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dB717C
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Back to Speakers
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This is a center channel speaker using the same shielded drivers as the
dB717TLC transmission line speaker but in a sealed enclosure. The enclosure provides a bass response to 77 Hz and
is slightly oversized at Qtc = 0.63.
(This speaker can also be done as an upgrade to the dB616C and with the RS180S woofers will provide a Qtc of 0.70
and an F3 of 83 Hz. The F3 with the dB616C enclosure is slightly higher, but still nearly perfect for home theater
systems with bass management at 80 Hz.) |
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Page updated 7/4/05
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There are two versions.
Shown first below is the version using the SEAS 27TDFC/TV shielded fabric dome tweeter. This is an outstanding
tweeter and is a tremendous value for the money.
Second is the version with the RS28AS shielded aluminum dome tweeter. This is a very high performace tweeter and
still a bargain when price-compared to tweeters in this performace range.
Please note that I haven't built a prototype of this speaker. The crossover design is from the dB717TLC. The sound
should be similar but there will be minor differences in the bass response and slight variations in the upper midrange
due to the baffle design. I would not anticipate making any changes because of these differences though |
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Dayton RS180S-8
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Dayton RS28AS-4
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SEAS 27TDFC/TV
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| The crossover is identical to the crossover which was optimized for the
27TDFC/TV version of the dB717TL. |
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| This is the crossover for the RS28 version which is the same as that designed
for the dB717TLC transmission line center channel. Note reversed polarity connection for tweeter. |
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| Basically, simple construction using 3/4" MDF. There is a 1" dowel
brace between the front and rear baffles. Acoustic foam or fiberglass should be placed on the inside rear of the
enclosure then the box should be lightly filled with acoustic stuffing. |
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| This is a BassBox simulation of the enclosure. The net volume is 0.7 cu.ft.
(~20 liters). F3 is 77 Hz. The upper curve includes 3dB/octave in-room gain starting at 150 Hz. Qtc is 0.63 when
moderate acoustic stuffing is used. |
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| Here is a parts list. This one is for the SEAS tweeter. The RS28 version
is below. |
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Parts and Cost for One Speaker -- SEAS Version
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Item
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Quantity
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Cost/Each
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Price
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| Dayton RS180S-8 7" Woofer |
2
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$30.74
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$61.48
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| Seas 27TDFC/TV Tweeter |
1
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27.50
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27.50
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| 3/4" MDF, 4' by 8' Sheet |
1
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20.00
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20.00
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| Polyfil Stuffing, 20 Ounce Bag |
1
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2.89
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2.89
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| Terminal Cup |
1
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3.95
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3.95
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| Crossover Parts (Parts Express part number) |
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C1 (027-426) 8.2 uF
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1
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2.75
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2.75
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C2 (027-432) 15 uF
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1
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4.10
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4.10
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C3 (027-350) 33 uF
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1
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.85
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.85
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C3b (027-424) 6.8 uF
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1
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2.25
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2.25
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Ce (027-427) 6.2 uF
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1
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2.15
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2.15
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Cz (027-432) 15 uF
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1
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4.10
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4.10
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Cn (027-348) 22 uF
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1
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.75
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.75
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Cnb (027-424) 6.8 uF
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1
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2.25
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2.25
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L1 (255-216) 0.27 mH
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1
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2.34
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2.34
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L2 (255-246) 0.9 mH
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1
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3.39
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3.39
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L3 (255-244) 0.4 mH
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1
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2.58
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2.58
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Ln (255-242) 0.8 mH
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1
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3.22
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3.22
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R1 (005-3) 3 ohm non-ind.
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1
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3.50
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3.50
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R2 (005-15) 15 ohm, non-ind.
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1
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3.50
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3.50
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Re (004-1) 1 ohm, non-ind.
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1
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.98
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.98
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Rz (004-4) 4 ohm, non-ind.
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1
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1.25
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1.25
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Rs (004-2) 2 ohm, non-ind.
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1
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.98
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.98
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Rp (004-20) 20 ohm, non-ind.
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1
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1.25
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1.25
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Rn (004-6) 6 ohm, non-ind.
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1
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1.25
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1.25
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| Grille Cloth |
1/2 Yard
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7.50
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3.75
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| Grille Guides, Small |
8
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1.90
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1.90
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| Glue |
1/2 Bottle
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4.00
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2.00
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Total
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$166.91
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Notes:
C3 and C3b paralleled = 39.8 ohms to meet 40 ohm value.
Cn and Cnb paralleled = 28.8 ohms to meet 30 ohm value. |
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| Here is the parts list for the RS28 version. |
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Parts and Cost for One Speaker -- RS28 Version
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Item
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Quantity
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Cost/Each
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Price
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| Dayton RS180S-8 7" Woofer |
2
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$30.74
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$61.48
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| Dayton RS28AS-4 |
1
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49.45
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49.45
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| 3/4" MDF, 4' by 8' Sheet |
1
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20.00
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20.00
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| Polyfil Stuffing, 20 Ounce Bag |
1
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2.89
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2.89
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| Terminal Cup |
1
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3.95
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3.95
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| Crossover Parts (Parts Express part numbers) |
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C1 (027-428) 10.0 uF
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1
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3.15
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3.15
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C2 (027-432) 15.0 uF
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1
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4.10
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4.10
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C3 (027-352) 47.0 uF (NPE)
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1
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.90
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.90
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C4 (027-350) 33.0 uF (NPE)
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1
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.85
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.85
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C5 (027-418) 3.0 uF
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1
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1.67
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1.67
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Cx (027-418) 3.0 uF
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1
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1.67
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1.67
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Cz (027-348) 22.0 uF (NPE)
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1
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.75
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.75
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Cn (027-414) 2.0 uF
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1
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1.52
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1.52
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L1 (255-216) 0.27 mH
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1
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2.34
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2.34
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L2 (255-234) 0.6 mH
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1
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3.02
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3.02
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L3 (255-260) 1.5 mH
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1
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4.47
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4.47
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L4 (255-234) 0.6 mH
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1
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3.02
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3.02
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Ln (255-202) 0.1 mH
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1
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1.83
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1.83
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Rs (004-2) 2 ohm non-ind.
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1
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1.25
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1.25
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Rp (004-6) 8 ohm, non-ind.
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1
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1.25
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1.25
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Rx (004-2) 6 ohm, non-ind.
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1
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1.25
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1.25
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Rn (004-4) 4 ohm, non-ind.
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1
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1.25
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1.25
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| Grille Cloth |
1/2 Yard
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7.50
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3.75
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| Grille Guides, Small |
8
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1.90
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1.90
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| Glue |
1/2 Bottle
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4.00
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2.00
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Total
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$179.71
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Notes:
Non-polarized electrolytic caps (NPE) may be upgraded or bypassed with film and foil or metallized poly propylene
caps. If you use bypass caps, parallel the NPE cap with a value of approximately 0.1 percent of the NPE. Upgrading
caps can get expensive. For example, C1 (10 uF) is $3.15 for the Dayton poly versus $43.13 for an AudioCap Theta.
I leave this up to you!
I don't recommend changing inductors to larger wire gauges. The inductors used in the design are 18 ga. and their
resistance (DCR) has been taken into account and used to make the speaker's response what it is. |
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