828-8G 515-8G graph and numbers

[gearfreak]

Nothing terribly formal, just fodder for commentary/posterity/heck of it. From WT3.
Feel free to comment/question if it looks odd, though - I have no particular goal at the moment.

Port openings are 2 7/8 (02.875") x 25 1/4 (25.250") (full width of thier opening)
So... 72.59375 in2
Stacked horn+horn (ports @ floor @ ceiling).

Impedance calc and 'free air'
parameters of
stacked 828-8G 2x515-8G
Top>Bottom>Both

RTop (green)
R(e) 6.780 ohms
F(s) 22.21hz
Q(ts) 0.5663
Q(es) 0.6494
Q(ms) 4.427
L(e) 0.4986 mH

RBot (magenta)
R(e) 6.497 ohms
F(s) 22.21hz
Q(ts) 0.6123
Q(es) 0.7059
Q(ms) 4.619
L(e) 0.4575 mH

Rboth (yellow)
R(e) 3.496 ohms
F(s) 22.21hz
Q(ts) 0.6247
Q(es) 0.7239
Q(ms) 4.555
L(e) 0.2439 mH

[GM]

I've never measured T/S in a vented or horn cab, but I'm surprised these Q values are so high compared to both published and some measured 8Gs that actually bested them a bit, so if you ever have nothing better to do, measuring the raw drivers to get a comparison would no doubt be enlightening.

Anyway, thanks for sharing, can't have too much tech data available.

GM

[Coendert2011]

Shouldn't both peaks be equal for altec recommended 828 br alignment?

A long time ago I measured impedance of my 828 with 515-8g diy look alikes and tuned the port around 75 sq inch. The difference between peaks was much smaller. My cabs are of the reduced volume variant, I sealed off the space behind the horns with a baffle over the entire width.

[gearfreak]

Cool, thanks for the input guys.

I'll get around to pulling one or both of the drivers and testing outside the box. Lots of screws...