Help a beginner with diagnosing Lancer 77 ailments....

Let me first thank you all for sharing so much information and assistance. I just acquired a pair of Lancer 77 speakers this weekend. I'm no stranger to small issues like replacing surrounds, and even fixed a shifted magnet on one of my KEF 107 drivers, but these JBLs are puzzling me.symptoms:-some light popping / cracking in the tweeters-if the volume is raised beyond a quiet level, I note that there is mild distortion, and with just a small amount of increased volume drivers seem to be moving in and out uncontrolled at a very high rate. I immediately cut the volume when I saw this happen.i would find it hard to believe that all drivers are bad / blown. How can I tell if this is a crossover problem vs driver issue?i do not know the history of these but would like to resurrect them if possible. If that means replacing drivers I will most likely not invest the $ to fix them :(thanks all!

Honestly, the driver cones moving excessively sounds like subsonic oscillation. Are you using a turntable; and if so, is it isolated from the floor etc.?

Francis

on both speakers ?
all sources ?
try different amp.
switch wires to other speaker.
check polarity. etc.

AFAIR ..the 77 has a passive radiator.
white/yellow Lansaloy surrounds ?
very likely shot , even if they look OK.

Ok, so you were right about the subsonic issue... I had faced this before but in my haste I forgot about that. However, definitely still need some kind of work.

Tested while playing iphone via an aux input through my 2235b marantz (feeding MC 2505 from the tape out) and works perfect with the kef 107. Switched to the JBL Lancers and face the following:

1. Mid / high seem fine (very nice tone)
2. Strong lack of bass in both units (not the case when same system hooked to my KEF 107). yellowed surrounds seem intact but I do see one crack on a driver so yes - need replacing.
3 rattling coming from one driver (radiator) although this is slightly alleviated when I lay the speaker on its side. I'm guessing if the surrounds are bad this could be the cone sagging to one side in the basket???

is it possible that the crossover could cause lack of bass?

Sorry for for the delay in responding, I've been traveling on and off.

The lack of bass is caused by the once very flexible lansaloy surrounds turning to crust