Another "Synergy" Build...

Discussion in 'Waveguides and Horns' started by SpeakerScott, Jan 21, 2013.

  1. More on the close MIC analogy
    In the horn, making the frustrum deeper is equivalent to moving the MIC back. You can only do this so far before you are through the horn wall. With phase plugs, you can move the driver in the opposite direction withouth increasing cavity volume and thus reduce path length differences even further....
  2. More measurements.

    I tested dual .5" holes, with volume plug and no frustrum.

    Doing this you loose a little top end extension, but with the benefit of much smoother rolloff. Based on these measurements I'll stick with my original plan of dual .5" port entrances, frustrum and some sort of volume plug. Still not 100% sure of the plug construction method.

    Attached Files:

  3. The plugs will get glued to the horn. One catch with doing this is you need to make sure that the filtering used and the plug dimensions are appropriate so that the midrange cone doesn't smack into it at high volumes. So there is a tradeoff between plug volume, high frequency extension and total output. In a residential setting something tells me this will never, if ever, be a big issue. (You'd be deaf as a post.)

    I think the notches/ripple in the offset port example is due to the out of phase arrival from the far side of the cone. It least that's my theory. It seems entirely plausible to me that it smooths out with dual ports since the pressure from the far side is relieved by the port on the far side. Again I keep having to come back to thinking of this system as a way of pressurizing a volume so that the sound exits some other aperture (besides the cone) the way you want it to exit. If you are thinking about it that way all you need is enough of a piston/motor combination to get the job done.
  4. Since this i one of the more active threads on synergy horns i thought i pop in and share two interesting driver suggestions. I do not know what price you can get but in Sweden they are not that expensive.
    First is the compression driver from Faital Pro, HF 107.

    I have never heard any of them but specs looks good to me. The hf107 and Bms 4550 would be nice to compere.

    Then there is a open back midrange with phase plug 3,5"-4" also from Italy. But from Sica. 2xfs/qes=~480
  5. Here's a shot of some of the measurements I did with a centered vs. offset port. These are the 4" closed back Celestions that Danley uses. They're on .5" mdf with a 2" dia frustrum .375" deep. My port is a curved slot roughly .3" wide by .6" long IIRC. The red curve is the offset port mounted on the Paraline which is on a 60x40 conical waveguide. The tan curve is a close mic measurement directly out of the offset port, so no horn loading. The purple curve is a close mic msmnt directly out of the centered port. Nevermind the difference in efficiency, that must have been due to mic placement.


    My goal was a 1.5khz crossover and I spent days trying to figure out why the mids wouldn't go any higher than about 1.1k. I figured it was the port/frustrum combo and I tried many different sizes/shapes on both with little change. The one thing I didn't change was the ports' relative position to the cone. Someone on DIYA said it was the unequal path-lengths from the offset port causing self-cancellation. So I took the measurements shown here and did the old palm to forehead slap.......doh!

  6. Huh, I didn't see any substantial difference in high frequency response from centered or offset until I added the volume plug. Then it was substantial.

    I'm working on a initial flare assembly jig. Should have pictures this weekend. I've been pretty quiet, work has gotten busy, but I've still made some progress. The penalty has been less posts!

  7. That effect seems to favor using smaller dia midranges. Path differences remain smaller even with very offset ports. I haven't had difficulty with high crossover by the luck of starting with 2inch dia cones. Probably good for efficiency but it's still higher than the woofers.

  8. Does it seem to be more pronounced in a paralline?

    Not sure...
  9. Nah, just on a horn. Never tried a Paraline (haven't seen a use for it yet in my stuff).
  10. Hey, SpeakerScott, any new progress on your Synergies?
    I'm hoping you're still going forward and have more to write about, to keep up the diyer's interest in these things. Since I've been too busy (and lazy) to do much myself the past month....
  11. I'm still working on it. Work has gotten crazy busy and the girls have been quit demanding of time. They say girls with a background like ours are about half their real age emotionally. So... I've gotten a few things done.

    1. A jig to help primary horn assembly. I'll post pictures...not 100% convinced this will be as helpful as I hoped. It can be tricky to hold on to all of the pieces.

