Quote Originally Posted by bfish View Post
Really? I thought they just recommended sealed.
At this point, the only written 'proof' I'm aware of that it was more than a suggestion is Altec's lack of listing any vented alignment for the 411 in their '74 DIY manual and of course practicing what they 'preached' by only offering the various 411 versions in sealed cabs.

From experience with a very early pair with the super low Fs, high Vas though, it took a fairly large cab tuned very low to keep the driver linear. When I experimented with venting them loaded in the bottom half of blocked off 825s it caused some strange fart-like noises to emanate from the surround along with some interesting looking rippling, so sealed it was.

Don't have a clue about the later versions, though I gather from Ron's experience that if you send a 411 to GPA, it comes back as some 'flavor' of 416 (or maybe even 515) performance wise, so I imagine that venting is a viable choice in many (most?) apps, making me wonder how its performance in a 411 spec cab, etc., compares to the original, especially the 9846 with its special filters.

GM