First DIY ported sub need help with port

Hello all, I will attempt a ported sub after successfully building my first sealed sub.

My driver of choice is the Dayton Max X 10-inch. Link: https://www.daytonaudio.com/product...-high-excursion-dvc-subwoofer-2-ohms-per-coil

Power will be supplied via Crown XLS 1502.

I will build the box on Dayton's recommendations of 1.1 cubic feet with a tuning frequency of 28-29hz. Currently, I am having trouble figuring appropriate port configuration.

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In WinISD port length is 36 inches when the port area is 4 inches tube, with 24m/s air velocity. Or 46 inches when its a 4 x 4 (16 inch) slot; however it's 46 inches in length. I would have to do a lot of folds just to get that to fit. Then my volume would shrink, so I would need an even bigger box than what Subbox Pro is suggesting.

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Using sub box. pro my port is always outside the box. I input the driver as taking up 0.1ft3
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The issue is the port is stupidly long, with a port velocity of 28 m/s, regardless if it's a slot port or a tube port. My use case is music, so I would like to keep this at a safe level and not have any amount of chuff or distortion, or audible noise. What Can I do to rectify this situation? I am not well-versed in how certain parameters affect others.

It almost seems that the subwoofer cannot be built due to the required port lengths. I have not even added any bracing yet. Is there a software that works better than box pro that is free so I can visualize it? Would be nice if Subox automatically increased my box size to keep the 1.1 interval volume.

Thank you in advance.
 
What driver parameters affect the ability to go low with small port tuning? SVS seems to dig down to 20hz with flat amplitude. I know they have two ports on their ported models, but more ports would = more length, is my understanding. I know they use DSP, I do as well, but their amps are not big either 325W RMS.


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Inside of PB 1000.

Dimensions, 18.9" (H) 15" (W) 20" (D)
 
Vent length can be calculated with this formula, based on physics (and some empirical data for the end correction term).

ventL.png


Use consistent units.

For SI units:
fb = tuning frequency (Hz)
c = 343 m/sec (speed of sound in air)
Vb = box volume (m^3)
R = port radius (m)
Lv in meters

For English units:
fb = tuning frequency (Hz)
c = 13500 in/sec
Vb = (in^3)
R = (inch)
Lv in inches

If it's in your budget, you might consider Passive Radiator(s). Or just use sealed, and use your dsp for gain in lower freq.
I don't have the formula for vent mach. WinIsd and others can do that, as you noted.
 
WinIsd will make a slot port too long.

It is very good for calculating ports that do not share cabinet walls
.732 correction factor for non flared, believe dual flare considered .850

Rectangle slot port has low efficiency and also shares 3 walls.
So it looks longer. And correction factor is much much higher constant.

Looking at the common chart below you will see that end correction
for 3 shared walls = 2.227

you cannot change error factor in Winisd you need to use a sim which you can adjust
Error factor.

in nutshell WinIsd only goes to .850 when you need to be at 2.227
to calculate a slot port sharing 3 walls.
Which will make it shorter.

and yes correct the total volume of the box needs to always be bigger, because the driver
and port remove airspace. So to get correct volume for the speaker the box will
be bigger because the port and driver remove volume.

if your hitting max SPL in winisd to check port velocity then likely making a way bigger port
than needed as well. Since you will hit linear distortion or Xmax way before the thermal rating
of the speaker. WinIsd just applys the thermal rated power you enter you enter . So rather useless to
determine port velocity with full thermal power. Since you will hit xmax below port frequency rather
quickly. Just apply power till it unloads to xmax at around 35 Hz. that is all you get in real life

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It almost seems that the subwoofer cannot be built due to the required port lengths. I have not even added any bracing yet. Is there a software that works better than box pro that is free so I can visualize it? Would be nice if Subox automatically increased my box size to keep the 1.1 interval volume.

You could use Hornresp, its free and there is a dedicated thread here Hornresp Subwoofers where you can get help from it's author and others.

Using your box volume (1.1ft3=31L) with a 3"x10.6" (45.5cm3 area x 27cm long) port tube provides the following response.

[edit] set drive voltage to default 2.83V, replaced graph and design file
 

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You could use Hornresp, its free and there is a dedicated thread here Hornresp Subwoofers where you can get help from it's author and others.

Using your box volume (1.1ft3=31L) with a 3"x10.6" (45.5cm3 area x 27cm long) port tube provides the following response.
What is the correction factor? for the port.

He is trying to design a slot port
correction factor is =2.227
not a round port = .732 to .850
 
careful with the math.
To use the formula in post #5, you need to find the radius of a single equivalent port that has the same total area of the combined multiple ports.
In the case of (2) x 2" ports, the equivalent Radius is 1.414".
Also, maintain consistent units.
For (2) x 2" ports, I get L = 17.89" (~454 mm) for fb = 29 Hz.
 
careful with the math.
To use the formula in post #5, you need to find the radius of a single equivalent port that has the same total area of the combined multiple ports.
In the case of (2) x 2" ports, the equivalent Radius is 1.414".
Also, maintain consistent units.
For (2) x 2" ports, I get L = 17.89" (~454 mm) for fb = 29 Hz.

