My 38-7 has a nice big speaker, but not much bass. It looks like the spider has stiffened over its 80 year life (understandably), and the cone can't follow the larger bass motion. Is there anyway to soften the spider, and make it more compliant? If it was an old baseball glove I'd put neatsfoot oil on it. But I don't have any clue about cardboard. It otherwise looks to be in great shape, so I'd hate to make it worse.
I just spent a week chasing down cracks and spots where it separated on the cone at the rim where it flexes that appeared as I continuously played as much bass as I could, then patch and gently flex the center cone which I had repaired a couple months back and massaging it back to life. As the glue dried, I gently persuaded it to flex right at the outer edge of the cone. The glue took 24 hours to fully dry. Gave a lot of working time to it. My cone was completely shot with severe holes and cracks, along with disintegrating paper. It would tend to come apart at the areas where I hadn't fixed yet. The thing is to allow the center cone to vibrate at whatever rate it needs to, while having the outer edge secured with a good flex. THIS SPEAKER SOUNDS GREAT!!! The bass is beautiful, full, dynamic and LOUD!!! However, the speaker itself looks hideous!!! It probably would be in your best interest to have it re-coned, but if you're adventurous...
Your speaker looks like it has been through a war zone! It is encouraging to see how much repair they can take and still function.
Until my speaker degrades a lot more, I'll just accept that it is too stiff, so no re-coning in it's immediate future. If there was a speaker-yoga class down at the health spa, I'd sign it up.
I'm listening to it right now. it...sounds... FANTASTIC!!! It is incredible how they can bounce back to life... That speaker-yoga class might not be a bad idea! (I do something similar myself whenever I embark upon a new project. You must be "ONE" with the radio. It really does wonders for me and the projects always seem to come out favorably!!!) Just for the fun of it, have you checked your alignment lately? That will cause lack of bass, if it is misaligned...
You mean the IF alignment, not the speaker coil, right? I did a quick alignment when I got it running, but I did not play with the trim capacitors. Unfortunately I noticed last night the dial calibration is nonlinear, so I need to go back in there and play with those, and will touch up the IF again as well. Thanks!