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Building up a PA


josh a

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Hello, all.

 

I am considering building up a PA, for band use, rehearsal's, anything I can find a use for it for.

 

Anyhoo, I have been thinking that I will build two Omni 10\'s . I will use them for vocals, and run the drums, bass and guitar (475watt, and 100w, respectively). It will be for small, "underground" gigs. A bit of fun.

 

If I ever need to move to a bigger situation, I will make some Titan 39\'s , or 48\'s .

 

Then I would run the full band through the system or something.

 

On to the mixer and power amp. I understand that I need a mixer and a power amp or a powered mixer. (I also realize that I could have a load of other goodies, not sure what, but I think they are uneccessary for a vocal PA, especially as I am just a beginner) I think it would be better to get a mixer and a power amp so that I can upgrade and change as and when. I think I will need an 8 channel mixer to start off with (say, 3 vox, then if I ever ran the band through have 1 for guitar, 1 for bass, and 3 for drums [kick, snare, over head]). I am not sure what size power amp I would need. If I could get hold of some Eminence Basslite S2010 speakers (I cannot find these in the UK, anyone have a link? Or any info about importing some?) I would have 600 watts. Would I want a 1000watt power amp? 500watt?

 

Also, the Omni 10's are 4 ohms each, so 2 ohms together. I'm not sure what ohm the Titans are, they use one speaker so I assume its about 8 ohms. This would mean the overall ohmage is very low, lower than I've ever seen a power amp handle.

 

Thanks for reading all this, and here goes the fundamental questions:-

 

1. Does the two Omni 10's as a vocal PA sound a good idea?

2. Is an 8 channel mixer a good idea? What brands do you recommend?

3. What size power amp should I get? What brands do you recommend?

4. How would I add in the Titan subs?

5. Is there anything I've forgotten?

 

Thanks for reading, thanks for helping, thanks for C Alex for suggesting this.

 

Any tips or hints welcome!

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Yes stereo mixer goes out in stereo to stereo power amp. The vocals would be panned centre so although not in stereo, half of the signal goes out left and half right. I think that is what you are asking.

 

10's sound a bit small, but Alex usualy spot on, and I don't have experience of the eminence gear. Probably OK for a small combo. If you plan to upgrade later, I'd go straight for horn loaded 15's. Yamaha, Peavey and Soundcraft make good mixers. You definately will need some kind of feedback control, either a 15 or 31 band graphic or a behringer feedback suppressor. The 7 band graphics are OK but alter the sound a bit much for my liking.

Feel the groove internally within your own creativity. - fingertalkin

 

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Tim, the Omni 10's are one of Bill Fitzmaurice's horn-loaded designs. They go deeper and play much louder than the usual direct radiating 15" plus horn-loaded compression-tweeter designs. They have two 10" woofers in each, plus a vertical array of piezo tweeters. The woofers are fully horn-loaded, which increases their sensitivity in the horn-loaded region (from 150Hz upwards) and also lowers their resonant frequency so they put out more bass than a normal direct radiator (even though they are direct radiating in the bass region). Because they use 10" woofers they're crossed over higher than a 15" would be, so you can use these piezo tweeters, and by using a line array of them you increase the power handling and sensitivity, lower the distortion and flatten the frequency response. Anyway, we're not here to discuss speakers because the Omni 10s are by far the best choice!

 

Stereo mixer to stereo power amp is the standard way to feed this. I'd recommend a minimum of 8 channels - if it doesn't cost much more, 12 channels are worth having because there's nothing more annoying that not having enough channels on the desk. Once you have a few backing vocalists, second guitarist, keyboardist, horn players (seem to be quite popular with all the sixth form ska I encounter), then 8 channels doesn't go very far.

 

On the power amp front, you won't actually need much power to get the Omni 10's loud. However power is cheap and more is better. In my experience although PA systems are nominally stereo, they're rarely run like that because if you stick one guitar on the left and one on the right then the audience on the left of the venue only hear half the guitar sound. So if you get a relatively powerful amp, then you could run one Omni 10 on each channel for now, and when you add the Titan subs you can stick both Omnis on one side and the Titan(s) on the other. 500W-1000W per channel at 4 ohms should be fine.

 

A 31 band graphic EQ or dbx driverack would be good to EQ the system in and deal with feedback, though IMO you're better off positioning the PA and mics right and keeping the overall SPL down than messing with ringing out the PA.

