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Dual Exhaust

4thtry4thtry
in DIY
I started building these in 1991.  When the cabinets were about 80% finished, I got sidetracked on another project.  And for some reason or another, I never came back.  The unfinished cabinets sat in storage, collecting dust, for the next 26 years! :o   The original driver cutouts were for DYnaudio drivers, but they were never mounted. :'(

Last month, as I walked past these old cabs, I noticed that the woofer cutouts seemed close to the SB Acoustics Satori woofers I had on hand.  The old cabinet used a traditional style TL and I wondered if I could re-tune it and make it work as a modern day ML-TL?  :)


So I ran some ML-TL alignments using the LA beta TL software package and found that a slightly drooping, soft knee low frequency alignment, good to about 30Hz, could be created in this box.  All I had to do was to make a few relatively simple changes to the overall length, port location, and stuffing plan. 

Here are some pics of the old cabinets, taken in 1991. Sorry for the poor quality; I scanned the negatives and cleaned them up as best I could. 










Thanks for looking.  I'll stop back later with xover, measurements & a few current pictures. 

Bill

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Comments

  • 4thtry4thtry
    Here are a few measurements.  BSC is about 5dB, plus or minus 1dB.  I used Jeff B's Response Blender spreadsheet to adjust my NF measurements to include diffraction.  I use Open Office Calc, not Excel.  I can enter the baffle data to generate a correction file, but I then have to manually cut and paste this data to a new spreadsheet so that I can adjust my near-field data.








    kennykJasonPS7910
  • jr@macjr@mac
    Those tweeters look familiar ;-)

    Great project!
    I have a signature.
  • 4thtry4thtry
    Thanks!  Thought you might want to hear them again.   Should have them ready to play music sometime next week! :)
  • ani_101ani_101
    What is the sw you are using for calculating the TL?
  • 4thtry4thtry
    ani_101 said:
    What is the sw you are using for calculating the TL?

    It is the Leonard Audio Transmission Line program.  There was a long thread about this program on www.diyaudio.com and PETT a few years ago.  The program was a free download, but has not been updated since 2014.  I am using version 3.6.3.5.   Here is a link if you want to check it out.  I don't know if this link still works.

    http://leonardaudio.co.uk/

  • 4thtry4thtry
    Here are some construction pics detailing some of my retrofit operation:

    I moved the port down and added a PE 268-368 PSP3OFH 3" outside type flare to the end of a 2.5" PVC elbow.   The PVC elbow is actually 2.9" ID and is butt joined to the flare.  I then added a short piece of 2.5" ID PVC pipe, which makes the total port length about 8 inches.  I made a gasket for it out of 1/16" foam sheet material from Michaels craft store.



    I butt joined this flare to the 2.9" ID elbow and then silicone rubber cemented it in place.  Then I cut a 1 inch long piece of PVC from a length of 3" ID stuff I had on hand.  Then I cut this 1 inch
    ring into 4 separate pieces on my band saw and made a silicone rubber reinforced junction.  I was very generous with the silicone and when it cures completely this should produce a very strong joint between the black PE flare and the PVC elbow.



  • 4thtry4thtry
    Here are some crossover pictures:

    The top crossover board is for the other channel's tweeter.  This board slides into the slot just above the needle nose pliers.  This gives me easy access to the tweeter board for mods.  Just pull it out, re-solder, and go!

    The bottom crossover board is for the woofer.  If flips into the access hole just above it:




    Note:  I had to grind a little material off this 3.3mH P-core inductor to that it would fit in place when I flipped the board in place.  Grinding this small amount of material off reduced the measured inductance by about 1% from 3.38 to 3.34mH.  This did not affect the FR graph at all.


    greywarden
  • 4thtry4thtry
    And here are a couple pics showing the oak corner molding being glued in place with strap clamps.  This is a beer budget project, so I am using cheap 3/4" oak corner molding and 1/4" oak plywood to cover up the particle board.  I am hoping it will look much better once I get some stain and finish on it.




