Folded horn enclosure

[the_garynator]

yeah basically in a TL you can either have no change in port area or have it decrease or expand (horn). and i know tl can be big. i have a 24Hz t-line that the port area doesn't change for my JL 12" right now and it takes up all the extended cab part of my truck.

the sub im toying around with the idea of building a folded horn for is my 12"s baby brother. its an 8" sub same model and it's fs is around 30 Hz.

i've done some reading and what not today and one person on youtube said " If the point of a horn is to be an acoustic coupling device to match he sound waves with the environment, doesn't a horn loaded enclosure become a problem in a high SPL vehicle application?"

can someone help me understand the "coupling device" part of this.

and thanks for your guy's input so far!

that statement isn't really accurate, but I think what he means by an acoustical coupling device is the quarter wave transmission line portion of it. The purpos of a T-line is to invert the rear wave of the sub so that it provides constructive interference with the front wave (i.e. does not cancel it out). The horn side of things increases the efficiency at which the rear wave of the speaker is transferred from the enclosure to the room or vehicle cabin. I can explain how it accomplishes it, but I'm too tired right now to do it lol.

[the_garynator]

here's a decent explanation from here: http://basscouch.com/labhorn-science/:

"Most people assume that a horn throws the sound, like a trumpet. This
is not true; a horn loaded speaker does not throw sound any further
than a non-horn loaded speaker. In horn-loaded sound systems, the horns
are a tapered sound guide, designed to provide an acoustic impedance
match between a sound source and free air. This maximizes the efficiency
with which sound waves from the particular source are transferred to
the air.

A horn does, however, minimize the unwanted volume levels behind the
cabinets. This leads to less sound bleed onto the stage than
non-horn-loaded systems. This aspect is great for performers – they can
hear themselves from the monitors clearer and it helps minimize the
effects of microphone feedback.

Horn-loading also naturally increases the efficiency of the drivers. A
horn-loaded speaker gains 1.5 decibels of gain per every reflection. In
this way, the bent walls of the Labhorn naturally amplify the sound
coming out of the speakers by 6 decibels."

[HunterJohnson]

I've seen a folded horn do a 147 at 45hz off one 10" on a Rockford 1500 amp.

It was in an rx-7, and the horn unloaded off the rear glass

[revoracing247]

so if the purpose of a transmission line box is t basically invert the wave off the back of the driver so it's harmonious with the wave off the front. then how is it possible to create a sealed TL? in research i've seen, people have built sealed ones.

[revoracing247]

also can anyone steer me in the right direction as far as how much the horn should grow? should it be linear or exponential?

also should the starting port area be smaller then the sd of the sub or should it start at the sd of the sub and grow?

any help or links to stuff that will help will be greatly appreciated!