To simplify matters somewhat, I used equations found at:
http://www.diysubwoofers.org/
Please be aware that you really need to add a First or Second Order Passive Crossover (which would make this into a 5th or 6th Order Bandpass box); or, you will have to have a separate power amplifier that has an active crossover for this cabinet that restricts the frequency response accordingly (4th Order Bandpass cabinets have very uneven frequency response at frequencies above the Sub-Bass range (200 Hz or more) - you will need to manage this with either a Passive or Active Crossover network).
See: First Order Crossover Networks and Second Order Crossover Networks for information about adding one to this box.
Also see Additional information about this application and its use.
Please fill in the following Information.
Construction Data Diameter: Speaker Diameter in Inches Bracing: Inches mm (Optional) Thickness: Inches mm of cabinet material Speaker (Driver) Data Qts: Fs: (Hz) Vas: Cubic Feet Liters Cabinet Parameters S: 0.4 0.5 0.6 0.7 Response Curve F3: 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 80.0 Hz - Low Freq Roll-off Port Diameter: Inches mm (Optional)
Optional: If you have a specific Port material that you want to use, and you know the inside diameter in inches (ie. 1 3/4 inches = 1.75), or in mm, you may enter this value manually. Select the right scale to use. This value must be entered as a decimal value (the program does not understand fractions).
This software generates results for a single speaker. You may consider adding a second speaker to your system, if you do, all parameters stay the same, except Vas. Assuming identical drivers:
You can define the Diameter parameter as the the size of both the drivers put together - ie. 2 6 inch speakers = 12 inch Diameter. Make this correction to the Diameter parameter you enter before calculating your results.
Also be aware that the published specifications of your Speaker is based on a sampling of the production run. Large variations may exist in any 2 speakers produced by the same manufacturer with the same model number. This is not as big an issue as it could be. The relationships of the major parameters tend to be quite consistent and while it could impact your design, it may not be significant. If in doubt, there are systems that can be used to individually measure speaker parameters available from Parts Express and LinearX (and others) using a Windows based PC.
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