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Discussion Starter #1
Sometime last year I became totally enamored by the Synergy Horn concept after several "a-ha" moments about how Tom Danley's other inventions work (Paraline, and Tapped Horn.) My S.O. (the bestest wife in the whole wide world) gave me permission to build a set of three for the LCR of our home theater. After many...many prototypes, rebuilds, back-tracks and a few choice words they are mostly done. I have Tom's permission to post details of my design, as it's his idea and he has it very well covered by patents.

First...for those that haven't heard a well designed DIY Synergy Horn, or the real deal. Find some. Now. They really are that special. I have a degree in Electrical Engineering and have designed audio equipment professionally on/off for over 20 years. They image better than any other speaker, and there is a precision and clarity that some of the crazy high end magnesium/beryllium/unobtanium based speakers can't match.

So, without further ado here are the basics for each speaker:

4 Dayton Classic 8" woofers, 295-310
4 Dayton Designer Series 3" woofers, 295-422
1 PRV Audio D290Py-B, 294-2833

22.5" Cube
60x60 Coverage Area
45Hz to 18kHz +/-3dB (ish)...more on that later.

I'll be posting the photo's I took during the build and my drawings...but it's going to take some time to put together all the info...so patience is appreciated. Questions are welcome at any time.

Scott
 

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Discussion Starter #2
Next up are some frequency response plots. I designed the speaker using SoundEasy V18, a Dayton Microphone and a custom jig I designed. SoundEasy is one of the best values...but also one of the quirkiest pieces of software I've ever used.

The on/off axis plots were measured with a real speaker in slightly different conditions than were used to measure the individual drivers for crossover development. I believe I might have some early reflections from a compost pile, trash can and garage door creeping in the on-off axis plots (taken at 0-10-20-30-45 degrees) which I didn't have for the measurements used for crossovers. Those were taken in a very large wide open band hall.

Scott
 

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One of the bigger difficulties for starting a project like this is figuring out how to build the speaker. I had a few rules I set out for myself:

1. Do something where the back cup design for the midrange speaker is relatively easy to implement. I had a version where I was turning 6" burial grade conduit on my lathe. Not cool. Pain in the rear really. Many different closed back speakers will work, but a lot of them are relatively large (5" diameter plus) making placement near the tweeter a bit more challenging.

2. All drivers needed to be nearly vertical. The suspensions of a lot of home drivers will take a set over time if stored horizontal...I've seen it way too often. Since I'm using relatively inexpensive drivers I wanted to avoid this since I don't plan on building myself new speakers every 5 years or so.

3. The outside size limit was set by what my S.O. is willing to live with...and frankly they are pushing the boundary.

4. The enclosure needed to have access ports on the sides and back so that I could get to the internal wiring and drivers. I tried a version where I bolted the horn into a box...but I couldn't ever get the box braced very stiffly.

So...that said I decided that all drivers would be mounted on the two vertical side walls of the horn...and that those walls would run from top to bottom aiding with the bracing.

When building one of these horns the important thing to realize is that you're building a compound mitered box. My favorite is at: http://www.pdxtex.com/canoe/compound.htm

You could do all of the calculations by spreadsheet and there are plenty available for download. The above calculator is handy because it assumes you'll be using a table saw and tries to make sure you can run every piece flat on the saw. (You might have to flip something over....)

I've attached the drawings I used as a guide. There is one that I'll post more detail, and that is the one I used to create a template to mark driver mounting holes, entry ports, surround clearance routing...etc.

One very important thing to note about doing something like this without having the aid of a CNC router to machine all your parts.

Tolerance errors stack up...work slowly, carefully and don't panic. Each speaker will end up slightly different. Work to fit the parts to the project, not build all the parts and hope they go together. This is something I learned when building fine furniture. My three speakers vary by up to 1/16" of an inch in some dimensions.

Scott
 

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The design leaves so many questions.. The ports seem so small for what's behind them. Is there a fixed box volume or is it a calculation of the drivers needs / angles... are the angles fixed or variable?



If/when I buy another house I've already been considering how to build a in wall / ceiling sound system. This seems worth while to me to learn more about. Prior I had considered a set of Tapped horns in the attic space and in wall surrounds.
 

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Discussion Starter #8
The design leaves so many questions.. The ports seem so small for what's behind them. Is there a fixed box volume or is it a calculation of the drivers needs / angles... are the angles fixed or variable?



