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How do you arrange two drivers and one port?

  • Front/Back Opposed Drivers - Side Facing Port

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  • Left/Right Opposed Drivers - Front Facing Port

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  • Dual Front Facing Drivers - Back Facing Port

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  • Dual Front Facing Drivers - Side Facing Port

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  • Front & Bottom Facing Drivers - Front Facing Port

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Discussion Starter · #1 ·
You have two drivers and one port.


Where do you place them on your enclosure?


You can vote for more than one, but please limit it to your top three.


One additional caveat, I will be building two of these, so they can be mirrored.


(FYI, there are more options than what I can poll)
 

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Dual opposite side opposed drivers in a stiff box with bracing between the drivers. This will greatly reduce driver vibration into the box as it will cancel, meaning lower cabinet resonances and less chance of it walking.




I'd also thoroughly brace the box.


I would use a well proportioned port to reduce compression, with 2:1 flaring on either end, also to reduce compression but also to delay the onset of chuffing. I'd also place the port on the rear or bottom (with enough floor clearance) of the enclosure so that any stray HF artefacts or occasional chuffing is reduced in audibility.
 

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Quote:
Originally Posted by theater_lover /forum/post/17003592


What are the benefits of doing opposed subs on the sides, versus front and back, or even top and bottom?

Side to side vs front/back = can be placed flush against the wall.

Side/side vs top/bottom = no cone sag.
 

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Discussion Starter · #7 ·
How much of a factor is cone sag with downward and upward facing drivers?

Is it worse for upwards facing? Is this something that occurs after years or months? If it is an issue, why do so many designs feature downward facing drivers?
 

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Quote:
Originally Posted by theater_lover /forum/post/17006072


How much of a factor is cone sag with downward and upward facing drivers?

It depends upon the driver suspension compliance. Here's how to calculate it.
Driver Orientation by Dan Wiggins
Quote:
Originally Posted by theater_lover /forum/post/17006072


Is it worse for upwards facing?

I would think it would be the same unless local gravitic effects are different for each driver.

You would also need some sort of strong grille that didn't interfere with driver action in case somebody places something on the top of the enclosure/driver.
Quote:
Originally Posted by theater_lover /forum/post/17006072


Is this something that occurs after years or months?

The paper above seems to indicate it will be OK, and the author is no dill, but I have no expreience, so others will need to comment on long term.
Quote:
Originally Posted by theater_lover /forum/post/17006072


If it is an issue, why do so many designs feature downward facing drivers?

It may not be an issue and it's easire to make a box with all sides finished without a visible driver for domestic acceptability.
 

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Discussion Starter · #9 ·
That is some great info. Thanks.

Which setup would provide the greatest non-directionality of bass?

If I was using these for stereo subs (left and right mains), would I want them to be more directional, such as front firing? Or would side or bottom be best for room filling bass?


I know low frequencies are supposed to lose their point of origin in a room, but I have always been able to tell.
 

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I would set the distance between the sides with the two drivers based upon how they fit physically with bracing like the pic I posted. The other box dimensions would fall into place with required volume and potential height limitations etc. With most drivers that would mean the distance between them is a small fraction of a wavelength at 60-80Hz and so will act as a point source. With proper filtering, you should not be able to locate them.
 

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Discussion Starter · #11 ·
I understand the idea of bracing the drivers, but is minimal distance between the two required? Or is the bracing the key? I have been thinking of making a slotted port that's walls could act as a brace.
 

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Quote:
Originally Posted by theater_lover /forum/post/17007245


I understand the idea of bracing the drivers, but is minimal distance between the two required? Or is the bracing the key?

Shorter braces are my preference, but if there was a stiff tube of say aluminium connecting the magnet assemblies under compression that would also be fine. If you do this, be sure to drill some holes in the sides of the tube to allow any polepiece vent air to circulate into the main box.
Quote:
Originally Posted by theater_lover /forum/post/17007245


I have been thinking of making a slotted port that's walls could act as a brace.

I'd need to see a drawing.
 

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Discussion Starter · #15 ·
Would there be any benefit to doing opposed drivers that were not directly back to back, but if one was lower than the other?


I was thinking I could make a thinner, taller subwoofer if I could place one driver above the other, with one on the front and the other just lower on the back. I would then brace the rear of each driver's magnet against the inner baffle of the others driver.


Obviously this would not be as good as if they were back to back, but would it be worthless?
 

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You wont get the same benefits as the reactive motion of each driver will be flexing the opposite panel.
 

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My guess would be no, except potentially for a narrower baffle.
 

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"I would use a well proportioned port to reduce compression, with 2:1 flaring on either end..."


Please clarify this for me.

Does that mean for every 2 units the port increases in length, the openning of the port will flair 1 unit wider?

Or vice-versa?
 
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