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Old 11-21-2009, 10:14 PM   #1
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Smile How many volts does a 6 ohm speak give out?

hello, i'm wanting to add some led lights on my surround sound speaks, so when i play music, the lights blink to the beat of the music..

i'm going to eventually buy 10 of these:

http://www.amazon.com/Logisys-LT400R...d_bxgy_e_img_b

and mount them over or below my speakers.. yeah i know there pc fans, but it's easier and cheaper than buying seperat led lights, and resistors, and then soldering and mounting them in the right positions... pc cooling fans are cooler looking anyway

my speakers are 6 ohms
i'm planning on striping the speaker wire to add the led's

SO! i have a pc fan next to me and it's 12 volts (but no leds), i'm assuming that most pc fans are 12 volts, right?

and, how many volts is a 6 ohm speaker?
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Old 11-22-2009, 08:32 AM   #2
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Default Re: How many volts does a 6 ohm speak give out?

The audio signal is an alternating current not flat line DC. DC is required to drive the fans and most fans run on 12 volts. If you put the fan across the speaker will will not only have the wrong power signal, but there won't be enough to push the fans.
Besides you'll change the impedance of the load and make the speakers sound like crap. Not to mention the load on the amp will be out of the range it was designed for and as a result you could burn your amp up.
IMO you'd do better to look at sound activated CCFL or led sticks. You'd have to have a central power supply and run a two conductor cable to each unit. Just strip the wires close to the power plug on the sound controller box and attach the leads from the power supply.
Besides even if you could make it work like you want it, why in the heck would you want to listen to all that fan noise?
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Old 11-22-2009, 01:31 PM   #3
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Default Re: How many volts does a 6 ohm speak give out?

the fans are super quiet, and i thought that the fans would be blinking on and off with the music to

but, sounds more complicated than what i'm capable of doing, eh, i'll be fine without fancy led lights..
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Old 11-22-2009, 06:07 PM   #4
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Default Re: How many volts does a 6 ohm speak give out?

"How many volts does a 6 ohm speak give out?" It depends on the SPL applied to the speaker cone.

The fans and LED require DC current. So the current from the Amp will need to rectified to produce a DC current for the LED's and fans. At low volumes the reverse current may not damage the LED's but they won't last at high volumes. Also at low volumes the LED's may work and the fan won't spin.

And you need to ensure that when you do turn up the wick you don't over power the LED's and fans. So after rectification you will need some kind of regulation. This can also ensure that at high volumes the LED's and fans still flash to the beat. You may choose to have them on all the time at full volume also.

It's possible.
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Old 11-24-2009, 06:36 PM   #5
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Default Re: How many volts does a 6 ohm speak give out?

i'm not that technical with stereos, speakers and stuff, so, what is SPL?

how could i convert it to DC? and wouldn't a simple resistor work to limit the power so i don't burn out my LEDs?
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Old 11-25-2009, 12:36 PM   #6
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Default Re: How many volts does a 6 ohm speak give out?

Quote:
Originally Posted by peteyboy22 View Post
i'm not that technical with stereos, speakers and stuff, so, what is SPL?

how could i convert it to DC? and wouldn't a simple resistor work to limit the power so i don't burn out my LEDs?
SPL = Sound Pressure Level.

You will need to convert the output of the amplifier from AC to DC. The LED's are polarity sensitive devices and although they will operate at low volume levels, where the reverse AC cycles across the diode are small, as you increase the output from the amp the large reverse AC cycles will cripple the LED. Remember also that the 12V fan requires a DC power supply. Very simple rectification would involve a single diode. Although you could use bridge rectification which would make use of the negative half of the AC output. This would be the first thing I would do for this experiment. Put it across the amp terminals and measure the DC output across the rectifier, with and without the speaker connected, gradually increasing the amp volume from zero to full.

Once you have your measurements then you can take it from there.
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