M2 Synergy Horn

[Patrick Bateman]

Last week I did some work with Voishvillo type phase plugs, and it seemed to work out well.

I was curious to see how that would work on a Synergy Horn, so I thought I'd take a crack at it.

I think there's a fairly good chance this won't work, but the only way to find out is to build it.

Here's some pics of the model.







This waveguide looks admittedly bizarre, but there's a method to my madness. As detailed here*, it is possible to 'mask' off a great deal of a radiator and still have wide bandwidth. For instance, JBL 'masks off' about 50% of the diaphragm of their EON drivers.

It occurred to me that it might be possible to do the exact same thing in a waveguide, basically take a conventional wave guide and 'fill' half of it's volume.


The final shape winds up very reminiscent of the JBL M2

I did something similar two years ago : Synergy horn - 3d printing entry?


* Car Audio | DiyMobileAudio.com | Car Stereo Forum - View Single Post - Imitation

[Patrick Bateman]

I think JBL is using that weird shape for a couple reasons:

1) it looks neat

2) The reason that narrow angle horns have higher output is because they're radiating into a smaller area. Conversely, wide angle horns have lower output because they're radiating into a wider angle. The M2 style waveguide combines both; it has a wide beamwidth, but it's on-axis SPL should be higher than a conventional wide angle waveguide because half of the M2 waveguide is 'filled.' IMHO the shape is reminiscent of the Voishvillo phase plug on the M2's driver (JBL D2430K)


In my application, I am after a similar goal. I'm trying to make a waveguide that's as shallow as humanly possible, but with a decent amount of gain. I am hoping that I can sacrifice some frequency response smoothness for higher efficiency.


By far, the main reason I'm using this shape is that it allows me to 'push' the Synergy midranges right into the 'knuckles' on the waveguide.

This thing is insanely small, about three liters in volume. It's approximately 8" x 6" x 4". The idea is to 'push' it back into a corner, as far as possible.

[Patrick Bateman]

If anyone's curious, here's some pics of the waveguide as a 'work-in-progress'
Note that there's quite a bit of volume inside of those 'knuckles', which is where I hid the midrange drivers

The waveguide is printing as we speak...

[wesayso]

The entry holes are not neatly hidden near the corners anymore... hmmm...

[Patrick Bateman]

Originally Posted by wesayso

The entry holes are not neatly hidden near the corners anymore... hmmm...

Yep.

This is a very specialized solution, designed to do one thing only:

I want it to fit as tightly into a corner as possible.







In these pics, I've added a 60x40 pyramid to illustrate how the midranges and the tweeters fit inside the space. Basically I curved the walls and added those 'knuckles' to get everything inside of that envelope.

[bwaslo]

You're getting really good with the 3D sketches there, John!

[jrh0516]

Amazing drawing and interesting concept. I assume the plan is to 3-D print something?

[Patrick Bateman]

I need to give a quick 'shout out' to Monoprice for my new 3D printer. It's 2/3rds the price of my other printer*, so I'd expected it to suck. And I was honestly prepared for it to be junk, but I figured I'd rather risk $400 than spend $1000 at Frys.

But lo and behold, it's light years ahead of my other printer.

Whenever I printed something on my other printer, I'd say there was a 25% chance that the print would fail IF it was about half a liter in volume. But the bigger the volume got, the more likely it would fail. It reached a point where just about anything larger than a liter in size would fail. Generally the way it would fail is that the print head would slam into the print, and knock it right off the print bed.

That printer was LITERALLY making me insane, because I'd invest a whole weekend designing something in 3D, only to watch the print fail. Week in, week out, for the better part of the last two years.

But this new printer JUST WORKS.

If I had to speculate why, I believe the print head and the fans work better.

I'm going to feel dumb if the printer heads downhill from here, but so far, so good.

https://www.monoprice.com/Product?p_id=15711



* my original 3D printer is Printrbot Simple Metal (now discontinued)

[Patrick Bateman]

The printed waveguide. Note the quality is light years ahead of my other 3D prints over the past couple years


This waveguide simply doesn't work with dome tweeters. There was a distinct 'sawtooth' pattern in the frequency response. My work with Hornresp has taught me that the 'sawtooth' pattern in horns is caused when you have a driver on the horn that doesn't have enough BL.

Based on that, I slapped a BMS 4552 on there that I bought from Danley Sound Labs

That helped quite a bit, the peaks and dips were reduced by about 50%

I'll post polars and frequency response later


I used a soldering iron and a file to enlarge the throat from 19mm to 25mm (The waveguide was intended to be used with a SB19)


While unintentional, my new trike is the exact same color as this waveguide. Neat.

[silverprout]

There is some lacquer on the market specifically designed to smooth the 3D printing parts surfaces