Beware the one eyed monster!

bitzo wrote: does exist a method to calculate it?

Yes .. in fact it is pretty simple to calculate for single frequency.

If length of duct/labyrinth or horn between two sides of same diaphragm/cone is 1/2 wave length of certain frequency on that frequency acoustic radiation of both sides of cone will be in phase.

Hehh.. but you say, OK ..But that is only on that exact frequency so what is with lower and higher freq. how to get them "in phase"?? :shock:

Now tapped horn theory comes to help.
Tapped horn by idea is designed to have "variable" cone surface area depending on frequency speaker play and also cleverly used sound physics to get wider usable bandwidth from same speaker.

It works relatively simply I will try to explain on example as much as I can;

Let's take tapped horn with length between two sides of cone is 215cm (ignore a bit of length of "offset" from center of cone to "blind" end and bit of extension from back of driver to horn mouth)

215cm is 1/4 wave length of 40Hz frequency .. so what happens here when speaker (booth sides of cone) play 40Hz?
One side of cone which is near horn throat "see" entire 1/4 wave length horn load and effectively drives it.
But other side of cone is near the horn mouth and exactly 1/4wave length distant from horn throat and 40Hz wave radiated from that side travels down the horn (yes you can look at this .."travel"backwards into horn) and reflects from "blind end" horn throat and than travels back to horn mouth. When that reflected wave (40Hz) comes back to horn mouth it is exactly 180degrees out of phase with initial wave from that side of cone. Such way back side of driver cancels it's own radiation on 40Hz and effectively decouples itself from horn system so it not contribute positively or negatively on horn response at 40Hz.
So at low end only one side (front side) of speaker "drives" the horn.
When we start rising of frequency horn approaches to be 1/2 wave length (will be exactly at 80Hz). Mean while on our "way" to 80Hz things gradually change and back side of driver do not cancel it's own radiation strongly like on 40Hz ..so less and less canceling to the point when it begin to come in phase with initial wave from that side of driver.

When we come to 80Hz booth sides of driver are completely in phase (1/2 wl distance) and also wave from back side of driver (in mouth) is 1/2 wl distance from "blind" end throat so when wave travels back to horn and comes to throat it is 180 degree out of phase but when it reflects back to the mouth phase is rotated for another 180 degrees (so 360 in total = 0 = in phase)

Mean while all this creates peaks and dips in freq. response but exact thing (peaks and dips) happen when horn mouth are too small to reproduce certain frequency. (even biggest professional bass horns have too small mouth at low end - so suggested to use in stacks to effectively increase horn mouth and come closest to "ideal" and such way smooth-up response and eliminate peaks/dips which are curse of single horn.

At first look Tapped horn also have far too small mouth (even smaller than most classic FLH-s) to reproduce low freq. without peak/dips ripple. ... but taped have trick in sleeve!
So on freq. where we have first peak caused by too small mouth area tapped horn physic creates equivalent dip... and further where we get first dip from too small mouth TH "situation" makes first peak.. So there.., those peaks and dips caused from two different reasons nicely smooths out each other and such way tapped horn (even single) is capable to reproduce very smooth response through its usable bandwidth.

..that is theory (and seems that it works good) smiley1 ..

Thanks for taking the time to post the detailed reply.

And a simple question, why is taped not tapped?
T APE ed or T APP ed?

Mr. Stipe, you're the man! Many thanks for teaching us.
So I get this concept....if the 2 driver sides are closer you'll get radiation cancel at lower frequency and you'll get in phase at higher freq. Am I right?

nickyburnell wrote: And a simple question, why is taped not tapped?
T APE ed or T APP ed?

Looks like a Y-tapped horn to me. Was it designed with Hornresp? If so, can you post the inputs?

this cab is so complex, HR isn't good in this case. However here's an akabak sim b&c 18tbx100 loaded, composed by eleven section, I take care of the magnet diameter in 10th section.
Great cab, I'm very curious to listen it someday.

Bitzo, Can you simulate the Void V18/1000.

yes, I can. smiley33

I think I start building one tomorrow, and want to put the void v18-1000 in because I can't afford the b&c 18tbx100 of fane 1000, I will post building pics on FSP or SP.

I've started building: forum.speakerplans.com/build-of-a-cb18-and-a-x1_topic40867.html