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Old 29th January 2013, 05:31 PM   #31
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Quote:
Originally Posted by kees52 View Post
Do you now this? I did found it just when googling.

http://www.kirchner-elektronik.de/~k...ARDIOIDeng.pdf

Hmm old topic, but not a problem I hope.
I looked at this a long time ago, when it was first published. Here is the result of my investigation: dipole_cardioid_woofer

One problem I had was that they indicated a -18dB null at 90 degrees and at the same time 3dB low SPL at the rear. The thing is that to have an -18db null the difference between front and rear SPL would have to be on the order of only 1dB.

The other issue that I have more recently begun to recognize is that whether it be dipole, cardioid or other, the free field response at low frequency is not relevant in a room. In a room these types of sources all reduce to multiple monopoles with different position and phase. The only real difference between dipole woofers and distributed monopoles in a room is that the dipole sources have a net zero volume displacement and can not excite the DC mode.

You can only reinvent the wheel so many time before someone start to catch on.
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Old 29th January 2013, 05:55 PM   #32
kees52 is offline kees52  Netherlands
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Hi John

The article in pdf the inventers give as idea that the efficientie is a lot better with this kind of box, I do not now afcourse I have never test it, os as I did read it is a problem to get the back and front of the speaker isolated,, so a wave can not traffel there and cancel low frequenties, oke, these guys say why not mass load the conus and give sound velocity a push and the wave need more time to get to the front of the speaker.

Did you build the one on your picture? not the double one I did drawn.

The wheel, wel no need for re-invention, but maybe I can let it better rolling.

I do always re-invent te wheel with the audio amps, old idea,s are populair these days, like single ended, and such.

thanks for your link, I go read it. Maybe a better way for cardioid is the use of a delay line (bessel allpass will do perfectly) and a extra speaker..
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Old 29th January 2013, 08:01 PM   #33
puppet is offline puppet  United States
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Quote:
Originally Posted by kees52 View Post
Maybe a better way for cardioid is the use of a delay line (bessel allpass will do perfectly) and a extra speaker..
Small gradient arrays are done much this way. Varying the delay between both woofers alters the cardioid pattern ... fine at lower frequencies. Pattern will still deteriorate as frequencies rise .. this mostly dictated by element spacing.

* Should include that steering woofer would have its phase inverted as well as delay applied.

Last edited by puppet; 29th January 2013 at 08:27 PM.
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Old 29th January 2013, 10:00 PM   #34
kees52 is offline kees52  Netherlands
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Originally Posted by puppet View Post
* Should include that steering woofer would have its phase inverted as well as delay applied.
Yes you are right 180 degree.

For a sub between 20 and 120 hz the delayline is fine, like a bessel who is fase consisted for a couple of octaves.

But I go not make that, room invloence is to big, open field yes that is fine.

I want try this very soon, I have use 1 x Sd for front and 1/3 for both rear openings.

have a good evening/day.
Attached Images
File Type: jpg dipole-cardioid.jpg (151.9 KB, 498 views)
File Type: jpg dipole-cardioid-front.jpg (64.0 KB, 493 views)
File Type: jpg dipole-cardioid-rear.jpg (80.6 KB, 476 views)

Last edited by kees52; 29th January 2013 at 10:04 PM.
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Old 30th January 2013, 03:05 AM   #35
puppet is offline puppet  United States
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http://www.electrovoice.com/sitefile...s%20v04%20.pdf
While this document is mostly prosound related there is some good insight regarding subwoofers.
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Old 30th January 2013, 12:19 PM   #36
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by puppet View Post
http://www.electrovoice.com/sitefile...s%20v04%20.pdf
While this document is mostly prosound related there is some good insight regarding subwoofers.
Thanks very interesting article, I try some thi some time, I make a electronic (bessel alpass with opamps) and a 180 degree fase shifter, this is not difficult, and try with two closed boxes back to back, I only need twice as much bass amps, or only one for mono, but music is also stereo in the low tones I have heard?

I want try first the box I drawn, this is from a german guy but it is not really further developed? it is not for the cardioid wich is difficult in normal room but efficienty of this box is higher says the developer that is interesting.

regards
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Old 1st February 2013, 05:07 PM   #37
kees52 is offline kees52  Netherlands
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Hi All

I have made the box, I have still need measurements and I let now, for the sound, it give pretty good bass, also low end, and it is louder then the dipole/ripole.

here some pics.
Attached Images
File Type: jpg Afbeelding 015-2.JPG (427.4 KB, 375 views)
File Type: jpg Afbeelding 016-1.JPG (430.7 KB, 361 views)
File Type: jpg Afbeelding 017-1.JPG (492.5 KB, 75 views)
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Old 1st February 2013, 05:11 PM   #38
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Quote:
Originally Posted by john k... View Post
The other issue that I have more recently begun to recognize is that whether it be dipole, cardioid or other, the free field response at low frequency is not relevant in a room.
...unless you're in the near field.
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Old 1st February 2013, 05:20 PM   #39
kees52 is offline kees52  Netherlands
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Originally Posted by markus76 View Post
...unless you're in the near field.
For me cardioid is not my search, but more efficienty, and near field, tja, in a home it is not a theatre, only big audient places needs cardioid because it give more efficienty because it is more directed to the front..

If i want cardioid then I put me head in the box, then I have a true cardioid, or I make a horn, the best cardioid ever.

But serieus, this thing here sound very well, I go make a bigger one where the part of the box where the magnets are has a volume who is also needed when I have a closed one, or a basreflex one and front of speakers still mass loaded.

I have need a shelf filter for the dipoles, for this one I have more bass, it is punchy and no need for the shelf filter anymore, or maybe very little correction nut first measurements.
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Old 1st February 2013, 06:43 PM   #40
tvrgeek is offline tvrgeek  United States
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If bass is "punchy" or not is usually a midrange property. That darn Fourier stuff again. You of course have selected superb mid-range armament. My experience is bass is a matter of managing the peaks and distortion. Are you expecting some sort of un-equal phase cancellation front to back modifying the radiation pattern? Please enlighten me here.
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