# amp problem



## Nismo240 (Jul 24, 2004)

whenever i turn on my car to let the amp run, it'll work until the subs hit and it blows the fuses on the amp. can someone help me with this?


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## Nismo240 (Jul 24, 2004)

anyone????


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## Orbital199 (Feb 7, 2005)

How many times have you blew a fuse?


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## sr20dem0n (Mar 19, 2003)

what amp, what subs, how are they wired


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## Nismo240 (Jul 24, 2004)

Orbital199 said:


> How many times have you blew a fuse?


this was the only time it has done this.


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## Nismo240 (Jul 24, 2004)

sr20dem0n said:


> what amp, what subs, how are they wired


its a kenwood 800 watt amp and RF P2 subs. when you say how they are wired, do you mean if they are bridged or not?


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## optimusp99 (Sep 19, 2005)

Yes is your amp bridged? For now turn down the gain on your amp. What type of amp and sub do you have?


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## Myidolis (Oct 17, 2005)

Blown fuse? Hmmm. If it's only done it once, it could have just been a faulty fuse. But (i'm a home audio and video expert, but not as much dealing with cars, but wiring is very similar.) if it wasn't a coincidence, it sounds like your sub has a safety built in to prevent you from blowing it. Since they don't draw their own power, but rely on an amplifier, there is no other way to cut off the power supply before it blows, so your fuse (relatively inexpensive) may act as a sacrificial lamb, in order to prevent you from ruining your sub. (couple hundred bucks.) So:
1. Get a new fuse obviously
2. turn down the gain on your amp
3. Turn down the volume on your sub (if it has one.)
4. Turn UP the frequency on your sub. The higher the frequency the shorter the wavelength, the less power your sub needs to output to achieve a successful 
hit.

If that doesn't help, check the connecting wires on your amp and sub. Look for any wires that have ANY metal exposed that is touching ANYTHING. 90 percent of the time you blow fuses or speakers it is due to power overload, often from one wire that is touching anything metal. (touches metal, conducts electricity, allows WAY too much power to pass through the wire.) 

If that doesn't help...then i'd say take it to best buy ( i work there) and let one of the car audio guys look at it. They are usually very knowledgeable and will only charge like twenty bucks to diagnose the problem. And usually very little to fix it (assuming it's not a major problem)

Good luck.


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## Nismo240 (Jul 24, 2004)

optimusp99 said:


> Yes is your amp bridged? For now turn down the gain on your amp. What type of amp and sub do you have?


yeah, the amp is bridged. i put what kind they are a few posts up.


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## Nismo240 (Jul 24, 2004)

Myidolis said:


> Blown fuse? Hmmm. If it's only done it once, it could have just been a faulty fuse. But (i'm a home audio and video expert, but not as much dealing with cars, but wiring is very similar.) if it wasn't a coincidence, it sounds like your sub has a safety built in to prevent you from blowing it. Since they don't draw their own power, but rely on an amplifier, there is no other way to cut off the power supply before it blows, so your fuse (relatively inexpensive) may act as a sacrificial lamb, in order to prevent you from ruining your sub. (couple hundred bucks.) So:
> 1. Get a new fuse obviously
> 2. turn down the gain on your amp
> 3. Turn down the volume on your sub (if it has one.)
> ...


since you work at best buy, maybe you can help me. i bought the amp from there and got the 4-year warranty plan with it, but they did not install it. would it be free of charge for them to fix it, or would it cost since they didn't install it?


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## sr20dem0n (Mar 19, 2003)

Nismo240 said:


> its a kenwood 800 watt amp and RF P2 subs. when you say how they are wired, do you mean if they are bridged or not?


Model numbers man....the brand and it's power rating tells us nothing about how the amp was designed. And by the wiring, I meant just that, how are they wired? Ok the amp is bridged, fantastic, is it a 2ch? 4ch? Are the subs single 4ohm? 8ohm? Wired in series? Parallel? Separately?


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## sr20dem0n (Mar 19, 2003)

Myidolis said:


> it sounds like your sub has a safety built in to prevent you from blowing it.
> 1. Get a new fuse obviously
> 2. turn down the gain on your amp
> 3. Turn down the volume on your sub (if it has one.)
> ...


