Hello, I know how to use the diaphram for growling. On good days I sound like Michael from Opeth, and bad days I sound like Corey Taylor from Slipknot lol!

Anyway the question is, how do I improve my vocal strength, I seem to do my full potention for about a couple of minuites or so, until my voice gets dry and raw and then I start feeling pain. I drink alot of water when I practise, but for some reason it isn't working. But yeah, when I growl I feel no pain whatsoever, its when my throat/vocal chords have had enough it goes dry and sore, thus I sound like Corey Taylor lol. I was wondering if anyone knows how to prolounge a long amount of time at their vocal best. Seeing as my growls sound pretty badass before my voice gives up.

I use the vocal fry technique. I was wondering if I am doing it wrong or not. A friend of mine told me that it gets a bit sore quickly because the amount of air I am pushing up its very powerful and that I should really do a warm up.

So what do you guys think? Later on in the day I will record myself and let you see what you think about them.

what it sounds like is your not warming up long enough. youd be surprised how much longer you can sustain your optimum sound after a 15 minute warm up of simple scales and excersizes you can find on youtube. Personally i spend a good hour warming up and at the begining of warming up i wont even sing loud or aggressive i just take my time and make sure everything feels natural. Either that or your pushing too hard and need to tone it down for better endurance. It obviously wont sound as good but i find your throat will adapt to it over the course of a few weeks. One more thing i doubt you sound like Opeth post some clips of your good growl vs. the corey twatburger growl

I generally warm up before i play while my band is all warming up, playing chugs and blast beats etc,

I then go for about 5 minutes of every single different type of vocal style untill i'm warmed up, I start with growls, shouts, hardcore vocals, highs, lows, gutturls, then i do deathmetal vocal scales, followed by inhaled scales, i hum, zzz and just about anything I can do to warm up.

if that helps at all?

it's easier to do it with loud music in the background, or with enough adrenaline to belt it out yourself.
but it helps with the loud music in the background because you try to hear yourself.

however if you're a newbie at vocals then trying to do this may only result in you straining your vocals.