     
  • 4thtry4thtry
    ani_101 said:
    What is the sw you are using for calculating the TL?
    Oh, I forgot to mention one thing about this program.  I have found from experience, in running models on existing TL's and making comparisons, that there is a "fudge factor" that needs to be applied to the stuffing density so that the model matches the expected results from other programs.  Something is going on that I do not fully understand.  
  • 4thtry4thtry
    Getting the Esoteric tweeter to fit was a real bear.  I had to cut out a "waxing-cresent-moon" shaped insert plug on my band saw to get it to work (see pic).   The original hole was for a DYnaudio D28af tweeter.  When I got done, I had a somewhat odd looking oval shaped opening with some mounting holes that ended up very close to the two lower edges.  It doesn't look pretty, but it works, and seals the tweeter in place properly.  :)



    I glued some backer boards inside the cabinet behind the old TL terminus hole and then sealed up the old opening with a plug.  This plug can be removed to adjust stuffing.  I have a small amount of stuffing at the end of the line to act as a trap.  The new terminus/port was moved to the bottom of the enclosure. 






  • 6thplanet6thplanet
    Cool cabs Bill. Looks like a lot is going on in there. Do those xover cavities act as resonance traps (with all the holes right by the woofer?) 
  • ani_101ani_101
    I tried this program a few months back, but the example and help is spartan, and couldn't figure out much. Do you have a set of steps that you do? I am just generally lost. 
  • ani_101ani_101
    Those are some nice drivers for a beer budget project...!
  • 4thtry4thtry
    6thplanet said:
    Cool cabs Bill. Looks like a lot is going on in there. Do those xover cavities act as resonance traps (with all the holes right by the woofer?) 
    Yes.  And there is another 9" long trap at the end of the line that you cannot see.  I am not sure what the frequency cutoffs are or even if these smaller traps are very effective.  My thinking, back in 1991, was to minimize  the amount of upper mid-range energy from reflecting back and hitting the woofer cone. Perhaps I could have left this entire trap area open and simply stuffed it with poly.  I was trying to design something similar to the baffles in an automobile muffler.     
  • 4thtry4thtry
    ani_101 said:
    I tried this program a few months back, but the example and help is spartan, and couldn't figure out much. Do you have a set of steps that you do? I am just generally lost. 
    Yes.  The program is very easy to use once you get the hang of it.  But you have to re-size the cabinet CAD screen tab, widening it out so that you can see all the data entry fields.  You probably opened this screen and got stuck because the data entry fields are hidden.  But once you re-size this tab, it is a simple matter of entering all the TL parameters and watching the cabinet sections change shape.  You can easily move the driver up and down the line, add sections, change stuffing densities in sections, position and add ports along new branches, etc.  And when you add stuffing, the actual stuffing you use in the box is about double what you actually entered in the data field (fudge factor).
  • 4thtry4thtry
    ani_101 said:
    Those are some nice drivers for a beer budget project...!

    I agree.  I guess it is a beer budget from my perspective alone.  JR gave me the tweeters and I scored the Satori woofers as a door prize at InDIYana 2016.  I built most of the cabinets in 1991, so my current cost for lumber was almost zero.  And my PE order for crossover parts was roughly $100.  I'd call that a beer budget!  B)   
  • 4thtry4thtry
    Here are some basic specs & features of the speaker:

    Description:  Floor standing two way using a 70" ML-TL on the woofer and a traditional
                       30" TL on the tweeter.

    Drivers:  SB Acoustics Satori MW16P-8 6.5" woofer
                 Dayton Esoteric ES25Nd-4 Tweeter

    Crossover:  1.1kHz @ 12dB octave on tweeter and 6dB/octave on woofer (electrical)
                      Zobel FR shaping networks on both woofer & tweeter.  HF tank on woofer.
               
    Sensitivity:  87dB @ 2.83V/1 meter

    Woofer loading:  70" ML-TL tuned to 29Hz.  Constant cross section of 5.5x6.75".  2.9" ID
                             port elbow approx 8" long.  Stuffing density and location adjusted per model.

