hobot wrote:I snagged a pair of long dong Dunstalls 6-7 yr ago and these had inner tube w/o packing left and a perforated screen at narrow end then a 6 tube baffle with a soup can over their ends so exhaust exited the tube ends turns back on itself in the can cap then back out the ring slot between can and mega end. Throaty sound but not much louder than open peashooter. With end baffle removed you will be hunted down to shoot for the LOUDness EAR damaging noise unless barely on throttle. An open empty Dunstall can out LOUD Harley open headers.
Just to be clear here, I don't run them without the six-holed cap on the end. I saw off the long perforated tube that runs down the center, so the megaphone is empty, but still retains the end piece with the six or seven pieces of pipe welded together. Then you're okay up to about 3000 rpm's, and after that all hell breaks loose in the volume department.
And I am familiar with the baffling plate that came with various styles, including the long ones you're using. I do not use that plate, although a bike my brother had did have the 27 inch Dunstalls, with the same baffling plate that's centrally mounted on the end cap.
For anyone reading this that's trying to decipher what the hell is being discussed, Emgo mufflers are not of the same design and do not come with the centrally mounted end-cap that only some Dunstalls were sold with.
As far as the sound escaping from the smaller pipes that comprise the end of Dunstall pipe, I do not possess the knowledge of physics to comment knowledgeably regarding exactly what is occurring.
I can comment from direct experience, though, and say that in my opinion a Norton with gutted Dunstalls sounds way better than a Harley with straight pipes, especially when de-accelerating from higher RPM's, and very likely could be louder. I think by it's very nature, a megaphone is going to amplify a sound more than a straight pipe.