The sub is a completely passive device, it has no safety features nor anything that could "tell" the amp that it's being pushed too hard

1 & 2 - yes
3 - the sub is passive, it has no volume control of its own
4 - this came completely out of left field and makes no sense at all

I wouldn't take it to Best Buy, I've never met anyone who even knew the difference between a spider and a surround that worked in the car audio department at Best Buy. They've screwed so many installs up that it's ridiculous, I swear they'll let anybody off the street become an installer, it's sad. Granted I'm sure there are a few people who know what they're talking about, but there might be one of these people out of every 10 stores, not very good odds.


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## Myidolis (Oct 17, 2005)

sr20dem0n said:


> The sub is a completely passive device, it has no safety features nor anything that could "tell" the amp that it's being pushed too hard
> 
> 1 & 2 - yes
> 3 - the sub is passive, it has no volume control of its own
> ...


Care subs are passive? Hm. Well like i said, i specialize in home audio, so i'm not very familiar with the workings of car speakers and what not. Many receivers have safety features like that, so i figured it might be the problem. And it's very sad that best buys where you are have shitty installers. The one at the two stores i've worked at are all really good. Sometimes they'll mess something wrong, but they always get it right, and your installs free if they do it wrong...which is rare. 

How does four not make any sense? Whether it's a tiny tweeter or a 12" sub, the lower the frequency the more power it takes to fire. So if it's drawing too much power to fire and the fuse can't handle it...no more fuse. I'm not saying it's likely that thats the problem, but depending on how much this guy knows about audio, it's not all that unlikely...of course if the sub is passive then the frequency control would be done through the amp, if it's aloud to be adjusted at all...but all the amps i've seen have frequency control knobs.


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## ga16freak (Dec 31, 2004)

Myidolis said:


> Care subs are passive? Hm. Well like i said, i specialize in home audio, so i'm not very familiar with the workings of car speakers and what not. Many receivers have safety features like that, so i figured it might be the problem. And it's very sad that best buys where you are have shitty installers. The one at the two stores i've worked at are all really good. Sometimes they'll mess something wrong, but they always get it right, and your installs free if they do it wrong...which is rare.
> 
> How does four not make any sense? Whether it's a tiny tweeter or a 12" sub, the lower the frequency the more power it takes to fire. So if it's drawing too much power to fire and the fuse can't handle it...no more fuse. I'm not saying it's likely that thats the problem, but depending on how much this guy knows about audio, it's not all that unlikely...of course if the sub is passive then the frequency control would be done through the amp, if it's aloud to be adjusted at all...but all the amps i've seen have frequency control knobs.


Haha is it just me or does that still sound like a heap of bs? Either you are just making shit up as you go or we are missunderstanding youl.


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## sr20dem0n (Mar 19, 2003)

Myidolis said:


> How does four not make any sense? Whether it's a tiny tweeter or a 12" sub, the lower the frequency the more power it takes to fire. So if it's drawing too much power to fire and the fuse can't handle it...no more fuse. I'm not saying it's likely that thats the problem, but depending on how much this guy knows about audio, it's not all that unlikely...of course if the sub is passive then the frequency control would be done through the amp, if it's aloud to be adjusted at all...but all the amps i've seen have frequency control knobs.


What frequency control are you referring to exactly? The only one I can think of is the lowpass cutoff frequency. If that's the case, then by turning it up the sub would still be receiving the low frequencies as well as higher frequencies. If anything it would draw more power, not less. The only way to cut out the low frequencies is to use a subsonic filter which 99% of the stereo amps out there don't have, and is pretty pointless considering the entire reason behind a sub is to play those low frequencies that you're now trying to cut out.

Low frequencies don't require more power to reproduce by nature, if you have speakers with similar efficiencies it will take the same amount of power to reach 90dB at 40hz as it will to reach 90dB at 2khz. Actually, due to cabin gain it would take less power to reach 90dB at 40hz than at 100+hz. With music it's not balanced like that though, since 120dB at 40hz is fine but 120dB at 2khz would have you running away in fear. Lower frequencies do have more content, which means for most music the sub will require more power (since it's playing several dB louder than the rest of the speakers) but this has nothing to do with the wavelengths of the frequencies it's playing.


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## captain_shrapnel (Sep 10, 2004)

Nismo240 said:


> anyone????


Hey, to restate sr20dem0n's question again: supply us with the model name and maker along with impedence of the sub load. Although we cannot accurately diagnose this issue without said info, if you constantly blow fuses I would guess that you are running too low of an impedence for the amp. If it just blew one time out of the blue, just reload a new fuse and go.


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