This is how to blow an amp

Try hooking a 1200 watt sub up to a 75 watt POS amp. It lasted for like 20 seconds and something blew and it all shut off. The sub is still fine though but damn now I need a new amp :( Any ideas? I wonder if I could build myself one?

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NachoMahma10 years ago
. OK. I think it's time to regroup and take a fresh look at this - I'm starting to get confused. . Parts: 1 bass driver with dual 4 Ohm coils rated for 1200W, 1 cabinet, 1 amp rated 75W. Are you using any type of crossover or other circuit between the amp and driver? . Goal: maximum volume with little regard for quality. . . If the amp sounds good with another sub, the that leads me to believe that the problem is in the woofer - a bad coil or improper wiring are my first two guesses. . Try using just one coil. Hook a coil up to either channel (straight from amp outputs to driver; bypass everything else) and listen at about quarter volume. Now use the other coil and listen at the same volume. Any difference? If so, one of the coils is bad. . If it passed the first test, wire the coils in series, hook to one channel on the amp, and listen at quarter volume. If it sounds OK, then go ahead and roll the volume up slowy while listening for distortion. Rearrange the wiring so that the coils are out of phase (tie the +s on the coils together and wire the -s to the amp) and give another listen. Wired one way should sound clear and the other way "muddy." If it sounds better with the +s wired together, then your coils are out of phase - not a problem if you are aware of it. . Whew! Time for a break. Try this stuff and see what happens. . Oh! Where did you see the stuff about dual-coil drivers and "off beat" music not being compatible?
Punkguyta (author)  NachoMahma10 years ago
Okay all give those a try, I'm just a bit afraid to in case I blow something and can't take it back to them. When I said it sounded crappy, that's when I had it wired in parrelel to the amp (btw it's apparently rated for 300 W dynamically (Whatever the hell that means)). I changed it around to be series which makes my amp pretty damn hot and I have to turn it off once in a while but it sounds basically how the other one did except with a little distortion and not as loud. I'm not using a cross over, although the amplifier does have a limited crossover in it's circuits, but only through high level inputs, it doesn't seem to filter the ouput when it's hooked up via the rca input. I have a kenwood amplifier that is hooked up to this smaller 75 watt amp. The kenwood has a digital 10 band equalizer that works in real time (it's fun to watch) and I set it to cut off everything above 80hz, it works fairly well combined with the panel amp. I'll try testing the sub like you suggested but one thing I did notice is that the cone is very hard to move (when it's off) which I'm guessing is because of the heavy duty voice coils, the leads that come off the push terminals go straight through the spyder and it interlocks through the waves in the spyder, looks neat and definatly a far off design from anything I've ever seen. Might be why it sounds a little different. Now another thing, the excursion on this subwoofer is pretty much the same size as the other one, and the amp seems to be able to push it out to it's full length and it's not that loud, if I got a 1200 W amp for it would it be louder?
> I'm just a bit afraid to in case I blow something . That's something I haven't noticed in you. heehee But I'm learning to deal with it. ;) . > 300 W dynamically (Whatever the hell that means) . Marketing mumbo-jumbo for "It has some reserve power." It can put out the extra power for very brief intervals. Always be skeptical of amplifier power ratings. They are usually shown as xxW @ 0.yy%THD (Total Harmonic Distortion). Some companies will use 0.01% and others will use 0.1%. And there are probably others schemes nowadays. Just make sure you're not comparing apples to oranges. . > cone is very hard to move (when it's off) . The coils should not have any effect on how hard you have to push to move the cone. This is determined by the suspension (the ring between the outer edge of the cone and the frame). The coil/core may be in a bind, which is a big problem. . > excursion on this subwoofer is pretty much the same size as the other one . Is the excursion (distance cone moves) the same or the size (diameter)? I don't think the human eye is sensitive enough to determine excursion, but I could be wrong. If the size is the same, then they should produce about the same amount of sound (depending on efficiency, enclosure, &c) from the same excursion. . > if I got a 1200 W amp for it would it be louder? . Yes. But remember, power:loudness is a log function - it takes 10x the power to get twice the sound. Ie, a 1200W amp is only twice as loud as a 120W one. For you, I highly recommend that you stay well below the speakers rated capabilities. . . For your system, I don't think you are going to be able to harm the woofer, no matter how you wire it up. Woofers, by their nature, are very rugged. They have large coils that can take quite a bit of heat. Tweeters and mid-ranges are a different matter. They cannot handle the DC encountered when an amplifier clips (causes the coil to heat up). . What you need to worry about are your amps. You are pushing them too hard from what I can tell. Not only do you risk your amp, but as above, you run the risk of burning up tweeters (when used). . . How about a lead to the stuff on dual-coil/stereo problems? I'd like to check it out and see if I'm wrong about it.
Punkguyta (author)  NachoMahma10 years ago
A link to how they're able to be wired?: One link I found

I don't think the core is binded/frozen or it would not move at all and possibly make some pretty sweet smoke. And maybe I'm just expecting too much from a sealed/ported enclosure (it was a sealed one until I cut holes in it). I wanna make a bandpass box but I'm too dumb to make one of those and the only thing I could figure out was a square ported box which do sound pretty good.
. According to that link, I'm right about the dual-coils - "You can wire each voice coil to a separate channel of your amplifier, ..." - but wrong about the output impedance of modern car amps - "... most car amps are stable down to 2 ohms in normal operation, ..." I'd say there's a good possibility I'm wrong about home amps being 8 Ohm, also. They may go down to 4 w/o problems. Which is all in your favor! :)
Punkguyta (author)  NachoMahma10 years ago
I just googled that, but if you google "wiring a dvc sub to seperate channels" tell me what you find.
. I've got a better idea: post the link(s) you are referring to.
Punkguyta (author)  NachoMahma10 years ago
It's in here .

"Sure Tim...You just use a Y from the Sub out of the main receiver to whatever input on the unit you're using to drive the sub. It is a mono signal being sent, its just being amplified by two amp channels. I think it is typically suggested to NOT send two amp channels to a single VC though."

"At least you were playing the same signal through both channels but still there is potential for damage."

"it is typically suggested to NOT send two amp channels to a single VC" (my emphasis). My suggestion is to wire one amp channel to a single VC - two times.
Punkguyta (author)  NachoMahma10 years ago
But you did ask me where it said that you shouldn't wire each vc to seperate channels right?
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