So I only have the 2 and the 5, and I don’t find the 5 lacking in bass. I find it definitely better than the 2, esp. without EQ. But I skipped over the 3 and 4, and bought the 5 based on love of the 2 once I EQ’d it.I've done a few tests this week with the LCD4 and LCD5, I agree the 5's can't do bass like the 4. Sorry, they can't. I'm sending my 5's back and keeping the 4. Now the 5 is tighter and faster, but just aren't my preference. I like the slightly slower decay of the 4. And the increased bass level fits the genres I use them for. When I want fast, tight bass I'll grab the CRBN. I prefer the CRBN over the 5 for its warmer signature. Never thought I would say that about an electrostatic, but here we are. Just my preference, nothing wrong with the 5, just not for me.
Pretty much every headphone I do an <80 Hz bass shelf. The only one I’ve seen (not heard) is the Stealth, that *might* not need this.