"Eine Schwalbe macht noch keinen Sommer", the saying goes (one swallow does not a summer make), but what I just experienced is quite astonishing, given the sorry state of Neumann K870/K87 capsules of late: Tonight I installed a brand-new K870 (build date late 2012), and my jaw dropped: Both sides of the capsule are lush, reedy, frequency-balanced, with a full-figured bass, and are extraordinarily musical. Only the very best K67 from the mid 1960s (the famous 'fibre board' model) could hold a candle to this one. This capsule was so exquisite and similar on both sides (very rare, for any LD dual-membrane capsule, from any period) that I still don't know which of the two sides to make the front side for cardioid operation.I am hoping and praying that this is a trend, and will report what the next new K870 capsule portends.Disclaimer: the electronics of the U87Ai which I installed the capsule in are heavily modified; so while this capsule could mitigate some of the stock U87Ai's electronic compromises (which I find especially unsatisfying since circuit diagram 05), it cannot overcome them all.
I've never heard a re-skinned Neumann capsule that actually approached the sound of a good Neumann. I've heard one of Mr. Thiersch's excellent M7-style rebuilds, and it sounded to my ear very much like Thiersch's excellent new capsules, but (especially being the Mylar version) it did not sound exactly like a good vintage Berlin M7.
Then what hope is there for a U47 owner who needs an M7 replacement?
China may be an answer to reproducing PVC capsule diaphrams. They don't follow EPA or CE environmental restrictions there.
I know this thread is old, but I'm wondering if that was a one-off experience or have you experienced a general improvement in k870 capsule quality?
Yes, it is. And this mic's response, as that of the U87Ai, therefore is largely affected by the individual response of the actual capsule installed.
So, how do you test the diaphragm tension of an assembled capsule, or do you just listen empirically?
It always seems a little circumspect to me to peg difference down to just that. Small differences in the size of holes in the backplate for instance, etc., could seemingly make as much difference in end frequency response.
It also seems like low tension can be a bad thing... one of the first things to make a capsule sound bad, IMO, is low tension that starts to result in a capsule being overly sensitive to plosives.
So, has Sennheiser/Neumann improved things lately?
Extreme cases of diaphragm hypertension that I encountered in late 2017/18, and in the U67Reissue I tested and wrote about are getting rare. It's the average that still concerns me: too many people continue to send me current-issue capsules to reduce the tension back to 1960s level. It's time-consuming and not lucrative, but an interesting project I continue to refine and improve.