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Hurtin' Feelins' errrday
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This is actually a good thread.

My next few boxes will have 45's in them. In the past, I haven't used any.

Wondering if things would change if the port piece edge/corner if it was cut at an angle or rounded.....if it would help any? Below the green line
 

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Ive personally never gained by using 45's, so to me its more of an appearance thing when being built (or even hepls brace in corners?). But everyones results will be different. To me its a waste of time. Good box design will overcome everytime
 

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A port is a vent. When the woofer moves inwards it's forces the air out of the box. When it moves out it sucks air in. If you have enough port area it won't really don't help if the turbulence isn't high enough you have no compression/resistance. That being said there is a ideal about of Port areach and to much has hurt my score. Probably the reason some people lost output..
 

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Discussion Starter #24
This has been my experience on 3 different enclosures... yet some people I've talked to swear they have gained with angles, hence trying to see if someone has some solid testing data here they can share. =)


Ive personally never gained by using 45's, so to me its more of an appearance thing when being built (or even hepls brace in corners?). But everyones results will be different. To me its a waste of time. Good box design will overcome everytime
 

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Old thread I just decided to browse through, something I had actually researched heavily in the past. A lot of the comments made here were partially true, just from intuition, but the physics behind it is interesting. Without going into moments and/or moi, I will just point out that pressure, specifically the direction of the force vector in pressure, is defined as being perpendicular to the walls of the (in this case subwoofer) box, which is preventing the force from becoming a sheer force.


But in a 90 degree hard corner, the transition from pressure on one wall to the other is very abrupt. In reality, the corner introduces a pressure gradient, and in the case of hydraulic pressure a sheer force. That's why you never see hydraulic cylinders without rounded corners. Pneumatic pressure is more forgiving, and the tiny gradient creates a small pressure difference. Remember this.

The nearby pressure tries to equlibriate to the corner pressure. It would take more acoustic energy to pressurize the chamber with hard corners than say a cylinder or sphere of the same volume. Why? Sound pressure is oscillating pneumatic pressure; the chamber pressurizes, and relieves pressure into the vent in a ported box, and then reverses the process. For a given speaker "stroke" there is a defined amount of energy that is transmitted into the box volume. This energy is the same energy, that excites the port volume. Given the energy must be conserved, any loss of energy would result in less port excitation. This is where the loss of pressure energy in hard corners comes into play. In an acoustic circuit, it would equate to small resistors, one for each hard corner, especially the tri axis intersections. So he assumption that box rise was lowered is correct, though the volume displacement may have also been a factor in spl results. The size of the 45 is not critical, the more "round" the corner the better. Hard corners in a port will have a turbulent effect as well, but the oscillating air in the port doesn't see the same effects as in the pressure chamber. The argument that air " flow" is better in the box is not true.

I did one build, with decreasing box rise as much as possible the main goal. Dividing flat surfaces into equal "pressure chambers" and eliminating all hard corners were the two initial objectives.





Compared to the previous/initial build, where the volume was essentially the same with no 45s, the rise went from 2.7 times rise down to 2.3 times, at the minimum impedance.

A lot of variables other than just the internal geometry changed, so I can't say for sure that the decrease in rise was purely due to the angled corners. The frequency at the minimum impedance moved from 35 to 36, and the box volume as calculated by solidworks was about 0.1 cubes smaller. But same ports, same drivers, same baffle placement, even the same runs of speaker wire. Seems like there's some evidence in there to support the physics.
 

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newbie forever
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if properly placed 45 degree angles will always help. using a router to have completely rounded corners help even more. air does not like to travel across sharp edges and can get trapped in corners causing a static air space. 45's or rounded corners should be placed along the project airflow path. other area's not direct with the air flow wont matter much. also depending on how large the 45 or rounded corners are it can also increase box integrity thus reducing box rise. so yes beyond question 45s help but be wise with the locations that they are set.
 

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newbie forever
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A port is a vent. When the woofer moves inwards it's forces the air out of the box. When it moves out it sucks air in. If you have enough port area it won't really don't help if the turbulence isn't high enough you have no compression/resistance. That being said there is a ideal about of Port areach and to much has hurt my score. Probably the reason some people lost output..
you want the port to flow as smooth and easy as possible however you also want placements of sub vs port to create resistance. 1 big reason why port directly inline with the sub tend to have less than desirable results. always make the sub work to move that air but yet smooth line the airflow direction to. thats why for example so many suv boxes with subs up and port back work out so well. redirection of air flow causes self resistance yet still smooth out the airflow so static voids do not appear. a smoke machine really helps to show what im talking about. fill the box with smoke and run at low power and then you can see the area's that air gets hung up. make mods (45's or rounded edges) to free that trapped air.
 

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Discussion Starter #28
Do you have some before/after data you can share?


you want the port to flow as smooth and easy as possible however you also want placements of sub vs port to create resistance. 1 big reason why port directly inline with the sub tend to have less than desirable results. always make the sub work to move that air but yet smooth line the airflow direction to. thats why for example so many suv boxes with subs up and port back work out so well. redirection of air flow causes self resistance yet still smooth out the airflow so static voids do not appear. a smoke machine really helps to show what im talking about. fill the box with smoke and run at low power and then you can see the area's that air gets hung up. make mods (45's or rounded edges) to free that trapped air.
 

