A Tapped Horn Experiment

[Rich Schenk]

This is what I think of when I see folded horns

[Triticum Agricolam]

This is what I think of when I see folded horn

That thing certainty is interesting. I like how the guy bolts the door shut. With what he had done to it it's not really a vehicle any more.

[bassfreak85]

how does it sound? got some cancellation issues?

[bassfreak85]

BTW that looks KICKASS!

[Patrick Bateman]

Richard Clark and David Navone built this in the 90s:

It was in an accident, and they never competed with it.

I always wondered if that was a story though. Because when I look at those pics, it seems like you'd lose a ton of SPL from the flexing of the walls. IE, you could be running the biggest sub in the world with the biggest amp in the world, and if the structure isn't rigid it's not going to get loud.

[Jhunt94]

didn't they test it and it basically tried to shake the vehicle apart?

[Triticum Agricolam]

Here's the frequency response of a ported box versus a tapped horn. I set the box size to be equal, and tuned both of them to the same frequency. You can see that the efficiency is virtually identical. This is especially easy to do with transmission lines; I can make a transmission line that has the *exact* same response curve and efficiency as a ported box of equal size.

There were a few years where I believe that a horn had an efficiency advantage over other box types, but it's just not true. Hoffman's Iron Law doesn't bend, and efficiency is simply tied to box size. (Of course, horns DO WIN when you make them bigger than ported boxes; the Danley BC-218 is the size of a small car and weighs a quarter of a ton.)

Where things get interesting are at high power, because that's when port compression plays a big role, and thermal effects too. Wayne Parham's work is really interesting; he showed that doubling the power only added about 1dB at the limits. (He literally cranked up the power until the drivers melted down.)

By the way, the ported box in that sim is one half of a PK Sound CX800 and the tapped horn in that sim is the tapped horn in my car.

I totally agree with you when it comes to ported boxes and T-lines. Which is one of reasons I think T-lines for car audio usage are a waste as least 90% of the time.

When it comes to comparing horns to ported boxes, you don't have me convinced. My challenge was to match the output of MY horn, not yours :-)

Here is the HornResp input:

https://dl.dropboxusercontent.com/u/1642665/E-10Horn.txt

See if you can match the efficiency and frequency response to that with a ported box. To keep it fair, you also have to keep cone excursion under 14 mm and port velocity under 22 m/sec above 27 Hz on 45 volts.

[Triticum Agricolam]

how does it sound? got some cancellation issues?

It sounds great. Probably my favorite car audio sub thus far.

I'm sure I do have some cancellation issues with it in the vehicle. I just threw it in there for testing and haven't put any effort into dealing with cancellation or reflections.

[Patrick Bateman]

Here's the frequency response of a ported box versus a tapped horn. I set the box size to be equal, and tuned both of them to the same frequency. You can see that the efficiency is virtually identical. This is especially easy to do with transmission lines; I can make a transmission line that has the *exact* same response curve and efficiency as a ported box of equal size.

There were a few years where I believe that a horn had an efficiency advantage over other box types, but it's just not true. Hoffman's Iron Law doesn't bend, and efficiency is simply tied to box size. (Of course, horns DO WIN when you make them bigger than ported boxes; the Danley BC-218 is the size of a small car and weighs a quarter of a ton.)

Where things get interesting are at high power, because that's when port compression plays a big role, and thermal effects too. Wayne Parham's work is really interesting; he showed that doubling the power only added about 1dB at the limits. (He literally cranked up the power until the drivers melted down.)

By the way, the ported box in that sim is one half of a PK Sound CX800 and the tapped horn in that sim is the tapped horn in my car.

I totally agree with you when it comes to ported boxes and T-lines. Which is one of reasons I think T-lines for car audio usage are a waste as least 90% of the time.

When it comes to comparing horns to ported boxes, you don't have me convinced. My challenge was to match the output of MY horn, not yours :-)

Here is the HornResp input:

https://dl.dropboxusercontent.com/u/1642665/E-10Horn.txt

See if you can match the efficiency and frequency response to that with a ported box. To keep it fair, you also have to keep cone excursion under 14 mm and port velocity under 22 m/sec above 27 Hz on 45 volts.

Here ya go.

Grey line is your tapped horn.

Black line is a vented box using the same woofer and the same size box.

Here's some random observations about the two:

1) The ported box is way WAY bigger than a "conventional" ported box, and that's why the response is so peaky. Basically I made the port HYOOOOOGE to raise it's efficiency. The port is five decibels louder than the driver itself; in a conventional ported box the port output is the same, which is why a conventional ported box has flat response and this one doesn't. But if you want the absolute maximum output the driver can deliver, and you don't want to make a horn, you can make a ported box with a really REALLY huge port.

2) The excursion limits of the ported box and the tapped horn will be identical, because the low frequency response is the same.

3) Obviously, the TH will be a lot more 'musical', it has wider bandwidth and superior phase response. (The tapped horn only has 90 degrees of phase shift, the ported has 180.)

4) I would speculate that the ported box would have much lower port compression, because the port on this thing is HUGE. It's diameter is about 18"!

5) I tried to 'fill in' that trough at 50hz. It wasn't possible to do it because of the phase difference. Basically the TH has half the group delay. So the output above the tuning frequency of the tapped horn isn't 100% in-phase, but it's much closer than the ported box, and that 'fills in' the trough in the tapped horn. For this reason, if I wanted to duplicate the output of your tapped horn it would be easier to do it with a front loaded horn or a transmission line. This is because those boxes are only 90 degrees out-of-phase, while a ported box is 180 degrees out-of-phase.

[Patrick Bateman]

double post, whoops