What is compression?

Hello guys. I really would like to know what these terms mean and if and how they are different. Are these all the same thing? What is what makes an album loud?

1)Brickwall
2)Peaks
3)Compression
4)DNR

 

Compression in the context of recording, which I presume is what you're asking about, is a way of reducing a music signal's dynamic range, so that the difference between the loudest parts and the quietest parts of the signal going into the compressor is not as great. There are a bunch of different technologies and technique that have been and are used to limit dynamic range of a signal in whole or part at all kind of different points in the recording and mastering process.

Peaks are the loudest most instantaneous signal tops -- dynamic reduction by compression typically responds to peaks by bringing down the level of the signal when the peaks reach a certain threshold by some ratio of reduction.

When people in audio circles talk about brickwalling and loudness wars and such they're talking about a common practices begun in the early 1990s. In this technique, a digital limiter -- a kind of compressor which stops the output signal from passing a certain level when a peak is encountered -- which looks ahead at the digital file and identifies upcoming peaks, is applied, the output level from the limiter is set at or near the highest level that the digital audio medium can accomodate without distortion, the input level into the limiter is set fairly high, and the threshold at which the limiter begins acting is set pretty aggressively so that there's lots of output limiting and input boosting of almost the whole track. The result is a severe narrowing of the dynamic range -- the "quietest" parts of the music are almost as loud as the loudest parts -- and, in the worst cases, almost a sort of deformation of the wave form so that it is almost like a hashy distortion signal not a ebb and flow music signal, and pushed to such a high output level as to be at or over the line into actual distortion. There may be artifacts of this sound that might be modern, hot to some listeners, artists and producers.

DNR, I think you're asking about is Dynamic Noise Reduction, which is a digital audio process for, attempting to filter noise.

 

I was thinking DNR on this site refers to Dynamic Range or DR. I love this site for dynamic range: Album list - Dynamic Range Database

 

As long as you don't use dynamic range as any kind of arbiter for musical quality you'll be fine.
There are many albums that do not have a really wide dynamic range that are full of great music.

 

Good summary with the singular exception of DNR. That is/was a single-ended analog noise reduction technology which came out in the mid 80s.

However I suspect that the poster above is likely correct that the OP meant DR as often referenced on this forum.

 

Thanks for that, my knowledge is limited but you've confirmed my basic understanding is reasonably sound.

The best analogy I've heard about compression, "It's like driving a car into a brick wall, it makes a loud sound but doesn't do anything good to the car".

Many people on this forum talk about bad EQ but to my mind that's a digital artifact from compression etc. and not down to some mastering decision.

Low DR figures aren't great but many contemporary album are fine with, no artifact, with DR figures as low as 6 - 7, with electronic music a DR of 4 can sound amazing.

I don't think compression is just digital, although I don't know if it was used much in analogue recordings. My friend had a Aiwia cassette deck, were he could limit recording level so it wouldn't go beyond the max level. He'd just set volume to max and his recording sounded like Phil Spector had produced his 'wall of sound' on every album.

 

It's not restricted to digital, and compression is used on everything.
Has been for years.

 

Being a recording musician, I can tell you that there is some amount of compression in almost every recording you've ever heard that has been done in the last 50 years. The master bus generally has some compression on it continuously. There's also a type of compression that comes from tape saturation, but I imagine that's not the main topic of discussion.

I wouldn't get wrapped around the axle about the idea of using compression. But anything can be abused.

 

Shown is two different mastering of the same recording. The bottom one is brickwalled. The volume is increased beyond the headroom for the audio editor. The peaks have been truncated to allow for an overall louder playback of the track.

 

This is the current and "modern" method of using compression, and is illustrated above. It's done to increase the overall impact of the song and the wars are a result of various bands and producers wanting to have their songs sound louder than the next guys, as it was viewed as a means of having greater visceral impact.

 

Compression can be sudden or gradual in terms of how peaks are clamped down on, the brick wall analogy just relates to the fact that a threshold is hit and the it's more like an on-off switch, everything over that point is instantly limited, vs. compression that might be done more gradually, with the compressor beginning to clamp down on a peak as the level rises, and with different degrees of compression --- 2:1, 4:1, 10:1, whatever.

Also, although the "loudness wars" style practices became commonplace because of the use of digital look-ahead limiters beginning in the early '90, limiting and compression are not inherently digital. There's plenty of limiting and compression that was done and continues to be done in the analog domain on recordings. It is commonplace on all the famous classic rock records everyone celebrates around here, even sometimes used because of the colorations in sound particular compressors and compression settings could produce -- a huge part of the characteristic mid '60s Beatles sound on record is a result of the deliberate use of a Fairchild compressor to color especially the drum sound. That giant, blooming cymbal sound on Revolver is a compression artifact deliberately used. Pretty much every record you probably listen to had lot of compression on it in all kinds of different places -- maybe compression used during tracking on vocals or bass or drums, and maybe compression added at mix down then more and different compression at mastering. And in the LP era a lot of times compression was more necessary to make sure ppp music didn't get lost behind rumble or that bass peaks could be cut in ways that my old GE Trimline turntable would track.

It's 100% about the decision making in how to use these tools and the sound and effects you want to achieve. It's not about the tools themselves. Now it is true that in these days there are plug ins with presets that home and amateurs might just turn on to deliver a particular hot, modern, limited boosted and squashed sound. But it's still a choice -- I want a hot sounding mix that's riding right at the edge of digital overload with modern rhythm punch that doesn't get lost when someone is listening in the car or with earbuds out in the environment. EQ choices are other choices. But it's all a matter of choice.

