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Synergy horn build

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  • bwaslo
    replied
    Yeah, HR does model that. You can see on some models the low end tick up when the back chamber size is reduced (assuming the horn and driver are right for that). When I was using the little 2" surplus drivers a short mailing tube did ok, but when I tried to use things like 3FE22, it was hard to get the back chamber small enough without messy patching of the back of the basket. I was pushing to get low enough with the mid really close to the throat, though, so the mid could go high enough for a small tweeter I like.

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  • jhollander
    replied
    Bill, I'm close. The horn Fc is 400 hz, the sealed chamber Fs almost 300 hz. I could shrink the mailing tube a bit more, but thought this was a good starting point.

    I was not sure if the Horn Response models includes reactance(?) I assume it must account for the mass of air in the horn?

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  • bwaslo
    replied
    So you're not planning on using reactance annulling (stiff compliance behind the cone to offset mass of air in the horn) to pull up the low end?
    I guess that's ok if you're only after directivity (which is mostly what I'm after).

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  • jhollander
    replied
    Here is the GRS in box, on a flat baffle. This looks good to me. Preliminary x-o points at 400 and 1,500 hz.

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  • jhollander
    replied
    The GRS 4FR-8 mid fits great in a 4 inch mailing tube. I started with 4 inch PVC pipe and then tried the mailing tube. The mailing tube leaves more of the mounting holes open on the frame. The mid is the only untested piece of the horn.

    The design has been updated with the woofer ports now inside the horn mouth

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  • 1100xxben
    replied
    Originally posted by bwaslo View Post
    I wouldn't worry too much about symmetry on the drivers, my most recent posted Synergy horn ("SmallSyns", see link) use just one midrange driver per horn. There is certainly no need for more than one 4" midrange in a horn for home use in terms of SPL requirements, and the fewer holes in the horn walls, the better for the tweeter! And there is actually some advantage to being asymmetric, as response deviation due to finite wall lengths and diffractions don't sum up as much when measured on-axis as they do when things are symmetric in the horn. That's one of the reasons I like using rectangular or "superelliptical" (SEOS) horns, there's less symmetry in horizontal vs vertical so you don't get the big hole in direct on-axis response like with a circular or square horn.
    Good information. Thanks.

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  • bwaslo
    replied
    John, interesting project, hope it comes out well. I'm surprised you're able to easily get a small enough volume chamber behind the mids to work with a Synergy horn, that often takes some tedious patching of the back of the basket to make it like a sealed-back mid, and getting around the terminal strip can be an issue. It would be good if that does work out, the diameter of the driver is good for fitting things together, and the price is also nice. I like the Celestion TF0410MR sealed back mid for that, but it's hard to get at a decent price in small quantities and PE doesn't carry it (I tried to convince Brian, but not enough customer interest in that kind of thing).

    I wouldn't worry too much about symmetry on the drivers, my most recent posted Synergy horn ("SmallSyns", see link) use just one midrange driver per horn. There is certainly no need for more than one 4" midrange in a horn for home use in terms of SPL requirements, and the fewer holes in the horn walls, the better for the tweeter! And there is actually some advantage to being asymmetric, as response deviation due to finite wall lengths and diffractions don't sum up as much when measured on-axis as they do when things are symmetric in the horn. That's one of the reasons I like using rectangular or "superelliptical" (SEOS) horns, there's less symmetry in horizontal vs vertical so you don't get the big hole in direct on-axis response like with a circular or square horn.
    I posted a few plots of this speaker build on another thread of xrk971's, so thought I'd stop hijacking his thread ( http://www.diyaudio.com/forums/mul

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  • 1100xxben
    replied
    John, typically Synergy horns have symmetric loading of the transducers, at least in one dimension. By placing the 2 LF drivers on the bottom and the two MF drivers on the top, you're creating an asymmetric load. It may not be as big of an issue with the LF, but I would definitely think this would cause some weird behavior in the vertical pattern of the mid-range. Have you done any testing of the low and mid drivers in this type of configuration?

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  • KEtheredge87
    replied
    Hey John, That's a very interesting jig you've made for the angled cuts. I'm sure it's helping you out... although I would still find a way to screw it up, or spend more time "adjusting" my table saw to be sure my alignment is correct. I've learned not to mess with it, or else I spend all my time attempting to fix the problem I create by messing with it in the first place! Analysis Paralysis of the table saw is a terrible thing.

    At any rate... I'm intrigued to see this design keep coming along. I've never seen a box of this style come together before, so I'm sure there's some interesting acoustics at play. Keep up the good work!

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  • howard
    replied
    Good luck, John.

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  • jhollander
    replied
    Cut some wood, then recut some more, then made some scrap. The benefit of using MDF is that you can glue it back together. I found some errors in my drawings. Good thing I'm making a prototype.



    The angled wings were the most time consuming to make. Unfortunately that's where the drawing was wrong. This speaker has lots of parts inside.


    Jig for the relief cuts. There has to be a better way to make this jig.



    Did get the midrange chambers done.

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  • jhollander
    replied
    Here's Bill library link http://libinst.com/SynergyCalc/

    Bill and I had a discussion about some of the calculations used for Horn Response. That aside the spread sheet is great for figuring out the angles to cut. I removed the waist banding/ last flare from my horn.

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  • skatz
    replied
    John

    Do you have a link to Bill Waslo's spreadsheet for the synergy horn? I have a terrible time every time I try a search on DIYaudio, usually don't find things I know to be there!

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  • jhollander
    replied
    This is not going to make MWAF this year. I'd be happy if I made the Design team end in September.

    I made a bunch of tests with phase plugs, unfortunately none with the F model. What I found was that I could not get the shape right or close enough to the dome to stop the destructive interference. Most of the tweeters I tested were 1 inch dome that were recessed behind the face plate. The XT and RS that performed better also had very little recess.

    Note the Wolf added a grill and phase plug to his TL labs tweeter. He might have some interesting measurements. If you are following the wave guide thread, I do think the edge overlap is important.

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  • 6thplanet
    replied
    Could you use your own "phase plug" on the F tweet?

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