Am I using UniBox correctly?

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I downloaded a copy of UniBox a while back but haven't used it in some time (and I was not very good with it in the first place). I've been using WinISD for a "best case" scenario to see where things might lead. But, I've been wondering about the effects of the inductance of the driver and box stuffing. So, I dug up the copy of UniBox.

I am looking at upgrading subs to an Ascendant Audio Avalanche 18, because I really like the appeal of the 18, mostly. I've been wanting an 18 for some time now. The only problem is that I don't have the room for a huge box to put it in. The minimum recommended enclosure (this is without using an EQ or LT) is 4.6 cubic feet, which is just way too big, I think. I am looking for something more along the lines of 2.5-3.5 cubic feet or so. I know this is small for an 18, but it is a must to satisfy my "need" for an 18" driver without losing a lot of space.

I've done a little modeling in UniBox and it seems like all could work out well. As a test, I used 80l for the box size. I ended up with a system Q of over 1, which is not a good thing. I will be using this mostly for music and some HT, but never really loud. I've heard bad things about boomyness with high Q's, though, and I don't want any of that. So, I tried selecting the heavy fill option, which brought the Q down to .84, which is about where Chad Kuypers (of Ascendant Audio) said he runs his two Avalanche 18's that are in his home theater. But, I wonder, what exactly does this "heavy fill" setting mean? How much fill is heavy?

I am trying to achieve as low a Q as possible while keeping the box small and not requiring any EQ, as I do not have all the funds yet to include all this. I am a very poor carpenter, so I am having to have a box built for this sub in addition to buying the driver.

Are there any tutorials for using UniBox? What kind of values should I use for absorption and leakage? Any help is much appreciated. :)
I have written a program similar to Unibox

For design purposes I use:
Ql=15 for standard vented boxes

Qa=Ql=20 for lined sealed boxes
Qa=Ql=10 for lined stuffed boxes

Once it is built, you can measure the impedance curve and vary Qa, Ql and Qp until they match your measurements to see what you have got. It is typically not as critical as you might think. A Q up to 1 will sound fine especially if you like pop music. People who like lower Q's just like big boxes.
Thank you for the information. :)

I have a wide variety of tastes... I like deep impacts for movies; effortless, smooth bass for classical; and articulate bass for rock (mostly Van Halen). Its hard to get all of that out of one sub...

I will try some modeling with this woofer. Strangely, with UniBox, my old woofer (Blueprint 1503) looks pretty good...
I tend to find that a Q of 1 can actually be quite tuneful. The Monitor Audio MD852 speaker of the late 80's early 90's used that loading, and it was desigend by someone who was no fool, and that is Robin Marshall. I do know this: Everyone who worked at a certain local store and had the opportunity to buy any speaker in the store, for their personal use..ended up taking home that MD852, and that is a sealed box with a Q of 1.

Low mass cones, and low mass moving structures.. go for high Q boxes to control the driver. The air bcomes the dominant factor and also.. if the driver is going to be crossed over with a low slope crossover..and it is 18 inches in size, box resonance issues will very slightly rear their head. Driver positioning may end up being critical.

Also, look at possibly aperiodic loading of that smaller box. That may solve the issue, and still deliver clean enough bass.
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