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Blue Collar Audiophile
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I'm about to build a ported box for my Dayton ho10d4 and I'm getting some strange vent mach results with winisd. Box will be 1.2 tuned to 29hz with sub firing into the seat of my single cab truck and port(s) out the side. I'm going to use an aeroport over a plain slot. What I'm second guessing is how the vent mach is way lower with a pair of 2" ports vs a single 3" port. The single 3" port is just shy of being in the red for vent mach. Am I missing something here or is winisd just plain wrong on this one? Common sense says the pair of 2" ports should have a slightly higher vent mach since the pair has slightly less area than a single 3" port. I'll have 600rms available for the sub but it will never see anywhere close to that for daily listening. Been wanting to try this sub ported for a while and it's an itch that needs to be scratched.

 

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Blue Collar Audiophile
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Discussion Starter #3
The first screenshot is a pair of 2" ports. A single 4" port will be 30" vs the 14ish inches each 2" port would be.
 

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The first screenshot is a pair of 2" ports. A single 4" port will be 30" vs the 14ish inches each 2" port would be.
Weird... Vent velocity should be much higher for the two 2" versus the single 4". Even the single 3" of your first post should be lower velocity than two 2". Area of a 3" tube is 7.07 in^2. Area of a 2" tube is 3.14 in^2, so two 2" tubes would be 6.28 in^2.
 

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Blue Collar Audiophile
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Weird... Vent velocity should be much higher for the two 2" versus the single 4". Even the single 3" of your first post should be lower velocity than two 2". Area of a 3" tube is 7.07 in^2. Area of a 2" tube is 3.14 in^2, so two 2" tubes would be 6.28 in^2.
Would you feel confident running a 3" aeroport in my situation or do you think chuffing would be an issue way below full excursion? I do know from experience that this subwoofer lets you know in a hurry when it's pushed too hard so will baby it when it gets put back into service.
 

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Would you feel confident running a 3" aeroport in my situation or do you think chuffing would be an issue way below full excursion? I do know from experience that this subwoofer lets you know in a hurry when it's pushed too hard so will baby it when it gets put back into service.
3" was too small for my 12" HO. Not sure about the 10". I can model it later this evening and get back to you.

With a double-flared aeroport you can get away with higher velocity (perhaps up to 40 m/s or more) without chuffing than with an ordinary tube or slot port of same area. However, for maximum output, you'll want to avoid port compression by staying below ~22 m/s vent velocity ...at which point flared ends shouldn't matter much/at all.

BTW, excursion is not a factor for vent velocity, as the cone barely moves at Fb (tuning frequency), when the vent is most active.
 

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I can model it for you in Bassbox Pro when I get a chance later if you want.
 

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3" was too small for my 12" HO. Not sure about the 10". I can model it later this evening...
Imagine if someone read this out of context?! Lmao :p
 

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3" was too small for my 12" HO. Not sure about the 10". I can model it later this evening...
Imagine if someone read this out of context?! Lmao <img src="http://www.diymobileaudio.com/forum/images/smilies/tongue.gif" border="0" alt="" title="Razz" class="inlineimg" />
I read it before I read yours and didn't think twice. Once you pointed it out it was pretty funny.
 

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Modeled Dayton RSS265HO-44 10” in WinISD Ver. 0.7.0.950 @ 1.2 ft^3 at 29 Hz, 600 watts:

58.85 m/s with one 3” x 16.60” tube.
66.22 m/s with two 2” x 15.25” tubes.
33.11 m/s with one 4” x 30.49” tube.
29.43 m/s with two 3” x 35.40” tubes.

One of these should be fine for “daily listening” (well under 600 watts, as you describe it – for example, 41.6 m/s at 300 watts, or 34 m/s at 200 watts): https://www.parts-express.com/precision-port-3-flared-speaker-cabinet-port-tube-kit--268-350

…or one of these for the full 600 watts (if you’ve got room for a 2.0 ft^3 box, for a 17” vent length, at 46.5 m/s): https://www.parts-express.com/precision-port-4-flared-speaker-cabinet-port-tube-kit--268-352

<edit> While for some strange reason I'm getting a flatline excursion plot, given PE's 1.5 ft^3 vented volume recommendation I would be remiss to suggest that this driver would handle the full 600 watts in 2.0 ft^3.
 

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Would you feel confident running a 3" aeroport in my situation or do you think chuffing would be an issue way below full excursion? I do know from experience that this subwoofer lets you know in a hurry when it's pushed too hard so will baby it when it gets put back into service.
Having re-read your first post, yes I would confidently go with 3" (in particular, one of these: https://www.parts-express.com/precision-port-3-flared-speaker-cabinet-port-tube-kit--268-350 )
 

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Blue Collar Audiophile
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Discussion Starter #14
Having re-read your first post, yes I would confidently go with 3" (in particular, one of these: https://www.parts-express.com/precision-port-3-flared-speaker-cabinet-port-tube-kit--268-350 )
Thanks. Yeah I just use the sub for blending purposes and have always enjoyed my ported setups more than my sealed setups but have mostly run sealed out of necessity. You can do a lot more behind the seats of a single cab Ram than you can under the back seat of a quadcab like I used to own because the single cab has more usable room without having to fiberglass.
 

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Modeled Dayton RSS265HO-44 10” in WinISD Ver. 0.7.0.950 @ 1.2 ft^3 at 29 Hz, 600 watts:

58.85 m/s with one 3” x 16.60” tube.
66.22 m/s with two 2” x 15.25” tubes.
33.11 m/s with one 4” x 30.49” tube.
29.43 m/s with two 3” x 35.40” tubes.

One of these should be fine for “daily listening” (well under 600 watts, as you describe it – for example, 41.6 m/s at 300 watts, or 34 m/s at 200 watts): https://www.parts-express.com/precision-port-3-flared-speaker-cabinet-port-tube-kit--268-350

…or one of these for the full 600 watts (if you’ve got room for a 2.0 ft^3 box, for a 17” vent length, at 46.5 m/s): https://www.parts-express.com/precision-port-4-flared-speaker-cabinet-port-tube-kit--268-352

<edit> While for some strange reason I'm getting a flatline excursion plot, given PE's 1.5 ft^3 vented volume recommendation I would be remiss to suggest that this driver would handle the full 600 watts in 2.0 ft^3.
That's the version I used (0.7.950) for the results posted above. Seems to have worked properly.

<edit> ...at least with respect to vent velocities - not sure what's going on with the flatline/zero excursion.
Erroneous flatline/zero excursion explained: I had accidentally clicked "Cone excursion (PR)" instead of "Cone excursion." :blush: Result: 2.0 ft^3 at 29 Hz, excursion is just under Xmax (13.09 mm at 38.2 Hz) at 400 watts.
 

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I really wish I had the Polk Audio whitepaper on their special port design. I lost it long ago and it was supposed to be a free release but now it is gone. Its the one that has the spike in the middle of it, going into the port. Supposed to be for floor-stander subs inside their main towers. There's a pair in the basement, I might have to go get some pics. Anyway, that port makes zero noise and uses the space very nicely.
 

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I really wish I had the Polk Audio whitepaper on their special port design. I lost it long ago and it was supposed to be a free release but now it is gone. Its the one that has the spike in the middle of it, going into the port. Supposed to be for floor-stander subs inside their main towers. There's a pair in the basement, I might have to go get some pics. Anyway, that port makes zero noise and uses the space very nicely.
Interesting... I'd love to see pictures.

However, I wonder about vent compression. It is my understanding that with ordinary vents (particularly flared ones), by the time you're hearing vent noise, vent compression will be significantly limiting output potential/vent efficiency.
 
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