I have some Altec 803B woofers that were more recently reconed with the modern 035400 cones. Trying to figure out the right cabinet, but I notice there’s quite a difference in Vas. The original 803B/416A had a Vas of about 1050, whereas the later Altec 416-8B seems to be about half that. In my mind, I would think that Vas follows the cone, but I’d like to hear from those knowledgable on the subject.
I tried to measure the Vas by adding weight, however, I don’t have signal generator that goes below 20 hz at the moment. The fs of the woofer I tested was 22.3 hz, so I could only add the weight to get to 20 hz, which ended up being 16 grams, probably not enough for an accurate measurement…I got about 75 Vas which doesn’t seem possible.
So, if it’s obvious that Vas follows the cone, I’ll go with that, otherwise I might need to buy a function generator.
Thanks in advance!
I tried to measure the Vas by adding weight, however, I don’t have signal generator that goes below 20 hz at the moment. The fs of the woofer I tested was 22.3 hz, so I could only add the weight to get to 20 hz, which ended up being 16 grams, probably not enough for an accurate measurement…I got about 75 Vas which doesn’t seem possible.
So, if it’s obvious that Vas follows the cone, I’ll go with that, otherwise I might need to buy a function generator.
Thanks in advance!
Well sometimes I often ignore the generic " break in" theory's
But paper accordion edge or cloth accordion edge speakers
are going to be rather different in the beginning because of the
black edge treatment.
22.3 Fs sounds very low and impressive.
75 Vas does sound impossible but if double to 140
would make sense.
Either way its a 15" so 3 to 4 cubic feet be rather standard.
From the sound of it is gonna swing more to a smaller volume.
With measurements done after some run time.
I would just build a quick box of 3 cubic feet.
and just start listening to the woofer.
Then measure again after many hours of operation.
All in all things will shift. You can tune the box to high
at 35 Hz with 3 round ports. And plugging
One or 2 ports will make the box lower to 20 Hz.
Or for the most part just start enjoying the speaker.
Even a large 3.3 to 3.8 sealed box. to get it moving
But paper accordion edge or cloth accordion edge speakers
are going to be rather different in the beginning because of the
black edge treatment.
22.3 Fs sounds very low and impressive.
75 Vas does sound impossible but if double to 140
would make sense.
Either way its a 15" so 3 to 4 cubic feet be rather standard.
From the sound of it is gonna swing more to a smaller volume.
With measurements done after some run time.
I would just build a quick box of 3 cubic feet.
and just start listening to the woofer.
Then measure again after many hours of operation.
All in all things will shift. You can tune the box to high
at 35 Hz with 3 round ports. And plugging
One or 2 ports will make the box lower to 20 Hz.
Or for the most part just start enjoying the speaker.
Even a large 3.3 to 3.8 sealed box. to get it moving
Hmm, 803B = 416A measured way back when = 21.7 Hz Fs, 1043 L Vas, 0.272 Qt, 0.6 mm Xmax, 38.6 g Mmd.
T/S max flat = 20*1043*0.272^3.3 = ~276.95 L/9.78 ft^3 net
Fb = 0.42*Fs*0.272^-0.96 = ~31.8 Hz
Vas/compliance is its suspension: T/S explained
T/S math interaction explained
Pre T/S I'd use a sealed box and reduce with solid scrap (net Vb) till Fs was raised 1.56x, then net Vb*1.44 = Vas, though in this case one needs a big box to start with. 🙁
edit: re added mass; need to lower Fs < 25%
T/S max flat = 20*1043*0.272^3.3 = ~276.95 L/9.78 ft^3 net
Fb = 0.42*Fs*0.272^-0.96 = ~31.8 Hz
Vas/compliance is its suspension: T/S explained
T/S math interaction explained
Pre T/S I'd use a sealed box and reduce with solid scrap (net Vb) till Fs was raised 1.56x, then net Vb*1.44 = Vas, though in this case one needs a big box to start with. 🙁
edit: re added mass; need to lower Fs < 25%
Last edited:
: < should be > greater than 25%, so ~16 Hz min.
Digging around some more found some re-cone? specs:
Sd = 880 cm^2
Re = 13.1 ohms
Fs = 23.5 Hz
Vas = 510.17 L
Qes = 0.24
Qms = 6.29
Qts = 0.23
Le = 2.7 mH
Pmax = 150 W
Xmax 3.8 mm
Sd = 880 cm^2
Re = 13.1 ohms
Fs = 23.5 Hz
Vas = 510.17 L
Qes = 0.24
Qms = 6.29
Qts = 0.23
Le = 2.7 mH
Pmax = 150 W
Xmax 3.8 mm
Yes, that’s exactly it. With the new cones, are those the new parameters? I think that’s more the 416-8b vas, which is about half of the 416a you had above.
The 416a parameters really don’t seem like you can get much bass without an enormous enclosure, whereas the later 8b seems like it would be happy in 612 size, 6.5 cubic feet or so…
Thanks! Much appreciation for the help!