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The Quarks - M.O.S.D. Computer Speaker

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  • Jeff B.
    started a topic The Quarks - M.O.S.D. Computer Speaker

    The Quarks - M.O.S.D. Computer Speaker

    Introducing the Quarks
    A Microcosm of Speaker Design

    A micro desktop computer speaker
    by Jeff Bagby


    For years I have been using the cheap little plastic speakers that come with my computer, mostly because I really don’t have the desktop space for speakers like Continuums or Piccolos to sit there. Recently after transferring a couple hundred CD’s to the hard drive I decided to make something a bit nicer to sit on my desk. Since I am only 18” away they really don’t need to be real big and powerful, but I at least wanted something the sounded right when I listened to tracks or played Youtube. I have noticed a long time now that Parts Express was selling a small flatpack from Denovo Audio that would meet my needs (PN 300-7060), so I finally decided to pick up a pair.


    For drivers I really didn’t have a plan, but when Parts Express ran the Fountek FE-83 on sale for $6.90 I decided to pick up a pair. (I believe the FE-85 PN 296-717 will work in this design too). For a tweeter I pick up a pair of the press-fit Dayton ND20FA-6 tweeters (PN 275-030). Together these made a nice little attractive speaker.

    One interesting thing I found was when I measured the T/S parameters on the FE-83 was that even though the manufacturer lists the Fs at 121 Hz my sample measured at 100.3 Hz, and the Qts was a little lower than specified as well. You don’t often see drivers measuring with a lower Fs than specified so this was a welcome surprise. This led me to decide to make a vented speaker and see if I could pull a little more bass from the tiny box. I ended up using a press-in port that measured 1” x 4” (PN 260-470). This tuned the enclosure to 102 Hz and gives me good half-space bass into the mid 90’s. However, sitting on my desk there is excellent output to about 80Hz.


    For the computer speaker I decided to paint the enclosure. I looked around at different paints and settled on a Krylon textured paint in their “Stone” series called “Obsidian”. This paint turned out to have an excellent contrast with the shiny aluminum cone 3” woofer. Finally, I added little rubber bumper feet on the bottom of the enclosure.



    The crossover is a fairly simple design, because first of all, this is an inexpensive project and second, there is very little room inside this box. All of the components are pretty small. Including the woofer’s inductor where I used a surplus ferrite core inductor that I unwound to 1.0 mH. However, a standard laminate core or iron core should work just fine.



    The frequency response of this speaker is exceptionally flat, and vocals are very clean and realistic. Bass is better than you might expect give the speaker’s size and bass extension.


    And another thing that surprised me was the measured phase response , the speaker turned out to be a minimum phase design, even the Impulse Response shows a single peak revealing the perfect time relationship of the two drivers.





    The impedance is a solid 8 ohms or higher, so a lot of T-amps can drive this speaker without issue. I chose the Topping TP-21 Amplifier (PN 310-310), which works nicely for such close listening.




    So, my final thoughts? I called these the Quarks due to their really small size, certainly the smallest speakers I have ever made. I referred to them as a “Microcosm of Speaker Design” because despite their small size: assembling, finishing, measuring, voicing, etc. is just the same as it is on a larger speaker, so a small speaker doesn’t necessarily mean a small project. But, I think the speaker turned out better than I had expected. I like the look and it sounds exceptional. If I were to do it again the only thing I would change is to not use the binding posts and go with a terminal cup instead. It was really hard to get my fat little hands in that hole to connect the wires to the terminals. But that’s the only thing I would change.







    Believe it or not, after all of this time this is my first project posted in the Project Gallery. :D

    Enjoy,
    Jeff B.

  • djg
    replied
    I glued all my components to the walls. The coil I screwed to a piece of underlayment then glued that. My Quarks (Pg 11) are sealed, never to be opened again. I have had speakers 15 years old that I disassembled to sell the components. Nothing had moved at all.

    You can put the crossover on a piece of thin ply small enough to go through the woofer hole and epoxy that down.

    I don't care if you use them upside down, I'm just telling you that you don't need to.

    It's DIY, have fun.

    Leave a comment:


  • robca
    replied
    Originally posted by djg View Post
    If you make the crossover small enough to fit through the woofer hole, you won't need any access besides that. There's not much going on inside these.
    Well, one of the inductors is pretty heavy and needs securing (screws, since any glue would not hold on the paper-like MDF), plus I like glueing everything down to avoid rattling crossover components or wires over time. Would be pretty messy to try and do it from the small midwoofer hole, so I prefer to have easier access.

    More than anything I'm trying to understand what would the problem be if I were to use the speakers upside down, since that would make my plan (open back) possible

    Leave a comment:


  • djg
    replied
    If you make the crossover small enough to fit through the woofer hole, you won't need any access besides that. There's not much going on inside these.

