"Like many people, I use Waves L1 on my mixes prior to burning them on CD. Many of my clients prefer their mixes as loud as possible even though I sometimes hate it. I sometimes find it gets really grainy or gritty sounding when too much of this L1 process is applied. What can I do to get better sound, but keep things really loud?"
Interestingly there has been a real backlash among audio engineers against overuse of maximizers in the past year. Many of us now fight like dogs to keep the dynamic range in our material and sell our clients hard on how this is really better and more musical. Of course, at the end of the day you have to apply the axiom that the customer is always right and try to do what they want.
L1 acts mainly on the peaks of your material, and it does do an incredible job of making complex music signals sound a lot louder and more energetic with reasonably little coloration. This one product practically built the project mastering industry all by itself. But like any creative tool you can push it beyond its intended boundaries and make it sound bad. The gritty quality you refer to is probably a function of too many waveform peaks in your material being compromised. In order to get you the headroom it needs to normalize or turn up the whole program, it has to trim back the peaks. Change too many of these peaks too much and the sonic character of the material begins to change.
The solution? Aside from the obvious, "back it off," you can employ more common forms of compression to reduce dynamic range before you apply the L1 process. A good multiband compressor applied to the mix can reduce dynamic range in a more gentle way (in terms of peak waveform distortion). You can dial in more compression on a range of particularly problematic frequencies thereby opening up more headroom for the rest of the signal. Applying RMS (as opposed to peak style) compression of any type is likely to help you. The ability to tailor it to specific frequencies is just another way to further fine tune the process. Once you do this you can then apply L1 to what's left and potentially get better results. There will still be peaks to act on that will allow L1 to get your overall mix a few dB louder, but it will not have to hit them as hard if the material has been somewhat compressed ahead of time. Your results will vary depending upon the material and the exact techniques you employ. Compress any signal too much and you will end up with something resembling noise. There's only so much you can do. Also keep in mind that all compressors add some type of coloration to the overall sound, especially when they are used in excess. Many people find the sound of some compressors pleasing, while they don't like others. You may have to try a few to find one you really like.