DIY Synergy/Unity spreadsheet

Discussion in 'Waveguides and Horns' started by BillWaslo, Apr 29, 2012.

  1. --some shortcuts to stuff deeper into the thread:

    Newer kinda-linear-phase version of crossover:

    Square wave sweep on youtube:

    A wav file of the sweep input, if you want to try it with other speakers:

    With active MiniDSP crossover:

    Tony Seafords small box build:

    Woodgrain horn build:

    Here's the latest spreadsheet:

    |added March 29, 2014:| I finally found time to complete and update the document that details how to use the spreadsheet, cut the pieces, and assemble the horn. And how to come up with and build your own horn or Synergy waveguide to your specifications.

    And, now, back to the first post of this thread......................................
    I've been working on a DIY Unity type horn, using some inexpensive small 2" fullrange drivers available from various places. It is still being built (glued-up wood pieces are drying in the garage), but I thought I'd post an Excel97 spreadsheet I put together for designing the horn, figuring out the dimensional parameters to put into HornResponse, and calculating the panel dimensions and angles to cut for the structure. It's a lot pretty brain-hurting trig calculations, but I'm pretty sure I have them right. The spreadsheet could also be used for calculating the pieces to cut for a normal dual-expansion conical horn.

    There is also a page of basic instructions for how to use the spreadsheet. Let me know if there's anything that isn't clear.

    (Note: see this post, later in this thread, for crossover and more Synergy design
    url= )

    Tools needed include: table saw, good long metal meter or yardstick, calipers, belt sander, drill and bit, maybe a jigsaw or router, #4 wood screws, #8 wood screws, wood and clamps (such as for sled jigs, patience, bottle of aspirin. :)

    I'll post measurements when I get the drivers all mounted and tested (provided the results aren't too embarrassingly awful!).
    WARNING: The Synergy and Unity concepts are PATENTED by Tom Danley and cannot be built for sale without his approval. Please respect his patents, he deserves all benefits of this rather brilliant design concept!
    7/06/2012: Tom has given his ok for me to show Synergy-particular details of my design (I didn't want to do that without him bein ok with it) for DIY builders for their own use (only)..
  2. (cross-post from my thread at AVS, just to get all this stuff in one place):
    Tonight I slapped the midrange drivers on, put the back cups on them, wired them up and made a quick measurement:
    Not too bad, surprisingly smooth (that's an unsmoothed graph), goes lower than I expected, but not as high as modeled. I think I need to cut frustrums into the ports, will try that to see if I can approach 3kHz.. even if not, plenty usable as-is.

    This was a trial build (see see how well it matches HornResponse and to debug my calculations -- the build I did had some errors I had to patch, which are corrected in the posted spreadsheet). The HornResponse prediction isn't too far off other than at the high frequencies (and the response is much smoother than predicted, which showed stronger passband ripples).

    Here are some photos of the build process. As you can see, I didn't spend much effort on cosmetics for this first one. The next I plan to make prettier.
  3. Bill,

    Thanks for sharing your work! I appreciate the spreadsheet as well.

    Like many others, I am slowly experimenting with Unity designs. I also experienced the early roll-off with my first prototypes. I "fixed" a lot of it by changing the ports considerably, as well as filling the compression chamber. Bondo works wonders.

    I think this early roll off has a lot to do with how we are modeling them. As far as I can tell, modeling unitys within HornResp can not be done 100% correctly when simulating multiple drivers. The usual practice is to add the throat chamber volumes together, then add the port areas together.

    Issue is, I don't think that this approach is proper, and all the DIY results I have seen pretty much confirm that.

    At least when working in HornResp, 4X the box volume needs more than 4X the port area to maintain the tune with the same port length. When you use 4 drivers, with 4X the volume and 4X the area, the model tunes things too low. Model a unity with 1 driver, with a proper chamber volume and port for a good response. Then, using the same horn, model with 4 drivers, with 4X the chamber volume and 4X the port area, but the same length, then compare the impedance plots. In my experience, the multi-driver impedance peak will be lower if the single-driver model is "correct", and the multi-driver horn will have a rounded-off response.

