Tapped Horn For Car

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I've been messing with this for a while. I got my inspiration from the smallest tapped horn thread. It seems that if you design a horn with a falling response of about 12 db/octave starting at 10 hz you will end up with a pretty flat response once the puppy is in the car.

I worked up an example with some CSS SDX7 drivers. They are quite a bit like to 6.5 inch Tang Band stuff only made a little better. The specs are measured and the simulations are linked below.

Mark

http://i407.photobucket.com/albums/pp160/mwmkravchenko/2DriverCSSSDX7TappedHornCarSubMa-1.png
http://i407.photobucket.com/albums/pp160/mwmkravchenko/2DriverCSSSDX7TappedHornCarSubMaxim.png
http://i407.photobucket.com/albums/pp160/mwmkravchenko/MaximallyFlatincarresponseTappedhor.png

P.S. If anyone knows how to properly embed pictures into posts please let me know how.
 
I've got a few ideas I'm messing around with too. Modeling non-flat responses is trickier than it looks. I probably should measure the cabin gain curve of my car to get some sort of idea of what response curve to target.

As far as posting pictures - all I do is attach the file by selecting it in the attach file dialog below the edit window.

Other people use web-hosted images, I think that is done with the IMG button, though I have never posted image files that way.
 

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Response curve for the previous model. It is only a 40L box, it has the falling response I was after, but I do not think I'll waste time building it. The impulse response looks terrible (rings like a bell). Back to the drawing board.....
 

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Ok now that the light bulb is finally turned on

This particular box is about 95 litres. Or around 3 1/2 cubic feet. As dimensions take something like this. I.D. 8"x 24"x 30" Small enough to fit in the back of my Toyota Matrix. The size I chose is to go all the way down to the basement for listening to Organ music and the like. There are obviously much smaller combinations.

Normal music cuts out around 40hz so I'll post one for that shortly. I'm going to build the one I simmed first. It will replace the tuba 18 that is currently hogging all my space in the back. The tuba 18 is just great if you are listening to anything above 50hz. I rapidly dies if you ask it to produce anything below that. It only gives a hint of 30hz which really sucks.

This tapped horn will be what the doctor ordered. More or less flat from 100hz down to about 18hz.

Mark

An externally hosted image should be here but it was not working when we last tested it.

Impulse response. Not to bad for a subwoofer.


An externally hosted image should be here but it was not working when we last tested it.


With a little bit of power we get a lot of noise.
 
Things that don't bump in the car

A quick check on the realities. This CSS SDX7 driver is rather amazing. You get more efficiency and X-max than anything I know of within the price range. Plus the second design is almost a qualifier for the smallest tapped horn thread. Less than a cubic foot. actually with a quick calculation of Inside Dimensions of 20.3 cm x 30.48cm x 32 cm. Or 8"x 12" x 13" that is pretty small. And the SPL's available from a single nominal 6.5" driver are Pretty Darn Good!

Mark
 
Very interesting idea.

One could also use an ELF subwoofer design (that is, a sealed box driven below Fs) to also get the same -12dB per octave response. It'd be interesting to compare some of these designs, but I'd hazard a guess that the tapped horn will come out as the best value, but multiple sdx7 ELF subs might be best on a SPL per box volume basis for 40hz and up.
 
19 litres plus one driver plus the wood to make the box

Hello Henkjan

The design is for one driver. The total size with the driver volume displacement and the box volume displacement would be over 21 maybe 22 liters.

Two drivers will give a boost of about 3 db mechanical efficiency and 3db in potential electrical efficiency. Depending on how the drivers are wired. Series or parallel would make the difference. And according to real world results expect 3 to 4 db over a broad bandwidth.

I could simulate two drivers but the box will increase in size. Do you have a maximum size or is this just fooling around a bit?

Mark
 
A little bit OT, but here it goes:

For a few weeks I have been trying to squeeze a 30Hz basshorn into a 130L volume to put in the back of my car, a VW Golf III. (10 dB rising curve from 30-125Hz for cabin gain.)
Yesterday I finally came up with a folding to squeeze it all in. Oddly enough it is about 100L large in HornResp, yet it completely fills the volume and this was the most eff folding scheme I could find!

