I ordered the SB Acoustics SB34 12 inch sub and I'm designing a box for it. WinISD suggests sealed, but I'd go for ported this time. I've never built a ported sub so I need some advice.
I went with the "slot" type port instead of a tube, but I'm concerned that it migh be too small in height and so port noise will occur.
I went with the "slot" type port instead of a tube, but I'm concerned that it migh be too small in height and so port noise will occur.
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It depends on port diameter and flare size. There's a calculator to calculate the maximum allowable velocity. It distinguishes between the onset of chuffing and turbulence. Flare-it - Free Speaker Design Software
That's one nice looking driver.
The sim shows a flat response above 100 Hz. That's highly unlikely, and I'm guessing that the sim isn't taking the driver's inductance into consideration. Such programs can over-estimate the driver's response at the upper end of the bass range.
Concerning vents, I consider anything below 1/3rd Sd as "small" and likely prone to non-linearities (for one of my last builds, I measured 2dB of compression at higher SPL levels due to the vent, and that vent had a cross-sectional area was around 2/3rds Sd).
Given that rule of thumb, a vent for a 12" driver should be around 167 cm^2, or almost 6" in effective diameter, with a length chosen to achieve the target Fb. Smaller than that, and you'll likely end up with a vented box that has different response curves at different SPL levels.
The sim shows a flat response above 100 Hz. That's highly unlikely, and I'm guessing that the sim isn't taking the driver's inductance into consideration. Such programs can over-estimate the driver's response at the upper end of the bass range.
Concerning vents, I consider anything below 1/3rd Sd as "small" and likely prone to non-linearities (for one of my last builds, I measured 2dB of compression at higher SPL levels due to the vent, and that vent had a cross-sectional area was around 2/3rds Sd).
Given that rule of thumb, a vent for a 12" driver should be around 167 cm^2, or almost 6" in effective diameter, with a length chosen to achieve the target Fb. Smaller than that, and you'll likely end up with a vented box that has different response curves at different SPL levels.
I've only tested it in free air without any filtering and anything other than the bass sounds awful. But I'll be filtering everything above 95Hz or so with a 24db/oct active filter so I'm not concerned. The bass sounds really nice and controlled, I've never heard low bass so tight.
We'll see how it sounds in the box. I am concerned that the port is too small in diameter, but if it was larger, it would also be too long.
We'll see how it sounds in the box. I am concerned that the port is too small in diameter, but if it was larger, it would also be too long.
Well, as expected, there is some chuffing. The next pipe diameter I can find is 110mm, which results in about 54cm of port length (longer than it can fit in the box).
As for the sound, it does sound good, of course with everything rattling around in the room.
Measurements look decent, I'd say. No break-in, outside, with walls nearby.
Mind the SPL values, I haven't calibrated the levels. It does roll off higher than expected, even though the box is tuned to 23Hz.
As for the sound, it does sound good, of course with everything rattling around in the room.
Measurements look decent, I'd say. No break-in, outside, with walls nearby.
Mind the SPL values, I haven't calibrated the levels. It does roll off higher than expected, even though the box is tuned to 23Hz.
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The 110mm should be good, I typically use 4" port for a 12" woofer and that seems to work fine for most music, not home theater. It looks like the 54cm port should fit with an elbow and maybe mounting it lower on the baffle.
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