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Joel's First DIY Build: 15" Subwoofer

post #1 of 23
Thread Starter 
Hey everybody, I just completed my first DIY speaker build yesterday. It's a 15" subwoofer built from a MDF flat pack from DIY Sound Group. Here are the components I used:

- 3.0 ft³ subwoofer box
- Dayton Audio Reference Series 15" subwoofer, 4Ω
- Paper backed flat cut cherry veneer, 2' x 8'
- Watco Danish Oil, natural
- Heavy duty rubber feet, 1-3/8" x 1"
- Speakon 2-pole panel mount connector
- #8 x 1" pan head screws
- Polyester fiberfill
- 1/4-20 x 2" socket flat head screws, black finish

As others have mentioned, the DIY Sound Group flat packs are outstanding. Mine fit together perfectly. I figured out a way to glue the panels together in a few steps using no clamps, just using a heavy box to keep the glued joints together during setup.

I'm a rookie when it comes to veneering, but the whole process was easier than I expected. I used Heat Lock glue applied with a roller to both surfaces, allowed to dry for ~30 minutes, placed them together and re-activated the glue with a clothes iron. After letting it cool I trimmed the edges using a router and a flush trim bit. There were a couple of edges I had to mash down with the iron a second time. Then I carefully sanded the edges with 180 grit sandpaper, and sanded all the surfaces with 400 grit. I flooded the veneer with Watco Danish Oil and rubbed it in on each side with 600 grit sandpaper for about ten minutes, then wiped with a cotton cloth. I love how the veneer turned out.

For the front baffle I first sprayed on a fill 'n sand primer and sanded with 220 grit paper. I probably should have sealed it with shellac first, because the first coat of black paint looked rather uneven and raised the grain (or whatever you call it on MDF). I sanded that coat with 320 grit paper and painted it again, which did the trick.

The remainder of the assembly was time consuming but simple. I drilled a 15/16" hole on the back for the Speakon mount and secured it with two #6 tapping screws. The barbed inserts for the rubber feet were secured with two part epoxy. I used about 2.5 pounds of the fiberfill in the box.

I am powering this sub with a Crown XLS 1500 amp set to bridged mono mode, which pushes 1,500 watts into 4Ω. I turned the gain pots about 3/4 of the way up and ran the Audyssey setup on my Integra pre-amp. All I can say is "wow." It subtley adds an amazing bottom end to my Epos Epoch 5 tower speakers. The sub seems to be just loafing along during music tracks but really comes alive for effects in movies. This seems to be the perfect sub for my home theater and it's great to say I built it myself.

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post #2 of 23
bravo! that looks fantastic!
post #3 of 23
Looks great! I highly recommend purchasing a MiniDsp to boost the low end and EQ to a slightly slopping/flat response.
post #4 of 23
Thread Starter 
Quote:
Originally Posted by Martycool007 View Post

Looks great! I highly recommend purchasing a MiniDsp to boost the low end and EQ to a slightly slopping/flat response.

Hmmm, I've heard of that but don't know much about it. I'm running balanced signals to my amp, so should I buy this miniDSP? https://www.minidsp.com/products/minidsp-in-a-box/minidsp-balanced-2x4 To do what you're suggesting, that means using a mic and REW software?
post #5 of 23
who knows what audyssey may already be doing. even an spl meter and some test tones would give some insight in what your frequency response is.
post #6 of 23
Thread Starter 
Update: I acquired a miniDSP and wired it into the subwoofer signal. I did not attempt the "Linkwitz transform," although I would probably benefit from it. I did try the parametric EQ using REW and a UMIK-1 USB microphone. REW gave me these EQ filters, which I uploaded into the miniDSP:

Filters_zpse4841fea.jpg

EQGraph_zps954dd405.jpg

This stuff is Greek to me, but hopefully what I did improves the sound quality. Anyone care to comment on the EQ filters? After programming the miniDSP I re-ran the Audyssey calibration in my Integra.

As for doing the Linkwitz Transform, I read the instructions here: link I understand most of it, except the part about measuring F and Q. So, I'm supposed run a measurement sweep with the mic two inches in front of the subwoofer. I can see how F is determined by looking at the graph, but what about Q? Does REW give me that as a number, or do I have to guess by looking at the slope of the graph?
post #7 of 23

Nice build and thanks for posting.  I'm in the middle my first build (http://www.avsforum.com/t/1510254/css-duet-sdx12b-build), and have been planning to use cherry.  Yours looks great and reinforces my decision. 

 

I'll keep my eye on this thread, because you are several steps ahead of me, and I have some of the same questions you do.  How did you determine the volume of the subwoofer box?

post #8 of 23
Thread Starter 
BadToTheTone, as stated in my original post I used the MDF flat pack from DIY Sound Group. They call it a 3.0 ft³ box. I did not measure it myself, but I have no reason to doubt the size.
post #9 of 23
Quote:
Originally Posted by joel md View Post


This stuff is Greek to me, but hopefully what I did improves the sound quality.

LOL! I think you speak for many of us on this DIY discussion forum! rolleyes.gif

If I didn't already have a great signature quote from Bill Fitzmaurice, your words of wisdom would now adorn the end of each of my posts!
post #10 of 23
Quote:
Originally Posted by joel md View Post

BadToTheTone, as stated in my original post I used the MDF flat pack from DIY Sound Group. They call it a 3.0 ft³ box. I did not measure it myself, but I have no reason to doubt the size.


