Horn for 2445J - throat angle? Elliptical options?

Posted by hollowboy (A) on January 1, 2016 at 20:32:23

Hello,

THROAT ANGLE

A couple of sources, including this:http://www.audioheritage.org/html/projectmay/technology/435be.htm
...say that older JBL 2" drivers "had a 180hz flare rate whose origin dates back to the original AT&T Labs designs from the 1930's. This low rate was necessary to accommodate the low cross-over points used in early two-way loudspeakers."

So I looked this up, made a spreadsheet, and calculated that a 180Hz exponential flare doubles in area every ~10cm, and from this I worked out that the initial horn angle should be 6 degrees. Is this accurate (was my maths OK)?

---EDIT:

I'm a little surprised that no JBL enthusiast stepped up for this. I think my spreadsheet calculation was close but not quite right:
using Hornresp, I get these throat angles (simulating horns with 2" throat & exponential flare):
160Hz - 4.25 degrees
180Hz - 4.75 degrees
190Hz - 5 degrees

As a crude reality check (now that some parts have arrived), by sticking a ruler into the throat of a 2445J, I measure about 5 degrees.

I'm guessing this is why many users say that these drivers don't sound right unless crossed around 1000Hz, whereas John Inlow describes (and measures) them performing well < 1000Hz on his 190Hz horns. The latter have the "correct" flare rate and are really, really big: TRIPLE the length of the horns that seem to be the default options - the JBL 2380 & JBL 2385.

END EDIT---

In practice, horn manufacturers don't seem to specify throat angle, only coverage pattern, so it looks like (when buying a horn off the shelf for a 2445J), I just have to eyeball it / avoid really short horns with rapid flare.

ELLIPTICAL OPTIONS

There are some decent-looking biradial horns available quite cheaply.

Even better looking are the Faital elliptical tractrix horn, LTH142* and there are some no-name equivalents (which look exactly alike) for $25 on ebay, e.g. this:
http://www.ebay.com/itm/9-x-14-Square-1-5-Bolt-On-Horn-For-Many-1-5-Exit-Driver-/252134276208?hash=item3ab45fbc70:g:ydQAAOSwunJWE8HI
...however, these are only in 1" and 1.5" throats.

Is there anything similar elliptical horn that would be appropriate for a 2445J (2" throat)? I'd love to get some good-but-economical off the shelf horns and save a lot of time vs. building them myself.

---EDIT:

After ruling out some boutique options (due to high cost & shipping time), I ordered some relatively large but otherwise standard biradial horns.

I'll either use these while I build the ultimate horn, or just do some tweaks (like tacking on a large mouth roundover), and call it a day.

END EDIT---

BACKGROUND TO QUESTIONS:

I've made some impulse purchases recently, so now I have

2x EV 18"
2x Faital 12"
2x JBL 2"
...which could be the foundation of a decent 4-way home hifi

*the Faital has no corners / more even & gradual expansion, so as well as looking sweet, it seems theoretically better than a 4-walled biradial. Not trying to be a genius or start a horn theory war :)

This post is made possible by the generous support of people like you and our sponsors:

Topic - Horn for 2445J - throat angle? Elliptical options? - hollowboy 20:32:23 01/01/16 (0)

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.