Synergy horn build

[jhollander]

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.

[howard]

Good luck, John.

[KEtheredge87]

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!

[1100xxben]

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?

[bwaslo]

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.

[1100xxben]

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.

[jhollander]

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

[jhollander]

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.

[bwaslo]

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).

[jhollander]

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?

[bwaslo]

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.

[bwaslo]

The GRS looks pretty nice. Looks like you could mount it to a horn wall without a big spacer or worrying about the cone crashing, too. Is it's sensitivity like advertised?

[jhollander]

Right out of the box, with measured VAS and TS parms the sensitivities were 88 and 89. There was some inconsistency in the driver TS measurements. I should probably repeat/ check at 2.83v 1M in box.

The surround to the front edge of the gasket looks like about 2.5 mm. At half the xmax of 1.5mm the surround should not hit the side wall.

I'll be at MWAF this week, do you want me to send you one with a mailing tube kit?

[TN Allen]

This looks like an interesting project. Can someone suggest a link to an explanation of the benefit of this type of enclosure, or perhaps explain it?

[jhollander]

Tim, Bill could probably give a better explanation. For me it's about controlled directivity with fewer room interactions. I've done narrow baffle, open baffle, and tested some omni's, so for me this will be going in a completely opposite direction.

We'll see what the actual benefits turn out to be in a home environment. Assuming I can make a passive x-o work, this should be fun to compare to all the other RS28A speakers.

Here are a few links
http://www.danleysoundlabs.com/produ.../synergy-horn/
http://www.danleysoundlabs.com/danle...apped-Horn.pdf