So, it appears SVS is using the new subwoofers from Peerless for their top of the line products, which is great:
Here's a link to an off the shelf 15" sub with similar features as the one used in the SVS 16-Ultra series, which come with 8" voice coils:
https://www.madisoundspeakerstore.com/subwoofers/peerless-stw-350f-188pr01-04-15-subwoofer/
While I cannot confirm this as a perfect match across the board, the use of three suspension points (two spiders and a surround), an 8 inch voice coil, and visually similar cone, surround, and frame, I am confident these are from the same designers as the SVS drivers.
So, what do you get? Well, the huge voice coil and added magnet mass increases power handling, motor linearity and Bl linearity. However, the added mass, lower motor strength, and necessity for triple suspension results in a lower sensitivity than most other hi-fi subwoofers designed for deep bass. So, to gain the benefit of high motor linearity, the woofer requires as much as 10x the power as other subwoofers of similar cost, size, and peak output capacity. So, you can use a similar priced subwoofer with a 3 inch voice coil with a max sustained power handing of 300 W to get 117dB at 25Hz, or you can use a subwoofer with an 8 inch voice coil with a max sustained power capacity of 3,000 W to get 115 dB SPL at 25Hz. One could argue the greater motor linearity of the less efficient woofer with a huge voice coil is a benefit, and I cannot dispute that, it is a little scary to me to think that I need 10x the power to get the same output in the room as the smaller voice coil subwoofer.
Another advantage of the huge voice coil sub, which I am certain SVS is counting on, is the fact it doesn't require as huge an enclosure to get an ideal performance for the most critical operating range - which for HT use is between 30Hz and 60Hz. Being a super-nerd, I tend to want the best performance at 20Hz and lower which then assumes very good performance in the 30Hz to 60Hz range, but that's my nerdy character. Most users don't really appreciate stunning performance below 25Hz as most users have listening rooms which resonate like a drunken bastard below 40Hz anyway. So a tighter, cleaner, smoother subwoofer in the "subsonic" frequency range is useless to a good 90% of customers for aftermarket subs like this. Hell, I've recently discovered that many serious and well-intentioned "audiophiles" with some of the best gear on Earth tune their subwoofers on their "reference systems" 10dB to 25dB too loud. They energize their noisy, lively, resonant rooms to much in the bass, they cannot turn their systems up enough to appreciate the other 9 octaves of sound properly. It is sad.
So, if SVS is using these very good Peerless made drivers, I openly admit they are very good. However, I could argue they are sacrificing perfection across the entire range for improvements in box size and detriment in the super low subsonic bass and making those insanely huge 1,500 W amps absolutely necessary - which is fraught with their own risks (how many AC circuits do you need if you have a 7 channel Monolith amp and a couple SVS 16-Ultra subwoofers???).
So, it is all a game of "what works best for you" that makes this discussion incredibly complex.
