2015-12 Repair Solarvox speakers

This was to be an easy one. HA! Anyway... I have a number of HiFi speakers from the '60s - '80s and they take up space. Sorted them out and found this pair have a sound I like but a blown tweeter.

The label on the back is interesting...

I found an appropriately rated tweeter from JayCar and fitted it. It sounded very very bright. A series resister would be all that's needed to reduce the level of the modern more efficient driver but doing that by listening and changing the resistor seemed fraught.
I decided to try measure it :

• Make sweep and noise files and play them  on the left then right channels
• Use the Tascam recorder to grab a recording 
• Have a look at the spectrum of the recordings and adjust until they match.

Generate tone:  sox -n sweep1.wav synth 10 sine 10-20000
Generate noise:  sox -n wn1.wav synth 10 whitenoise

Then play it back and record it on the tascam.

Script:

while true ; do for F in *.wav ; do echo "Playing [ $F ]" ; play $F ; sleep 1 ; done ; done




Note the rug on the chair to create a special sound proof recording area.



After some trial and error the spectrogram of white noise seems the best way to see what's going on. Got these from
sox infile.wav -n spectrogram outfile.png
after trimming the tascam recordings down to just the white noise burst.

This is the new tweeter 

This is the original.













An 8 Ohm resister seemed to be about right:

I did both speakers as the high end is clearly better.