    2. Created 4 volume plugs. I'm getting pretty fast at turning these, I've made a lot of experimental versions. I might make a video to show how I do it.

    3. Back cups for the drivers...this one is tricky. I'm trying to figure out a cheap easy way to do it. I found some clear pipe from McMaster-Carr with the exact ID but it would be more expensive than the drivers!!! I might actually try turning a few thousands off the inside of a PVC pipe. I have a carbide rougher, and apparently if you're willing to deal with hot slag it turns pretty easy.

    Anyway...that's where I'm at!

  12. Haven't posted in a bit. Here are two quick pics of the assembly jig I made to help hold the pieces.


    Attached Files:

  13. Some more progress pics....

    Attached Files:

  14. More...this time the horn is assembled...not quite everything done though.... still need to do more work on the frustrums and add the mounting holes/volume fillers for the mid-ranges...

    Attached Files:

  15. I've been working on different ways to put chambers on the mids. I made a jam chuck and turned a PVC pipe for one try. Not sure if this is the method I'm going with or not. Thinking of hot-gluing these to the drivers.

    Attached Files:

  16. One of the other things I experimented with was the woofer "port" diameter and size....there was audible chuffing at relatively low power levels for my original 1.25" size. I thought there might be, I just tried it to verify. It turns out you can use SoundEasy or any box program that's capable of doing a 4'th order bandpass enclosure to predict air velocity in the port. I hear chuffing around the drivers FS at pretty high's pretty much capable of doing a mini hair-trick at that point though, so at even pretty insane listening volumes I think it'll be okay.

    I don't know if the assembly jig is quite what I need...the horn is out of square a hair bit..could make things interesting in mounting it in the full enclosure.

    Sorry for the delays folks...that whole life thing intervenes. I had 3 birthdays, an anniversary and a scare where we were told we would have to send the girls back, because of a court decision. Then due to a bad decision by a biological relative, that was put on hold and it looks pretty good for us. So the synergy build has to take a back seat. Now that we are a bit clear of all that...I've started up again.
  17. So, made a lot of progress this weekend. Made the compression driver mounting plates, discovered a clearance issue with the 2 bolt pattern, fixed the issue (using a combo of a dremel and a chisel) and then started in on the secondary flare.

    This thing is bigger than I envisioned.

    My wife is going to kill me.

    Here's to hoping is sounds fantastic.


    Attached Files:

  18. nice clean fitting flare. Keep going! What did you end up with for the woofer hole diameter?
    I know the problem of which you speak. I was in deep dodo yesterday but I spent today on my back in the dirt (lierally) in a crawl space working on a honeydew project and now I'm out of the doghouse. Couple more days like that and I might dare to start a speaker project.
  19. I ended up at 2" diameter for the woofer entry ports. There *might* be some audible chuffing at <40Hz and more than 12mm excursion. But by that point I'll probably be deaf as a post anyway. At near xmax below 40Hz I can hear a bit of chuffing when playing single tones. Not sure how audible that will be in a real application as...that would be really...really loud.
  20. Sorry folks, not a lot of progress...we are back in a legal bind with the girls. It isn't hopeless, but it's going to be a tough one. The system didn't do it's job.
  21. Awesome thread. After scouring the net and reading I think I am just going to try your method of testing the mids and ports as you did. This will give me the information I am looking for to accomplish my goals and wants in my SH design. Thanks again.
  22. Awesome thread! Any updates? I am willing to offer my CNC router services to help you complete it.

    What are the approx dimensions of the horn?

  23. Yeah, there's been a lot of progress, but not any posts. I'm on my 4'th horn design, and I can't count the number of variations I went through on midrange porting....

    I've taken pics of the build so far and will be putting something together to detail the design process I went through.

    They are crazy labor intensive if you want the fit and finish I'm looking for.

    Here are two pics showing where they currently stand.


    Attached Files:

  24. Would love to see the measurements on these 8)
  25. Hi,
    What were the woofers that you used for this in the end?
    I've looked through the thread but can't seem to find your final choice on which model there.

    Cheers Paul.

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