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Help me design a new pair of subwoofers.

post #1 of 50
Thread Starter 
Here's the current status of my home theater system, please forgive it's simplicity.

Panasonic TC-P65S2
Onkyo TX-NR708
PS3
Xbox 360
Local Cable Provider HD Cable Box
Center Channel: Yamaha NS-C444
FL/FR: Yamaha NS-777
Rear Surrounds: (4) NS-333
Subwoofer: (1) Velodyne Impact 12

I'm looking to hopefully build a pair of subwoofers to stage within the setup, eventually I'd also like to build another two subwoofers to increase the total in the room to 4. I'd prefer equipment that would keep the setup minimal, and reduce the amount of tuning that is needed since I'm not the only person that uses the room. I would like to keep the size of the subwoofer around 15"-18" and a price point that's somewhat affordable or at least allows me to purchase portions of the equipment in stages, till I can complete the build.

I also use the system for 7.1 at the moment, I'd like to add a set of subwoofers that can provide the "visceral" lows of the theater.

The main problem that I'm running into is finding a driver that I like, under the $500 dollar mark. Seems everything I've looked at, and seen in builds are well into the $650-$750 pricerange. I was looking at the Sundown Audio SA-15's, but I'm curious to see them in a build.

Your suggestions are greatly appreciated.
Edited by Big-Sexy907 - 6/14/12 at 2:54am
post #2 of 50
What's the room size, and what are your goals for SPL and low frequency extension? By 15-18" do you mean the outside dimensions of the enclosure be no more then an 18" cube?
post #3 of 50
Thread Starter 
Sorry, I should have included the room dimensions with my original thread.

Room is roughly 20x24.

And the 15"-18" was meant for driver size. Enclosure size doesn't really concern me.

Ideally I'd like to have the subs extend to 20hz and lower if possible.

I think I found a set of subs that I'd like to use.

http://obsidiancaraudio.com/index.php?id=6

Perhaps four of these sealed would do quite nicely, now which version should I purchase, the D4 or D2?
Edited by Big-Sexy907 - 6/14/12 at 12:51am
post #4 of 50
You're not going to get much room gain in a room your size, so you would need to apply boost to the low end of any of those sealed, though the 18 is still good to 30hz. The obsidian 15 looks pretty good for a decent sized vented box, venting the 18 isn't really an option. I'm not sure what you're considering for power, as you said minimal equipment in a common room. I'm still a fan of plate amps until you get past needing 500 watts, and you will have to deal with fans using pro amps. Here's the 15 in an 8ft3 20hz box vs the 18 in an 8ft3 sealed, both with 600 watts.

347
post #5 of 50
Thread Starter 
Jay, Thanks for the quick modelling. I'm not really limiting myself to just a sealed enclosure at the moment. I'm stricken with the perpetual problem of enclosure size vs. how much space I'd like to enclosure to take up. Realistically, I am comforatble with reducing the number of drivers to two, in vented enclosures... The possibility of using a 500w plate amp is also reasonable.

BTW, I see that you have AK as your location. Where abouts are you located? I'm in Palmer.
post #6 of 50
There are lots of ways to go about it. I find that lots of clean output in the upper range is important to get the chest compression effect. A pair of of Eminence Sigma Pro 18s in 12 cu. feet powered by a 500w plate amp (in parallel = 4 ohm) should get 128dB to 40hz (or be tuned lower and larger to get to 30, which would likely achieve a similar, albeit louder, effect to what you'd find in a public cinema). Then a separate enclosure (or IB? only if you can cut holes in the wall biggrin.gif) could be added later to handle the bottom octave. Just an idea.

With twice the enclosure (15hz tune) size and same amp power, a pair of Dayton 15s (about same price) should get 116dB f3 of 14.5hz. Keep in mind that using the 18s in that same enclosure would get around the same max output at 15hz (likely higher distortion, maybe not important, dunno), but it would be back up to 128dB at higher freqs, which could be compensated for with dynamic EQ that drops off as levels pass 116dB to maintain linearity. This means that both would be about the same at normal lower levels, but you'd get 20x the acoustic output from the pro drivers when nudged to the limits. Just more ideas wink.gif

Some might nudge you to horns tongue.gif.

