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slow_hoe2001
05-13-2006, 07:32 PM
i made my first BIG box today and we put a huge port on it. when we fired it up the subs moved in instead of out. we checked the wiring and retried it. same thing. why does it do this? seems like the subs are bottoming out real easy. could the port be to big?

PowerNaudio
05-13-2006, 08:01 PM
have you tryed the subs free air, at low power to see if the same thing happens.
if the same thing happens you may have a bad amp, internaly the push pull configuration is not balanced and it pull to one side intead being at zero.

test it out before you kill your subs.

slow_hoe2001
05-13-2006, 08:10 PM
when the subs were in smalled sealed boxes they moved out, although not much. i was gonna try different things to see what kinda increase i can get from them. i have like 12 boards of mdf and a gutted neon so i figured i'd play a lil bit.

DarkFox
05-13-2006, 08:19 PM
considering the music is being played through the coil of the sub this should be observed...

A subwoofer is a fixed magnet with a coil in the middle of it.

The coil is supplied with power from the amp. Creating a Electro-magnetic field

The "Music" is a AC sine wave. Meaning that the polarity on the coil changes with every 1/2 cycle at any given freq.

If your sub only moves one way then you are giving it DC.

So end result is how do you figure it only moves in or out? If you are hearing sound then it is moving both ways. Maybe you are just seeing alot more of the excursion (sp?)

If you have a multi meter you can set it to DC Volts and parallel it to your sub. You should read 0 V dc, (or within a few hundred mV anyway.) If you hear music AND have a few volts DC then there is a problem with your amp, and from a electro-mechanical stand point it would be the equivilent of a AC sine wave riding a elivated DC signal. All in theroy of coarse. J/L

PowerNaudio
05-14-2006, 02:42 PM
if the sub is puting out sound but is pulling the sub in. its posible that the sub instead of playing in a push pull from zero is doing it from some thing like -3v or some thing of that sort thats why the sub pulls in and still plays music. if it was only getting a dc signal it would just pull to one side ither up or down. so if it pulls in but not all the way. the amp is out of balance internaly the dc offset is not set to 0 were it should be.

DarkFox
05-14-2006, 04:10 PM
If you hear music AND have a few volts DC then there is a problem with your amp, and from a electro-mechanical stand point it would be the equivilent of a AC sine wave riding a elivated DC signal.

So arnt me and you saying the same thing?