02' Rockford 450s amp DEAD?!?!

[C.Palmer]

I need some help here... my amp started cutting out on me a little over a week ago. It's a Rockford Fosgate power series 450s amp that I bought new this year. It's bridged to a JL 12-W6 amp. I thought it might have been over heating so I would shut it off and let it cool... sure enough it would start working again but only for a short while until it cut out. Then it starts cutting out at low volumes. Well I just let it sit for 4 days while I went to San Diego and come back to nothing from it at all. I have 2 in-line fuses going to it and they're fine. I'm pretty sure the fuse in the amp is good.

Did I just loose my NEW amp?! help!! :mad:

[TransNot]

well i know this seems like a stupid question to ask, but is it hooked up wrong? ground to pos, pos to ground? and are you overpowering it? enough abuse to a amp will kill it eventually... you also might want to check and see if it's the sub that's dying... also could be the rca outs from the cd player, why don't you give more specs on everything you've got (rms wattage and brand mostly).

[v6maro]

how about you find some info on your amp for us, if it's to a single 12w6, then how did you wire it up? Series or parallel? With the W6, they are DVC's so you are either at a 3ohm or 12 ohm load, and is your amp capable of handling either of those loads?? If not, you probably fried something internal or it's in protection mode not allowing it.
-Steve

[TransNot]

ooh i suppose ohmage would be nice to know too [img]tongue.gif[/img]

[C.Palmer]

3ohm... i took advantage of the DVC's. I believe the sub peaks at 700 although I could be wrong. The amp is bridged. I pulled it out of my car today and found nothing fried internally but that was just me pulling off the exterior cover and taking a look at the board.

Yes everything is hooked up right... it sounded great for about 6-8 weeks until now. I re-did my ground and everything to make sure that was satisfactory. I pulled my deck and checked all my connections which were [img]graemlins/thumbsup.gif[/img]

I might try hooking it up again tomorrow and running the sub off 1 channel instead of bridging it. if it's stuck in safe mode then maybe that will ease it out of it. I might try 12ohms as well. Is it worth my time or should I just take the amp in to have it checked while it's out of my car? Please keep in mind I moved from out of state a little over a month ago so I have no connections and no luck finding a job yet... my last paycheck before leaving was gone 2 weeks ago :(

[TransNot]

so your subs and amp were both wired to push at 3 ohms?

[C.Palmer]

<blockquote>quote:</font><hr>Originally posted by TransNot:
so your subs and amp were both wired to push at 3 ohms?<hr></blockquote>

yup

[Backfire]

That Fosgate amp, like most of them, is rated for 2Ohm per channel. So a 3Ohm bridged load is going to look like 1.5Ohm per channel to the amp. So, you are pushing the amp beyond what Fosgate specifies. I have heard of people running them that way, but these amps already run hot and pushing it harder only increases that. I tried playing a Soundsteam SPL12 on a 600a4, that was a 1ohm per channel load. It played it, but I didn't risk trying it for extend amounts of time. How hot did the amp get when playing?

If you try the series wiring, the 12ohm load is much easier on the amp, but at 6ohms per channel, you will probably only see ~80W per channel, or 160W to the sub. That is a little low for max output, but for actual listening, that should work quite well. JL recommends 125-300W. Even if you do get it working properly again, I would suggest that arrangement simply for the life of both your sub and amp. You were probably sending it close to twice what JL recommends with your current setup.

[TransNot]

mixing ohms is not only bad on the amps, but it's also confusing. make sure they match the way they're hooked up.

[Backfire]

What do you mean by mixing? He is running a single sub. He is bridging the amp, so each channel will "see" half the nominal resistance of the speaker.

Using his numbers, a series configuration is 6Ohm + 6ohm = 12Ohm. By bridging the amp, you are running a 12ohm bridged setup, which is equivalent to a 6ohm stereo setup.

If he were to use a parallel wiring for the sub, the would be looking at 1/6ohm + 1/6ohm = 1/Restistance. Therefore, Resistance = 3ohm. If he runs that as a 3ohm bridged setup, each amp channel will see 1.5ohms.

[ July 24, 2002: Message edited by: Backfire ]</p>

[TransNot]

sorry, mixing nominal ohms ratings is bad.

[C.Palmer]

<blockquote>quote:</font><hr>Originally posted by TransNot:
sorry, mixing nominal ohms ratings is bad.<hr></blockquote>

you still didn't explain yourself.... what do you mean? Are you saying that since I've been running at 3ohms it would be bad to switch to 12? There's no need to get defensive we're just asking for a more in-depth explaination of what you're trying to say so your information is worth something to us...

[TransNot]

what i'm trying to say is it's not good to have an amp rated to push at 2 ohms push subs that are rated to be pushed at 3 ohms.

[Backfire]

<blockquote>quote:</font><hr>Originally posted by TransNot:
what i'm trying to say is it's not good to have an amp rated to push at 2 ohms push subs that are rated to be pushed at 3 ohms.<hr></blockquote>

If the amp is rated to drive a 2 ohm load per channel, and you wire it to 3 ohms per channel, there is no problem. Using a sub configuration where the resistance is greater than the rating of the amp isn't bad at all. You may not be getting maximum power from your amp, but if you are getting ample power to your subs then it will work great.

The problem is when you run a configuration where the resistance of the load is less than the amp's rating.

It could just be mixed up terminology, but subs are not rated to be pushed at a certain resistance. Speakers are measured to determine their nominal, "average", resistance. Since the actual restance changes during playback depending on frequency and some other variables, the nominal value is used when determining the amplifier requirements. With a dual voice coil sub, I don't believe there is a difference in performance based on how you configure the coils, as long as the needed power is provided. Taking his 12W6, it can be wired as either 3ohms or 12ohms. As long as the amp can provide the XXXXwatts needed, either config will work the same. If an amp has a minimum resistance per channel of 2ohms, but the user can get the needed power from the amp when connecting a 6ohm load, there are no problems with that.

[TransNot]

sorry, as backfire said the amp saw the subs as 1.5 ohms, which is lower than the 2 ohms the amp is rated at. v6 maro, you know what you're talking about and you seem to have plenty of expirience.

i've just always been told that your nominal ohms should match, obviously i wasn't informed completely.