Smaller Low-Tuned Sub

asarose247 said:

why not get a REW set-up and get a baseline and some sense of possible solutions . .

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Here is a measurement from one of the secondary seating positions.

I'm with Noah Katz on this one,

You basically have around 5 cubic feet of air space and want to tune a ported sub to match your mega sub tuned to 13.5 Hz? Well, that would require something that can move some serious air in a smallish box and the port will eat up all your space. Passive raditors would be the ticket as they use little to no additional space and use weights to tune them lower. Now to find a 12 inch sub with serious Xmax, a lowish Fs and small Vas to not make too much of a mess.

In my clueless view, I'd suggest the CSS SDX12 subwoofer. 28mm of Xmax, Fs of 21Hz and a Vas of around 2.4 cubic feet should get you close. They also offer passive radiators which can get quite pricey considering they need to be long stroke monsters themselves--don't forget you need two of them, one on each side of the box. If you can, model out using two 15" passive radiators in your WinISD modeling software to see if they would work better. Try tuning the PRs to 13.5, 14 and 15Hz to see which one models the best as a Hz or two difference in tuning is OK as long as you stay within about a 1/4 octave of tuning.

https://www.css-audio.com/online-store/CSS-SDX12-12-XBL^2-Subwoofer-p110031759

You can also get those monsters at Parts Express, they are not cheap, they weigh 47 pounds but you asked! Using something like a SpeakerPower 700 watt plate amp, the SDX12 and two PRs would probably push your total cost to around $1,000 just for the parts. Personally, if I was in the same situation I'd use a PA amp with DSP so I could add a third when/if needed and no worries about purchasing another amp. That's just me, use what works best for you.

Just a thought, an option to model in WinISD as they do have passive radiators incorporated into the software. I use a PR sub myself, had a stout birch 4.1 cubic foot cabinet and made a 12 inch sub tuned to around 20 or 21Hz with a PR. I'll tell you this up front, a few feet of PVC pipe or a few board feet of plywood is much cheaper than a pair of proper PRs to make it work It costs what it costs and sometimes making something smaller is much more costly than making it bigger. Just an option, take a sniff and learn if your nose enjoys the scent. Good luck and keep us posted on your quest.

chucks0 said:

I thought it might be possible to do a small ported sub since JTR has something coming out that is quite small for a 10hz tuning.

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The way I look at this particular kind of situation is not that it's impossible to do small ported subs with low tune, it's just that you still have to work within the physics of ported subs and the fact that their efficiency around tune is largely a function of volume and port size. The major limitation of a small ported sub is that port compression/velocity will become an issue a lot sooner because it doesn't have the volume to support a port with a large cross-sectional area.

However, what you can do is take a very large ported sub and essentially split it up into multiple smaller subs and get the same combined performance, and you can use cheap drivers since it doesn't take much to max out the smaller ports. As an example, you could build multiple 5-6cf subs tuned to 13.5Hz and put a $30 12" JBL in each. Even those cheap drivers will push that sub to 20 m/s port velocity, so I don't see a whole lot of value putting more expensive beefier drivers in a small low-tuned sub, since once you are hitting the limits of the port there isn't much to be gained aside from the mid/high bass where you'll have plenty of output in any case. So it really comes down to whether you are limited to one more small sub or if you can fit multiple. If you can only fit one and you're trying to cram as much performance out of it as possible, I agree with the others on PR being the best (and expensive) option.