There is now a chance that I may need to change out the diaphragm in addition to the dampening pad on one of my 2441. Is there wisdom in changing out the diaphragm in the other 2441's even if it is working so both can match? Is the sound of the JBL-D16R2445 diaphgragm they sell similar sounding the original diaphragms in the 2441? I had read some posts stating that radian audio's aluminum/beryllium(?) diaphragms might sound closer to the original.Thank you in advance!
It just gets harder and harder to make a good matched pair of drivers these days.
Back when JBL’s quality control was tight I would have said replace both because the old diaphragm would possibly not sound as good as the new one. Now that is rarely the case. Now days some of us will rebuild six or more like compression drivers at once swapping parts back and forth and measuring over and over in the hopes of being able to best pair them.
Aluminum diaphragms don’t match the Ti in sound character. The SL diaphragms sound better. At this point the Radian aluminums might be your best bet and at that point I would swap them in pairs.
Also I have had trouble getting JBL diaphragms made in this century getting the voice coils not to rub in the tighter magnetic gaps of the AlNiCo motors.
While diaphragms are “field replaceable ” it’s not often easy to get them truly right.
There is plenty of information and help here if you want it.
Barry.
If we knew what the hell we were doing, we wouldn't call it research would we.
Hi Barry, this is so incredibly helpful thank you!I was able to take apart the back today to replace the foam and upon inspection, saw a small dent on the diaphragm. It seems the dent did not puncture through as is no hole in the diaphragm which I imagine is why it plays well most of the time. However, would this dent cause any issues like a slight buzzing at specific high frequencies?Originally Posted by 1audiohack
It just gets harder and harder to make a good matched pair of drivers these days. Back when JBL’s quality control was tight I would have said replace both because the old diaphragm would possibly not sound as good as the new one. Now that is rarely the case. Now days some of us will rebuild six or more like compression drivers at once swapping parts back and forth and measuring over and over in the hopes of being able to best pair them. Aluminum diaphragms don’t match the Ti in sound character. The SL diaphragms sound better. At this point the Radian aluminums might be your best bet and at that point I would swap them in pairs. Also I have had trouble getting JBL diaphragms made in this century getting the voice coils not to rub in the tighter magnetic gaps of the AlNiCo motors. While diaphragms are “field replaceable ” it’s not often easy to get them truly right. There is plenty of information and help here if you want it.Barry.
Can you see from the other side if there is any evidence that it was touching the phase plug at the dent? Or anywhere else?
Those diaphragms are anything but pistonic so it’s possible any deformation could cause a problem but in my experience it appears the damage is quite small and to be unlikely to be problematic.
Do you have a way to run these with a small trustworthy amp and frequency generator?
Barry.
If we knew what the hell we were doing, we wouldn't call it research would we.
Hi Barry, I didn’t look at the other side bc because I was worried about dissembling the diaphragm and not reinstalling it correctly. I had read that the screws had to be tightened to a specific torque value. I’m not sure if this is true or not but didn’t want to risk it without confirmation. I don’t have a small trustworthy amp/frequency generator. However, I saw on YouTube that someone using a 3.5mm headphone cable to bare wire that hooked to the positive/negative of the diaphragm and using a frequency generating app - would this work?
Btw how do make your paragraph breaks? I respond and it when I submit my response everything gets put together into a single paragraph.
Let’s see if I can remember the formatting thing: Go to settings, top right of the maroon page by your profile and log out, then to general setting in the drop down tree on the left, then almost to the bottom of the page there are three text editor setting, the bottom most basic is it, I think.
You could get some noise out of your driver with a head phone amp but I don’t know if you could get enough drive to really test it.
I use an old Crown D45. At 300 Hz you can clip that amp and not instantly kill a large format driver.
I didn’t notice the screws were still in making it obvious the diaphragm was still in the driver. Sorry.
Physically manipulating the diaphragm and tightening screws in odd orders is part and partial to getting these to behave. An experienced tech can get these to behave by ear with a signal generator and amp.
Qualifying measurements are not usually part of the job unfortunately. There has to be someone in every state that can perform these services, finding the good guys, that’s the trick.
I know a great guy in Wixom MI. That is as close as I know to you.
Anyone else here close to NY someone could refer?
Barry.
If we knew what the hell we were doing, we wouldn't call it research would we.
This is an excellent phone app for anyone who wants to test speakers of any kind. The basic app does everything you would need for what you're trying to accomplish here but some of the add ons are pretty useful if you want to explore the rabbit holes. You can use any amplifier to test a compression driver including your main listening amp as long as you set your signal generator to sweep in a range that the driver can handle AND you control the level. Surprises kill more speakers than just about anything else.
https://www.studiosixdigital.com
I've seen considerably worse vampire bites with no discernable effect on the sound.
