Thanks for the advice. The sytem we are looking at would be primarily for vocals but capable of handling the input of bass, guitar and drums at a 75%(vocals)/25%(instrumentation) mix, just to help balance the sound for a small bar gig (150 or less people). Guitar player is using a Mesa Boogie (50 watt) combo through a 2x12 cab and I am using a 300 watt head through a 1x15 cab. Drummer is not a gorrilla, he is very volume conscience.
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PA system help
- Thread starter bluemonk
- Start date
Don't forget that if you want some 'free' amp power, use a compressor either just before the power amp - or, if you have a system EQ, try to get the compressor before the EQ; so it goes board mix, compressor, EQ, amps.
Part of the reason you'll commonly hear advice like "amp power should be so-many-times the speaker rating" is that folks aren't considering the use of compressors in the chain. With proper compression you can perfectly-well run an amp right at its max continually - it's not hard on the amp at all, but remember that the average power being dissapated in the speaker can be considerably higher with compression than without, but on the other hand the speakers aren't seeing repetitive extreme transients, like is the case with running no compression, and an over-sized amp for Headroom.
I've helped several bands with their PAs, and investment #1 is usually a compressor for the mains! It's truly the equivalent of literally AT LEAST doubling your amp power.
Our band runs twelve channels of compression; one in the insert of each of eight input channels, a stereo pair for the mains, and another pair for the monitors. If we only had two channels though, no doubt it would go as specified above. It is amazing what a difference those two channels make.
Our band played a very small gig not long ago - a private party at a house. We used electric drums, and ran processed guitar and bass right to the board. Because of compression we were able to run a powerful, full-sounding, room-filling audio mix at very low levels! Now the individual channel compressors have much to do with having a good mix with no soundman - they're really 'icing on the cake' compared to the much more important mains compression.
I helped out a local band a few years ago that was running an old powered Yamaha board that featured 75W per channel. They had surprizingly efficient old Cerwin Vega speakers, but seventy-five watts?! I amazed'em! -I threw a stereo compressor and a dual 15-band EQ in the chain; the compressor let them run pretty-much full-time full power, and the EQ let me dump-out those power-robbing lowest freqs from the system. They ran two guitars, three vocals, and even a little kick drum through the system (in fact one of the guitars ran straight to the system with no amp), and they had plenty - I'm serious, I mean PLENTY - of power for large rooms, and even handled a couple outdoor-under-a-big-tent gigs just fine. Bass G. had a couple hundred watts by itself through a stage amp; drums were played by a full-time fortissimo drummer, and actually got pretty much bleed through the drummer's vocal mic.
compression, people - I'm tellin' ya: I consider it manditory for ANY PA.
Joe
Part of the reason you'll commonly hear advice like "amp power should be so-many-times the speaker rating" is that folks aren't considering the use of compressors in the chain. With proper compression you can perfectly-well run an amp right at its max continually - it's not hard on the amp at all, but remember that the average power being dissapated in the speaker can be considerably higher with compression than without, but on the other hand the speakers aren't seeing repetitive extreme transients, like is the case with running no compression, and an over-sized amp for Headroom.
I've helped several bands with their PAs, and investment #1 is usually a compressor for the mains! It's truly the equivalent of literally AT LEAST doubling your amp power.
Our band runs twelve channels of compression; one in the insert of each of eight input channels, a stereo pair for the mains, and another pair for the monitors. If we only had two channels though, no doubt it would go as specified above. It is amazing what a difference those two channels make.
Our band played a very small gig not long ago - a private party at a house. We used electric drums, and ran processed guitar and bass right to the board. Because of compression we were able to run a powerful, full-sounding, room-filling audio mix at very low levels! Now the individual channel compressors have much to do with having a good mix with no soundman - they're really 'icing on the cake' compared to the much more important mains compression.
