I snagged four NE123W-08 and two NE149W-08 from a local dealer who was closing out NOS.
The first pair had a label attached reading "Tymphany NE123W-08". A very long extended pole piece and copper ring nearly as long are visible through the venting holes of the VC former. The winding extends about 2 mm beyond the top plate. In typical Peerless fashion, the second layer is missing 1-2 turns at the top (this improves Bxl symmetry for cylindrical pole pieces). 2 mm top overhang for a stated x-lin of 3.1 mm seem on the low side but are probably ok given tolerances and intentional offset.
The second pair came without those labels attached. There are Vifa/Tymphany badges on the frame and a sticker reading RM Vifa 4". Coil overhang is only 1.5 mm in one and 1.0 mm in the other driver.
The pair of NE149 drivers has the same badges and stickers reading RM Vifa 5.25". Coil overhang is about 1.6 mm in the first and a hair above 1 mm in the other which is really low for a stated x-lin of 5.0 mm.
What kind of overhangs and variation have you observed in this series of drivers? Is there a change RM stands for midrange and these are actually drivers with a shorter coil?
This thread here has pictures of the NE149W, and according to the impedance plot, it must be a -08. In the third picture, I can count about 10 turns, and the picture is taken from slightly below the top plate, so it might even be 11 turns. I count three turns in the shorter of the two drivers (pic below).
https://techtalk.parts-express.com/forum/tech-talk-forum/57431-vifa-ne149w
The first pair had a label attached reading "Tymphany NE123W-08". A very long extended pole piece and copper ring nearly as long are visible through the venting holes of the VC former. The winding extends about 2 mm beyond the top plate. In typical Peerless fashion, the second layer is missing 1-2 turns at the top (this improves Bxl symmetry for cylindrical pole pieces). 2 mm top overhang for a stated x-lin of 3.1 mm seem on the low side but are probably ok given tolerances and intentional offset.
The second pair came without those labels attached. There are Vifa/Tymphany badges on the frame and a sticker reading RM Vifa 4". Coil overhang is only 1.5 mm in one and 1.0 mm in the other driver.
The pair of NE149 drivers has the same badges and stickers reading RM Vifa 5.25". Coil overhang is about 1.6 mm in the first and a hair above 1 mm in the other which is really low for a stated x-lin of 5.0 mm.
What kind of overhangs and variation have you observed in this series of drivers? Is there a change RM stands for midrange and these are actually drivers with a shorter coil?
This thread here has pictures of the NE149W, and according to the impedance plot, it must be a -08. In the third picture, I can count about 10 turns, and the picture is taken from slightly below the top plate, so it might even be 11 turns. I count three turns in the shorter of the two drivers (pic below).
https://techtalk.parts-express.com/forum/tech-talk-forum/57431-vifa-ne149w
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Anyone? Pictures or just the mm of your NE123 or NE149 would be much appreciated.
At the moment, other than my drivers, I have only the techtalk thread to go by. If the wire is the same thickness, that would amount to about 3 or 3.5 mm overhang. Not much compared to 5 mm x_lin, but certainly more than in my drivers.
I realize some offset may be intentional but I just checked two other drivers (Scan Speak 15W8535 and Peerless NE95W) and overhang was within 0.2 mm of data sheet.
Is maybe the conical top plate responsible for some of this apparent offset? I would have to do a FEMM simulation to see, which I haven't done in years. But that would still leave me with about 2 - 2.5 mm variation between the one in the techtalk pic and mine with shorter overhang.
At the moment, other than my drivers, I have only the techtalk thread to go by. If the wire is the same thickness, that would amount to about 3 or 3.5 mm overhang. Not much compared to 5 mm x_lin, but certainly more than in my drivers.
I realize some offset may be intentional but I just checked two other drivers (Scan Speak 15W8535 and Peerless NE95W) and overhang was within 0.2 mm of data sheet.
Is maybe the conical top plate responsible for some of this apparent offset? I would have to do a FEMM simulation to see, which I haven't done in years. But that would still leave me with about 2 - 2.5 mm variation between the one in the techtalk pic and mine with shorter overhang.
Erin tested big brother ne180 many years ago. That also has 2.5mm offset.
https://techtalk.parts-express.com/forum/tech-talk-forum/48186-vifa-ne180w-4-klippel-testing
https://techtalk.parts-express.com/forum/tech-talk-forum/48186-vifa-ne180w-4-klippel-testing
Yes, Erin's full Klippel test of the NE180W-04 is here:
https://www.diymobileaudio.com/threads/vifa-ne180w-4.120417/
Vance also tested it (page 8): https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/40_Voice_Coil/2010/2010_8_Aug.pdf
Vance writes that the NE149 was tested in the Dec. 09 issue but it does not seem to be available online.
