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Helium - a true micromonitor

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  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    These are the caps I bought at Ace Electronics in Houston to replace the Dynavox 4 μF caps that were actually 8 μF.

    Click image for larger version

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    I suppose they'll be alright but do you think I should plan on replacing them with either the PE NPE caps that are 4 μF and 100 V or the PE poly caps?

    Leave a comment:


  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    Paypal is the only payment option.

    Leave a comment:


  • johnnyrichards
    replied
    Re: Helium - a true micromonitor

    Cool - looks like they got their shopping cart woes under control. Interesting company.

    Leave a comment:


  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    I placed my order on a weekend and they shipped it out on Monday or Tuesday. I opted for first class postal service and it took almost two weeks to arrive.
    Attached Files

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  • johnnyrichards
    replied
    Re: Helium - a true micromonitor

    How is the ordering process through Dynavox? A few years ago I tried to order something, and it calculated $100 in shipping or something. Curious to try some of their stuff...

    Leave a comment:


  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    Andy, look back at Post #47. Scott said he didn't use any damping material but he is interested in hearing from folks who try it. I'm getting ready to start and I'll post pictures as I go. To deal with the small spaces I plan to not make crossover boards. Just glue the inductors to the cabinet walls on the inside corners, and then wire the caps and resistors in line. I've got the smaller wire-wound resistors and plan to use just one 2-ohm and one 15-ohm in each cabinet. Likewise I've got small 2 μF and 3.9 μF caps.

    Scott, thanks for measuring those cap values. I picked up some 3.9 μF NPE caps today at a local parts store. Weird that the Dynavox cap values are so scattered. I guess they're selling factory seconds at bargain basement prices, so you take your chances when you buy from them. I'll update this post if I get a response from them.

    Leave a comment:


  • andykriech
    replied
    Re: Helium - a true micromonitor

    Scott, did you put any damping material in your boxes?
    I, for one, would love to see a pic of the box innards (I am building mine now and with the boxes mostly glued up, see how really small they are for all this stuff (specially the ports...).
    Thanks, Andy.

    Leave a comment:


  • scottsehlin
    replied
    Re: Helium - a true micromonitor

    I bought 10 of the 4 uF capacitors from Dynavox. 2 are in my speakers, so there were 8 available to measure. 6 of the 8 measured in a nice tight band between 4.25 and 4.39 uF on my Centech DMM courtesy of Harbor Freight. I tried a couple of tighter tolerance caps from Mundorf and Wonder, and they also measured a little high, so I would consider those 6 caps well within tolerance. One of the Dynavox caps measured 4.05 uF, which in reality is probably a little low, but still in the ballpark. I did find one outlier that measured 2.31 uF - so approximately half of what it should have.

    My conclusions:

    The 4 uF caps aren't mislabeled 8 uF caps in general.
    There is the potential for outliers; so if you use these, make sure you have some way to check them. This is what I used.

    http://www.harborfreight.com/ac-dc-d...ter-37772.html

    Leave a comment:


  • scottsehlin
    replied
    Re: Helium - a true micromonitor

    I will check mine this weekend and report back.

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  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    Originally posted by scottsehlin View Post
    You can also get the 4 uF capacitor and a terminal cup from Dynavox.
    Did you happen to measure yours before you installed them? I received the inductors and caps today. The 2 μF capacitors and the 1.0 mH inductors measured just fine (measured a DCR of 0.8 Ω on the inductors, by the way).

    But the 4 μF caps actually measured to be 8 μF.

    I have notified Dynavox.

    Leave a comment:


  • Naught1
    replied
    Re: Helium - a true micromonitor

    Originally posted by scottsehlin View Post
    ... or one could start with a 1" hole and file out until the tube fits.
    That's what I had to do, but I used a dremel tool with a sanding tube. It took a very light touch in order not to make it too big.

    I think that in general, pipes and conduit are purposely sized to be between common tool sizes, so it's easy to pass them through materials.

    Leave a comment:


  • scottsehlin
    replied
    Re: Helium - a true micromonitor

    http://www.amazon.com/Mibro-460271-C...le+hole+cutter

    I used something like this in a drill press. Herman's method sounds good, or one could start with a 1" hole and file out until the tube fits.

    Leave a comment:


  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    If you have a router you can cut the hole any size you want. If you're using a drill one option is to drill the hole too small and then file out material to make it the right size. Another option, and this is my choice, is to drill the hole too large, but not all the way through. Then use an epoxy filler to cement the pipe in place. After it dries drill a small hole all the way through from the other side, and then cut away the remaining material with either hand tools or a router. Using a round over bit on the router gives nice results.
    Last edited by Herman Trivilino; 12-17-2014, 02:54 PM.

    Leave a comment:


  • flyfishingnitin
    replied
    Re: Helium - a true micromonitor

    What was the secret to drilling a hole for the port? I am having a hard time finding a 1 1/6" holesaw bit or even a spade drill bit.

    Leave a comment:


  • Herman Trivilino
    replied
    Re: Helium - a true micromonitor

    Thanks, Scott, for the verification of the circuit diagram.

    I got the parts from PE the other day and was shocked to see that the tweeters are so small. I had made a cardboard mock up of the cabinet just to show Donna how small the cabinets will be. Looking at that along with the woofers I see why it's all going to be a tight fit! All this talk about room for fitting the crossover components in the cabinet got me thinking that they may make up a significant fraction of the cabinet's volume and have to be accounted for in the same way as the drivers and port tube volume are accounted for. Some calculations indicated that maybe that's not true. Scott said the cabinet volume should be in the 0.03 to 0.04 cubic foot range, and the cabinet has a volume of 77 cubic inches, or 0.045 cubic feet, so maybe it's all good. Still, that crossover has to fit in that tiny cabinet and I won't be able to figure out placement until I actually mount the drivers in the cabinets, so I'm thinking crossover construction will be the last step.

    I ordered that tiny 1.0 mH inductor, along with the caps, from Dynavox. They shipped last Tuesday and should have arrived here in Texas by now. I'm getting worried.

    The 5% tolerance resistors from PE are smaller than their 2% audio grade resistors, so that's one way to save space. Since a 14 Ω resistor is unavailable, using 15 Ω will save space as it eliminates the need for a combination that adds up to 14 Ω and it may also eliminate the need for the 40 Ω resistor across the tweeter as Scott mentioned. I ordered the 2 μF caps from Dynavox. But if ordering from PE, I think the NPE caps are smaller, and since they don't offer a 2 μF NPE cap, it might be better to get two of the 1 μF NPE caps and put them in parallel.

    Leave a comment:

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