DiyMobileAudio.com Car Stereo Forum banner
1 - 19 of 19 Posts

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #1 ·
Hypothetically speaking...


Let's say I know a guy who is related to a girl who is dating this dude. He had 4 subs wired parallel to an amp.All is well for like 2 months.

All of a sudden one day at volume 30 out of 63 playing some rap song the subs all go out. The amp is checked and all three fuses are popped. The fuses are replaced. no sound from speakers. Speakers are pulled and found to show open on a DMM. They are sent back to manufacturer who finds the tinsels are melted.Manufacturer fixes them by soldering direct to coils speaker wire.

Speakers are reinstalled in box. Amp is checked out. All wiring is correct and secure. Dude is driving to work. Again volume at 30. Bam Speakers go out and are showing open again. Again this is simultaneous.

Any idea's???
 

·
Registered
Joined
·
1,756 Posts
hmmm....interesting. ive had an amp keep blowing fuses when it was turned on but nothing with subs...

what are the ohms of the four subs? type of subs? amp?
 

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #3 ·
subs are 4 ohm single coil. Make of amp and subs are irrelevant. Amp is Class D mono block stable to 1 ohm.
 

·
Registered
Joined
·
177 Posts
Did all 4 subs melt the tinsel leads? If so I would guess the amp has a problem as I doubt all 4 subs would fail at the same time.
 

·
Registered
Joined
·
1,756 Posts
he says parallel so the amp only sees 4 ohms which it is stable down to 1 ohm...unless i have series and parallel mixed up
 

·
Registered
Joined
·
177 Posts
he says parallel so the amp only sees 4 ohms which it is stable down to 1 ohm...unless i have series and parallel mixed up
Actually what you are describing would be a series parallel configuration.
 

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #7 ·
Amp is seeing a 1 ohm dcr load. Yeah, I think it is the amp. Just bums me out. Am recommending that it be sent out to be fixed.
 

·
Registered
Joined
·
177 Posts
1 ohm can be stressfull on an amp. I would think it would last longer than 2 months tho. What kind of amp is it? Sounds like its having a power surge issue.
 

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #9 ·
Meh, this amp is designed to run 1 ohm all day long. Hell I myself have a class D mono block and can run it .5 ohm dcr all day long. as for the amp, I blame myself. At least for this second round of smoking the leads. I should have told the "dude" to send it in. Oh well.... Hindsite golden and 20/20 and all that...
 

·
Registered
Joined
·
636 Posts
The subs are 4 ohm "nominal". This means their impedance could dip below 4 ohms at some frequencies.

If they are all in parallel it is a "nominal" one ohm load. But depending on the sub, the impedance may dip well below 1 ohm when all 4 are in parallel. Could draw crazy current from the amp, causing it to fry. Amp may be built poorly, resulting in large surge and frying all 4 subs at once and fuses. Just a guess as to what is going on.
 

·
Registered
Joined
·
636 Posts
Oh, and what kind of a manufacturer fixes tinsel leads with speaker wire? Sounds shoddy to me. Sure it may work. But that's just stupid.
 

·
Registered
Joined
·
17,148 Posts
Before they go pop, is there a weird sound, a burp, or anything?

Are the tinsel leads melting or going weak from fatigue and building heat at that point?

are you sure you aren't nuking one at a time and the others start go go quicker and quicker till they are all dead?

The amp popping fuses kinda screams that it's running away.
 

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #14 ·
Is the girl hot at least?
Man after my own heart.

Xander, though this is true on upper frequency reproduction, I have tested these subs as well as about 20 others in differing configurations. ALL have been significantly higher due to impedance rise. I usually test 20 to 100 hertz in 5 hertz increments. In all cases, the subwoofer/box combos have been at a minimum 2 times higher than dcr. Get a clamp meter and check out your substage along with a DMM. You will be surprised to find that a 4 ohm sub will usually be showing a minimum of 8 ohms and in most cases a minimum of 10-12 ohms during music or tones. All due to Impedance rise.

