Horn Length Questions

[Doug Hart]

What is the result of lengthening a horn, and at what point is the advantage (if any) fully realized?
Example: Assume that space and transportation is not an issue. What if you were to take a T39 and continue the horn path until it was twice as long?
What about the same question with an Omnitop12?

Understand, this is not something that I really want to try, I'm just trying to better understand the theories.

[Bill Fitzmaurice]

What if you were to take a T39 and continue the horn path until it was twice as long?
.

You'd call it a T60.

[Doug Hart]

haha, you crack me up Bill.
I imagine you saying that in a Ben Stein style.

[SeisTres]

For every doubling of the length of the horn, it goes an octave lower. But then you also have to consider the horn mouth area. Even a horn was 18ft, if the mouth area is not there, it's going to perform very poorly. Sure, once you couple enough cabs and increase the mouth area, then the longer horns can have their full extension. I remember reading something about the golden number was 1/4 of the wavelength for mouth area is where it start to make a difference. As an example, check out the graph in the spl charts where a stack of 4 t30 is compare to 4 t36's. Then, it goes on to compare the same cabs but 8 of each; you can see the t36's longer horn coming into play there(don't know if the graphs are still there, haven't checked).

[Monomer]

haha, you crack me up Bill.
I imagine you saying that in a Ben Stein style.

Bueller?

[Rich4349]

Lengthening a horn makes it go lower, but all of the writings I've read about horn performance state the importance of mouth area to extension, not path length.

So if Titan39 were stretched twice as long, and that would make it a T60, a longer path also drops dBs? Can we get these variables spelled out, ala I=E/R etc ? If the T60's path length is what makes it go so low, why isn't it as loud as a T-39?

I'm so confused!

[BassMe]

Rich, my understanding is that the longer the horn path is the greater the load placed on the driver thus restricting it. Alongside this you also have the fact that you need drivers with different specs for different horn lengths (tuning). And drivers just generally have to work harder to produce lower frequencies.

Given how sound volume and the octaves themselves work I'd assume there maybe an exponentially greater amount of power/displacement needed for every octave lower you go and current drivers are simply limited.

From what I have read on mouth area/extension they both play roles in SPL and extension. This is a guide to HornResp which I found great for explaining/visualising how horns work.
http://www.avsforum.com/avs-vb/showthread.php?t=1211856

Edit: Another one I like:
http://fullrangedriver.com/singledriver/horndesign.html

I was trying to understand how the DR's work And how they improve sound quality through folding.

[Bill Fitzmaurice]

So if Titan39 were stretched twice as long, and that would make it a T60, a longer path also drops dBs? Can we get these variables spelled out, ala I=E/R etc ? If the T60's path length is what makes it go so low, why isn't it as loud as a T-39?

Look at the charts for the T39 and T60 and you'll answer your own question. Horn length determines the low frequency limit. Mouth area determines the sensitivity at that limit.

[Rich4349]

So if path length=extension, and mouth size= volume (at that freq) , what about horn path width? (ie, volume, at a given distance down the path) If you google gigantic horns (such as the phrase "live in the horn", you can find horns with a 20' + path length, and maybe 36 sq foot mouth area. BUT, these horns have a rapidly (exponential, I'm sure) decreasing cross section down to the throat. So with a 27" wide T-60, how well used is the throat area immediately following the driver? At that point, or shortly thereafter, isn't 3/4 of the width there not really needed? I'm not asking for a full page of physics calculations, but something a bit more descriptive than "Yes, it is." would be great, too.

I understand that for most people these builds are complicated enough, but I just wonder if there isn't an extra 5-10 feet of more efficiently used path length in there, toward the throat.

[Bill Fitzmaurice]

So with a 27" wide T-60, how well used is the throat area immediately following the driver? At that point, or shortly thereafter, isn't 3/4 of the width there not really needed?

I never put anything into a design that isn't needed.

I just wonder if there isn't an extra 5-10 feet of more efficiently used path length in there, toward the throat.

Sure, if you scale the horn to fit a 6 inch driver.

[bassmonster]

I wonder if there could be a "bolt-on horn" that would add to the horn length of a single cab? Sort of like a v-plate?

[Drey Chennells]

I wonder if there could be a "bolt-on horn" that would add to the horn length of a single cab? Sort of like a v-plate?

http://www.funktion-one.co.jp/products_04.html

[88h88]

Would the 'up to 12db @33hz' include the correct positioning? ie: fired into a corner?

I've never seen Funktion kit set up as anything other than split piles of speakers, subs on the bottom, mids then tops.

[Bill Fitzmaurice]

Would the 'up to 12db @33hz' include the correct positioning? ie: fired into a corner?

I've never seen Funktion kit set up as anything other than split piles of speakers, subs on the bottom, mids then tops.

They remain firmly mired in the 20th century. Not that it's a bad business model, now that virtually every other manufacturer has moved on from that technology they have a much bigger slice of what's been a constantly shrinking pie. As to the 'up to 12dB' compared to without, I seriously doubt that. SPL charts would confirm or disprove that, but of course there are none. It's a similar concept to the V coupling plate, and we know what that does.

[88h88]

I suppose if your stuff is regarded generally as being pretty fantastic then it doesn't really matter that your stuff is old tech in purple boxes with bits of plastic. Reputation/marketing or opinion on people who supposedly know their stuff goes a long way it seems, explains why Dr Dre's Beats headphones still sell millions despite being made by Monster.