 

All the time. Compression is as old as high fidelity recording. It gets a bad name around these parts, and for good reason. But it can be very useful to making a recording sound good in less optimal environments, not least on the radio or for streaming, to overcome a low signal/noise ratio, or allow the music to be better heard in a noisy environment, or in the background. Cruising around in your German convertible with the AM radio. Chopping vegetables in the kitchen with Apple Music. Modern, very modern.

 

Perhaps I was being too kind in saying it wasn't a mastering decision, rather than a instruction from your employer.

I know that at the music college my friend's son attends, those on the Studio Production course are taught how to make it as loud as possible.

 

All of this. While digital compressors are very common now with the use of plugins, analog outboard compressors are still very much coveted in the recording process. Not only does it serve to normalize the volume peaks as intended, but compressors often color the sound, and that's the sound we are used to in rock and pop recordings. It's funny how often you'll see drummers on drumming forums asking a million questions about how to get so-and-so's snare sound for their band, and they'll go round and round talking about this head or gaffers tape, etc etc etc. The correct answer usually is, use the same compressor that drummer used and compress the hell out of it. That's how those sounds are achieved, via processing of some sort.

Where compression typically goes wrong, is after all that mixing has been done, and then in the mastering process someone compresses it even more and then limits it, all to get a loud final master. Lots of times it isn't the fault of the Mastering engineer...mixing engineers send them mixes pre-compressed. You can't get dynamics back after you compress them so the Mastering engineers hands are pretty tied. But there are also plenty of cheapo mastering "engineers" and DIYers who simply run their 2 channel mix through a L1 Limter plug-in and call it a master. And that's how you get a squashed final product that looks like a solid bar when you open up the wave form.

 

Several points. First of all you can surely brickwall a signal with an analog compressor. In fact it's been done so many times on pop records, usually just for one instrument and nobody complains at all. They just like the sound. Yes you can use a digital limiter to do this and many have, but it doesn't have to be digital to ruin a record.

The other point is that the loudness wars did not start in the 90s. I was a victim of the loudness wars in the 70s.

We had recorded a record which I actually mastered with Stan Ricker. It sounded wonderful. Unfortunately, we were not the only entity to record that same song. When our management got a hold of a copy of our competition and compared it with our record, the **** really hit the fan. The problem is that our song started out quietly and the other version started out loudly. It's not the overall level that was a problem, but our intro.

Management cried that we had lost the record as a result. Since I was responsible for the sound of the studio, all eyes were focused on me. I was asked how to save the record and my response was to remix the intro, but nobody wanted to do that. Instead, I was told to go back and remaster, but pot up the intro and then bring it back down when the main part of the song started.

This was not practical since we mastered it at 1/2 speed, but Stan and I gave it our best shot. It was a mess and we never released the record. The other version went to the top of the charts. Ugh!

 

Of course, I don't think I ever suggested that brickwall compression was only possible with digital; if I did, I didn't mean to. And sure, "make it louder, make it hotter, make it pop on the radio next to the other guy's record" have long been market demands. But it's also true that as an overarching, secular trend, there has been a particular sound and set of practices that have become widespread, and in a way self-replicating thanks to plug-in presets, since the middle-'90s that I think we can talk about as a broad, common practice and which in part became popular because of the commercial use of certain technology (and maybe also playback technology became more dominate by compresses lossy digital and iPods and phones and earbuds).

 

Yes, I wasn't disagreeing with you as much as offering clarification. I realize you know what you're talking about.

 

It's always been a thing, and it really took off in the 90s when CDs freed up people to ush their masters further than vinyl would have allowed, but it has gotten arguably worse with how ubiquitous digital recording equipment has become. Even in the 90s, recording gear was still out of reach of most people, so there was still some level of restraint with professional hands working the knobs. Today Waves L1 Ultramaximizer will run you $40 to download, so ultra limited squashed masters are within every average Joe's reach to "master" their own recordings.

 

Rather it would mean digital noise reduction. Or in the case of forum members here, do-not-resuscitate.

 

This has been extremely horny to read. I do have one more question in regards to dynamic range. Does having a poor dynamic range mean that the record has to be loud or louder? For example, Oasis's "Be Here Now(97)" and Liam Gallagher's "Why Me Why Not(19)?" have about the same dynamic range(DR database). Yet "Why Me Why Not?" is significantly louder than "Be Here Now" which was an album that was called the loudest thing at the time. Sgt. Peppers 2017 mix has much higher dynamic range than the aforementioned and yet it is tied in loudness with "Why Me Why Not?". So what gives?

 

No.

 

So you can have an album with horrendous dynamic range and it can also be not loud? So if that's true what makes the Sgt pepper 2017 mix so loud? It's like a big wall of sound that sounds nastier the more you raise the volume. I lent that CD to my brother and he told me just now that the album has this obnoxious loud and artificial bass all over it and that the whole thing is very louddddddd.

 

Not to mention the algorithm used doesn't reflect equally on all musical genres, particularly Classical.

 

Earbuds, iPods, MP3 and listening on the go in loud public spaces. Noise drowns out the quiet bits, so they're boosted. Sign of the times.