Being the Gear Head that I am, I find myself constantly browsing the Internet and the music catalogs to see what new gear is on the market. Lately however, I have changed my focus to watch for what gear has been on the market for a long time and continues to be a great seller. Surprisingly, most products in the music industry last less than 5 years before they go through an overhaul, upgrade, or are phased out completely and replaced by a new model.

In my research, I was able to find very few products that have stood the test of time. One of these products is the 3630 compressor from Alesis. The 3630 was first introduced in 1991, giving it an unprecedented run of almost 15 years on the market. Furthermore, I spoke with Alesis and they said it is not going to go away anytime soon. I decided that we should see what makes this compressor one of the most popular compressors on the market today.

The 3630 Compressor/Limiter/Gate by Alesis



The 3630 is a dual channel compressor / limiter / gate that comes in a single rack space. The 3630 holds many features that you will not find in a compressor in the 3630’s price range. Let’s take a quick look at some of these features:

Stereo or Dual Mono operation – The 3630 can be used in stereo applications where you need a compressor on the left and right side of a stereo signal. It can just as easily be used as two completely separate compressors so that you can compress two different instruments with separate settings.

Peak or RMS response – This allows you to set up the compressor to work with either signal peaks, or an average signal level of an entire program. For example, you would probably want to use the Peak function on drums, while the RMS function might be more suited to vocal performance.

Hard Knee / Soft Knee Response – The 3630 allows you to set the compression to work in "Hard Knee" or "Soft Knee" mode. The hard knee mode is considered to be a more severe compression, while the soft knee mode will roll of the compressed signal more naturally. Both have their applications, and can be a matter of personal preference depending on the instrument or the mix.

Individual bypass switch on each channel - This makes it easy to compare the original signal with the compressed signal on each channel.

Built in stereo or dual mono gate - Gates are of invaluable use if you have an unwanted sound in your signal chain such as a hum or tape hiss. You can set the gate so that it does not allow a signal through unless it is louder than a specified level. The gate will open when the signal strength exceeds this point. This does also allow the offending sound to come through, but it is usually largely inaudible when covered by louder sound that caused the gate to open. Once the sound level of the signal drops below the settings of the gate, it will close and not allow the background sound to come through.

Light Meters - The 3630 also incorporates a 12 LED display on each channel to show you the amount of gain reduction the unit is applying. There is also a second set of LED’s that show you the input/output levels. This allows you to get a good idea of what functions the unit is performing with a glance. There is even a set of LED’s that show you the status of the gates operation.

Side Chain Connections - The side chain connections gives you the option of two entirely different, yet useful functions that are usually reserved for much higher priced compressors. These function are called "ducking" and "Frequency Dependent Limiting".

Ducking - Ducking is the process of using one signal to effect the dynamics of another signal. Here is an example. We have all heard those commercials on the radio and television where the music is loud until someone starts speaking. The music gets lower when the voice comes in so it can be heard. Then the voice stops, the music gets loud again. To do this, the engineer runs the music through the 3630 inputs like they would in normal operation, but the microphone for the voice is inserted in to the sidechain jack. The microphone then becomes the trigger for initiating compression. When a voice is present in the microphone, the compressor kicks in and brings the music level down. When the voice stops, the compression also stops and the music level comes up again. This is great for post production for documentaries and also for the singer that is trying to be heard over a noisy band.

Frequency Dependent Limiting - One of the most common forms of frequency dependent limiting is the function of De-Essing. This is the process of removing the excessive "sss" sound that is made when saying words that start with the letter "S". This happens in everyday speech, but is not noticeable to most. However, a microphone seems to have a way of accentuating this sound. By inserting an equalizer in the sidechain, you can dial down the frequencies that cause this phenomenon, therefore making the speaker or singer sound more natural.

As you can see the 3630 has many options and many uses, both for the studio and live sound. The manual does a great job of going more in depth on these features and how to use them. There is even a great explanation of compression, limiting, and gating. It is very well written and easy to understand.

The Sound Test

Since my forte is guitars, I decided to keep my review in this area. I tried the 3630 with acoustic, electric, and bass guitars with very satisfactory results.

Acoustic – The acoustic guitar was my favorite use of the 3630. I have found in my experiences that compressing an acoustic guitar with a soft knee style of compression makes the transition between strumming and single sting fingerpicking very smooth. The 3630 did a great job in tightening up the articulation of my acoustic guitar sound and removing the muddiness that can mess up an acoustic mix.

Bass – The bass guitar was sounded great through the 3630. When playing slap bass styles, you can really run into some heavy clipping. The 3630 on a limiting setting can really tame these level spikes and give you a very consistent sound.

I read in reviews that people were having problems with a clicking sound (particularly on bass guitar) when the compressor would turn on and off. I tried to duplicate this problem to see if it was really a design flaw in the unit. I was unable to get the clicking to manifest itself unless I boosted the input signal to a very high level. This level was much higher than I would ever use with a compressor, so I believe that the people having this problem are creating it themselves due to misoperation. In my view, you should only use the minimum amount of compression to get the desired result.

Electric Guitar - For the electric guitar, I do use compression, but my general rule is to only use it if it’s needed. Sound level dynamics are a very important part of many guitar players styles, so compression can often have an adverse effect on electric guitar sound. Many players forego the use of a compressor on the electric guitar altogether. I do find that most of my own use is on clean electric guitar sounds since overdriven sound have a tendency to compress themselves. I found the 3630 to be a very transparent compressor for the electric guitar. I found it useful using the sidechain function with an equalizer to remove the 60 cycle hum from single coil pickups. This is another great example of "Frequency Dependent Limiting".

Closing Thoughts

Overall I found the 3630 to be pretty straight forward and extremely easy to use. If you have even a limited knowledge of compression, you should be able to plug an play without even reading the manual. I do however recommend reading the manual for some insight and tips that are very helpful.

If used properly, a compressor can be a valuable tool in a studio or live application. The 3630 is a great unit for both situations. It is easy enough for a novice to figure out, yet has plenty of features to satisfy a professional. I have found that Alesis does a great job of putting together gear that is both educational as well as functional. The 3630 is no exception.

Coming in at a price tag at just under $100, the 3630 is a very small investment to make on a dual channel compressor. The quality of the sound and functionality of this unit puts it in a class that would compete head to head with other units costing five times as much or more. For this I award the 3630 both the Guitar Gear Heads "Approved" award as well as the "Rig Ready" award. This is another great Alesis unit, and is an amazing value for the price.



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