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Lighting up the inside of a subwoofer

Hey everyone,

I am an undergrad in ECE and I am working on building the box for a double vented 500W subwoofer. I want to light up the inside with some kind of blue light so that it shines out the side (thick clear material) and through the two vents. I also want to put orange LEDs around the outside of the speaker (I go to the university of illinois, school colors). I want the lights to pulse with the bass of the subwoofer though. I haven't taken enough courses to design my own circuits yet, so I have been googling for hours looking for circuits that involve a mic and a low-pass frequency filter. I have a few questions that I am hoping someone can give me insight on:

1) Will there be a problem with using a microphone inside the box? I am wondering if the lights will come on out of phase with the beat and whether or not it will just always be on because its inside the box.

2) Would it be smarter to tap into the two wires going into the woofer instead of using a mic? And if so, will the high current be a problem for such a simple circuit? Would it be more effective to put it in series or parallel with the woofer? Are there overload concerns with hooking it up to a 500w amp?

3) Am I going about this all wrong? I am open to advice and to alternative to what my current thoughts are. I am also unsure of how to power the circuit if its a seperate one with a mic. I don't know if tapping off the transformer is such a good idea, seeing as its a 250$ amp.

I appreciate any feedback. Thanks for your time.

Reply to
Jacob.Block
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Repost to alt.binaries.schematic.electronic and I'll send you some info

Reply to
Lord Garth

you'd need one that rated for very high SPL.

???

parallel (with large resistors in series with your circuits input). problems most unlikely.

getting in series with the sort of current needed to put 500W into a 8 ohm load is'nt worth the bother,

google for colour organ.

Bye. Jasen

Reply to
jasen

What is ECE? What year are you in?

John

Reply to
John Larkin

Here's an interesting experiment you can try that may give you what you want with a bjt.

Wind some (10 ?) turns of hookup wire around one of the wires that connects the subwoofer speaker to the circutry that drives it to make a pickup coil. Then do this:

PNP + 12 --------------------- ---+ e\\ /c | - | ------ ----- | [1K] |Pickup|--|~ +|---[1K]---+ | | | | BR | a| [LED] | Coil |--|~ -|---+ [D1] | ------ ----- | | | | [D2] | | | | Gnd ----------------+------+----+

If the LED lights at all the levels of audio that you will use, you're in business. You can use the output at the collector to drive the gate of a mosfet, and switch however many LEDs or circuits you want.

Ed

Reply to
ehsjr

If you wind turns around another wire, the coupling is zero.

This circuit blows out the PNP as soon as you turn on the +12.

John

Reply to
John Larkin

Right. It is wound around one wire.

Thanks! Started with an NPN, then changed to PNP - forgot to chage the rest around. Correction:

PNP + 12 ---------------+------+---- ---+ | a| e\\ /c | | [D1] - | ------ ----- | | | [1K] |Pickup|--|~ +|---+ [D2] | | | | | BR | | | | | Coil |--|~ -|---[1K]---+-----+ | ------ ----- [LED] | Gnd ----------------------------------+

Reply to
ehsjr

Still zero.

John

Reply to
John Larkin 

--
Winding it around the single wire, using the wire as the core won\'t
work either.

The sensing coil needs to be wound like a solenoid and then wrapped,
like a toroid, around one of the wires feeding the subwoofer.  It
then becomes the secondary of a current transformer, the primary
being the wire feeding the subwoofer.
Reply to
John Fields

Thanks to both you and JL. So the experiment would fail, unless he did it like that.

Now the question is why is there 0 coupling? What do I need to read/study to gain the understanding you & JL have on this? I've got an incorrect idea(s), or a missing concept(s) somewhere.

Ed

Reply to
ehsjr

Well, there's all that em field theory and stuff, but the simple statement is that parallel wires couple magnetically, and perpendicular ones don't.

And even if the wires are arranged to share flux loops, namely to couple, air-core coupling at audio:bass frequencies will be tiny.

The drive to the speakers is typically huge, so why not just drive the led's directly from the amp output?

Even better idea: stop doing silly light-organ tricks and spend the time studying electronics. If the op is a electronics student and can't figure out how to do this yet, he's in trouble.

John

Reply to
John Larkin

One is as good as the other.

Bye. Jasen

Reply to
jasen

It takes parallel (or atleast non-perpendicular) wires to make a (air-core) transformer if you wind the sense wire round the power wire your windings are mostly perpendicular to the otther wire and you won't pick much signal up.

Bye. Jasen

Reply to
jasen

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