An interesting weekend enclosure project.

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This past weekend I built a test cabinet with a double tuned reflex design. Audio Physic uses this type of design in their smaller speakers. I've spent quite a bit of time with the Spark III and in the correct sized room, it is a bass powerhouse.

The first data that I found on this subject was in the "Weams" book. He used three ports for his design. I found another website that had some different designs and some more info.

For my test, I used the DCAAV design from Claudio's website. I first drafted up a reflex box tuned to 50Hz for my Eton 7-372 woofer. It ended up being .7cuft with a 3" x 8.75" port. To this, I added a second cabinet with the same volume and port length(compensating for different braces and the volume of the woofer, etc) . The idea, as I understand it, is that the woofer (above 50Hz) doesn't see the second chamber. Below 50Hz, the woofer sees a 25Hz tuned enclosure. It's kind of cool in theory.

While you still don't get something for nothing, fter some listening, I've found the results to be very pleasant and worthwhile. I measured the test cab using Clio and indeed there is quite a bit of output down to around 25Hz. The response is also quite flat throughout the transition region (25-45Hz) between the two chambers.

I'm going to try to build a second matching cabinet this weekend. I will post some pics when both speakers finished are "clothed".

If any of you all have tried this or know of a source for more information please share!!

I built a test box with 2 8" Dayton Classic woofers. I used the the Double-Chambered Reflex box on Claudio's site. The MJK's worksheet program is here;
I didn't use his program, but I did use Unibox and Ports.xls from diysubwoofers site.
Here's a pic of the test box. It's kind of big;
I also lined it with 3 1/2" fiberglass and left a cavity for the ports to resonate. Like you the transition from chamber to chamber was smooth and undetectable. When I first fired them up the first thing I noticed (heard) was how deep they sounded. They sure gave my Rock CD's a kick in the ***. Another thing of note was the power handling capability. With my other test boxes using the Dayton 8's the speakers would bottom out pretty quick, not with the DCR box. The ported box I built doesn't even compare to this DCR box. I hated the sound from the ported box. When playing the Bass Mekanik CD the ported box would unload below resonance and slap like heck, even at low power levels, not the DCR. They took the Bass Meckanik Test CD fairly well. I was very surprised. My next box I build will use the 10" woofers. I really liked the kick these type of boxes put out. Down the road I'll probably try the DCAAV usin MJK's worksheet. I just finished 2 test boxes using the Dayton 8's in MJK's ML-TL worksheet. Very nice & tight bass. Very clean sounding. Very good for low to medium volume playing. Jazz and pop really shine through them, but I like to crank it up now and then and that's where the DCR or DCAAV boxes will come into play.
They're not that much more expensive to build or that much harder. I don't see why there isn't anymore designs using these type's of boxes out on the web either????
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