Bad AMP???? ;(

[Nikku]

Ok, I got 2 sony 12" xplods ( 350rms@4ohm ) bridged to a 1000w sony xplod amp. I have the LPF all the way up, becuase the higher i had it the louder the bass. anyways the other day i was driving and after about 2 min the bass went low ( like it wasnt as loud as normal ) then after about 5 sec it went back to normal. Then today i get in and its really low. i had the stereo turned up to 18 and it didnt sound near as loud as it usually does on 10. then after about 5 min it went really low! I havent tried it agian yet cuz im at school, any ideas on what it might be?

I think its the amp, could it be a fuse?

if it is the amp can someone lead me to a good amp? or atleast help me understand what the specs mean on the amps? since i have 2 12" at 350rms@4ohms does that mean i need an amp that does atleast 750w@2ohm x 2?

Modified by Nikku at 7:16 AM 1/16/2007
Modified by Nikku at 12:25 PM 1/16/2007

[Looneybomber]

2 subs wired together to a bridged 2chan amp. How are the subs wired together and what are their impedence (ohm) rating? I fear you wired 2, 4ohm subs in parallel, then bridged your amp, resulting in 1ohm per channel. I doubt that Sony amp is stable at 1ohm thus the reason why it's all focked up. Try wiring your subs in series and hope you didn't burn up your amp from ignorance.

If you did, expensive lesson learned right?

Also, if you have no idea what I'm talking about, start doing a little research. It will help you later with your car stereo stuff.

[qsiguy]

I concur with Looney. Sounds like you've got two 4 ohm woofers and most people that don't know better wire all of the positives to the positive on the amp and all the negatives to the negative on the amp. In this case all to one channel which is the left and right channels bridged. (usually left positive, right negative). This is called wiring in Parallel and will make your subs look like a 2 ohm woofer to the amp. When you bridge the amp you cut that value in half again, which gives your amp a 1 ohm load. It'll be super loud until the amp fries. Might explain why it was so loud prior to the meltdown.

To determine if the amps dead you'll have to do some testing. Try some different speakers, try a different source/radio, check all the fuses (but if it's intermittant it's probably not fuses), Check the ground and of course power connection. It's a process of elimination.

[homeslicej2]

I concur as well w/looney and nikku based on what info you've given. If you could put up a diagram showing how you wired them it would help us help you to diagnose the problem. Research is a must as well.

[Nikku]

ok i have my subs wired like so 4ohm( WOOFER )---| 4ohm ( WOOFER )---|-----[ AMP ]

I thought if i had it wired like this then it would be a 2ohm load on the amp, not a 1ohm? can someone explain this to me??? also i replaced the ground wire and 12v wire and now everything seems to be working fine.

I dont belive my amp is stable at 1ohm though.

So when it burns out............... back to wallie - world hahahahah

can someone point me to an amp that is stable at 1ohm and can handle both these subs bridged? there both 350rms

also is having the subs in parallel the best way to do it?


Modified by Nikku at 6:56 AM 1/17/2007

[homeslicej2]

First off, based on your drawing I still can't really tell how you've wired your subs. Also, are they SVC or DVC (single or dual voice-coil)? That's is important to know. I assume they are SVC. In that case it looks like they are parallel this would give you a 2-ohm load. Most 2-channel amps are not 2-ohm stable in a bridged configuration. If you want a 1-ohm load capable amp, they usually more expensive. FYI running an amp at 1-ohm, even if it's capable of it, results in several things, some of the most important ones are more heat and more distortion. Both translate into shorter amp and sub life and greater potential for hearing damage. Many brands make 1-ohm stable amps. Some to consider might include Hifonics or Memphis, but there many others. Google it. Googling works to answer your sub wiring question as well. There are several good diagrams and car audio learning centers on the web. Here is a link to Crutchfield's sub wiring diagrams. http://www.crutchfieldadvisor.....html

A few last questions. You said you replaced the power and ground wires. What size were they, what size are they now, did you remove all paint and go to bare metal for the ground and paint over it to keep the the metal from rusting, and what is the fuse rating of your amp? This and the amp's RMS (not peak, which is most likely what is written on the top of your amp) wattage output along with length of power wire will help to determine the appropriate size power wire needed.

Last thing. Most manufacturers do recommend parallel over series. Not entirely sure why (it deals with the electrical mechanics & properties of the sub but I don't know the nitty-gritty of it), but they do. Hope all this helps.

[qsiguy]

The reason your 2 ohm load is 1 ohm at the amp is because a bridged amp will see half of the resistance of the load. If you wire one 4 ohm woofer to the amp bridged the amp sees 2 ohms, one 8 ohm woofer bridged the amp sees 4 ohms.

You can combine series and parallel wiring in your speakers configuration to achieve whatever load you want for your amp. The amp doesn't see how many speakers you have, it sees the load or resistance. Technically you can have 100's of speakers wired to one channel as long as the impendance isn't below what the amp will handle. Keep in mind you the power output of the amp will be devided up between all those speakers tho.

Two 4 ohm woofers in parallel will be at 2 ohms and the amp, if bridged will see 1 ohm. If you wire those same subs in series the load would be 8 ohms and the amp, again if bridged, will receive a 4 ohm load. Dual voicecoil subs give you many more wiring options because each sub is really like two separate subs and you can wire them in series or parallel and then wire that one in series or parallel with the 2nd sub and you have limitless (almost) options.