I'm trying to figure out what volume to build the closed box. There are a couple parameters that the unibox speadsheet give out though... under standard design, Vb is 105.4 L and under "Design by Vb and Q" the Physical Vb is 130.0 L, and the Vb is 157.5 L. Three different numbers..which one do I use to build the box.
Also, my wanted Qtc is .707. Is that a good Qtc to want.
here is a link to the spreadsheet I am working on:
Click HereThe fields in blue allow change; the fields in red are set. You can change your desired alignment under 'standard design", but that is the only thing you can change. "Design by Vb and Q" allows you to work the program and look at the results in the graphs, etc. Start out working the design by entering the same value as shown under "Standard". You'll see that the two boxes just below Physical Vb are changed when you select the scroll choices in the next column over: "Damping" and "Leakage", which you select according to your desired way of building a box. (Don't select "No leaks", because it will at least be minimal.)
Now start working on changing values under "Physical Vb" and update the graph each time...the changes in Vb will be according to how big your desired net volume of the box will be. Keep in mind that the program is not figuring displacements for the sub, etc.
.707 is considered flat frequency response, so you will see that come up by default. Now since I'm quoting the gurus from time to time as I see fit, without benefit of their permission, lol...I'll reprint a great statement from haemphyst on alignment, or Q. Use what you learn from that, and design your enclosure!
"Generally speaking, the lower the Q a system has, the thinner the bass will sound. A Q of .5 will sound very thin for most people, but it will offer the lowest overall cutoff frequency. It will have a higher F3, but due to the VERY shallow slope of the rolloff, the driver will go deeper in it's overall frequency response. It will have lower power handling, but you will have the absolute smoothest response with a minimum of resonant peaks, both output and impedance.
A Q of .707 is what most people call "max-flat". It will offer good power handling with reasonable rolloff and extension. It will do this also with a decent trade off in resonant peaks. It will usually sound pretty good.
A Q of 1.1 is a maximum power handling enclosure, and will sound like CRAP. Their response is VERY boomy, with many high level peaks in output AND impedance. They will not go very deep at all. It usually happens when an enclosure is too small for the driver."
(quote: haemphyst 11-22-04)
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Thanks stevdart, that cleared a few things up for me.