    As I understand things (and I am still learning...a lot) no matter how many drivers you have in the model, HornResp only models a single port, and ports are all circular in section. Larger diameter ports have larger end corrections that auto-magically get applied in HornResp, lowering the tune by making the port appear longer. I believe that this is where the math breaks down with respect to accurately modeling multi-driver unity horns.

    Admittedly, I am still exploring and learning, but I have built and measured a few iterations of unitys so far, and have a lot of ideas rattling around in my head for the next round.

    Looking forward to your results (as well as some shop time to build my next iterations...) Thank you again for sharing.

  4. Lilmike, thanks much for your comments. What you say about HornResponse and end corrections makes sense. So you think I'd be closer modeling with one driver for best response shape and then just duplicating that 4x on the build?
  5. You're welcome. Glad that it makes some sense. I've been scratching my head on this for a while now. I will be modeling a single driver, then building with a pair in my next project.

    I think I made my ports too small and too short the first time around. At least with the drivers I had, larger and longer measured better (to a point). Still, I was not quite able to match the models, so take what I have said with a grain or two of salt. I'm just wandering down the same path as the rest of us.


    That next build is still a couple days off though....hope I can get things started soon.

    My first prototypes looked like this.


    I went through about 12 porting iterations with these until I could no longer attach the drivers.
  6. Update -- I used some wood putty to fill in the front chamber a little and also scooped out the port taper some. Increased the length of the tube behind the drivers to increase the volume. This is now much closer to what I modeled (I had forgotten to include the volume of the magnet behind the drivers, before, and also the volume within the cone itself in the front chamber). And the results fit the model reasonably well now:
    Red is model, blue is measured (level just adjusted for best overlap, not true sensitivity).

    Still not quite as strong at HF as modeled, but more than enough to reach the HF driver response I want to use.

    I think I'm ready to make some "real" ones next. These are quite fun to work with. Kind of like the speaker building equivalent of a ship-in-a-bottle.
  7. I started making three "real" SynergyDIY horns, and redid the spreadsheet for a more efficient (and neater-looking) shape. This spreadsheet is for a horn in which the inside of the "mouth" extends all the way out to the full height and width, without the useless outer lip. Like this sketch:
    Here's the link to the new spreadsheet:

    BTW, I downloaded the free open-source spreadsheet program "GNUmeric" and my horn spreadsheet opens just fine in it! So, if you don't have Excel, no worry, just download and use GNUmeric for free:

    And now, for some pictures of the build, to try to coax you into trying it (if I can make them, you can. I'm an abysmal cabinetmaker with cheap tools!).

    After cutting the boards to their outside dimensions and angle cutting the ends, ready for the marking up with guide lines for making the slanted cuts. The beer bottle is an essential tool for this part:

    A view of a "sled" jig for making compound angle cuts. Just a board, something to guide it on, and some clamps to hold the work down in the proper place. Pre-cut the jig board, then line up your work board to the cut edge, run it through again. You get perfect cuts without a sweat or much cost. Harbor Freight has the clamps for about $5.
    Some will have to be done with a vertical sled jig, just butt two boards together to make a sled that holds the work perpendicular to the saw table.

    After those are all done, more guide lines to figure where any offset drivers (midranges, woofers if you're going 3-way) go:

    For the first expansion "throat" section, I used wood screws to dry fit the pieces together, and then to hold he pieces while the glue dried. Get the pieces lined up right on the outside edge, it will make for less filing and sanding later (I wish I had on this first horn, but it still wasn't hard to clean up).

    To attach the "mouth" pieces, I couldn't get screws to attach things right, too hard to position while drilling or putting in the screws. In the end, I just used good old duct tape to hold stuff till it dried. It actually worked, though a more elegant solution would be nice....

    Here's how you'd like the outer corners to look (sorry for the out of focus shot). My other 3 corners weren't so tight right away, but are close enough. (Edit: not a great photo -- the "mouth" of the horn is upwards, thats the other side of the open mouth you see across the top...)

