Desktop speaker project — Bill of Materials

ISU Audio & Arduino Clubs

Desktop speakers – Bill of Materials

Parts to build a set of speaker are available through the ISU IEEE student branch. If you are interested in obtaining a kit contact IEEE or G. Tuttle.
You will need to decide if you want to make the cross-over using the "audio-grade" inductors and capacitors as specified by Carmody (option 2a) or if you prefer to go the economy components (option 2b). The Carmody-crossover option costs about $35 more than the econony version and may give better performance in listening situations.
Most items come from either Parts Express (PE) or DigiKey (DK). The PCBs, wood panels, and other miscellaneous parts are provided by IEEE.
You should stick with drivers and cross-over components as specified below. However, there are opportunities for some variation. See the comments below the BoM tables.

**1. Drivers, port tubes, binding posts**
item	manufacturer	vendor	quantity	item cost	total
midrange	HiVi B4N Mid-bass (4 in)	PE 297-429	2	19.49	38.98
tweeter	Dayton ND20FA-6	PE 275-030	2	10.98	21.96
Port tube 1-3/8" adjustable	Parts Express (1-3/8", adjustable)	PE 260-388	2	2.98	5.96
set of 4 binding posts	Parts Express	PE 091-0250	1	17.49	17.49
Total					84.39

**2a. Carmody cross-over components**
item	manufacturer p/n	vendor p/n	quantity	item cost	total
1.1-mH inductor	Jantzen 000-1078 (air core. 0.57 Ω)	PE 255-252	2	15.54	31.08
0.35-mH inductor	Dayton AC20-35 (air core. 0.4 Ω)	PE 257-030	2	4.09	8.18
6.8-μF capacitor	Dayton DMPC-6.8 (poly)	PE 027-424	2	1.99	3.98
2.2-μF capacitor	Dayton DMPC-2.2 (poly)	PE 027-415	2	0.99	1.98
1.5-μF capacitor	Dayton DMPC-1.5 (poly)	PE 027-412	2	0.79	1.58
0.22-μF capacitor	Dayton DMPC-0.22 (poly)	PE 027-402	2	0.59	0.54
10-Ω resistor	Dayton DNR-10 (10 W)	PE 004-10	2	1.25	2.50
6-Ω resistor	Dayton DNR-6.0 (10 W)	PE 004-6	2	1.25	2.50
terminal block	Phoenix 1935161 (2 position)	DK 277-1667-ND	6	0.78	4.68
PCB	custom	available from IEEE	2	2.00	4.00
Total					61.66

**2b. Economy cross-over components**
item	manufacturer p/n	vendor p/n	quantity	item cost	total
1-mH inductor	Murata 1410516C (ferrite-core, 0.46 Ω)	DK 580-1410516C	2	2.49	4.98
0.33-mH inductor	Murata 18R334C (ferrite-core, 0.34 Ω)	DK 811-1343-ND	2	1.42	2.84
6.8-μF capacitor	Murata FA16X7R1E685KRU06 (ceramic)	DK 445-180434-1-ND	2	0.85	1.70
2.2-μF capacitor	Murata FG14X7R1H225KRT06 (ceramic)	DK 445-173138-1-ND	2	0.53	1.06
1.5-μF capacitor	Murata FA24X7R1H155KRU06 (ceramic)	DK 445-180637-1-ND	2	0.64	1.28
0.22-μF capacitor	Murata FG24X7R1H224KNT06 (ceramic)	DK 445-173377-1-ND	2	0.28	0.56
10-Ω resistor	Yageo SQP10AJB-10R (10 W)	DK 10W-10-ND	2	0.82	1.64
6.2-Ω resistor	Yageo SQP10AJB-6R2 (10 W)	DK 6.2W-10-ND	2	0.82	1.64
terminal block	Phoenix 1935161 (2 position)	DK 277-1667-ND	6	0.78	4.68
PCB	custom	available from IEEE	2	2.00	4.00
Total					24.38

**3. Miscellaneous**
item	Description	cost
Wood panels	Approximately 5 sq. ft. of 1/2-in thick medium-density fiber (MDF), cut into 6 panels for the enclosures. These are supplied by IEEE and will come precut and predrilled. If you want to do the cutting and drilling (assuming you have proper tools), one 2'x4' panel is more than enough for a set of speakers.	7.50
Wood glue	A couple of ounces of standard wood glue. Supplied by IEEE. If you want to buy your own bottle, something similar to this is good.	0.50
Speaker wire	Approximately 3 1-ft lengths of 16 gauge wire for internal connections. Also supplied by IEEE. If you want your own spool of speaker wire, this is one good option from Parts Express. Speaker wire is also available from any big box store or Amazon.	1.00
Screws	#6 x 3/4" screws – 24 total. Supplied by IEEE. (Parts Express sells a bag of 25 – 081-423 – for $1.79. Also available at any hardware store.)	1.00
Total		$10.00

Total cost

Using Carmody cross-overs: $156.05. About $20 cheaper than the kit sold by Parts-Express, once the cost of binding posts is added to their kit.
Using economy cross-overs: $118.77.

The economy cross-overs save almost $40.

Note that sales taxes, tariffs, and shipping charges will push the total up in usual the fashion. The good news is that IEEE prices for the kits will be somewhat lower due purchasing in volume, which comes with discounts.

Finishing touchs and a few options

You will probably want to give your speakers a nice exterior finish. If so, you will need to a few extra things. These are available in many forms from big-box store or Amazon. The specific items linked are merely suggestions.

Possibly some wood filler to close up any gaps and fix surface imperfections — something like this. You will probably need only a small amount, so you can share it with your friends or save it for your next speaker project.
Sand paper to smooth the surface. One good pass with 80 grit might be sufficient, but you might consider adding a second pass with finer grit (120 or 180) for a really smooth finish.
Your choice of surface covering — paint, wrap, or whatever.

You could use a better quality of wood for the enclosure. Using something like oak or birch plywood would allow for staining rather than painting. Obviously, you would have to acquire and cut the panels and drill the holes yourself.

There are other options for external connections. Parts Express has many variations of basic bindings posts.

I have used these — they are perfectly fine.
Or you could use a terminal cup to get a more flush back surface. (This would require cutting an extra hole.)
I also like Neutrik connectors, which make for easier plugging/unplugging. These require two pieces — a panel mount that goes on the back of the speaker and the mating connector that goes on end of the speaker cable.

Finally, you might consider adding some damping to the interior to try to improve the sound, either Polyfill or fiber mat.