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It is currently 11 Dec 2019, 17:40

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PostPosted: 25 Sep 2019, 21:23 
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Joined: 25 Sep 2019, 20:48
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Hi everyone, this is my first post. I've got one of these tweeters https://www.amazon.com/gp/product/B01IC0XR6S wired into the front right speaker outputs on an old amp from Goodwill. The amp works fine when plugged into normal speakers, but when there's only a tweeter wired into the amp's right-speaker output, and I play a 1.5 kHz tone at about half volume, after a bit, the tweeter pops, smokes, and fades out.

The setup is:
* a laptop audio out going to the amp's CD inputs
* the laptop plays a 1.5 kHz sine wave
* amp volume dial is about 1/2. The left/right and forward/rear knobs are on the middle.
* the tweeter is impedance matched with the amp (8 Ohms)
* there's not a crossover in front of the tweeter

In trying to characterize the power that the amp is sending to the tweeter, the results were confusing. With a multimeter (or a scope) on the amp-tweeter leg of the circuit, in series it was seeing milliamps, and in parallel, it was seeing millivolts. Since the tweeter is popping and blowing, and the tweeter has a 300W rating, it would seem that the meter should be picking up way more than milliwatts. (This was with the volume knob on the amp maybe a quarter of the way to max volume).

Any ideas for measurements I can try, or any obvious thing I've missed here in the setup?


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PostPosted: 07 Dec 2019, 16:21 
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Joined: 01 Jun 2013, 09:05
Posts: 855
Its just an idea,

NB as with all things its just suggestions and at your own risk!
If you are wiring the tweeter direct to the amp output its wrong!
It should be fed via a crossover network never direct to the amp output.
The crossover is selective for frequency and is not just about splitting frequencies between midrange and tweeter.
Reason is that the impedance is probably wrong and or there are overtones and spikes appearing on the amp output.
Things like cross over distortion and harmonics.

NB you should never run an amplifier into an open load, if parasitic oscillation sets in it will fry the tweeter and even the amplifier.
Any frequencies that get through to the tweeter that are outside the range of operation will blow it very quickly.
One other thing is I have never seen a perfect power supply so if its not through a crossover you have hum which is the same as low frequency to the tweeter. Without a load on the amp output to sink any transients you could get all sorts of problems.

Another thought, is the tweeter rated at continuous power or transient power. Its not "normal" to run a tweeter at continuous set frequency.

Regards
M. Gregg

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