I recently replaced a diaphragm on a JBL 2426 driver. Included with the diaphragm, a genuine JBL part, was a little folder with "Warning" printed on it. Inside it said: "This part is NOT self-centering! This product should be installed by an authorized factory trained technician." Then they went on to talk about the centering of the voice coil within the magnetic gap and special test equipment. Really? I just stuck it in and it worked- just as I have done with many other ones over the years. Was that some kind of generic waiver, or am I doing something stupid?
HF Diaphragm Question
- Thread starter Chuck Simon
- Start date
Re: HF Diaphragm Question
If not accurately centered, the coil can rub against the magnet causing poor sound and premature failure. If it's not perfectly centered, but not touching the sides, the quality of sound might change slightly from spec. Might not be enough to notice.
The only concern I'd have would be if it was close to rubbing, but not noticeable in testing. When the coil heats up during use, it could end up rubbing and destroying itself.
If not accurately centered, the coil can rub against the magnet causing poor sound and premature failure. If it's not perfectly centered, but not touching the sides, the quality of sound might change slightly from spec. Might not be enough to notice.
The only concern I'd have would be if it was close to rubbing, but not noticeable in testing. When the coil heats up during use, it could end up rubbing and destroying itself.
Re: HF Diaphragm Question
You may or may not have properly installed the diaphragm. It's been a long time since I've had to replace one, but in essence you finger-tighten the screws and then do a sine wave sweep. The instrumentation is to show the distortion or impedance change from a VC that rubs or is otherwise not centered in the gap. The screws are finger tight so you can gently move the assembly while observing the changes; tighten them down when you're sure everything is correct.
You may or may not have properly installed the diaphragm. It's been a long time since I've had to replace one, but in essence you finger-tighten the screws and then do a sine wave sweep. The instrumentation is to show the distortion or impedance change from a VC that rubs or is otherwise not centered in the gap. The screws are finger tight so you can gently move the assembly while observing the changes; tighten them down when you're sure everything is correct.
Re: HF Diaphragm Question
Interesting. There doesn't seem to be much room for movement once the screws are in. I never realized there was any adjustment needed. I guess I have done about a half dozen of them over the years and have been pretty lucky!
Interesting. There doesn't seem to be much room for movement once the screws are in. I never realized there was any adjustment needed. I guess I have done about a half dozen of them over the years and have been pretty lucky!
Re: HF Diaphragm Question
I do the same as you, put them in gently and tighten them down, they will be fine.
I do the same as you, put them in gently and tighten them down, they will be fine.
Re: HF Diaphragm Question
The "quick and dirty" method is to apply a sinewave-say in the range to 500-800Hz-but don't make it to loud. Install the diaphragm with screws almost tightened all the way.
Now "slide" it to one side. You may hear a buzz come up-which is a harmonic due to the rubbing.
Depending on how much "slack" you have-you may be able to move it around a bit or not. Figure out how much "elbow room" you have. Figure out where the diaphragm is in the middle of the buzzes and tighten it down.
Then sweep the freq around (using mostly lower freq tones that cause the diaphragm to move more) and see if you hear any harmonics "pop up".
Some times you get lucky when you just "put them in". Other times not so lucky.
Some are easier than others. The factory and good after market units (Radian for example) tend to be easier to align. I ahve tried (years ago) several of the "imports" and had a very hard time getting them lined up-and then they still did not work (or last) as good as the better units.
The "quick and dirty" method is to apply a sinewave-say in the range to 500-800Hz-but don't make it to loud. Install the diaphragm with screws almost tightened all the way.
Now "slide" it to one side. You may hear a buzz come up-which is a harmonic due to the rubbing.
Depending on how much "slack" you have-you may be able to move it around a bit or not. Figure out how much "elbow room" you have. Figure out where the diaphragm is in the middle of the buzzes and tighten it down.
Then sweep the freq around (using mostly lower freq tones that cause the diaphragm to move more) and see if you hear any harmonics "pop up".
Some times you get lucky when you just "put them in". Other times not so lucky.
Some are easier than others. The factory and good after market units (Radian for example) tend to be easier to align. I ahve tried (years ago) several of the "imports" and had a very hard time getting them lined up-and then they still did not work (or last) as good as the better units.
Re: HF Diaphragm Question
Thing is, a majority of us don't have these tools,,
~:-(~:sad:
Thing is, a majority of us don't have these tools,,
~:-(~:sad:
Re: HF Diaphragm Question
A sine wave generator exists on many analog mixers and almost every digital mixer.
Thing is, a majority of us don't have these tools,,
A sine wave generator exists on many analog mixers and almost every digital mixer.
Re: HF Diaphragm Question
Also, if you have a computer, you'll have the tool.
Edit: And of course there are lots of apps for iPhone, iPad etc.
Also, if you have a computer, you'll have the tool.
Edit: And of course there are lots of apps for iPhone, iPad etc.
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Re: HF Diaphragm Question
As others have said-you can get sine waves from all over the internet.
But having a basic analog sinewave generator is a good thing to have if you are in "audio". You can use it for HF alignment-or sweep low to check for subwoofer cabinet buzzes/rattles and all sorts of other testing. A sweepable one is better than a steeped one.
You can find them used for uner $100.
Not much to spend for a very useful tool-if you are serious about your craft.
Thing is, a majority of us don't have these tools,,
As others have said-you can get sine waves from all over the internet.
But having a basic analog sinewave generator is a good thing to have if you are in "audio". You can use it for HF alignment-or sweep low to check for subwoofer cabinet buzzes/rattles and all sorts of other testing. A sweepable one is better than a steeped one.
You can find them used for uner $100.
Not much to spend for a very useful tool-if you are serious about your craft.