# Horn transistion to dash



## jimbno1 (Apr 14, 2008)

I see a lot of comments concerning the smooth transistion from horn mouth to the dash "using the dash as an extension of the horn mouth". I think I understand the concept but lack the information exactly how to implement it. 

I know some of you folks are competing and do not want to give away your secrets. Could some of you who do not compete share your expertise?

For instance, what materials can be used effectively? I have seen pics of PVC pipe on the upper and lower edge, some times it looks looks like felt or carpet is used, and I believe some even used cardboard. Is it just as simple as having material between the horn mouth and the bottom of the dash? Or is there shaping that is critical? 

Does the horn have to be flush with the dash? 

If someone has a pratical step by step how they handled the dash transistion that would be helpful. I know it will be vehicle specific but maybe the concept could be put to use in any vehicle.


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## Patrick Bateman (Sep 11, 2006)

jimbno1 said:


> I see a lot of comments concerning the smooth transistion from horn mouth to the dash "using the dash as an extension of the horn mouth". I think I understand the concept but lack the information exactly how to implement it.
> 
> I know some of you folks are competing and do not want to give away your secrets. Could some of you who do not compete share your expertise?
> 
> ...


Have you been to the ocean? Put a rock on the beach, then watch what happens when a wave comes riding up onto the beach. That rock will 'break up' the incoming wave, creating eddies and pools on the other side of the rock.

Sound works a lot like that. When the transition from your horns isn't terminated smoothly, the wavefront coming off of the diaphragm is broken up.

The closer that the incongruity is to the diaphragm, the worse that it is.

Check out some of my threads on diffraction, I have some illustrations that demonstrate how this works.

The spherical tweeter thread works on the exact same principle. Diffraction sucks.


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## Mic10is (Aug 20, 2007)

it can be as easy and filling the gap between the underdash and horn with cardboard, wood, fiberglass or any other material.

the idea is not to have gaps between the horn mouth and the underdash.

you also dont want to do any materials that will absorb either. as most a piece of trunk liner carpet. any thicker than that it can start absorbing higher frequencies.


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## DanMan (Jul 18, 2008)

My driver side horn had a sizable gap to the dash. I had been procrastinating doing something about it because I wanted to "do it right".

Recently I decided to just put some duct tape on it. It was probably the best tweak I have done in a while. It noticeably raised the stage and cleaned up the image a bit. 

Do it for the psycho-acoustic factor if nothing else.


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## jimbno1 (Apr 14, 2008)

I knew duct tape could fix anything.


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## DanMan (Jul 18, 2008)

jimbno1 said:


> I knew duct tape could fix anything.


There you have it.


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## jimbno1 (Apr 14, 2008)

Anybody have any good pics or techniques?


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## Patrick Bateman (Sep 11, 2006)

DanMan said:


> My driver side horn had a sizable gap to the dash. I had been procrastinating doing something about it because I wanted to "do it right".
> 
> Recently I decided to just put some duct tape on it. It was probably the best tweak I have done in a while. It noticeably raised the stage and cleaned up the image a bit.
> 
> Do it for the psycho-acoustic factor if nothing else.


If I'm not mistaken, the same principles which govern aerodynamics operate on sound waves too. A few years back The Discovery Channel did a special on Lance Armstrong, and using a wind tunnel they demonstrated that something as subtle as raising a finger to shift a gear reduced the aerodynamics of his bicycle.

It's crazy stuff - even the smallest detail makes a difference when it comes to diffraction.


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## T3mpest (Dec 25, 2005)

Duck tape is the BEST thing to use that I have found.. In my car it allows me to get perfect coupling. The horns if touching my firewall reach up to just behind where the little 1/2 gap in my upper dash is. I can put a piece of ductape with one end inside the horn and the other end covering up the gap, running sidways so I can do it with just one long strip. It covers the hold, perfectly molds to the car and the edge on the tape is so rediculously tiny that I doubt any sound diffracts backwards from the .00000002inch thickness of the tape. I used to have a HUGE hole in my driver side soundstage, cleared it right up!


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## Patrick Bateman (Sep 11, 2006)

T3mpest said:


> Duck tape is the BEST thing to use that I have found.. In my car it allows me to get perfect coupling. The horns if touching my firewall reach up to just behind where the little 1/2 gap in my upper dash is. I can put a piece of ductape with one end inside the horn and the other end covering up the gap, running sidways so I can do it with just one long strip. It covers the hold, perfectly molds to the car and the edge on the tape is so rediculously tiny that I doubt any sound diffracts backwards from the .00000002inch thickness of the tape. I used to have a HUGE hole in my driver side soundstage, cleared it right up!


This stuff is straight up evil. I've seriously been trying to remove the glue residue from this for four years now:


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## Arclight (Apr 29, 2011)

On the drivers side, I used cardboard w/ glued on carpet to bridge the gap between the horn and the lower portion of the dash. For the passenger side, I used a narron/long piece of sticky felt since the tops of the horns practically touched the bottom of the glovebox lid. 

As stated above, it's critical that the transition between the horn and the lower dash is as seamless as possible. I would have never thought of duct tape...


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## nubz69 (Aug 27, 2005)

Although some people swear by molding to the underside of the dash other school of thought is to get your horns as far back as possible to help equalize wavelengths. As usual YRMV.


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## DanMan (Jul 18, 2008)

nubz69 said:


> Although some people swear by molding to the underside of the dash other school of thought is to get your horns as far back as possible to help equalize wavelengths. As usual YRMV.


I think attention should still be given to the transition from horn > dash, or horn > underdash > dash.


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## Patrick Bateman (Sep 11, 2006)

nubz69 said:


> Although some people swear by molding to the underside of the dash other school of thought is to get your horns as far back as possible to help equalize wavelengths. As usual YRMV.


Another benefit of pushing the horns waaaaaaay back is that it improves the transition to the dash, because the dash extends the curve.

You can try this in your room by listening to the horns in free air, then listen to the horns sitting on a flat surface, like a table.

When they're sitting on the table you should notice that the lower octaves sound a lot cleaner, because the HOMs are reduced by improving the horn termination.


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## TokoSpeaker (Nov 12, 2010)

jimbno1 said:


> Anybody have any good pics or techniques?


Same above, Anybody have any good pics or techniques?


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## veritasz34 (Jul 25, 2011)

I always got the best results when my horns was mounted on the lower edge of the dash with out any gaps. In Dallas at finals one of my horns came loose from the dash during the drive (Bumpy roads in Arkansas) and it had a 1/4-1/2 inch gap on the passenger side that I DIDN'T catch until it was too late..I paid the price for it too..9th place finish at finals....


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