The Smallest Tapped Horn

[Patrick Bateman]

Originally posted by MikeHunt79

If you don't mind me asking, what do you have in your car now?

I currently have a dual driver autotuba in mine, and while is sounds great, it is a little large as it fills my entire boot (trunk)!

I was wondering if there is something similar which is smaller yet gives the same rising response of the AT?

I was thinking maybe a TH tuned to 60Hz, maybe with a 8" MCM but maybe a 12" driver would work better?

I used to have a three hour commute everyday, and I was running Unity horns up front. In the trunk I had an autotuba clone for a while, and then I switched to a pair of eights in a severely undersized front-loaded horn.

I documented most of it over at audiogroupforum.com.

It's really hard to improve on the autotuba; I've tried half a dozen times. If you make it any smaller, the response goes to hell. To get the F3 lower, you have to make it a LOT bigger.

I still have the clone in my garage, and I'm hoping to measure both the tapped horn and the autotuba clone head-to-head.

[David_Web]

Looking at a LP at 100Hz iFFT (IR) the difference might not be significant in the time domain. Instead of 4 spikes it is a lump just like on a TH with one speaker. Even with two 15" drives after one another. Wavelength is just too long for the IR to get smeared.

The strength of the TH is that it does not continue to resonate much beyond the initial 2-3 cycles that is takes to "fill" the TH.
Unlike ported or even closed boxes that happily continues to give output 5-10 cycles away.

I don't get the same bandwidth increase like you though.
However I do use one vs two 15" drive in a 210L vs 400L TH.
So it might only apply to smaller drives. I don't know.

Please keep testing as it is very interesting.

[Patrick Bateman]

Originally posted by David_Web
Looking at a LP at 100Hz iFFT (IR) the difference might not be significant in the time domain. Instead of 4 spikes it is a lump just like on a TH with one speaker. Even with two 15" drives after one another. Wavelength is just too long for the IR to get smeared.

The strength of the TH is that it does not continue to resonate much beyond the initial 2-3 cycles that is takes to "fill" the TH.
Unlike ported or even closed boxes that happily continues to give output 5-10 cycles away.

I don't get the same bandwidth increase like you though.
However I do use one vs two 15" drive in a 210L vs 400L TH.
So it might only apply to smaller drives. I don't know.

Please keep testing as it is very interesting.

I had mixed results as well. Here's a few things that I tried:

#1 - I started out with a cabinet that's very similar to a Danley TH-Mini. Instead of a twelve, it uses two eights. It has a dramatic flare at the mouth. In this cabinet, I saw substantial improvements in bandwidth and smoothness with two drivers, and to a lesser degree with four.

#2 - I tried modeling a tapped horn with a modest flare. In my experience, these enclosures are easy to build, but suffer from a lot of nasty resonances. With multiple woofers, there was no real improvement. In some cases it was much worse.

#3 - One idea I had was that staggering the woofers using the golden ratio (1.62) might smooth out resonances. This seems to be promising; I was able to achieve a very wide bandwidth by using four woofers which use a spacing ratio that matches the golden ratio. The only drawback is that the F3 rises quite a bit.

Just some food for thought! The use of multiple woofers seems to extend the bandwidth without hurting the efficiency.

[Patrick Bateman]

Originally posted by Patrick Bateman


I had mixed results as well. Here's a few things that I tried:

#1 - I started out with a cabinet that's very similar to a Danley TH-Mini. Instead of a twelve, it uses two eights. It has a dramatic flare at the mouth. In this cabinet, I saw substantial improvements in bandwidth and smoothness with two drivers, and to a lesser degree with four.

#2 - I tried modeling a tapped horn with a modest flare. In my experience, these enclosures are easy to build, but suffer from a lot of nasty resonances. With multiple woofers, there was no real improvement. In some cases it was much worse.

#3 - One idea I had was that staggering the woofers using the golden ratio (1.62) might smooth out resonances. This seems to be promising; I was able to achieve a very wide bandwidth by using four woofers which use a spacing ratio that matches the golden ratio. The only drawback is that the F3 rises quite a bit.

