Misconceptions about power being divided between speakers

[grampi 10+ year member]

I was talking to a guy yesterday who was trying to explain to me how if a mid and tweet (comps) were running off of an amp channel that was providing 75 watts per channel, that 75 watts would be divided between the mid and tweet. I told him if the power was going through a crossover network that divided the freqs (lets say the twett was only getting 4K and above and the mid was only getting freqs from 4K and below) the mid and tweet would actually be getting 75 watta each. He didn't believe this. Who is correct?

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[helotaxi 5,000+ posts]

You are.

 

[Etac 10+ year member]

from what i heard and correct me if im wrong

crossovers rob power (approx 15%) and it does split the freqencies but if you're playing say 200 watts at 80 hz on the mid - it wont take 200 watts to move the tweeter at like 10k hz at the same volume....

 

[mrwigglezdj 10+ year member]

I was talking to a guy yesterday who was trying to explain to me how if a mid and tweet (comps) were running off of an amp channel that was providing 75 watts per channel, that 75 watts would be divided between the mid and tweet. I told him if the power was going through a crossover network that divided the freqs (lets say the twett was only getting 4K and above and the mid was only getting freqs from 4K and below) the mid and tweet would actually be getting 75 watta each. He didn't believe this. Who is correct?

well i belive you are wrong, the cross over is not a amp, so how in the gods green earth could each be geting 75 watts each off of a single chanle

i think its more less the freq being played will detrmin the power each item gets when connected to a cross over?...

 

[grampi 10+ year member]

from what i heard and correct me if im wrong
crossovers rob power (approx 15%) and it does split the freqencies but if you're playing say 200 watts at 80 hz on the mid - it wont take 200 watts to move the tweeter at like 10k hz at the same volume....

I don't think crossovers eat that much power, it's probably actually less than 5%. Don't know about the rest of your statement though. From what I understand, an amp pushes a certain amount of power from 20-20K hz. If an amp is pushing 200 watts at 80 hz, it's also pushing 200 watts at 10K HZ.

 

[delvryboy 5,000+ posts]

well i belive you are wrong, the cross over is not a amp, so how in the gods green earth could each be geting 75 watts each off of a single chanlei think its more less the freq being played will detrmin the power each item gets when connected to a cross over?...

full power at different frequencies.

 

[bikinpunk 10+ year member]

full power at different frequencies.

easiest explanation.

 

[Etac 10+ year member]

I don't think crossovers eat that much power, it's probably actually less than 5%. Don't know about the rest of your statement though. From what I understand, an amp pushes a certain amount of power from 20-20K hz. If an amp is pushing 200 watts at 80 hz, it's also pushing 200 watts at 10K HZ.

i would like to know the answer to this second half of this statement - i never mind being corrected and im not arguing with you - i just didnt think it was like that... im not saying it isnt capable of doing that - but since the tweeter is so small i didnt think it would need that much power to move the cone at the same volume

 

[Scoobydoo 5,000+ posts]

the mid would draw more power to play at the lower freqs

 

[Etac 10+ year member]

^hence why the higher you set the crossover point - usually the more power a set of speakers can handle.. correct?

besides over excursion

 

[mile098 10+ year member]

they dont get the same power..yes the crossover eats up power but not that much(at least the passive ones)...try going active and putting the same ammount of power into the mid and tweet(lets say the system is rated at 100 rms) and see what happens...

edit: i mean put a 100 rms into a midbass and the tweet, set the gains equaly to both channels, and listen to it for a couple of hours

 

[T3mpest 10+ year member]

crossovers don't eat up power at all, an inductor will simply cause an impedence spike so that the amp cannot produce power at those frequencies. That will dissapate some of it as heat,but when we are talking about speakers less than 1% effecient, who really cares? A resistor will actually "eat power" though. Such as the attenuation switch on a tweeter.

 

[helotaxi 5,000+ posts]

The cap in series and inductor in parallel with the tweeter will begin to increase their impedance below the resonance of that circuit (depends on the value of the cap inductor and impedance of the driver at the given freq). The increased impedance attenuates the output of the tweet by cutting the power going to it. The inductor in series and cap in parallel with the mid do the same thing above circuit resonance. The crossover loses power around the crossover freq but is fairly transparent, power wise, well above and well below. With the tweeter and mid paralleled by the crossover, the effect is a fairly smooth division of power between the two.

While the amp is capable of running the same amount of power to the tweet as to the mid, and the crossover usually won't stop it from doing so (barring an attenuation circuit of some sort) most music has a lot less up high compared to down lower. Less energy present in the signal means less power going to the driver. Look at a spectral analysis of a typical song. It slopes fairly significantly from the lows down to the highs. Play pink noise though and prepare for your ears to bleed.

 

[kmanian 5,000+ posts]

The cap in series and inductor in parallel with the tweeter will begin to increase their impedance below the resonance of that circuit (depends on the value of the cap inductor and impedance of the driver at the given freq). The increased impedance attenuates the output of the tweet by cutting the power going to it. The inductor in series and cap in parallel with the mid do the same thing above circuit resonance. The crossover loses power around the crossover freq but is fairly transparent, power wise, well above and well below. With the tweeter and mid paralleled by the crossover, the effect is a fairly smooth division of power between the two.
While the amp is capable of running the same amount of power to the tweet as to the mid, and the crossover usually won't stop it from doing so (barring an attenuation circuit of some sort) most music has a lot less up high compared to down lower. Less energy present in the signal means less power going to the driver. Look at a spectral analysis of a typical song. It slopes fairly significantly from the lows down to the highs. Play pink noise though and prepare for your ears to bleed.

Thats a fact jack! Well said