High Efficiency Speaker Asylum

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RE: Belated THANKS to Uncle Stu, R.I.P.

Posted by drlowmu on December 30, 2016 at 15:08:47:

The thing I want to avoid is to change the box from stock. Everyone changes them, butchers a stock box, but not me. I added no braces inside either. I did mass-load the boxes, by ear, and stopped around 290 pounds per side. That easily improved the stock box, was very inexpensive, and guess what, it is totally reversible back to stock.
If you change the port, you determine that port size by ear, AFTER all else is set-up, and I would do it last. When you change the port size, you also change other parameters me thinks, perhaps efficiency, etc.
So, with the help of Dennis Fraker, who used to typically put eight A7-800s in each of the movie theaters he owned, or for theaters he bought and renovated for resale, I did my changes in a different pecking-order than what others typically do. ie:
a) I sent my 802s off to GPA for re-magnetizing and new stock diaphragms.
b) I carefully cleaned the surrounds on my 515Bs.
c) I extensively rewired the speaker internally, from the crossover to the drivers. I use Mil Spec wire, ran doubled-up 12 AWG ( equals 9 AWG ) to each woofer polarity, at Bob Fulton lengths ( 57 1/8th inches ). I ran 14 AWG Mil Spec from the crossover to the 802, not doubled up, however, 57 1/8th inches in length.
d) I rebuilt the 800 HZ / 12 dB crossover with much better parts, better Mil Spec wiring, and changed the adjustment pot from 20 Ohms to a 6 Ohm Ohmite 25 Watter, so I can get fine driver adjustmemts easier. " Human engineering " versus 20 Ohms . I used DIY golf balls to isolate the external crossover with mass loading. And my cap choice is to die for.
e) On the ALTEC 515B and 802D drivers, I eliminated the stock ALTEC " press to fit " terminals, stock, and Wonder soldered the Mil Spec wire carefully, properly, directly to the terminals that feed the voice coil wires. A big permanent improvement.
f) I made up DIY speaker cables, Fulton length multiples, Mil Spec and used three 12 AWG Mil Spec wires in parallel, lightly twisted, for each polarity.
g) I decided that the NOS 45 tubes I had been using, were not linear in the mid range, had a broad shallow depression, and just one listen to a JJ 2A3-40, in my 45 amp, convinced me to build a new DC amp using JJ 2A3-40s for the VOTTS, done 12-1-16, still breaking-in and needing final bypass work on all the film caps. Excellent change BTW !!
Comer, everything I did above, I would do again and suggest to others in the order shown, and the "port size" will be something I may be ready to visit dead last, late 2017, but only after I get all the most important things done in " my " pecking order, which I have thought-out carefully and conservatively. When the speakers are "flying" I will attend to port size.
I am simply conservatively taking my time, spent all of 2016 on this, expect to keep these speakers, need to just optimize them as I see fit.
Have fun, I am !
Jeff Medwin