Tuning a back loaded horn

What is the best material to use to tune a back loaded horn?

After doing some research I saw poly-fil is widely recommended for TL enclosures. Would poly-fil work for a back loaded horn also?

What is a "back loaded horn" ? Would that be like a Klipshorn? If so, no fill is used.
Eldartford,Back loaded horns are used in many full range driver systems using lowther AER fostex drivers, others. They are more of a hybrid of TL BR and horn in a folded pathway cabinet.But a few are true full back loaded horns but even they need some tuning. When you used a fullrange you need to absold some of the back wave to prevent a peak in frequincy responce. This is what the poster is refering too.
Thanks for the response John. I try some Madisound wool.

Would I start by putting some wool in behind the driver or close to the mouth of the horn? I have a sachiko design (from the Frugal Horn website) with 206 fostex, and I want to bring the upper bass down just little bit.

I am thinking I need to start close to the mouth of the horn.

Stuff the area behind the woofer tightly, and progressively looser towards the vent. The object being to convert acoustic energy to thermal and reduce peaks/nulls in the cabinet response. In other words: Add 1/2lb/ft3 of fiberfil to the coupling volume(area directly behind the woofer), and reduce that to 1/8lb/ft3 of
fiberfil to the first one third of the hornÂ’s length.
PS: Polyester is nice because you don't have to worry about moths and their larva.
The real wool is treated you will not have a moth problem. You tune a BLH from the driver down you shouldnt need to damp mouth but this all depends on cabinet design and driver choice. I could help you more if I knew this.
Third attempt to respond to Johnk question.

John, the speakers I use is at http://homepage.mac.com/tlinespeakers/FH/download/Sachiko-map-1v0-230307.pdf. I use Fostex 206E drivers.

Rodmann - I put about 5/8 of a pound of polyfill packed quite tightly behind each driver.

The bass that was bugging me is greatly reduced, and somewhat to my surprise, the speakers seem to have more snap, more detail and improved midrange!

Man, back loaded horns are the bomb!