dB 717R	Back to Speakers
The dB1661 was the home theater surround speaker which I designed to go with my dB616TL mains and dB 616TLC center channel. I now use them as side wall surrounds and developed the dB717R for use as the rear channels in my 7.1 surround system. Except for the dB1661s, all the other speakers have been upgraded to use the Dayton RS-180 7" woofer and either the Dayton RS28 or Vifa D25AG-35-06 tweeter. This speaker is designed to be mounted near the ceiling on the theater's rear wall. I wanted it to be as shallow front to rear as possible and to have a sloped baffle that would place the listeners closer to being on-axis.
The crossover is the same as the dB717TL. This is the crossover designed for the dB717TL version with the RS28 tweeter. I elected to go with it using the Vifa tweeter temporarily until I can get another pair of RS28s ordered.
Here's a pic of the crossover. I did it on a piece of 8" x 4 3/4" ply so it would fit into the box through one of the woofer holes. I made it smaller than the dB717TL board because the shallow box doesn't all as much room to shove the crossover through the woofer hole and then turn it. It's a pretty tight squeeze with all the components but it worked OK.
This is a BassBox simulation of the enclosure. The net volume is 0.5 cu.ft. (~14 liters). F3 is 83 Hz. The upper curve includes 3dB/octave in-room gain starting at 150 Hz. Qtc is 0.70 when moderate acoustic stuffing is used.
Here are a couple of pics of the construction. It's a very simple box except for the 12.5 degree slope in the baffle.
I made the front baffle slightly oversize and after the rear, sides, top and bottom were assembled, I cut it to fit. I did this because I wasn't able to use my normal router trimming method on the angled corners.  I rounded all edges with a 1/4" roundover bit. A little bondo and sanding and they're ready for paint.
If you cut the sides first then you can use them to cut the top and bottom so they are exactly flush so that the front and rear baffles lay flat.
There is one 2" x 2" brace located near the center of the baffle. Cut one end of a piece of stock 12.5 degrees then cut the square end slightly oversize and trim it until the brace fits with the top just at the bottom of the tweeter cutout. You can see the approximate location in this pic. I painted the enclosures with one coat of acrylic latex primer (which I had tinted gray) and two coats of flat black latex. Applied with a roller, they actually came out looking pretty good. Stuff the boxes with 10 to 12 ounces of poly-fil pillow stuffing or fiberglass.
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 1/2 10.00 10.00 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 (004-1) 1 ohm non-ind. 1 1.25 1.25 Rp (004-8) 8 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 $169.71 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.
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