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Built first sub. Need some help figuring out what options on amp panel mean.

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  • Built first sub. Need some help figuring out what options on amp panel mean.

    my friend and i just finished building our first sub. we're trying to understand what all of the settings mean. we're also getting some rattle at certain frequencies and we're trying to figure out how to resolve it. going to use a frequency generator this weekend to try and narrow it down.
    Attached Files

  • #2
    Plan? Amp? Driver? Box volume? If there's a port, specifics? What are your L/R/mains? Music or HT?

    Not much there really. You set volume, and freq. below which you want to hear the sub.

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    • #3
      Turn the volume to less than the half way point. Maybe 1/3rd. Turn the frequency to a low setting., like 60hz. Play music that you like, and are familiar with, and make small adjustments to the volume adjustment, until you can just barely hear that the sub is contributing. Keep an eye on how much the subwoofer cone is moving. Should be less than 1/4 inch peak to peak usually. After a few minutes, try switching the phase switch, and see if you prefer it over the previous phase setting.

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      • #4
        Originally posted by Chris Roemer View Post
        Plan? Amp? Driver? Box volume? If there's a port, specifics? What are your L/R/mains? Music or HT?

        Not much there really. You set volume, and freq. below which you want to hear the sub.
        we're new to all of this, but we followed the specs for the sub and added in the volume of the plate amp with CAD. the driver is a dayton audio SD315-88 and the plate amp is a foster WF-100K.

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        • #5
          So you've got Dayton's 12" DVC sub (a VERY high value driver IMO) in a ported box, maybe 2.5-3 cu.ft. ?

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          • #6
            Originally posted by Chris Roemer View Post
            So you've got Dayton's 12" DVC sub (a VERY high value driver IMO) in a ported box, maybe 2.5-3 cu.ft. ?
            actually the box is sealed.

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            • #7
              we don't have a backplate or spring washers on the plate amp screws. should we add both of these? if so, do you know a source for backplates? only ones i've found online are these. 1/4″ thick laser etched acrylic. i just found these as well. i suppose we could try to design one on our own and use a service like ponoko to source the plate.

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              • #8
                So, unless that amp has built-in "boost" (which I haven't read that it does), you're looking at an F3 in the 50-60Hz range.
                Why don't you (finally) tell us the (internal) volume of the box. WHO's "plan" is this, can't you tell us?

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                • #9
                  Here is the FAQ on that Foster Sub amp from Hidley's old site.

                  FYI
                  - The amp is rated at 115W into 8 ohms
                  - I have Hidley's 2nd order XLS calculator and would be happy to email it to anyone if needed.

                  ********************************
                  Foster WF-100k FAQ


                  *** Major revisions make on 5/3/09 ***

                  How do I remove the spectral tilt that is in the frequency response?

                  See the file “WF-100k FR with VR603 adjustments.pdf” posted on the website. This file has frequency response curves with VR603 adjusted to various positions. VR603 is located on the power amplifier PCB. This file shows how the amount of spectral tilt, and overall gain, changes with the adjustment of VR603. As shipped, the position of VR603 gives the amplifier a frequency response shown in the file “WF-100k frequency response.pdf”. When VR603 is turned fully counter clockwise, the spectral tilt is almost completely removed. If you want the spectral tilt 100% gone, you will need to jumper a 10k resistor across pin 1 and 3 of VR603.

                  Once the spectral tilt has been adjusted out of the frequency response, the amplifier has a 3rd order (18dB/octave) HP response with a Q of 0.707 and a corner frequency of 29Hz. Note that the spectral tilt portion of the amplifier circuitry is NOT in the posted schematic. If I can find a 100% accurate schematic for the amplifier, I will post it. DO NOT ask me for one.

                  How do I change the high pass (HP) filter/bass boost or frequency

                  Open the link on the sale site labeled “2nd order HP filter calculator.xls”. This spreadsheet should open in Excel. If it doesn’t when you click on it, you will have to right click on the link, select “Save As”, save the file to your hard drive and open it with Excel manually. The instructions in the spreadsheet should be self explanatory on how to calculate the value of the new resistor values. Replacement resistors can be 1/8 or ¼ watt sizes. It won’t make any difference. The ¼ watt models may need to be stood up on end to fit on the PCB.

                  Remove the four screws located near the corners of the amplifier plate. There is no need to remove any of the other screws on the amplifier plate. Pull the bucket off slowly. You will need to unplug the speaker wires from the connector on the PCB. Locate the PCB with the volume control, it contains the resistors that need to be changed, R617 and R618.

                  Clip the body of the resistors at both ends, so they fall off the PCB, from the component side of the PCB. Unsolder the leads from the sold side. Pull the leads through the PCB from the component side of the PCB. This will keep you from accidently lifting one of the solder pads off of the PCB. Clean the hole with a desoldering pump or solder wick. Install the new resistors. Solder them in place.

                  Refer to any Chiltons manual for reassembly instructions

                  Comment


                  • djg
                    djg commented
                    Editing a comment
                    Chilton's: "Assembly is the reverse of disassembly".

                • #10
                  Everyone,

                  Thank you so much for the help so far! This has been quite the undertaking and I feel like finishing the construction of the sub was just the beginning! I wasn't able to "let 'er rip" yet and use a frequency generator as many of you have suggested in order to find out what frequency might be causing the rattle, but I'll be able to today and tomorrow.

                  I did some general research on crossover frequencies and got a pretty good estimate of what frequency my two front speakers should be set at and what the sub should be set at. I could've just used the auto-setup on the Onkyo TX-SR606 that I'm using with my setup and I still may, but I wanted to get an understanding of what the variables actually mean and the methodology involved in figuring them out. I'll post an update with my findings later today or tomorrow!


                  CokewithLime

                  I do have that FAQ, but unfortunately it may as well be written in Chinese. I'm still very much an amateur at DIY audio and don't understand the gist of the document. Does removing spectral tilt improve the sound? Should I be making the changes mentioned in the document? If so, my friend and I will get on top of making those modifications. Would you shoot me a copy of that calculator? I know I have it somewhere but can't remember where I saved it!

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                  • #11
                    Originally posted by KMPLSV View Post
                    I do have that FAQ, but unfortunately it may as well be written in Chinese. I'm still very much an amateur at DIY audio and don't understand the gist of the document. Does removing spectral tilt improve the sound? Should I be making the changes mentioned in the document? If so, my friend and I will get on top of making those modifications. Would you shoot me a copy of that calculator? I know I have it somewhere but can't remember where I saved it!
                    I can't post a XLS file on the forum and from your reply it appears that you don't have enough experience, at this point, to disassemble the Foster amp and make internal electronic component changes that would be required to implement the 2nd order boost filter that the XLS calculator provides.

                    IMHO - you are safest, at this point in time, to just leave the internals of the Foster amp alone and concentrate on tuning the enclosure ;)
                    Last edited by CokewithLime; 06-29-2020, 11:24 AM.

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                    • #12
                      CokewithLime

                      The friend that is working with me has more than enough technical know-how to make the necessary changes.

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