Loudspeaker Designs and Articles for the DIY Enthusiast
This is 2.5 way design with 3 woofers below and 1 woofer above, flanking the MTM mid woofers. The drivers are wired in 3 sets of series pairs, which are
ultimately paralleled through the network. The six woofers are first driven through a common network. This consists of a LP filter L0011and C0021. R0021
helps shape the knee of the response. R0011 and C0011 work in conjunction with L0011 to function as an elliptical filter, notching out the woofer response
peak at 7 kHz. This circuit drives the MTM woofers labeled as 2 and 3 on the network drawing. The circuit also connects to L2011 which is in series with the
4 0.5 woofers, labeled 1, 4, 5, and 6. The value of L2011 was chosen to ameliorate the lack of imaging often heard in vertical arrays of drivers. By choosing
such a large value of inductance, the resultant sound does not affect the bass response at all, but images very well, sounding more like a small bookshelf
speaker than a tower.
The tweeter is about as simple as a 2nd order crossover can get. No tweeter attenuation resistor is used, but a 1 or two ohm resistor could be placed in
series with the tweeter if something other than near wall placement is required. It initially exhibits a very low Q 2nd order transfer function, but transitions to
4th order at 1500 Hz. There the filter response are overlapped providing good driver integration. Note the tweeter is connected with reversed polarity.
|A high sensitivity
high SPL design
Tips and Tricks:
Caution: Wire hazard ahead! With all the wires and series parallel combinations in this design, I suggest you label
the number of each driver to correspond to my numbering scheme. Also label each wire as you lay it in the
enclosure as to what driver it goes to. I.e.: Woofer 2 minus, Woofer 1 plus, etc.
Note that Woofer 1 - tab is connected to woofer 4 +, Woofer 2 - is connected to woofer 3 +, and Woofer 5 - is
connected to woofer 6 +
All woofers are connected with normal polarity. Each woofer pair represents roughly a 16 ohm load, so 16
gauge, or even 18 gauge internal hookup wiring will be more than sufficient in this instance.
The tweeter is connected with reversed polarity.
The Common Net provides the low pass filter to cross over the six woofers to the tweeter. It connects to the binding
posts and its output feeds the inputs of Net 3 (the MTM pair) and through the 7 mH series inductor, Net 1 and Net 2.
Net 4 is the tweeter network, and it is connected directly to the speaker binding posts.
Net 3 is the woofer pair flanking the tweeter, connected in series and wired across the common network.
Net 1 and Net 2 is the four woofers wired in series parallel, and also wired to the Common Net through the
aforementioned 7 mH inductor.
Click on the image below for the kit provided by:
The numbers adjacent to the woofers in the network drawing above
correlate to the numbered positions in the baffle drawing below. it is
imperitive that drivers 2 and 3 flank the tweeter. The other drivers
positions are not critical, but for simplicity's sake, I'd suggest you
follow the number scheme I've set out.
All pictures courtesy of Alejandro Fernández Valdespino