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Old 15th October 2012, 11:19 AM   #401
Omholt is offline Omholt  Norway
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Thanks John.
Well, from this alone it's obvious that monopole is the better sub. Dipole/cardioid offers no real improvement and with less output. And they cost more as well.

I personally don't understand the word "pressurization". It's a term I have never heard used in acoustic circles. Can you explain further what you mean by it?
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Old 15th October 2012, 11:40 AM   #402
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Well.. in near-anechoic situations there should be no difference between a dipole and monopole. Or between a controlled and bad directivity for that matter ....

Pressurization: what I understand with this is that the speaker can generate a "static" sound pressure in the room, globally speaking.

A monopole can do this. A dipole can not since both + and - periods of the signal is released into the room.

No pressurization is perhaps the main reason dipoles are more neighbor-friendly than monopoles.
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Old 15th October 2012, 12:00 PM   #403
Elias is offline Elias  Finland
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Quote:
Originally Posted by john k... View Post
I'll post the impulse responses.
Great !

I can run similar modulation analysis as I did here:
Elias Pekonen Home Page - Dipole Bass vs Monopole Bass


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Originally Posted by john k... View Post
I don't listen to test signals. I have no idea what they are supposed to sound like.
Wow. But you should. It can be an eye opener.



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Originally Posted by john k... View Post
As far as music goes, you may recall that the original NaO II had a woofer system which could be mechanically and electrically converted between U-frame quasi-cardioid and sealed box, with identical free field response. The NaO II RS has only the U-frame cardioid. That should tell you something.
It may true that in your purpose built dedicated listening room cardioid performs well enough.

But how about those of us who live in a concrete boxes ? Maybe they wish for dipoles.



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Originally Posted by john k... View Post
Also, in this test I am not trying to find optimum position for the placement of the woofers. I'm interested in how they perform in a typical stereo speaker setup.
The bass reproduction in a typical stereo speaker setup has been may goal also ! Maybe I should have expressed that more clearly in the beginning of the thread, too.


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Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
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Old 15th October 2012, 12:03 PM   #404
Elias is offline Elias  Finland
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Yes and there are steel bars in front of the windows
The walls at my current place are about 70cm (2.3ft) thick.
Well, I dont have steel bars in the window, but my walls are 'only' 50cm thick brick and cement.

These walls don't have any of 'damping' properties... It's a whole new problem scenario.
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Old 15th October 2012, 12:05 PM   #405
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Well, I dont have steel bars in the window, but my walls are 'only' 50cm thick brick and cement.
Steel bars aren't needed for you guys up there, the weather wouldn't allow one to step outside anyways.
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Old 15th October 2012, 12:29 PM   #406
lolo is offline lolo  France
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wow.. 70cm walls! torture room?

my concrete box is "only" made of 25cm thick walls and I do have issues with two fairly large resonances below 80hz. I use dipoles. the funny thing is measurements did not show much difference with the speaker placed right on the corner, I thought it would cancel all modes..

more subjectively, aren't dipoles meant to give an edge on "natural" LF reproduction? less energy storage + less group delay compared to ported subs, and even closed boxes?

Last edited by lolo; 15th October 2012 at 12:44 PM.
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Old 15th October 2012, 01:24 PM   #407
Rudolf is offline Rudolf  Germany
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John,
your Arta burst decays may be good for detecting driver resonance issues, but they are inferior to Elias' methods when you want to see room dependent timing issues. You may compare my diagrams, which show the influence of some front wall absorption Wavelet CSD a better graphic representation of loudspeaker/room interaction?:
ani constQ wavelet 30.gif
In the above diagram you can clearly recognize the attenuated front wall reflection at 7 ms. This is much less visible in the Arta burst decay diagrams from the same IR measurements:
ani burst decay1 30.gif
ani burst decay2 30.gif
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Old 15th October 2012, 01:38 PM   #408
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50cm thick walls! The only homes like that in the UK are either at least 200years old or of the 'stately' type. Or both.

However, i once lived in a pre-fab concrete building, and whenever a bassist hit the B string open on a 5 string bass the room shook! Considering the speakers were only 5 inch audax, and f3 of the box was circa 55hz, this mode gave a useful boost. If a little hungover. The upper bass modes were far less noticable. The effect of concrete floor and walls was most objectionable in the midrange.

In that room i would never have used a dipole, whatever improvement could be realised in bass mode reduction was, to me, stolen away by the 'swimming pool' sound of the mids. Difficult rooms dont necessarily require a dipole solution alone, room treatment is almost certainly required. John K's listening room seems a logical approach to tame a concrete coffin
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Last edited by mondogenerator; 15th October 2012 at 01:44 PM.
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Old 15th October 2012, 02:25 PM   #409
lolo is offline lolo  France
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Originally Posted by mondogenerator View Post
In that room i would never have used a dipole, whatever improvement could be realised in bass mode reduction was, to me, stolen away by the 'swimming pool' sound of the mids. Difficult rooms dont necessarily require a dipole solution alone, room treatment is almost certainly required. John K's listening room seems a logical approach to tame a concrete coffin
you are right, anything above 90db becomes horrible. I am experimenting with bbc absorbing modules but don't have enough of them yet. and my furnishing is on the light side.. you also need EQ too, for sure! so it's definitely a more complex picture if you want to reach a really good level.
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Old 15th October 2012, 02:39 PM   #410
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Originally Posted by Omholt View Post
Thanks John.
Well, from this alone it's obvious that monopole is the better sub. Dipole/cardioid offers no real improvement and with less output. And they cost more as well.?
Well, if on graphs, dipoles look so similar to monopoles...how to they sound so different to many including SL, ? JohnK, ?Martin King. Not to mention the many successful commercial models which are dipoles.

It seems that the graphs by John are missing to capture something very deciding. However, the graphs by Elias told a different story more in sync with subjective perceptions. Even Dr. Geddes agrees that dipoles sound "different". Then why should the graphs look the same ??!!
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