Tapped Horn For Car

[Henkjan]

I was thinking of placing it on the floor behind the driver's seat, to double as a footrest for my 4 year old daughter outside dimensions would be approx 40*30*25 (l*w*h) cm.

[mwmkravchenko]

Hello Henkjan

What you are proposing is well within the space available. I have to work the rest of today. Something about paying bills

But tonight I will crunch the numbers and post something that may help you.

Mark

[Henkjan]

cool! thanks a lot.

[Cordraconis]

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.

[mwmkravchenko]

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

[mwmkravchenko]

The box viewed from the top.


The woofer supreemo.





Woofer from the top




LAYOUT




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

[dangus]

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.

[Volenti]

Originally posted by dangus
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.

[Henkjan]

Originally posted by mwmkravchenko
..... and made the following. The small puppy. It's a Henkjan special.

I feel flattered

Originally posted by mwmkravchenko
or for our metric friends 419.1 mm x 336.5mm x 228.6 mm
......
The box viewed from the top.

so you even managed to get two woofers in at that size!

[mwmkravchenko]

Originally posted by dangus
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