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The 10 Hz greater
bass extension offered by the FE 127 led me to use it in the next project. I was
able to just make a slightly larger baffle ring and again use 4" ABS pipe components.
Of course I popped the new heads on the too short 107 lines, yup, modest bass gain
but the increased efficiency was immediately obvious.
I was now in line tuning hog heaven. Longer pipes gave greater extension and stuffing
was not so good for extending bass but best suited for tuning out unwanted liveliness
or coloration. One point; I found these narrow pipes easily killed with over stuffing.
The sound… finally bass. Good honest string bass tapering off in the foot pedal notes
of Jimmy Smith's Hammond B3. The high end reveals the 127's Achilles heel, an overly
bright and sibilant treble (EQ and/or off axis aim makes this livable). Best configuration
to date is 1.2 m of pipe, fiberfill quilt batting covering the tapered 2x4, dense
stuffing in the elbow and light stuffing in the top 20cm of the line
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12/06/02 |
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The Boomtubes are perhaps
the absolutely worst configuration for baffle step
loss. I have now tried b-step filters and now recommend them for use on
the ABS tubes I've built.
I found a formula:
Inductor Value in mh = Baffle Width in meters * Driver Impedance / 1.021
which I took on faith and and came up with a 1.5mh inductor value for the
Boomtubes. This was combined with an 8ohm resistor in parallel for 6db of
attenuation.
I didn't have room inside the Boomtubes for the resulting filter so I used
two 2in. ABS hubcaps connected with a 1.5in. length of 2in. ABS pipe to form a small
project box (hockey puck) which I have velcro-ed to the ABS elbow of the speakerhead.
I was able to cram a 14ga. Madisound inductor and 10w 8ohm Eagle resistor into the
little hockey puck. Connections are 1 speaker binding post for input and a pig wire
to connect to the speaker terminal proper.
Sound: Big surprise for me most of the improvement seems to be in the mid-range.
Bob Marley's vocals struck me as submerged on the One Love CD, now he sounds as if
he has finally stepped up to the mike. Full range shout is much reduced, only very
bad mixes induce the turn-it-down reflex. The FE 127 is still bright; however it
now merely seems super-accurate as opposed to sibilant and strident. Overall volume
levels can be increased revealing much more program material especially in the mid
bass. I'm very happy. |
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