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In Reply to: RE: GPA Altec 414 alnico vs. MCM 55-1220 : WinISD posted by deathtube 667 on February 23, 2015 at 12:34:12
Those would seem to be my T/S measurements... I'm pretty sure when I originally posted them I explained why Fs and Qts usually test high for me (drivers not broken in and sitting face up on the dining room table). Originally, and here again, take them as a single data point.
In any case, GPA publishes the T/S for those drivers. Again, use those and not mine.
I have mine in 4.5cu ft, tuned to around 28hz. I like them an awful lot. Keep in mind my amplifiers have 2-3ohm output impedence.
Follow Ups:
What made you select 414 vs. 416 or 515?
I recently got a chance to hear Valencia w/416 woofers and was not that impressed with them, but I think the set had not be properly serviced before the audition.
Thanks for the info on 414.
I figured that the 414 would be a better directivity match to the horn/driver that I'm using (GPA 802 plus 50deg concial horn), and that it would work in a smaller box. For my setup, I'd need a > 10cu ft box for the 416. Not that I don't still think about upgrading to the 416/288 combination...
I have been reading conflicting reports on how to use the 414 in a vented enclosure.
WinISD indicates using a 1.2 cu. ft. box tuned to around 47 cycles based on the published T/S parameters for 414-8B/C.
Then others are using them in 614 cabinets or whatever that are a bigger.
Not sure what to do at this point.
A friend is dropping off some Magnavox alnico 12" , so I will measure those in ARTA and see if they are useful.
I think that an individual's setup should help dictate what the implementation looks like.
I know that I will be using amplifiers with ~2ohms of output impedence, so I should use that data point when calculating box size and tuning.
Further, I know that I need to factor in room gain -- I need to allow for some boost from boundary reinforcement without bass becoming too much and unbalanced versus 10k-20k roll-off (802s don't go to 20k).
So, when modeling an enclosure I typically aim for a low-Q roll-off, starting pretty high, and is down 3db by 50hz. That's what works well for me.
I changed direction and got a pair of Altec 808-8A alnico drivers for my 811B horns.
They had new diaphrams installed and were less costly than the GPA 802G.
Now that I will have comp drivers I can crossover lower, it might make more sense to go for a 416 or 515 woofer vs. 414.
I'll need to think on it a bit more.
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