I want to first of all thank Will for his excellent advice and service.
I had noticed that my ebay purchased HB1s required a lot of volume to bring them alive so I thought it was time to replace the originals, rather than losing my hearing!
Having purchased a simple soldering set from Hifi Collective, I set about unbolting the original 8" speaker, saving its original plastic seal and discovered the loose wool inside which I replaced with a denser wool thickness whilst still leaving a hollow for the basket of the new 8" Vifa . I then notice that the latter was simply made of pressed metal, so it "rang". Consequently, I used finger-applied caulk over the reverse and rim of the speaker basket to damp the ringing. I also decided to replace the original tweeters with the recommended Morel CAT298 -104mm ; mention this at the same time as one needs access through the 8" speaker to accomplish this. The reason being that the contacts on the Morel are in one location whilst the originals are at either side of the tweeter enclosure . Consequently, unless one re-routes both cables through one of the original holes the new Moral won't sit flat on the internal wooden tweeter enclosure. So I threaded the brown wire (red) through the widened hole for the blue and filled the underside of the redundant hole with caulk. The Morel only has three bolt holes and these can only be fitted in Y-shape because of the lack of wood to hold them - so three extra holes require to drilled. NB the 94 mm faceplate is too small for the diameter of the HB1. it is the CAT298-104 mm that is needed, or at least it was for my HB1s. All of this had to be done before the actual connection of the new Vifa anf the Morels . I watched Danny Richie's excellent soldering tutorial on GR Research's Youtube channel and managed to make the connections.
Thankfully, the considerable effort involved, which was quite testing , has been worth it. The improvement was dramatically for the better - no longer deafened to get any bass response, no sub-woofer will ever be required! LP playback via Denon DL103 MC cartridge, Phasemation SUT 320 to MM phono stage of Marantz PM17 KI Sig. sounds warm and life like. For near-field listening Iturn the HB1s away from my seating position to avoid tweeter "sizzle". I was fortunate to purchase the HB1s with the original stands which are a perfect height for an Ikea Poang armchair.
I apologise for the length of this review and for including mention of the Morel CAT298-104 as well, but I couldn't find a step by step guide to the speaker replacement process and hope it may give non-tech audiophiles the confidence to improve their vintage speakers for themselves.
Highly recommend Willys Hifi for excellent service and advice communications.
