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woofer inductance
woofer inductance
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Old 6th April 2008, 12:51 AM   #1
lolojr1 is offline lolojr1  United States
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Default woofer inductance

not sure if this should be in the amp or caraudio section i will move it if it is in the wrong place

can there be any adverse effects to running 36 exactly the same brand new woofers on one class d amp?

the impedance was just over the rated 1ohm measured at 1.1 ohm and the input voltage never dropped below 14 volts

9 groups of single 4 ohm wired to 4 ohms and then paralleled to just over 1 ohm total

i spoke with the manufacturer of the woofers and he told me about an inductance problem that might/will happen from this

2 of the mosfets completely melted right off of the heatsink

all of the woofers were checked and double checked for shorts and phase they all move the same direction

im curious now because my line array will get finished soon and i have 36 mids per channel and i dont want to do the same to my amp
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Old 6th April 2008, 10:59 AM   #2
95Honda is offline 95Honda  Germany
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Inductance will lower with drivers in parallel and increase when they are in series. If you are doing series/parallel or just parallel then no problem. You would get a lot of inductance if you wired a whole bunch in series, but you would also get very high impedance....
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Old 6th April 2008, 11:39 AM   #3
PeteMcK is offline PeteMcK
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?
4/9= 0.444
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 6th April 2008, 12:43 PM   #4
AndrewT is offline AndrewT  Scotland
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I'm not sure what "9 groups of single 4" means, but I think Pete is on the track with 4/9 giving an impedance very much lower than 1ohm.
Why on earth aim for 1ohm when 4ohm or 8ohm works perfectly well?
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Old 6th April 2008, 02:30 PM   #5
lolojr1 is offline lolojr1  United States
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sorry let me clarify

every 3 are series up to 12 ohms

then there are 12 groups of 3 paralleled back down to 1 ohm

my mistake i was remembering alot of different wiring configurations and that one stuck in my head fr some reason


the reason to use 1 ohm is that is where this amplifier is rated to be used at
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Old 6th April 2008, 03:05 PM   #6
AndrewT is offline AndrewT  Scotland
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the amp manufacturer is telling fibs.
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Old 6th April 2008, 03:13 PM   #7
ßart West-VL. is offline ßart West-VL.  Belgium
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Quote:
Originally posted by AndrewT
the amp manufacturer is telling fibs.
I didn't know what "fibs" meant.. now I do:
http://www.urbandictionary.com/define.php?term=Fibs

Thanks Andrew, I needed that.
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Old 6th April 2008, 03:13 PM   #8
tinitus is offline tinitus  Europe
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woofer inductance
A 4ohm driver may only be 3ohm dc

High sensitivity might help on using a classD fore low impedance drive, but you may actually not achieve high sensitivity at all
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Old 6th April 2008, 03:28 PM   #9
lolojr1 is offline lolojr1  United States
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Quote:
Originally posted by AndrewT
the amp manufacturer is telling fibs.
actually this is one of those crazy low impedance amplifiers it has been wired to .25 ohm and worked fine but that wasn't on 36 woofers it was 2
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Old 10th April 2008, 12:10 AM   #10
lolojr1 is offline lolojr1  United States
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anyone have any idea what this could do to an amplifier?

is this the same as a line array with a final impedance of (?) can this damage an amplifier
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