dembits

Limiters, compressors, and crossovers

18 posts in this topic

I am having trouble finding a plain English explanation of what a limiter, compressor, and crossover do and why I may or may not need them. I have a basic idea of what the crossover does, but if anyone can give me an explanation or a link to a decent article on the topics I would really appreciate it. I would like to have the best possible sound quality, but I don't want to spend my money on something when I don't even know what it is doing for me.

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A "Compressor" is a device that the when the audio signal level on its input reaches a selected threshold level it starts to limit the output level. This limiting is expressed as a ratio such as 4:1, 6:1, 8:1 etcetera. So the louder the input gets the more the output level is pulled down. The larger the ratio the more the output gets pulled down.

A "Limiter is the same thing as a Compressor except it is like a governor on a car. Just like when a car reaches a certain speed it can go no faster because of the governor when the Input to a Limiter reaches a selected threshold level the output is limited to that level regardless of the input. Most good Compressors can be set to run as a Limiter if needed.

A Crossover comes basically as two filters one is a High Pass filter the other is a Low Pass filter. When put together one will pass only the Low Frequencies and the other will pass only the High Frequencies. The point at which the filters intersect is called the Crossover Frequency. A Crossover separates the audio signal into two or more frequency ranges and can be either Passive or Active. Passive Crossovers generally come inside a speaker cabinet and don’t need any setting up. They do however use up a little amplifier power as they are attached between the speakers and the amplifier. Active Crossovers are electronic filters that go in the signal path just before the amplifiers and split the audio signal so that the lows go to one amplifier the Mids go to another and the Highs go to another. This way you can better power match the amps to the speaker components and the amps can work more efficiently as they are only amplifying a certain band of frequencies not the entire audio frequency range.

There are a few good books I would recommend:

"Sound Check: The Basics of Sound Systems" by Tony Moscal

"Guide to Sound Systems for Worship" by Jon F. Eiche

“sound Reinforcement Handbook” by Gary Davis & Ralph Jones

"Audio Engineering for Sound Reinforcement" by John Eargle and Chris Foreman

I believe all the above mentioned books can be ordered online.

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So, if I get a crossover, do I still need a limiter/compressor and vice versa? I have an XLS 602 amp where I am running 2 MTX TP-112 speakers parallel on one channel. I am considering either adding 2 more MTX's on the other channel or one JBL JRX 118S. Should I get the crossover, the compressor, or both. Also, for a fuller, crisper sound would it be better to get the two additional 2-way MTX speakers or the JBL sub? I am trying to do mobile djing for small to medium sized events where I would be playing mostly pop, hip hop, and electronica music. Finally, I have an equalizer that I used with my home stereo system. Is that any different from the pro sound ones that you see at guitar center, etc. Aside from the fact that it cannot be rack mounted and it only has RCA inputs, can it still be used with the setup listed above. Thanks in advance. Because of this forum, I went speaker shopping with my dad last week to help and got to tell the salesman that he was full of $h*t.

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Hi Dembits,

Here's the bottom line:

With the equipment you currently have you don't need a compressor/limiter or a crossover. If you buy additional full-range speakers, see previous statement.

If you buy the sub(s), however, you would need a crossover. Keep in mind a crossed-over system requires a separate amp channel(s) for the highs and lows. In other words (with a single two-channel amp) all of your full range (high) speakers would have to be on one amp channel and your sub(s) (low) on the other.

As for better overall sound I suggest a BBE Sonic Maximizer, they start at $100. (To the best of my knowledge; Crown does not offer this type of processor, so I hope I can mention it here)

Your home EQ would probably work, but you can buy a commercial one for around a $100. If you get the BBE unit, you may not even need additional EQ.

Future shopping??? Consider a "warehouse" website that offers a wide variety of commercial equipment. A few of my favorites are , www.americanmusicalsupply.com, www.prosound.com, and www.planetdj.com. These (and similar) websites are great way to compare prices and features. Most of the time you can go to a companies website, like Crown, and view manuels and specifications on the items that specificly interest you.

