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Building a new PA from old - HELP!!
Building a new PA from old - HELP!!
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Old 5th March 2013, 06:15 PM   #11
chris661 is offline chris661  United Kingdom
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Exactly what is needed of this PA?

You said guitars and drums don't go through it.
I would recommend that the guitars do: relying on the backline for anything other than club jazz is asking for trouble with feedback.
If you have a bassist with a big enough rig, that doesn't need to go through the PA. I'd say 300w and 4x10" would be a minimum.
Vocals definitely do need the PA, and maybe the kick-drum (depending on venue size - just for a little re-inforcement).

I'd say don't bother looking to go much below 80Hz, and in fact add a low-cut filter there to ensure the drivers don't bottom out. You'll also get a cleaner sound as you'll avoid hitting most of the room nodes/standing waves.

Here's what I'd do in your situation...

Invest in 4x Eminence Beta (or Delta) 12 drivers, and two decent compression drivers from Eminence.

Build a pair of cabinets with one woofer and one tweeter. Add a +6dB switch to the tweeter L-pad.
Build another pair of cabinets with just a woofer per side.
Give those cabinets each a copy of the low-pass crossover from the two-way cabinets you built earlier.
You could get clever and have those second boxes on the floor and cross over ~150Hz for more oomph in the bass - big series inductor (or active XOs) needed for that.

Now, you have a modular system.
You'd use the 2-ways for most stuff - it'll be loud enough.
Put the extra woofers on top for an MTM system - you'll get 6dB more output (assuming your amp can stick full power through 4ohm per side) and the midrange ought to project better.
Put the extra woofers on the floor, run them as subwoofers, and you've a decent full-range system with plenty of kick.

Over time, maybe look at 15 or 18" subwoofers if you end up mic'ing the whole drum kit, or are playing at larger venues.

I'd say 12" drivers are about the sweet spot for midbass duties: 15"ers can't do midrange to a couple of kHz, 10"ers can't move enough air to do a kick-drum properly.

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Old 6th March 2013, 09:27 AM   #12
The Bear2013 is offline The Bear2013  United Kingdom
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I’ve just obtained a Peavey XR 1220 powered mixer. So I will be primarily using that in the future. It states on the back that it is 600w per channel and it has 2 channels with 2 speakon outputs per channel. So there’s 4 outputs all together. I am assuming that if it’s 600w a side with 2 outputs per side then each of the 4 outputs is 300w. So what I was thinking of doing was this:

Channel 1 = 2 speakon outputs – each output will go to a EV Stage 200 (300w cab) That’s 600w taken on the one side
Channel 2 = 2 speakon outputs – each output will go to a Peavey XT (500w cab), although the power amp may not match the cab capability, it should be plenty.

This power mixer also has an auto-EQ function and you can use RTA with a mic.
It also has a built-in crossover or a Subwoofer Output so I was thinking of using the American Audio amp with a 2 x 15” sub enclosure (1000-2000w), maybe I could bridge the amp and that’ll take care of the sub cab.

So all in all, the PA would be EQ’d via the RTA/auto-EQ function. All the correct frequencies should go where they are supposed to without the need of an external crossover or system controller like the Driverack as all this is built-in to the power mixer.

So I could send or pan the vocals to the EV’s (Channel 1), pan the music/backing to the Peaveys (Channel 2) + external powered sub, then mic the bass drum (pan to subs), then mic the guitar amp (no panning) so it’ll get a full spread.

Sorry for the newbie quotes but I hope to gain knowledge through my tinkering! Is there anything you would do differently? Maybe use another power amp not to push the power mixer too much?
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Old 6th March 2013, 10:32 AM   #13
The Bear2013 is offline The Bear2013  United Kingdom
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Hi Guys,

I've added a photo to provide a more visual accurate representation of what I am looking to achieve:

Click the image to open in full size.
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Old 6th March 2013, 02:10 PM   #14
bear is offline bear
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Building a new PA from old - HELP!!
Dear The Bear2013,

I think for you to get good answers and results you'll need to define your situation and goals much more clearly.

