Post by svart on Apr 20, 2022 14:39:21 GMT -6
So I bought another set of NS10 for ridiculously cheap.. Let's say cheaper than to replace a single woofer.. But one of the tweeters was blown.
I always wanted to see if there was a way to resurrect a dead NS10 tweeter since they are crazy expensive for NOS parts and generally pretty expensive for the Avantone replacement.
I also bought an Avantone replacement because I was curious to see how good it was.. And it was decent enough, but it was probably a few dB higher in volume than an original. This seemed to corroborate the "they're brighter sounding" reviews I've seen about them. Otherwise, they look identical. I didn't take it apart to see what the voicecoil looks like though.
On to my experiment!
I disassembled my tweeter and noticed that the voicecoil was slightly browned. It did not have continuity through the connectors so somewhere along the path the wire was broken. I noticed that the flexible wires from the connectors/terminals was corroded and looked rather bad shape. One of the flex wires did not even have continuity from end to end. I could not test the coil directly in-situ due to the glue that was covering up the transitions between the coil wire and the flex wire.
One thing of note, the original coil wire is not a round conductor. It's FLAT but wound so that the flats are perpendicular to the movement of the coil in the speaker. I'm unsure of why it's this way, but it would take some work to manufacture this, so I assume there was a good reason. The coil backing is some kind of paper coated in wax or glue. It's not very stiff and was easily pulled off the diaphragm, but also easily deformed.
Also of note, the voicecoil is 27mm ID. That's a very odd size and I had a hard time finding 27mm voicecoils and/or replacement diaphragms, but I was able to find two different kinds. I found a discrete voicecoil and a voicecoil/diaphragm assembly which I intended to remove the diaphragm from as it was metal and too small.
After removing the original diaphragm I was able to remove the flex wires and attempt to measure the NS10 original coil resistance. To my surprise, the coil measured out to be around 5.9 ohms. This means that the coil itself was OK and that the failure was with the flex wires. Nonetheless, I had already removed and damaged the original voicecoil and it is unusable.
The new coils are both slightly more prominent. The original coil is roughly 5mm tall while the others are 5.5mm and 6mm.
The discrete coil measures 6.5 ohms and has a metal coil former with kapton type tape and the one removed from the diaphragm measures 7+ ohms but looks to be only kapton material as the coil former.
I had no issues removing the remainder of the old coil and glue from the diaphragm. It was old enough to have become brittle and easily pulled up in chunks.
I also had little issue in gluing the new coil down. I chose to try the discrete coil (5.5mm and 6.5 ohms) since it was the closer match for size and resistance but I am unsure of the role that the metal former might have on the sound, nor the increased depth or difference in impedance. When reinstalling the assembly, I found that the coil had slight rubbing where the flex wire is attached to the coil wires and the magnet assembly. I was able to gently use tweezers and soldering iron to reposition the solder joint so that it was nearly flat against the coil backing which removed the rubbing.
The end result is that the tweeter works. The volume is slightly less than the other original tweeter and many dB less than the Avantone replacement. I do not detect any harshness or distortion. Other than it being lower volume, it sounds rather normal for an NS10 tweeter, but I believe it to be unusably low in volume compared to a NOS tweeter.
Now, the next experiment is to replace a NS10 tweeter coil with the other style of coil to see if the sound is more in line with the original NS10 tweeter I have to compare to.
If I can find more broken tweeters I can also experiment with unwinding one of the replacement coils slightly to see if I can get either one down to more like 5.9 ohms to increase the volume and/or see if the flex wires are a common failure point. It would be interesting to see that a corroded wire exposed to higher powers over time would be more of a fusible link than a coil of wire.
I always wanted to see if there was a way to resurrect a dead NS10 tweeter since they are crazy expensive for NOS parts and generally pretty expensive for the Avantone replacement.
I also bought an Avantone replacement because I was curious to see how good it was.. And it was decent enough, but it was probably a few dB higher in volume than an original. This seemed to corroborate the "they're brighter sounding" reviews I've seen about them. Otherwise, they look identical. I didn't take it apart to see what the voicecoil looks like though.
On to my experiment!
I disassembled my tweeter and noticed that the voicecoil was slightly browned. It did not have continuity through the connectors so somewhere along the path the wire was broken. I noticed that the flexible wires from the connectors/terminals was corroded and looked rather bad shape. One of the flex wires did not even have continuity from end to end. I could not test the coil directly in-situ due to the glue that was covering up the transitions between the coil wire and the flex wire.
One thing of note, the original coil wire is not a round conductor. It's FLAT but wound so that the flats are perpendicular to the movement of the coil in the speaker. I'm unsure of why it's this way, but it would take some work to manufacture this, so I assume there was a good reason. The coil backing is some kind of paper coated in wax or glue. It's not very stiff and was easily pulled off the diaphragm, but also easily deformed.
Also of note, the voicecoil is 27mm ID. That's a very odd size and I had a hard time finding 27mm voicecoils and/or replacement diaphragms, but I was able to find two different kinds. I found a discrete voicecoil and a voicecoil/diaphragm assembly which I intended to remove the diaphragm from as it was metal and too small.
After removing the original diaphragm I was able to remove the flex wires and attempt to measure the NS10 original coil resistance. To my surprise, the coil measured out to be around 5.9 ohms. This means that the coil itself was OK and that the failure was with the flex wires. Nonetheless, I had already removed and damaged the original voicecoil and it is unusable.
The new coils are both slightly more prominent. The original coil is roughly 5mm tall while the others are 5.5mm and 6mm.
The discrete coil measures 6.5 ohms and has a metal coil former with kapton type tape and the one removed from the diaphragm measures 7+ ohms but looks to be only kapton material as the coil former.
I had no issues removing the remainder of the old coil and glue from the diaphragm. It was old enough to have become brittle and easily pulled up in chunks.
I also had little issue in gluing the new coil down. I chose to try the discrete coil (5.5mm and 6.5 ohms) since it was the closer match for size and resistance but I am unsure of the role that the metal former might have on the sound, nor the increased depth or difference in impedance. When reinstalling the assembly, I found that the coil had slight rubbing where the flex wire is attached to the coil wires and the magnet assembly. I was able to gently use tweezers and soldering iron to reposition the solder joint so that it was nearly flat against the coil backing which removed the rubbing.
The end result is that the tweeter works. The volume is slightly less than the other original tweeter and many dB less than the Avantone replacement. I do not detect any harshness or distortion. Other than it being lower volume, it sounds rather normal for an NS10 tweeter, but I believe it to be unusably low in volume compared to a NOS tweeter.
Now, the next experiment is to replace a NS10 tweeter coil with the other style of coil to see if the sound is more in line with the original NS10 tweeter I have to compare to.
If I can find more broken tweeters I can also experiment with unwinding one of the replacement coils slightly to see if I can get either one down to more like 5.9 ohms to increase the volume and/or see if the flex wires are a common failure point. It would be interesting to see that a corroded wire exposed to higher powers over time would be more of a fusible link than a coil of wire.
