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Old 29th July 2012, 08:56 PM   #11
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Hi,

I'm not a scientific but i know that what you describe is relative to open space measures of hp, so that reflected waves cannot go back to polluate the results.

The in-room listening has nothing to deal with open air measures. In a room, there is plenty of reflected waves that you cannot completely kill, - even by room-treatments, - even in putting the hp in a close box, because the reflected inside sounds go outside through the membrane of your hp.

In a room, the cancellation of dipoles hp is tremendously lowered. But the theory cannot set up exact formulation of this lowering, because all situations depend on the dimensions of the room. And if the idea of a normalised room could be accepted to find the equations, they could not be be applicable in a not normalised room.
The adaptation of a hp system to a specific room to get a good sound holds on being made by experience and hearing, instead of application of scientific formulas.

Scientific specialists prefer to repeat that cancellation make dipole hp not work.
Too easy !

They did not know it was impossible, they made it...
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Old 29th July 2012, 11:32 PM   #12
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Hi,

To be more precise, we must know that cancellation does not appear in every point of the space around the dipole. It appears only when front and rear waves meet, having made exactly the same distance, that is to say where we commonly install baffles. Elsewhere, cancellation doesnot appear so strong and decreases rapidly. Specially in front of the dipole, there cannot be cancelletion because the distance between front and rear surface of the membrane is maximum : rear vibration cannot reach front one. Too much advance.

So,the phenomenon is not so important when you consider the whole space around the dipole in open air.

In a listening room, because of wall reflexion, there is a general mix that nobody can describe and thus, measure or predict... Every where, there is points of pression and points of depression. Be carefull to where you put your microphone to measure ! 10 cm aside, you get a completely different result. This is why positionning HP in a music room is a question of listening and expertise by experimented installators, not scientifics professors.
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Old 30th July 2012, 12:23 AM   #13
Remlab is offline Remlab  United States
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You will have a 6db roll off starting at 266 hz. That means it will need 24 db of compensation at around 17 hz just to stay flat, relative to 266 hz. There is no way it could be 93 db efficient in the low frequencies..

Last edited by Remlab; 30th July 2012 at 12:25 AM.
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Old 30th July 2012, 12:54 AM   #14
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Quote:
Originally Posted by Remlab View Post
You will have a 6db roll off starting at 266 hz. That means it will need 24 db of compensation at around 17 hz just to stay flat, relative to 266 hz. There is no way it could be 93 db efficient in the low frequencies..
You can see the response curve published on the Infraplanar website.
The only thing i can say is : this roll off does not appear.
You can read the following affirmation , as I do :

"Courbe de réponse en proximité, hors influence du local, micro à 3 cm de la membrane ;
mesures faites avec STEPS (ARTA) + carte son Edirol UA 25 EX + micro Audiomatica MIC-01 : On voit que la linéarité est très bonne et très étendue dans le grave. Avec des niveaux de puissance efficace de l’ordre de 5 Watts seulement, les niveaux sonores atteints sont très impressionnants et génèrent une écoute tout à fait réaliste."

.... "You will have a 6db roll off starting at 266 hz". Sorry, we don't have....
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Old 30th July 2012, 09:49 AM   #15
Remlab is offline Remlab  United States
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Quote:
Originally Posted by Tiburce2 View Post
You can see the response curve published on the Infraplanar website.
The only thing i can say is : this roll off does not appear.
You can read the following affirmation , as I do :

"Courbe de réponse en proximité, hors influence du local, micro à 3 cm de la membrane ;
mesures faites avec STEPS (ARTA) + carte son Edirol UA 25 EX + micro Audiomatica MIC-01 : On voit que la linéarité est très bonne et très étendue dans le grave. Avec des niveaux de puissance efficace de l’ordre de 5 Watts seulement, les niveaux sonores atteints sont très impressionnants et génèrent une écoute tout à fait réaliste."

.... "You will have a 6db roll off starting at 266 hz". Sorry, we don't have....
To clarify, I meant 6 db per octave. Sorry about that.
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Old 30th July 2012, 10:05 AM   #16
Remlab is offline Remlab  United States
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Measurements..
infraplanar

Google chrome will translate it..
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Old 30th July 2012, 10:13 AM   #17
SY is offline SY  United States
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Microphone is placed 3cm from the diaphragm for those measurements? No wonder the cancellation doesn't show up.
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Old 30th July 2012, 11:08 AM   #18
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Originally Posted by SY View Post
Microphone is placed 3cm from the diaphragm for those measurements? No wonder the cancellation doesn't show up.
True. See adress infraplanar

You can see in the chapter : EFFICACITE a curve taken in open space, the micro in axe at one meter.

Where is the roll-off from 266 Hz to 10 Hz ?
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Old 30th July 2012, 11:16 AM   #19
SY is offline SY  United States
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Quote:
Originally Posted by Tiburce2 View Post
You can see in the chapter : EFFICACITE a curve taken in open space...
Open space? No wonder the cancellation doesn't show up.
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Old 30th July 2012, 11:24 AM   #20
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You can see also that the efficiency is in open space above 90dB from 15Hz to 900Hz and maxi 98dB at 150Hz.

In a music room, you can expect 95 to 97 dB as mean value.
Not exactly "low efficiency" !
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