    Leave a comment:


  • a4eaudio
    replied
    Originally posted by robca View Post
    Can anyone think of any downside doing so? I have seen quite a few two ways speakers with the tweeter at the bottom, and aside from noting they should have the tweeter at ear level, no other consideration applies.
    From what I have read, the tweeter height is the main thing.
    The other theoretical issue would be the bounce/reinforcement of the woofer being down by the surface of the desk vs further away with the speaker inverted. But with this small woofer and speaker I doubt if that is going to make any difference, and it's not clear which would be better anyway.

    Leave a comment:


  • robca
    replied
    I'm building the Quarks using the DIYSoundgroup kit. I was hoping to be able to leave the back removable and with exposed MDF (possibly painted black), and veneer the rest of the speaker. But due to the way the kit is designed, the top panel is smaller, and the back panel is exposed at the top. If I were to assemble the cabinet so that the smaller piece is at the bottom, the port would interfere with the midwoofer. I could replace the back panel and drill a new hole for the port, but I don't have woodworking tools anymore, and would probably not be worth the effort anyway (and the cost of buying MDF just for 2 tiny panels)

    One possible alternative is to use the quarks "upside down", with the tweeter at the bottom and the midwoofer at the top. I do realize that I will have to "sit them higher" so that the tweeter is at ear level (btw: I use them as a desk speaker, near field). Can anyone think of any downside doing so? I have seen quite a few two ways speakers with the tweeter at the bottom, and aside from noting they should have the tweeter at ear level, no other consideration applies

    I found some reference to change in phase, depending on the type of crossover used, but I'm afraid it completely flew above my head, and could not follow that explanation

    And, yes, the other alternative is to build them the way they are supposed to, and not have the back removable, but why make life easy when you can make it hard on yourself?

    Leave a comment:


  • dkalsi
    replied
    Click image for larger version  Name:	Quarks actual vs measured.JPG Views:	1 Size:	215.0 KB ID:	1398969 Has anyone measured their Quarks build? I built mine earlier this year and am now just getting around to taking measurements.

    I've attached an image comparing my measurements with Jeff's measurements in the first post.

    Blue = Jeff
    Red = Mine

    Leave a comment:


  • jdhill
    replied
    I posted this in another thread but I figured it would belong here as well... The MTM version! The sound is great but I don't have much of a reference having never made the originals. It was a fun build in any case.

    Leave a comment:


  • warllo
    replied
    I do, I figured that one was pretty hard to screw up :-) Thanks for the response!

    Leave a comment:


  • Jeff F.
    replied
    Originally posted by warllo View Post
    Hello everyone, this is my first speaker build that uses x-over components. Does this layout look correct for the quarks?
    Looks correct, you have the inductor for the mid as well?

    Leave a comment:


  • warllo
    replied
    I forgot to notate that the positive terminal of the tweeter would get a wire connecting to the same solder joint as the inductors negative side. The forum wouldn't allow me to edit my post for some reason.

    Leave a comment:


  • warllo
    replied
    Hello everyone, this is my first speaker build that uses x-over components. Does this layout look correct for the quarks?

    Leave a comment:


  • Jeff F.
    replied
    Originally posted by corwin6654 View Post
    That is a nice little boom box build. I’m looking to do something similar for my wife for the kitchen. Do you have plans for the box and crossovers you can post? What amp is that on the top? Sent from my iPhone using Tapatalk
    Thanks! As for plans, it's just two Quark speakers on their sides and built into one enclosure. The crossover is the same as the original as well. The amp is a Nobsound and can be found on the Zon or the Bay and has built in Bluetooth. It sounds and works well.

    Leave a comment:


  • corwin6654
    replied
    Originally posted by Jeff F. View Post
    Finished the Quark speaker yesterday. It's for my wife to use on her desk at work. She needed something small with good sound quality and Bluetooth. The sound is great for being so small and just right not being boomy to bother anyone nearby. If you see this, thanks for the design and I hope you are doing well Jeff B. I still need to clean up the wiring on the back side, but here are some pics.
    That is a nice little boom box build. I’m looking to do something similar for my wife for the kitchen. Do you have plans for the box and crossovers you can post? What amp is that on the top? Sent from my iPhone using Tapatalk

    Leave a comment:


  • Jeff F.
    replied
    Finished the Quark speaker yesterday. It's for my wife to use on her desk at work. She needed something small with good sound quality and Bluetooth. The sound is great for being so small and just right not being boomy to bother anyone nearby. If you see this, thanks for the design and I hope you are doing well Jeff B. I still need to clean up the wiring on the back side, but here are some pics.

    Leave a comment:

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