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I considered upgrading from MCM-1220 to GPA Altec 414 alnico.
T/S parameters for both drivers measured in ARTA, the 414 by another user and the 55-1220 I measured myself.
Ran both drivers in WinISD and they seemed to perform similar in every parameter.
I guess the 414 could drop in my test boxes with no issue.
I would think a $330 alnico driver would sound a lot better than a < $50 made in Taiwan MCM driver but not sure based on the WinISD data.
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WinISD shows you the performance of an ideal driver in whatever enclosure you're modeling. It doesn't take into account aberrations in the frequency response, distortion, and other issues that don't fit tidily into the T/S parameters.
It's kind of like saying two cars with about 200 HP and 175 Lbs of torque will perform about the same, when one is a Lotus Elise and the other is a minivan.
The WinISD model comes out OK with the nullspace 414 T/S parameters he measured in ARTA.
The T/S parameters taken off the product data sheet and the T/S parameters GPA apparently sent to him are different.
Not sure what is up with that.
The model doesn't seem to work well for my box size and tuning.
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.
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.
You sure about that Qts? I have a pair of 414-8c from them, and the Qts value I have found is around .20-.21. Are the Alnico versions that different?
IME, the ARTA measurements can differ from the published T/S parameters.
The amount of added mass can affect how the data comes out.
I might try running the graphs from the manufacturers data and see what happens.
I have read that the 414 alnico and non-alnico version have the same T/S parameters, no idea if they sound the same or not.
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