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The Plumber's Delight

Here are a few pictures of my latest speaker building project.  

I used the 24.5 x 72 x 1.125" workbench table top particle board they sell at Menards for $14.99 a sheet.    The finished speakers are 19 lbs each.  You might think this thickness is overkill for such a small speaker.   But what I was trying to do was to increase the mass of the speaker as much as possible to reduce self-cancellation caused by the entire speaker moving back & forth at low frequencies.     

Gross internal volume is 3 liters (5.30x3.55x9.75").  The port is 26" long with a 1.6" inside diameter.  This tunes the system to somewhere in the 40-42Hz range.  A 10" long by 1.25" inside diameter bass trap eliminates the 1st and 2nd port resonances at 260 and 520Hz.  This trap is stuffed with a small amount of Acousta-stuf and dacron material.   Tuning was done experimentally by changing the trap length and stuffing density, on the fly, as I measured the near field response with OmniMic.  

Drivers are the Tang Band W5-2053 subwoofer, the Techtonic Elements TEBM46C20N-4B midrange, and the Morel MDT-39 tweeter.  Crossover frequencies are 320 and 2400Hz.   Sensitivity measures somewhat low at 82-83dB/2.83V/1 meter.   

Because I am using a 4 ohm subwoofer and a 4 ohm midrange, the overall system impedance dips to about 3 ohms in the 90 to 150Hz range (see graph).   I have played the speakers at moderate to somewhat loud levels with a number of amplifiers and have not, as yet, had any problems with amplifier overheating or the tripping of amplifier protection circuitry.   :o

I measured total harmonic distortion at various SPL levels with OmniMic and then transferred this data to a spreadsheet (see attached).  Subwoofer distortion at 80Hz appears to be the weakest point, with midrange distortion at 300Hz a close 2nd.  When I listen to the speakers at the 86-89dB level, there is absolutely no sense of strain, but when I push them to either the 93-95 or 95-97dB levels, I can hear a very serious dynamic compression effect starting to set in.   :)   

Any comments or questions are welcome.  Thanks for looking. 

Bill


kennykNicholas_23
«1

Comments

  • Look forward to seeing and hearing them at Indy.
    ............. could you hum a few bars.
  • Woops.  The HD spreadsheet didn't come through because it was a gif file.  Changed to jpeg and uploaded.
  • Nice work Bill! I have to ask, why Particle board vs MDF?? There is so much more work involved in prepping for paint when using the Particle board. Not to mention, it flakes so easy leading to more clean up work. Just curious.
  • If I may, PB is a great choice for cabinets. It is plenty stiff, and cheap. 
    I have a signature.
  • Bill,
       That was A LOT of work! I like your port resonant trap. Do you have a Z measurement with and without? Also,  NF/port summed with and without? 

       If you have ever seen the weird shape of Vivid speakers, even the Nataulus thats what L. Dickie (the desiger) uses the cabinet shape for. That, and diffraction. It is very cool stuff as a whole and I think your exexution of dampening a port's resonance is awesome. 

    Great document package, too. 3 ohms Z for a 4 ohm speaker is no big deal. Many commercial 8 ohm speakers drop to 3.8. It is a little reactive and 80HZ looks to be a hell of a load which could account for the distortion spike as you are pulling a ton of current and back EMF will be at a maximum.  Would not be a problem with amps, just make them complain a little and by the looks of it, it is likely more of something that is measurable....Not meaningful. 

    Specially in such a tiny speaker!!!!!

    I bet they actually are stunning at regular to moderate volumes. I am very impressed with this design. 
  • There are different grades of particle board.  I like using it if I don't plan on painting the enclosures.
  • Nice work Bill! I have to ask, why Particle board vs MDF?? There is so much more work involved in prepping for paint when using the Particle board. Not to mention, it flakes so easy leading to more clean up work. Just curious.

    Thanks, Kevin.   I went with particle board because it is available in the 1-1/8" thickness verses 1/2" or 3/4" for MDF.  I cannot find 1" MDF in my area.  I would have had to glue up two 1/2" boards, but when I do this I run into problems with the boards warping when the glue dries. Even when I clamp boards in rails for a week, when I remove the clamps, I get warping.

    I do get some flaking with particle board, especially in the driver cutout holes.  But it is not too bad.  I just fill it in with bondo.   
  • Bill,
       That was A LOT of work! I like your port resonant trap. Do you have a Z measurement with and without? Also,  NF/port summed with and without? 

       If you have ever seen the weird shape of Vivid speakers, even the Nataulus thats what L. Dickie (the desiger) uses the cabinet shape for. That, and diffraction. It is very cool stuff as a whole and I think your exexution of dampening a port's resonance is awesome. 

    Great document package, too. 3 ohms Z for a 4 ohm speaker is no big deal. Many commercial 8 ohm speakers drop to 3.8. It is a little reactive and 80HZ looks to be a hell of a load which could account for the distortion spike as you are pulling a ton of current and back EMF will be at a maximum.  Would not be a problem with amps, just make them complain a little and by the looks of it, it is likely more of something that is measurable....Not meaningful. 

    Specially in such a tiny speaker!!!!!

