XN270 is small standmount loudpeaker, with Scan Speak Classic series drivers, midwoofer 18W/8535 in closed box and tweeter 9700. The age of this loudspeaker pair was ~15years, so it was time to make a control measurements, look inside and evaluate what would worth improvement. To my quite surprise all drivers were in very good state and it was luck new drivers were not needed. After short discussion we came with following reasonable and quite easy scope of the upgrade:

1. Internal wiring changes to Jantzen silver coated copper 2.5mm PTFE wire

2. Tweeter capacitor changed to Jantzen Silver Z-cap

3. Binding posts Jantzen were installed

4. As there was no damping in the cabinets originaly at all, I added damping material to rear half of the cabinet

Below is on axis measurement of both loudspeakers, before and after. There is the difference between left and right loudspeaker, and I would blame 18W paper cone differences in that area. This is quite common for soft cone drivers.

Horizontal off axis measurements are below for 0-90degrees. Mic was placed 77cm far from front baffle, and at the height of tweeter-midrange overlap. On the left: Smoothing 1/12 was applied, on the right: gating 5.2ms. 

Impedance measurements are below, again before and after. Besides the change of the woofer resonance frequency, notice also improvement of resonance at 500Hz, both thank to additional damping material. This also improved the sound of midrange, it became less hollow and hidden and more open and apparent.

....and the sound after upgrade....

These are the least sensitive speakers I have ever listened to. They need WATTs.  I was quite surprised with bass quality from this small 18W woofer in closed box. It is not full-bodied, physical and kicking kind of bass and anyone could not expect that, but it is textured, easy to listen, lacking any boomy character. This is something I really appreciate. Overall character was somewhat darker, dull and "in the speakers" sound, but after upgrade the sound got sparkle, air and very enjoyable character. The drivers are well integrated and the sound just flows out of them without any sense of disconnection or different characters. I liked them. It amazes me that all these Classic series drivers have a lot to say still these days after being decades in the production.

Photos