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If pressure gradients are responsible for poorer performance in vented enclosures without 45's, do they work the same way in sealed enclosures? You should see a noticeable change in the impedance response if so. The air inside a vented enclosure is not pushed out of the vent like water being sprayed from a hose. It acts as a resistive "cushion" that bounces the slug of air in the port back and forth (so low mentioned this already), so any effect that you see in a vented enclosure should also show up in a sealed enclosure.
 

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SPL Retard
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Original box:
41hz - 141.5db - 587 watts (7.41 ohms)
42hz - 141.9db - 561 watts (7.72 ohms)
43hz - 142.2db - 568 watts (7.11 ohms)
44hz - 142.3db - 595 watts (6.24 ohms)
45hz - 142.1db - 689 watts (5.41 ohms)

After adding the 45 degree angles
41hz - 141.7db - 668 watts (7.07 ohms)
42hz - 142.0db - 637 watts (7.40 ohms)
43hz - 142.3db - 633 watts (7.06 ohms)
44hz - 142.5db - 663 watts (6.15 ohms)
45hz - 142.5db - 757 watts (5.34 ohms)


The power delta in every result *should have* resulted in a +.6dB gain. Theoretically. And at these power levels, it probably should have.

I would like to see a retest with the original box after having removed the 45's and using the added power that the second test utilized.
 

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If pressure gradients are responsible for poorer performance in vented enclosures without 45's, do they work the same way in sealed enclosures? You should see a noticeable change in the impedance response if so. The air inside a vented enclosure is not pushed out of the vent like water being sprayed from a hose. It acts as a resistive "cushion" that bounces the slug of air in the port back and forth (so low mentioned this already), so any effect that you see in a vented enclosure should also show up in a sealed enclosure.
Sort of, except that the goal of the rear chamber in a sealed enclosure is only to absorb the rear wave energy of the cone, not to transfer the energy to a resonator. From this argument, the more sharp angles you can create in a sealed enclosure, the better.

Really though, the efficiency of the geometric shape used for the enclosure means more than the corner geometry alone. There is a lot of do***entation covering these variations, from trapezoids and cylinders even spheres. Each shape will shift the system a slightly and made for a different sound.

Original box:
41hz - 141.5db - 587 watts (7.41 ohms)
42hz - 141.9db - 561 watts (7.72 ohms)
43hz - 142.2db - 568 watts (7.11 ohms)
44hz - 142.3db - 595 watts (6.24 ohms)
45hz - 142.1db - 689 watts (5.41 ohms)

After adding the 45 degree angles
41hz - 141.7db - 668 watts (7.07 ohms)
42hz - 142.0db - 637 watts (7.40 ohms)
43hz - 142.3db - 633 watts (7.06 ohms)
44hz - 142.5db - 663 watts (6.15 ohms)
45hz - 142.5db - 757 watts (5.34 ohms)


The power delta in every result *should have* resulted in a +.6dB gain. Theoretically. And at these power levels, it probably should have.

I would like to see a retest with the original box after having removed the 45's and using the added power that the second test utilized.
I agree, it seems like spl should have gone up more at certain frequencies even if it was a difference of 60-80 VA. I never tested my results by spl, just impedance alone.
 

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Hurtin' Feelins' errrday
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12,531 Posts
Original box:
41hz - 141.5db - 587 watts (7.41 ohms)
42hz - 141.9db - 561 watts (7.72 ohms)
43hz - 142.2db - 568 watts (7.11 ohms)
44hz - 142.3db - 595 watts (6.24 ohms)
45hz - 142.1db - 689 watts (5.41 ohms)

After adding the 45 degree angles
41hz - 141.7db - 668 watts (7.07 ohms)
42hz - 142.0db - 637 watts (7.40 ohms)
43hz - 142.3db - 633 watts (7.06 ohms)
44hz - 142.5db - 663 watts (6.15 ohms)
45hz - 142.5db - 757 watts (5.34 ohms)


The power delta in every result *should have* resulted in a +.6dB gain. Theoretically. And at these power levels, it probably should have.

I would like to see a retest with the original box after having removed the 45's and using the added power that the second test utilized.

Or...use the same box w/o the 45's in it...do a test. Jot down results. Then add the 45's in it. Then do 2nd test. Then compare the 2 tests and see if anything is gained.
 

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newbie forever
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again place the 45's in a manner of which will help increase air flow. some area's depending on the build might not need or even call for no 45's
 

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Discussion Starter #34
The 45's were placed in the manner typical of the pictures the "pretty box" guys are using, in the corners where the port is changing direction and opposite angles to the woofer to eliminate the 90 degree corners.


again place the 45's in a manner of which will help increase air flow. some area's depending on the build might not need or even call for no 45's
 

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Discussion Starter #35
It's definitely in need of further testing, power in numbers!
Which is why I was hoping others would have data to contribute as well =)


Original box:
41hz - 141.5db - 587 watts (7.41 ohms)
42hz - 141.9db - 561 watts (7.72 ohms)
43hz - 142.2db - 568 watts (7.11 ohms)
44hz - 142.3db - 595 watts (6.24 ohms)
45hz - 142.1db - 689 watts (5.41 ohms)

After adding the 45 degree angles
41hz - 141.7db - 668 watts (7.07 ohms)
42hz - 142.0db - 637 watts (7.40 ohms)
43hz - 142.3db - 633 watts (7.06 ohms)
44hz - 142.5db - 663 watts (6.15 ohms)
45hz - 142.5db - 757 watts (5.34 ohms)


The power delta in every result *should have* resulted in a +.6dB gain. Theoretically. And at these power levels, it probably should have.

I would like to see a retest with the original box after having removed the 45's and using the added power that the second test utilized.
 

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