What is compression?

[jason r. baur]

Please forgive my ignorance, but what exactly is compression? Is it a reduction in the "distance" between the quietest and loudest points in a recording? Also, to know whether a CD is compressed, would you have to compare it to a version that isn't?

[Bob Lovely]

Originally posted by jason r. baur
Please forgive my ignorance, but what exactly is compression? Is it a reduction in the "distance" between the quietest and loudest points in a recording? Also, to know whether a CD is compressed, would you have to compare it to a version that isn't?

Jason,

See the thread on RCA Nashville Studio/What is compression? that is still an active thread. Steve put a very educational link in one of his postings.

That link should answer your questions and further your knowledge!

Bob :)

[BradOlson]

All popular music is compressed but on some discs, the compression is more obvious than others.

[jason r. baur]

Originally posted by Bob Lovely


Jason,

See the thread on RCA Nashville Studio/What is compression? that is still an active thread. Steve put a very educational link in one of his postings.
Bob :)
Bob,

I was OK at first with that compression article, but my head began to hurt before long. Anyway, I see I was basically right. But how about you or someone else offering the "Compression For Dummies" version--or was that article it?

Also, if a CD is remastered a second or third time, and you don't have to turn the volume as high for the newest one (i.e., the new one is louder), does that automatically mean it's compressed?

Finally, was the "active thread" comment a dig?;)

[Bob Lovely]

Originally posted by jason r. baur

Bob,

I was OK at first with that compression article, but my head began to hurt before long. Anyway, I see I was basically right. But how about you or someone else offering the "Compression For Dummies" version--or was that article it?

Also, if a CD is remastered a second or third time, and you don't have to turn the volume as high for the newest one (i.e., the new one is louder), does that automatically mean it's compressed?

Finally, was the "active thread" comment a dig?;)

Jason,

No dig intended, just trying to be helpful. The information contained in the link starts off at the most elemental level and then works into the depth and details. As you can see from the link, compression is actually a very complex process with many characteristics. The most simple explanation is that compression is an electronic form of controlling levels of audio for both technical and creative purposes. In other words, compression is used during the recording and mastering process to both control the "balance" between soft and loud passages but to also "tailor" the sound for certain affect.

A major objecton in this Forum is when recordings are remastered and additional compression is added to an "already" compressed master. Most of us here are against such added compression because it is not really neccessary and it is beyond the intentions of the creators of the original recording. Plus, it degredates the sound as well!

I hope this helps!

Bob :)

[jason r. baur]

Bob,

Thanks again. But what about the second paragraph in my last post?

[Bob Lovely]

Originally posted by jason r. baur
Bob,

Thanks again. But what about the second paragraph in my last post?

Jason,

Two possibilities--the louder CD was either mastered at a higher output level or additional compression was added during remastering!

Bob :)

[Richard Feirstein]

There are two basic technologies at work, compression and limiting. There are also at least two basic goals. First, to gain a sonic effect so that the listener will enjoy the magic that is music reproduction. The second is to fix the recording so that it can be played over AM and FM and TV and on your home setup and mono boom box and not distroy the hardware or turn off the station.

If you make a great home stereo recording of your band that sounds great on your high end sound system you may not even recognize the sound after it goes thorough the black box sound processing at the radio station.

Limiting is employed to avoid overloading the tape heads in analog situations and to avoid overdriving the mixing boards, and to avoid driving digital recorders into overload.

The effect of both, if overused, is to push everything loud but just below the point of overload. (Analog tape recorder heads actually start to attenuate the high end if the high frequencies are driven at too high a level into the heads).

Dolby noise reduction and other noise reduction systems were intended to be two way systems so that the listener would not hear the effects of the compression.

If you look at the top selling 50 pop recordings over the past 40 years you will likely find that most employed excessive compression and limiting. Thus success is often copied without thought, just because it is associated with commercial success.

This is oversimplified, but I hope it addresses your question.

