Big One That Got Away-Listening Report

[Jim Butler]

I couldn't wait. Got home and opened them up. They are 605A's. As I said in my earlier post, they look new.

I hooked them up to a Pioneer 1080 crossed through a PE plate amp that powers a 411 woofer in a sealed 620 cab. I put on a Beck CD. Clear, clean, and interestingly more relaxed than 604-8H's.http://www.hostboard.com/ubb/icons/icon14.gif

The 411 sub crosses in about 70hz at 12db/octave. This PE plate amp's crossover supposedly filter's the mains in at a 6db drop per octave starting at 120hz.

The blend seemed very smooth and allowed the 605's to really rock. But its clear their bass response rolls off pretty high if played without the sub.

Question: The cabinets internal volume measures exactly 6.83 cubic ft. Subtracting the .33 Vid of the 605A you get 6.5. I figured this to be a reasonable Altec volume for a ported cab....except these are not ported. Its not exactly like they're airtight either (loose baffle-joints and no caulking). I'm wondering what Altec calculated in letting the 605's woofer cone drop off in this design. Does anyone know what a 605A cone response is in such a situation? There are earlier posts that indicate a 605A cone is the same as a 416's...

[GM]

Well, it would have a ~critically damped alignment, though any air leaks will change it a bit, but consider the times and what it was voiced with: http://hifilit.com/hifilit/Altec/1959-e.jpg

With this much power/boost and typically positioned up against a wall combined with impedance matching, there's ~23 dB of LF boost available, more than enough to either flatten its response to at least Fs or turn it into a serious boom-box.

For SS amps consider sealing up any leaks and replacing the rear cover with a braced 19 mm BB ply one with a 5" diameter vent hole offset so it's not directly behind the driver if ~42 Hz is low enough or experiment with 5" diameter tubes up to 5" long and maybe some digital EQ.

GM