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Old 18th February 2010, 05:03 PM   #1
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Default how to rate a voice coil?

it seems that there is a big varience in ratings for voice coil power handelings. how do speaker manufacturers rate at the power handeling of their speaker. from what i have seen is it seems to be a just a best guess.

example a kicker L7 has a rating of 750 watt and has 2 coils 2x around the former each.

i had a new one made by a very reputable speaker manufacturer and instead of a kapton former he used aluminum and he also used a better quality wire (his words not mine). this seems to be a better stronger coil that will stand up to a lot more punishment . he said this coil can handle around 200 watt before failing and if i put 800 watt to it that it will last 5 mins then explode.

he also sells a speaker that is rated for 1000 watt and this speaker has a 5 inch diameter coil and is 4x around the coil, and i think it has 2 spiders.and has a enourmus magnet.

this guys power ratings are extrodinarily conservative but they seem to be measured in a real world kind of way.

he reccomended that i might try putting in my kicker L7 a coil that is 4x around single coil but a 2 ohm coil since that is the load i am looking for.
i dont know if this is a good idea or not.

are these power numbers rated on the draw of the amplifier in watts or the output of the amplifier in watts? or is it like a space heater where i can apply 750 watt with a voltage all day long before failure?

im confused.
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Old 18th February 2010, 05:13 PM   #2
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from what i have seen is it seems to be a just a best guess.
It's not so much a best guess, because the manufacturer knows what the coil is capable of - they just have a lot of variables to balance in giving an exact number. Power handling is very dependent on enclosures when installed, and a lot of car audio manufacturers like to include an "idiot factor" in their numbers Better to be conservative than have a ton of dissatisfied customers with blown soft parts, especially with the fixation of running at or above rated power thinking they'll get an SPL increase.
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Old 18th February 2010, 05:59 PM   #3
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you dont get a spl increase with more power?
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Old 18th February 2010, 06:11 PM   #4
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Originally Posted by scampo77 View Post
it seems that there is a big varience in ratings for voice coil power handelings. how do speaker manufacturers rate at the power handeling of their speaker. from what i have seen is it seems to be a just a best guess.
They rate the voicecoils to accept "music" rather than a continuous sine wave. Peaks in music can result in a 10db or more increase in power over an average, so your Kicker probably could handle 750W RMS on a temporary basis. However it'd probably die quite quickly given 750W RMS continuous.
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example a kicker L7 has a rating of 750 watt and has 2 coils 2x around the former each.
That's simply to get the correct voicecoil impedance & length of coil in the gap or beyond it so you have a certain amount of Xmax & a given impedance.
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Originally Posted by scampo77 View Post
i had a new one made by a very reputable speaker manufacturer and instead of a kapton former he used aluminum and he also used a better quality wire (his words not mine). this seems to be a better stronger coil that will stand up to a lot more punishment . he said this coil can handle around 200 watt before failing and if i put 800 watt to it that it will last 5 mins then explode.
Now that is realistic. He mentioned it'd take possibly 800W RMS for a few minutes but a continuous 200W RMS
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Originally Posted by scampo77 View Post
he also sells a speaker that is rated for 1000 watt and this speaker has a 5 inch diameter coil and is 4x around the coil, and i think it has 2 spiders.and has a enourmus magnet.
It's that 5" voicecoil that allows it to handle so much power. On the inside of the coil is the pole piece & as it'll be just under 5" diameter there is a lot of metal there to absorb heat given off by the voicecoil. The same on the outer side of the coil there is the magnetic top plate which will again do the same thing.
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Originally Posted by scampo77 View Post
this guys power ratings are extrodinarily conservative but they seem to be measured in a real world kind of way.
Yes he appears to be realistic.
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Originally Posted by scampo77 View Post
he reccomended that i might try putting in my kicker L7 a coil that is 4x around single coil but a 2 ohm coil since that is the load i am looking for.
i dont know if this is a good idea or not.
It might drastically alter the Thiele/Small parameters of the driver so you'd need to measure the driver itself (if you do it) & find out the new specifications so you could design the enclosure correctly.
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are these power numbers rated on the draw of the amplifier in watts or the output of the amplifier in watts? or is it like a space heater where i can apply 750 watt with a voltage all day long before failure?
Amplifier output in Watts RMS into the given load. Please remember though that the speakers impedance will vary by quite a lot depending on the frequency that is applied to it & the enclosure type. It won't sit at 2 ohms (which you stated you wired it for), it might well be near 50 ohms depending on the frequency. If you imagine that it was then you'd only be sticking 30W RMS into the voicecoil when you'd expect it to be 750W RMS.
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Old 18th February 2010, 06:55 PM   #5
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Originally Posted by scampo77 View Post
you dont get a spl increase with more power?
Sorry, i missed this....

At low power yes. As you approach the power limit of the driver the voicecoil heats up & the resistance of the voicecoil increases. This is known as power compression... You might stick an extra 6db of power into the driver (6db would be equivalent to quadrupling the power) but because the voicecoil is getting hotter & hotter & the resistance is increasing due to this heat, you might only get a 3db increase in output.

At low volumes it'll probably produce that 6db with no problems. If you want to understand a bit more about it have a look at this driver here. As you can see it has 2db of power compression at 1KW RMS with a 6" voicecoil. I'm sure if it was a smaller voicecoil it'd exhibit much more compression
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Old 18th February 2010, 09:58 PM   #6
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so aside from changing the T/S parameters what would be stronger a dual coil each is
2x around the former or a single coil 4x around the former? or will they handle the same amount of power?

now what about my power amplifiers? because this is the same problem on the drive side as i do on the driven side. i have JBL BP1200.1 and i have 6 of them. from what i have read these can produce up to 1350 watts of power. what does this number mean (if anything)? and how would it apply to my speaker that can handle 200 watt (according to the coil manufacturer) 750 watt (rms according to kicker) or 1500 watt (peak according to kicker)
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