[Bob Lovely]

Richard,

Great points...I have read some very interesting accounts on how "singles" were mastered to sound a certain way for AM Radio back in the 50's and 60's. My Father was a Broadcast Engineer in Radio and TV for his entire career and it really bothered him that he maintained technically, wonderful sounding stations whose "on-air" sound was ruined by the "Sales" department and station management who wanted a bigger, louder sound on the AM band....added compression and reverb to everything!

Bob

[Steve Hoffman]

Gotta jet to breakfast, but REMEMBER THIS:

Analog compression/limiting: Good

Digital compression: Not good



;)

[Bob Lovely]

Originally posted by Steve Hoffman
Gotta jet to breakfast, but REMEMBER THIS:

Analog compression/limiting: Good

Digital compression: Not good



;)

Steve,

That is a basic in the course--Hoffman On Compression 101!

Bob ;)

[Richard Feirstein]

You should have heard WABC FM in NYC before management at ABC realized they owend this property. It was commercial free and put on some of the best sounding live music ever. They they changed the call letters to WPLJ, the newspapers reported on how great and progressive the station was and managenent at corporate took notice. Within months all those bad AM radio practices were incorporated into their sound and today this is just another second rate sounding radio station. Those were the days. Today you purchase a black box that does all sorts of compression, EQ and limiting functions without any human intervention to gain that big city powereful sound (yet studies have shown that highly compressed, always loud radio is harder to listen to for a long period, but they don't seem to care). People would be shocked if they heard how good AM and FM can sound. Try your local low powered college station for the best chance of real clean sound.

[Bob Lovely]

Originally posted by Richard Feirstein
You should have heard WABC FM in NYC before management at ABC realized they owend this property. It was commercial free and put on some of the best sounding live music ever. They they changed the call letters to WPLJ, the newspapers reported on how great and progressive the station was and managenent at corporate took notice. Within months all those bad AM radio practices were incorporated into their sound and today this is just another second rate sounding radio station. Those were the days. Today you purchase a black box that does all sorts of compression, EQ and limiting functions without any human intervention to gain that big city powereful sound (yet studies have shown that highly compressed, always loud radio is harder to listen to for a long period, but they don't seem to care). People would be shocked if they heard how good AM and FM can sound. Try your local low powered college station for the best chance of real clean sound.

Richard,

I have an old Heathkit tube AM Tuner that my Dad built in 1957--wide band. Since I am only 90 miles north of Chicago I am fortunate to receive a great sounding AM station like WGN in Chicago--an old fashioned, good sounding AM station. Most AM stations really do not sound all that good today but there are exceptions. Your point about FM stations is right. The Educational and Community non-commercial stations sound the best!

Thanks!

Bob

[Grant]

BUT, when they used to slightly compress singles, sometimes it actually added a bit of vibrancy to the sound. Yeah, the music was sometimes squashed but sometimes a song can sound too clean and crisp. Sometimes I like some "dirtiness" in the sound.

I sometimes dirty up a recording I feel is too clean with either a little (ulp!) digital compression or use an analog tape emulator in Sound Forge's Accoustic Mirror to get that tape saturation sound.

[Bob Lovely]

Originally posted by Grant
BUT, when they used to slightly compress singles, sometimes it actually added a bit of vibrancy to the sound. Yeah, the music was sometimes squashed but sometimes a song can sound too clean and crisp. Sometimes I like some "dirtiness" in the sound.

I sometimes dirty up a recording I feel is too clean with either a little (ulp!) digital compression or use an analog tape emulator in Sound Forge's Accoustic Mirror to get that tape saturation sound.

Grant,

Clearly, I understand your point. Please provide some examples of where you have done this? I am curious!

Bob :)

[lukpac]

Originally posted by Bob Lovely
The Educational and Community non-commercial stations sound the best!

Well, if you're in an area where reception is perfect. Get in the fringe a bit, and the background noise starts to get in the way. Not as much of a problem with more "compressed" stations since the signal is louder.

I kinda like that compressed FM sound myself...

[Bob Lovely]

Originally posted by lukpac


Well, if you're in an area where reception is perfect. Get in the fringe a bit, and the background noise starts to get in the way. Not as much of a problem with more "compressed" stations since the signal is louder.

