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Discussion Starter · #1 ·
Hi all,

Looking to put two 10W6v3-D4 in a ported enclosure paired to a 1kW amp @ 1 ohm.

Enclosure size after driver displacement: ~2 cu ft

I'm looking to tune the box to 32-33Hz. If I model one 4" port (~14" long), I get an air velocity of about 108 ft/s. That's a bit high for my taste (actually, quite high). I'm worried about resonance / chuffing even with the port flared at both ends.

If I model a 6" port, it's going to be too long for the box, so that's out. With a 5" port, I get an air velocity of about 72 ft/s which is much better.

The problem is, I cannot find 5" ports anywhere online. I also need it to be ~25" long.

I was looking at doing a slot port, but if I can find a 5" ID port that would be much easier and more efficient (port takes up less volume in box).

 

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Discussion Starter · #3 · (Edited)

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If you think there is no danger of it being peaky, all you need to do, if you're worried about chuffing, is widen the port and extend it to maintain tuning. But after running all those simulations you must already know this. I don't understand how can you wonder about one aspect while claiming to be certain about the other, when they are both so directly related.
 

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So I don't know where your 5" port is, but no doubt the internet knows. If you can't google it and find it, I don't know why you think anyone here would know where to get it. You're looking for 5" pipe. Think like a plumber, not a speaker freak.
 

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How about a pair of 4" ports or a triplet of 3" ports?:confused:
 

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Discussion Starter · #8 ·
If you think there is no danger of it being peaky, all you need to do, if you're worried about chuffing, is widen the port and extend it to maintain tuning. But after running all those simulations you must already know this. I don't understand how can you wonder about one aspect while claiming to be certain about the other, when they are both so directly related.
I am here to learn! Can you please elaborate on what you mean by peaky? Are you referring to the low tuning? I do have a DSP/EQ and intend to flatten the response as much as I can. (lowering peaks, not raising dips...)

If not the low tuning, do you mean the port resonance frequency (above Fb)?
 

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Discussion Starter · #10 · (Edited)
How about a pair of 4" ports or a triplet of 3" ports?:confused:
Pair of 4" won't work. To get the same tuning, they would be way too long and not fit the box.

Three 3" limits the lowest tuning to about 36Hz again due to the port length. That also bring the resonance frequency way down (peaks at 230-260Hz) which might be audible.

edit: Well, look at this, 5" pipes.

CLEAR 5" Sch 40 PVC PIPE. (5.047" ID, 5.563" OD, .258" Wall, 90PSI, Weight: 2.726#/ft)

CLEAR UV Rated 5" Sch 40 PVC PIPE. (5.00" ID, 5.500" OD, .25" Wall, 130PSI, Weight: 2.73#/ft)
5" PVC Rigid Pipe, SDR26 Pipe, not sch 40 pipe, but will fit sch 40 fittings. .25" wall thickness, 5.5" OD, 5" ID. 160PSI at 73F. Weight is 2.42#/ft. Max length 7' 11". Min length is 3". Wall thickness is slightly less than Sch 40.

No flared ends. If I use one of those, 25" long it'd only have 2.75" before it hits the wall. That's just over half the diameter, far from the suggested port distance to wall of at least the port diameter. Will I run into issues?

Port Flares says:

The following pair of tables show the default recommendations for some common port / flare combinations. Selecting different options, such as allowing some port compression can change these values.
They show the maximum allowable port velocity in metres per second, so that turbulence will not be noticable at the typical Home Theatre seating position. The core limit is where the air in the "core" of the port becomes turbulent, regardless of flare size. Combinations that are core limited are shown in red
The first table is for a sub whose peak velocity occurs at 30z. The second table shows what happens when the velocity peak is at 20hz - note the drop in performance


https://imgur.com/a/pwfP8













 

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I am here to learn! Can you please elaborate on what you mean by peaky? Are you referring to the low tuning? I do have a DSP/EQ and intend to flatten the response as much as I can. (lowering peaks, not raising dips...)

If not the low tuning, do you mean the port resonance frequency (above Fb)?
I mean in terms of SPL it will tend to roll off fast down low, then give a big boost (maybe 5-6 dB) higher (like maybe 50 or 60 Hz). Low frequency extension may be compromised, in exchange for a peaky boost up higher that you usually don't want. Another danger is over-excursion down low, you get less down low, so turn it up not realizing that the driver is over-worked.

I am just speculating, let me look again at what you've got. But to keep this sort of thing away, while tuning low and avoiding chuffing, you usually need alot of overall airspace. The numbers you gave sound low to me.
 

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I don't know, it looks like you aren't too far away from the manufacturer's specs so maybe it is OK.

Why not do a slot port again? The thinking is that they usually take up less space in the box, because they act longer than they really are. Plus JL seems to recommend it.
 

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Discussion Starter · #13 ·
I don't know, it looks like you aren't too far away from the manufacturer's specs so maybe it is OK.

Why not do a slot port again? The thinking is that they usually take up less space in the box, because they act longer than they really are. Plus JL seems to recommend it.
Because it's a lot trickier to build. I'll have to make a 90 degree angle against the sloped back, compared to just plugging in a rounded port.

I'll revisit the slot port again and see what numbers I come up with. (the slot port does take up more space in the box though, so Vb decreases)
 

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For a 5" port you might see if you can find a 5" cardboard mailing tube. I've found them online, but you have to buy them in a pack of a dozen or more. You might be able to find a local shipping store than has one.
 

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Don't wanna deal with a 90* bend and a sloped back? Just fire the port out the side of the box and call it good. I don't see any good reason why that wouldn't work just fine an suv or car trunk. It's how I'm firing the port in my Jeep.
 

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Discussion Starter · #16 ·
Don't wanna deal with a 90* bend and a sloped back? Just fire the port out the side of the box and call it good. I don't see any good reason why that wouldn't work just fine an suv or car trunk. It's how I'm firing the port in my Jeep.
How do you mean, do you have an example drawing/picture?
 

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It's as simple as it sounds. Instead of port coming out the front on the same plane as the subs fire it out the side of the box instead. You really are overcomplicating this in my opinion.
 

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Discussion Starter · #19 ·
It's as simple as it sounds. Instead of port coming out the front on the same plane as the subs fire it out the side of the box instead. You really are overcomplicating this in my opinion.
I see what you're saying. That might work too, I'll graph it up.
 

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I would suggest trying out the "JBL Slipstream" ports. They are very very very close to having an elliptical shape, which is the best possible profile for inlet/outlet conditions of a resonating air mass. You won't find them for sale under that name, but Parts express has them in bulk, cheap. I mean $4 cheap. They're on close out. I bought 20 last year. :)

The chuffing limit on these I reckon is much higher than any cylindrical counter part so they can tolerate higher vent speeds before it becomes non-linear and turbulent. JBL did a lot of research years ago, and they did it so well and because the design was so close to the elliptical profile that Bose had patented, they were sued by Bose, with Bose winning.
 
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