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Quad 63 (and later) Delay Line Inductors
Quad 63 (and later) Delay Line Inductors
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Old 12th June 2020, 10:44 PM   #261
bolserst is offline bolserst  United States
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Location: Fort Worth, Texas
Quote:
Originally Posted by Hans Polak View Post
O.k., got it, but does this apply to any of both systems
Each source model applies to any system that is emulating or behaving like it.
The ESL-63 theoretical starting point was to emulate the portion of the wave-front coming from a point source or pulsating sphere that would pass thru the diaphragm if it was placed 30cm behind diaphragm. The FrontRo theoretical starting point was to emulate the motion of the outer surface of an oscillating sphere. Both speakers use rings and delays, but the acoustic source that they behave like is different.

Quote:
Seeing the ESL63 as an pulsating sphere is not the first thing that comes to my mind.
One way to think about how the ESL63 emulates a portion of the wave-front from a pulsating sphere is to consider the ESL as acoustically transparent, like an open window. So, place a window the size of the ESL63 in an otherwise acoustically inert, infinitely sized wall. Now place a point source, or pulsating sphere source 30cm on the back side of the wall centered on the window, and you listen from the other side sitting your usual listening distance from the window. Next, stretch a very thin diaphragm across the window. Other than a very small roll off in the highs from the diaphragm mass(which can be compensated for) you would not notice any difference compared to the open window. Now, calculate the relative pressure and time delay across the window at the plain of the diaphragm. Knowing this, you could add stator rings and drive signal to move the diaphragm to re-create this same pressure field vs time across the whole window. Finally, remove the source behind the wall and turn on the power to the ESL.
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Old 12th June 2020, 11:13 PM   #262
bolserst is offline bolserst  United States
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Quote:
Originally Posted by Hans Polak View Post
Here is an initial LTSpice model that I have made for the FrontRo ESL.
Summing up currents for all the segments in your model and you get the Fig. 14 response from the AES paper. Nicely done
For grins, I took the currents from you model and applied them to rings to calculate the polar response.

Attachment #1: This is the traditional polar plot which matches Figure 13 from the AES paper.

Attachment #2: The polar response for the Hansí FrontRo model is shown in the 3 plots on the left side.
For comparison, the polar response for an ideal 2 inch diameter piston is shown on the right side.

Attachment #3: Because I know somebody would ask The polar response for the first 6 rings of Hansí ESL-63 model is shown in the 3 plots on the left side. For comparison, the polar response for just the center disk of the ESL-63 is shown on the right side. This basically tells us that the directivity of the whole ring system at high frequency is not that much different from that of just the inner disk, but it can play 15dB louder.
Attached Images
File Type: png Polar_FrontRo_Model_01.png (29.4 KB, 124 views)
File Type: png Polar_FrontRo_Model_02.png (349.6 KB, 106 views)
File Type: png Polar_ESL-63_Model_01.png (335.0 KB, 93 views)
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Old 13th June 2020, 12:47 AM   #263
martin clark is offline martin clark  Europe
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Quote:
Originally Posted by bolserst View Post
Each source model applies to any system that is emulating or behaving like it.
The ESL-63 theoretical starting point was to emulate the portion of the wave-front coming from a point source or pulsating sphere that would pass thru the diaphragm if it was placed 30cm behind diaphragm. The FrontRo theoretical starting point was to emulate the motion of the outer surface of an oscillating sphere. Both speakers use rings and delays, but the acoustic source that they behave like is different.


One way to think about how the ESL63 emulates a portion of the wave-front from a pulsating sphere is to consider the ESL as acoustically transparent, like an open window. So, place a window the size of the ESL63 in an otherwise acoustically inert, infinitely sized wall. Now place a point source, or pulsating sphere source 30cm on the back side of the wall centered on the window, and you listen from the other side sitting your usual listening distance from the window. Next, stretch a very thin diaphragm across the window. Other than a very small roll off in the highs from the diaphragm mass(which can be compensated for) you would not notice any difference compared to the open window. Now, calculate the relative pressure and time delay across the window at the plain of the diaphragm. Knowing this, you could add stator rings and drive signal to move the diaphragm to re-create this same pressure field vs time across the whole window. Finally, remove the source behind the wall and turn on the power to the ESL.

Cogent & elegant description!
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Old 13th June 2020, 08:31 AM   #264
esl 63 is offline esl 63
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Imagine this speaker been developed in the 60-70ties.
Walker did some speaches at AES and got standing ovations.
Wish i had been there..
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Old 16th June 2020, 05:01 PM   #265
Hans Polak is offline Hans Polak  Netherlands
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With Steve Bolser's and Demian's fantastic support, I could bring my LTSpice model to an end.
After having added all currents, currents that are directly proportional to the produced SPL, I added all the necessary acoustic corrections.
First image below shows in blue the sum of all currents and the red curve shows the end result after having applied the various corrections, such as:
Membrane resonance at 50Hz, Proximity effect a 1 m distance, Baffle effect and stator transparency.

Second image shows an acoustic recording with om the top the final result from LTSpice.
Be aware that all this applies only to the on axis response.

Hans
Attached Images
File Type: jpg Final_Sim.jpg (514.7 KB, 70 views)
File Type: jpg Corrected_FR.jpg (387.2 KB, 75 views)
Attached Files
File Type: asc FR Definitief Steve.asc (14.9 KB, 12 views)
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