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Working on some Wolf's PC speakers... Or at least Wolf-inspired.

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  • Working on some Wolf's PC speakers... Or at least Wolf-inspired.

    I probably shouldn't call them Wolf's unless Wolf approves them, because I've ended up changing almost everything from his design.

    To start with, I'm using 4-ohm NS3's instead of the 8-ohm set he uses. They cost half as much, which is nice, plus I'll be driving these from a 12v amp and wanted to get full power. The T/S parameters are apparently a bit different, but a few months ago Wolf indicated that this should be barely within parameters for his design (though it would require twice the capacitance on the filter). Because of the higher capacitance needed, no audio caps were available (or reasonably priced), so I picked up a pair of Nichicon bipolar electrolytic 1,000 uF caps from an electronics place. They were $2 each and way smaller than pairing up 500 uF Daytons.

    Then, I decided to rear-mount the driver, because I can't stand to see the squarish frame on those NS3's.

    Then, I changed the dimensions into something a little slenderer and more graceful, while keeping the enclosure volume the same. The internal width is the absolute minimum the frame can fit inside, which means I'll need to be really careful cutting the hole and mounting the driver to keep everything aligned.

    Then, I screwed up the construction. I had sketched out all my dimensions but had an arrow pointing to the front of the baffle, when it should have only referred to the depth of the side panels. As a result, I cut the thing too shallow by half an inch. Instead of 64 cubic inches, I'm going to wind up at 58 cubic inches, minus a bit more for the new driver position. WinISD doesn't think it'll matter much, but I'm still annoyed at the slip-up.

    Now that I'm done talking about my screw-ups, here's where things sit this morning. This is likely the smallest set of speakers I'll ever build, which makes them a great candidate for solid wood construction. If you start gluing solid boards together with the grain running perpendicular, as these are where the baffle meets the top and bottom, you can have serious issues with differential expansion and contraction. You can usually get away with it for a few inches, but beyond the 4.5" width of the baffle I would worry about these self-destructing once summer humidity hits. Since I think I can get away with it in this size, I decided to use up a chunk of glulam maple beam someone gave me. This is basically plywood on steroids, with the laminations running through the board instead of across it. With the black glue, it winds up looking a lot like Zebrawood, but is a lot easier to work with. I'm probably going to finish them with something clear. Maple is hard enough to dye cleanly when it's all the same board; I don't think I've got much hope of putting consistent color on this stuff.

    I'm hoping to finish these up in the next day or two, but I need to pick up a replacement router bit to rabbet the side panels to accept the back panel.
    The dimensions noted here are the CORRECT ones. I cut mine half an inch too shallow. I have almost enough clamps! Glue still needs a bit more time, then the edges need cleaned up.

  • #2
    Charles Neil blotch control may be in order for the finish. I used it on some pine step stools and it worked very well. I messed up and used the Minwax polyshade finish but absolutely no blotching.

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    • #3
      Hard Maple is a very stable wood and is used on bass and regular six string guitar necks because of the stability. The only drawback is the weight, Maple is heavy. A couple of coats of poly on all surfaces and all should be okay. They are looking great so far and I like the slimmer proportions and dislike the look of the pin cushion frame also.

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      • #4
        Progress continues. I got all the glue joints cleaned up and all the edges rounded over. I had a really hard time controlling tear-out in a few places, so I had to rebuild part of one corner with some wood filler. It'll be noticeable if you look for it, but hopefully doesn't stand out too badly.

        Maple is pretty stable, but in woodworking it's usually dangerous to think "this wood is really stable, I don't need to worry about it moving." Guitar necks are made of maple, but they still go out of tune when the humidity changes. I've calculated the expected movement at 0.025" in my air-conditioned house once summer hits, although if I let it spend a summer in the garage or storage unit it could move as much as 0.1". That latter situation still looks like a small number, but it could crack the butt joints on the cabinet. I'll try to avoid doing that.

        I played with a few finishes and colors on some scraps. I got a pretty even color with Transtint dye applied over dewaxed shellac, but I think the result was fairly bland. I'll be leaving the maple pale to capitalize on the "almost Zebrawood" appearance, and just using some wipe-on polyurethane. The first coat of that is drying right now; no pictures with finish yet, but maybe tomorrow. I do have a picture of the sanded cabinets just before finishing:

        Click image for larger version

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        Last edited by aramid; 04-27-2018, 12:07 PM.

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        • #5
          I don't doubt the Muse caps will sound nice, but I would worry about a tolerance issue. Before final assembly I would make sure one is not louder than the other at low volume.

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          • #6
            That's a fair point - I think these are only 20% tolerance. I got extras, and will be measuring them to pick the closest two.

            Edit: HAH, 20% tolerance my eye! I measured three capacitors and got 1,025 uF, 1,025 uF, and 1,028 uF.
            Last edited by aramid; 04-27-2018, 09:19 AM.

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            • #7
              Well, I got them all wrapped up this weekend!

              The drivers are held in with little hard maple tabs, because the screw holes would punch right through the bevel in the baffle and look bad. There's about a quarter-ounce of Polyfil inside; I think this might be a bit too light, but I'll listen to them for a while before I go nuts.

              The speakers are finished with six or seven coats of wipe-on polyurethane and then knocked back to a semi-gloss with paste wax and steel wool. I'd not used Minwax wipe-on poly before, and I'm not sure I'll bother again. It works just fine, but it combines the drying speed of polyurethane (slow) with the build of shellac (thin). Not a good combination.

