Can you increase the efficiency of vintage speakers?


Hello to all...

I have a pair of JBL L25 Prima speakers which have an efficiency of 73 - and I am wondering if I could increase the efficiency of them by rewiring them: I am now powering them with a Parasound HCA-750a ( high current 75w/c/8ohms) power amp, using the pots on the back of the amp...

I'm assuming that rewiring them would change their sound abit as well: has anyone ever experimented with this approach? 


insearchofprat

Showing 1 response by millercarbon

Thought at first 73 had to be a typo. I had a pair of these myself, yellow with orange grills, and they are more like 92-95dB. 73dB is just off the charts low. But then I did a search and found the factory owner’s manual. https://www.manualslib.com/manual/284530/Jbl-Prima-L25.html?page=3#manual

That must be where you got this from. The factory measures 76dB, but notice this is at FIFTEEN FEET! Modern sensitivity measurements are taken at 1m. Rest assured your L25 is a highly efficient speaker.

Anyway no, you cannot increase sensitivity by re-wiring. Oh sure someone will come along and prove me wrong. It’s a sport. You could win a prize. But by and large sensitivity is a function of the native efficiency of each driver and the size and shape and design of the loudspeaker cabinet. You could increase the sensitivity of the JBL L25 only by putting the drivers in a different cabinet.

Which I have done! My first speaker project was a transmission line design by Roger Sanders in which to save money (starving college student) I used the L25 woofers. This wasn’t really much of an increase in sensitivity, but it was a huge increase in terms of bass that was smoother, flatter, and deeper. The native sensitivity of the tweeter is something like 95dB, which is why they have the control to let you turn it down.

Which is what I would do if I were you. Messing with these like I did, transmission line, is a huge amount of work. The high density MDF alone will today probably cost more than you paid for the Primas.

The amp you have now is perfect. The Kenwood mine ran with for decades was 60 watts. So relax. You are fine. Enjoy!