    Here is the front view, before any filing, sanding, or filling. Came out reasonably decent, and verifies the spreadsheet calculations:

    I had to jump ahead and see what it was going to look like with all the drivers glommed onto it:
    The midranges will have back chambers (mailing tube sections) and the woofers will work into a box for bass. According to HornResponse, it should work (the horn of course won't load the woofers at bass frequencies, but I'll get all the drivers playing from the same acoustic center -- a point source.

    Here's a view of the other side, without drivers yet, showing the tapered port holes for the midranges and woofers. I may still need to put in plugs to fill in the midrange and woofer cone volumes, will see how this works first.

    I'm writing this up while glue dries on the tweeter mounting board. I'll update when I can get drivers really mounted and can make some measurements. I still have some work in store to figure out how to mount "super driver" into an enclosure (planning on a tower type for the L and R, a long horizontal box for center channel).

    The dimensions of this horn, BTW, are 24"W x 15.3" high.
  8. Awesome!!

    Can't wait to see measurements.

    As usual, I'm more than a few steps behind with my build, but it looks like I have finally solved an issue that's been nagging me when it comes to cutting these accurately.

    Will grab the new spreadsheet and check it out too.
  9. Thanks Lilmike.
    I got all the drivers stuck onto it today, and here are individual responses from about 2ft away. Looks like there is more than enough overlap (could almost just do the woofer and tweeter, I'm surprised the woofer goes that high where I have it ported).
    The woofer (red) doesn't have an enclosure other than the horn in front of it. That should come up down low when it gets one.

    Guess I'll go ahead and assemble the other two like this one. Next is to work up a good way to mount it into a floorstanding cabinet.

    Though I suspect I'm never gonna convince my wife to let me permanently install these in the living room.

    Attached Files:

  10. Great stuff!! Looking forward to seeing this project progress...

  11. Plot's a little tiny, but the results look pretty good.

    Have you measured THD yet? I saw a marked decrease in THD when I opened up the ports.
  12. No, just basic responses. The setup is a bit clumsy to work with, plus the wife is home so loud sweeps aren't appreciated just now!

    I don't think I want to open up the ports more than they are, I can see an effect on midrange response from the woofer ports (covering them flattens a slight dip at 1khz in a hires measurement). I might move the bass ports closer to the mouth to minimize that. Do you have yours making music yet?
  13. Nowhere close. Only audio stuff I have been doing lately is folding tapped horn subs....

    Those prototypes were nothing more than an educational experience, and they served that purpose very well. I learned a bunch.

    After a few lightbulb moments and countless simulations, I think I have several ideas that are worth building. They are all larger than I can safely and accurately cut on the radial arm, table saw, or sliding compound miter, which means I need to use the tracksaw. I can do miters and bevels on the tracksaw, but not at the level of accuracy I need for making unity horns, so I am upgrading the angle setting system on my tracksaw table's fence. I'm integrating a sine bar, which will allow me to set angles to within 1/10 of a degree, as well as reverse the fence for cutting the opposite side with the same accuracy.

    Once I get the saw table working the way I want it to, another unity prototype is next on my list.

    For the mids, it looks like your ports are plenty big, those are tiny cones. The low frequency drivers might be a bit choked though. How large are the ports relative to the driver's Sd?
  14. Mounting scheme

    Here's the scheme I came up for mounting the horns. Since I have woofers firing into the horn, their backs have to be enclosed. I plan to make floor standing "towers" (which being 24" wide will look more like monoliths). I'll have these horns insert into a mounting frame that is in the tower enclosure, much like most individual drivers do. To do that, I need a flat around behind the mouth like the rim of a woofer.

    So, I ripped some angled pieces of wood from ply for the less acute angles and from 2x4's for the more acute ones. These I glued to the back of the horns, using short wood screws to hold them temporarily until the wood glue dried. It was a pretty quick operation, not difficult to do at all. Precision not required, since gasket will be used on these surfaces when mounting into the box.

