It’s a tough call. I love listening to music but movies are the driving force behind this upgrade. I want to have my cake and eat it too. This is a lot like computer monitor shopping. Higher resolutions are great for general usage but lower resolutions give better framerates in 3D heavy applications and games.
12" vs 15" Depends on the Sub. Too many variables to make a judgment.
A 12" with a 200w amp vs 15" with a1500w amp?
A 15" needs to move move a much shorter distance to produce the same SPL. So which is “quicker”?
A sealed Sub often sounds tighter than a vented Sub, but again it depends on the design.
Take a look at the Arendal 1723 subs. The group delay for the vented subs is less than most other brands sealed designs. PDQ.
As far as music goes, the lowest string on a bass guitar is 42Hz. Organ and big grands reach lower.
Movies plumb the depths.
All the Best,
Jeff
My sub? Just took my 24" Hartley in a 68CuFt transmission line apart because of a move.
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24" sub? That must be epic! 
Is there a typically-listed spec I should be looking at to see which subs are quicker? I guess knowing size, wattage, and enclosure type only gets you so far.
Edge of Tomorrow is a great movie! I hear Blade Runner 2049 has some crazy low-end too.
Seems like it isn’t practical to buy a subwoofer rated for 10hz. I guess you go as low as you can and hope that in-room performance gets you the rest of the way?
Btw have you seen Annihilation (2018)? I was ultimately disappointed in the plot but sonically that movie was CRAZY. Unforgettable theater experience
Unfortunately most manufacturers don’t give meaningful data on their subs.
Even frequency response is often bogus.
Sure a sub may reach 20Hz, but if it only produces 90dbl at 20Hz it won’t be felt (much).
For example here is the actual responce of a 12" Klipsch
vs an SVS 2000 pro
Guess which one I’d rather have? 
A thing to keep in mind is that a sub (or AVR) with PEQ can filter (or gain down) peaks in the freq response caused by room nodes. But nulls can’t be filled in by boosting those freqs.
If your source AVR doesn’t have bass management, having PEQ built into the sub - like the SVS - is important.
The 2000 series, for example, has 3 EQ filters and a phone app to control it.
I suggest hanging out in the subwoofer section at the AVS forum I mentioned above and the
Great reviews there. Both have articles that give all sorts of info on choosing and installing subs.
All the Best,
Jeff
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Fantastic resources and replies, thanks Jeff!
Sounds like I would definitely benefit from a sub like the SVS with EQ options. Whether or not I upgrade my current budget amp, I plan to keep that part of my system fairly “stupid.” I don’t want to switch to an AV receiver until I have room for surround sound. I think most of those products emphasize features over actual sound quality and power.
Using the REW software you can send any freq you like to your receiver.
Lots of fun to see what the speakers can really do.
No matter what you get in a quality brand - it will make you smile every time the dino stomps…
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Does your amp have a subwoofer line level output?
The SVS doesn’t have speaker level inputs.
All the Best,
Jeff
Here is another link for you. Great sub discussion . Mthomas is very knowledgeable and loves helping people.
The sub thing can be as complicated or as simple as you want it to be. True optimization can be quite involved. But, really adding a sub and putting in in a corner, setting crossovers and levels, will usually make things “better” for most listeners. What receiver are you using? Many produced over the last several years have some kind of room correction. They will help with integrating the sub.
He has a real good primer that will help you get started.
As you like watching movies with your system, I really can’t see how adding a sub and doing minimal configuration will not help you to enhance the experience.
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Thanks I’ll check that link out too. Looks like I’ll be signing up to some new forums when I get home today.
I have an SMSL AD18 which is a D-class dac-amp combo. I believe it maxes out at around 50 watts per channel at 8 ohms and my speakers are rated for 20-100 watts. Technically it has a subwoofer out, but it is really just a crude line-out with no cross-over or controls whatsoever.
I know there are several possibilities for how to integrate a subwoofer in terms of wiring/connections. None of the options open to me are strictly ideal (there’s no spot in-between my amp and preamp because they are a single unit) But in the short term I think a sub would make the biggest immediate difference and I could then upgrade the other parts later on.
I also found this gizmo which might allow for more flexibility with different types of amps other than SVS
That makes it a little bit more difficult, as there is no high pass filter for your main speakers. And (it sounds like) not a true LFE (Low Frequency Effects) channel output. But it does allow a single wire connection to the sub.
Is the output on the SMSL labelled as SUB OUT? if so there may be some crossover filtering built in.
(EDIT: I checked. You are correct, the jack is just a full range out)
Also, any decent sub will have built in crossover settings and certainly level control… for the sub. So you can do at least basic blending.
Try before you buy is the answer. It is just that shipping on most Subs is expensive. It would be great if you could find a shop locally that would work with you on that.
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It’s a funny thing about all these statistics and measurements ---- If the music doesn’t go below a certain Hz as stated above — Put a high pass filter at 10-35hz, see if you loose any sound or realism in the sound
Transmission Line Bass is a great setup ( love em ) If you have the room
Speaking of LFE channel output, does it need to be explicitly supported by a receiver in order to make it past the processing stage to the analog stage? Currently all of my audio runs into my x900f TV via HDMI and then passes out to my dac/amp via an optical digital connection.
I think it might be possible to utilize a sub like the SVS as a high-pass filter for the speakers if it was after a pre-amplifier. Is that correct?
Unfortunately there isn’t much for audio around here. Everything around leans towards audio production rather than consumption.
Yes, but some will argue that there are harmonics and some instruments, like synthesizers and pipe organs, that do go as low as single hertz. In any case, the LFE, used for explosions, gunshots, thunder, etc, do go well below the 35 Hz that you mention. Now finding a sub with decent output that low is a different story. They tend to be big and expensive. And, of course, getting them to do that in your room is where the optimization comes in.
This is the one you need
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lol that looks ridiculous but I’d love to hear one haha
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Room, Room , Room Most important aspect in the equation
Bass is a funny thing ( Big Waves) sometimes you sit in one place, there’s hardly any – move over, back, forward, there’s too much
We go see lots of live music, most of the time I like the back wall the best