Yea I am finally having a sub-woofer made.
Actually it can be used for more than just a sub-woofer. It plays smoothly to 500Hz.
I had several objectives for this design.
As a sub-woofer I wanted low end extension with a -3db close to 20Hz.
I also wanted to do it with a relatively small box.
The main focus was to be on sound quality not quantity.
It also needed to have a nice smooth response up to about 500Hz so that it can be used in three way designs.
To get the low end extension the box has to either be ported or used with a passive radiator. Since the ports will be huge to tune a small box to a low Fs the solution was a matching PR. So they were designed together to be used together.
Since sound quality was high on the list a treated paper cone material was chosen as well as a dust cap made from the same material.
They both use the same cast aluminum frame.
A large 1.5" rolled surround was used to minimize any cone flex as the limit of the X-max is approached. This will reduced distortion that occurs from cone flexing.
I am not a big believer in playing woofers to levels that force really high X-max's. Long exertions equals high distortion.
If you want to move a lot of air and you want it to sound good then I recommend using more woofers.
Here are the specs and the tuning of the box according to Bass Box software. Adding a little bit of mass to the PR in the test box I was able to confirm the tuning with an impedance sweep.
The final product (PR) will have a bolt running through it that will allow for mass to be added as per washers and screws.
Laudspeaker Parameters
-General Information-
Company: GR Research
Model: 12 inch
Note/SN:
-Mechanical Parameters –
Fs = 20.5 hertz
Qms = 4.85
Vas = 3.56 cu.ft or 101 liters
Cms = 0.057 in/Ib
Mms = 5.964 oz or 169.1 grams
Rms = 9.843 Ibs/sec
Xmax = 16 mm
Sd = 72.5 sq.in
Dia = 9.6 in
-Electrical Parameters-
Qes = 0.440
Re = 6.7 ohms
Le = 5.16 mH
Z = 8.0 ohms
BL = 18.5 N/A
Pe = 200 watts
– Combination Parameters –
Qts = 0.40
qo = 0.201%
Sens = 87.03 dB (2.83 V)
--Multiple Drivers-
Number= 1
Single
Wiring: single
Single Driver Passive Radiator Box Parameters
Vb = 2.400 cu.ft
Vap = 6.000 cu.ft
Fp = 12.5 hertz
F3 = 20.8 hertz
Fill = normal
Oh yea! I need to think of a name and or model number for these things. Any good ideas.
There is currently a small run of 200 woofers and 200 PR's being built, just to see how they go first.
I also plan on using these in two three-way kits in our A/V series. Looks like lots of fun ahead....
