tweeters with resistors

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dalfe5

Member - Posts: 19

Joined: June 20, 2006

Posted: October 06, 2006 at 3:40 PM / IP Logged

Could someone please explain why a resistor is used on some tweeters. I know about a capacitor but not why a resistor. From my understanding of a resistor it is to limit the power coming into it to a lower power coming out. I bought a pair of tweeters with a rating of 100w RMS but to use them with power over 60w you would need a resistor that is 16ohm/25watt. If it is used to lower the power to the tweeter then it's RMS shouldn be 100w. Alson the power rating was for the pair so anything over 60w per pair (30w per speaker).

dalfe5

Member - Posts: 19

Joined: June 20, 2006

Posted: October 06, 2006 at 4:37 PM / IP Logged

that doesnt help me understand. will you still have the same amount of WATTS coming out of the resistorand going to the tweeter? not trying to be an @$$ but just wanted to try to understand. So if it lowers the AC voltage the tweeter will still see the same amount of power?

hemanjoyman

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Joined: August 18, 2006

Location: United States

Posted: October 06, 2006 at 4:48 PM / IP Logged

Actually, I believe resistors limit the amount of current, not voltage. If there is a resistor in series with the tweeter, the tweeter will see less power as the resistor will dissipate some of the power.

geepherder

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Posted: October 06, 2006 at 7:01 PM / IP Logged

Easy, killer. No one was trying to step on your toes. Wattage, resistance, voltage, etc. are interrelated. Yes, the resistor eats up some of the power and voltage, which limits the current to the tweeter. Basice ohm's law tells us that if resistance (impedence) goes up, current goes down. In a series circuit, if you have more than one load (a tweeter as well as a resistor), the voltage will be split between them.

Let's use this example: your daytime running lights probably use your high beams. Why are they dimmer than turning on your high beams with the headlight switch? They run at a lower voltage because they are connected in series instead of parallel (using relays, etc.). They don't both use 12 volts, but rather 6 volts each, since they are connected end to end.

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stevdart

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Posted: October 06, 2006 at 8:43 PM / IP Logged

Good info on the daytime headlights, geepherder. Now I know...

(I love that feeling of knowing something that all those other drivers don't know.)

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geepherder

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Posted: October 06, 2006 at 11:41 PM / IP Logged

Nouse, my post was not directed towards you, but the original poster who jumped your case. I guess you posted while I was still typing.

Yeah Steve, I've never been a fan of drl's so I did some research on how to disable mine. I had to remove a relay, pop the cover loose, and isolate the contacts with tape.

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DYohn

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Posted: October 07, 2006 at 10:40 AM / IP Logged

Chill out please, gentlemen.

The purpose of resistors in a speaker circuit is to match its sensitivity to other speakers being used. It generally has nothing to do with protecting the speaker from over-power, although I suppose it could be used for that purpose. If a tweeter operates at 91db sensitivity and you want to use it with a woofer that operates at 88db sensitivity, for example, you need to reduce the tweeter's output by -3db. This is done by using resistors (or an L-pad, which is a variable resister bank.) Resistors work by changing the voltage and current distribution in a given circuit, which changes the power utilization by the speaker.

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dalfe5

Member - Posts: 19

Joined: June 20, 2006

Posted: October 09, 2006 at 9:42 AM / IP Logged

the tweeter i am talkin about is rated at 100 watts rms.

on the instructions it says for use with systems over 60 watts rms use a 16ohm/25watt resistor. thanks for all of your help.

"killer"

DYohn

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Posted: October 09, 2006 at 11:05 AM / IP Logged

dalfe5 wrote:

the tweeter i am talkin about is rated at 100 watts rms.

on the instructions it says for use with systems over 60 watts rms use a 16ohm/25watt resistor. thanks for all of your help.

"killer"

What's the tweeter? What kind of crossover are you using?

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dalfe5

Member - Posts: 19

Joined: June 20, 2006

Posted: October 09, 2006 at 12:04 PM / IP Logged

it was a power acoustic NB-2. it had crossover built-in. but also needed a resistor. i returned it because nobody in town carried the resistor that was needed. did not even find the exact one stated online. close but not same. i tried tech support for power acoustic but he said it was for frequency to block the lower frequencys but i thought that is what a capacitor(buit-in crossover) was for. i thought power acoutsic was a dec ent brand but after finding them online for around ten bucks guess not.

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