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Yet another Overnight Sensations build

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  • Millstonemike
    replied
    You might be able to retrofit. Marry a port of the correct size inside the existing port.

    Or perhaps1 1/4" PVC may fit inside the existing port and provide nearly the exact inside diameter of the original port. Maybe set it back from the front - paint it - round over the front edge, etc. All a lot of handy work. And you'll likely need to fine sand down the outside diameter to fit in the existing port.

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  • bungelow_ed
    replied
    Word of caution, if I may, OS's work well with the port specified. Remember the KISS rule and ask yourself why you want to change Paul's design. Why mess with something that's not broken?

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  • Bugsi
    replied
    Originally posted by Dewmiester View Post
    Can you get the correct diameter, length, port and mount it inside the 1.625" port. A piece of 1.25" pvc would have the correct inside diameter, but the OD would be a little big.
    Do you have a way to turn it down about .035 per side. You could even sand it, would be a lot of sanding. I could do it if you want, I have some 1.25 laying around.
    They actually sound fine for my kids' room purposes. But your idea spurred a thought of another alternative: Ports can have a non-constant cross-section. This makes it more complicated to calculate their tuning frequency, but the idea would be that in theory, one could turn a piece of 1.25" pvc to fit the inside diameter, and then turn the *inside* of the PCV so that it's cone-shaped at least at the end that meets up near the flared opening of the existing tube, then chokes down over a short length (maybe an inch or two) to a constant smaller diameter for the rest of its length inside the speaker box. That would probably work pretty well, but it's a crap-ton of work for a very minor amount of tuning. There's around one to one-and-a-half octaves of useful audio below the tuning frequency that my existing ports tune to, and it would probably just annoy my kids anyway.

    My plan is to build another set for myself, also front-ported, but use the flared 1" diameter port tube, where a length of around 4-inches ought to be about spot-on. I just wonder if there will be audible chuffing noises from such a small diameter port.

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  • Dewmiester
    replied
    Can you get the correct diameter, length, port and mount it inside the 1.625" port. A piece of 1.25" pvc would have the correct inside diameter, but the OD would be a little big.
    Do you have a way to turn it down about .035 per side. You could even sand it, would be a lot of sanding. I could do it if you want, I have some 1.25 laying around.

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  • bungelow_ed
    replied
    Lucky kids, and now you have an excuse, uh reason, to build another pair.

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  • Bugsi
    replied
    Originally posted by bungelow_ed View Post
    Worst case, you can send them to me where they will have an honored place and frequent use.
    Thanks very much for your kind words! I'm leaning towards just letting my kids use them as-is. I originally intended to build these for myself, for my computer desktop, but the practical need for a speaker system for my kids drove me to finally construct them. I expect I will buy another kit and build another set for myself, where I may use the 260-472 port tube for front porting, and see how that goes.

    One aspect of this build I'm most pleased with was the construction of the crossover. Making an eyelet board made for a very tidy board. If I ran the speaker wires and terminal cup wires directly to the eyelets, it would have been a very clean, jumper-less design. I hope other people will feel free to make use of it. That's why I posted a full-scale layout for it. I do like the wire-terminals that I used, as it made connecting and disconnecting things easy when I used wires that were too short for the midwoofer that didn't allow me to rotate it so that the tiny print on it was vertical. I was able to quickly disconnect the midwoofer and run longer wires.

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  • bungelow_ed
    replied
    Congratulations on a very attractive pair of speakers and in devising a way to meet your fabrication and application constraints.
    I see three possible solutions, one of which should be acceptable. Build a small powered subwoofer, or just play them like you stole 'em. Play them as-is, I doubt you had any complaints until you decided they are flawed. Your kids will not likely notice the lack of lower limit bass; they are still very attractive speakers which meet your fabrication constraints. Just my 2 cents...
    Worst case, you can send them to me where they will have an honored place and frequent use.

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  • Bugsi
    replied
    Originally posted by thekorvers View Post
    If you use a larger diameter port, you need to INCREASE the length to get the same tuning!
    I apparently did not know this. I presumed if the air volume in the port was the same, it would have the same tuning, but that appears to not be the case.
    Looking this up now, increasing port diameter raises tuning frequency, while increasing port length lowers tuning frequency, with an equation that relates both of these and cabinet volume with tuning frequency.
    Discovering this now, I can't recommend others use the same port tubes I used for front-porting, which need to be around 8.6 inches long for the same tuning. Part 260-472 is a 1.125" diameter flared port with a 6" length that could be cut down to around 3.9 inches in length for similar tuning.
    I'm not sure what I'm going to do at this point, considering the cabinet is already cut for the 1.625" inside-diameter port.

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  • ceiol
    replied
    looks like your enclosure is tuned to about 68 Hz whereas the original Overnight Sensations are tuned to about 53 Hz

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  • thekorvers
    replied
    If you use a larger diameter port, you need to INCREASE the length to get the same tuning!

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  • Bugsi
    replied
    Originally posted by tomzarbo View Post
    Man, those ports look huge for some reason; guess I'm not used to seeing them on the front.
    You bring up a good point. You're not imagining things; the port diameters on my Overnight Sensations *are* larger than usual.

