The very low budget DIY synergy horn build

Inspired by paulspencer's fine work on his: DIY Synergy horn I set out to try and build one with drivers I had on hand for as cheap as I could.
You may have seen my post in his thread about a <$25 synergy horn, it will turn out to cost a little bit more then that.


The build begins, I liked the symmetrical appearance of the square 60x60 horn so that is what I chose to use.
The mid drivers are the $0.69 sony buyouts from PE, I have alot of those.
Here you can see me laying out the first panel with driver mounting position and the ports.



Three drawn out on a single 2'x4' sheet of 1/2" mdf


I tried a bunch of angles on scrap untill I got it right and cut my first three, they look like they fit together just fine.



All four cut and held together with some masking tape.


First look into the horn, an MTM bookshelf that holds 5.25" woofers for size reference.

Marking driver position on outside of the horn, drilling port holes and cutting
angles on the throat for a flat surface so the HF entry plate can be mounted.


Since the sony woofers have no gasket material on the front, I need to make
a small chamber in order to mount them to the horn. Holes drawn out and ready for routing.



Done.



Test for driver fit, look good.




More to come...

Yes I did, it works great. Does circles of any size from 2.5" to 22" diameter,
with larger sizes possible when using extensions.

Here is the little Cap that the HF driver (a soft dome tweeter) will mount to.
Ready for routing with a 45 degree chamfer on the inside.
I know it does not match angle of the horn, but it will all be filled in smooth with wood putty later.



Glue time a real pain in the butt, this was the best way I could figure to
hold all the pieces together.

Since this is only an experiment and the only cost to me is the mdf and some time, I did not use any software to calculate placement of the mid ports.
though I did try to use hornresp to simulate it I could not figure out if I was really entering the right values. After messing around with that for a while,
I just ended up placing the port as far up towards the throat as I could get them. Lots of science behind this one!

Glue is dry.


Time to see how the drivers all fit on the horn.


I tried playing some music with a basic crossover on it just to see how it sounds like this.
Not bad, but not very good either. I will need to put a rear chamber on the mids.

Forgot to post the picture looking into the horn with drivers installed, here it is:

Thanks guys.


Time to build the rear enclosure for the mids, I would have wanted to a full enclosure starting at the mouth of the horn but ended up making a smaller one halfway up.
The reasons for that is the full enclosure would be too large for the mids, and I am not planning on making this a three way horn.

I had making small brackets to extend an even surface out from the horn because making a square enclosure with the correct angle
to mount to the horn would have been alot more work to get right. here I have the pieces cut.


Checking the dry fit before I glue.


It would also be a good time to apply some wood filler
inside the horn to smooth out the HF entrance.

Here is what the box off the back of the horn will mount to.
Had to fill in the corners with the small squares as it is easier to do it that way then to make the brackets full length with multiple angles.
Who got their fingerprints all over my horn.



I sanded the wood putty and now the HF entrance is much smoother.



Dry fit of enclosure.



Clamp time.

Here I am finishing the rear enlosure, I put some 1"x2" around the edge of the mdf so I have something to hold the screws for the removable cover better then just the mdf.



Here is a closer look at the dome tweeter that I am using, it a buyout from PE #279-051.



Here it is mounted on the horn with some electrical tape to help smooth out where the driver frame meets up with the horn.



All done.



I tried playing around with the crossover but I don't get a lot of flexability with the crossover point as the rolloff of the mids/high limits it. It's kind of a mess but you can see here the raw driver FR along with the FR of the drivers with crossover. This was measured indoors about 1m from the horn.


You can see that the mids are not anything that could be called flat, High frequency is not too bad but overall not very good sounding.
This is how it sat for about four months in my basement while I moved on to other more sucessful projects.

Recently I started playing around with it again, I tried a dayton silky in it which did not turn out any better, I would even say it sounded worse.

Likely because the dayton did not have as smooth a match to the horn as the roundover on the faceplate of other tweeter did.


Then I decided what would happen if I ported the mid enclosure into the horn?
I also made the front mid chamber ports larger becuase I could not get to the backside with a router and use a chamfer bit to shorten them.


What it did to the FR:



Much much better, and I can highpass at 80-100hz and let the subs take over. I have it running right now on a simple second order crossover for both the mids/high at about 1100hz. I set it up in a small room where I padded the tweeter to taste which when I measured it came out to about 6dB under the mids:



And here is a video of me anoying the neighbors with it in the backyard
I am about 50 yards away before I start walking up to it.

The two DIY folded horn subs below it use a 8" Dayton DVC driver, and are powered by a Dayton APA-150.
The synergy horn is being powered by a Yamaha HTR-5450. It was crossed over at 90hz to the DIY horn subs, I did not have the crossover on the subs set up right 60hz lowpass so there was a large dip between 70-100hz.




The total cost was <$50:
sony mids: $0.69 x4
tweeter: $5.50
crossover parts : $18.54
Mdf and other material: $15-20

Now I just have to build the second one.

I aready had the drivers, they were just sitting on a shelf and after reading Paul's thread I thought that would be fun to try with stuff I have laying around. Nothing but a 4'x4' sheet of 1/2 mdf was puchased in order to build it.




It sounds quite good for something that was just thrown together with spare parts. I cannot give a real good impression on the sound until I build the second one (may be a while as it isn't really a high priority), and listening to just one speaker has a way of making my ears/head hurt after a while.

The sound is really good in the midrange, very clear and defined. The highs are a bit harsh due to the dome tweeter which has a fs of 1600hz and I am crossing at 1100hz. It does have a large effortless sound much more so then the speakers I built with two direct radiating 6.5" woofers and a waveguide loaded CD. I can't really say much more as I have only listened to it for maybe a half hour-45 min.

I want to do some off axis measurements (and compare some outdoor measurements with the indoor ones) but it has been too cold and or windy outside (mostly windy 10-20mph almost constant) when I have would have had a chance to do some the past week or so.




A miniDSP is already on my list of things I want to get.

I am not sure what back ports, or seat for that matter you are referring to?
the only ports are for the front mid chamber two per driver, and the four rear chamber ports a bit further towards the mouth.

I believe that is distortion from the cameras microphone, too loud for it to handle, in person the sound does not change when you walk up to it.

Edit: I just watched it again, there is some change while I walk past it.
johnbomb I think your right there, it has to do with the doppler effect that caused the change in sound.