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The Advocate |
Page updated 4/26/06 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| My project RS 180-RS Tweeter project is called The Advocate Loudspeaker. The name is partially because I am a lawyer but mostly because my son, for whom these were designed and built, was on his high school mock trial team and was a truly gifted advocate for one his age (his senior year he was the team captain, and the team won the county competition and finished 5th of 34 teams in the State competition.) The name mainly honors him. |
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Dayton RS180S-8
Dayton RS28A-4
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| The box is 0.75 ft^3. However, tuning is done assuming an internal volume of 0.706 ft^3, so if you mess with tuning, use that for your box size in Win ISD, not .75 ft^3. 0.706 is the supposed ideal internal volume as calculated by WinISD, and I figured driver displacement and bracing would get me close to that with a .75 ft^3 cabinet. Internal dimensions are 8.5" wide by 10" deep by 15.25" high. I used those dimensions because I front ported with a commercially made 1 7/8" port. (I front ported because I was not sure where these would have to be placed in a college dorm room.) If you want to rear port you can monkey with the height and depth (I'd leave width alone), or if you want to front port but use a bigger diameter port, you will need to monkey with height. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| My final ports were 1 7/8" by 7 1/2". According to WinISD, that tunes the box to 34.4 hz and should yield an F3 of about 50.5 Hz. A 2" diameter port would need to be 8.5 inches long. Unless you put in an elbow, that does not leave you much room behind the port if you use my box dimensions. Last I knew, PE carried some 1 3/4" ports. That would equal 6.33"; call it 6 3/8" and call it good. You would likely need to buy three or maybe four of those ports, and cut and splice them. That is what I did with my ports, and it worked pretty well. I used blue masking tape to get the splice right, then covered that with exterior grade electrical tape because it sticks better. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Box construction: I laminated 5/8" particle board to my 3/4" front baffle using Titebond II, cutting the PB the right size to insert between the sides and top. I did that to try to get the box more square than I usually manage, and it worked. I also wanted to strengthen the front baffle given how heavy the woofers are. I used a 1/2" roundover bit and rounded over the inside of the woofer hole. The result of this is also that the box is a bit deeper externally than it would be too, and I liked that. I don't think you would have to increase the front baffle thickness, but I had reasons to do it and am glad I did. Link to pic of front baffle from the internal side, showing the roundover (on this and other links, you may need to cut and paste into the address box): |
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| I used what I call a "sHelf" brace, mounted between the woofer and tweeter. The reason I do this is so that I have a brace all the way across the front baffle, but have room on the rear baffle to mount the crossover board between the two legs of the sHelf brace. |
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| Here is the driver mounting information: Tweeter center = 2 1/16 from the top of the internal front that is, from the top of the piece of particle board (or, 2 13/16 from the external top). Tweeter is offset inward 3/4 from center in a mirror image for the left and right speakers. Link to pic showing the tweeter placement: |
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| Woofer center = 8 1/8 from the top of the piece of particle board (or 8
7/8 from the external top). Tweeter to woofer CTC is 5 15/16. Port center is 13 7/16 from top of piece of particle board (or 14 3/16 from the external top). Likely can cheat it upward by 1/16 or so. Woofer thru hole is 5 ¾ Tweeter thru hole is 3 ¼. |
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| I constructed a grill using ¼ hardboard and the magnets PE has for grill mounting. That is why the pic above of the finished pair does not show grill guides. The magnets are under the veneer. |
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| You will also notice the name badge I had made at a trophy shop. |
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| I also used business card stock to make a label for the rear of each speaker (with the name of my hopelessly out of date and pop-up ridden website); my wife then laminated the labels at work. I mounted them on the rear of the cabinets using double stick tape: |
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| Here's a crossover pic that, if I did things right, should label each part as it is labeled on the previously posted crossover schematic. Note the I+ is a bit of a mess because I managed to leave some stray text in, but the rest should be OK. Yes, I just soldered the female disconnect directly to the inductor lead. |
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| Finally, I have the big disclaimer in the crossover schematic because Speaker Workshop modeling showed some impedance in places below 4 ohms. My son has had no problem with them but he is using a hefty mid-70s Kenwood KR 6400 that will handle 4 ohms. Neither my relatively cheap TEAC HT receiver or my more expensive Denon HT receiver showed any problems during testing. However, I include the disclaimer because I dont want someone complaining if they build these and fry a receiver or amp. Someday I hope to take them to Mark K or Ratch Higgins for a real impedance check, but have not had the time to do that. |
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| Oh, by the way, they sound exceptional. Great detail without shrillness or tinniness, very good bass on the Kenwood receiver, and mids that I like, but I have come to conclude that I like my mids more receded than some around here do. If I werent so cheap I would build a set for my office! | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Here is the parts list. Caps are the Dayton metallized poly and the inductors are Jantzen. Note two resistors paralleled to obtain the 15 ohm value for R3. Note that L1 is listed as 15 ga., however, the prototype used an 18 ga. L3 used in the prototype was a Dayton Perfect Layer 18 ga. instead of the Jantzen since I had one on hand.. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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