Kevin, thanks or the spreadsheet. The Iconic has a considerably higher Vas than the Altec 515s that are currently available, which makes it work in the Onken a little more reasonably. Are you using a passive crossover between the amp and the driver? I'll be biamping, so I believe Rg will be much lower than 3Ω.
John
John
Hi John,
Yes, I'm currently using passive X-O, at one time I had thought about the possibility of bi-amping, and the idea still crosses my mind from time to time, but overall I am so pleased with the result that I have not bothered.
I'm wondering whether there might not be some drivers that are better suited than the current GPA 515.. Possibilities from P Audio or B&C? There were also some Eminence 15" drivers that seemed a good match to the Onken when I was working on the design..
Wondering whether Iconic would be willing to make you a pair? Not sure what they are doing these days.. Iconic Speaker Manufacturing - Index Page I don't believe my drivers were off the shelf. (Believe they were built on order) They are excellent quality and I've no regrets. I'd email to make sure they aren't able to make you a pair.
I am mistaken here. The Iconic is identical to the currently available Altec ceramic drivers. I was looking at the new Alnico driver which has higher Vas as well as higher Qts and doesn't want to work in the Onken.
John
This is actually very good news. I remember talking to Altec-Sparkomatic, and trying to order that driver from them about 4 1/2 yrs ago, and being told it was discontinued. Shortly after I ordered them from Iconic I was contacted by Altec indicating that they had had a change of heart, and if I was still interested they would be happy to take my order. I have wondered ever since who actually made/makes the Altecs.. (My guess Iconic or GPA) My Iconics are ferrite obviously.
Sounds like the new Alnico ones aren't necessarily very close to the early Altec units which surprises me a little. (or not..)
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I just looked at the GPA 515-8G and the Iconic 165-8G and it shouldn't come as any big surprise that they appear to be one and the same driver. The data sheets are virtually identical in every way - no coincidence there I guess. 
Anyway the prices are MUCH lower than they were a few years go so I would grab a pair of the GPA 515-8G.. Guess the economic mess has one benefit for us diy types.
Anyway the prices are MUCH lower than they were a few years go so I would grab a pair of the GPA 515-8G.. Guess the economic mess has one benefit for us diy types.
Hi John,
Were you looking at the GPA 515-8C? If you are totally crazy and don't mind a really large box and/or a solid state amp on the bass (cross low in that case) you could use this driver. You'd have to keep Rg to 1 ohm or less otherwise the box gets way too big fast. If you can afford a really big box you can get way below 30Hz with this driver with a high Rg and the Onken alignment..(6.34) I assumed that Sd and Mms were the same as I used in my calculations with the 165-8G which might not be the case. Not sure about excursion limitations if you were to do this - and please don't take this as a recommendation to do so..
What I can tell you is I run out of amplifier power long before I run out of excursion.. Mine actually roll off a bit lower than I expected based on the spreadsheet which was a significant bonus.Please take the comments on the GPA 515-8C as a hypothetical exercise, were it me I would not choose this driver for all of the reasons you mentioned. It would probably be better in a horn..
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Hi John,
Were you looking at the GPA 515-8C? If you are totally crazy and don't mind a really large box and/or a solid state amp on the bass (cross low in that case) you could use this driver. You'd have to keep Rg to 1 ohm or less otherwise the box gets way too big fast. If you can afford a really big box you can get way below 30Hz with this driver with a high Rg and the Onken alignment..(6.34) I assumed that Sd and Mms were the same as I used in my calculations with the 165-8G which might not be the case. Not sure about excursion limitations if you were to do this - and please don't take this as a recommendation to do so..
Please take the comments on the GPA 515-8C as a hypothetical exercise, were it me I would not choose this driver for all of the reasons you mentioned. It would probably be better in a horn..
Right now I'm leaning toward your design with the 515-8G. I like the idea of using 86% vent area rather than the full 100% of the original Onken. I haven't seen any 515-8C for sale yet and at any rate I'm sure they will be out of my price range.
John
414-8B as originally published. Don't know how much difference the Z would make.
Apparently I've just been talking to myself since the main point of an Onken alignment is it's high damping factor around/at Fb due to a vent area that ensures a low vent mach, so obsessing over a vent length that exceeds a relatively short arbitrary limit (by (sub)woofer design criteria) that wasn't even a part of the design routine originally AFAIK seems a bit too narrow minded to me. Worst case is you find the vent's harmonics 'color' the lower mids too much (perceived as a lack of clarity/'smearing') in which case you add a bit of damping to each vent to damp its pipe harmonics same as others do.
GM
OK, the EL34 has enough power to cause some vent compression, though of course it has to have a strong signal at the tuning frequency for it to happen, so if vinyl was the source it likely didn't happen. Still, in their driver's heyday, Altec recommended 0.25x Sd minimum, which the 'W' doesn't come close to meeting, so anyone contemplating building one today might want to re-think its vent system for CD, SS, etc..
Never actually built a sand filled cab, though a Wharfedale built this way had no sonic advantage compared to one of my very rigid designs that pushed the cab's Fs well above its XO point, so never bothered. I guess the only way to know for sure if either had at least a theoretical advantage though would be to build two identical alignments except for cab construction and measure them.
Hear, hear!
GM
'New' Altec, Iconic WRT vintage model drivers = GPA built, though there was talk about the 'New' Altec having China tool up to replace them, but AFAIK it hasn't happened.
The Iconic 165 series = GPA 515 series, so unless you spec'd a custom with different T/S specs...........
Iconic was formed primarily to make finished speakers, so it's my understanding that its XO designs are different from GPA's, or at least were originally.
Anyway, Todd White can fill you in on all the details/differences.
GM
If GPA is holding to the measured specs I have of some early 515-8Gs, you'll be hard pressed to improve on them overall, especially at the price, but there's a thread here somewhere about (mid)woofers with the lowest moving mass (Mms), so that's where I would begin searching.
GM
There were no large driver speakers from Onken (the company) AFAIK.
Typical '60s era specs AFAIK:
803B/416A:
21.4 Hz Fs
1042.89 L (36.829313 ft^3) Vas
4 Qms
0.292 Qes
0.272 Qts
12.5 ohms Re
12.7" dia
1.4 mH Le
30 W Pe
3.56 mm (0.14") Xmax (my SWAG)
calc'd:
817.2693 cm^2 (126.677"^2) Sd
17.11 N/A BL
1.1024E-03 mm/N Cms
50.175 gr Mms
97.3 dB/W/m
---------------
416-8A (near enough 416-8Z equiv.):
23.9 Hz Fs
840.246 L (29.673 ft^3) Vas
3.55 Qms
0.27 Qes
0.251 Qts
6.58 ohms Re
12.7" dia
1.26 mH Le
30 W Pe
3.56 mm (0.14") Xmax (my SWAG)
calc'd:
817.269 cm^2 (126.677"^2) Sd
13.61 N/A BL
8.764 E-04 mm/N Cms
50.51 gr Mms
98.14 dB/W/m
GM
Within the same time period, there's very little spec difference between the AlNiCo versions and should be no difference with ceramic motors, so considering the Petite is a very over-damped alignment, it has quite a bit of tuning flexibility via series resistance and/or stuffing some of its vents to raise Fb, ergo should be tunable with any reasonable spec 414/amp combo, even a matching impedance one.
GM
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