[Moonfly]

Based on your criteria, I find it hard not to recommend the drivers I'm using.

http://aespeakers.com/shop/catalog/product_info.php?products_id=68

They are incredibly articulate, and Ive experienced a pair of these running in a very decent setup. They are incredibly clean, match your spl criteria no problem, and I havent heard anything as clean (although my experience obviously cant include everything). They will come well within budget and the only area they might push your limits its size, but not by much. They work well in a 75-125 litre enclosure with QTC ranging from .707 to .6 respectively, although you may wish to employ a filter for the larger box sizes to help protect the bottom end excursion. As a side note, there were no apparent issues with the ones I heard in 125 litre enclosures so me personally, I wouldn't be overly concerned and especially at the levels you wish to run at.

 

[Moonfly]

Thank you!
Do you know what the practical difference between the AV15-X and the AV15-H is?
Given my limited cabinet size and lack of concern over extreme low extension or SPL, do you think a 12" might work better?

I don't understand most of the specs, but is there a way to tell if the same motor structure is used for both the 12" and the 15" versions? The AV12-X weighs in at 36lb and the AV15-X weighs in at 37lb so I'm guessing they might have identical motors and the 1 lb difference is in the extra frame and cone for the 15" unit. They also both have the same stroke - Xmax = 23mm. The magnet structure doesn't look different in the photos, but it wouldn't be unusual for them to use the same photo for both products.

Anyone else - other suggestions? Or is this a clear choice for the AV?

From what I gather, the H is designed to be tuned a little lower to gain more depth, while the X is tuned a little higher to get more pronounced upper bass, so I reckon the X variant would suit your requirements better. I think your hypothesis on the 12" model is probably correct, although it will really take a confirmation e-mail from them to confirm that one. I dont see an issue with you using the 12" if thats what suits your desires better.

The larger drivers will have a little more of an air of effortlessness about them, and obviously will go a little deeper with a little more ease, but otherwise I'd be hard pushed to point out any major differences based on specs.

You seem to have a good handle on things and I would follow your instinct a little, but it is worth noting I think the 15" would be the better option for a sealed design. As has been pointed out, the shiva is a very popular driver so if your looking at 12" drivers its certainly worth a look.

It may also be worth browsing the diy build database to get some ideas. CSS also sell sub kits that are popular. Take a look at their 12" sealed designs, I believe they have a promotional discount running at the minute as well. Here is a pr design, if your going to build a 12" sealed though, you might find yourself being more volume limited than you really want to be. That said, if you dont go crazy anyway you'll be fine. I used to own a Rel Q series sub, it was a sealed 12" design, and the SQ musically was very good indeed.