Car speaker box using a 'Folded Horn' design

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Picture of Car speaker box using a 'Folded Horn' design
vibe black death qb69 750 x 750.gif

vibe black death qb69 750 x 750.gifThis project came about because a friend of mine sold me some great Vibe speakers real cheap that needed repairing.

Folded Horn speakers work like a trumpet in that the sound comes out of an expanding tube/box. To make it fit into small spaces the tube can be folded. As long as the fold continues to get wider then it has a chance of working.

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Step 1:

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 The rubber surround had split in a number of places. So I repaired the splits by using a rubber/latex glue called Copydex together with a very thin but strong rubberised cloth cut from a cheap glasses drawstring case/bag.

This is a view of the gluing. Several layers were added, but not too much as to restrict the speaker moving. Its not very pretty but it works, it takes 110 watts RMS with ease.

Step 2: Cab Design

Picture of Cab Design


The design of the cabinet was inspired by cabs like this one shown at 

Mine had to fit in the limited space of the back of the car but I still wanted it to shake everything. I have heard folded horn speakers before and I knew that they could do that.

Folded Horn speakers work like a trumpet in that the sound comes out of an expanding tube/box. To make it fit into small spaces the tube can be folded. As long as the fold continues to get wider then it has a chance of working. There are formulas for this but I didn’t/can’t use them.

There are loads of these ideas on the net. A good place to start is -
dchev1 year ago
I'm sure there's a term for it, but wouldn't this terrible box design just give you some kind of insane amount of delay between the sound coming off the front and the sound from the rear? I've seen folded horn subs before and this isn't right.
8ohms141 year ago
nice looking speakers u got wattag and independince?
rimar20002 years ago
This seems an impressive project, I want to make one.

But I wonder if you don't lost an important part of stereo effect. It is to say, the channels separation.
blueskink (author)  rimar20002 years ago
Yep, you do lose a bit, the back seat passengers get the best deal, but the original car speakers are also connected to the music source, so they put back the stereo and the limited high frequencies.
Perhaps the loss would be somewhat less if you manage for leaving mainly bass thru folded horn. That could be achieve reinforcing the inner filling of the walls, so that absorb the treble.

Mind you, I'm guessing, would have to be tested in order to be sure.
A true folded horn (which this is not) or transmission line acts like an acoustical filter and filters out much of the high frequencies. Fibre fill, and the like is not used to absorb high frequencies, but to reduce internal reflections. Some theory suggests that fill in an enclosure design as suggested would actually ruin the way the acoustics work.

Also there would be no "loss of stereo separation" here, since low frequencies are omnidirectional, and quite long, which goes along with the acoustic filter that I mentioned already.

The stereo separation effect that our minds recognize come from much higher frequencies than what would be passed through an enclosure design like this, from the back wave of the speaker.

fwater2 years ago
This not a folded horn. It's some sort of transmission line based on a wild guess and the idea that it looks vaguely familiar to something the author saw once. Just imagine the amount of slammin bass, yo, if there was a single ounce of reasoning in the layout...

This is meant to instruct people on how to produce something useful. It will result in dismal performance (one-note bass, massive group delay and distortion).
I agree with this.
Folded Horn uses the front wave of the loudspeaker, not the rear wave. This is sorta based on a transmission line that uses the rear wave of the loudspeaker. The problem with the folded horn and transmission line designs is that they are not very forgiving, and need to be designed specifically for the drivers being used, among other requirements.
jklosowski2 years ago
Good call on the deckert design, Bummer hid setup didnt suit your space needs. i have had the chance to be privvy to 3 of thode builds and WOW ! impressive. Kudos on taking his design a step further .

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