View Full Version : Altec 416-8b BL factor needed

08-02-2013, 08:35 AM
Im trying to find the bl factor for the 416-8b. Ive looked on every data sheet I can find. But its not listed on them. I even called GPA. Bill told me to email him with the question. We unfortunately all know how bad those guys are at replying to emails. So I don't expect to get a reply from him. Although it would be nice if I did.

If anyone here knows it I would be very grateful to have it.


08-02-2013, 08:47 AM

08-02-2013, 09:04 AM
I always forget about that site. Thanks Grumpy.


Earl K
08-02-2013, 09:10 AM
Here's the "official" Altec 416-8b cut-sheet ( with Ts parameters that also include BL factor ) .

- Ironically, this sheet comes from GPAs own web-site .


- I'm now left wondering why Bill wanted communications to be conducted in private . ;)

HINT 1 : You're so much better off measuring your own woofers basic parameters / & then manipulating WinISD Pro ( alpha ) into auto-calculating the rest for you .
- You may just find that Altec had some real QC problems in maintaining those offical figures ( for whatever reason ).

HINT 2 : GPAs ( recent ) re-release of the highly sought after 416-8B would seem to be derived from their own acquired compendium of measured figures ( what GPA has observed in their shop, then tagged to , the publics articulated preferences in response, versus actual measured Ts figures ) . Yes that was a bit cryptic .


HINT 3 : There can be quite a difference between "what people actually like, versus what they think they like" .


08-02-2013, 10:10 AM
Oh wow did I miss that. You see, I actually have the gpa 416-8b drivers. I figure the number for the altecs would give me at the very least an idea of what it should be.

Do any of yall actually know how to measure the bl of a driver?


08-02-2013, 12:02 PM
Directly: destructive (need gap access), accurate, gauss meter in gap.
Indirectly: non-destructive, less accurate, calculated based on other parameters (e.g., woofertester2 or other test jig)

08-02-2013, 12:14 PM
Let me just find my trusty utility knife and slice one of them 416s open. I'll do me some measuring.
Just kidding. I'll have to do some reading one measuring ts specs. I've got most all the test equipment to do it the old fashion way.