A smaller sub proposal 
Saturday, February 20, 2010, 13:00
Posted by Anders
Another loudspeaker project, this time a much smaller 6.5" based version, but still it relies on the same tapped horn principles as the larger 15" version posted earlier in this blog.

On a side note I'm happy to announce that the 15" bigger brother design was built in Australia, Brazil, France, 2x USA (NYC and other) Macedonia and Sweden, and perhaps (probably) even more places that i do not know about yet.

Now it's time for a more domestic friendly version on the same theme, hopefully this, the baby version, will make for a small and easy weekend DIY project for those of you seeking to build a small sub for the computer or home theater system without upsetting the balance and harmony of the household.

This design has not been built to date, but the results of the design phase seems good enough to post for others to take part of.

Here's what it looks like as a 3D CAD representation :

(click the images to enlarge them)

Please note that the size of this sub is only 47x44x20.4 cm, yet it holds a 2,4 meter long horn path inside.

This is achieved by using 12mm thick plywood, and cleaver tweaking of the inner layout, the small surfaces also allows for a design entirely without inner brace panels.

Front view :

Section A-A from front view :

And then we have the Hornresp simulation input data :

The driver is the 6,5" Audes 40W65-8 that seemed to to the best job in the simulation of this very compact design, but there might be others out there that work just as well (as we found out with the 15" bigger brother).

The simulated SPL/frequency graphs below are made with several different placements in a room in mind, the input level in the simulations are 2.83 Volts or roughly 1W.

When placed in a corner :

When placed by a wall :

When placed in the middle of a room :

The intended range of this sub is 40-110 Hz but as we have seen before, the lower end range may extend further then that of the simulation by approx. 10Hz, this has been the case in many builds before, so with a little luck this small sub may reach down to 30Hz in room response.

The prefered driver for this design is the above simulated Audes 40W68 (previously known as 40W65-8), but I have looked at some other drivers that might work with this design as well.

The Seas H1224 L18RNX/P (corner):

The Seas H1215 CA18RNX (corner) :

The Peerless HDS PPB 830874 (corner) :

The Silver Flute W17RC38-08 (corner) :

18sound 6ND430 (along a wall) :

Beyma 6P200Nd (along a wall) :

If you want to build it please keep in mind that the mounting of the driver may pose a challenge but there are several ways to cope with this, either pre-mount it, or drill four holes on the cone facing outer piece large enough to fit the shaft of a screw driver, then mount the driver using nuts held in place by hand though the horn mouth, you'll figure it out.

Good luck with the build, please let me know what you think.

Br // Anders Martinsson
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