View Full Version : 077's

10-08-2008, 08:50 PM
I have the originals with the blue diaphragms. How can I tell if they or the crossovers are at 100 percent?????

10-08-2008, 10:59 PM
077s : DCR and impedance measurement is a minimum (sine generator with mVmeter or freq analyser), listenning with slow sine sweep at low and "high" levels (listenning at 1000Hz fixed (low level!) for buzzle&rattle), frequency response in a free environment is a good complement but not so easy to do ...,

Be carefull with DC and low frequencies that could be accidently applied on 077 (capacitor link and/or Xover for testing ...)

In addition you can remove the front part (except phase plug !) without any risk (be patient and accurate ;)) to observe dia shape ... (there is no red wax seal on 077 also the original value will be kept constant ...)
Xovers : frequency response measurements with nominal load at output (8 or 16 ohms) and doublecheck crossover frequency at -3dB

Regarding all nominal values for testing, take a look on JBL spech sheets (077 or 2505 and 31xx Xover) on jbl pro site (vintage)