EZSub14 subwoofer project

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Andrew Pratt

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EZSub14 subwoofer project
« on: 21 Apr 2003, 06:02 pm »
You might be wondering why I'd be building yet another sub when I have two 220L tempest in the theatre. Well this little guy will be for the living room which is our second zone. There's presently two Paradigm Atoms up there that do a nice job for what we need but bass is something they simply can't do well...which is no surprise given their tiny size. Some time ago Bob Reimer from Creative Sound Solutions asked me if I'd be interested in building one of their new subwoofer kits based on the Shiva, EZSub14 and the Sub100 plate amp. Bob happened to be flying to Winnipeg this weekend so I met him at the airport and picked up the box containing the driver, amp, box and all the little goodies needed (glue,wire,stuffing,screws etc) The box it comes in weighs in at 45lbs which didn't seem to heavy when I picked it up off the airport baggage carousel but by the time I got to my car my arms were now a good 4" longer and I'll be visiting my chiropractor soon :) Anyway I told bob that I'd build this sub the way someone without access to tools and a "shop" to see how viable these would be for a complete novice to DIY so here goes...

The first thing I did when I got home was to open the box to see what was in the box. Click Here to see the box and Here to view the contents. As you can see it’s a very well thought out kit with everything needed all provided in a nice well packaged box.

The first thing I noticed after unpacking the MDF for the box was that the edges were routed so that they had a nice dove tail like edge which makes putting the box together incredibly easy and fool proof. Because of these routed edges you won't need clamps to hold the box together...in fact all you'll need is the supplied duct tape to hold it together while the glue dries. Click here to see the box been assembled. Here's a close up of the routed edges and here's a picture of the box being held together with the provided duct tape while it dried. Here's a picture of the bottom of the box showing the cut out for the driver and the amp. It only took about 30 minutes from the time I opened the box to the time I had it glued and taped so it’s very easy to build!

Once the box had dried for a few hours I decided to install the t-nuts to the back side of the bottom plate. Bob was kind enough to include a few extras which is a nice touch in case you happen to loose one during the building process. I was able to hammer the t-nuts into the pre drilled holes but it would have been a lot easier if I'd done that before assembling and gluing the box. You can see the installed t-nuts in this image. You'll note the excess glue along the joints...I doubt it was needed given the nice routed joints but I'm a creature of habit and come from the school of you can never have too much glue:)

To finish the MDF I decided to apply some oak veneer and stain it with a red mahogany stain to match the furniture in the room. Unfortunatly some of the glue soaked though the veneer and the edges didn't seal as well as I'd would have liked. This is my first attempt at applying veneer and the lesson I've learned is that you should never skimp on the veneer...buy the good stuff its a lot less work in the end. I ended up taking my router with a 45 degree bit and putting an edge on the side of the box to clean up the edge of the veneer. I painted that exposed MDF with a dark green paint then stained the whole box with a red mahogany stain. The green paint soaked up some of the stain as well which gives it a nice "weathered" look so over all I'm pretty pleased with it. I then applied two coats of glossy polyurathane to help protect it.


Here's some images of the final product...

Here's how it looks in its final resting spot in the livingroom

Here's the front of the box. If you look closely you can see where the glue's showing though the veneer :(


Here's the side of the sub


Here's what the shiva looks like on the bottom of the box


And finally here's the plate amp


Now that I've lived with the little wonder sub for a few weeks I feel I'm now comfortable talking about the performance of this little wonder. I have been running this sub in my second zone to add to the bottom end of the Paradigm Atoms in the living room. Its been doing a very impressive job in that role. I ran some SPL sweeps though it this afternoon and the results were even more impressive then I could have imagined for a small 12" sub! I placed my SPL meter on the hardwood floor slightly underneath the box and ran a series of test tones recording the value from my analog Radio Shack SPL meter. Here's what those results look like when plotted in Excel.



As you can clearly see this little guy can really belt out the bass which is impressive considering its small size and that it’s a sealed unit! It won't reach down to the low teens like a large ported tempest can but then that's hardly a fair comparison :wink:  What this will give you is solid performance down to about 30 Hz and respectable numbers down to nearly 20 Hz. I'd like to see how many commercial subs at this price point can match these numbers...very few I'd imagine. So would I recommend this sub? You bet I would! It’s exceptionally easy to build and the numbers above speak for themselves...this is a reasonably sized subwoofer that would feel very much at home in someone’s music system on in their Home Theater.

Bwanagreg

EZSub14 subwoofer project
« Reply #1 on: 22 Apr 2003, 02:34 pm »
Nice review Andrew. This looks like a great bargain.