I kinda like that compressed FM sound myself...

Luke,

Does that mean you are glutton for punishment? (rhetorical). I understand the whole "broadcasting" reason for making stations louder but I was in my posting referring to optimum signal conditions. When I lived in Madison I always though WORT-FM had great sound. Back in the 70's and 80's the old WIBA-FM was a great sounding FM station.

Bob

[lukpac]

Originally posted by Bob Lovely
I understand the whole "broadcasting" reason for making stations louder but I was in my posting referring to optimum signal conditions. When I lived in Madison I always though WORT-FM had great sound. Back in the 70's and 80's the old WIBA-FM was a great sounding FM station.

Well, the thing is, most often listeners will not have optimum signal conditions. Few people listen to the radio on their stereo with a 14 foot antenna on a 40 foot tower behind their house. They listen in the car or with some smallish indoor antenna. If they can't hear the music over the noise, they'll tune out.

I don't listen to WORT much. WSUM is finally on the air at 91.7, although I don't listen to that all that much either. That's broadcasting from near Belleville, and the signal isn't that strong to begin with, so reception in Madison is often less than optimal.

[Bob Lovely]

Originally posted by lukpac


Well, the thing is, most often listeners will not have optimum signal conditions. Few people listen to the radio on their stereo with a 14 foot antenna on a 40 foot tower behind their house. They listen in the car or with some smallish indoor antenna. If they can't hear the music over the noise, they'll tune out.

I don't listen to WORT much. WSUM is finally on the air at 91.7, although I don't listen to that all that much either. That's broadcasting from near Belleville, and the signal isn't that strong to begin with, so reception in Madison is often less than optimal.

Luke,

Typically, in Urban areas, FM signals are strong enough to be heard on any type of Radio, Stereo, or Boombox. When you get 20 or more miles out from the transmitter site, your point makes more sense. WORT-FM sounds great on a high quality Tuner--naturally dynamic with very little added compression.

Bob :)

[lukpac]

Originally posted by Bob Lovely
Typically, in Urban areas, FM signals are strong enough to be heard on any type of Radio, Stereo, or Boombox.

Well, the thing is, broadcasters don't want to limit their range to the urban areas directly surrounding the transmitter. The louder the music is in relation to the static, the better...

[Bob Lovely]

Originally posted by lukpac


Well, the thing is, broadcasters don't want to limit their range to the urban areas directly surrounding the transmitter. The louder the music is in relation to the static, the better...

Luke,

I understand why broadcsater do what they do--I grew up in a broadcast home. But with a 100kw or 50kw transmitter and good tower height all this added compression is not really an engineering neccessary!

Bob

[lukpac]

Originally posted by Bob Lovely
I understand why broadcsater do what they do--I grew up in a broadcast home. But with a 100kw or 50kw transmitter and good tower height all this added compression is not really an engineering neccessary!

I assume you meant "necessity"...

No matter how far you push the limits, that's only so far. Adding compression makes things more "workable" for a longer distance. Simple as that.

[Bob Lovely]

Originally posted by lukpac


I assume you meant "necessity"...

No matter how far you push the limits, that's only so far. Adding compression makes things more "workable" for a longer distance. Simple as that.

Luke,

Yes, I meant necessity, thanks! I cannot argue with your point for fringe area reception quality.

Bob

[Grant]

Originally posted by Bob Lovely


Grant,

Clearly, I understand your point. Please provide some examples of where you have done this? I am curious!

Bob :)
I can't think of anything at the moment, but Al Wilson's "Show And Tell", and Donald Fagen's "Kamirikaid" CD are two examples.

[Bob Lovely]

Originally posted by Grant

I can't think of anything at the moment, but Al Wilson's "Show And Tell", and Donald Fagen's "Kamirikaid" CD are two examples.

Grant,

I suppose with Show And Tell you give it some added "body"--a song we have talked about before. On Show and Tell, I just EQ it up a bit on the low end (100hz). Kamirikaid is a surprising choice. That is a pretty good sounding recording, as is. Try to think of some other examples, if you can, bceause this is a very interesting subject.

Bob :)