I helped out a local band a few years ago that was running an old powered Yamaha board that featured 75W per channel. They had surprizingly efficient old Cerwin Vega speakers, but seventy-five watts?! I amazed'em! -I threw a stereo compressor and a dual 15-band EQ in the chain; the compressor let them run pretty-much full-time full power, and the EQ let me dump-out those power-robbing lowest freqs from the system. They ran two guitars, three vocals, and even a little kick drum through the system (in fact one of the guitars ran straight to the system with no amp), and they had plenty - I'm serious, I mean PLENTY - of power for large rooms, and even handled a couple outdoor-under-a-big-tent gigs just fine. Bass G. had a couple hundred watts by itself through a stage amp; drums were played by a full-time fortissimo drummer, and actually got pretty much bleed through the drummer's vocal mic.
compression, people - I'm tellin' ya: I consider it manditory for ANY PA.
Joe
Thanks - glad to be of help.jondog said:
Yes, I can explain the position of the compressor in the signal chain: We can assume that generally-speaking, the board channel EQs (and more importantly don't forget, microphone choice and position for guitar amps and drums) are used to adjust the tone (what's that word - 'tambre'?) of the voices and instruments - like so it would sound best in a pair of million-dollar headphones - and the EQ is for trying to get the room and the system to sound like that - to 'flatten' the overall system response; to compensate for the composite errors and deficiencies between this 'perfect' master-mix and the listener's ears.
You want the compressor's detector to hear the proper, 'flat' mix. For exapmple - if you turn UP a certain range of the mains EQ, it means you need that range to be louder than it would be without, of course, but the compressors whole job is to not let stuff get louder. So if the compressor were after the EQ in this case, then room-volume-wise, it wouldn't let this range of frequencies 'stick-out' like you wanted - it'll still stick out relative to the other frequencies, but the compressor is now more sensitive to this range (from being after the EQ) and will tend 'crush everything else down behind this range', making it sound like the system is dropping-out a little sometimes - a certain weak sound. This is one thing that can contribute to one of the infamous compressor side-effects called 'pumping' (what most often causes it, though, is probably too fast of an attack time along with too high a ratio)! Now keep in mind that this is not totally cast-in-stone - unless you have a very radical EQ setting (which is an indication of other problems), inwhich case the pumping could get quite noticeable if you put it after - otherwise before or after doesn't make all that much difference - and either way, it's way, way better than no compression!
See what I mean, though? The sound comes out of the board the way you want it, so that's how it should be compressed. The EQ should be just to make the room sound like the board.
One interesting situation that goes against this rule is when you're trying to get maximum efficiency from a smaller system by rolling-off the far-low-end freqs on the mains EQ (< 30Hz or 40Hz). In that case you're fighting yourself a little, because if you put the EQ after the compressor, the compressor is still 'hearing' these sub-lows, hence it'll tend to pump-down the overall volume, especially if there's a bassy kickdrum in the mix! Because of this, if your main problem is an under-sized system (especially with full-range speakers), but the system you do have runs nice and flat (no radical EQ-settings needed), then there are two reasons to run the compressor AFTER the EQ: 1) you can roll-off the lows to get the most percieveable volume per watt of available amp and speaker power, without the compressor pumping-down on lows that aren't ending up at the speakers anyway. 2) Running the compressor very-LAST provides the most speaker protection - which is not a bad idea if you're trying to push everything to it's absolute-max.
I gotta get back to work. Maybe I can write more later...
Joe
Shoot, I was thinking you meant a $4,600 system and was about to jump in and fix you right up. Oh well.bluemonk said:
12 Channel Powered mixer with two 400 watt amps, huh? I assume you're talking about a Behringer PMH3000 or PMH5000. If this is the case, just be aware that in order to get close to the 400 watt rating you'll have to push the "Trim" level for each channel you will be using to it's maximum setting, and set the "Main 1" level to at least "unity gain" ("0" setting on the slider). I have a PMH5000, and while it works well for my purposes, I'd say the "400 watts/channel" rating is a bit LIBERAL on Behringer's part.mwm70 said:
- Ugly.
I'm currently in two bands... One has their own soundman and P.A. equipment. I use the Behringer along with a Link Removed for the other band. We use inputs 1 through 5 for vocals, 6 through 10 for micing electric & acoustic guitars & bass (just to fill out the sound a bit) & 11/12 on the snare & kick. The stereo channels aren't being used for the most part. Please note that my praises/criticisms below take into consideration that this mixer is NOT in the league of professional grade gear.