Also this is not a "cheap" amp nor is it from a flea market. I think it just may be "one of those things" that can happen.

As for the speaker wire fix, I requested it. Look at DD subs as well as some other pure SPL manufacturers. I will take a 12 gauge connection over an 18-20 gauge tinsel lead. Maybe a slight exaggeration but you get my point.
 

·
Inappropriate Thoughts
Joined
·
4,007 Posts
The amp popping fuses kinda screams that it's running away.
Either that or there is a problem with the amp. In high school, I had a Punch 150 that was purchased from the local dealer and it kept popping fuses. I brought it to the dealer multiple times, they called Rockford Fosgate and their techs kept saying use a bigger fuse. Keep in mind, I was running a pair of 8" kicker subs at 8 ohms mono and there was NO reason for that 25 amp fuse to be popping like that. Well, this went on for several months and I was up to a 40 amp fuse before it would stop popping on me.

A couple of weeks later, the torrid catches on fire and that is the end of my amp.:( The dealer sent the amp to Rockford fosgate, and Rockford Fosgate gave me a brand spanking new one under warranty!
 

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #16 ·
Before they go pop, is there a weird sound, a burp, or anything?

Are the tinsel leads melting or going weak from fatigue and building heat at that point?

are you sure you aren't nuking one at a time and the others start go go quicker and quicker till they are all dead?

The amp popping fuses kinda screams that it's running away.
Hey Chad! thanks for popping in.

the first time the fuses went. There was a strange sound like the subs got quieter. I was in the vehicle at the time and can verify that the volume was at 30ish (not above 35 not below 30) this lasted about 5 seconds and then just went out.

This time fuses are ok. Subs just went out. At volume 30. He checked. Had the guy use a multimeter and they are showing open circuit again. And again it was simultaneously. If it wasn't it was so close it probably doesn't matter.

I was wondering if the amp for whatever reason was putting out DC. Anyway I told the guy to get an RMA and he did. Will update when I know more. He is thinking about getting some JBL GTo subs to replace the blown ones. I may try my hand at rebuilding them
 

·
Registered
Joined
·
2,450 Posts
Discussion Starter · #17 ·
Please understand if I can't give details as a lot of this has been diagnosed by cell phone, cell phone pics and walking the guy through as I am in Texas right now. Will answer any questions and thanks for trying to help all!!
 

·
Registered
Joined
·
17,148 Posts
Maybe the first time the reduction in volume was 1-2 subs letting go, then the voltage increased further as the impedance went up and nuked the other ones. The blown fuses could have been the leads shorting together making the amp draw huge current into a dead short.

That's my Colombo reasoning.
 

·
Registered
Joined
·
26 Posts
Hypothetically speaking...


Let's say I know a guy who is related to a girl who is dating this dude. He had 4 subs wired parallel to an amp.All is well for like 2 months.

All of a sudden one day at volume 30 out of 63 playing some rap song the subs all go out. The amp is checked and all three fuses are popped. The fuses are replaced. no sound from speakers. Speakers are pulled and found to show open on a DMM. They are sent back to manufacturer who finds the tinsels are melted.Manufacturer fixes them by soldering direct to coils speaker wire.

Speakers are reinstalled in box. Amp is checked out. All wiring is correct and secure. Dude is driving to work. Again volume at 30. Bam Speakers go out and are showing open again. Again this is simultaneous.

Any idea's???
well no matter what,,, in order for this to blow your leads and or coils.. they would either have to see the full 12 and current of the car battery,, or be exposed to full rail voltage,, for more than a sinusodial wave....

I would think that something is wrong with the final output stage biasing circuits,, causing thm to turn on the transistors at full voltage or something.. or some kind of problem with the board,, allowing either the full 12 volts of the battery or full rail voltage to leak into the output circuit....

either way if it is happening,, do not hook it back up..
 
1 - 19 of 19 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top