Sub Problem

[ethanfitz]

Hey guys,
im having a problem with the Active sub I have installed...

It was working fine for almost a year then recently (after some mechanics had been poking about in my boot looking for the locking wheel nut key) it has stopped working properly...

my problem:
The sub works great when the ignition is on, sounds exactly as it always has and should. However as soon as I turn the engine on it isn't thumping as loud at all to the point where I think it isn't on at some points...
I have checked the connections, fuses and dials (encase any where knocked by the mechanics) but it is still happening... the power light is always on and there is sound coming from the sub when the engine is on, it is just not as powerful, clear or as accurate as it is with the engine off...

Any one have any ideas what could be wrong/where to look?

thanks in advance...

 

[coachwhip]

Sounds like an earth or battery problem. What sort of power is the sub, check the fuses in the amp itself, they will give an idea of the actual power output.
Do you have decent wiring on the power and earth side of the sub.
With the ignition off then you'll normally have around 11.5 volts and running around 13.5 volts.

 

[ethanfitz]

Thanks for the advice,

i have had a poke around today and.... i still cant get it to work :-(

My battery gives me 12v with ignition and then 14v with the engine on. so i assume my battery is fine...
I have checked and replaced the 2 fuses on the live wire to the sub (just in case), i have cleaned up and re-seated the earth wire as well...

I have checked voltages going to the sub (the connection before it enters the sub) both with ignition and with the engine running, and all is as it should be (12v on ignition 14v with engine running), the same comes up when connecting across to the ground point with everything connected so i can only assume it is getting the right power and my ground is fine also...

to make sure i checked voltages + resistances and continuity across all bits going into and out of the sub that i could everything is reading as it should (as far as i can tell) but im still getting the same issue...

Sub works fine with ignition on but as soon as i switch the engine on it doesn't work... any one have any more ideas on where to look or do you think it is a fault in the amp bit of the active sub?

 

[coachwhip]

I'd be tempted to say it's the amp. Something wrong internally that doesn't like the extra volts.
Though the fact that it didn't go wrong till the mechanics looked in boot trends to point towards wiring.
What sizes are the fuses just out of interest.what wires go to sub.

 

[ethanfitz]

sorry for the late reply... thought i got it working again but took it for a drive and nope :-(

this is the sub i have that is causing the issue:
http://www.ebay.co.uk/itm/201048437947?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

(i was only £70 when i brought it!)

annoyingly i have had it for a year and a half not so outside of its warranty...

fuse wise there is a 30amp on on the wire near the battery and a 10amp one on the back of the sub itself...

dam thing it pretty annoying now :evil:

 

[coachwhip]

I'd think it's the circuit inside the amp. It's a fairly low spec unit as evidenced by the 10 amp fuse on the amp.
I'd be tempted to look for a small sub in box and separate amp. Though do some searching around, eBay or Gumtree. You can pick up cheap old stuff that will work well. Don't go on the Max watts figure. The cheaply made stuff will have high figures but not actually come anywhere near.

 

[ethanfitz]

Yep defiantly the amp... i noticed it was going into protection mode all the time, even when it was working on the ignition the protection light was still on, it was also still on when i disconnected the sub inside (i followed a trouble shooting guide)... weird... anyway i hooked up my friends active sub and that worked fine both on ignition and with the engine on (as it should) so guess my amp is shot... time to start hunting e-bay etc...

one more question... bit of a noob one maybe but...

it can be hard to exactally match the rms of an amp to that of a sub (at the same ohms)... so is it best to have a slightly under powered amp, eg amp outputs 300 watts rms at 4ohm and the sub is 350watts rms at 4ohms ... or is it better the other way round eg amp outpur 500watts rms and sub is 350watts ... just some examples from a few combinations i have looked at...

 

[lusid666]

With Pro gear the rule of thumb is to have speakers rated about 25% higher than the amp so you have some headroom if theres a spike in volume.

 

[ethanfitz]

ok thanks so it would be better to get a slightly under powered amp then, and the example i gave: "eg amp outputs 300 watts rms at 4ohm and the sub is 350watts rms at 4ohms" would probably be about perfect? thanks for the help :grin: