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DIY A7-900 (14 photos)(4.8) (17 ratings)
Uploaded Feb 18, 2010 20:11:49
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.
Uploaded Feb 18, 2010 20:30:55
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.
Uploaded Feb 18, 2010 20:30:58
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.
Bringing it in.
Uploaded Feb 18, 2010 20:31:10
Moving the subwoofer required a dolly. This picture should explain why.
Poly-fill on steroids
Uploaded Feb 18, 2010 23:33:40
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.
An empty shell...
Uploaded Feb 18, 2010 23:33:43
The sub, after a week of labor, is finally assembled! Partially that is. The rest is to come...
The equipment arrives.
Uploaded Feb 18, 2010 23:33:45
Here was when I brought out the drivers, amp, pillows, wiring, and tools necessary to connect everything and get it all hooked up.
Packing the pillows in.
Uploaded Feb 18, 2010 23:33:48
Here you can see the six pillows stuffed up in between the bracing of the sub.
Uploaded Feb 18, 2010 23:33:51
After connecting the drivers to the amp, I was ready to install the drivers.
Uploaded Feb 18, 2010 23:33:53
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.
Uploaded Feb 18, 2010 23:33:56
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.
Front Soundstage Currently
Uploaded Feb 18, 2010 23:57:54
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.
Uploaded Feb 18, 2010 23:57:57
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.
Uploaded Feb 19, 2010 00:08:43
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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