 

Alex

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Most decent power amps run down to 2 ohms on each side and 4 ohms bridged. I'd suggest that whatever you buy should be able to do that, as it gives a lot more versatility.

 

If you're running the Omni's as top speakers plus a Titan as a sub, you should use an active crossover to send the mids and highs to one amp channel, and the lows to the other amp channel. There are quite a lot of handy DSP based single rackspace devices out there, that can deal with all your EQ, feedback suppression, and crossover requirements in one go. However, I'd leave that until you build the Titan.

 

Another option would be to build Omni 15's, which would preclude the need for a sub.

 

Alex

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If you plan to install the system and not move it, graphic equalizers can be great. However, if it is going to be mobile, I have always found graphic equalizers to be much inferior to a decent 3-band fully parametric equalizer. The latter will let you quickly ring a room by setting a high-Q, boosting, and sweeping the frequency while having an adjustable low and high band will allow you to find the sweet spots for the room.
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Originally posted by getz76:

If you plan to install the system and not move it, graphic equalizers can be great. However, if it is going to be mobile, I have always found graphic equalizers to be much inferior to a decent 3-band fully parametric equalizer. The latter will let you quickly ring a room by setting a high-Q, boosting, and sweeping the frequency while having an adjustable low and high band will allow you to find the sweet spots for the room.

It would be moved to different places a lot.

I didn't really understand that latter part of the post, but I know the difference between a parametric eq and a graphic one. Halfway there. :D

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Regarding T39 vs O15 as a sub:

 

"The strong bass response of the O15 is why I don't recommend using it along with a sub; it really doesn't need it. One could use the O15 sans midrange and tweeter as a sub, and with one cab it's almost as good as the T39. However, what is very different between the two is that the O15 operates as a direct radiator below 100Hz, not a horn, so response will not get better with stacking as it will with the T39. That shifts the advantage to T39 with only two cabs. As far as the build complexity is concerned the T39 is only slightly more complex than the O15, so I wouldn't make that a selling point between the two."

 

Alex

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Im confused. Are you jsut buying the speakers and building the cabs? if so I would sugest jsut buysing some YAMAHA 12" cabs they will do just fine and cost you much less money.

For bare speakers Eminence is great stuff. They hold strong to there workmanship and when something went wrong sent me a replacement speaker no questions asked within 48hours and let me use that box to ship the blows speaker back.

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I like running an active crossover in my rack. This is just personal preferance. The down side to this is that I have to use 2 poweramps. That gets heavy :(

Upside, I never have problems with blowing crossovers in the speaker boxs at a gig. Also, it gives me more play on where the crossover freq. is between the subs and the tops.

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MONITORS for the vocalist. Most mixers have an AUX/BUS out system that you can send to monitors. Maybe powered speakers would work for this. The crate PSM12P's are great for that, even the PSM10P would be fine.

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MIXER: I would suggest getting soemthing that you can grow into. the price differance between and 8 and 16 cannel board is not that great. This way if you can just add speakers and PA in instead of having to rework your whole system as your grow. Traiding in is not good for th wallet ;)

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AMP. Once again I would suggest something you can grow into. (all the following are suggestions Im ton trying to tell you waht to do :) ) Get 8 ohm speakers and an amp that will deliver what you currently need at 8ohms. this way you can add subs, or monitors later if you want to. This is if the amp you find has a 4 ohm minimum. Either way I would get more watts than you currently need and leave yourself room to grow.

_________________

 

In my experiance, I ALWAYS want to run the bass drum through the PA. Unless this is listening music and not dancing/doing music. If people will be sitting down and clapping after each song ignore this part. Otherwise run the bass drum through the PA. 10's can accomplish this, I personally like running 12"tops with a horn and subs.

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I hate messing with browken music equiptment, so I tend to get more watts and more speaker than I need so I dont have to push it. Go to your local music store and ask them to set up a pa, or better... Rent one that is like what you want and see if it suits your fancy. the $100 will save you a lot in the long run.

Jonathan

 

 

 

 

 

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:) There are three things to be concerned with for equalization. Frequency (what you are trying to boost or cut), gain (the boost or the cut), and Q (the width of the boost or cut). For example, a narrow-Q at 30 Hz will boost or cut near 30 Hz, but leave the surrounding frequencies relatively unaffected. A wide-Q, in contrast, would significantly affect the surroudning frequencies.

