One rule of thumb w.r.t port velocity recommends from 5% (small port) to 10% (large port) of the speed of sound (344m/s. Even a single 3" tube is a large port.. Whether or not you actually hear port chuffing also depends on the shape (irregular causes more turbulence) and the port mouth termination (flared) and the power level. It's a squishy number.
BTW the rear chamber volume calculated by Hornresp, also excludes the volume taken by the rear driver basket and magnet as well as port tube volume.
[edit] At 320w, the woofer displacement is +/10mm@30Hz and it exceeds Xmax at lower freq, so you might want to consider a HP filter.
BTW the rear chamber volume calculated by Hornresp, also excludes the volume taken by the rear driver basket and magnet as well as port tube volume.
[edit] At 320w, the woofer displacement is +/10mm@30Hz and it exceeds Xmax at lower freq, so you might want to consider a HP filter.
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round ports work better. Flared port ends help too.
"22.13 m/s velocity @25hz @ 320W" thats probably good enough to try.
"22.13 m/s velocity @25hz @ 320W" thats probably good enough to try.
I’d put that in a 40L box. 1.4ft3. I think the tiny size is meant for a car maybe. Why else does a sub need to be so small?
Otherwise, increase port frequency, and reduce port x-section. That will drop the length down, at the cost of a FR rise around 40-50 Hz and other distortions. You don’t have a choice, unless you want the port sticking out the box. That response is ruler flat, and it doesn’t have to be. You might need a high pass at 30Hz anyway with that much power.
Otherwise, increase port frequency, and reduce port x-section. That will drop the length down, at the cost of a FR rise around 40-50 Hz and other distortions. You don’t have a choice, unless you want the port sticking out the box. That response is ruler flat, and it doesn’t have to be. You might need a high pass at 30Hz anyway with that much power.
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Okay, everyone thought I would share some photos of the current build. My next question is about dampening. I know the industry standard is polyfill. Are there better materials? I watched a few videos and read a few posts. There seems to be a disagreement on what's best and how much to use. I would like to summon the power of this forum once again.
I accidentally cut a full pass on the baltic birch (double baffle). Thank god no one will see it. The reasoning was screws don't work so well with MDF. All material is 3/4 of an inch. This thing is heavy already. Another lesson learned was if my vent went any higher I would have a real tough time with the wiring, and it would be impossible to solder terminals, and the wires would be dancing in the vent. In my next build, if there ever is one, I will definitely snake the ports on the bottom instead of an L shape. The front baffle is not finished. I still have to round over the outside.
I accidentally cut a full pass on the baltic birch (double baffle). Thank god no one will see it. The reasoning was screws don't work so well with MDF. All material is 3/4 of an inch. This thing is heavy already. Another lesson learned was if my vent went any higher I would have a real tough time with the wiring, and it would be impossible to solder terminals, and the wires would be dancing in the vent. In my next build, if there ever is one, I will definitely snake the ports on the bottom instead of an L shape. The front baffle is not finished. I still have to round over the outside.
I want to say 1.65-1.7 net 2.13 total internal. Port tuning 28-29hz port area 16 square. The vent length is 27 -28 ish, so I have to double-check. I rounded both ends with a round-over bit. The box is 18 H 15 W 18 D. A lot bigger than I wanted, but it made the build easier.
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Will be doing some tests with REW to see the in-room response. Have not dampened internals yet—dry box.
Does anyone have any insight on best practices for dampening internal cabinets? Polyfill, foam, insulation? As well, as any good forum posts or links on painting?
Ported subs generally don't require any damping. The frequencies produced are too low and wavelengths too long for damping to have any effect.
Correct.
Asking for suggestions on absorption material will be the usual can of worms.
I do not use home insulation of any type.
Fiberglass is itchy and also bad to breath.
Far as the actual absorption quality is same as many others.
Common safe product is non glass fiber.
Aka poly fill or poly batten.
Reflex/ported cabinets usually lined
So common poly batten sheets.
Available at fabric store in rolls or big box stores
like Walmart. Usually " Super" Walmarts are the ones
with fabric departments.
Poly batten sheets sold for quilt blankets or comforter
blankets
Asking for suggestions on absorption material will be the usual can of worms.
I do not use home insulation of any type.
Fiberglass is itchy and also bad to breath.
Far as the actual absorption quality is same as many others.
Common safe product is non glass fiber.
Aka poly fill or poly batten.
Reflex/ported cabinets usually lined
So common poly batten sheets.
Available at fabric store in rolls or big box stores
like Walmart. Usually " Super" Walmarts are the ones
with fabric departments.
Poly batten sheets sold for quilt blankets or comforter
blankets
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If that is the case, why do manufacturers like SVS et all fill the cabs? Not trying to be difficult.
...because maybe they know that no vented cab is "perfect", and there will be distortion generated by the driver and panel resonances and there's also the harmonic vent resonances to be dealt with, and the easiest way to deal with all of that is to fully damp the enclosure and retune it accordingly 🙂
Most damping material is not effective at low freq (port tuning) so it appears transparent. The damping is for higher freq. This is a good Absorption Calculator and the list of Acoustic Resistivity Tables
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