First DIY sub... ideas? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 9 Old 05-29-2008, 06:16 PM - Thread Starter
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I've been kicking around the idea of a DIY sub for a while and looking around for good deals. What I've found is the 13Kv.2 D4 on sale over at elemental designs. I'm curious what kind of setup one could make using one or more of these drivers and one of the following amps (these are the ones I've found used for cheap):

QSC MX1500
Behringer EP2500 (about $50 more than the QSC)


I tried messing around with Unibox but all it does is blow up when I try to use it on my iMac using Excel 2004... I'm trying to put something together that would best my SVS PB12-ISD/2 which I'm getting about 105 dB out of before the distortion makes cranking it up anymore unbearable.

I'm open to any ideas although as I have basically no woodworking experience a sealed design would probably be best.

Any help would be greatly appreciated!


The tech specs for the eD are:

Qts: .31
Qes: .35
Qms: 3.33
Fs: 21.5 Hz
Re: 3.7
Vas: 162 L
Mms: 142 g
Bl: 15 T*m
SPL: 88.47 dB
Sd: 545 cm^2
Xmax: 15.1 mm
Voice Coil: 50 mm

Magnet Width: 5.700"
Cutout Diameter: 11.000"
Mounting Depth: 5.750"
Weight: 14 lb
Total Height: 6.250"
Displacement: .06 ft^3
Outside Diameter: 12.375"
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post #2 of 9 Old 05-29-2008, 07:51 PM
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Add another $150 for a Behringer feedback destroyer parametric EQ unit if you go sealed. Also decide sealed or vented based on the driver - this one looks like it would work better ported due to a low qts.

Unibox isn't working, have you tried WinISD? Any access to a PC? Macs are cool, but my close friends dual boot Vista for this kind of stuff :-/

Speakerworkshop is another free one that I like a lot. Any of these should tell you what cabinet is best for a given driver, ported, sealed, bandpass, etc.

If you're looking to best your SVS you may want to either get a pair of those or different drivers. I'm not going to do a plot for you, nor do I know what your SVS can do, but I'd carefully compare the predicted results versus what you got. With this single 12 it might be the same tool in a different hand if you get my drift...
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post #3 of 9 Old 05-30-2008, 07:55 AM - Thread Starter
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Thanks for the input! Unfortunately I have a G5 iMac so no dual boot... but I got my wife's laptop out and have been playing around with Unibox on that. I have a couple (stupid) questions though.

1. Do I need the Le, Le2, and Re2 values? They are not listed on the eD site.
2. The driver I'm looking at states Dual-4 voice coil, is that Dual-4 Ohm? If so does that mean that one of these drivers with the two voice coils wired in sequence will result in an 8 Ohm load? Looking at this page at eD the last image shows 4 drivers wired in parallel with each driver's 2 voice coils wired in series resulting in a 2 Ohm load but how do you compute the watts each driver will receive?

I'm trying to figure out what value to enter for Nominal Power and am curious if I could drive 2 or even 4 of these with the EP2500 (and what Nominal Power I'd end up with if using 2 or 4 of these).


I know these are basic questions but it's been a long time since I've done any of the math with Ohms law and the like (since 10th grade)!
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post #4 of 9 Old 05-30-2008, 08:16 AM
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In a ported this driver looks good in a 6-7cu ft box,17Hz tune. I would use a 4 in port with heavy flaring,ideal would be a 6inch port but it would have to be long...

With ~300W input you are good,and in room extension should be below 15Hz.

With a 4 Inch port I would even tune lower,~15-16Hz tune.

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #5 of 9 Old 05-30-2008, 08:59 AM
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With the EP2500 you can drive 4 of the 13KV2 d4's with about 375 watts each (4ohms per channel). If you go with two 13KV2 d4's you'll have about 500 watts on each of them (8ohms per channel).
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post #6 of 9 Old 05-30-2008, 09:30 AM - Thread Starter
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Quote:
Originally Posted by TheEAR View Post

In a ported this driver looks good in a 6-7cu ft box,17Hz tune. I would use a 4 in port with heavy flaring,ideal would be a 6inch port but it would have to be long...

With ~300W input you are good,and in room extension should be below 15Hz.

With a 4 Inch port I would even tune lower,~15-16Hz tune.


I think I'm entering something wrong... when I put in these parameters (17 hz tune, 4" port, 170L box) the FR graph looks good but it looks like I'll be exceeding xmax between 22Hz and 32 Hz (17mm at ~24Hz). Also the port speed peaks up to 48m/s at about 16 Hz - would that be audible chuffing?

I'm thinking either I'm doing something wrong or the xmax being exceed and the air speed are acceptable.
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post #7 of 9 Old 05-30-2008, 09:41 AM - Thread Starter
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Quote:
Originally Posted by evilbeaver View Post

With the EP2500 you can drive 4 of the 13KV2 d4's with about 375 watts each (4ohms per channel). If you go with two 13KV2 d4's you'll have about 500 watts on each of them (8ohms per channel).

Looks like the EP2500 may be too much power for these guys... plugging 375 watts into Unibox I'm way over XMax at 24Hz.

I'm thinking about doing two boxes with two drivers in each. If the EP2500 works out I can get one for about $250 + $200 for the drivers + $? for building supplies should crush my SVS. I have no idea what to factor in for building supplies though, also I don't know what I'd need (if anything) for driver protection. It may be a tough sell with the wife though...
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post #8 of 9 Old 05-30-2008, 09:46 AM
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Nope, you are entering it correctly, unfortunately a 4" port is pretty useless for most 12" subs, you need a lot more port area than that, I'd prolly do a pair of 4" ports 30" long in this situation. You do go a hair over xmax, but in a typical subwoofer system, there will be big losses, you probably won't even hit xmax with 300watts even below tuning. Theres all kinds of options here, but ultimately, it depends what box size you can do and what your budget is.
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post #9 of 9 Old 05-30-2008, 01:07 PM - Thread Starter
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As far as box size I have a spot in my room that isn't useful for much of anything besides an end table or subwoofer. It's 27" x 32" (that would put it right up against the wall) and I could go up to 60" tall if I had to.

I was trying to get my budget under the $500 I think I could get for my SVS but if I go with those 4 drivers with an EP2500 there's no way I can make that. However, it seems like a waste to buy a cheaper amp that will only put out 1/4 the output of the EP2500 just to save $50-$100 and it also seems like a waste to buy the EP2500 and only use one of the two channels. I guess what I'm thinking is the EP2500 with 4 of these seems like the logical combination - going with a smaller amp and fewer drivers will only save a little but I can put in that little bit more and double my subwooferage! What would be the cheapest way to go? I'd like to try to keep it all under $600.

Any thoughts on my logic?
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