    Some photos:

    Slats glued onto the long sides:

    gluing a slat on a short side:

    After the slats are on (with the short ones cut at diagonals to clear the top/bottom mouth pieces), part of top/bottom pieces stick out beyond the mounting surface. Just take a razor saw (or the like) and trim it off, very easy.

    Of course there are gaps, but this is in the back, so just fill them with putty. I used "Water Putty", magical stuff.

    Three horns, water putty hardening up (sand them down before the putty totally hardens -- it isn't called "Rock Hard" for nothing).

    Next steps: paint the horns and build the cabinets.
  15. That helped me figure out how the heck I'm gonna mount mine.


    Got the miter angles handled. Next is bevel angles, should get that done on Saturday if I can actually build what I have drawn up.

    Have a few other little projects I want to work on, but hopefully I can get a unity project started before too long.
  16. Glad it helps, Lilmike. Hope it works (for both of us).

    I hit mine with some rattle can paint tonight. Flat black. They look..... flat. I think I'll get some semigloss texture paint and put that on top.
  17. Quick update -- I repainted the fronts of the horns with "hammered texture" semigloss black paint. They don't look flat anymore, but I think I liked the looks better with no paint on them. But eventually they'll be behind grilles so black is needed back there. Not so cool to look at when you can't so easily see all the angles.

    I've been cutting pieces for the outer cabinet the past week. I decided to make it mostly out of 1/2 inch ply, with a B&W "matrix" type construction to get good rigidity with less weight. The last big speakers I made ended up too large for me to carry, so I don't want to make that mistake again. Matrix construction takes a lot of ply, and worse, a LOT of cutting out of windows in all the ply cross pieces. I have a photo of all the little wooden circles and ovals all over the garage floor. Took most of the day, and my hand hurts now from guiding the jigsaw, but it's all cut out out now. I started the glue-up, which will go in stages. Pictures will get posted when I get enough ambition to load them from the phone camera into the computer.
  18. Here are some shots of the Synergy DIY cabinets under construction.
    Ye Olde Horne Shoppe:
    Note all the little plywood disks on the floor after cutting out the pieces for the window braces (some assembled braces and panels shown alongside).

    Testing the fit of a waveguide into the cabinet pieces:

    A front and a back view (without the back panels) after the glue has set and the clamps just removed; night time flash shot:

    Shouldn't be too long before some measurements can be made, this weekend.
  19. Some daylight photos, after some sanding, a few coats of finish, gasketing, and the drivers onto the horn.

    Did some measurements today. Box tuning is off, will work on that this afternoon. Got enough to do a quick crossover in PCD, it doesn't appear to be hard to do at all. I think these things are going to work out pretty well. Though it looks like I could maybe have done it as a two way, with the woofers moved in closer to the apex and with a larger CD driver.


    Notice that I switched to a Celestion CDX1-1445 for the tweeter, as it's exit angle was about twice as wide and it has greater extension. Total driver cost for the speaker is under $200, still, for a pair!

    A bit of a delay... the second waveguide fell off a shelf (ok, I bumped into it) and broke into about 4 pieces last night :'( . I'm trying to re-glue it back together now... hope I don't have to rebuild it from scratch.
  20. That celestion is a wicked choice for a unity horn ;D
  21. Very nice indeed! The PVC bits are rear chambers for the mids, correct?

  22. They're actually cardboard mailing tubes, but, yes, back chambers for the mids.
  23. Got a crossover! It was unexpectedly easy to do on PCD. At first I had it pretty flat, but the sound seemed too bright so I toned it down a little bit with a "house curve". I still may tweak some after I get some more absorbent in the box, but I think it's close. Sounds quite good. It tends to make me want to turn it up. Here's some measured curves (about a meter away, in-room).

    And with sixth octave smoothing:

    Maybe when Erich comes over I can talk him into helping me take it outside to do some polar measurements without the room effects.

    These will be at MWAF.... in the "Under $200 Category". :eek:
    I'll also have the SEOS12/Designer12 set there, too.
  24. Very nice.

    I've been busy playing with subs (at least the designing and folding part) as well as wrenching on the rigs, so no progress on mine at all.

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