Thank you for your reply.
The AT-15s were vented with a 6" diameter port. I can probably find someone who can and will tell me the length. I have the dimensions for the original enclosures, but wanted to play with some modeling programs to compare those results with the original boxes. The OCD in me likes to start with the basics.
A modeling program makes it easy to see how changes in box volume will influence the port length.
There are always trade-offs, and often many reasonable solutions. Hopefully you can find something that suits you.
There are always trade-offs, and often many reasonable solutions. Hopefully you can find something that suits you.
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The AES2-1984 standard defines Xmax as "the voice-coil one way peak displacement at which the "linearity" of the motor deviates by 10%. Linearity may be measured by percent distortion of the
input current or by percent deviation of displacement versus input current. Manufacturer shall state method used. The measurement shall be made in free air at Fs."
When you drive the speaker with a sine wave at Fs, and see a harmonic reach -20dB below the Fs frequency on an RTA, the speaker has reached Xmax.
Persistence of vision makes it easy to see and measure the peak to peak excursion with a ruler and divide by 2.
Simpler, but less telling of actual linearity:
Xmax = (Voice Coil Length - Height of the Magnetic Gap) / 2
The top plate is the "Height of the Magnetic Gap", easy to measure externally.
The voice coil is 2" in diameter (60mm) looks like the voice coil length is about 21.6 mm:
If the driver's top plate is 10mm, Xmax would be around 5.8mm.
Considering the magnetic gap extends a bit beyond the top plate, some manufacturers may use more lenient mechanical formulas resulting in as much as 40% more Xmax.
These are common:
(Hvc - Hg) / 2 + Hg / 3
(Hvc - Hg) / 2 + Hg / 4
Anyway regardless of your OCD itch, no need to cut up your woofer for an ambiguous parameter you can measure in a variety of ways 😉
Art
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Hello @weltersys,
Thank you for reply.
My calipers are in the shop which is not connected to the house. Eyeballing the top plate with a rule, it appears that the top plate is 9mm. I'll check it with the calipers tomorrow and then run the calculations.
Thank you for reply.
My calipers are in the shop which is not connected to the house. Eyeballing the top plate with a rule, it appears that the top plate is 9mm. I'll check it with the calipers tomorrow and then run the calculations.
@weltersys - I'll be using the speakers in my shop which is fairly small. I'm not one for high SPL due to a damaged right ear.
After yah sim a few drivers which are roughly the same
type of design
Overall specs and magnet size.
I would just expect the same old 3 to 4mm
And my OCD wouldn't let that bother me.
Because its feasible enough this type of woofer.
Higher thermal rating, than linear travel
at 10% distortion. Same old 20 to 30 watts linear/xmax, For home
environment dont need a port much larger than that to keep
velocity at a decent rating. Just enough voltage for 30 watts
and size the ports to give yah around 15 to 20 m/s
Say have seen it many times before with winisd
they apply max power at the thermal rated/ manufacture rating.
When linear travel is likely 20 to 30 watts with 3 to 4mm
drivers of this type.
So many assume you need a huge port applying to much power
in sim. When port velocity at 30 ish watts doesn't need too big
of a port. Which helps keep length down, so yah dont hit the rear
of the enclosure. Round tubes with flare can easily be used.
Rear magnet plate seems to have a little bump to
it. So xlim might be pretty decent. Basically just bump
the rear plate. So its less likely for the coil to smack it
on big transients when your playing at high levels.
Should be fun project, bass with Vegas was never a problem.
Usually just the tweets were little harsh. So just a basic modern
silk dome for 30 bucks sound way way better than some of the mylar
or piezos in some vegas. easy upgrade
type of design
Overall specs and magnet size.
I would just expect the same old 3 to 4mm
And my OCD wouldn't let that bother me.
Because its feasible enough this type of woofer.
Higher thermal rating, than linear travel
at 10% distortion. Same old 20 to 30 watts linear/xmax, For home
environment dont need a port much larger than that to keep
velocity at a decent rating. Just enough voltage for 30 watts
and size the ports to give yah around 15 to 20 m/s
Say have seen it many times before with winisd
they apply max power at the thermal rated/ manufacture rating.
When linear travel is likely 20 to 30 watts with 3 to 4mm
drivers of this type.
So many assume you need a huge port applying to much power
in sim. When port velocity at 30 ish watts doesn't need too big
of a port. Which helps keep length down, so yah dont hit the rear
of the enclosure. Round tubes with flare can easily be used.
Rear magnet plate seems to have a little bump to
it. So xlim might be pretty decent. Basically just bump
the rear plate. So its less likely for the coil to smack it
on big transients when your playing at high levels.
Should be fun project, bass with Vegas was never a problem.
Usually just the tweets were little harsh. So just a basic modern
silk dome for 30 bucks sound way way better than some of the mylar
or piezos in some vegas. easy upgrade
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