Jim Audiomisc
pfm Member
I’d seriously recommend trying a valve power amp or integrated. Your speakers were designed using one and based on a design that would have been too. I own a pair of the WD18s (like Heybrook HB2s) and the only time they really sang properly was on the end of a push-pull kt88 amp. They sound fine but a little lifeless on transistor amps. Being class A I’m guessing your Sugden has quite a high damping factor. Definitely worth a try. The WD amps can be had very reasonably used.
Well, if someone really wants to, they can experient with a series resistor + cap network between amp and speaker. As with the ESL57 + 303 the unbypassed coupling cap adds a 'bump' to the low LF response, and the resistor alters the overall response according to the speaker impedance vs frequency. Its a cheap and low-skill way to experiment.