the amplitude of the refracted front wave of the system. But I'm sure that only occurs horizontally. The vertical radiation pattern is subject to the bends and folds of the channel and will not be cardioid in nature.

That allows the system to couple nicely with the room with no effective baffle step effects. But then I guess not everyone is willing to build such a monster and try to stuff it in your living room

[Face]

It did not happen - yet.
The original 'volunteer' had reasons to withdraw his offer. And there has been no brave man to step in. Sort of ''you don't want to enter the lions cage just to entertain the crowd"

Any update?

[DaveFred]

Any update?

How many years has it been?

Did the shoot out ever happen?

[DaveFred]

How many years has it been?

Did the shoot out ever happen?

I guess not...