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B&C 21SW152 clone
B&C 21SW152 clone
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Old 26th June 2019, 03:08 PM   #31
Crashpc is offline Crashpc  Czech Republic
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Okay, came from Hornresp sims. I did not input favourable parameters for 21DS115 against 21SW152 at all. The "measureable difference" only ocurs from 85 Hz up, within 1db still at 100Hz.
The 21DS115 still wins over 21SW152 on sensitivity, motor force and efficiency. (Bassreflex box 160l @ 30Hz). I cannot see any opposite data at this moment.
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Old 26th June 2019, 04:09 PM   #32
Brian Steele is offline Brian Steele  Grenada
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Originally Posted by Crashpc View Post
Okay, came from Hornresp sims. I did not input favourable parameters for 21DS115 against 21SW152 at all. The "measureable difference" only ocurs from 85 Hz up, within 1db still at 100Hz.
The 21DS115 still wins over 21SW152 on sensitivity, motor force and efficiency. (Bassreflex box 160l @ 30Hz). I cannot see any opposite data at this moment.
Did you use semi-inductance parameters in your sim?
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Old 26th June 2019, 04:13 PM   #33
Brian Steele is offline Brian Steele  Grenada
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Originally Posted by Matthew Morgan J View Post
Brian (and team?) has since taken things a step further by developing the Semi-Inductance method (snip)
I certainly didn't develop it, LOL. Guys with a lot more working brain-cells than I have did that . Knud Thorborg and Claus Futtrup wrote the paper, and Stephen Bolser (who has a thread going here on the subject) developed a spreadsheet that can be used to derive the parameters.

More info here: The Subwoofer DIY Page - Semi-Inductance
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Old 26th June 2019, 04:17 PM   #34
Brian Steele is offline Brian Steele  Grenada
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Originally Posted by Brian Steele View Post
See attached. The red line shows how the inductance of the 21SW152 varies with frequency (based on extracted impedance data from its published impedance curve).
..and here's the curve for the 21DS115. The inductance is significantly higher than that of the 21SW152 at lower frequencies.
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File Type: png 2019-06-26 (3).png (21.5 KB, 93 views)
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Old 26th June 2019, 04:24 PM   #35
Crashpc is offline Crashpc  Czech Republic
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Brian Steele: Yes. I used semi inductance parameters. Compared 21DS115 with 21SW152. 21DS115 was affected more, but basically, it didnīt do much to the simulation, which would push one to consider that 21DS115 is less efficient or has weaker motor.
I certainly do not disagree on the presence of inductance. But its effects on efficiency are not significant enough. Or at the moment it seem to not be the case.
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Old 26th June 2019, 05:55 PM   #36
Josh Ricci is offline Josh Ricci  United States
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Originally Posted by Brian Steele View Post
I certainly didn't develop it, LOL. Guys with a lot more working brain-cells than I have did that . Knud Thorborg and Claus Futtrup wrote the paper, and Stephen Bolser (who has a thread going here on the subject) developed a spreadsheet that can be used to derive the parameters.

More info here: The Subwoofer DIY Page - Semi-Inductance
Correct...This goes way back many many years. Thankfully with Bolserst's hard work on the spreadsheet, David's inclusion into HR of the semi-inductance model and modern measurement gear or curve fitting apps, we now have free tools available and useful for the hobbyist DIYer.

Note this is a much different thing than the lossy inductance check box in HR that was developed a few years ago as a generic approximation for any driver. This was better than nothing but using the derived semi inductance specs is far more accurate. Also there is no cut-off point where a driver should use the lossy Le function and another should not, like I saw suggested earlier. The driver that is the subject of this thread has a shorting ring employed and there is nothing in the specs or impedance curve that suggests the inductance is significantly different than other drivers with similar specs. If in doubt use the spreadsheet and a derived impedance curve to do a HR comparison. It's not a clone of another driver either.

Also comparing drivers based on inductance / semi inductance alone as a modifier of motor force isn't very useful. Doesn't matter whether it's from Bolserst's spreadsheet or not. Actually motor force compared in a vacuum isn't very useful either.
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Old 27th June 2019, 05:15 AM   #37
Matthew Morgan J is offline Matthew Morgan J  United States
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Sorry about that, my mistake ....

Brian has done such a great job with other useful spreadsheets that i thought he might have had a part in this one too ..


I need to read more about the semi-inductance method..... Currently i am only just familiar with the "Lossy Le" feature/formula and what it implies about how relative inductance can influence real world motor force ..
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