back loaded horn from pvc?

[Cramerklontz]

i have a pair of Dayton Audio PC83-8 burning a hole in my pocket. the speaker cutout is almost exactly the same as 3” pvc so i thought no brainer, lets make a transmission line to play with. then as always, i got to thinking to much. there are these T joints at the home depot. that would double the area everytime i doubled up on the pipes. that sounds like a horn to me. so my question is, with 14 T joints i could double the area of one speaker 3 times and make the length in between each doubling anything i want, would this make a decent backloaded horn? doubling again would be cost prohibitive. or would it be more like an expanding tapered TL? which seems like a bad idea. i wouldn’t be getting the benefit of the end of the horn pointed at the listener, but i was thinking id get some benefit from the impedance coupling with the room. i could probably buy all the pipe and fittings for 75-100usd.

 

[claudiogan]

i have a pair of Dayton Audio PC83-8 burning a hole in my pocket. the speaker cutout is almost exactly the same as 3” pvc so i thought no brainer, lets make a transmission line to play with. then as always, i got to thinking to much. there are these T joints at the home depot. that would double the area everytime i doubled up on the pipes. that sounds like a horn to me. so my question is, with 14 T joints i could double the area of one speaker 3 times and make the length in between each doubling anything i want, would this make a decent backloaded horn? doubling again would be cost prohibitive. or would it be more like an expanding tapered TL? which seems like a bad idea. i wouldn’t be getting the benefit of the end of the horn pointed at the listener, but i was thinking id get some benefit from the impedance coupling with the room. i could probably buy all the pipe and fittings for 75-100usd.

If you want to try a very economical and omnidirectional frontal acoustic load you can use the 22C7 project by changing the lengths of the 7 25 mm pvc pipes with the 773, 853, 942, 1040, 1148, 1268, 1400 mm series. The lengths can be reduced proportionately, the bass would be reduced. I do not recommend the increase, the bass would increase but the highs would end up above the listener's head.

With 20-30 euros complete the diffusers using less glue than with the T tree.

 

[Cramerklontz]

that looks cool. thanks for the reply.

 

[jjasniew]

I've oft dreamed of making such a pipe array. However I wonder if "Karlsonating" each pipe would make each a little more wide-band? Something like in the picture from the net below?

 

[Audio-Lego]

Been there, done that.

I've made all sorts of things out of ABS pipe. Most success came with quarter-wave resonators.
Just as you have wondered about a back horn from pipe, I did as well. I had some parts for 1/4 wave speakers and combined them with a bunch of 45 degree tees to make the horn flare.
The recipe was:
A 90 degree tee with a baffle for a Fostex FE 108ez at one opening, speaker terminals on a plug at the opposing opening and the start of the horn on the 90 deg opening.
A one meter piece of 4in ABS pipe which had an internal expansion plug that tapered from 25% opening to 100% opening.
A half meter U shaped section of straight pipe.
Then the horn flare, 7 45 degree tees coupled 1 to 2 to 4 to 8 openings.
It was totally goofy looking, you had to twist the tees in all directions to make them not interfere with each other. Sorry no pics.
It sounded lousy, really bad. There was little horn augmentation. I tried a number of fiddles to make it do something. The only fiddle that worked, kind of, was to place a can of soup behind the driver in the "compression chamber" to reduce it's volume. I got a moose like bellow at 65hz and that was all it did.
It was, as they say, a teachable moment. I learned that I needed to know more than nothing about horn theory to get to even a ballpark solution.
All in all the 45 degree tees made a much better planter for wave petunias than a horn. A very expensive planter.
I did an expanding taper pipe for the Fostex FF165. The problem with this was that the open terminus was limited in cross section area so acoustic gain was minimal. It only sounded "meh".

 

[pelanj]

jjasniew: Karlsonating is not necessary in my opinion - and maybe even contraproductive. The 34c9 works as it is with square aluminium tubes (I built these: My 34c9 (omnidirectional full range with 3FE22) build) I also experimented a bit with 3D printed k-tube (3D printed K-Tube for 1" compression drivers) The slot there is ca 15 cm long. There is also a mini-klam in that thread with a short slot, but that seems not to load the driver I have properly. They sound quite well, but the initial measurements (may be flawed, of course) show no real benefit on such a small slot.

Cramerklontz: I can highly recommend to try the pipe array. My short version does not have too much bass, but that was expected. However the "3D" effect is worth the effort. I listen mostly to multitracked panned stereo recordings and it makes the sound really enjoyable.

 

[claudiogan]

I've oft dreamed of making such a pipe array. However I wonder if "Karlsonating" each pipe would make each a little more wide-band? Something like in the picture from the net below?

The k-tube mounted vertically I think has an omnidirectional emission due to the acoustic diffraction generated by the exponential profile. The emission is generated in a space of a few centimeters. In project 22C7, diffraction emission is generated over a length of one meter. On the acoustic page I drew the spatial distribution of the generated wave fronts. The effect is not measurable in standard mode and detectable only with direct listening. MDD technology is not commercially available so for now it is only available for DIY.