What does the inductor do

...there was some attempt to make the tweeter path without a capacitor, just substitute it with a high power resistor. The coil shunts the bass as usual. In this video you see a 4 terminal coil, such as the ones used for EMI filtering at mains ( common mode), so it seems that's the case.:scratch2:
 

sumotan

Member
2013-10-16 4:18 pm
Hi picowall,
Yes noted but don't think a power resistor serve the same function. What Im curious is why the introduction of the inductor increases the sound level & also makes it clearer.
Assuming that the tweeter is a 8 ohm unit, this would mean that the henrie value of the coil is pretty high to begin with. I would imagine that the wires for each terminal is wound in opposite direction to each other, perhaps the cancellation of emf etc when signal is applied is what provides the louder & cleaner sound. Just my speculation.

Many thanks
 
Wait...at the beginning of the video there is something labeled as "tweeter" but I haven't seen such a thing. A coil stuffed behind the "tweeter", never seen it.
That's completely nuts! Now you take your cheap speaker and put that coil, well, you make the connections, put the music in behind and see that it moves...clever.

Sumotan, stop watching videos :rolleyes:
 
Wait...at the beginning of the video there is something labeled as "tweeter" but I haven't seen such a thing. A coil stuffed behind the "tweeter", never seen it.
That's completely nuts! Now you take your cheap speaker and put that coil, well, you make the connections, put the music in behind and see that it moves...clever.

Sumotan, stop watching videos :rolleyes:

The coil is just the tweeter voice coil that drives the tweeter cone.
All they did was pinch that coil to make a filter for the other speaker.
However, just putting a coil there would have minimal effect as there is no capacitor or resistor in front to potentially divide the signal.
 
However, just putting a coil there would have minimal effect as there is no capacitor or resistor in front to potentially divide the signal.

Seems to me (and LT Spice) that a series inductor on its own works as a simple high frequency attenuator:

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But the inductor in the video was put in parallel with the speaker not in series.

I didn't quite get what he was doing in the video. It is a 4 lead inductor and to be honest I can't really imagine the signal flow with it hooked up that way. Is it really connected in parallel, or is it two separate windings connected in series (meaning one winding in series with + and one winding in series with -) ?

I do agree that a simple inductor run in parallel would do nothing.
 
In this vid what does the inductor do to the speaker am curious ?
This is not a simple inductor, it is step-up autotransformer ("booster") salvaged from a cheap piezo tweeter. It delivers more voltage to the speaker, but introduces serial resistivity - thus increasing Qts. Step-up transformer wire is extremely thin, not allowing much of power through it.
Bottom line: crap gimmick.
 
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This is not a simple inductor, it is step-up autotransformer ("booster") salvaged from a cheap piezo tweeter. It delivers more voltage to the speaker, but introduces serial resistivity - thus increasing Qts. Step-up transformer wire is extremely thin, not allowing much of power through it.
Bottom line: crap gimmick.

I'm satisfied with that explanation, and the conclusion as well. :)
 
Motorola didn't use this trick, but some loudspeaker manufacturers did incorporate externally their own step-up autotransformer in the "crossover". Today, there are plenty no-name Chinese manufacturers of this kind of "boosted" piezo tweeters. It works OK for tweeters, but usually the piezo disc is unsupported, or it is glued on the wrong places/points - making horrible tweeter. Many models are advertised as a "dome" tweeter, which is deceiving - the dome is glued to a piezo disc, with step-up autotransformer behind it. This one (from Walmart) is typical:
d49155ea-0610-443b-bba9-cdaadc4a027a_1.a3e21118eb63aae2ff71315f9669235e.jpeg
 
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