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Discussion Starter · #1 ·
Figured I'd have a go at a DIY sub...


2 12" ED drivers 13Kv2 4 + 550 amp + two 4 " ports. Fingers crossed, I hope to end up with a 20hz tune in a 6 cubic ft (internal) box with 18" port length. WinISD reports this can be achieved with the aforementioned drivers, ports and box size. The box will be 36" x 20" x 19"


I have not cut the top or the bracing pieces, but that's next on the list.


Bottom layers:



Drivers will mount to this:



Fronts and sides:



Drivers. I originally bought a single driver, then realized it's a dual 4. So, of course, I did the sensible thing and bought another.



Little Hsu Research will need to find a new home:
 

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Lookin' good.


Contrary to "popular" belief - they're actually good little drivers. I've got one, and used some before and was very pleased for the price - and at the "throw em away" price they have on the D4's now it's a steal.
 

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Discussion Starter · #3 ·
Box on its side:



Bracing:



Looks like it will come in at 5.3cft. With 17" ports this will give me a 19hz tune. - if i've done the calcs correctly.
 

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Certainly doesn't look like your first DIY job, nice!


You should be happy with dual drivers. I have a hard time recommending a single to anyone
 

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Will it make a difference if one woofer 'breaths' easier than the other?


I am talking about the placement of the porttubes..
 

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In my dual build, i isolated each driver and port in it;s own air space-worked out fine but don't have a comparison of 2 drivers sharing the same space. I imagine theoretically there may be some anomolies due to driver to port spacing and the like but without comparative measurements it would be speculation at best. That's why i isolated them-imeasuarable at best in shared air space. Just a thought.
 

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Discussion Starter · #7 ·
This being my first DIY speaker build of any sort, i'm in the 80/20% range on winging it/science. I did ponder, as Kanaris mentions, if the one driver will breathe easier than the other. I'd bet that is probably correct. I am wondering if it will make a difference in the overall effect. There is plenty of real estate left on the brace to put in some holes - if it's gonna make a difference. I'm also considering a full front to back brace, or, four more triangles like the ones in the inside corners.


Feedback is welcome.
 

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Good work.


Extra time invested in the build is time I consider well invested. The sub should come out great.
 

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Discussion Starter · #9 ·
I tested the sub over the weekend.


Without actual testing with audio software and a mic, I observed the following:


1. The sub is too big. It looks sorta odd in position, and is not WAF approved - I have to agree actually. Photo evidence will be posted tomorrow.


2. With the sub gain turned to the 8 o'clock position, the room pressurizes to an amazing level. Forget 10-11 o'clock- it hurts.


3. There is a huge volume peak, I'm guessing between 30-50hz. This could be tuning, internal box layout, the PE Bash 500w amp, room layout, or most likely a combination of all mentioned and more. Audio testing would confirm the peak, however, given the size issue testing of the current box is moot.


I'm going to cut the box in half, redo the bracing, maybe get a 4 ohm driver and retry.
 

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wad up some socks or a towel and plug one port, then plug both. It might cut back on the roar if your box was tuned too high.


If you still need less bass just build 2 sealed cubes and hide them on opposite sides of your room, this will help even out the response in your room. Then run wires back to the amp
 

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Discussion Starter · #11 ·
I'm thinking the box is tuned too high, combined with the 2db or so peak at 30hz inserted by the PE amp. I'm going to change the resistors in the amp to bring the bass boost down to the 20hz range.


I plugged the ports, per Dan's suggestion. With one port plugged, the sub isnt as boomy but I think the 30-50hz range is muddier. With both ports plugged, the sub has more punch, is less muddy, but is missing quite a bit down low. The ports are 4"x17"


I really need to get some audio measurements before I redo this box. I'm curious now if the present build can be corrected to something better.


In a previous post I mentioned this build is 80/20 winging it/science. I really need to flip that to 100% science for a better result - although building and experimenting is darn fun.
 

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Discussion Starter · #12 ·
I plugged my final box/driver numbers into winisd. It is reporting a 2db peak between 27 and 39hz with both ports open. With one port open there is a 1.5db peak between 24hz and 40hz. I missed these results when initially using winisd to calculate tuning, oh well.
 

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Discussion Starter · #13 ·
Lost a bunch of posts... bummer.


The old dual sub was a bust. It didnt sound good, it also looked comically oversized once placed in the ht. WAF rejected.


I figured part of the problem was the amp. Stock it has a 2db boost at the 36-40hz range which, I suppose, accounts for the boominess. I put it on craigslist and picked up a PE 500W amp instead. I could have swapped the resistors, per the manual, but my soldering skills are rusty, and I didnt want drop $228 on a soldering mistake.


I decided to try a sealed design, with room to install ports later. I did not take picitures of the initial cutout and glue-ups. Flaming for this oversight is approved.






Bit of Bondo to correct bad routing:
 

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You do nice work. It's a shame the old box didn't do the job, it was well built. Did you try moving it around the room? It could have just been in a bad spot. I know with things this size, sometimes there is only one place to go, that's how mine is.
 

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Discussion Starter · #15 ·
I did try the dual sub in one other spot and it still sounded boomy and weird, even with one or both ports plugged. And it looked like an orphaned coffee table out in the open.


With this new single sub, it sounds better and better the more it's used. I'm really pleased and surprised - I was a bit worried with the DIY thing after the first build.
 

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Discussion Starter · #16 ·
I recall in a lost post someone asked if the driver and amp were flushmounted. The answer is yes, they are. The driver hole was cut with router and circle jig. The driver face is two layers of 3/4 MDF with a 3/4 rabbet on the outer piece. The amp side is a single layer of 3/4 MDF with a poorly cut rabbet - hence the Bondo. I made a template, after the fact, which can be used to accurately cut a hole for the PE plate amps.
 
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