Pros:
- Cheap! C'mon, a 20 channel board (12 mic channels) with 400watt/channel amp built in, for $550? I swallowed the bait, hook, line & sinker on this one.
- Light & portable... between the Behringer and the Dawn, setup & breakdown is a breeze. In most cases we're able to get by without any monitors. For outdoor gigs we'd bring along a pair of Yamaha 15" speakers and use them to suppliment the Dawn. Since we have no soundguy in this band, I setup the mixer on the side of the stage near me (control freak that I am
).
- Hasn't failed us yet... Keep in mind though that I've only had it since around September and we've only used it on a half dozen gigs so far so that's not saying much I guess.
- Pretty much self contained & plug&play... Since it has the onboard efffect processors and seven band graphic EQ, you don't really need any other outboard processing equipment.
- The reverb & delay effects on the processors are decent. It's nice having two separate processors so we set one type of reverb for vocals and another type for the acoustic guitars & drums.
- It has separate monitor sends and sub out so you can expand it's power cababilities by using it with external power amps.
Cons:
- While we have been able to attain a volume level that suits our playing style and the places we play (mostly churches, coffee houses and retreat centers), the 400watts/channel seems to be a generous statement by Behringer. It seems more like half that (even with running a 4ohm load on each channel).
- Not the most musical EQ I've ever heard on a mixing board. It's not horrible, but it's not even close to say, Soundcraft or A&H.
- On the equalizer, 7 bands isn't nearly enough to effectively EQ out feedback... The band width is too wide and you loose too much when you cut back on any of the sliders IMO.
- I have to admit, I keep waiting for the other shoe to drop. From the reviews I've read of other Behringer mixers, I'm anticipating some sort of problem down the road. Since this band doesn't play out as much as the other band I'm in, I'm not terribly worried (I have another mixer & power amp as a backup if neccessary).
Overall, I'd say I'm pretty pleased with it so far. I played in a band a few years ago that used a Mackie 808M mixer/amp combo and I'd say this compares favorably.
- Ugly.
Pros:
- Cheap! C'mon, a 20 channel board (12 mic channels) with 400watt/channel amp built in, for $550? I swallowed the bait, hook, line & sinker on this one.
- Light & portable... between the Behringer and the Dawn, setup & breakdown is a breeze. In most cases we're able to get by without any monitors. For outdoor gigs we'd bring along a pair of Yamaha 15" speakers and use them to suppliment the Dawn. Since we have no soundguy in this band, I setup the mixer on the side of the stage near me (control freak that I am
).- Hasn't failed us yet... Keep in mind though that I've only had it since around September and we've only used it on a half dozen gigs so far so that's not saying much I guess.
- Pretty much self contained & plug&play... Since it has the onboard efffect processors and seven band graphic EQ, you don't really need any other outboard processing equipment.
- The reverb & delay effects on the processors are decent. It's nice having two separate processors so we set one type of reverb for vocals and another type for the acoustic guitars & drums.
- It has separate monitor sends and sub out so you can expand it's power cababilities by using it with external power amps.
Cons:
- While we have been able to attain a volume level that suits our playing style and the places we play (mostly churches, coffee houses and retreat centers), the 400watts/channel seems to be a generous statement by Behringer. It seems more like half that (even with running a 4ohm load on each channel).
- Not the most musical EQ I've ever heard on a mixing board. It's not horrible, but it's not even close to say, Soundcraft or A&H.
- On the equalizer, 7 bands isn't nearly enough to effectively EQ out feedback... The band width is too wide and you loose too much when you cut back on any of the sliders IMO.
- I have to admit, I keep waiting for the other shoe to drop. From the reviews I've read of other Behringer mixers, I'm anticipating some sort of problem down the road. Since this band doesn't play out as much as the other band I'm in, I'm not terribly worried (I have another mixer & power amp as a backup if neccessary).
Overall, I'd say I'm pretty pleased with it so far. I played in a band a few years ago that used a Mackie 808M mixer/amp combo and I'd say this compares favorably.
- Ugly.