In Erin's test, the offset of Kms is about 3 mm towards coil out, the Bxl offset is about 2 mm coil out. In Vance's test, it is about 2.5 mm for Kms and -0.47 mm (i.e. coil in) for Bxl.
Not sure what the difference in Bxl offset means? Choice of parameters in Klippel testing or huge production tolerances even then?
Let's zero in on the Kms offset that is almost identical in both tests. It means that the suspension get slightly softer as the cone moves out until it reaches 2.5 mm coil out. Not sure how this is physically possible at the cone sits at 0 with no current applied and I can vouch that the spider is flat in rest position. It is probably a dynamic stiffness, meaning that the surround gets softer at frequency, and this cause the cone to move out as it moves at a certain frequency.
I am really confused about what Vance writes about this:
Figures 7 and 8 show the Kms(X) and Kms symmetry range curves. The Kms(X) curve is likewise very symmetrical in both directions, but with a forward (coil-out) offset of about 2.5mm at the rest position decreasing to 2.4mm coil-out offset at the physical Xmax position, which means it stays mostly constant suggesting a physical offset of magnetic center, an easy fix in production.
In my understanding, the Kms is about the mechanical properties, so a Kms offset means the symmetry point at frequency is different from the mechanical symmetry at rest. What's this got to do with an offset of magnetic center, which I would expect to show up in the Bxl plot?
Assuming that Erin's results are right about the +2 mm Bxl offset and this is really what describes the magnetic offset, I think this is consistent with what I see on my drivers. The coil is too far in at rest position, and moving it out makes it sit more symmetrically around the top plate which is exactly what you see in Erin's Bxl plot.
https://www.diymobileaudio.com/threads/vifa-ne180w-4.120417/
Vance also tested it (page 8): https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/40_Voice_Coil/2010/2010_8_Aug.pdf
Vance writes that the NE149 was tested in the Dec. 09 issue but it does not seem to be available online.
In Erin's test, the offset of Kms is about 3 mm towards coil out, the Bxl offset is about 2 mm coil out. In Vance's test, it is about 2.5 mm for Kms and -0.47 mm (i.e. coil in) for Bxl.
Not sure what the difference in Bxl offset means? Choice of parameters in Klippel testing or huge production tolerances even then?
Let's zero in on the Kms offset that is almost identical in both tests. It means that the suspension get slightly softer as the cone moves out until it reaches 2.5 mm coil out. Not sure how this is physically possible at the cone sits at 0 with no current applied and I can vouch that the spider is flat in rest position. It is probably a dynamic stiffness, meaning that the surround gets softer at frequency, and this cause the cone to move out as it moves at a certain frequency.
I am really confused about what Vance writes about this:
Figures 7 and 8 show the Kms(X) and Kms symmetry range curves. The Kms(X) curve is likewise very symmetrical in both directions, but with a forward (coil-out) offset of about 2.5mm at the rest position decreasing to 2.4mm coil-out offset at the physical Xmax position, which means it stays mostly constant suggesting a physical offset of magnetic center, an easy fix in production.
In my understanding, the Kms is about the mechanical properties, so a Kms offset means the symmetry point at frequency is different from the mechanical symmetry at rest. What's this got to do with an offset of magnetic center, which I would expect to show up in the Bxl plot?
Assuming that Erin's results are right about the +2 mm Bxl offset and this is really what describes the magnetic offset, I think this is consistent with what I see on my drivers. The coil is too far in at rest position, and moving it out makes it sit more symmetrically around the top plate which is exactly what you see in Erin's Bxl plot.
I don't trust that particular Klippel test too much. There's some number looking very strange. For instance, BL is only 3.7 at rest position, Mms is way too small(5.929g ?!), and XMAX actually looks twice as big. I simply don't believe that motor only lose 50% BL after moving 13mm coil-out (The coil is completely out of gap at this point).
Vance test the same driver here, which looks much more believable.
https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/40_Voice_Coil/2010/2010_8_Aug.pdf
This happened before, multiple times. Some klippel test seems not calibrated and looks twice as big as it should be. For example
https://audioxpress.com/article/Test-Bench-Dayton-Audio-ES140Ti-8-5-5-Midwoofer