20w rms amp with 150w rms sub

[zerox61]

hi. i got a temporary speakerset up. i got a 20watt rms amp and hooked it up with two subs, both is 150w rms with 8 ohms. the amp is 4ohms so i put the subs on on parrallel to match it. im just wondering.. i put the volume to max and there is lots of pop and distortion and clipping. just wondering if that will damage the subs. since the amp is only temporary i dont really mind that blowing up. but i want to keep the subs safe. im pretty sure it wont even harm the subs but just asking to make sure. thanks

 

[Seth=L]

hi. i got a temporary speakerset up. i got a 20watt rms amp and hooked it up with two subs, both is 150w rms with 8 ohms. the amp is 4ohms so i put the subs on on parrallel to match it. im just wondering.. i put the volume to max and there is lots of pop and distortion and clipping. just wondering if that will damage the subs. since the amp is only temporary i dont really mind that blowing up. but i want to keep the subs safe. im pretty sure it wont even harm the subs but just asking to make sure. thanks

It can damage the subs. DO NOT UNDERPOWER SPEAKERS IT DESTROYS THEM. The clipping from the amplifier presents the distortion into the driver, which is hard work for the driver. Prolonged use will damage or blow the woofers. I would suggest not allowing it to clip.

 

[zerox61]

but the subwoofer should be able to withstand the output from the amp? i heard from someone, that cuz its 20w rms. and the woofer is 150w rms it should be able to handle 20watts at any signal. but that kind of confuse me coz clipping is from dc current. and it shoud heat up the coil and maybe damage it over time. but a 150w sub prob has more heat resistance so it wont be damaged?

 

[Nomo]

Don't Do that

20 watts ain't much power for an amplifier. When it tries to play louder volumes or difficult loads it struggles. The stuggling results in distortion. Distortion, not too much power, is biggest factor in speaker damage.

 

[Seth=L]

MORE SPEAKERS ARE BLOWN FROM UNDERPOWERING. No one hear is going to tell you otherwise.

 

[Sheep]

Call it premature... but this could get troll worthy...

Anywho... Listen to the above posters... you're going to destroy your subs, and maybe the amp too.

SheepStar

 

[mtrycrafts]

but the subwoofer should be able to withstand the output from the amp? i heard from someone, that cuz its 20w rms. and the woofer is 150w rms it should be able to handle 20watts at any signal. but that kind of confuse me coz clipping is from dc current. and it shoud heat up the coil and maybe damage it over time. but a 150w sub prob has more heat resistance so it wont be damaged?

No, clipping is not from DC current at all, even if the wave form has a flat top and bottom for a short period before it changes direction. At clipping, the power that is output is not 20 watts with this amp but at least 2X. Even though that is less than the rated power, it has and creates harmonics and creates stress on that driver.

 

[zerox61]

i was reading on this site and it goes:

If your speakers are capable of handling significantly more than your amplifier can produce, driving them with a clipped signal will not likely hurt them.

If the speakers can handle 3 or 4 times the power that your amplifier can produce, there's virtually no way to damage your speakers (no matter how clipped the signal is).

If your speakers are rated for the same power handling as your amplifier is capable of producing cleanly, driving them with a clipped signal for extended periods of time may cause speaker damage and/or premature failure.

If your speakers are rated for the same power handling as your amplifier is capable of producing cleanly, driving them with a square wave signal for extended periods of time will likely cause speaker damage.

at www . bcae1 . com / 2ltlpwr . htm

and my bad.. by saying dc i meant a square wave didnt know there was a proper name for it untill i read the site

btw not tryna proove whos right or not. i just wanna kno if this guy is correct.
and i should be able to play it at normal volume and not cause damage right?

 

[fmw]

hi. i got a temporary speakerset up. i got a 20watt rms amp and hooked it up with two subs, both is 150w rms with 8 ohms. the amp is 4ohms so i put the subs on on parrallel to match it. im just wondering.. i put the volume to max and there is lots of pop and distortion and clipping. just wondering if that will damage the subs. since the amp is only temporary i dont really mind that blowing up. but i want to keep the subs safe. im pretty sure it wont even harm the subs but just asking to make sure. thanks

Just note that the amp is not 4 ohms. That is a speaker impedance measurement. If you wire speakers in parallel that effectively halves the impedance. If you wire them in series it effectively doubles it. I would suggest wiring the subs in series, assuming it is a mono amp, unless it handles full power into 4 ohms. Even better would be to use just one of the subs.

