Originally Posted by genaccmiller
1. Do I even need a second sub given the room dimensions?
2. If I did need a second sub would I need one or two? I already have one sub in the front. Would adding another two for a small room be an overkill?
3. Given my room size would I go for mini Marty or cube or something different? The first page of this FAQ says For a small room under 1500cuft a pair of the micro and cube are potent. I already have a Klipsch. So does this mean I will need two micros?
4. I don't see a lot of difference from a cost perspective comparing this to a ready made sub. I was looking at the gsg website. Am I misreading anything?
5. There also seems to be a VBSS. What's the difference between that and Marty?
On top of Gary's solid input above, I'll pitch in my thoughts as well:
1.) Multiple subs will always help out. When you start getting down under 30Hz frequency wise, your room nodes will kick in. You'll find with REW that in nearly every case, you won't be able to get ideal bass response out of a single source. If so, it would only be for a single seat. When frequencies get under 30Hz, think of a sound wave as an old massive jump rope that two people swing. The subwoofer has one handle... and then any given wall has the other handle. As frequencies change, the length of that rope changes. There will be certain lengths that cause the rope to swing 'nicely' as a standing wave and will cause inconsistent response throughout the area. Bit of an odd comparison, but hopefully it helps a bit. Bottom line - Yup! Multiple subwoofers primary advantage is to help get better frequency response throughout the room, not necessarily boost output.
2.) You can always turn down your subs, so I wouldn't worry about 'overkill'. Depending on what you end up with, you may find that it's more work than it's worth to integrate your original sub, however. I'd personally just plan on building two, as it's easier to make them in pairs. You can always try to dial the room in with all three and compare the result to only using the two DIY subs. If the two new DIY ones are okay in the room, you can sell your current sub or move it to another setup.
3.) Your call on the sub size. Even in a smaller room, as far as ported subs go, the bigger the box the 'better' if you can fit them and position them ideally. I'd recommend cubes based off the dimensions unless you really need the micros smaller size. The mini's will have a good bit more output, but they are a decent step up dimension wise. I think you'll be very happy to start with a pair of any martys. You can always add on one or two more down the road easily.
4.) You won't find too many direct comparisons at first glance. The performance of any 18" DIY sub is going to be substantially better than most of your commercial subs, but the cost will come out a bit higher in the end depending on what you go with. I think I spent ~$300 on my SVS12, but I spent a good bit more on a pair of full marty's (~$450 each when you split the cost of the amp?)... The problem with that comparison is that the performance of the two are not comparable... may as well be dividing by zero. There are much better commercial offerings out there then I had, but you'll always be paying more for a given performance level with commercial offerings in the end. The problem with the apples to apples cost comparisons is that most DIY designs here target very high performance.
5.) The VBSS is a smaller ported sub that uses a pro-audio style woofer. It's much more efficient for sound above 30Hz or so, but it doesn't have the response of the marty subs under 30Hz. I plan on adding a pair of them to my pair of full marties just for some extra higher frequency output, for what it's worth. They seem to be great subs for most music given the frequency response and doesn't require a real strong amp. Some people are building enough of them to get fairly solid output below 30Hz, so YMMV.
Good luck! You won't look back after you go DIY.