What is the crossover alignment on the plate amp - 12db/octave or something else?

Andrew Pratt

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EZSub14 subwoofer project
« Reply #2 on: 22 Apr 2003, 02:44 pm »
Good question! I'll see if I can find out.

Andrew JC

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EZSub14 subwoofer project
« Reply #3 on: 23 Apr 2003, 12:42 pm »
Andrew, Any idea how much of an improvement by going the upgrade route using the DLP12 and DT300 amp? thanks...andy

Andrew Pratt

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EZSub14 subwoofer project
« Reply #4 on: 23 Apr 2003, 01:42 pm »
I'm not 100 percent sure but from looking at the DLP12 it appears as though its got some nice properties for its intended use in dipole subs but i'm not sure it would sound much different then the cheaper Shiva in the EZ14 box. That said the only way to know for sure would be to model both drivers and see what the response plots are. Alternatively try posting that question to the experts here...if anyone knows the answer its Thomas or Jon.

As far as the amp goes double the power gets you (in theory) an extra 3 dB of headroom which is always a good thing. If you want to upgrade I'd say you'd get more "bang" for your buck with upgrading to the larger amp and stick with the Shiva.

JohnR

EZSub14 subwoofer project
« Reply #5 on: 23 Apr 2003, 03:08 pm »
Cool!

Here's a response curve of the two drivers

http://www.audiocircle.com/index.php?topic=1296.msg10508#10508

Both of those amps have eq which would need to be taken into account.

Andrew JC

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EZSub14 subwoofer project
« Reply #6 on: 23 Apr 2003, 05:38 pm »
John, Thanks for the graph. If I'm interpeting it correctly there does not seem to be a big difference in drivers until around 28Hz where the Shiva starts to break away. Also, the DLP12 plays a little louder under 20HZ. Are my assumptions correct? Thanks...andy

randytsuch

EZSub14 subwoofer project
« Reply #7 on: 23 Apr 2003, 07:38 pm »
What's a dipole sub, and how does it work.  Never heard of it.

Thanks,
Randy

Andrew Pratt

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EZSub14 subwoofer project
« Reply #8 on: 23 Apr 2003, 07:43 pm »
A dipole sub is either a single driver located on a baffle (no box) or a sealed box with two drivers at oppostie sides of the box. These would then move in and out oppostie of each other...ie when one is going out the other would be going in. (if these were reversed it would be bi pole)

JohnR

EZSub14 subwoofer project
« Reply #9 on: 24 Apr 2003, 12:07 am »
Quote from: Andrew JC
John, Thanks for the graph. If I'm interpeting it correctly there does not seem to be a big difference in drivers until around 28Hz where the Shiva starts to break away. Also, the DLP12 plays a little louder under 20HZ. Are my assumptions correct? Thanks...andy

Yes, Shiva has higher sensitivity in the midband, but (without any eq) the DPL12 is flatter in the 25-80 Hz region. I like my DPL12s but the package Andrew describes above looks like it really hits a price/performance sweetspot.

randytsuch

EZSub14 subwoofer project
« Reply #10 on: 24 Apr 2003, 12:21 am »
Quote from: Andrew Pratt
A dipole sub is either a single driver located on a baffle (no box) or a sealed box with two drivers at oppostie sides of the box. These would then move in and out oppostie of each other...ie when one is going out the other would be going in. (if these were reversed it would be bi pole)


Thanks.  That makes sense, just like a bipolar vs dipolar surround speaker for HT.

So, my next question is, what is different about a dipole sub.  If you wire one out of phase from the other, they move in opposite directions, and you get dipole.  Are the cones or something special for supporting a dipole sub?

BTW, thanks for this post.  I have been looking for a subwoofer, and this looks like a great project, for not a lot of money.

Randy

JohnR

EZSub14 subwoofer project
« Reply #11 on: 24 Apr 2003, 12:32 am »
What happens with a dipole is that below a certain frequency the front and back waves from the driver start to cancel each other out. So you need equalization to boost the output of the driver at lower frequencies. This translates into high excursion of the driver.

In the configuration where the back of the driver is exposed, then any extraneous noises from the driver (caused by air moving around the various parts at high excursions) will be audible. The DPL12 has a lot of venting around the back to prevent this.

More than you ever wanted to know on this subject at www.linkwitzlabs.com :-)

Andrew Pratt

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EZSub14 subwoofer project
« Reply #12 on: 24 Apr 2003, 06:43 pm »
FYI there's now a kit with the tempest and DT300 amp that's going for $469US or $679Cdn

link