If/when I buy another house I've already been considering how to build a in wall / ceiling sound system. This seems worth while to me to learn more about. Prior I had considered a set of Tapped horns in the attic space and in wall surrounds.
What questions do you have at this point besides those you have posted so far?

As far as box volume goes, the Dayton woofers in sealed configuration can be used from about 15 to 50 L with relatively small changes in F3, so the rear volume is what it is based on the size box I could live with.

For the ports...I haven't gotten to this yet...but port length is critical. Cutting frustums into the port lets you use much smaller diameters then otherwise would have been acceptable. I decided on the final size by making a version on a flat plate and operating the woofer at well past xmax at FS and cutting larger holes until I couldn't hear audible chuffing. The mids were tested using a similar method. I'll post plots later on.

BTW, I love tapped horns. I have a Stereo Integrity HT 15 in an 8' tapped horn. It will rattle your eyeballs.

Scott
 

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Discussion Starter #9
Wow, those have one unique look! How do they sound? Awesome work on the construction. The horns look very precise.
It's tough to describe...I've been to CES, THE SHOW, and many...many stores and homes with high end speakers. I've heard everything from Klipschorns, to Lowther to Wilson, to Manger, to any of the statement speakers from Focal, Dynaudio...and I'd rather have these.

They combine the ethereal sound qualities of a planer or ribbon speaker, with the clarity of a well designed dynamic speaker, the dynamics of a horn without any honk and the shear output of a pro-sound line array. Imaging is better than anything I've heard and frankly beats some headphones without having the "in your head" effect.

The crazy thing is...I'm not exaggerating, I cannot emphasize enough how special this design concept is.

Scott
 

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Discussion Starter #10
One of the things I see folks struggling with is how to place the holes for the entry ports...and figure out the size/shape of the pieces for the compound mitered box.

Hopefully this set of drawings helps simplify it.

This doesn't get into 1/4 wavelength spacing...it doesn't get into cutoff or flare-rate...it just makes sure the holes end up where you want them and don't hit the side of the box.

So the coverage angle sets the initial angles...in my case 60x60...but the method works for any desired angle. The tweeter size sets the throat dimension which is where you need to start. In my case I'm using a 1" compression driver so I wanted a 1"x1" throat for the horn. I've seen that Danley's speakers don't smooth out the throat entry, but I keep reading that the entry is critical for hi-fi. I figured out a relatively easy way to get it smoothed and I'll go into that later.

The first drawing is the completed placement of drivers, drawn to scale, and port holes...but it's complicated. I've got a bunch of other dimensions in there that I was using as an aid during construction.

The second drawing shows the lines of where the inside of the horn would fall, the outside if the horn if it were butt jointed and the sides didn't extend...and the outside line of the pieces of the horn that are butt jointed.

One thing to remember with this compound miter...the outsides are smaller than the inside for the cut pieces...you have to angle them back as the pieces rotate out. It's tough to explain, but you'll see it if you cut some test pieces.

Which brings me to another very important point.

For all that is good and holy, cut some test pieces. Don't be afraid. Cut lots....figure out how this goes together on smaller cheap scrap. You'll save yourself a lot of trouble.
 

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So next up in the build is how to repeatably drill all the stinking mounting holes. I wanted to use threaded inserts to ease driver replacement if ever necessary. I ordered a couple extra mids and woofers for myself in case one ever went bad. (One did...but in a crazy way, totally my fault...story to be told later.)

There will be hundreds of holes...between the access panels, driver mounting panels...etc. Have a drill press, it will speed things up greatly. It could be done by hand...very slowly and carefully...but it could be done. Also, please use a brad point bit or a forstner bit for drilling...preventing bits from wandering. Much more precise.

I made myself a marking template. I used 1/4" thick MDF that I laser cut using an exported DXF. (I have access to a laser cutter at work.) However, with a lot of careful measuring you could hand measure and mark it...and drill the guide.

I cut 1/4" holes and used something called a transfer punch to transfer them to the piece that would be used in the horn. It only took a couple of minutes to transfer all the drill locations to the work pieces where it would probably take you 20 or more each piece to measure every one. So totally worth the time.

You can also see I marked the location of the tweeter entry and the center line of the board.
 