Hope this helps,

Chris

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Dembits,

Here is some food for thought...

Probably in a DJ enviroment your MTX's are shallow on the bottom end. I see that they have a mid/high horn in them which should really overpower the 12's, espically on the low end?? :unsure:

If you are going to DJ you will (in the end) have to have some subs. To minimize your expense now, why not try a sub running off one channel and keep your 2 MTX's on the other? I really think a good sub would be the biggest bang for your buck and you would really, really hear the difference. Also using a crossover for your sub would really clean up the quality of sound you are getting from your MTX's because you would only send freq. of say 90hz - 100hz and up to the MTX's.

You will be suprized how much cleaner they will sound.

But don't skimp on the sub. I would recommend an 18" pro sub, no smaller than a 15". Check the websights that Chris recommends they also have subs.

I don't think the Sonic Maximizer has a sub out so you will need a crossover. You might even check ebay, I saw several Rane crossovers listed there yesterday at low prices. (Rane AC22) Rane even makes a cheaper line called MOJO I am just not sure of the model number for the 2 way crossover. Or you might check for a DBX prof. (DBX 223) they are a little cheaper that Rane.

Hope this helps

David

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Okay, so if I get a crossover and a sub, how will the setup hook up together? Will I be splitting things after the amp and before they get to the speakers? So channel one on the amp would go to the crossover and out to the 2-way speakers and channel 2 of the amp will go to the crossover and then to the sub? Will that cause my amp power to suffer? If so, will it be enough to make it a problem? I am currently giving my speakers good power and would like to keep that going.

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Ok here's how it would hook up:

From your source (CD player) to your mixer, out of your mixer (and for this setup probably run out of you mixer (preamp) mono, then into your EQ. If you run mono out of your mixer you will only use one channel of your EQ. Then run out of your EQ (one channel) into your crossover using is as a mono crossover. Out of your crossover straight into your Crown. (using all coax cables)

Then using speaker wire use One channel for the high Freq. 100hz and up to power your MTX's and one channel for the Lows 100hz down for your sub.

Just remember the Crown amp is the last piece in the chain before your speakers.

The "active" crossover is considered a line level piece of gear and processes the signal in the same manner as your pre amp, mixer, or EQ.

The crossover inside of your MTX speaker is a "passive" crossover and processes a high voltage signal between the amp and the speakers. The crossover you need

above is an "active" type.

With this set up you will still have plenty of power until you decide to add additional speakers.

Hope this helps, if you have questions let me know

David

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Okay, that makes sense, but if I am not using an EQ, then would I go from stereo out from the mixer to MONO in on the crossover and continue the chain of connection? Also, while I am not questioning the hookup method, it doesn't make sense to me. If I hook up the crossover MONO before the amp, how does it know to distribute only high frequencies to channel one of the amp and only low frequencies to channel two? Apparently, the crossover is smarter than I am.

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Okay, that makes sense, but if I am not using an EQ, then would I go from stereo out from the mixer to MONO in on the crossover and continue the chain of connection? Also, while I am not questioning the hookup method, it doesn't make sense to me. If I hook up the crossover MONO before the amp, how does it know to distribute only high frequencies to channel one of the amp and only low frequencies to channel two? Apparently, the crossover is smarter than I am.

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Your Crossover (depending what you buy) will most likely offer 2-way (bi-amp_ stereo) or 3-way (tri-amp mono). You could run 2-way stereo, but with the speaker set up we are discussing here is the problem. You only have 1 amp which is a 2 channel amp. If you run in stereo you would need 3 channels: Front Left, Front Right and Sub. Since you only have 1 am (2 channels) I am recommending to use one channel of your amp (ch A or 1) for both left and right front speakers wired in parallel and use the other channel (ch B or 2) for the sub.

Now back to the hook up. Yes, you would run direct from your mixer to the crossover. For the speaker set up we are talking about, I would use the mono out on your mixer if it has one. The crossover would have one "mono" input. And it would have 2 outputs: A "high out" and a separate 'Low or sub out". The crossover would have adjustments for both gain and crossover point (hz) for both outs. (high and low/sub) The 2 outs we are talking about would go to your Crown.

