Can someone explain the main differences? I'll start off a little:
Glass pack is a straight through tube, where the casing is larger than the actual inlet/outlet diameters. But inside the tube is a whole bunch perforated holes inside, then a layer of fiberglass strands "packed" tightly inside. Hence Glass pack. It does a good job reducing the "vibrant" sound coming from the motor, aka the buzz. On my 3g I had a pacesetter header 2.5" collector, and 2 2.5" glass packs. I think they are something like 37" in length each. And I had experiences with straight header, 1 gp and 2 gp's.
Completely straight header sounded awful, not like those high displacement cars with straight headers, it sounded like a car without any mufflers (which it is) and has that bad sound.
1 glass pack did a great job in changing the tone of the car, it sounded "good" from inside, but it resonated alot under the car because it didnt exit out the back.
2 glass packs sounded really good, it exited out the back like it should and didnt resonate at all. The only time it didnt sound good is if the motor was under a heavy load and couldnt keep up, sounded kinda diesely. IE 40kmh in 5th gear in low revs
Thats my brief intro of glasspacks, but whats the difference between it and a resonator? A resonator must use resonant sound to cancel it out or something, but its still entirely straight through. From what I hear a glasspack when you "ding" it with a flick of your finger is a dull thud, but a resonator should have a distinct ting to it.
And as for straight through mufflers, I dont have much experience with them either, and I dont see them acting any differently than a resonator would (*if Ive got a basic understanding about resonators)
I dont know if those aero-turbine mufflers count as straight through, but I would probably put it in that category.