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Old 11th September 2013, 10:06 AM   #1
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Default Dual opposed Slot Loaded Port

Greetings Bass Lovers,
I've been having a hard time finding any president for a design idea I have. I may just not know what to call it. I can think of several reasons why this design may be problematic but I keep coming back to it for some reason. The design takes a dual opposed slot loaded subwoofer and integrates the slot as the last part of the port.

This is a quick model I made to demonstrate the idea.
Click the image to open in full size.
My thoughts are that this will provide significant low end extension while not taking up a lot of extra room. The port is lengthened lowering Fb or allowing larger port area for the same Fb, reducing turbulence; the front of the woofers are loaded to improve impedance matching and theoretically lowering Fs; cabinet vibrations are reduced by the opposing drivers(which I would have facing each other); and sharing the slot loaded area with the port mitigates the volume increase.

Has anyone tried this? Does it have a common name? Could this a beneficial trade-off when trying to optimize for low extension and space conservation? I'm imagining some strange resonances/standing waves causing big peaks or dips in the response. This is why I threw that little triangle section where the ports meet. I think the geometry of this area could be a critical factor and any insight would be appreciated. I wonder if the long wavelengths will tend to propagate more towards the lower impedance path, so less energy will pass from the port on one side through to the other.

Please bear in mind this model is just to present the concept and is in no way refined...and yes I searched extensively for an existing thread, please pardon me if I missed it. If this hasn't been done, I do not authorize it's use by others for commercial purposes but DIY away

-Matt Long
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Old 11th September 2013, 02:10 PM   #2
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Hi, this is basicly a tapped horn - bandpass horn hybird, without much actual horn action, so I suppose it's more of a tapped quarter wave tube - bandpass hybird. Certainly stands a chance of working, and could be modeled in hornresp. I would look at the CUBO series of subs, they are tapped - bandpass horns.

Acutally, on 2nd thought, this is pretty interesting for me because I could take my two existing slot ported boxes and strap them together like this. Maybe I'll run a model.

Last edited by turbodawg; 11th September 2013 at 02:13 PM.
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Old 11th September 2013, 04:37 PM   #3
rigtec is offline rigtec  United States
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Hi mattlong8'

Take a look at this, you should see a "very close similarity" to what you're considering; see two links below:

Ported horns

Whats the story on this Subwoofer design? - Wave Music Community Board

rigtec, best regards
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Old 11th September 2013, 04:52 PM   #4
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Rigtec is correct, the OP's design is functionally the same as the EAW SB1001, a ported box with the port exit plenum also housing the speakers.
Of interest, the previous version of the cabinet also included smaller ducted ports on the side front panels in addition to the central port.
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Old 11th September 2013, 05:16 PM   #5
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Humm....a "ported horn" would typically be a front loaded horn with a separately vented rear chamber:

https://www.google.com/search?q=port...w=1536&bih=867

A "bandpass tapped horn" would be much closer to describing this:

https://www.google.com/search?q=port...+horn&tbm=isch
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Old 11th September 2013, 05:40 PM   #6
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Quote:
Originally Posted by turbodawg View Post
A "bandpass tapped horn" would be much closer to describing this:
A "tapped horn" gets larger from throat to mouth, the OP's design seems to maintain a uniform cross section, as such would fall into a "pipe" category.

Whether the OP's design is a BR or a pipe or a TH depends on ratio of duct to enclosed volume and the taper of the duct.

Regardless of what it is called, it is not conceptually new, and can be modeled with Hornresp .
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Old 11th September 2013, 05:45 PM   #7
troystg is offline troystg  United States
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That is this but with the drivers reversed and a larger port slot.

TH221 | Danley Sounds Labs | Danley Sound Labs, Inc.
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Old 11th September 2013, 06:45 PM   #8
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Quote:
Originally Posted by weltersys View Post
A "tapped horn" gets larger from throat to mouth, the OP's design seems to maintain a uniform cross section, as such would fall into a "pipe" category.

Whether the OP's design is a BR or a pipe or a TH depends on ratio of duct to enclosed volume and the taper of the duct.

Regardless of what it is called, it is not conceptually new, and can be modeled with Hornresp .
I called it a tapped tube in post #2.
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Old 11th September 2013, 07:11 PM   #9
troystg is offline troystg  United States
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It is also surprisingly similar to the JBL sb210 although that is more of a flared vented enclosure.
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Old 11th September 2013, 07:45 PM   #10
OMNIFEX is offline OMNIFEX  Jamaica
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Quote:
Originally Posted by mattlong8 View Post
Greetings Bass Lovers,
I've been having a hard time finding any president for a design idea I have. I may just not know what to call it. I can think of several reasons why this design may be problematic but I keep coming back to it for some reason. The design takes a dual opposed slot loaded subwoofer and integrates the slot as the last part of the port.

This is a quick model I made to demonstrate the idea.
Click the image to open in full size.
My thoughts are that this will provide significant low end extension while not taking up a lot of extra room. The port is lengthened lowering Fb or allowing larger port area for the same Fb, reducing turbulence; the front of the woofers are loaded to improve impedance matching and theoretically lowering Fs; cabinet vibrations are reduced by the opposing drivers(which I would have facing each other); and sharing the slot loaded area with the port mitigates the volume increase.

Has anyone tried this? Does it have a common name? Could this a beneficial trade-off when trying to optimize for low extension and space conservation? I'm imagining some strange resonances/standing waves causing big peaks or dips in the response. This is why I threw that little triangle section where the ports meet. I think the geometry of this area could be a critical factor and any insight would be appreciated. I wonder if the long wavelengths will tend to propagate more towards the lower impedance path, so less energy will pass from the port on one side through to the other.

Please bear in mind this model is just to present the concept and is in no way refined...and yes I searched extensively for an existing thread, please pardon me if I missed it. If this hasn't been done, I do not authorize it's use by others for commercial purposes but DIY away

-Matt Long

Yes, I am familiar with that design.

The cabinet uses a combination of a reflex and band pass. Anyone can mimic the design by merely having two reflex cabinets facing each other while having the proper spacing in order for the sound to escape.

EV X-Array Subs follow a similar principal. These have no characteristics of the EAW SB 1000 or the 1001.

Nevertheless, the biggest obstacle will be the amount of pressure build up the cabinet will need to endure for the exit area is very small (based on the photograph) compared to the surface area of the drivers.


As it is a band pass, you will be limited in the upper frequencies due to exit of the port/vent the sound must escape through. They perform okay for an extension to your bass bins if your bass bins can’t offer anything meaningful under 50 Hz, but tend to sound too limited to cover a full bass range on their own.
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Last edited by OMNIFEX; 11th September 2013 at 07:53 PM.
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