i have been seeing a good bit of confusion, and misinformation on different motors that do not share the same designers, or build houses.
from left to right in all the pics is a TRF motor, soundstream 1st genXXX, tc4hp, and tc lms ultra.
the trf has the following dimensions. slug od-10", top plate height-1.226", gap od-4.26", gap id-3.815"
the ss xxx slug od-10.75", top plate height-1.362", gap od-4.322", gap id-3.82"
tc 4hp slug od-10", top plate height-1.41", gap od-4.26", gap id-3.815"
tc lms ultra slug od-10", top plate height .535", gap od-4.328", gap id-3.82"
i know some of these measurements are very close, but these small differences drastically affect the performance of each motor.
in the pics it is obvious the steel shape of each motor is completely different. the trf, 4hp, and lms ultra use slugs that are the same diameter, and thickness.
the trf has a different top plate, and backplate yoke than the tc 4hp.
the ss xxx is completely different than all of them. other than a similarity with the trf on the depth of the pole flair, but the pole vent diameter is different, and it looks the slope of the flair is at a different angle also.
i can not remember the exact the date of the 4hp release as the sw9100 ti pro, which is the first commercially available version of the 4hp, but it was released no earlier than 2003.
back in 2007-2008 i use to spend a lot of time on roe, and then ssa trying to correct people constantly calling every 4" motor a 4hp variant, but i gave up on it, and the comparisons had slacked off a good bit.
but now this newer company tantric sounds which is owned, and operated by a guy that has been in the industry for a good while, and designed a lot of motors in the past. has brought out a new 4" coils motor, and people are going retard calling it a 4hp motor, and it is clearly not if you actually new what you were looking at in the first place, and hopefully this clears some of this up.
now onto some pics
got some pics of the shd motor from tantric to add