I'll post it here since this might be a good folding for a tapped horn (which my driver is not suitable for anyway in this freq range)

http://users.telenet.be/Hellhouse/public/carbasshorn/

It is completely on the left, where the other schemes were some early tryouts that proved impractical.
Note the "ribbon" measuring tool in yellow: I have found out this is a very fast and easy way to find the horn length from a given point, and speeds up the folding process greatly.
 
This working for a living SUCKS!

Tonight turned into 5 nights.

Anyway I spent a couple of hours in the shop tonight and made the following. The small puppy. It's a Henkjan special.

I'm making a rather interesting built in cabinet for a client and the material I'm using is the proceeds from the old one. It's actually HDF. Hard as a rock. But it cuts nice and glues up wonderfully. I almost have enough to make the one for my car to. That is the first one I posted. The one in the pictures is probably going to be a bit more user friendly. The size is 16.5" x 13.25" x 9" or for our metric friends 419.1 mm x 336.5mm x 228.6 mm

It's not glued up yet but every piece is cut out to fit and the holes for the drivers are setup perfectly.

If you guts are interested I could post some plan or the other. I took a whole wack load of pics. They are up on photobucket. So I'll post the interesting ones and if you are a little interested snoop around and look at the others.

Mark
 
Box over view

The box viewed from the top.
An externally hosted image should be here but it was not working when we last tested it.


The woofer supreemo.


An externally hosted image should be here but it was not working when we last tested it.



Woofer from the top


An externally hosted image should be here but it was not working when we last tested it.


LAYOUT

An externally hosted image should be here but it was not working when we last tested it.



The darker line is optimal layout shape. The straight lines are the compromise to get the woofers into a boc and still keep the shape.

David McBean is owed a great deal of thanks. I would have had a difficult time without his wonderfull software.

Mark

An externally hosted image should be here but it was not working when we last tested it.
 
dangus said:
How does the "transfer function" or "cabin gain" of the car interior affect the performance of a horn? I'd figure that at the low frequencies, a sealed box would be better.

Well mostly it just adds to it just like it would to a sealed/ported enclosure. However, all though I haven't built a tapped horn for a car (yet) I have built many 1/4wave enclosures, and they tend to drop in frequency when loaded in a vehicle, a large one I built specifically for SPL competition had an impedance peak 10hz lower inside the car then outside (measured).

I suspect a large tapped horn would behave in a similar manner.
 
Re: Box over view

mwmkravchenko said:
..... and made the following. The small puppy. It's a Henkjan special.
I feel flattered :D


mwmkravchenko said:
or for our metric friends 419.1 mm x 336.5mm x 228.6 mm
......
The box viewed from the top.
An externally hosted image should be here but it was not working when we last tested it.
so you even managed to get two woofers in at that size! :smash:
 
Al you gain in a car is ?

dangus said:
How does the "transfer function" or "cabin gain" of the car interior affect the performance of a horn? I'd figure that at the low frequencies, a sealed box would be better.


Hi Dangus

There are two attributes working hand in hand here. The efficiency of a horn loaded driver/box combination. Look at the posts for the small horn. The max SPL is at 100 watts. It's almost 130 db and Horn Response does not factor in cabin gain. You can easily add on 3 to 5 db at 100 hz and 10 to 12 db at 30 hz. Try that with any other car sub! The cabin gain or what ever you would care to call it ( transfer function I believe is the better term ) works to give you a naturally reinforcing increase in volume as you go lower in frequency.

How does this help with a horn? Incredibly smaller mouth size for one thing. The tapped horn cconcept is almost 1/2 the length of a competitive conical horn. This horn pictured above will smack down the current 18" cube Tuba sub in my car. I drive the tuba sub with my pioneer head unit with the rear channels bridged and get 22 real watts. Those 22 real watts give peaks of 122db. The problem for me is that the Tuba 18 poops out at 50hz and rapidly rolls off below that. Not low enough for big classical music. The little sub rolls off around 35 hz. That is in normal conditions. In a car I don't know yet. I will measure this thing up carefully. I will also post spl measurements using my Rat shack meter which is within 1 db accuracy of a Bruel and Kajer last time I had it compared side by each. So I generally trust it. The one watt one meter will have to be done out side at a wall ground building junction. 1/2 pi measurement that can be massaged by adding on the apprpriate db gain in a car or home.


Mark
 
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