I didn't realize there was any difference between replacing a small and large format diaphragm either. So you have to center it?
Just got off the phone with Bill at GPA. He is going to send me one in the mail. He also said that it can be centered with a 200Hz test tone and after centering to do a sweep to see if it sounds ok.
Can anybody suggest a good frequency generator for an android?
Thanks
BillWojo
I didn't realize there was any difference between replacing a small and large format diaphragm either. So you have to center it?
I don't know what the appropriate thickness is, most important that the shim isn't too thick such that the assembly gets stuck on the pole. A quick call to Bill at GPA would be definitive.Originally Posted by BillWojo
You could try just plopping one in, if it buzzes, you'll have to loosen the locating dowels and shim it. Take your time, you're working with eggshells and a 30lb hunk of iron.
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Must be you didn't get the memo.
http://www.greatplainsaudio.com/LgDrvrDiaRepl.pdf
The locating pins on lg format drivers are not fixed. They allow you to remove and replace the same diaphragm in situ. But, they do not allow interchangeability like the guide pins on the small format drivers.
Not all vegetables make good leaders.
Ah I was wondering why the guide pins have phillips head screws. That makes sense!
Guess I'll have to do the same thing when I get my new GPA diaphragms
Your new phragms will have the spider shims packed with them.
Not all vegetables make good leaders.
Bill, thanks so much for posting your experience with the 30904 eq. I'm planning to use it in my next build, but I've never heard the effect it has on Altec horns. Good to know that that ear-splitting midrange is going to be attenuated enough to be worth the effort!
GeeDeeEmm
Sweet!
Does anyone know what the 30904 attenuation curve looks like and what varying the components in the attenuator does to that curve? Thanks.
Kind of surprised since it's designed for a somewhat lower efficiency woofer, so in theory would be shelving down the horn too much.
Regardless, reduce C1 to 'let through' more of the extreme HF. Way back when we were young and spinning vinyl, tapes, 0.1-1.0 uF was the norm depending on the system, so probably a bit more for modern CDs.
GM
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No beyond that the three resistors act as a fixed version of the adjustable attenuator [L-pad/voltage divider] and C1 is a HF bypass cap, so if you already have good Altec attenuators, then you just need to set it with no regard for how rolled off the HF is, then experiment with different caps to 'lift up' the HF to flatten it out to 15-20 kHz or whatever sounds best overall.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
I,m not to worried about the highest frequency's on my system after helping my friend Dave set up my 291-16K drivers on his EV HR9040 horns. At my request we did a frequency sweep after getting everything all wired up. He used a program on his computer and much to my dismay as I watched the digital readout as it did a slow sweep, my hearing fell out at about 10K.
To many years of working in loud machine shops, racing motorcycles and driving with the windows open really took it's toll on me.
Thank God the midrange on my Altecs are so sweet, I still enjoy listening, that won't stop. Still kind of bums me out though.
BillWojo
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