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dB10tit Subwoofer
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Description
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I built this project and a pair of my "dB61TL" transmission line speakers for a friend here in the Sacramento
area. Her listening room is fairly large -- maybe 30' by 30' including an open stairwell and a high ceiling --
so we thought that the TLs might need some extra bass.
I designed the dB10tit around the new Dayton Titanic 10 II, a long excursion subwoofer with the potential to produce
low bass in a small vented enclosure. One drawback with drivers like the Titanic 10 II is that the port length
may have be very long when the port is made large enough to avoid port noise. However, I decided to proceed with
the project and hope that, at normal listening levels, any port noise would not be discernable. I should mention
that by "normal listening levels" I mean that the sub id set to provide a normal level of bass reinforcement
and the main speakers operating within an undistorted volume range. Using this criteria, I was able to use ports
that would fit inside the enclosure. Note that this design uses four 1 1/2" diameter ports which have the
same cross-sectional area as one 3" diameter port.
Now, if you operate the sub by itself, like I did during testing with a signal generator at Fb and below, you can
definitely make the ports huff and puff. You can also drive it well beyond Xmax. But, like I said, if you control
the level with the main speakers playing music, you shouldn't hear any port chuffing.
The amplifier used for this project is the Dayton 300-793 250 Watt subwoofer amplifier (The remote controlled version
of 300-794 which is the same except the -794 has variable phase versus the -793 which only has reversible phase).
This is an excellent amp with plenty of power to drive the Dayton 295-412 Titanic II driver. This amp can be used
with and without bass boost and it works well either way. Parts Express may be shipping units with bass boost disabled
now -- I suggest you use it either way. One nice thing about this amp is that it is self-sealing. All you need
to do is cut an opening and mount the amp. |
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| Total cost for the project is about $250 to $300 depending on whether you buy the parts on sale and on what type
of finish you apply. |
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Design
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The enclosure is a vented design, 1.5 ft3 (42 Liters). It employs four 1 1/2" ports which tune it to 30Hz.
Four ports are used to work with the down-firing design -- the four smaller ports can fit in the corners of the
bottom baffle.
I planned on using 2 1/4" legs attached to the bottom, but, as you can see in the pics, I changed to a different
style base. In any case, 2" clearance provides plenty of room for air flow from the driver and ports.
A two by four brace is used to stiffen the sides.
The enclosure should be lined with 1 1/2" acoustic foam on the top and two sides or 2" fiberglass all
around. |
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Driver
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Dayton Titanic II 10" Subwoofer
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Amplifier
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Dayton 300-794/300-793 Subwoofer Amplifier
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Box Prediction
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Enclosure
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| Construction of the enclosure was from 3/4" MDF. The bottom (baffle includes four 1 7/8" holes for the
four ports and a 9 1/8" cutout for the driver. The port exits were rounded over with a 1/2" radius router
bit. The legs can be made from 2 1/2" PVC or by stacking 3 layers of 3" MDF which were cut with a hole
saw. It is strongly suggested that you add some backing to the baffle (driver mounting side) to provide additional
bite for the driver mounting screws. 3/4" blocks at the screw locations should be sufficient. |
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| Note that the cutout for the woofer is 9 1/2", but 9 3/8" might work better for a tight fit. If your
cutout is then a little too tight, you can file or router some clearance for the speaker basket's ribs which stick
out beyond the flange. Also be careful watching that the amplifier's power supply transformer stays clear of the
port tube. If you stay with the dimensions shown on the drawing, you won't have a problem. |
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| Also note that the cutout for the amplifier differs slightly (9 1/8" width) from the dimensions specified
by Parts Express. I made this change to allow a bit more clearance. Double check the amplifier mounting location
to make sure the ports won't be in the way. There's sufficient room, but if you get the amp a bit too far to the
left, the amp's transformer may hit the port. |
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| Here's a pic of the box assembled except for the top. Circular pieces of MDF slipped over ends of ports to create
flared ends can be seen. Also, the 2x4 brace. |
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The baffle with the driver cutout, not flush mounted, and the four ports which are flared with a 1/2" radius.
The notches are clearance for the speaker basket's ribs. I didn't intend to have to do this, but somehow I cut
the opening too small. But, this is actually a better way of doing it since it provides more wood for the mounting
screws.
You will definitely want to use machine screws (I think I used #10s) with T-nuts. I set the woofer in place and
drilled the mounting holes through the basket's mounting holes. That way I was sure the holes would line up --
very important if you're using T-nuts. |
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| Flared port. Ports are epoxied in place inside the 1 7/8" hole then flared using a 1/2" radius round-over
bit with bearing. Same thing with the other end of the port. Don't mount the ports though until you've done the
round-over flares on the top ends of the ports. |
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| Here are some more pics of the finished subwoofer showing the bottom. It differs from the drawing a bit.
In this case it's a removeable base. |
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Parts List
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