These are caused by somone not holding on to the spade lug when removing/replacing it. The spade lugs are ferrous and are instantly drawn to the magnet through the diaphragm. What you see is the resultant dent.
Barry, thank you again! Fingers crossed, my formatting will hold.
Reading your response, reassures me that I made the correct decision to not mess with the diaphragm at this time. However, I'm very curious, is there a way to learn how to calibrate the diaphragm? Or where I could start learning? I have a Bogen DB20 (in need of a restore). Would something like this work as a tone generator? I think this is something I have to work my way up to.
In the mean time, I would love the information of the guy in Wixom, MI. I pass through Detroit a couple times a year so it wouldn't be a stretch to drop something off if needed. Or even mail it if its easy to be posted.
Thank you for the advice and app recommendation - it's crazy that something like this exists for the iphone/ipad. Would you just use an rca to 3.5 to hook into an aux input to use the signal sweep?
Toddlin! I didn't realize that the spade lug needed to secured due to the magnet - luckily, nothing happened when I was separating the back to remove the foam. However, Your response actually put me at ease regarding the vampire bite. After putting everything back together the driver sounds great - still buzzes slightly on certain records at higher frequencies - however, overall it nice.
BTW, your 3115's are used everyday and have been (are being) thoroughly enjoyed!
Yes connect the smart phone headphone jack output to the amp with a mini plug to RCA plug adaptor cable. Works fine although may be about 6db higher output than most hifi equipment so again start low then turn the phone output up to the desired level.
Your instance of distortion at a few frequencies well above the low end of the driver response may be dirt between the diaphragm and the phase plug so probably time to remove the diaphragm entirely and vacuum out the phase plug. Also tug on each ring of the phase plug with a finger nail. It's not unheard of that they become loose and need to be reglued or replaced.
My procedure for installing replacement diaphragms in 2440, 2441, 2445s, EV DH1s, dozens of assorted drivers over the decades is not what I was taught at JBL recone training so probably heresy here on the forum but it starts with the factory version. Install the diaphragm and with the securing screws only finger tight run a 500 hz tone into the diaphragm at a moderate level. Twist the rim of the diaphragm back and forth til you hear distortion and then back until you find the spot where distortion disappears. Sweep the tone down to about 400 hz and up to about 2khz confirming that no distortion is found. Keep iterating til satisfied then tighten the screws in opposing pairs. The non-factory next step if you can't find a no distortion point. Remove the diaphragm and ream out the mounting screw holes in the plastic rim for more 'play' in the mounting and return to step one. Not for the feint of heart if you have one replacement diaphragm and one driver but if you have an entire stage full of monitors with ruined diaphragms and a show that starts in a couple of hours it gets the job done.
I am right in line with Riley.
I was thinking that for less than even shipping the 2441’s somewhere you could buy a 2445 or 2446 with a Ti diaphragm that are not easily damaged and work with that a while until you are comfortable with working on something you care about.
You can put 20 Watts at 300 Hz to it and let the diaphragm bang on the phase plug, loosen the screws and push the diagram around and get a feel for what that all sounds like with near zero risk.
Barry.
If we knew what the hell we were doing, we wouldn't call it research would we.
How far are you twisting the diaphragms??? The older drivers can have very tight gaps with channels cut to allow for the return on the coil that is laid against the wound voice coil. JBL specifically tells you not to rotate the coil in the gap??? You can see the channels in the attached photo's. You are twisting with the screws in place ?? Yes !! Just don't want the uninitiated to twist without screws for stops.
Rob
"I could be arguing in my spare time"
" Install the diaphragm and with the securing screws only finger tight ... "
Sorry if that wasn't clear enough. My suggestions are based on decades of repairing speakers & installing compression driver diaphragms for use in concert sound systems where the listeners are thirty feet away to a few hundred feet away. They should not be undertaken by the feint of heart. Yes more precision and caution is a good idea for your home stereo or studio monitors. I'm simply explaining that in the case of the original question if he decides that the diaphragm he has isn't performing as he wants there are options to exercise before throwing it away and looking for a replacement.
How far are you twisting the diaphragms??? The older drivers can have very tight gaps with channels cut to allow for the return on the coil that is laid against the wound voice coil. JBL specifically tells you not to rotate the coil in the gap??? You can see the channels in the attached photo's. You are twisting with the screws in place ?? Yes !! Just don't want the uninitiated to twist without screws for stops.
Rob
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