I don't do well with imperial measurements! I used the cabinet size from his sub-box graphic. This is 1.7 ft3, 50% bigger that the 1.1 ft3 (31L) specified.

Metric: = 47 litres - (Driver, ports, bracing) = 42 Litres.
 
The legend on sub box graphics says 1.1 cu ft net internal volume (not counting the 90 deg slot port), and OP noted that woofer displacement of 0.1 cu ft was accounted for. Calculations on post #12 are based on Vb = 1.0 cu ft (1728 cu in), R = 1.414 in, C = 13500 in/sec, fb = 29 Hz.

For 42 liters (1.5 cu ft tuned to 29 Hz, the response peaks up about 2 or 3 dB, which may (or may not) be acceptable to OP.

A larger port area is likely more suitable for such a high excursion woofer. I'm not sure what the port speed is for either of these cases.
 
The issue is the port is stupidly long, with a port velocity of 28 m/s, regardless if it's a slot port or a tube port.
29Hz is a ridiculously low Fb for such a small box. PE often recommend a box size and port design.
You can’t use a 4” port, 3” might work, maybe even 2”, or a slot port, or a passive radiator. You should increase the size of the box to accommodate the port. The Vb doesn’t increase since port volume is subtracted. Also, I wouldn’t trust WinISD for this, but use more basic Helmhotz calculators, along with testing/measurements of your box with a variety of port lengths. You can often deviate down from the theoretical lengths quite far without noticeable degradation.
 
Why would you make a bunch of guesses and boxes.
Take about 10 mins to get a design in Virtuix Cad.
You can adjust error factor to 2.227 and be done.
29 Hz is about perfect for cone control. It is a sub
PE boxsim recommendations are just about horrible.
WinIsd can predict a transfer function
for a actual standard alighnment no problem
It just cannot predict shared wall port lengths.
 
I enjoy calculating on paper, trial-and-error design, tinkering, measuring and listening. CAD seems more like making a kit to me. “By hand” is not for everyone, but it‘s successful. Multiple boxes is not an issue: The range of acceptable cabinet dimensions is wide, and the results of deviation from the optimum is calculable, no matter what method you use to model response.
True, 29Hz isn’t that low.
 
Thank you all for your replies! Much of this goes way over my head, so please be patient. I have downloaded Hornresp, which has an extremely steep learning curve. I am using WinIsd in conjunction due to its easier-to-use interface.

I have taken the advice to increase box dimensions. However, I am not sure that rectify's my problem.

First off, my initial box of 1.1 net, not including the port volume on HR. Please inform me if any input parameters are incorrect. Not sure what to input for EG.

VRC 31.14 or 1.1 Cu Feet
LRC 50 = 20 Inch deep.
AP 103.26 OR 16 inches


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I get a box that looks like this. 31.14 L for the net box size and 6.7 L for the vent. I still have no idea of my box dimensions and cut panels. Am I doing something wrong in HornResp?

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Response looks like this.
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Port Velocity is rather high, or what I deem to be rather high. All my DIY subs are closed.

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Now onto the bigger box, as suggested at 1.439 In WinISD with a box 1.439ft^3 tuned at 28hz with a vent of 4.02 X 4.02 35 inches total gives me a response that looks like this.
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Using HR with the following parameters.
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I get something that looks like this

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Port Velocity

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Lastly, using HR, how do I go about switching between aeroport's or slot ports?

I agree a tube port would look nicer and is easier to build; however, no idea how to go about calculating values in HR. In WinIsd, it says I can get away with a 4-inch round port 27 inches long.

Apologies in advance if what I am asking was already covered. A lot of this goes over my head.
 

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Thanks for trying Hornresp.

As you've seen, if the port is larger the port will also be longer. The port area (Ap) and port length (Lpt) determine the tuning for a given box volume. The port cross section (round, square, etc) will have a secondary effect on the tuning and is not adjustable in Hornresp. The port internal volume is considered separate from the box internal volume, so you would account for this when building the box. The box depth (Lrc) will determine where internal reflections and resonances occur (the glitches in the freq response).

What max port velocity are you aiming for? do you really need a large area port? I also noticed you are driving Eg=39.03 Vrms (320 watts) is that the max intended?

[edit - port cross section added, port volume]
 
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Hey, so the driver has an RMS of 400W. My crown amps can do 525 @ 4 OHM or 325W at 8. I used 320W as 80% of RMS. As far as max port velocity, I am unsure. I have read that you want to keep things under 18ms. However, I have no real-world experience, so I do not objectively know for sure.

From what I have modelled, the larger the port area, the lower the port velocity. Using 16 inches as the area, I thought 1.1 * 13.5 inches @ 35 inches long gives me a peak of 22.13 m/s velocity @25hz @ 320W. The calculations above are all from WINisd.
 
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