E: By the way, the (dynamic EQ) DEQ2496 from Behringer would have all of the functionality needed for subwoofer integration without too much tuning required (depending on individual smile.gif )
Edited by arande2 - 6/14/12 at 3:28am
post #7 of 50
Thread Starter 
Arande2, Thanks for the reply. I'm really thinking I want to try out these obsidian drivers, and the price is just cheap enough that I think two of these ported may be worth a shot. (Jay would you mind plotting the 18" in a vented enclosure?) And hopefully if I like them enough I could add two more at the back of the room to to give a little extra oomph. As I stated before I'm really at the limit of making a giant enclosure to accomidate the sub. However some redesign of the room could be made to give the space needed for additional enclosure size. (I'll have to measure this out when I get home). I'm not completely against using a proamp, but the simplicity of a plate amp configured into the enclosure does have it's appeal.

Oh, and I'll be utilizing the Onkyo's Audyssey feature to tune the system to avoid complex components so the little lady won't feel so overwhelmed when using it.
post #8 of 50
Hey, cool! I'm down here at JBER. This woofer doesn't like a vented box because of its high Qts, you can see the hump around 40hz.. The blue line is 20ft3 14hz, basically an EBS alignment, and it still has a minor hump.

318
post #9 of 50
it doesn't work. the motor is too weak.
post #10 of 50
Thread Starter 
Damn, and I had my heart set on getting a set of 18's. 15's here I come. Any reccomendations on a plate amp? I seen that there were some at Parts Express that were fairly affordable manufactured by Yung. Now my question is, should I purchase the amps with a 6db boost at 25hz or not?

Amps can be seen here,

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=301-514
post #11 of 50
The boosted amps are basically for sealed box subs, though you could design a ported sub that makes use of the boost.
post #12 of 50
One more thing to consider with you living in AK is shipping. When I was trying to plan out my build I kept getting hit with the prospect of paying $90 shipping for a 15" woofer, which basically increased the drivers cost by 50%. I decided to go with something available on Amazon, they have a pretty decent selection of "car" subs that will ship free to your house. For example, here's a model of the driver I purchased compared to the obsidian, both with 500 watts in 8ft3 20hz
(green is obsidian)
291

This woofers specs make it very versatile, it works well in small sealed, and small or large ported boxes. My model also matched my measured response pretty closely.

http://www.amazon.com/Power-Acoustik-15-Inch-Competition-Subwoofer/dp/B001QWYP3Y/ref=sr_1_1?ie=UTF8&qid=1339719412&sr=8-1&keywords=mofo+152x

(the ring around the outside comes off, I also plan on painting the heat sink black when I rebuild my subs)
post #13 of 50
Thread Starter 
Jay, those don't look half bad! Other than the blue mess around them. Maybe this will reduce the costs a little more so I can afford some other items for the house?
post #14 of 50
There's always the option to down fire the drivers as well. I like these drivers, they perform well, sound good, and are well built. For $160 they arent the greatest deal for most people, but when you you have to deal with shipping these are definitely a good deal.
post #15 of 50
Thread Starter 
That's an understatement, shipping costs have killed potential purchases for me before. LOL
Think these can potentially take 1k watts from a Dayton plate amp?
Edited by Big-Sexy907 - 6/16/12 at 4:56am
post #16 of 50
Thread Starter 
Double Post.
post #17 of 50
Supposedly those "1000 watt" amps only put out 580 watts

http://www.avsforum.com/t/855865/measuring-amplifiers/570#post_13714349

Not sure if they could actually put out the claimed 950 watts or not, but if you use one it might as well be set up for it. The Mofo can handle it depending on the enclosure setup. 5 ft3 tuned to 23hz will take 950 watts at just a hair under xmax.

265
post #18 of 50
Thread Starter 
Thanks for the tip Jay, I went ahead and ordered two of the Mojo's today.

Now it's time to go plate amp shopping....
post #19 of 50
Nice! Let me know if/when you need any help with the box design.
post #20 of 50
Thread Starter 
Jay, If anything I could save the box design and build it at a later date. I'm actually supposed to be starting construction on a shop behind our house in a couple weeks, Hopefully after that I'll be able to start construction on the enclosures.

