dB717TLC

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This is a center channel speaker version of the dB717TL transmission line speaker using the Dayton RS28AS-4 shielded tweeter.

This speaker can also be done as an upgrade to the dB616TLC with the use of an add-on baffle.

For pics of dB717TLCs built by other DIYers, scroll down.

 
 

 

Dayton RS28AS-4

Dayton RS180S

   
Here's the enclosure drawing showing the add-on baffle. Consult the dB616TLC page for details.

 

 

The tweeter cutout is moved up about 1/4" compared to the dB616TLC but everything fits OK. I ended up making the baffle 1/2" narrower (trimmed 1/4" off each end) so that the original baffle was revealed a bit on the sides. I cut the big curve with a jig saw then used a belt sander to smooth it.

   
This is the enclosure drawing for building the RS version from scratch without the add-on baffle. I actually prefer the add-on baffle version, but this preference is only based on aestetics.

 

   
   
The crossover is identical to the crossover which was optimized for the dB717TL with the exception of adding 3dB attenuation on the tweeter to account for anticipated on-axis listening.

 

   
This is the simulated response. As in the dB717TL, the notch filter (Ln, Cn, and Rn) may not be necessary unless your ears detect excess energy in the 10KHz range.

   
Crossover pic with the tweeter wired in reverse polarity. This is actually a dB717TL crossover.
The L-pad values are the only difference. They should be 2 and 6 ohms as the schematic shows.

   

Parts and Cost for One Speaker

Item

Quantity

Cost/Each

Price

Dayton RS180S-8 7" Woofer

2

$30.74

$61.48

Dayton RS28AS-4

1

49.45

49.45

3/4" MDF, 4' by 8' Sheet

1

20.00

20.00

Polyfil Stuffing, 20 Ounce Bag

1

2.89

2.89

Terminal Cup

1

3.95

3.95

Crossover Parts (Parts Express part numbers)  

 

 

C1 (027-428) 10.0 uF

1

3.15 

3.15 

C2 (027-432) 15.0 uF

1

4.10 

4.10 

C3 (027-352) 47.0 uF (NPE)

1

 .90

 .90

C4 (027-350) 33.0 uF (NPE)

1

.85

.85

C5 (027-418) 3.0 uF

1

1.67

1.67

Cx (027-418) 3.0 uF

1

1.67

1.67

Cz (027-348) 22.0 uF (NPE)

1

.75

.75

Cn (027-414) 2.0 uF

1

1.52

1.52

L1 (255-216) 0.27 mH

1

2.34

2.34

L2 (255-234) 0.6 mH

1

3.02

3.02

L3 (255-260) 1.5 mH

1

4.47

4.47

L4 (255-234) 0.6 mH

1

3.02

3.02

Ln (255-202) 0.1 mH

1

1.83

1.83

Rs (004-2) 2 ohm non-ind.

1

1.25

1.25

Rp (004-6) 6 ohm, non-ind.

1

1.25

1.25

Rx (004-2) 2 ohm, non-ind.

1

1.25

1.25

Rn (004-4) 4 ohm, non-ind.

1

1.25

1.25

Grille Cloth

1/2 Yard

7.50

3.75

Grille Guides, Small

8

1.90

1.90

Glue

1/2 Bottle

4.00

2.00

   

 

 

   

Total

$179.71

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.

 
   
Here is a dB717TLC built by James Beane. He used solid wood (veneered plywood with solid edge trim) top/bottom caps and wraps a grille cloth sock around the body of the speaker. James also built his surrounds using the same technique and the look is quite handsome.

   
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