Just some food for thought! The use of multiple woofers seems to extend the bandwidth without hurting the efficiency. It does seem to require a different kind of driver though. The high FS / moderately high QTS drivers that work so well in tapped horns seem to suffer from a lack of bandwidth. I had better results with drivers that offered a EBP. I guess that's why they call it EBP?

[MikeHunt79]

Originally posted by Patrick Bateman


I used to have a three hour commute everyday, and I was running Unity horns up front. In the trunk I had an autotuba clone for a while, and then I switched to a pair of eights in a severely undersized front-loaded horn.

I document .d most of it over at audiogroupforum.com.

It's really hard to improve on the autotuba; I've tried half a dozen times. If you make it any smaller, the response goes to hell. To get the F3 lower, you have to make it a LOT bigger.

I still have the clone in my garage, and I'm hoping to measure both the tapped horn and the autotuba clone head-to-head.

Unity horns in a car, that's a new one on me! I'll take a look at audiogroupforum.com, I'm intrigued.

I do have the autotuba plans and sketchup models, so it would be pretty easy to work out the dimensions so I could sim it in Hornresp, but as you said, it's hard to get the same rising response, especially with a Tapped horn.

Right now I don't mind having a massive sub in the boot, so I can keep it in there while I experiment a little with TH's.

I'd be interested to see your measurements of the clone against the TH once they're done, I keep meaning to try my dual driver autotuba outside once I get ARTA up and running...

[Patrick Bateman]

Originally posted by MikeHunt79

Unity horns in a car, that's a new one on me! I'll take a look at audiogroupforum.com, I'm intrigued.

I do have the autotuba plans and sketchup models, so it would be pretty easy to work out the dimensions so I could sim it in Hornresp, but as you said, it's hard to get the same rising response, especially with a Tapped horn.

Right now I don't mind having a massive sub in the boot, so I can keep it in there while I experiment a little with TH's.

I'd be interested to see your measurements of the clone against the TH once they're done, I keep meaning to try my dual driver autotuba outside once I get ARTA up and running...

I love my home speakers (Gedlee Summas) but the Unities can do one thing that the Summas can't. The unities sound amazing even if you're seated within a few feet of the waveguide, while the Summas really need a bit of distance to "integrate" fully. I believe this is because there's a fifteen inch gap between the woofer and the tweeter in the Summa, and in the unity the gap is just three inches.

So what does this have to do with a car?

Well, in a car you're seated way too close to the speakers. So the tight integration of the midrange and the tweeter has a lot of benefits in a car.

I see a lot of guys trying to cram eight inch woofers into the front stage of their cars, and it's a dumb idea. It's impossible to integrate, because you're so close to the woofers.

[Patrick Bateman]

The glue has barely dried on the 12" tapped horn, but I wanted to measure it real quick. Here's a pic:



The good news is that we see two deep impedance troughs, which indicate that this is behaving like a tapped horn should. The bad news is that they're about 15% too high.

I took these measurements with the tapped horn up against a wall, and also in the middle of the floor of my listening room. Didn't seem to make a difference in the impedance plot.

At first I was worried that my hypothesis that the mouth extends into the room was incorrect. I think the jury is still out though. I messed around with the parameters in Akabak a bit, and the mismatch between the measured results and the simulated results appears to have more to do with the length of the line inside of the horn, not outside.

I'm going to go hook it up in the car, and I'll probably do some electrical and acoustical measurements of that setup in the next week or two.

[hm]

Hello,

if you take two different horns you can reduce the IMP
look my Subfanfare,
if you take 4 (2+2) you can reduce it more
and you get 4 Ohm
here single imp of the long and short horn and the sum
driver WAL 416 Mivoc.

you get a cleaner bass with better contour,
enclosure movement is smaller because no big pressure changes,
and the AMP likes it much more, here below 50 Hz no IMP peak
but down to 35 Hz.

[Patrick Bateman]

Posted some subjective observations here:

http://www.diymobileaudio.com/forum/...tml#post744111

In a nutshell, this thing plays really loud. Definitely a huge improvement over the sonotube tapped horn that I described in my "tapped horn for dummies" thread.

It also has huge bandwidth; it's playing up to 2khz easy, maybe higher. (haven't done any acoustice measurements... yet.)

[CrazyTubax86]

Let us know as soon as you get some measurements. In car and in the open.