              Because I was working with so little space, I didn't have a good way to seal the back panel. I ended up using rope caulk, which will probably set up enough that the back panel is almost impossible to remove in the future. Oh, well.

              These are being used as computer speakers, in conjunction with Carmody's Voxel sub. The two seem to complement each other nicely.

              Finally, I recently bought myself a calibrated microphone and have been playing with it - I don't know how accurate these measurements really are, but it's interesting to look at, anyway.

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              • #8
                Those look great, i have made 3 or 4 sets of Wolf's PCs so far (and I think i have the parts for 1 more set...). that looks great with the sub. Did you build the sub to match these?
                Andy.

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                • #9
                  Thanks! I planned the sub and speakers at the same time and always intended to use them together, but the sub is just painted MDF. I only had about 2 board-feet of that laminated maple someone had given me; it was just barely enough to finish the pair of speakers. I'm actually trying to find some more to make stands.

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                  • #10
                    Good job on these. How do they sound? I've only heard the sprite separates. I would be interested to pair these with a small tweeter. Being 4ohm, these would be easier to pair.

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                    • #11
                      I like the hard maple.
                      On the cheap diy. That is my motto - www.hifiposse.com

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                      • #12
                        Jake:
                        They sound pretty good out in the open, and blend really nicely with the subwoofer. It's taking me some time to get them sounding right at my computer desk, though. I need to make taller speaker stands than I had previously and need to play with the subwoofer location some more to get the whole system sounding right. Looking at how quickly the response rolls off above 7 KHz, I'd definitely like to explore adding some tweeters (and fortunately, my baffle layout leaves me room to do so). Unfortunately, I don't know much about driver selection and crossover design. I don't even know where to start.

                        Hobbyhands:
                        Thanks! The laminated lumber is interesting stuff to work with. It's essentially quarter-sawn, but the layers make it more prone to tear-out, and there are a lot of voids and through-holes where plies meet, which required using a lot of filler to get an airtight box. The black glue adds some nice visual interest, though, and it's certainly more renewable than Zebrawood or one of the other exotics with similar appearance. Unfortunately, I don't know how to find more of it! A friend gave me a small chunk of the material to play with, and I don't have a brand name or anything to go searching for more.

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                        • #13
                          Originally posted by aramid View Post
                          Jake:
                          They sound pretty good out in the open, and blend really nicely with the subwoofer. It's taking me some time to get them sounding right at my computer desk, though. I need to make taller speaker stands than I had previously and need to play with the subwoofer location some more to get the whole system sounding right. Looking at how quickly the response rolls off above 7 KHz, I'd definitely like to explore adding some tweeters (and fortunately, my baffle layout leaves me room to do so). Unfortunately, I don't know much about driver selection and crossover design. I don't even know where to start.

                          Hobbyhands:
                          Thanks! The laminated lumber is interesting stuff to work with. It's essentially quarter-sawn, but the layers make it more prone to tear-out, and there are a lot of voids and through-holes where plies meet, which required using a lot of filler to get an airtight box. The black glue adds some nice visual interest, though, and it's certainly more renewable than Zebrawood or one of the other exotics with similar appearance. Unfortunately, I don't know how to find more of it! A friend gave me a small chunk of the material to play with, and I don't have a brand name or anything to go searching for more.
                          Aramid, the simplist and cheapest tweeter addition is part #289-2300. A simple Butterworth is a 3.8uf cap in line with the positive lead. Crosses over at 7k. I'e used these paired with small drivers. They blend very well. I imagine you wouldn' even need a resistor. One thing, they are difficult to mount. They require a rear mount with sufficient roundover.

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                          • #14
                            Wow, that's cheap. I don't think I'll be able to use them, though, because my baffles aren't removable (and I'm not remaking or refinishing the boxes). I can drill a hole, and that's about it.

                            I was thinking something like the press-fit ND16FA-6 would be simple enough to integrate mechanically, although I'm still a bit uncertain about electrically. The 3.8uF capacitor still stands, but do I need a low-pass to the woofer, obviously not for response reasons but just to keep from wasting power sending it high frequencies it isn't playing anyway? Do I need to attenuate the tweeter because it's much more sensitive than the woofer, or do I need to attenuate the woofer because at 4 ohms it's going to be drawing 50% more power than the tweeter? Do I need to learn about phase shifting?

                            Like I said, I don't know much about crossover design.

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                            • #15
                              Originally posted by aramid View Post
                              Wow, that's cheap. I don't think I'll be able to use them, though, because my baffles aren't removable (and I'm not remaking or refinishing the boxes). I can drill a hole, and that's about it.

                              I was thinking something like the press-fit ND16FA-6 would be simple enough to integrate mechanically, although I'm still a bit uncertain about electrically. The 3.8uF capacitor still stands, but do I need a low-pass to the woofer, obviously not for response reasons but just to keep from wasting power sending it high frequencies it isn't playing anyway? Do I need to attenuate the tweeter because it's much more sensitive than the woofer, or do I need to attenuate the woofer because at 4 ohms it's going to be drawing 50% more power than the tweeter? Do I need to learn about phase shifting?

                              Like I said, I don't know much about crossover design.
                              You could make some sort of B&W nautilus style speaker with the tweeter mounted on the top of your box.* I was just offering a simple way to get a little sparkle up top. Yes, you could use the nd16fa, and put a high pass on the nd90, but then your getting into a whole different speaker.*

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