Speaker box dimension following the "Golden Ratio" = 3.318 cu. ft. vB. Depth 11" Height 30" Width 18" 60hz Speaker System Resonant Peak and 60hz F3. Smooth as silk speaker response. You could use 2.24 vB for a 70hz Speaker System Resonant Peak. It's up to you.
Speaker Driver Tweeter L-Pad = Resistors R1 = 3.1 Ohms(series) R2 = 1.15 Ohms(parallel) Use Mills Non-inductive resistors. Values: 3 and 1.2. 13db of attentuation
http://www.partsexpress.com/webpage.cfm?WebPage_ID=110
Speaker Driver Tweeter Bass Blocker - Capacitor Value 14uF Inductance Coil Value .45mH. Second Order Buttersworth Design
http://ccs.exl.info/calc_cr.html#second Capacitors: Use Solen non-pollarized 15uF 400VDC Polypropylene capacitor
http://www.partsexpress.com/webpage.cfm?&DID=7&WebPage_ID=71 Inductor: Use .45mH Jantzen 20 Gauge Air Core Inductor
http://www.partsexpress.com/webpage.cfm?&DID=7&WebPage_ID=197#20gauge
Tip: The phase of the tweeter driver will go out 180 degrees because of the Second Order Buttersworth design. So, make sure to reverse the polarity when attaching the bass blocker to the tweeter driver and to the speaker hook up wire. That means, attach the positive wire to the tweeter's negative post, and the negative wire to the tweeter's positive post. However, you will want to try it both ways, and see what you prefer. Some people like that out of phase sound.
Since you'll be using a three speaker system, I would attach the two 10" drivers in series. This will give 16 ohms. Then, attach the tweeter in parallel. The tweeter was 4 ohms. So, R1 = 16 and R2 = 4. The woofers would be one parallel circuit together, and the tweeter is the second. So, the formula is Rt = R1xR2/R1+R2. Therefore, Rt = 16x4/16+4, which is Rt =64/20, which is Rt =3.2 ohms. The ohm rating of the cab with this design would be 3.2 ohms. Your bass amp should be 4 ohm stable. It's close enough. Plus, if one of the bass drivers blow, both would stop working since they're hooked up in series. That would leave a ohm rating of 4. That's stable for the amp. And, if the tweeter blows, you'll have a 16 ohm rating on the two bass drivers which I know you bass amp can handle. This solves your three speaker hook up problem.
Good luck! Let me know how it turns out!
