Adam_Dawson Posted April 25, 2005 Author Share Posted April 25, 2005 Thanks Mr Si! The logic tops have been good for what I do, which is why I'm thinking of getting their bass cabs too for the band stuff - it's just the dilemma of powering them. Maybe I should just use the mixer's amp for the monitors and run everything through the Chevin Q6 if and when I can afford the subs! (that's the beauty of doing the solo acoustic stuff - it means I can save up quicker!) As the Q6 has got four channels (350w into 8 Ohm) would that be a good idea for the four components of the FOH setup? Leaving the mixer free for two monitor sends. Where would the active crossover go? At the EQ end near the desk, or at the Amp end on stage? Any recommendations for a decent one? I really appreciate your help, it's much better than just blundering on like I have been doing! Link to comment Share on other sites More sharing options...
Mr.Si Posted April 25, 2005 Share Posted April 25, 2005 Well, if you get a generic one like the dBx 233 (like mine) then you would normally put it at the front with the amps - put the sends from L + R into that, then take the 2 HF outputs to 2 inputs of the amp, and the 2 LF outputs to the other two inputs of the amp. But other units such as BSS OmniDrive etc, are really rather much better and have more outputs, plus delay and EQ etc, so you can control the system from your mixing console. (But that requires more return channels on the multicore). Si I'd go omnidrive if I were you. Link to comment Share on other sites More sharing options...
bruce Posted April 25, 2005 Share Posted April 25, 2005 If I'm to do that then I wonder if my Chevin Q6 power amp (which I dont currently use) could power the 400w subs. It gives out 600w into 4Ohms and 350w into 8Ohms (which the subs are) but judging by your previous advice they won't mind just getting 350w. <{POST_SNAPBACK}> Be careful here - the accepted wisdom is that you should err on the side of having the amp more powerful than the speakers..... which does sound a bit back-to-front! The logic behind that is that if the amp is less powerful than the speakers, then it's all to easy to "overdrive" it - crank the volume up to 11, thinking that since the speakers are higher-rated than the amp they'll cope. The problem, however, is that if the amp reaches its limit, it'll start to clip, and this can do nasty things to the coils on your speakers! having said that, I would expect a 350W amp and 400W speakers to be "close enough" to avoid this problem. But listen to the speakers, and if you detect clipping, then back off a bit. Bruce, Link to comment Share on other sites More sharing options...
Adam_Dawson Posted April 25, 2005 Author Share Posted April 25, 2005 Thanks Bruce, that's sound advice (pardon the pun)! If I were to run both 8 ohm tops off one channel in parallel (ie. forget about it being stereo) then would that reduce the impedence to 4Ohms in which case the Q6 can provide 600w which would be adequate? I do like to complicate matters! Also, if I am to get a dbx 223XL crossover (which I probably will, or maybe a behringer Super X pro CX3400 cos it's cheap) then do I just come out of my outboard stereo EQ (another thing to buy! Any ideas?) on XLR's into the back of it. Does that mean that when I adjust the EQ it alters the bass bins too? I guess it does. Link to comment Share on other sites More sharing options...
Adam_Dawson Posted April 25, 2005 Author Share Posted April 25, 2005 I'm just looking at Graphic EQ's and I've seen the Behringer FBQ3102 which claims to have a sub out with adjustable crossover - would this do away with the need for a seperate crossover unit? For the spec look here Link to comment Share on other sites More sharing options...
Mr.Si Posted April 25, 2005 Share Posted April 25, 2005 don't go behringer, not with the stuff you've got. You've got great speakers, you don't want to compromise the sound with behringer stuff. It's cheap stuff, and for a reason. the thing about having the speakers in parallel... that sounds like having 2 speakers on one channel. but then you'd only be giving each speaker 300W which would be less than running it in stereo with one per side. You'd also lose the ability to pan stuff left and right which is a feature you may need sometimes Si Link to comment Share on other sites More sharing options...
Darkfold Posted April 25, 2005 Share Posted April 25, 2005 Behringer sucks. In a big way. Have a look at www.pa-direct.co.uk for amp and speaker ideas, also call em up and ask, they're very helpful Get an adjustable active analogue crossover (cheaper and often sound better than digital). Feed the output from your desk into this, let it separate the signals into high/bass (good ones have adjustable crossover points). Then run its outputs into the amps, I'd suggest a separate amp for the bass bins (just my personal preference) and then you get decent quality signal splitting and you dont have to monkey around rewiring your lovely kit. passive crossovers look good on paper, but their characteristics change as they get hot (takes about 2 hours of hard playing) and you get funny sounds from the bass. Just my £0.02 Link to comment Share on other sites More sharing options...
Adam_Dawson Posted April 25, 2005 Author Share Posted April 25, 2005 Sounds good to me... What about parametric EQ's then? I've never really got on with mine and I'd like to have a seperate 31 band graphic in the long run when I actually splash out and get an outboard rack with some nice toys in it, such as: A couple of stereo graphics (any recommendations for good but sensibly priced ones?) A dbx 266XL compressor/limiter/gate and a nice Effects processor (just reverbs and maybe delay) This way I'd have a seperate EQ for both monitor sends as well as L+R which I assume will be better than the 4 band parametric which Allen and Heath provide on the PA12-CP?? Link to comment Share on other sites More sharing options...
