shrykhar

I'm running a Kicker Comp 12" sub and a Rockford Fosgate P450.4 4 channel amp in my RSX. I'm trying to bridge the rear channels to run the sub, and it works fine for a few minutes before the amp starts going in and out of protect mode. The amp is still cold to the touch, and the thermal light is not on, so I don't think it's a heat issue. The sub and amp work fine if I run it off a single channel instead of bridging 2 channels, but the sound is boomy and not punchy this way. Does anyone have any suggestions?

Some more info:
Kicker Comp 12" sub
power range 30-150 watts RMS
peak power handling 300 watts
The manual lists the Revc as 3.76 ohms. The correct Revc is 3.79 ohms.

The sub was in my gf's car, and she took it out when it stopped working. She wasn't sure if the amp or sub was broken, and never found out before she sold the car (without the sub). Does it matter if the sub's resistance isn't exactly 4 ohms?

Rockford Fosgate P450.4
» 4-channel car amplifier
» 60 watts RMS x 4 at 4 ohms (110 watts RMS x 4 at 2 ohms)
» 225 watts RMS x 2 in bridged mode (4-ohm stable in bridged mode)

The amp is new, and was recently installed in my car using a KnuKonceptz 4 gauge wiring kit. It is grounded to a sanded contact point behind the back seat, and I'm running a 2 foot long 12 gauge speaker cable to the sub. I tapped the white wire on the Bose sub harness for the amp remote on signal.

I'm also running a Kenwood X889 head unit, with the amp connected to the pre-outs. Only the sub is connected to the amp.

daicacharco

just go buy another amp -_-''

shrykhar

Uh, thanks for your constructive input?

MightySemen

Umm... Your amp is blown.. Happens when Subs are bridged it puts more stress on the amp and causes it to burn out. Take OFF the bridge ASAP and have individual wiring going to each sub. I found this out the first time I blew my amp I was HEATED lol.. And make sure not to go skimp on your amp... brand new with as long as a warranty as possible would be what you want this time around.

MightySemen

Err... I retract my previous statement... It might not be blown but if you keep it bridged it will blow out... I'm so lost, after re-reading.. you have 1 sub and 1 amp? what/why are you bridging?

shrykhar

I'm bridging rear channels to power the sub. Spec sheet says 225W RMS 4 ohm bridged, should be enough to power the sub, 30-150W RMS 4 ohms. It works for a few minutes, then it starts going into and out of protect mode. Same thing happens when I bridge the front channels.

mercman

You have one of the following problems,
1 Your sub is less the 4 ohms.
2 You are starving the amp due to a bad ground, power lead or low voltage.
3 Your amp has an internal problem.
4 A short due to a bad speaker connection.

Do this,
Switch the amp to 4 ch mode and disconnect the sub, play the amp and see if it shuts down. If it shuts down see problems 2, 3 or 4.

If it is ok then switch the amp back to 4 ch mode and connect the sub to just one of the rear channels. Play the amp and see if it shuts down, if it is ok then move the sub to the other rear channel and repeat the test. If the amp runs good to the sub in 4 ch mode then see problems 1,

If the amp shuts down in 4 ch mode (with the sub connected to only one channel) then check the voltage at the amp under load, and inspect the speaker wires. Problems 2 and 4.

Overall I suspect 1 or 2.

jeff

xtremelyslammed

is the speaker single voice coil or dual? if it is dual, you want to make sure you are wired up correctly inside the box to be running at 4 ohms ( wiring depends on dual 8 ohm voice coils, single 4 ohm voice coil, a bunch of possibilities)

junktionfet

...And make sure there isn't something simple like a single tiny strand of copper touching ground or shorting the output terminals at the amp or the speaker.

G22_Powered_YA1

Kicker is g*y and doesnt list whether its SVC or DVCs............. but on the pics at crutchfield I saw that it had a set of teminals on either side of the basket............ typical of DVCs, so id say its running 2 ohms and is overdrawing from the amp thats not 2 ohm stable at bridged setup, fact is that protect circuit is saving it as we speak, rewire your system and maybe buy another amp that IS 2 ohm stable (monoblock for this application), because at 8 ohms an average 4 channel just cant deliver

shrykhar

It's SVC. I busted out the multimeter and it registered 4.2 ohms. It seems to play fine bridged if I keep the gain down, and I might have turned it a bit high to match the funky setup I have with the front speakers and stock amp. Thanks for the help guys.

mercman

The DVM will only indicate the DC resistance of voice coil. What you need to know is the speaker’s impedance (not the same as resistance). It should be stamped on the speaker and it is important to know what it is so you don’t damage your amp.

jeff

shrykhar

It did say 4 ohms on the bottom after I finally unscrewed it from the box. I wonder why it's not published anywhere ...

shrykhar

Okay, it's either the amp or my wiring. I only have the front speakers (Polk db650) connected, and it goes into protect mode after 7-8 minutes of normal use at low volume. Once in protect mode, it goes in and out of protect mode at 15 second intervals even if I disconnect the speakers (while it's still on).

Amp busted? Where do I stick the probes for a multimeter to check the voltage from the battery? And thanks for the resistance/impedance thing, I didn't realize speakers got AC from the amp ...

mercman

A good test is to start by connecting the volt-meter (DC) a directly on the power and ground terminals on the amp. Take a measurement with the music playing and the engine off. Then immediately go to the battery and measure the voltage across the terminals. It should be the same. If you have a large drop you have a bad ground of power connection. It’s usually the ground. Lets say your battery voltage reads 12.5 volts at the battery and the voltage at the amp reads 11 volts. That’s no good.

You can check the ground connection by placing your meter (set for low DC volts) on the amp ground terminal and a good ground (a factory connection). With the amp running you should get zero volts. Any reading indicates resistance in the connection.

In short, if your speaker connections are clean and you have 12 volts at the amp and the amp is getting enough air, it should not shut down.

jeff

shrykhar

I'm getting 13 volts at the amp with the engine off, so I guess I'm SOL. Even when it's doing its protect mode winking act, the voltage is fine.

Uh, I also forgot to secure the positive terminal on the battery and it was loose -- my head unit actually asked me for the security code once when I closed the hood. *sigh* I suppose this might have damaged my amp's power supply?

98_2.5_TL

Svc Or Dvc?????????? 4 Ohms Or 2 Ohms??????????

shrykhar

I put in a different amp (Avionixx 440.4) and it's working now, although something sounds a bit off. Thanks for the help.