horn throats

Patrick Bateman · 9th June 2008, 11:31 PM

Who knows a lot about horn throats?

I'm working on a unity horn, and I'm having a hard time with the midrange holes in the horn. As I understand it, the holes basically act as the throat in the horn. So the holes in a unity are equivalent to the throat in a traditional horn.

The problem which I'm seeing is this:

When I use a small throat, the response is the smoothest. But when I actually built it, there's a raspy buzzing sound which makes me thing the woofer is on the verge of exploding. I checked the cone to see if it's touching the horn, and it's not. So the buzzing must be comin from the driver itself. I'm guessing the high pressure in the throat is causing the buzzing.

Sooooo -

What's the solution?

If I go with a larger throat, the response is worse (according to hornresp.)

Does the *depth* of the holes make much of a difference? Based on modeling it in hornresp, the difference between a throat that's 1/2" deep and one that's 1/4" deep is nil.

nickmckinney · 10th June 2008, 01:48 AM

Tom D would be the best to answer this of course. The Unity we did the holes were 3/4" deep plus a slight amount more from the putty put into the corners of the horn. We would smooth the holes as much as possible when making them. Here is a picture I still have floating around of one of the prototypes:

Patrick Bateman · 12th June 2008, 11:13 PM

Since the midranges are bolted right onto the surface of the horn, it turned out the mounting arrangement was the culprit.

Basically the surround on the woofers was buzzing against the side of the horn. I thought there was enough clearance, but there wasn't.

My solution was to create a gasket out of very thing cardboard, which I slipped between the woofer frame and the horn. It's very VERY thin, because hornresp shows that the best response is achieved with the smallest front chamber possible.

LineArray · 12th June 2008, 11:42 PM

Hi Patrick,

i am not a horn specialist, but as far as i understood the
unity it is a conical horn with slow rolloff at the lower end,
when attaching the tweeter only.

This is compensated by the augmenting midrange drivers.

Is it necessary to have the holes at all ?

Can one integrate some small midrange units with nearly
flat diaphragms into the wall without having holes in it ?

Maybe my idea is completely wrong ...

Patrick Bateman · 13th June 2008, 12:44 AM

responded here.

9th June 2008, 11:31 PM	#1
Patrick Bateman diyAudio Member Join Date: Oct 2006	horn throats Who knows a lot about horn throats? I'm working on a unity horn, and I'm having a hard time with the midrange holes in the horn. As I understand it, the holes basically act as the throat in the horn. So the holes in a unity are equivalent to the throat in a traditional horn. The problem which I'm seeing is this: When I use a small throat, the response is the smoothest. But when I actually built it, there's a raspy buzzing sound which makes me thing the woofer is on the verge of exploding. I checked the cone to see if it's touching the horn, and it's not. So the buzzing must be comin from the driver itself. I'm guessing the high pressure in the throat is causing the buzzing. Sooooo - What's the solution? If I go with a larger throat, the response is worse (according to hornresp.) Does the depth of the holes make much of a difference? Based on modeling it in hornresp, the difference between a throat that's 1/2" deep and one that's 1/4" deep is nil.

12th June 2008, 11:42 PM	#4
LineArray diyAudio Member Join Date: Mar 2008	Hi Patrick, i am not a horn specialist, but as far as i understood the unity it is a conical horn with slow rolloff at the lower end, when attaching the tweeter only. This is compensated by the augmenting midrange drivers. Is it necessary to have the holes at all ? Can one integrate some small midrange units with nearly flat diaphragms into the wall without having holes in it ? Maybe my idea is completely wrong ... __________________ Oliver, RFZ believer (?) www.dipol-audio.de

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10th June 2008, 01:48 AM	#2
nickmckinney diyAudio Member Join Date: May 2008	Tom D would be the best to answer this of course. The Unity we did the holes were 3/4" deep plus a slight amount more from the putty put into the corners of the horn. We would smooth the holes as much as possible when making them. Here is a picture I still have floating around of one of the prototypes:

12th June 2008, 11:13 PM	#3
Patrick Bateman diyAudio Member Join Date: Oct 2006	Since the midranges are bolted right onto the surface of the horn, it turned out the mounting arrangement was the culprit. Basically the surround on the woofers was buzzing against the side of the horn. I thought there was enough clearance, but there wasn't. My solution was to create a gasket out of very thing cardboard, which I slipped between the woofer frame and the horn. It's very VERY thin, because hornresp shows that the best response is achieved with the smallest front chamber possible.

13th June 2008, 12:44 AM	#5
Patrick Bateman diyAudio Member Join Date: Oct 2006	responded here.

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