 

In a graphic EQ, Q and Frequency are set, and you can just boost or cut.

 

A parametric EQ gives you control of all three.

 

In my experience with a mobile PA, the main purpose of EQ to to fight feedback. If you know the room well, a graphic EQ is fine. However, if you do not know the room, you can "ring the room" (meaning, search for the feedback frequencies) with a parametric EQ relatively easily by setting a narrow-Q, boosting the gain, and sweeping the frequency. When you get the nasty, painful feedback, you just cut the boosted gain to a fully cut gain and viola, feedback supressed. A graphic EQ is usable in this situation, but not ideal and will not handle fine-tuing as well.

 

Just my preference, either can be used sucessfully. However, the graphic EQ is cheap and ubiquitous, so you'll see it in most rigs, irregardless of my thoughts on the matter. :)

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Originally posted by dnkritr:

Im confused. Are you jsut buying the speakers and building the cabs? if so I would sugest jsut buysing some YAMAHA 12" cabs they will do just fine and cost you much less money.

Jonathan, check out the cabs we're talking about:

 

http://www.billfitzmaurice.com/Omni15.html

 

"On average 4dB higher in sensitivity than a reflex box, the Omni 15 uses less than half the watts to reach the same volume level. The 100dB/watt average sensitivity from 40 to 100 Hz is as good as most 15 or even 18 inch subs, so in most cases you won't need to use one with an O15. On electric bass the Omni has deeper lows than the average 2x15, stronger mids than the average 2x10, and unsurpassed highs. Keyboard players will love the low register authority. I challenge you to find a commercial speaker that delivers this kind of performance for less than a thousand dollars. You can build one for less than three hundred fifty bucks."

 

http://www.billfitzmaurice.com/Omni10.html

 

If Josh is willing to put in the time and effort to build some of these Bill Fitzmaurice cabs, he will end up with a fantastic PA that costs a fraction of a store-bought one. I wouldn't consider anything else if I needed a PA system, louder bass rig, or serious home hi-fi/cinema system (check out this sub: http://www.billfitzmaurice.com/TubaHT.html - how to bring down the roof with a few hundred watts...)

 

Alex

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At this stage I'm not going to worry about monitors, I don't think I've ever played with ones that were actually helping me at all.

 

About EQ's. Considering a mixer has EQ on it (basically, low, mid, and high) could I just not use that as a really basic feedback stopper, until I can get my hands on an Equalizer.

 

Money really is the issue here.

 

Alex - as far as money and simplicity goes - if the O15's could handle a full band, I am thinking they would be the better option, as I think there is no point making a mega rig etc etc as I would just not have the space to put it - or the space to transport it.

 

Or the know-how of how to use a top and sub etc.

 

I also think a top and a sub would be overkill - as yet all the gigs I have played have relied on the guitarists and bassist's amp's to provide their sound - were talking about 250 people. Maybe more in the future, but at the moment I think 250-350 is going to be the maximum this rig would be playing to.

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Originally posted by getz76:

Plenty of people use simple PAs. You should be fine. Add as you go.

And walk before you run. It's very easy to screw things up by incorrectly using processing gear!

 

Monitors are quite important if you want the vocals to be good. Then again, that's your singer's problem! One or two of these would be a nice solution:

 

http://www.billfitzmaurice.com/Wedgehorn.html

 

Alex

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I'm not familiar with the cabs you are looking at, and Alex is the spec guru so I won't pretend to know anything. I will however, suggest another option - powered cabs.

 

A local company uses them a lot around here. It's the Mackie SRM450/1801 combo I believe. They sound nice and have plenty of power for your average club. We use 2 of each. We also played outside and they just added a few more of each and we were good to go. Use a new board with built in effects and you're set.

 

Just another option.

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Originally posted by RicBassGuy:

I like these example diagrams from Crown as a way to better understand at least some aspects of putting together a sound system. They don't explain everything, but I like the visuals.

Thanks, that's been helpful.

 

Originally posted by TimR:

Josh, from your friends at GAK

 

http://www.guitarampkeyboard.com/en/xr-684f/3156

 

I use the peavey pro 15's but also have a PV1500 power amp with soundcraft mixer.

Thanks for the suggestion but I would rather a separate mixer and power amp - so I can upgrade as and when is good for me.

