Definition of Audio Terms In My Own Words

Listening to engineers describe how gear sounds can sound like  foreign language sometimes. When I describe how a piece of gear sounds I usually stick to six basic terms which all have opposites; vintage, modern, dark, bright, clean, colored. While we hear terms like warm, tubey, smooth, etc. all the time, I’m going to try to help you understand these terms in my own words. Now remember, how a piece of gear sounds is totally your opinion. What is bright to you may be be dark to someone else. For example, I let a studio in town borrow my JDK R24 for a few weeks because they were looking to get a new stereo eq. The studio told me the eq was too dark for them. Too dark?!?! The JDK is one of the brightest eq’s I’ve ever used. Everyone has their own opinion. So lets get into breaking down some of the popular terms, and remember, this is how I interpret these terms in my own opinion, as everything usually falls into the category of my  basic terms. Speaking of those basic terms lets start there.

1. Dark -  this means the signal sounds vintage, to understand what vintage sounds like listen to some old recording and study the tone. Dark sounding also falls under colored, which we’ll get to in a sec. A dark tone to some may sound dull but depending on the material you're working on it could be just what you need. Dark to me works very well with rock music and hip-hop (not rap, yes there is a difference). As an example of dark vocals listen to some Wu-tang. You can make a signal darker by rolling off some of high frequencies. Examples of some dark gear to me are the Universal Audio solo 610, Universal Audio la2a.
2. Bright -  this means the signal has more high frequencies. If you want to make something sound brighter add some high frequency to it. Bright being the opposite of dark can be great on some vocals. Too bright will result in harshness. If you want to hear harshness boost that high end as far it can go. If your ears are crying in pain then you're experiencing harshness. Bright can also improve clarity if done correctly.
3. Clean -  clean means your signal is pure and accurate. This is a modern sound, the opposite of vintage. For example a clean mic pre means it doesn’t change (or color) your sound. So what you put in is what you get back. Solid-state or transformerless is generally clean. Examples of some clean pres to me are the Avalon 737 pre, empirical labs mike-e, and API pres, even though they aren’t solid-state or transformerless.
4. Colored -  this is the opposite of clean. Coloring your sounds means changing the tone from the original signal. Colored can be associated with vintage and sometimes dark. Different gear has different colors. If you listen closely you can hear differences between different pieces of gear. The Neve 1073 is one of the most famous channel strips ever because of the color it adds to a signal. Color generally comes from gear with transformers and tubes. Though some tube gear is clean (like the avalon 737) tubes are mostly associated with color and warmth. Same goes for transformers. Some gear can have transformers in them and still sound clean because the transformer doesn’t produce a lot of noise. For example, my Empirical Labs Mike-e is a clean pre though it has a transformer input, it's a low noise transformer. Anything claiming a British sound should have some color to it.
5. Muddy -  this the second hardest term to explain, but here we go. Mud is a build of low mid frequencies (200-500hz) that makes the signal sound cluttered. Mud is not a positive thing and should never be taken as a compliment. It took me a long time to distinguish what mud was.
6. Sterile -  sterile means ultra clean. This is good for say orchestra where you usually want as little color as possible. Sterile can also come off sometimes as “too clean”, meaning its so clean it's boring. These type of pres are crystal clear though. Examples of sterile pres to me are Millenia and Grace pres.
7. Transparent - this another word for clean and it's mostly associated with compressors and eq’s. A transparent piece of gear means its not going to impart any color on the original signal during its processing. If you're happy with the tone of your signal but need to further process it then you need to reach for something thats transparent. My Chameleon Labs 7720 stereo compressor I use for buss compression is an example of a transparent compressor. Also Daking FET and JDK R22, and the Speck ASC eq are known for being transparent.
8. Smooth - this to me differs in compressors, eq’s, and mics. For compressors smooth means its compressing but you can’t really hear the compression, even at high gain reduction. The Summit Audio TLA 100A is the smoothest compressor I’ve ever used. Any compressor, except maybe aggressive ones (more on that next) can be made smooth with the right settings, but compressors like the TLA 100A does for you on its own. Opto compressors are known for being smooth. Because of their smooth character they are widely used on vocals. Examples of opto compressors are  the la2a, Manley ELOP, and Tubetech CL1B. Plugin examples of smooth compressors include the Softube version of Tubetech CL1B and Summit Audio TLA-100A and the McDSP 6030 ultimate compressor Opto-C, Opto-L, and British C.  Smoothness has to do with the knee of the compressor as well. If your compressor has the option to adjust the knee try using a soft knee for smoother compression. On EQ smooth means you can get away with high boosts without hearing any harshness. My JDK R24 to me is a silky smooth eq. On mics smooth means there is an even frequency response. Some mics will hype (or boost) certain frequencies to help achieve a certain sound. Because of this sometimes a different mic can be a substitute for eq on a source. Be careful you don’t judge a mic off its frequency response because a mics sound has to do with a lot more than just that. Mic pres, though often not shown, have a frequency response to. So a smooth mic pre, like a smooth mic, will have an even frequency response meaning certain frequencies aren’t jumping out at you.
9. Aggressive - in a mic pre this means in your face, very forward sounding. The API 312 and 512 have been described as an aggressive mic pre. In a compressor this means it really clamps down on a signal even with gentle settings. My JoeMeek TwinQ I previously owned had very aggressive compressors. Even with a slow attack, low ratio, and high threshold those needles would almost slam. I could never get a gentle compression action set up with them. Though the JoeMeek is a optical compressor, FET compressors are known for being aggressive and being capable of a very fast attack time.The most famous FET compressor is the 1176. The FET compressor from Softube is an emulation of an 1176. While I’m able to control it better than the JoeMeek TwinQ compressors, it's still an aggressive compressor to me.
10. Warm - this is the one you all have been waiting for. Warmth is the most used word when describing the sound of a piece of gear. Its the hardest one to describe because people who have no idea of what warmth is use the term freely. So what warmth is to  you and how you perceive it will be different from others because the term is used so loosely. Dave Pensado (shot out to the Pensado Students Facebook group) says warmth is another word for dull, and I partially agree. Where bright deals with high frequencies, warmth deals with the low to low mid frequencies. Tubes are associated with warmth because they add harmonic distortion (the good kind of distortion) to the those frequencies. This is what people are referring to when they say tube warmth. Where I partially agree with Pensado’s statement is that a warm signal can sound a little on the dark side, and like I mentioned earlier dark can be associated with dull. So now we have warmth, the word everyone loves to use for a good sound, and dull, a negative adjective in the same sentence describing a signal.

I hope I did a good job explaining these terms in my own words and this helps other understand what these terms mean. The only way to get your own definition of these terms is to listen to the gear and make your own assumption. Companies like Softube do a great job at emulating hardware in software, so demo some of their plugins and study how each sound different. If you're looking at getting some new gear and didn’t know what to go with then use this to help decide on what you need based on the sound you’re after. And you can always email me for my opinion on gear if you need it.