**********************************************************This is another my big passion, the "sound" reproduced with

High Fidelity!

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Unfortunately for some years now I suffer, above all from the right ear, of attenuation of middle frequencies with low sensibility and I have a modulated tinnitus also.

However this little handicap cannot stop me to listen the good music and above all like I want!

For this reason my passion for the sound, equipments, the homemade power amplifiers and everything to revolves around are always alive with necessary maintenance and every possible improvement.

So, you can see below some my maintenance interventions on loudspeakers, equipments and so on.

That being said, enjoy the show!

Hi Guys!

I had wanted to do it a long time ago but.....anyaway I'm finally on vacation and I have a litte bit time to put in place some modifications, substitutions and calibrations on my old active loudspeakers Audio Pro A4-14 Mk2 that I have bought more or less........thirty years ago!

The first one activity to put in place is the replacement of the original suspension rings of the woofers, Sipe "AS.130 42148", with new foam rings.

In fact after a lot of years of service inevitably the time has destroyed the original suspension that probably it was silicone rubber.

I have replaced the two old electrolitics capacitors on the DC power line with two electrolitics on high capacity to improve the current request on transient.

I have clean the potentiometers and the switches with a specific spray, aboveall I have substituted the "critical" tantalium capacitance on the signal line with new one. 

You can see the photo concerning the position of tantalum condenser.

This is the indication for bias and ACE Bass adjustments, by the way here I have added the voltage value (not indicated on Service Manual) that must be set to -5.5dB 

These simple notes I hope that can help someone to recalibrate well the A4-14 Mk2 active loudspeakers system after the necessary substitutions.

Only one important thing if you want to readjust newly the bias current!

In fact to avoid the possible broken of the final transistors, I strongly suggest to substitute the original trimmers (for both amplifier they are 470 Ohm, but it's better to use 1K) with most reliable mult-turn trimmer and to set it before on max value of resistence to avoid a possible initial high current that could be destructive for final transistors.

In any case, you can substitute the BDW93B and BDW94B final transistors with the "C" version that it's better because allowing 100V of VCE instead of 80V. 

I want to say that with the modifications, aboveall with new capacity to respond to high request of current (the electrolitics capacity it's increases to six time respect of the original) and the "old ladies" are now even more faster with amazing bass response, braked and even deeper (;-))

The S40 are a nice speakers but after over forty years .....

This is the conditions of the original woofers, more or less destroyed, see the foam suspension........anyway the coils are off-axis and touch the magnet bord.

Concerning the tweeters unfortunately we have no good news......in fact the coils on tweeters are broken, like the woofers we need substitution with new components. 

The choice of the woofers goes towards on CIARE production, in fact I had already bought them a some time ago for another project never made.

This is the new woofer, great component with high quality sound. Thanks CIARE!

Concerning the broken tweeters,  the choice fell to CIARE HT263 model, in fact it has a very linear response, the power handling is high and I was very impressed by natural sound of this componet.

Anyway the frequency response, the sensibility is correct and the resonance frequency is far low to the cut-off frequency of crossover filter and finally this tweeter  harmonizes very well with the other components.

The new woofers working well with a great sound and right sensibility.

The next step will be the switches substitution on both cabinet because they not working well.

Done!

Next step the tweeters installation (;-))

I have installed the tweeters and finally the loudspeakers working well now (;-))

Next step........New Acustic Dimension

NAD 302!