 

Originally posted by SteveC:

A local company uses them a lot around here. It's the Mackie SRM450/1801 combo I believe. They sound nice and have plenty of power for your average club. We use 2 of each. We also played outside and they just added a few more of each and we were good to go. Use a new board with built in effects and you're set.

 

Just another option.

Thanks but as money is an issue, and as they cost about £1000 each, it's not a realistic option.
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The power amp/speaker/mixer option is going to cost you around £1000. By the time you add speaker stands, mixer flight case, leads, a few mics and stands etc. What is your budget?

 

Our PA came to £1500 all in.

 

Soundcraft F16 (in sale), Peavey Pro15s (new). Peavey PV1500(new), Mixer rack case(ebay), Midiverb III (second hand). Behringer feedback destroyer/notch filter.(new)

 

And it weighs so much that one person cannot lift it safely.

Feel the groove internally within your own creativity. - fingertalkin

 

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As yet, I have no budget.

Cheap is my budget.

Bill says you can build an Omni 15 for less than $350, £190.

Everything would be second hand (except for speakers, and hardware).

I reckon I could get a 8/12 mixer for ~£75.

We're up to £355.

I think I would spend £250 max on a used power amp, and I think I'd get quite a good one for that.

So thats £605, excluding cases.

If it works out cheaper I can get an EQ. ;-)

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Won't you want 2 15's that would be £370 for the pair. Check also how much your wood is going to cost. Wood in the US grows on trees. In the UK it comes in on ships. Don't get it from B&Q or Homebase. Go to a local timber merchants. If you are lucky they will cut it up to the sizes you want. They might not even charge.

 

You'd definitely get a good second hand amp for £250. Mine was only £350 new.

 

A proper mixer flight case is going to be about £150. Don't scrimp on that. I looked for two years on ebay for the right one and in the end had to buy one new.

Feel the groove internally within your own creativity. - fingertalkin

 

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Raw speaker prices:

 

Tweeter: ASD1001 1" THROAT £17.33

Midrange: ALPHA 8MR 125 WATT £24.10

Woofer: DELTALITE II 2515 300 WATT £92.25

or KAPPALITE 3015LF 450 WATT £118.49

 

http://www.proaudioparts.co.uk/eminence.asp

 

Alex

 

P.S. Josh, have you bought that 4x10" cab yet?

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Originally posted by TimR:

A proper mixer flight case is going to be about £150. Don't scrimp on that. I looked for two years on ebay for the right one and in the end had to buy one new.

If Josh is building the Omni's he can certainly build a mixer flight case whilst he's at it!

 

Originally posted by TimR:

Go to a local timber merchants. If you are lucky they will cut it up to the sizes you want. They might not even charge.

I agree - usually if you buy the wood from them, they'll chop it up for free. Save you a bunch of time with the circular saw!

 

Alex

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Originally posted by C. Alexander Claber:

Originally posted by TimR:

A proper mixer flight case is going to be about £150. Don't scrimp on that. I looked for two years on ebay for the right one and in the end had to buy one new.

If Josh is building the Omni's he can certainly build a mixer flight case whilst he's at it!

Alex

I priced this up to do myself, and in the end I couldn't buy the raw materials for less than it would cost to buy. The one I bought was built in china and came with all the bolts for the rack and everything. If I was doing it again I would buy a separate 2 rack space case just for the power amp to make it all more manageable. If I need any more processor units I will certainly take the power amp out and put it in its own case. If my band are busy this coming year I will probably do this anyway.

Feel the groove internally within your own creativity. - fingertalkin

 

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Yep Tim I would want two - calculating went a bit wrong there.

 

I would be going to a timber merchants anyway - but thanks for the tip.

Alex - I ordered the cab, but it's not in stock till the 30th, if it does indeed come in then I should have it within a week!

 

I have been asking on the Bill Fitzmaurice forums about this ( here

) and I am undecided as to whether to build Omni 12's or 15's. 12's would be cheapest, but later on for big gigs I'd need some subs, more stuff/money. 15's would be not so cheap but I'd never need subs. I think I could use some not-top-of-the-range speakers at the start, then later on when I am more critical of the sound quality, put some better ones in. Would you agree?

 

I also realised my current bass amp (Laney 120w R2) is a kickback affair, so I could use this as a stand in monitor.

 

I'm off for a couple of days, talk when I get back.

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