In this gallery, you will find pictures of my most recent DIY project. Around Summer 2009, I tossed around the idea of upgrading subwoofers from my A2-300 and considered many options, including another DIY subwoofer. In October of 2009, I had the chance to make my dreams come true. Initially a project for a single 18" ported subwoofer tuned to 15hz (design currently employed as a DIY kit at eD now), I decided to travel down a road less traveled. Actually, a completely unique project. Not only does this subwoofer have dual 19Ov.2 drivers, an LT/1300 amp, and bracing that makes the subwoofers heavy enough to be a boulder, it is larger and is tuned lower than the A7-900. Dimensions are 49" wide, 36" tall, and 24" deep. The subwoofer uses a double baffle design, similar to the A7-900, and is built with 3/4" MDF wood. So we have it; the beginning assembly.

Here is a picture of the bracing. The bracing took nearly as long to do as the assembly of the entire cabnet since the bracing had to be cut as it went along. Needless to say, the enclosure is ridiculously rigid.

The vent is the port of the sub. It is much larger than any conventional port, and much longer. The port and enclosure size enable the subwoofer to provide a nearly completely flat response down to around 8-10hz before roll off. The sound is not unlike a large sealed enclosure and the output is still outrageous ported. The term for a subwoofer of this size is LLT; Large and Low Tuned.

Moving the subwoofer required a dolly. This picture should explain why.

To give you an idea of how much "stuffing" I'd need, I placed the pillows on the ground where the sub would be placed. The pillows would act as Poly-fill inside the subwoofer for additional lowering of tuning by about 1hz and to reduce any additional internal noises, if any.

The sub, after a week of labor, is finally assembled! Partially that is. The rest is to come...

Here was when I brought out the drivers, amp, pillows, wiring, and tools necessary to connect everything and get it all hooked up.

Here you can see the six pillows stuffed up in between the bracing of the sub.

After connecting the drivers to the amp, I was ready to install the drivers.

A picture of the LT/1300. It is provides 650 watts per driver. With the ICE Power integrated into the amp, the amp is able to provide sustained power at low distortion, is incredibly dynamic, and has a class D design with 87% efficiency and with sound quality similar to class AB amplifiers.

My initial reactions were unimaginable. I was practically hopping up and down, partially because of the subwoofer. My first tests were with Bass, I love you and some other bass sweep tests. Needless to say, I was very shocked. I barely had the gain up at all and felt like I was getting pummeled by a jackhammer during the low frequency sweeps. When I played 10hz on my system before, I heard a little bit of air moving around and not much more. 10hz now was like the room was getting sent through a time machine. The little wood blocks underneath the subwoofer did not stay very long underneath the sub. My next solution was to find some better absorptive material that could help decouple the subwoofer from the ground and withstand the weight of well over 300+ lbs. A trip to Home Depot was next.

After changing the blocks out, I decided to pick up some foam board insulation at Home Depot for the isolation/riser. I cut the board into four pieces, just nearly perfectly fitting the dimensions, and now have a very inexpensive, albeit temporary solution for isolation.

Out of curiosity one day, I decided to disconnect the living room subwoofer's amp (the vintage Techincs amp) and try it out with my system. Let's just say the living room sub has been sitting for a good while now without power. At 41 watts per channel with class A amp topology, the sound is a marked improvement over the Onkyo amps for the SDA's. The Technics amp is actually rated at 41 watts at 8 ohms but I believe it is more around 50-60 watts (not 82 watts) for 4 ohms on this one. With the SDA's efficency, only with movies does it start getting a workout. At ~95dB, it's only reading about 20 watts a speaker.

Although this is when I ran REQ back in December, I can only be sure that the frequency response has improved even more. This graph was before I had my front speakers properly placed, my sub raised off the ground properly, and before I did many setting changes and calibrations. The sound card in my laptop also limited the response I had, frequency and output wise, hence the 70.1dB set level. Regardless, this is a VERY pleasing graph. The graph definitely confirms my feelings about what I was hearing and feeling. Imagine that flat response up to over 120dB.

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Comments (6)

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Driver_King  » Mar 03, 2010 05:57 PM

I have not taken any measurments of THD for the sub, but the response is at seating position. With the subs playing together, I cannot imagine a more accurate reproduction of bass in my room. It's hard to describe. The subwoofers are seamless extensions of the speakers around the room. In critical listening sessions, I cannot really complain.

kareface  » Feb 26, 2010 03:44 AM

How is the harmonic distortion below 15hz? Is that the response at listening position or are you doing a near field measurement?

ShockWave  » Feb 19, 2010 04:33 PM

WOW!!!!!!!!!!!!!!!! AMAZING KING KONG!!!!!!

Driver_King  » Feb 19, 2010 12:20 AM

Thanks Vega! By the way, if anyone has a thought on what color/veneer I should go for, let me know. I was thinking maybe Mozambique but found out to veneer it all with Mozambique would cost me quite a bit of $.

Driver_King  » Feb 19, 2010 12:14 AM

Yes, it is ugly right now. I have not had time to veneer it. That is one thing I did not mention here. In all honesty though, I didn't do it because I wanted necessarily more bass but better bass. It is strange how it worked out but the upgrade to this DIY A7-900 (the real thing of which costs $2500) cost me less than an A5-350 and around the price of an SVS PC-12NSD. I have everything calibrated back to 75dB now and everything blends seamlessly.

vega2K  » Feb 18, 2010 10:17 PM

I can't wait until Big Daddy and CrazyBlu get a load of this! Unbelieveable! Congrats! 10/10 Please keep those pics coming!

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