    I bet they actually are stunning at regular to moderate volumes. I am very impressed with this design. 

    Thanks for the kind words.  They do pack a real punch for the size, which is what I was going for.   I did not measure Z with or without the traps; only NF SPL at the port exit with and without the traps. I now have the ports glued together, so I would be unable to re-measure at this point without cutting them apart.
  • Also,  outer 1/8" of stair tread rated PB is hard enough to break router bits if you ain't careful. Pissed me off a few times!!! Modern PB isn't the stuff all those Montgomery-Ward speaks used in the 70's. 
    I have a signature.
  • Cut these after work yesterday, glued up a couple of pieces last night and the rest tonight.

    jr@mackennyk4thtry
  • Bill,

    You might be able to find MDF stair tread at one on the big box building supply stores. Home Depot has them. 1-1/8 in. x 11-1/4 in. x 4 ft. MDF with a bull nose one edge which is big enough for small boxes and could be joined at the edge if you wanted bigger panels. http://diy.midwestaudio.club/discussion/272/1-1/8%20in.%20x%2011-1/4%20in.%20x%204%20ft.

    Ron
  • Wow these are great, can't wait to hear them in a few weeks, great craftsmanship!

    Javad
  • Thanks, Javad.  I saw the pictures of your dual-side-firing 6" passive radiator system.  Very impressive looking design.  Can't wait to hear them as well!

    Bill S.
    JavadS
  • Craig,  would this be a 3 liter box?
  • Ron_E said:
    Bill,

    You might be able to find MDF stair tread at one on the big box building supply stores. Home Depot has them. 1-1/8 in. x 11-1/4 in. x 4 ft. MDF with a bull nose one edge which is big enough for small boxes and could be joined at the edge if you wanted bigger panels. http://diy.midwestaudio.club/discussion/272/1-1/8%20in.%20x%2011-1/4%20in.%20x%204%20ft.

    Ron

    Thanks for the tip, Ron.   I was actually thinking about using the stair treads that you mention to build these speakers.  But I had to go with the larger benchtop material because I wanted to be able to cut the faceted baffle angles off the end of a long piece of stock.  So I first ripped the benchtop down into two 12x72 inch pieces on my table saw.  Then I sliced the baffles off the end of this long piece of stock using my dual-bevel sliding miter saw.  The stair tread material would only have allowed me to build the box about 11 inches high. 

    Bill   
  • 4thtry said:
    Craig,  would this be a 3 liter box?
    Hi Bill, no 4 Liters...  not for Ben's shootout.
  • PWRRYD said:
    4thtry said:
    Craig,  would this be a 3 liter box?
    Hi Bill, no 4 Liters...  not for Ben's shootout.

    You could cut a liter off like I did. ;)
    Mzisserson4thtryS7910
    ............. could you hum a few bars.
  • PWRRYD said:
    4thtry said:
    Craig,  would this be a 3 liter box?
    Hi Bill, no 4 Liters...  not for Ben's shootout.
    Aw, Ben will not be happy. You no like Nen when Ben not happy. 
    kennykNicholas_23
  • Does he turn green
    Mzisserson
  • Yup, with big pointy teeth, ouch, bite, bite!!
    Creative paint job, Bill
  • 6thplanet said:
    Yup, with big pointy teeth, ouch, bite, bite!!
    Creative paint job, Bill
    Thanks, Eric.  Just using up some old rattle cans and masking tape.  The concept is frame within a frame in burgandy and gold.  The burgandy dryed fast, but I got several thumb and finger prints on the gold by touching it too soon.  I tried to buff out the prints, but buffing dulled the finish.  May have to re-paint after Indy.

    Bill
  • Bill, I like to close my eyes while listening. They will be as beautiful as they may sound.  ;)
    4thtry
    ............. could you hum a few bars.
  • Did I catch this right? These took 1st? Well done! 
  • edited April 2017
    I was blown away. Bill did a fabulous.....simply fabulous job.
    PS. I didn't close my eyes. :3
    Mzisserson4thtry
    ............. could you hum a few bars.
  • Thanks you!   I went up against a powerful contender (Javad) in the first round.  But the votes luckily went in my favor and when the dust cleared after the 2nd round, I came out on top.  There were quite a few good contenders, but I think I got the edge because my entry dug just a little bit deeper than the rest.

    Bill S
    JavadS
  • And here are just a few pics from the show:
    kennykMzisserson
  • The last pic of (you?) Holding it is funny, like my 4yo coming up to me with a bunch of stuck together legis saying "I made this!"
  • That's Wolf lol
  • No, that is Ben (Wolf), the organizer of the show.  All of the Nanotech speakers were placed up front on the head table.  Then Ben & Chuck quickly swapped out speakers in predetermined groupings.  This helped reduce the down time between speaker swapouts.

    When Ben picked up my speaker to put it on the stand, he first waved it to the crowd and there was a slight uproar of laughter in the crowd.  As a photographer, whenever I hear laughter in the crowd,  I quickly raise my camera and fire as fast as I can.  This pic was the result.

    Bill
  • Awesome job Bill, so many parts of this build showed the incredible detail and skill you put into the project, not to mention they sounded fantastic :3
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