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dB41
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Description
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The dB41 is a small speaker designed for music and to be used with or without a subwoofer. Without a sub, the bass
output is limited, but there is sufficient bass to provide a degree of fullness in the sound, particularly if the
speakers are placed against a wall. With a subwoofer, the sound is full and dynamic. The mids and highs are clean
and there is alot of detail and very solid imaging.
These speakers can also be used in a small home theater set up for L, R and surround speakers. Even though the
tweeter is not shielded, I have placed the speakers within 4" either side of my television with no ill effects.
Similarly, dB41s can be used as computer speakers as long as 4" horizontal separation is maintained from the
monitor.
Update: There is now a shielded version of the tweeter and it is essentially a drop-in
replacement -- you can see my discussion and a comparison on the dB 616TL page here. |
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| Total cost for one speaker is about $57. |
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The Drivers
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| The woofer is a 4" design with a relatively smooth response. It works well in small vented enclosures and,
in this case, the enclosure is 0.11 ft3 net volume with a port (slot) tuned to 81Hz. The F3 point is 87Hz. The
low frequency response shows a slight rise above the tuning frequency up to around 200Hz. |
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MCM 55-1840 4" Mid/Woofer
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| The tweeter is a popular fabric dome, damped rear chamber speaker. It provides extended highs and an airy sound. |
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Dayton 275-070 1 1/8" Silk Dome Tweeter and the 275-075 shielded version
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| Here's a photo and comments by Kevin in El Paso, Texas. "Just a quick note to thank you for the great design.
I just finished up a pair (except for the finish) and they sound super. I'm not sure if I was supposed to put stuffing
in them so I put a little behind the woof. I should have bought the woofers from you a couple of years ago. They
cost about 17 bucks at MCM now. Also, the inductors are about double what they used to be. Anyway, Thanks again." |
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| And here's a follow-up and some pics of Kevin's speakers in the finished state: "They sound even better with
a little break-in time and foam instead of poly-fill behind the woofer. They are perfect for my office and in the
corner provide plenty of bottom. I even upgraded my sound card to the highly recommended M-audio Revolution to
show off my new speaks!" |
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| What a sweet, professional looking job Kevin did and it looks like a great computer workstation set up. |
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| Now on to the design and construction... |
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Crossover
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| The crossover is second order with a crossover point of approximately 3000 Hz. An L-Pad (Rp1 and Rp2) is used to
match the tweeter's output to the woofer. |
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C1 = 4.7 µF, Polypropylene, 0.006 ohms
C2 = 10 µF, Polypropylene, 0.00715 ohms
L1 = 0.6 mH, Air Core, 0.164 ohms
L2 = 2 mH, Air Core, 0.169 ohms
L-Pad: 4.50 dB
Rp1 = 6 ohms
Rp2 = 4 ohms
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Crossover Prediction
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Enclosure
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| In order to fit the woofer and tweeter on a small as possible front baffle, the tweeter face plate needs to be
modified by cutting/grinding a portion as shown in the drawing. A Dremel tool with a coarse grit sandpaper cylinder
works well if one works carefully. One caution: wait until the driver cutouts and flush mount recesses are complete
so you know how much to remove from the tweeter. |
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| Construction of the enclosure is from 3/4" MDF (except for the slot top which is 1/2" MDF). The slot
sides are formed by using pieces of 3/4" MDF cut to 5/8" thick -- the 5/8" thickness makes the slot
5/8" high. Placed inside the side walls, this forms a slot 2 1/2" wide by 5/8" high. The actual
slot is 5" long (4 1/4" plus the thickness of the front baffle). After the speaker is assembled, cut
the opening of the slot by drilling a pilot hole for a router bit with a bearing then cutting the opening using
the inside walls as a guide for the bearing to ride on. |
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Parts List
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