Most A/V people don't understand how much 20 wpc really is. I would bet my home theater receiver never needs to put out 20 wpc - even on peaks. Not even close. The reason is that I have a powered subwoofer. For full range speakers 20 wpc would handle most stereo systems in most rooms of a home without a problem. Subs are a little different because then really do need more power because there is more mass to move. Your amp will power them if you wire them in series and don't play them too loudly. You aren't likely to produce any damage but you will produce some distortion. If and when the amp clips, the distortion will be quite audible, even from a subwoofer.

 

[zerox61]

Just note that the amp is not 4 ohms. That is a speaker impedance measurement. If you wire speakers in parallel that effectively halves the impedance. If you wire them in series it effectively doubles it. I would suggest wiring the subs in series, assuming it is a mono amp, unless it handles full power into 4 ohms. Even better would be to use just one of the subs.

Most A/V people don't understand how much 20 wpc really is. I would bet my home theater receiver never needs to put out 20 wpc - even on peaks. Not even close. The reason is that I have a powered subwoofer. For full range speakers 20 wpc would handle most stereo systems in most rooms of a home without a problem. Subs are a little different because then really do need more power because there is more mass to move. Your amp will power them if you wire them in series and don't play them too loudly. You aren't likely to produce any damage but you will produce some distortion. If and when the amp clips, the distortion will be quite audible, even from a subwoofer.

yeah im aware that 20 is plenty. what do u mean by connecting to series? i saying connecting them parrallel incorrect? and yeah i was just wondering if it would blow up on me when i push it to the max. which is pretty loud. so i dont always keep it on max untill it distorts.

sorry if i sound noob or anything. i dont know terminology. i only learnt from first hand experiences, experiments, mostly by myself or with my dad.so i dont read books although after exams i will learn more. and.. i learnt about sound at my school.. for like 5 weeks

 

[Seth=L]

"the guy" is not correct. If you think it is a good idea, go ahead. But I am telling you it is a bad idea, not recommended, and will cause damage in prolonged use (at clipping) square waveforms are not good for any speaker, no matter the power handling.

 

[mtrycrafts]

yeah im aware that 20 is plenty. what do u mean by connecting to series? i saying connecting them parrallel incorrect? and yeah i was just wondering if it would blow up on me when i push it to the max. which is pretty loud. so i dont always keep it on max untill it distorts.

sorry if i sound noob or anything. i dont know terminology. i only learnt from first hand experiences, experiments, mostly by myself or with my dad.so i dont read books although after exams i will learn more. and.. i learnt about sound at my school.. for like 5 weeks

20 watts is not plenty with a sub but peanuts. You are getting what you hear from over driving the amp, no matter what. Yes, the sub driver only may be fine with all that distorted signals and even when clipped and the power is 2x or 3x. But, your voice coils may run hot because of that high duration where it gets all that power into it. A sub does use a lot of power much of the time.

 

[Nomo]

zerox61,
You seem to be hearing only what you want to hear.
If you intend to use those subs for any length of time then stop powering them, especially at high volumes, with that 20 watt amp.
In the very least stop running them in parallel. Without knowing the sensitivity of the subs it's hard to tell how bad of idea you are having, but most here have told you it is a bad idea!

Sorry to come across as rude, but you ain't listening.

 

[Seth=L]

zerox61,
You seem to be hearing only what you want to hear.
If you intend to use those subs for any length of time then stop powering them, especially at high volumes, with that 20 watt amp.
In the very least stop running them in parallel. Without knowing the sensitivity of the subs it's hard to tell how bad of idea you are having, but most here have told you it is a bad idea!

Sorry to come across as rude, but you ain't listening.

Yeah, it seems like a confirmation thing. Since we aren't confirming what he believes or heard he is debating it. Get over it dude, it's bad for the subs.