    Tweeter loading:  30" traditional TL designed to absorb as much of the rear wave from the
                              tweeter as possible, thus reducing the amount of midrange energy reflecting
                              back to the tweeter cone.  The cross sectional area is tapered from
                              2.19x6.75" at the beginning to 1.62x6.75" at the terminus.

    Size:    External:  49" H x 8.5" W x 13.25" D
               Baffle:  8.5" W x 48" H overall
               Woofer: 35.5" up from bottom, centered
               Tweeter:  43.25" up from bottom, centered

    Weight:  73 lbs each on my uncalibrated bathroom scales.
     

  • 4thtry4thtry
    To develop the crossover, I created several sets of polar position driver icons in XSim so that I could swap them out on the fly.  In this way, I was able to zero in, by trial & error, on the best overall compromise between on and off axis response.  The speakers are now finished, with all crossover parts and drivers in place.  As you can see below, I ran several polar response measurements on the finished speakers.  I found that they match my initial polar response models quite well.

    Test setup:




    For the verticals, a 5 to 6dB depression occurs in the 1-2kHz region on the blue, -20 degree curve.  This is the result of my crossover design which causes the vertical lobe to point upward. This depression is what you would hear if you were sitting on the floor in front of the speaker.  The black curve is what you would hear sitting in a chair.  And the red curve is what you would hear when standing. 



    Here is a graph showing the average of 24 horizontal curves.  I turned the turntable 15 degrees for each measurement, spinning it a full 360 degrees.



    And, finally, here is an averaged listening window graph.  I averaged 18 measurements, taken at a distance of 2 meters, inside a wide 4x6' window:






    greywardenkennykJasonPD1PP1N
  • kennykkennyk
    I have to go back to that software. ;)
    ............. could you hum a few bars.
  • 6thplanet6thplanet
    Nice job, I bet they sound wonderful, is that a MWAF possibility?
  • 4thtry4thtry
    6thplanet said:
    Nice job, I bet they sound wonderful, is that a MWAF possibility?
    Thanks, Eric.  They will be making an appearance in Sioux Falls shortly.  For MWAF, my current plan is the much smaller "Plumbers Delight" speakers.  Space in my little Versa is at a premium, and I have a nasty habit of buying more drivers than I need at the tent sale.  And then I usually wander over to the swap meet area at noon and start loading up on vintage reel-to-reel tape recorders and other classic stuff. :)   
  • 4thtry4thtry
    I found my original "Dual Exhaust" cabinet drawings from 1991:


    Side & Front View:



    Tweeter Side View:



  • Nicholas_23Nicholas_23
    You sir ,have the patience of Job

  • 4thtry4thtry

    Update:

    Based on the Dakota event listening session, I modified my Dual Exhaust speakers by shortening the port by about 3 inches, reducing the stuffing density in the front half, boosting the stuffing in the trap area, and increasing the length of the unstuffed area.  Below is the TL model showing before and after modifications.

    Before modification:

    After modification:


    They now have more deep bass below 100Hz when placed 8 feet from the rear wall.  Thanks to everyone at Dakota for allowing me to move my speakers forward and backward during playback.  This helped me a great deal to "hear" and correct the problem.  The port output is now roughly 3dB higher below 100Hz and is re-tuned from 28 up to 32Hz (no more drooping response below 100Hz).

  • 4thtry4thtry
     A little progress.  Stained the cabs and sprayed two coats of high gloss poly so far.  Based on how the poly is soaking in, I think I will hit them with another 2 to 3 coats, then pronounce the finish finished.  =) 
  • 4thtry4thtry
    testing attaching image
  • ani_101ani_101
    No image....
  • 4thtry4thtry
    Looks like I can no longer attach pictures.  Pics show up as an attachment, but when I click "post comment" they disappear.
  • 4thtry4thtry

    To review, I attempted to attach the following images with no luck.  They all have the .jpg extension and are fairly small (191 to 240KB):

    _DS50968.jpg  225KB 

    _DS50957.jpg  240KB

    _DS50959.jpg  191KB

    _DS50987.jpg  194KB

    _DS50999.jpg  191KB

    I will wait 5 minutes, log in and out, and try attaching again

    Bill

  • 4thtry4thtry
    2ndtry
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