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Laser cutter access - you lucky dog. I miss using a big Epilog 28"x40" in college; so nice for making templates, guides, parts, etc... The only problem I remember was somebody always cutting/engraving incompatible materials and cracking the focusing element...multiple times.

This build is really cool, seems like a cost effective way to get great sound as well.
 

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Next up is hole marking and drilling...for the driver mounting points I wanted to use threaded inserts. It happens the brass ones I used need a 1/4" hole. They are 6-32 which has plenty of holding power for an 8" woofer of the excursion of the Dayton.

I drilled each hole on my drill press.

Next I made marking drills for the woofer and midrange taps. I picked the smallest drill I had (not sure what size) and drilled all the way through since the back is what got marked. This gave me a precise location to drill on the front.

When I flipped the piece over I discovered that the hole was somewhat difficult to find...the MDF had "self healed" so I used a tiny plane to shave off the material covering the hole.

I drilled the tap ports for the woofers and mids from the front side of the horn using forstner bits. I didn't care too much about tearout on the back side since I knew I'd be grinding away at those areas anyway.

I then used a combination of dremel tools and routers to make clearence for the surrounds and cut aggressive frustums into both the mid and woofer holes.
 

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So next up is threaded insert installation. Buy. The. Tool.


Yes, there is a tool.

Buy it. It's very helpful. Also, install them on a very sturdy surface so you can press down hard as you are screwing them in. It helps prevent the MDF from pulling up...it still does, but not as bad. Then sand it flush. I put a dot of sanding sealer in the holes before screwing them in, in hopes that it would prevent the MDF from pulling up. I'm not sure it worked.

You can also see the jig I built to help hold the full height pieces.

The secondary flare and the primary flare were put together using gorilla glue which expands, aiding in assembly even if there is a small gap.

That said, work to minimize the gap. Gorilla glue isn't all that strong, so if you have large gaps you might consider secondary blocks, to increase glue surface area...I did on mine even though my gaps were pretty small.

I held the secondary flares in place using tape, and worked very slowly to ensure that each piece was glued on as square as possible. It was probably a week between start to finish since I was only gluing 1 secondary flare piece a day, one morning one at night. Patience is rewarded here....dry fit as much as possible.
 

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So next up is the process I used to smooth out the tweeter entry points. As far as I can see in the pictures on the Danley site...they don't do that. But I did...I kept reading about higher order modes...etc....so figured out a way to do it.

First I got two part epoxy putty to use as the filler. Next I drilled a piece of 1/8" MDF with a 1" hole. I covered it with masking tape, figuring that the epoxy would stick to the tape and the tape would come off the guide.

I then taped the guide to my entry throat and used it to build up and sand down the epoxy putty.

I thought I had gotten great photos of it.

I didn't, or if I did they are buried somewhere on my hard drive.

Scott
 

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More pictures of wrapping an enclosure around the horn.


When doing this, the idea is to keep everything as square as possible. I put some serious time in here... The best part is, this way you can use a bunch of off-cuts and odd sizes...since very few pieces are very large it's efficient sheet good usage.
 

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Sorry for the pause in updates...work got in the way.

One thing that might be asked is my finishing schedule. I'm a fan of the following:

1. Seal multiple spray coats of de-waxed shellac. I use a $15 Harbor Freight gun for most spraying jobs. I've owned fancier guns...and they do a better job. Not 20X better. I use automotive glazing compound to cover any scratches or rubs. (That's the pink stuff.)

2. Sand, down to ~300 grit...do not skip grits...do not rush...go slow. It will go faster in the long run.

3. Seal one more very light coat.

4. Build coats of finish with the recommended adhere coat...this will also expose any spots you missed in 1 and 2 for glazing and sanding.

5. Start with glazing and go to 2 again...repeat until you're happy.

I love Target Coatings products....they always work very well. The horns are as follows:

De-Waxed Shellac.
Glazing
De-Waxed Shellac (alcohol based).
Target Shellac as a bond coat (water based)
Target White Lacquer (roughly 3 coats...more glazing, sealer of Target water based shellac and 10 more coats of lacquer)

Yes...there are 14 (ish) coats of lacquer on the horns, and with the water based stuff it only took a long weekend.

And yes I used the $15 Harbor Freight HVLP gun, and I didn't build a booth.
 

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