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Multi-Way Conventional loudspeakers with crossovers

D 54 AF
D 54 AF
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Old 18th May 2018, 12:13 PM   #1
guidobullo is offline guidobullo  Italy
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Question D 54 AF

Hello everyone
what I ask and to know if the Le of the D54AF is equal to 0.2 as I would like to add the relative Zobel.
it seems unlikely that it is measured at 10Khz when the answer does not exceed 6 Khz, undoubtedly it is an error, so I ask you what its true value is.
the second question is to know what the exact formula for calculating zobel is.
some say that the king must be equal to the resistance to be included in the zobel, others say it must be superior.
can you give me the appropriate information?
thanks and bye
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Old 18th May 2018, 02:35 PM   #2
TMM is offline TMM  Australia
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The datasheet is showing Z=16ohm at 10kHz therefore if Re=4.5ohm, Le=16-4.5=11.5ohm
11.5/(2*pi*10K) = 0.18mH

You can also do it for other frequencies by looking up the impedance on the plot and calculating Le again. At 5kHz you get 0.09mH and at 20kHz you get 0.32mH. This is because the inductive part of the impedance is not an ideal inductor, it's lossy. Because of this there is no 'perfect' zobel, simply one that it makes the impedance flattest through a certain range of frequencies that is up to you to choose.

I would sim the zobel in a crossover simulator like XSim loaded with the measured driver impedance. Start with R=Re, C=0.1uF. Increase C until the impedance becomes flat through a useful range of frequencies (e.g. 1-5kHz for the D54). If the resulting impedance becomes too low for your liking then increase R and adjust C again.

Last edited by TMM; 18th May 2018 at 02:41 PM.
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Old 19th May 2018, 03:48 PM   #3
guidobullo is offline guidobullo  Italy
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The datasheet is showing Z=16ohm

Z= 8ohm!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!
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Old 19th May 2018, 05:34 PM   #4
raymondj is offline raymondj  United Kingdom
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Hi,

After reading TMM's reply I would humbly suggest TMM has offered correct and valid information. The spec sheet gives Z as 8 Ohms, however if you look at the frequency impedance chart you provided the Z at 10Khz is in fact 16 ohms.

TMM has then shown his calculations and provided what the calculated LE is at a few frequencies.
You can apply the same calculation for the le at 6Khz if that is your design crossover frequency. His further advice is practical if you use a crossover simulator where you can model the effect of differing C's and R to give a flat impedance response.

Last edited by raymondj; 19th May 2018 at 05:37 PM. Reason: Used the term frequency instead of impedance
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Old 19th May 2018, 06:02 PM   #5
Scottmoose is offline Scottmoose  United Kingdom
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Quote:
Originally Posted by guidobullo View Post
The datasheet is showing Z=16ohm

Z= 8ohm!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!
Look again. Impedance curve traced in green. 16ohm level in pink. The impedance at 10KHz circled in blue is 16ohms, as TMM said.
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