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Thread: Questions regarding building a test board for working on crossovers

  1. #1
    Junior Member
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    Jun 2019
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    Phoenix, AZ
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    Questions regarding building a test board for working on crossovers

    I am going to rebuild the crossovers on 3 sets of speakers. 604c in 6.9 cubic foot cabinets, lancer 77, and a heathkit as37a with 2x6 jensen horn and an 8in jensen woofer. I've never done this before, so I've been reading for a few days and I have the The Loudspeaker Design Cookbook by Vance Dickason 5th ed. I'm going to use 3 different qualities of capacitors: dayton polypro audio grade, mundorf evo al oil, and jantzen superior zcaps. I will initially leave all coils as is, except for the heathkit which only had a capacitor in series with the pot being used as a varible resistor, so that the pot was changing the crossover freq. So that one I'll be building from scratch. I found the crossover freq for the Jensen configuration with alnico drivers, but mine are ceramic drivers (at least on the woofer), so hopefully that freq will work no guarantees there. I'll use cheap caps on the two lesser sets and a combination of the two 15-30 dollar caps on the 604c's. And cheap caps for testing. And I'm going to buy a series of silver mica small caps for bypassing. That way I can sub in different values and see if one works better. They are only a buck a piece.

    I'm going to buy a series of dayton caps (2ea) from 0.22uF to a bit beyond 3.3uF. All of them. Then I can order caps about 2uF less than what would be expected and patch in from the series (in parallel), and see what sounds best. So I will have a partial capacitor, shown in the diag below as Cp1 and Cp2, and also test capacitors, shown below as Ct1 and Ct2. I drew out the test board just to try and visualize what mounting, attaching and connecting hardware I will need for this test board. I think only the 604c will have 2 caps (4 with the parallel setup).

    Name:  xoTestBrd31.jpg
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    Here's my questions: I'd like to have test posts as shown with stars. It would be nice for this post to have both lug termination and ...like a speaker termination. That way the wiring from the partial cap and the wiring to the input and load can all be hard wired with forked lugs, and then I can slip the test caps in and out of the speaker termination points on these test posts. Is such a post available? Is this even feasible? Please show me an image of your test board and tell me the names of the hardware you use for terminations, mounting etc. I saw a couple wiring posts on partsexpress today. I need to look more tomorrow.

    I had presumed to use plywood for the board. I saw a category for capacitor straps somewhere. I'll be ordering a dozen or so of those. How do you fasten an inductor? Would braided mason's line work, or would that be a fire hazard? I have some tiewraps with an eye on the end, but again, they could melt.

    Mike in Phoenix

  2. #2
    Junior Member
    Join Date
    Jun 2019
    Location
    Phoenix, AZ
    Posts
    4

    binding posts for test mounting of capacitors and resistors

    For the text posts for capacitors and resistors, the best idea I have so far is the speaker binding post, cinch 111-2223-001 $3.57ea, from Mouser. With it's .438in threads I would have to install a thin insulating plastic mounting plate. Odd that it doesn't come with a second nut for binding ring lugs. I will continue to search for a better option, and look for a mounting plate. Please let me know if the use of this type of hardware would introduce impedance that could mess with the audio in a way some other connecting method would not, say alligator clips. I think I'll get 12 of these posts.

    Mike

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