I've been avidly reading this string, and some old AudioCraft articles on tuning bass reflex enclosures. I'm not technically inclined and don't have access to woodworking tools, but last night I had a brainstorm. As an experiment, I covered up ~half of the vents on my 828s with big stacks of record albums in order to see if it made any difference. Yes it did! As suggested by the other posters and in the articles, the bass tightened up noticablly and also apparently extends further down. Even better, the LF and HF drivers blend better -- solving a minor problem I'd pretty much given up on.

I'm definitely a convert to the idea that the 828's reflex tuning can be improved upon -- at least with the 515B's I use. I wonder why Altec didn't design the 828's with a smaller vent in the first place?

Now I have to find a carpenter who will make some new 3.5" vent panels for me. Maybe this is something Iconic could offer (along with kits to better brace 828 cabinets -- ala Marcus -- and to enclose the horn flares)? Please?

Thanks to all who have posted constructive ideas on improving the sound of these speakers.