Welcome! Need support, you got it. Or share your ideas and experiences.
Return to Planar Speaker Asylum
71.62.218.36
I received an email from a Maggie owner in the Netherlands who thinks he found the difference in the 3.7 and 3.7i. The 3.7i has paper tape attached to the mid-panel. He wrote to me, hoping to find out what exactly was used as it appeared from his missive that he needed it repaired. I directed him to call Wendell as I had no idea.
Attached is the picture of his 3.7i showing the strip.
I married the perfect woman - the downside is that everything that goes wrong is my fault.
Follow Ups:
If it looks like what it looks like, that's the magnet pole piece on the rear.
The paper isn't attached to the mylar driver it seems, so changing its damping doesn't seem to be the effect. It might be an attenuator to lower the high frequencies going to the rear.
I bet there are other changes which may be invisible, like the double secret magic tensioning.
You know how Apogees have a trapezoidal lower frequency driver? Why? Physics of course, a rectangular one has more vibrational modes degenerate at similar frequencies, i.e. a lumpier frequency response. So you change the geometry asymmetrically to spread out the resonance frequencies of the various modes.
I read somewhere (can't remember now) that Magnepan has the same effect, but more cost effectively: upon manufacture the upper part of the mylar is stretched tighter than the lower parts.
I bet the 3.7i is looser in the lower portions than the plain 3.7.
This is to make up for the round wire -> flat wire transition. With insulated round wire they could and did double up on the center portions of the bass driver: more bass efficiency & response.
Maybe the longevity was an issue with round wire but I'm not convinced there is a sonic advantage to flat wire on the bass driver.
Does the 20.7/30.7 have flat or round wire on the bass driver?
Magnepan used/uses different methods for tuning the resonant behaviour. A rectangular driver without "buttons" need a varying tuning top-to-bottom. That can be found in some Tympani bass drivers. Others are tuned with the help of buttons that split the diaphragm into smaller sections with varying resonant behaviour. Both methods can be used together. The 3.7/3.7i have a lot of buttons.
The 20.7 have foil conductors.
Or...
;)
Regards,
Steve
There is tape on the back of the mid of the 3.6 as well. My T-IVa mids had some thick felt on some parts on there backs.
I guess to get the answer someone with the 3.7 needs to open them up and take a look to see if the tape is there or not.
I married the perfect woman - the downside is that everything that goes wrong is my fault.
I talked to a guy with 3.7 some years ago. 3.7 is without tape behind the mids. He had 3.6 earlier and found the 3.7 to be a bit thin. A few days ago another reported that about his 3.7i vs. 1.6. Is the 3.7 and 3.7i thinner sounding?
... have paper glued to the back, down the centre (pole-piece side).
Andy
Mine too -- it's presumably damping. Anyway, someone mentioned the paper here years ago, you must have missed it!
Edits: 02/05/21
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: