Is there such a thing as a TL opened at both ends ?

[DonVK]

....or a fixed length of ABS drain pipe (4" or 6") with a speaker tapped into the middle. Measure the FR and you can infer (transfer function) the correct model for it.

 

[Cal Weldon]

DonVK, private message sent.

 

[msgarris]

There is a "TL" speaker that is opened on both ends. It is called a tapped horn subwoofer.

Below is an example:

http://www.diyaudio.com/forums/subwoofers/193418-othorn-tapped-horn.html

However, I have never anyone do a TL for both ends of the speaker. It would be an extremely large enclosure. How would the enclosure you are talking about differ from a tapped horn?

 

[DonVK]

The TL is a direct radiator with the back facing, in this case, two pipes instead of one.

The TH has the front usually facing into the cabinet and driver rear facing in the opening.

 

[Retsel]

Check out "Rocking the Kazba"

Another way of doing (somewhat differently) what you are proposing can be found in a thread called "Rocking the Kazba." In this case it is a form of an open baffle design using the Karlson baffle to reduce the box opening to couple the driver better with the air.

Another similar concept are slot loaded designs, such as slot loaded open baffle, or SLOB.

I suggest reviewing such threads.

Retsel

 

[GM]

Do you think there are any programs that could be used to simulate it?

You can come plenty 'close enough' in HR by doing an offset driver TL, then terminating it with a 0.01 cm length/0.01 cm^2 area. This somewhat smaller than a pinhole will be much too restrictive to affect the sim or real world performance assuming you have a drill bit small enough to test it.

Ditto for doing plane wave tube [PWT] sims.

GM

 

[GM]

However, I have never anyone do a TL for both ends of the speaker.

If you mean a driver inserted in a tube in series, then search B*** Wave Cannon here for design details, which can be simmed in HR as a compound horn.

GM

 

[krakatoa]

A tapped horn is not an opened pipe - it has one end closed; the difference is in the way the driver sits "inside" the enclosure.
I am not familiar with the Karlson design but looks like some kind of horn, a double Karlson would be the same thing even if the sides communicate as in this picture - http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass-26.html - that is still a closed end - the baffle on which the woofers are mounted is the closed end of the waveguide. Same thing here - http://www.diyaudio.com/forums/full-range/271011-rockin-kazba-dipole-k-aperture-z-baffle-dipole.html there is no communication between the waveguides... they're just neighburs.
The slot loaded open baffle thing is hard to classify as an enclosure... that's for sure not a pipe, maybe I'm (slightly) wrong, it's hard to find a proper sketch to see how there things are designed but from the images I find on diyaudio.com these things are not pipes they are just siamese architectures... in general.

I'm going to repeat: the purpose of the thread is to locate projects/designs and the theory for a variation of the transmission line, the difference being the fact that the pipe has no closed end, both are open to communicate with the outside environment.

 

[DonVK]

But you still want a direct radiator, just with 2 TLs off the back of the driver. Correct.

 

[scottjoplin]

Yes I'm afraid people have been going off at tangents because of their paranoid fear of the alien creature you are describing. It's perfectly clear to me what you are after. Has GM's idea of a way to simulate it have any possibility in your eyes?

The Karlson is an extreme hybrid with a personality disorder

 

[krakatoa]

Clarifications

Re: DonVK
"Measure the FR and you can infer (transfer function) the correct model for it." >> I don't have any means to measure it and the "transfer function" is left for those who know mathematics.
As far as the architecture is concerned it’s time to upload a scheme:

Source material for "complicated stuff": https://sites.ualberta.ca/~pogosyan/teaching/PHYS_130/FALL_2010/lectures/lect19/lecture19.html

 

[GM]

The Karlson is an extreme hybrid with a personality disorder

I guess 'extreme hybrid' is in the 'eye of the beholder' as they vary from 4th to 8th order band-pass [BP] alignments with just its odd shaped reflex vent being 'extreme'.

GM

 

[krakatoa]

By the way - the distribution of pressure/motion in the pipe is there to understand why the driver is placed in the middle and not at the end.

 

[scottjoplin]

I guess 'extreme hybrid' is in the 'eye of the beholder' as they vary from 4th to 8th order band-pass [BP] alignments with just its odd shaped reflex vent being 'extreme'.

GM

Gotcha. I was thinking of the Karlson horn which was described to me as a combination of bass reflex, horn and slot loading

 

[GM]

As far as the architecture is concerned it’s time to upload a scheme:

OK, sim it in HR as a closed tube [plucked string modes] for 'close enough' or use AkAbak.

GM

 

[GM]

I was thinking of the Karlson horn

????

GM

 

[krakatoa]

OK, sim it in HR as a closed tube [plucked string modes] for 'close enough' or use AkAbak.

GM

Hornresp will not make a good enough simulation because - this was mentioned before - this pipe has double the number of harmonics, so for example a 50 hz pipe will also resonate at 100, while a closed end pipe will skip this one and only resonate at 150 hz; and the nulls will be different for sure.

I have never used AkAbak.

 

[scottjoplin]

????

GM

Apologies, I mean the original Karlson speaker, was described to me as a horn one time, I got confused

 

[GM]

Hornresp will not make a good enough simulation

A pipe closed at both ends is a 1/2 WL resonator same as an open pipe at both ends, same as room modes, plucked string, etc..

GM

 

[GM]

Apologies, I mean the original Karlson speaker, was described to me as a horn one time, I got confused

Yeah, there was a lot of misleading marketing hype, plenty of folks not conversant in bandpass design, which dates to the first compression horn drivers, so guess this is where the horn-like reference came from.

GM