In late 2018, I purchased “NAIM SBL NAIM ALLAE interior foam damping pads” from PureSoundSales on eBay. The damping foam in the upper cabinet of my SL2s had turned to dust (as had the grilles, several years earlier) and needed replacing. It worked perfectly. I have no idea if this is what you need for your DBLs, but the product is still available on eBay.