I was thinking about a vented enclosure, tuned low of course. Amplification will be dependant on what I can find at a reasonable price, but anywhere from 500-1k watts.
post #21 of 50
An EP4000 with a miniDSP would be a good choice if you move past a plate amp

http://www.amazon.com/Behringer-EP4000-Professional-Accelerated-Technology/dp/B001U5JFNM/ref=sr_1_1?s=musical-instruments&ie=UTF8&qid=1339778113&sr=1-1&keywords=ep4000

http://www.minidsp.com/onlinestore/detail/15-minidsp-in-a-box/flypage/62-minidsp-2x4-reva?sef=hcfp

The EP4000 does 650 wpc, the mini dsp lets you set a high pass filter, and eq the room response flat. A 6.5ft3 box would be good for handling 650 watts. You could tune to 20hz for flat, or tune to 17hz for a slight roll off. A pair of 4" x 33" ports for 17hz, or a pair of 4" x 23" ports for 20hz.. You could even do a slot port, 2" x 14" x 24.5" for 20hz, or 2" x 14" x 35.5" for 17hz. You just have to set a high pass filter with the DSP.

326

(16hz 4th order HPF green, 20hz 2nd order HPF orange)
post #22 of 50
Quote:
Originally Posted by arande2 View Post

Some might nudge you to horns tongue.gif

Nudge, nudge. There are a couple people using two of my signature as risers, and will give you plenty of SPL without needing a lot of power wink.gif

The drivers are going up in price soon, though.
post #23 of 50
Thread Starter 
Wolf, thanks for the reply. I've already purchased a set of drivers, now I just need to work on cabinets for them.

Jay has it almost right on the money, I was considering the ep4000 with the mini dsp. I've been looking at them while at work. Seems like a doable combo.

Jay, you wouldbt happen to be able to build a box diagram/cut list for me could you? I'm digging the idea of the slot port.

BTW, I just picked up the minidsp.
Edited by Big-Sexy907 - 6/15/12 at 9:24pm
post #24 of 50
I'm really not very good at sketch up, and I've never used cutlist, so that part isn't up my alley. I could give you some specifics. A 23" wide x 24" high x 28" deep box built out of .75" material, with a 2" x 14" x 24.5" slot port will have an internal volume of 6.83 ft3. So for each sub you would need a pair of 23"x24" panels for the front/back, a pair of 22.5" x 26.5" panels for the sides, and a pair of 24" 26.5" panels for the top/bottom. For the slot you would need a 15.5" x 23.75" panel and a pair of 2" x 23.75" strips, cut a 2" x 14" opening directly above where the bottom panel attaches to the front panel dead center, and attach the port to the front/bottom. For bracing cut a pair of 22.5" x 21.5" panels, notch out the 2.75" x 15.5" sections in the bottom center of each panel to sit on the slot port, an inch above that cut out two 9" x 16" sections leaving 1" down the middle of the brace, these are each placed right around 9.5" from the front and back of the cabinet. Cut four 2.5" x 26.5" strips, and attach them front to back in an X or + pattern around the driver cut out. This puts you at 6.55 ft3, and the woofer will take a bit of volume.
post #25 of 50
Thread Starter 
Jay, thanks for the help. I just thought you might have a enclosure designer.

I'll take a peek at RE Audio's website, they had an excellent calculator IIRC.
post #26 of 50
Ah, gotcha. I use this for all my enclosure calculations

http://www.hometheatershack.com/forums/enclosure-volume-calculator/
post #27 of 50
Thread Starter 
I have a question using the MiniDSP. According to this article features of the DSP allow for EQ adjustments on top of crossover setpoints to be changed. Since I'm planning on using the Onkyo's Audyssey feature to EQ and set the crossover points for the system, should I go into setting up EQ'ing for the subwoofer using the DSP, or should I set the crossover points and leave the EQ'ing to the Onkyo?

All of the remaining speakers in the system will be driven off the Onkyo's power, no other external amps will be used.

http://www.hifizine.com/2010/09/subwoofer-equalization-and-integration-with-the-minidsp-2x4/
post #28 of 50
You're going to have to wait and see what the results from auydyssey are first.
post #29 of 50
Thread Starter 
Gotcha, so setup the DSP as a crossover and set the HP filter then see where Audyssey gets me.
post #30 of 50
Yup, just be careful with what audyssey does, many people report it boosts output below tune by crazy amounts.
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