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Contemplating a pretty dumb subwoofer design

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  • Contemplating a pretty dumb subwoofer design

    Hey all,
    I am in a recycling mode and would like to add a subwoofer to my desktop system. The L/R will be covered by a set of small 30-yr old marine/car 3-ways with a 4-inch midwoofer, 1.5 inch cone mid-tweeter, and 0.5 or 0.75 inch poly dome tweeter. I purchased them for installation in the back of an '82 Chevy Suburban work truck and have held on to them since. The random drivers I have on hand for the sub include the 10-inch woofer pulled from a Logitech z-5500 (TangBand WT-644f) with a single 8-ohm VC and MB Quart 8-inch shallow car sub driver (DS1-204) that was intended for a car that was sold two years ago. That one has two 4-ohm VCs. The amp is a 4 year old Yung SD300 (w/o boost).

    After some rough modeling in WinISD, I'm headed towards a single enclosure using both drivers. The MBQ 8-inch would be in a 0.75 cu ft sealed compartment and the TB 10-inch would live in a 1.2 cu ft vented compartment tuned to ~32 hz with a single 11.25 x 1-inch slot port. The MBQ VCs would be wired in series and then paralleled to the TB for a nominal 4-ohm load. With room gain, it should extend much lower than I need.

    Aside from a ~5 db higher output from the 10-inch TB and lower extension, the FR in the passband is roughly comparable for the two drivers. I can add a steep LP filter and EQ through the PC and don't expect to be playing the system at high volumes, so chuffing and Xmax are minor considerations.

    The silliness of doing this and re-using some old stuff is frankly the major attraction. I'm okay with a sub-optimal result as long as its fun. It would be much simpler to just build an optimal enclosure for the TB and call it a day, but that won't satisfy my itch. I am not expecting hifi nirvana.

    Thoughts?

    -Squib

  • #2
    The FR added here includes a steep 25hz LP filter and +6db @ 30hz EQ. This is the modeled SPL at 75 watts. The TB is in green, MBQ in red.Click image for larger version

Name:	Dual enclosure Frankensub - FR with LP and EQ.jpg
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    Attached Files

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    • #3
      Click image for larger version

Name:	Dual enclosure Frankensub - subenclosures.jpg
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      Here are the basic specs on the subenclosures for each driver
      Attached Files

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      • #4
        Cone excursion @ 75 watts with the LP filter and 30hz +6db boost. I'll have to cut that boost down and keep the volume down to avoid exceeding Xmax on the MBQ driver. I have not confirmed whether the Xmax spec is 1- or 2-way travel.

        Click image for larger version

Name:	Dual enclosure Frankensub - Excursion.jpg
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        • #5
          It's hard for US to enjoy/comment on your silliness w/out T/S parms for your drivers (EYE can't find 'em) ...

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          • #6
            Originally posted by Chris Roemer View Post
            It's hard for US to enjoy/comment on your silliness w/out T/S parms for your drivers (EYE can't find 'em) ...
            Ah yes. Apologies Chris. Here you go.

            TB WT-644f

            Click image for larger version

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            MB Quart DS1-204

            Click image for larger version

Name:	MB Quart DS1-204 TS Parameters.jpg
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ID:	1484618

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            • #7
              I don't see a problem with this plan at all. Your subs are separated and independent, electrically and acoustically, so basically recycling a couple drivers as a couple different subs running parallel on an amp. Go for it!
              Last edited by wogg; 04-02-2022, 07:36 AM. Reason: Edit for stupid phone post wrong word that made no sense
              Electronics engineer, woofer enthusiast, and musician.
              Wogg Music
              Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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              • #8
                Thanks Wogg. It would be better if I could EQ the drivers independently, but it looks like this is viable. We had some basement flooding this Spring. Cleaning up the mess forced me to confront how many half finished projects and random bits I've accumulated. I need to build something.

                ​​​​​​

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