Yes, saw that, just wondered if you did any modelling or just went with a recommendation from the DIY Sound Group.  I'm doing some with WinIsd and ported.xls, but it's new territory.  Glad to hear you are happy with the results.

post #11 of 23
I dunno how I missed this but every thing looks GREAT! Very nice job, especially for a first project!
post #12 of 23
Thread Starter 
Quote:
Originally Posted by steve nn View Post

I dunno how I missed this but every thing looks GREAT! Very nice job, especially for a first project!

Thanks Steve!
post #13 of 23
Thread Starter 
Quote:
Originally Posted by BadToTheTone View Post


Yes, saw that, just wondered if you did any modelling or just went with a recommendation from the DIY Sound Group.  I'm doing some with WinIsd and ported.xls, but it's new territory.  Glad to hear you are happy with the results.

No, I did not do any modeling. It's a sealed design so I don't know how critical the size is, but DIY Sound Group only sells this size with a 15" cutout. Anyway, I'm not equipped well enough to be cutting speaker cabinets myself so I figured one of these off-the-shelf kits would work well enough for me.
post #14 of 23
Looks awesome! May I ask what sub you had before and how this one compares? I'm considering either a Dayton/Si build myself.
post #15 of 23
Curious, how do you get the edges of the veneer to look good? I've always wondered that. Any close ups?
post #16 of 23
Quote:
Originally Posted by Ryan Flynn View Post

Curious, how do you get the edges of the veneer to look good? I've always wondered that. Any close ups?

 



Flush trim router bit.

Im interested in the technique you did to apply the oil. You say you just put it on and rubbed it in with sandpaper? Do you have a link to an article you read about that?
post #17 of 23
Quote:
Originally Posted by joel md View Post

I flooded the veneer with Watco Danish Oil and rubbed it in on each side with 600 grit sandpaper for about ten minutes, then wiped with a cotton cloth. I love how the veneer turned out.
 

Yes, I am also interested in why you rubbed it in with sandpaper???

post #18 of 23
Quote:
Originally Posted by joel md View Post

Update: I acquired a miniDSP and wired it into the subwoofer signal. I did not attempt the "Linkwitz transform," although I would probably benefit from it. I did try the parametric EQ using REW and a UMIK-1 USB microphone. REW gave me these EQ filters, which I uploaded into the miniDSP:

...

This stuff is Greek to me, but hopefully what I did improves the sound quality. Anyone care to comment on the EQ filters? After programming the miniDSP I re-ran the Audyssey calibration in my Integra.


Great looking build! For the measurement with filters was Audyssey disabled when you did the measurements? If Audyssey wasn't turned off before doing the initial measurement you'll probably have to start over from scratch (it seems likely it was disabled first but I didn't see it specified). Did you do any measurements after applying the EQ filters? A post-EQ measurement is the best way to see if the filters are doing what they're supposed to smile.gif
post #19 of 23
Thread Starter 
Quote:
Originally Posted by Claybe View Post

Yes, I am also interested in why you rubbed it in with sandpaper???

I learned to use Danish oil that way from an old woodworker. If you Google search for "danish oil wet sand" you'll see there are a lot of opinions on how best to apply oil finishes. Basically the sandpaper produces microscopic sanding dust that combines with the oil to form a slurry that fills pores in the wood.
post #20 of 23
Thread Starter 
Quote:
Originally Posted by lennon_68 View Post

Great looking build! For the measurement with filters was Audyssey disabled when you did the measurements? If Audyssey wasn't turned off before doing the initial measurement you'll probably have to start over from scratch (it seems likely it was disabled first but I didn't see it specified). Did you do any measurements after applying the EQ filters? A post-EQ measurement is the best way to see if the filters are doing what they're supposed to smile.gif

No, I did not turn off Audyssey when I took the measurements. Looks like I better start over, and then do a post-EQ measurement.
post #21 of 23
Quote:
Originally Posted by joel md View Post



I learned to use Danish oil that way from an old woodworker. If you Google search for "danish oil wet sand" you'll see there are a lot of opinions on how best to apply oil finishes. Basically the sandpaper produces microscopic sanding dust that combines with the oil to form a slurry that fills pores in the wood.

 



Thanks!
post #22 of 23
Thread Starter 
Quote:
Originally Posted by Tripledub View Post

Looks awesome! May I ask what sub you had before and how this one compares? I'm considering either a Dayton/Si build myself.

In my last house I had a home theater with Boston Acoustics speakers and a Denon receiver. Don't remember the exact BA model, but I had a powered sub that was pretty good, think it was 10". I lost all of that in a divorce so my current system is completely new. To be candid I think my old BA subwoofer sounded better for movie effects, and as with any powered sub it's really simple to just plug n play. But this whole DIY thing has been kinda fun, and people are impressed when I tell them I built it myself. It definitely looks more like furniture compared to those store-bought subs that all look the same. Maybe once I get this subwoofer dialed in better with a Linkwitz transform and EQ'd properly it will sound better than the Boston Acoustics sub in my previous house.
post #23 of 23
Interesting...thanks. Kinda surprised the DIY didn't destroy the BA
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