woofer inductance

lolojr1

Member
2004-10-03 5:20 am
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
 

lolojr1

Member
2004-10-03 5:20 am
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
 
That is what I'm trying to get at, with you wiring at 1 or 4 ohms, you are doing a series/parellel arrangement and you won't have to worry about high inductance.

If you wired them all in series, you may have a problem, but I don't think you are going to be doing that.

I would be more worried about a 1 ohm load than the inductance. That low of a load is harder on the amp, cuts the dampening factor and generally makes things run less efficient....

I'd shoot for 4 ohms or higher....
 

lolojr1

Member
2004-10-03 5:20 am
ok well a higher load can be had not a problem but it seems to be a problem because he( i got asked how to fix this somehow) has blown a second amplifier today except this one costs around 750-1000 the first amplifier was having some problems before being hooked up to this setup

will the dampening factor play a big factor in this setup? could it just be that keeping 36 colis in check is too much for any amp?

after seeing this im kinda scared to hook my line array up and do any serious testing/listening because it has 36 drivers per side also although i have my line array wired to the same impedance of one driver ...4ohm

my response is to sell the one big amp and move to more 3,4,6 or 9 amps to distribute the load a bit

i have spoke with a few other people about this and they think low damping factor might be a problem and i have heard inductance ,back emf, enclosure loading and its just plain too much to handle
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
lolojr1 said:


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


That puzzles me...how on earth do you achive 0.25ohm with only 2 woofers
:confused:

Something tells me that you may have to calculate your impedance more carefully...remember that a 4ohm driver may only be 3ohm dc...could mean a lot of differense with that many drivers
 
To lolojr1 :

Did you check the DC impedance with a multimeter ? If you keep blowing amplifiers, there's maybe a short somewhere. It would only take one faulty woofer or wire on 36 to blow the amplifier.

Good luck !

As others said, there's no problem at all with 36 drivers, if you're blowing amplifiers, problem is somewhere else.
 

lolojr1

Member
2004-10-03 5:20 am
ok to answer the last few questions, but i haven't got a chance to get over to his house and do any testing or more investigating sorry i had to work late.

yes it is possible to achieve .25 ohm per amp dual .5 ohm coils or like simon5 said quad 1 ohm but this amplifier is capabile of low loads it has been used where 2 amplifiers were strapped to one .5 ohm coil.....and had 4 amplifiers per sub to a final load of .25 ohm per amp this is actually quite common in competition sub woofers and amplifiers.

Now not by any means is this optimal for quality or safety but to get every last bit of juice out of an amp thats what they do ?????

i can show pictures or diagrams if it helps but that was just a reference to show that that particular amp can handle a load lower than the one it was at when it was lost.

in this particular setup it was not ran that way the load which was not just calculated but measured with a meter to 1.1ohm final

the first amp lost to this was used like in the above refrence for a whole season of competition without a hiccup as far as i know.

there is no short that has been checked and rechecked now a few times and i have been witness to this on more than one occasion

the speakers are all in phase and move exactly the same with 16 vdc from the battery applied to check phase in both directions

although when playing music they all move differently im going to try a test tone at different frequency when i run the woofer tester this weekend

i am thinking that the pressure built up in the cabin/box is too much work for one amp to overcome

there are 9 woofers each in a sealed common chamber and 4 separate sealed chambers

i know caraudio gets frowned upon around here because of the strange questions and this is absolutey one of those but after years of reading and toying around with this stuff i have never seen this and figured the best place for answerers was diyaudio and its great minds