Say "high out to ch. A and Low/Sub out to Ch. B)

When you are ready to buy, if you tell me which crossover you are looking at I can be a little more specfic as to the exact settings.

Please let me know if I am clear here? :blink:

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I am considering the DBX 223 crossover. Will that one handle my situation well? Also, I will not have enough cash for the subwoofer for a little while. Is it still a good idea to get the crossover now so that the two main 2 way speakers do not get the lowest frequencies, or should I wait until I get the sub to also get the crossover. If you recommend that I get the crossover now, will the hookup be any different? By the way, thanks for all of the help. I have learned a lot from everyone that has responded to my 3 million questions.

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Dembits,

You don't need a crossover until you get the sub. You need all of your signal (20hz - 20,000hz) going to your MTX's for now. If you crossover (filter) your signal without a sub your removing bottom end from your MTX's and hurting your bottom end.

When you are ready the DBX 223 would be perfect.

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If you have a little $$$ to spend on your sound; I still recommend a BBE Sonic Maximizer(either the 362 or 482I. The 482I has a newer/better processing chip, but the the 362 is better than nothing.) My 482 is the best piece equipment I own. Easy to hook up, easy to operate.

Chris

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If you have a little $$$ to spend on your sound; I still recommend a BBE Sonic Maximizer(either the 362 or 482I.  The 482I has a newer/better processing chip, but the the 362 is better than nothing.)  My 482 is the best piece equipment I own.  Easy to hook up, easy to operate. 

Chris

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Chris,

Could you be a little more specific about what exactly the 482I does and how/what it did for your system?

Thanks

David

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Hi David,

BBE's website (address is below) gives a pretty good explanation. Me personally; I think it makes DJ sound go from a "AM clock-radio sound" to making the audiance think there's a live band in the room. It makes the sound much more "warmer" and "life-like" and it's controls help compensate for bad room acuostics. Read the info at the address below and drop me a note if you have anymore questions.

Chris ;)

http://www.bbesound.com/technologies/BBE%5FHDS/

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If you have a little $$$ to spend on your sound; I still recommend a BBE Sonic Maximizer(either the 362 or 482I.  The 482I has a newer/better processing chip, but the the 362 is better than nothing.)  My 482 is the best piece equipment I own.  Easy to hook up, easy to operate. 

Chris

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The sonic maximizers are not what you would want or need they do nothing except add highs and lows to your signal, hense sucking the mid frequencies out of everything. If you want to blow speakers and hear your speakers fart go ahead and buy a sonic maximizer. They are tools used for certain things to try to fix a system is not using it as a tool.

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Although the BBE Unit is a solid audio effect unit, it is still just a unit that colors the sound of your system. Have you thought about buying powered Subwoofers? These come with Amplifiers and crossovers built into them which would allow you to power your mid/high boxes with your existing amp and still maintain a stereo image. Your EQ unit could still control your overall sound and allow you to tune your rig to the room you are in on any given day. I hate to write this down here, but "Mackie" actually makes a single 18" subwoofer that kicks *beep* for DJ rigs and I have a pair in service with our "C" rig here, which we use for all our DJ shows. Michael Oliver - Prime Time Entertainment, Tracy, CA

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Although the BBE Unit is a solid audio effect unit, it is still just a unit that colors the sound of your system.  Have you thought about buying powered Subwoofers?  These come with Amplifiers and crossovers built into them which would allow you to power your mid/high boxes with your existing amp and still maintain a stereo image.  Your EQ unit could still control your overall sound and allow you to tune your rig to the room you are in on any given day.  I hate to write this down here, but "Mackie" actually makes a single 18" subwoofer that kicks *beep* for DJ rigs and I have a pair in service with our "C" rig here, which we use for all our DJ shows.    Michael Oliver - Prime Time Entertainment, Tracy, CA

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