I’m finding that the tweeter in one of my monitors is intermittent. At low levels, one speaker sounds dull — so the high frequencies seem to be skewed to the other speaker. If I turn up the volume going into the speaker it starts working properly and will generally stay that way for a good while, even if I turn it down again. So it’s usable but clearly not ideal. Is the tweeter broken or could something else be going on here?
John Hoyle
SOS Technical Editor Hugh Robjohns replies: I’m afraid the chances are that your tweeter is broken, although there are a few other (less costly) things to check first. Clearly, there’s an intermittent connection somewhere, and it’s quite common for a corroded connection to develop high resistance (and thus reduce signal level dramatically), but then break down (temporarily) when the signal voltage exceeds a certain level — hence causing the connection to work properly again for a while.
The challenge is to identify which connection is playing up, and as there are likely to be several possibilities in a monitoring signal chain, you’ll need to work through them all carefully. All you need to do is swap the two channel connections stage by stage to see if the fault stays with the suspect speaker or moves to the other one.
So, for example, swap the outputs from the interface feeding the monitoring controller (if present), and have a listen... then swap the inputs at the monitoring controller itself, then the outputs feeding the power amp or active speakers, then again at the speakers (or the speaker cables). You may have to listen for a while after each swap to see if the problem reappears.
When disconnecting gear to trace problems, it’s a good opportunity to apply a contact cleaner such as Caig’s Deoxit D5.Often just disconnecting and reconnecting plugs is enough to wipe corrosion off the terminals and restore normal working, at least for a while. However, if you’re going through the faff of disconnecting and reconnecting everything anyway, I would recommend applying a squirt of a contact enhancer like Deoxit D5 to each connector as you go along, since it helps to prevent corrosion and tarnishing.
If the fault is in the tweeter itself none of this cable-swapping will make any difference, of course, but at least you’ll have confirmed the problem.
In an active speaker it’s also possible that internal connectors might be the problem. If you are qualified to do so, you could check those as well, bearing in mind the inherent dangers of working inside mains‑powered equipment and the warranty implications. That said, it is not uncommon for the very delicate lead wire coming from the moving coil in a tweeter to fracture, or even for part of the coil itself to become damaged, if the tweeter is subject to excessive levels (even briefly).
Also, be aware that, depending on the manufacturing tolerances, it may be necessary to replace the tweeters in both speakers to ensure a good stereo match. The manufacturer or their service agent will be able to advise.