First Sub Build - Home Theater Forum and Systems -

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post #1 of 5 Old 12-24-07, 12:13 AM
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First Sub Build


I have been surfing this forum for a while now trying to plan out a good sub build. I have built a few main speakers with great results. I use my Vifa two-ways for HT but need a sub for 60Hz and below. My design parameters are, size around 8 cubic feet if possible, $300 or so for driver and box, impressive HT performance. It wont be used for music. I realize low is good and lower is better, but is there and optimum freq target for HT?

I have found a few options on the net and would like to discuss them as they relate to my needs. They are:

CSS SDX15 $300
CSS SD12 $150
Shiva-X $165
Tempest-X $185
Dayton Audio 12" Titanic MkIII $160
Rythmik Audio DS1500 kit $500

It looks like the Tempest maybe out as it doesnt model well in a small enclosure.
But it does seem like a good price.

My initial thought is to go with a sealed enclosure, but it might be more practial for a vented with less power requirments and probably a greater impact on HT.

I like the idea of making my own cabinet and feel pretty confident here. I also like the subs others have listed on the web where I can see the results before experimenting on my own.

Feedback on these drivers or any others I have missed is welcome.



PS: The new 58" Panasonic plasma is on its way
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post #2 of 5 Old 12-24-07, 11:46 AM
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Re: First Sub Build

8 ft^3 net or gross? You state a budget of $300 for driver & cabinet, but then list drivers and kits that exceed your budget? What is your hard limit? What size room? What is the associated equipment? How loud do you typically listen...objective SPL or relative to Reference level is more beneficial than "shake the room"? How much distance from sub to main listening position(s)?

Hoffman's Law...low, loud, small...pick 2.

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post #3 of 5 Old 12-24-07, 12:50 PM
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Re: First Sub Build

Thanks for the reply Brent,

I am hoping for a 2 foot cube for minimal visual impact in the corner upfront by my screen(12 feet from couch). My HT room in 16 X 32 with the HT positioned sideways in a section of the room that is 16 X 16. Carpeted basement.

The second option is to position the sub directly behind the seating. This gives me enough room to approx double the sub size.

I listed the Rythmik Audio kit because it looked like you got a lot for the money. After reading up more on thier site, It looks like it was designed more for musicality than HT. If I can build a sub with a lower priced driver / amp with close to equal HT performance, I can dump this option. At $500 with the amp and driver, I think it might still come close to the $300 driver and cabinete budjet.

The CSS 15" was listed as an option. If there will be that much difference over the 12 and I am convinced the 12" wont cut it then I might need to bump up the budjet to accomodate a better driver.

$300 is not abosolute. Just where i would like to aim. My budjet could double if needed. I am not a true HT junkie- yet.... I would like something that impresses me and my friends for the least amount of $$$. If $300 is unreasonable, then it will flush out here and I can increase the $$.

I dont listen to music very loud in this room. HT will be medium to low most of the time with the kids. Once a week my wife and I like to watch a movie and I suspect we will have it turned up a bit more. When it's the boys time, I will probably want to crank it and FEEL the sound afects/ show off my efforts.

The thing I like about my Vifa mains is that they were built for music and have great imaging. They do very well in HT. Unsuspecting gunshots have scared more than one viewer. I am not sure that I need that type of quality in my bass. It would be nice to have, but as a HT project I think I would want low Fq extension and dB first on my list.


post #4 of 5 Old 12-24-07, 07:42 PM
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Re: First Sub Build

Where to start? As currently described, your potential solutions list is quite long. I'm in NY for Christmas with the in-laws, so this computer doesn't have my WinISD driver library on it. I'll just throw out a few random observations and ideas for the moment.

A 2' cube is 8 ft^3 gross. I'd guesstimate at most 7 ft^3 net depending on wall thickness, bracing, driver displacement, and port volume displaced, if ported.

The CSS SD12 is a very different creature from the SDX15. In addition to surface area, the SDX15 has 33% more Xmax and an XBL motor. Output is a function of displacement...displacement = surface area * Xmax. Based on Ilkka's just published test numbers, his 100 liter (3ish ft^3) sealed SDX15 would probably satisfy me, if I were willing to spend $300 for a driver.

As I mentioned earlier, output is a function of displacement. So, the Tempest-X, also an XBL motor, with similar/same surface area and only 3mm less excursion than the SDX15, should be neck-n-neck for pure SPL output. From memory, however, I think it requires a little more box volume than the SDX15 for the same final system Q. Flip side is it probably doesn't need as much power to reach full excursion. Currently, probably the market leader for value, IMO, if you can handle the cabinet volume requirements.

If your SPL requirements are truly modest enough, a single ported 12" in near field might do it for you. I ran a pair of sealed 12s for years, sitting nearfield, without actually bottoming them or hearing any nasty sounds. However, listening to a friend's SVS 20-39PC+ in a similar sized room from a greater distance let me know my sealed boxes were probably reaching their limits as soundtracks have gotten more and more aggressive with high level low frequencies. The 20-39's driver has much more excursion and is ported compared to my sealed subs that used original NHT1259 drivers of '94 vintage. To use a golden ear term, I would describe the 20-39 as "effortless". Thus, my DVC15 build when the DVC15 went on sale for $105 about 2 years ago.

Another option, although I know nothing about the company. The Torrent Audio Mistral SVC, if it's still available...Torrent currently only lists the DVC. The DVC might be an option, but I haven't modeled it. For $115, this driver is supposed to be a TC Sounds DB500-12, which itself is supposed to be the former SVS Plus db12.2 driver, probably modified enough to satisfy SVS's NDA when SVS went inhouse for production and TCS sold direct DIY for a while. I ran the sims for a dual db500-12 in 7 ft^3 tuned to 20hz in another thread somewhere around here...believe output was roughly equivalent to a single Tempest-X in the same box.

The Dayton RS315-HF models nearly identically to the db500-12, up to its excursion limit of 14mm. Regularly $130ish, but on sale fairly frequently. It's been measured as one of the lowest distortion drivers currently available to the DIYer. Depending on what kind of a time frame you're looking at, I should be able to offer some first hand experience in the next month or so. I've built two identical 3.5 ft^3 net/19-20hz tuned will have an RS315-HF, the other an SVS db12.1 that I picked up from the above mentioned friend when he upgraded to SVS's inhouse built 12.3 driver. Right now, I just need some warm enough weather and a bit of time to complete the final clear coats on the cabinets.

The Rythmik kits receive high marks. In terms of output, it's still all about displacement. With something like the sealed SDX15 already turning in such low distortion measurements using a conventional amp in Ilkka's tests, it would be hard for me to give up the potential output of the higher excursion woofer for the potentially inaudible difference of the Rythmik amp/driver combo.

Bottom line, you could easily go sealed and probably ported with most currently popular 15" drivers in your 2' cube. The Tempest ideally likes a little bigger box. The SDX15 would be perfectly happy starting around 6 ft^3 net, although bigger is still better. A pair of the Dayton RS390-HOs will also work, I think. Not sure how output would compare to the Tempest/SDX since the RS390-HO only has 12mm of Xmax, but it doesn have a low distortion motor as well...usually about $160 each. Then as mentioned, there are a plethora of 12" drivers that will likely work in duals.

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post #5 of 5 Old 12-25-07, 03:06 PM
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Funky Waves
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Re: First Sub Build

For movies I would go with the SDX15 in 8-10cubic feet net tuned to 18-20hz, If you need help with port sizes, lengths, and cabnet sizes contact me and I will help you out. If you can spend a little more you could do an SDX15 with 2 18" passives and be able to go with a little smaller box.

Nathan Funk
Funk Audio
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