Gaps in my horn - a major problem?

wixy · 6th September 2007, 10:56 PM

I've just applied the side panel to my backloaded horn. I used polyurethane glue as I knew this would expand and help to seal up any gaps. However, I don't think I used enough glue because their still appears to be some small gaps where the glue didn't seep out. I can seal up some of these gaps but not all because they would be impossible to access.

I'm sure the glue would be present in the middle of the joints i.e. the sound won't actually escape through any gaps, but would the gaps present a problem? They are very small, probably less than 1/2 of a mm.

planet10 · 6th September 2007, 11:10 PM

Quote:

Originally posted by wixy
would the gaps present a problem?

Likely yes.

dave

wixy · 6th September 2007, 11:19 PM

Even if the sound can't actually escape through them? And the gaps are only around an inch or so long at maximum and occur randomly? I might see if I can take a photo to illustrate.

planet10 · 6th September 2007, 11:22 PM

If the gaps don't let air thru (or short circuit the innards) then as far as the air is concerned it is not a gap. Might affect the structural rigidity of the cab thou.

dave

awhite1159 · 6th September 2007, 11:47 PM

You might try turning lights off in the room and put a drop light inside the mouth with a cover over it and also in towards the throat with a cover over it to see if any light is coming out. That would at least show external leaks. As for concern about internal folds, I had a problem with the first horn I built being a Fostex FE208 Sigma enclosure I built and was able to get most of the joints sealed by working down the throat and up the mouth. If you have an internal fold, sealing one side of the board would essentially seal the other side. Also the seam in the back since it will be up against the wall (Front firing horn?) will be out of sight. My guess is that air leaks would be more serious the closer you get to the throat because of the pressures generated but I may be wrong.

What kind of horn?

wixy · 7th September 2007, 12:00 AM

Quote:

What kind of horn?

FE208E Sigma :P

I don't think there will be any actual air leaks, but I will follow your torch idea. My concern is with the little gaps where the air will go in and then out again.

ronc · 7th September 2007, 12:18 AM

A horn is a pressure container. It holds pressure along the trip between the FC to the mouth.

Any pressure leak during the trip alters the effective performance in two ways. The first is a loss in the effective energy during the expansion and the second is the gain in untimed pressure at a later given point along the expansion. This can cause alteration of the pressure at a later point by lowering/raising/cancellation of the later timed wave.

ron

6th September 2007, 10:56 PM	#1
wixy diyAudio Member Join Date: Mar 2006 Location: Melbourne, Australia	Gaps in my horn - a major problem? I've just applied the side panel to my backloaded horn. I used polyurethane glue as I knew this would expand and help to seal up any gaps. However, I don't think I used enough glue because their still appears to be some small gaps where the glue didn't seep out. I can seal up some of these gaps but not all because they would be impossible to access. I'm sure the glue would be present in the middle of the joints i.e. the sound won't actually escape through any gaps, but would the gaps present a problem? They are very small, probably less than 1/2 of a mm.

6th September 2007, 11:22 PM	#4
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	If the gaps don't let air thru (or short circuit the innards) then as far as the air is concerned it is not a gap. Might affect the structural rigidity of the cab thou. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

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6th September 2007, 11:19 PM	#3
wixy diyAudio Member Join Date: Mar 2006 Location: Melbourne, Australia	Even if the sound can't actually escape through them? And the gaps are only around an inch or so long at maximum and occur randomly? I might see if I can take a photo to illustrate.

6th September 2007, 11:47 PM	#5
awhite1159 diyAudio Member Join Date: Jul 2007	You might try turning lights off in the room and put a drop light inside the mouth with a cover over it and also in towards the throat with a cover over it to see if any light is coming out. That would at least show external leaks. As for concern about internal folds, I had a problem with the first horn I built being a Fostex FE208 Sigma enclosure I built and was able to get most of the joints sealed by working down the throat and up the mouth. If you have an internal fold, sealing one side of the board would essentially seal the other side. Also the seam in the back since it will be up against the wall (Front firing horn?) will be out of sight. My guess is that air leaks would be more serious the closer you get to the throat because of the pressures generated but I may be wrong. What kind of horn?

7th September 2007, 12:18 AM	#7
ronc diyAudio Member Join Date: Mar 2003	A horn is a pressure container. It holds pressure along the trip between the FC to the mouth. Any pressure leak during the trip alters the effective performance in two ways. The first is a loss in the effective energy during the expansion and the second is the gain in untimed pressure at a later given point along the expansion. This can cause alteration of the pressure at a later point by lowering/raising/cancellation of the later timed wave. ron

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