Jaycar 12 inch Double Magnet subwoofer
Jaycar Part no: 2228 - Cost $279aus (5th May 2005)
|Single coil driven||Both coils driven in series|
|Z - Nominal Impedance||4 ohm||8 ohm|
|Pe - Power Handling||150W||250W|
|SPL - Sensitivity||85.5 dB/watt@1m||88.5 dB/watt@1m|
|Re - Voice coil resistance||3.7 ohm||7.2 ohm|
|Fs - Resonant frequency||24 hz||24 hz|
|Qms - Mechanical Q||3.58||3.75|
|Qes - Electrical Q||0.48||0.236|
|Qts - Total Q||0.423||0.222|
|Vas - Equivalent volume||75 litres||75 litres|
|Xmax - Maximum excursion||5.5 mm||5.5 mm|
|Sd - Cone Area||487 sq cm||487 sq cm|
|EBP - Efficiency Bandwidth Product||50 - Best sealed||102 - Best ported|
Here is my parameter file for this driver ( single coil driven ) for WinISD Pro ver 0.50a7
Here is my parameter file for this driver ( two series coils driven ) for WinISD Pro ver 0.50a7
They also list specs for a parallel connection, which I have omitted because the resulting 2ohm impedance is too low for their Home Theatre plate amps.
|Box size||Tuning frequency||Port details|
|Jaycar design||45 litre sealed - single coil driven|
|My design||100 litre box - single coil driven||24hz||Two 86mm ports 540mm long|
|My alternate design||100 litre box - both coils driven in series||24hz||Two 96mm ports 680mm long|
My design - driven by 150w into 4ohms using the 240watt amp
My design - driven by 240w into 8ohms using the 350watt amp. A little disappointing - I had hoped for at least 110dB
Port air velocity
Running the 2nd coil in the vented design gives a benefit in extension but no extra SPL and requires a larger amp. Some more SPL is available but only by going to a much larger box (400l)
Calculated with Flare-it
For the dual 86mm port design:
I would recommend 15mm flares. If you have a full size router, you can use a 19mm rollover bit for routed flares. If you have a small router, you could get away with 13mm flares.
For the dual 96mm port design:
Firstly, the ports could be changed to 103mm diameter. This utilises commonly available pipe. The length becomes 790mm, and the peak velocity drops from 11m/sec to 9.5m/sec.
This would require 11mm flares, so a 13mm rollover bit for routed flares would be perfect
For either design:
You could use heat molded flares in 20mm or 25mm radius.
The intakes should be fitted with a donut ring . If you are using a heat molded flare, you could do a one-piece design with a 20mm flare on the inlet
See the Porting section for more detail on the design, construction and purchase of flared ports.