 

[PENG]

Just for argument sake, a 20W amp is not going to blow 2X150W subs regardless, assuming each subs is truly rated for 150W rms continuous.

zerox61, you may want to measure the resistance of your sub with a multimeter, using the X1 resistant range. The reading you get will be the d.c. resistance. Let's say it measures 2 ohms, and assuming your amp can output a maximum of 40V (unlikely), you will get 20A if there is no voltage drop. Chances are, the voltage on the secondary winding of that ittle power supply transformer in your 20W amp will drop way down if the amp tries to deliver 20A (theorectical). In other words, you will get some self current limiting effect. Pure d.c. output may be the worst case scenario but in reality the clipped output is a distorted a.c. waveform that can be shown (using Fourier analysis) to consist of a.c. harmonics plus a d.c. component. As such, the overall impedance is going to be higher than its d.c. resistance.

The little amp will likely destroy itself or blow a fuse if there is one, before the subs will blow, assuming the subs are each truly rated for 150W rms continuous. Remember we are not talking about the mid and high frequency drivers that can be damaged much more easily by clipped signals produced by cranked up underpowered amps.

 

[zerox61]

ok i understand now. making more sense to me now. so when is parrallel and series wriring appropriate? is that only for the dual voice coil?

and any good sites for learning? since i been told that the site i showed b4 was wrong.

and yes i dc the subs from parallel ( and put them in series) lol jk. its only running on one now

 

[annunaki]

Wow lots of misinformation here.

You should be able to run that amp wide open on those subs all day long. There will not be enough power to damage the coils. A 20 watt rms amplifier fully clipped will at best output 40 watts. That in an of itself will not damage the speaker.

Do I recommend doing this, no. It sounds terrible.

If the sub is in a sealed enclosure you will get away with more clipping. The odd order harmonics and potential for extreme low frequency blips from the amplifier could cause mechanical damage with the sub moving beyond it's mechanical limits mainly in a ported enclosure below the tuning frequency. However, with only 40 watts I doubt the sub will even rach full xmax in a sealed enclosure.

I would be more worried about the amplifier failing and outputting a straight dc signal with the sub sticking straight in or out with no motion. This could burn up the sub as it would get continuous voltage dumped into it with no motion for cooling.

Too much power over time is what cooks a voice coil on a speaker, nothing more nothing less.

Mechanical damage can occur on a speaker due to excessive clipping but then the amplifier has to be outputting enough power (when fully or partially clipped) to drive the speaker past its mechanical limits.

Again, I don't recommend running an amplifier into clipping for the reason that it sounds terrible. However, as long as the subs mechanical limits are not compromised and the clipped power does not exceed the rms power handling of the speaker in question there is no harm in it. Again if the amplifier fails and outputs straight dc this is a serious problem.

A sub or speaker cannot tell if it is being sent a clean or distorted signal. It simply does what it is told by the amplifer output signal.

For tweeters, clipping of an amplifier can dangerous. The reason being that they do not have much motion for cooling and if they are being sent too much power they will fail quite quickly. Combine that with odd order harmonic information causing them to exceed mechanical limits and you have a recipe for disaster.

 

[annunaki]

ok i understand now. making more sense to me now. so when is parrallel and series wriring appropriate? is that only for the dual voice coil?

and any good sites for learning? since i been told that the site i showed b4 was wrong.

and yes i dc the subs from parallel ( and put them in series) lol jk. its only running on one now

Coils can be wired in series or parallel on individual drivers to achieve a particular impedance or ohm load.

Speakers are usually recommended to be driven in parallel if at all possible. Series connections between drivers are usually recommended to be avoided if at all possible.

DVC wiring tutorial: http://mobile.jlaudio.com/support_pages.php?page_id=161

Single Voice Coil (SVC) tutorial: http://mobile.jlaudio.com/support_pages.php?page_id=160

 

[Seth=L]

Oh wow, I have never been so wrong (wait, yes I have). Well don't a feel like a big stupid dope?

Sorry zerox61, I was really certain that is was bad for the woofers. We all make mistakes at times.

 

[annunaki]

Oh wow, I have never been so wrong (wait, yes I have). Well don't a feel like a big stupid dope?

Sorry zerox61, I was really certain that is was bad for the woofers. We all make mistakes at times.

Don't feel like that. It wasn't directed at anyone in particular.

There is so much misinformation about power, speakers, and clipping it will make your head spin.

Under normal circumstances, with the rms output of the amplifier matching the rms input on the speaker, clipping is definitely frowned upon, big time. It will most certainly lead to failure of some kind at some point.

Clipping in and of itself is not the destructive force, it is the extra power generated along with odd order harmonic information that will push a speaker past it's mechanical limits and/or cook the voice coil.