I'm in the beginning process of converting my Normal bias Sigmas to Pro, and am looking for thoughts on what to expect between either the 303 and 404 drivers in the Sigma frames. There are a few threads about the 404 versus the Normal bias Sigmas, but not much that I could find on using the SR-303 as a donor. Anyone done a conversion with 303 drivers, who has also heard the 404s?
Initially, I had hoped to find someone to do the conversion for me. I emailed around a bit, and found no one was apparently willing to do the conversion any more, so I figured I would look into doing it myself. After reading through a few threads, I decided to look for a suitable donor, rather than just tear into my SR-404s blindly. I eventually found a broken set of SR-303s pretty cheap on eBay, that had various issues with broken and missing pieces on the frame, but with good drivers. So I started with removing the SR-303s drivers, as I figured if I messed-up the removal of the 303s, I woudn't be too upset. That went pretty well, so I carefully removed the normal drivers from the Sigmas, which also went fine. I took lots of photos, if anyone is interested. So now I have one SR-303 driver installed and will soon have the other installed. I'm using a light-coat of rubber cement to attach the driver. Assuming all goes well, my next thoughts will be on whether to leave the SR-303 drivers in-place or whether to open-up the SR-404s and install those drivers. Also, what to do with the normal bias drivers that were in the Sigmas originally? Anyone know what other models Stax used them in? I guess I could put them in the SR-303 (or 404) frames and add some new parts to fix the broken pieces and then have some Normal Bias Lambdas in 303 (or 404) frames, or maybe just sell the original drivers to someone who wants spares. They would be unique with SR-303 (404) frames and "kettle-cord" cables, thats for sure. I'll certainly hang onto the drivers until I am sure I don't hate the conversion and want to return them to normal bias.
Another other question for all you Stax experts out there: One of the drivers of the 303 had it's black metal protection mesh pushed-in. From what I read from other threads, this is just cosmetic right? Can anyone confirm this is indeed just cosmetic, and won't affect the sound in any way? The drivers seemed to be balanced before I removed them from the original 303 frames, but I just want to be sure I don't waste my time on a set of drivers that won't be matched acoustically. Here is a photo of the one driver that has the pushed-in protective mesh:
I'll post more photos of the process if anyone is interested. Thanks in advance to those that might offer input or helpful advice in the conversion!