Phase IV complete

Sunday evening. The painting is finished, the cabinets polished. All that remains is mounting the drivers: Which was going fine until the last unit, which was taken from the original Mk 1 prototype (left rear, white cab). These drivers were 6 months or so older than the ones in the Mk 2s (red) and turns out weren't exactly the same size. They were significantly (about 1 mm) larger in diameter, which meant the openings in the baffle had to be re-routed. Without anything in the middle to locate the router this is a bit of a problem. Silver Flute has a long way to go in terms of manufacturing consistency.

However, 6am Monday morning, before it got too hot, I cut a plug to go into the baffle opening and re-routed the hole. By 8:30 they were finally finished.

Both were tested. The graph below shows the two Phase IV units (one black, one red) and one of my old DM6s (blue). I was (am) concerned about one of the Phase IVs having a 9dB drop around 162 Hz but then THe DM6 has a drop of 14dB @ 248 so the problem isn't quite as horrible as I first thought. Still it's not great; and worse yet I don't know what's causing it. I thought for a moment it was a polarity problem between the woofers and the mid-range but reversing the woofers polarity made things worse so that wasn't it. Most likely it's a feature of the cabinet which is a bit of a shame since at this stage I don't really know what I can do.

However they sound very different in the mid and upper mids from the B&Ws. I think they resolve a lot more detail but I'm so accustomed to the B&W sound - rather warm and soft like an old pillow - that the Phase IVs will take a little getting used to.

Finally, I'd like to thank Mark Zachmann for creating Speaker Workshop which has been an invaluable tool.

This will be the last post for a while. I have a three more projects lined up (replacing the B&W crossovers, building a smaller version of the Phase IV with only one 4ohm woofer, the then the Phase Vs for which the design work is done). But for the moment I'm going to spend some time getting used to the Phase IV Mk2s.