I`m using a Rode NTK with Focusrite RED 7 pre.The vocals sound harsh and after cutting 4K and above the vocals sound lifeless/muddy with the mid frequencies 400 to 1500hz accentuated.Is this because of cutting the hi mid or because the room accentuates these frequencies? What can I do to solve the problem?
The first thing you should try to do is to tackle the problem at the source, rather than trying to do a "band-aid" type fix with EQ.
If a singer sounds too harsh on the chosen setup when you are recording, then you have several options to fix that:
-- Try a different microphone and/or pre-amp
-- Move the microphone to a different position
-- Try a different position in the room
The first one above will have the greatest impact on the sound. The reason why there are so many different microphones out there is that there is no single microphone that works great for everyone. Every major recording studio has a wide range of microphones to choose from so that they can pair up the right microphone for the job. Each vocalist is unique, and a microphone that might sound great on one person can sound really bad on another. So, the first thing to do is to try a different microphone until you find the one that sounds best for the voice you are trying to record.
Microphones Pre-amps can also affect the sound, and the pairing up of microphones with certain pre-amps to find the right combination can make a significant difference. Usually the difference in pre-amps is not as noticeable as the difference between microphones, but there can be a signficant difference and some microphones just work better with certain types of pre-amps. Definitely some pre-amps are more bright or "harsh" sounding that other, just like microphones can be, so if you have a bright microphone paired up with a bright pre-amp, the result can be something that is WAY too bright or harsh.
If you don't have the luxury of lots of different microphones and pre-amps to choose from, then try moving the microphone around or changing the polar pattern on the microphone (if it has multiple patterns). Microphones have different responses on and off axis, and so moving the microphone above, below, or off to a side can change the sound, or even just changing the angle of the microphone to one side or another so that the singer isn't singing directly into the front of the microphone. Also, to warm up the voice (which will make the harshness less noticeable), use a directional pickup pattern (such as cardoid) and get the singer to move in really close (around 6 inches) to take advantage of the proximity effect.
Then there is the room. If you are not in an acoustically treated room, and you are close to a wall or window or other hard surface, you could be picking up reflections from that hard surface that can cause comb filtering and other effects that could make the sound harsh or even "phasey". Try moving to a different location in the room to see if that helps, or use a vocal booth or some material around the vocalist that will absorb the upper mid and high frequencies.
Finally, as the very last resort, if nothing else works, you can try EQ and other tools such as de-essers. EQs come in a very wide variety and their quality can vary quite a bit as well. It sounds like you are using a shelving or low-pass filter to roll off frequencies from 4K and up. With most EQ, when using a shelf or pass filter, there is also going to be a resonant peak right at the roll off frequency you selected, in your case around 4K. The size and bandwidth of this peak depends on the type of filter implemented in the EQ and can be quite noticeable. Sounds like this might be what is happening in your case... you're rolling off frequencies above 4K, and at the same time getting a resonant peak probably in the 2K to 4K region, really bringing out the mid range.
Also note that simply removing the high end is going to make the mid range and low end more pronounced, and when you combine that with the resonant peak of your EQ, you are going to hear a lot more mids.
So, you can try a different type of EQ, if you have any, or simply switch to a parametric EQ with a bell filter instead of a shelf, and just zero in on the range of frequencies which seem "harsh" to you and pull some of those out without resorting to shelving out the entire high-end above 4K.
A De-Esser might also help, and comes in handy quite often for vocalists who simply have too much sibilance in their voice (especially when they are paired up with bright microphones and pre-amps). A De-Esser is just a compressor with a built-in side chain EQ that lets you trigger the compressor just on the frequency range where the "ess-es" or sibilance resides. So, anytime there is a loud ess type sound, the compressor will hear it and pull the levels down a bit for you.
That's all I have time for right now. Hope this is helpful!
Thanks a lot Steve.Just one more thing.Are there any cheap ways of treating my room so that it will absorb frequencies between 500 and 1500 hz?
I don't know of any products that will ONLY absorb between 500 and 1500 Hz.
Your best bet is some broadband absorbers and bass traps appropriately placed.
Seems like everyone favors the OC 703 rigid fiberglass for making broadband bass traps.
Lots of DIY solutions and plenty of great advice on acoustics and construction on the John Sayer's Recording Studio Design forum.
They are all very helpful there and much more knowledgable than I am about room acoustics and treatment.
I personally use the RealTraps system from Ethan Winer, with several different sizes of bass traps in the corners of my room, and on the wall-ceiling corners as well, plus the High Frequency mini-traps at the first reflection points in my control room. Those are NOT cheap solutions, however, but I didn't want to mess around with building similar things myself, and the RealTraps also look VERY nice.
Ethan has some good acoustic articles on his RealTraps.com web site, and if you search through it, you can also find plans on how to build your own bass traps (not exactly the same as RealTraps, but probably good enough). Also, you'll find links to lots of different designs for bass traps and other absorbers on the John Sayer's forums.
Good luck with it!