Notes
11 Sept 2002: I have made a small adjustment to the XO to bring the
XO freqeuncy down. It is now about 2850Hz, and it sounds noticably better.
Amazing how much difference a small change can make. I've also corrected the
diagram of the brace. I also need to see what I can do about that 5dB dip
at 450Hz, although I believe it's in the box and I'll have to live with it.
Design Goals
I'm working on this speaker as a temporary replacement for my mains,
which will have to be scavanged for parts to make my new mains.
The end goal is a 2.5-way, but I took a side trip through a simple
2-way to get to know the drivers.
Drivers
The woofer is the GR Reasearch
M16, the tweeter a Scan Speak D2010/851300 3/4" silk-dome.
The M16 is capable of good, tight bass, but is a little dry in the upper midrange. It should probably be crossed over lower than I'm using it in this design, but it's still plenty good enough for a $24 woofer.
The SS 8513 is a good tweeter. Think of it as a middle-class Hiquphon.
The M16 is capable of good, tight bass, but is a little dry in the upper midrange. It should probably be crossed over lower than I'm using it in this design, but it's still plenty good enough for a $24 woofer.
The SS 8513 is a good tweeter. Think of it as a middle-class Hiquphon.
The Box
The box is sealed (no port) and is 38 1/2" x 6 1/2" x 13 1/2" (HxWxD) and made
from 3/4" MDF. There are three shelf braces, one between the woofer and
tweeter, the second below the woofer, and the third about 12 inches below that.
The box is fully stuffed with Poly-Fil. The target Q is 0.577.
Cut the holes in the braces however you're comfortable. I recommend cutting 3 rectangular holes, each 3"x3.25", like so...
NOTE: The box in the pictures is 37 1/2" high. I decided an extra inch was necessary to cut down on some baffle diffraction from the tweeter.
The drivers are both centered on the baffle. The tweeter's center is 3 5/8" from the top and is flush mounted. The woofer's center is 9 1/2" from the top, and is NOT flush mounted.
Here is a very large drawing of the box which shows both the 2-way and 2.5-way configurations. (The 2.5-way XO is not yet finished.)
TIP: To save you some cutting, you can use the 12" wide MDF shelves available at Home Depot for the sides, top, bottom, and braces. It should take five 12"x48" shelves and two 24"x48" sheets of MDF to make a pair of speakers.
Cut the holes in the braces however you're comfortable. I recommend cutting 3 rectangular holes, each 3"x3.25", like so...
NOTE: The box in the pictures is 37 1/2" high. I decided an extra inch was necessary to cut down on some baffle diffraction from the tweeter.
The drivers are both centered on the baffle. The tweeter's center is 3 5/8" from the top and is flush mounted. The woofer's center is 9 1/2" from the top, and is NOT flush mounted.
Here is a very large drawing of the box which shows both the 2-way and 2.5-way configurations. (The 2.5-way XO is not yet finished.)
TIP: To save you some cutting, you can use the 12" wide MDF shelves available at Home Depot for the sides, top, bottom, and braces. It should take five 12"x48" shelves and two 24"x48" sheets of MDF to make a pair of speakers.
The Crossover
Pretty boring. 4th-order LR acoustic at 3K or so, although the null shows up higher.
As always, don't get too worked up over the DCR of the inductors.
Conclusions
As I said above, the M16 is a little bit dry in the upper registers.
And since I centered the tweeter, there is a bit of roughness through
the top octave. This mostly goes away off axis, so don't point the speakers
directly at you when listening. Also, keep in mind these
I have not yet taken an actual impedance measurement, but the sims show a low of 6.8 Ohms at about 3.2kHz, but with a fairly big phase swing. You will gain some benefit by using a quality solid-state amp with this speaker.
This was taken slightly off-axis, about 15 degrees, using the 37 1/2" test box. I'd say it's +/- 2dB, which is respectable but not great. The dip at 4-5kHz is an edge diffraction, and should be less of a problem using the final 38 1/2" box.
Nice deep reverse null showing the XO frequency at about 2850Hz.
I have not yet taken an actual impedance measurement, but the sims show a low of 6.8 Ohms at about 3.2kHz, but with a fairly big phase swing. You will gain some benefit by using a quality solid-state amp with this speaker.
This was taken slightly off-axis, about 15 degrees, using the 37 1/2" test box. I'd say it's +/- 2dB, which is respectable but not great. The dip at 4-5kHz is an edge diffraction, and should be less of a problem using the final 38 1/2" box.
Nice deep reverse null showing the XO frequency at about 2850Hz.