Mr.Si Posted April 25, 2005 Share Posted April 25, 2005 In fact I think you'll find that it's semi-parametric as there's no Q setting (the bandwidth of the shelving) The dBx 1231 (2x31 band) graphic is very good, and not too bad price wise (compared with Klark Technic & BSS). The 1231 is a 3U rack space unit, which provides a longer fader for more dB of cutting or boosting of frequencies. For FX, TC Electronic do some very nice units, I have an "M-One" dual fx unit. Prices are v. good also. Don't worry about Parametric EQ, that's something you won't need right now, I guess. Link to comment Share on other sites More sharing options...
Adam_Dawson Posted April 25, 2005 Author Share Posted April 25, 2005 I wonder if it's possible to still use the internal amp on my mixer for certain things (smaller gigs etc) whilst still making use of the outboard graphic and effects. I'll have to look in the manual as I'm guessing it'll mean using the graphic outs and ins and what-nots that I've never had anything to do with before. As for Effects, has anyone used either the TC G-Major or the M300? Any thoughts? Is it worth putting a compressor in the outboard rack too for vocals? I've had vague reports on this so I'm interested to know if compressing vocals is generally a good idea or not? Incidentally, I've just ordered the Live Sound Manual by Ben Duncan so hopefully I'll get myself a bit more savvy with setting it all up. I'm forever frustrated by doing solo acoustic gigs and not really knowing how to improve my sound. Made worse I suppose by not being out front to hear the true sound. I suppose I should try out a local sound engineering course really and learn the basics of EQ'ing etc... Link to comment Share on other sites More sharing options...
Mr.Si Posted April 26, 2005 Share Posted April 26, 2005 definitely compress vocals, or rather, put a compressor in the insert of the channel(s) - you never know if someone will suddenly ramdomly shout, so you set the threshold accordingly so that it has no effect until they increase their loudness into the microphone enough. Put the ratio at about 1:4 - 1:5 ish, hardknee compression is what is normally used on vocals. Though at the end of the day, it's all about experimentation. (Provided you have time). Like you said before, you could be best using the internal amp for smaller gigs where you don't need subs or something. Also, if you are, then use other amps for FOH and use the internal amp channels for Foldback. That's what I'd do. Si Link to comment Share on other sites More sharing options...
paulears Posted April 26, 2005 Share Posted April 26, 2005 A long time ago in this thread somebody mentioned about the differences between 15" and 18" subs. Oddly, it isn't really frequency response. If you compare specs, you'll find them very similar. Sound wise, they aren't. A lot of it is down to transient response. An 18" driver when subjected to something like a kick drum can shift a huge amount of air - a really solid KICK. A 15" - not quite so much. The poster mentioned Pink Floyd. Well, with wierd sound and low frequency synth content, then what is wanted is bass extension - 15" drivers do this quite well. My experience of 18"'s is that although I prefer them for Kick in the guts drum, they break up a little with real low notes. I suspect it is simply the inertia in the large cone that causes flexing as it tries to reverse quickly. So for a musical sub sound I prefer 15"' - if I need a percussive sound I go with 18". The snag with wanting both is that 18" speakers start to run out of steam below the frequency where 12" drivers in the topsstart to take over, hence the comment about matching sub and tops. If you ever build your own cabinets, the 15" polypropylene drivers sold for car subs have a nice tight percussive sound from a 15" driver. they aren't quite so smooth sounding as say Celestions or JBL's but can give a lot of thump from a smallish cabinet. There's a brand called USBlaster which are quite useful for replacing blown old drivers. They always seem to pep up the bottom end, making it more 'modern' (if that's what you are after) Link to comment Share on other sites More sharing options...
Adam_Dawson Posted April 27, 2005 Author Share Posted April 27, 2005 Thanks guys, I think I'll probably go for the 15" subs, as there will be times when I'll use them without a drumkit, so no kick drum to emphasise. Just getting back to the logic sytems stuff - the tops I've got are the X12's and the bass bins I'm looking at are the X150's which do seem to have a passive crossover in them, (anything below 150Hz to the bottom and anything above 70Hz to the tops - so maybe I won't need all the active crossover stuff. Maybe I will still get it all in the back of my estate car! It would be really nice if I can run it all of the Allen and Heath, as it's cheaper and more portable in the short term. The only thing is that the sub is 500w 40hm, while the tops are 400w 8 ohm. Those scary numbers are coming back again, make them go away!! Link to comment Share on other sites More sharing options...
Brian Posted April 27, 2005 Share Posted April 27, 2005 I wouldn't worry too much about the impedance figures. Well below crossover the combination will look like 4 Ohms-ish; in the crossover region it'll all go to pot; above the crossover point it'll settle down to around 8 Ohms-ish. When a manufacturer quotes a value it's usually the nominal DC value. In real life a driver will very rarely exhibit that figure. Depending on the type of cabinet it's put in the value can drop to around 1/2 - 1/4 of the nominal at some frequencies and rise to around 10 times the nominal at others. Link to comment Share on other sites More sharing options...
Adam_Dawson Posted April 27, 2005 Author Share Posted April 27, 2005 Ok, on the back of the PA12 there is an impedence selector switch (4/8 ohms) although it still gives out 500w eitherway. At the moment its set to 8 as I only run the tops, but if I was to put it into the subs would I choose 4 ohms do you think - then run the tops of the subs. I mean, do you think it'll do any harm to run all this stuff off the PA12? Link to comment Share on other sites More sharing options...
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