    The Overnight Sensations kit comes with a pair of part number 260-388: adjustable-length ports with a 1.375" diameter, which is to be adjusted to 6" long to tune the box to 53Hz. The volume of the air in the port is thus 𝜋*0.6875^2*6 = 8.9 cubic inches. I don't like that the included ports have a thick, flat flange extending around the port tube, as I think when front-mounting it would detract terribly from the appearance of the recessed-mounts of the Dayton tweeter and Hi-Vi midwoofer. Since I knew I'd be placing the ports on the front, and since I didn't have an appropriate sized forstner drill bit to recess the port opening, I opted for part number 260-474, which is a 1.625" diameter port with a flared opening. It is 4.875" long. To match the 8.9 cubic inch port volume of the Overnight Sensations design with the smaller diameter port tube, this larger diameter port tube should be shortened to 4.29" (cut off 0.585").

    [EDIT: See page 2 discussion. This is apparently not how port tuning works. Increasing the port diameter raises the tuning frequency, requiring lengthening the port tube to compensate and lower the tuning frequency back to the desired value.]

    As it happens, I didn't trim mine down, but now that I've worked out the math, I think that was my intention when I bought the things some time in 2016. I just forgot about that detail in the time I've had the kit sitting around waiting for me to get to it. I will likely pull the midwoofers and pop the tubes out (which I simply friction-fit into a hole in the speaker front panel) and trim them and reinstall.

    I also lightly stuffed this pair of Overnight Sensations with some loose polyfill fiber. I can tell you that the port definitely pumps air, and larger diameter ports tend to avoid chuffing noises that can plague smaller diameter ports, although I don't know how much Overnight Sensations suffer from that, if at all. Since there is a fair amount of sound that comes from the port, I feel quite happy with my decision to front-mount the ports, considering their intended location on a book shelf.

    I haven't installed the set in the kids' room yet, but we tested them out both with my home entertainment system, and with the Amazon Echo Dot and the Dayton DTA3116HP amplifier. The Echo Dot at max gain will overload the input of the DTA3116HP amp, but when dialed back a few notches on the Echo Dot, the DTA3116HP can be left at max volume with no apparent clipping. My home entertainment system with a large Pioneer surround receiver can obviously drive the speakers harder, and they definitely can go louder than the little DTA3116HP can drive them. I also drove them with the audio output of my 2014 Retina Macbook Pro 15" into the DTA3116HP amp, and the bass extension was deeper than with the Echo Dot, so the Echo Dot apparently has a slight bass frequency roll-off as a source. For home theater use I would pair these with a subwoofer. For desktop or bookshelf use I think they are fine on their own.

    That paint really did come out good. It took lots of attention to sanding the kit, spot-putty glaze to fill low areas and wood grain, more sanding, and several coats of primer with wet-sanding and glazing, before applying several coats of the Rustoleum Professional High Performance Enamel. I've been *very* happy with that paint in different colors, both flat and glossy, on different projects. For glossy finish I always follow it with Rustoleum gloss enamel and polishing. I intended to do that with these speakers, but the flat finished looked so good I decided to keep it.
    Last edited by Bugsi; 01-16-2018, 06:06 PM.

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  • tomzarbo
    replied
    Bugsi,

    they came out real nice. Love the look of the finish, the sheen is classy looking.
    Man, those ports look huge for some reason; guess I'm not used to seeing them on the front.

    Nice job on the crossover too. Have you assembled many crossovers? I've done dozens and I never seem to get mine looking that nice.
    Great job!

    TomZ

    Oh, how do the boys like them? I can only imagine!

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  • Bugsi
    replied
    Completed pair.


    They have a very impressive sound. They were very convincing in my home theater setup in place of my Klipsch SF-1 speakers. They were very transparent, with a touch of brightness, but lacked the lowest bass extension of my Klipsch SF-1's. For use in my kids' room, they will be perfect just the way they are. I'm extremely happy with these speakers.

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  • Bugsi
    replied
    Originally posted by joeybutts View Post
    Nice work. PAint looks great.
    Thanks! Rustoleum Professional High Performance Enamel is a quality product. I've been using it for years on my kids' pinewood derby cars for Cub Scouts, and with careful application, wet-sanding, enamel clearcoat, and polishing, I get finishes that rival professional automotive car paint. I was planning to clearcoat these, but I think the flat black has a beauty of its own that I really like, so for now I'm planning to leave them like this. The nice thing is that I can always change my mind, pull out the speakers, port tube, and terminal cup, and change the finish if I choose to.

    But most of the work went into the sanding, glazing putty, and priming stages. It took many cycles of glazing, sanding, wetsanding, priming, and repeating before the knock-down cabinet seams weren't visible. Attention to detail in that stage pays off. If the primed cabinet doesn't look good, the painted cabinet won't look good. The wetsanded primed cabinets looked beautiful in white. I was tempted to leave them white!

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  • joeybutts
    replied
    Nice work. PAint looks great.

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