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Aero port vs Slot port

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fatboy slim
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Aero port vs Slot port

Postby fatboy slim » January 1st, 2018, 2:50 pm

I would like to know which port you guys prefer to use for a daily music system. What are the advantages and disadvantages and is there a difference between spl and sq between the two. Enlighten me on this topic please!

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Re: Aero port vs Slot port

Postby X_Factor » January 2nd, 2018, 10:29 am

generally it shouldnt matter what type you use once its properly calculated and sized

slot port will obviously use more material to build

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Re: Aero port vs Slot port

Postby fatboy slim » January 2nd, 2018, 11:44 am

Thanks for the reply. I'm accustom using aero ports but most people nowadays using slot port boxes. Obviously it's going to use more material to build and the box is going to be bigger to compensate for port displacement. I think I'll go with the aero port box design to save trunk space.

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Re: Aero port vs Slot port

Postby Brian Steele » January 2nd, 2018, 12:00 pm

Slot port = more material to build, more difficult to tune, but adds some rigidity to the box.

Aero port = easy to use and tune, looks cool, adds no structural rigidity to the box.

Solution? Go with an MLTL design, which is just one long slot port of varying cross-sectional area folded into a box :).

20180101_092602-2.jpg

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Re: Aero port vs Slot port

Postby ruffneck_12 » January 2nd, 2018, 5:59 pm

aero slot port
You get the extra bracing of a slot port with the improved airflow of the aero port.

You can flare the edges with a router+round over bit . Or use a section of PVC pipe ,or kerf the wood and bend it.

It looks so much better than a regular rectangle hole in a box.
Kerfing is stress to get right, That's a whole post by itself.

PVC
Image

Kerf
Image

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Re: Aero port vs Slot port

Postby kavaninho » January 2nd, 2018, 9:53 pm

^ yes to the kerfing.
Using the slot port and a kerf would allow you to get any desired port area as opposed to fixed diameter aero tubes.
Both has its pros over the other. Routing a round-over on the edge of the port is not enough but its better than nothing.

If your kerf radius is between 2.5"-5" the 12 slit rule of thumb works great from my experience. Don't be afraid to wet the mdf a little to help you out. :shock: :shock:

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Re: Aero port vs Slot port

Postby Brian Steele » January 3rd, 2018, 1:01 am

Some background reading...

http://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf

Conclusions:
1. Good results can be achieved with a flare radius that's equal to the *length* of the vent, but if designing for HIGH output levels, flaring should actually be kept pretty low.

2. BOTH entrances to the vent should be flared. Flaring only one makes the port asymmetric and can increase distortion and cone offset at high playback levels.

Another thing about using long slot vents and aero vents in a box is that the textbook calculations for determining the correct length tend to off a bit, and sometimes by a lot. That means that you need to confirm that you hit the target Fb and adjust the length of the vent accordingly if you didn't (or just live with the difference). It's easier to trim an aero vent than it is to trim a slot vent :).

Finally, another problem with large vents are the organ-pipe resonances that they generate. These are a function of the vent's length, so the longer the vent, the lower the resonances. Typical rule of thumb is that the effective passband of the sub is one octave below the first resonance, so if that resonance is at 100 Hz, the effective passband of the sub reaches up to only 50 Hz.

All of this can be avoided by avoiding the whole box with large vent scenario and model and build an MLTL instead that will take up the same amount of space, and offset the driver in the MLTL to address the first vent resonance. The example I provided above basically hit the target Fb and the "vent" is large enough to keep compression down to less than 2dB at Fb at peak output levels. The driver is offset in the MLTL to reduce the impact of the first vent resonance at 200 Hz, pushing the effective upper limit of the design from 100 Hz to 150 Hz (the next vent resonance is at 300 Hz).

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Re: Aero port vs Slot port

Postby Rovin » January 3rd, 2018, 7:51 pm

probably 99% of my daily use ported boxes including competition boxes were aeroported , to my ears d roll off always sounded smoother/nicer than normal slotports & u simply cannot beat how quickly u can retune it , i prefer pvc pipe ports over slot too ...

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Re: Aero port vs Slot port

Postby fatboy slim » January 3rd, 2018, 8:47 pm

thanks rovin audio

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Re: Aero port vs Slot port

Postby ruffneck_12 » January 3rd, 2018, 10:58 pm

Weys boy Brian type all that and can't get a thanks too self :lol:


Anyhow, the flare calculations for bass box pro6. What's the dimensions of the flare they're accounting for?
They don't specify that

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Re: Aero port vs Slot port

Postby fatboy slim » January 4th, 2018, 8:01 am

Brian Steele wrote:Some background reading...

http://jahonen.kapsi.fi/Audio/Papers/AES_PortPaper.pdf

Conclusions:
1. Good results can be achieved with a flare radius that's equal to the *length* of the vent, but if designing for HIGH output levels, flaring should actually be kept pretty low.

2. BOTH entrances to the vent should be flared. Flaring only one makes the port asymmetric and can increase distortion and cone offset at high playback levels.

Another thing about using long slot vents and aero vents in a box is that the textbook calculations for determining the correct length tend to off a bit, and sometimes by a lot. That means that you need to confirm that you hit the target Fb and adjust the length of the vent accordingly if you didn't (or just live with the difference). It's easier to trim an aero vent than it is to trim a slot vent :).

Finally, another problem with large vents are the organ-pipe resonances that they generate. These are a function of the vent's length, so the longer the vent, the lower the resonances. Typical rule of thumb is that the effective passband of the sub is one octave below the first resonance, so if that resonance is at 100 Hz, the effective passband of the sub reaches up to only 50 Hz.

All of this can be avoided by avoiding the whole box with large vent scenario and model and build an MLTL instead that will take up the same amount of space, and offset the driver in the MLTL to address the first vent resonance. The example I provided above basically hit the target Fb and the "vent" is large enough to keep compression down to less than 2dB at Fb at peak output levels. The driver is offset in the MLTL to reduce the impact of the first vent resonance at 200 Hz, pushing the effective upper limit of the design from 100 Hz to 150 Hz (the next vent resonance is at 300 Hz).



Thanks for the reply.

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Re: Aero port vs Slot port

Postby Brian Steele » January 4th, 2018, 3:30 pm

ruffneck_12 wrote:Weys boy Brian type all that and can't get a thanks too self :lol:


(sigh), I gets no respeck.... :)

Anyway, I have two MLTL builds documented at the links below.

Boom Unit - http://www.diysubwoofers.org/projects/home/boomunit/

POC6 - http://www.diysubwoofers.org/projects/other/POC6/

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