- what sort of music?
- what sort of average SPL in the middle of the room?
- what is the actual size of the typical room you play in?
- are you an amateur garage band, no pay, sometimes gigging amateur band, or semi-pro band (paid for every gig)??

Your Peavy mixer ain't gonna cut it. Not unless ur in a very small room, maybe a practice room.

If you look at the specs on the Peavey you'll see that is likely the max rating into 4 ohms. That makes it a 150 watt 8 ohm x 2 amplifier.

I am going to totally disagree with the previous poster - putting the guitars and/OR the kick drum (or any drums) into your PA means instant overload and/or clipping. I'd sooner run more guitar amps on the stage over running them into the PA. As far as amplifying drums in the typical small band's PA = SONIC DEATH.

The truth is that the drummer should carry his own "PA" stack, his own mixer with limiter(s), and his own amps. This won't be too popular with drummers, I expect. But if ur band is playing so loud that you can't hear a good set of acoustic drums, you should either turn down, or have enough gear to handle the requirements to reproduce that sound.

Making the assumption that ur playing something like grunge or metal or something sonically akin to that, you're going to want the most amp power your speakers can handle, and once again a LIMITER on the output of your mixboard between the mix signal and the power amp. It can go in a loop on that PEAVEY, need be.

A whole lot comes down to the total $$ you can put into your project, either at once or over a number of months.

Anything less than what is actually needed to do the job ends up being hash and distortion as output.

I think I suggested already that you might consider a Class D amp module for each speaker/driver for maximum effectiveness and best matching/level setting.

I do not think the concept stated earlier is clear:

The effective loudness of a 100 watt guitar amplifier is many times that of an undistorted amp + speaker (PA system).

Put this the other way around - the PA system needs to be far more powerful and capable of more SPL (loudness) than a 100watt guitar amplifier, IF the PA is going to be able to sound as loud as the guitar amp (when amplifying voices, for example).

And actually, the PA needs to be more capable than the SUM of all guitar amps + drums to do the job.

Once you put the drums and the guitars into the PA, the requirements for the PA go even HIGHER. Why? Because vocals need to be low in distortion in order to be heard properly, guitars don't. Drums have exceptionally high peak output so will cause clipping IF they are set at equal level in a PA system that is already being run within 10dB of its maximum power output. (this 10dB figure is likely not enough).

This means in practice that if you have a "1,000 watt PA" you would have to run that at a maximum average level of <100watts, and likely more like ~30watts (that's just 15dB down) in order to NOT clip drums.

[working the other way, assuming TRUE 100db/1w speakers, then 30watts of input produces ~15dB more output, or 115dB @1m!]

The alternative is to put the drums in a sub mix and put a limiter on that output so that the PEAKS are controlled within a few dB, and the PA is NOT sent into perpetual peak clipping. Of course that sounds mostly like carp, if you do that... one needs a more sophisticated combination of limiters to handle drums and make for a live mix that isn't overly squashed and/or "pumped" by one drum or the other (like the kick drum for example).

Bottom line - if you care about vocals, keep the rest of the stuff out of the PA that does the vocals, unless you build/buy a PA that really can do the job properly.

If you think your music has merit, then don't do what all the other small bands do to their sound by trying to fit an elephant through a small door - the result is sound that is harsh, awful and ear splitting. It can't work, doesn't work, won't work, and has never ever worked.

If you want to hear how awful this can sound, take a digital recording of your band's playing *direct* out of your mixer, and then play it back on a small boombox CD player with the volume turned to max - clipped. o_O
That's what the audience is pretty much hearing from most bands in most small clubs - hashed up, clipped/blown speakers and amps.

http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]

Last edited by bear; 6th March 2013 at 02:16 PM.
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Old 7th March 2013, 09:45 AM   #15
The Bear2013 is offline The Bear2013  United Kingdom
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The music we play is generalised. We are a cover band doing mostly modern pop songs. We are semi-pro and get paid for every gig we do. Our fee range from $450/300 to $1500/1200 depending on the booking/gig. So we are bordering on pro if the bigger bookings become more regular.
The average size/capacity of a room will be anything between 100-500 people. As we do public gigs in bars and pubs which house 100-200 people. But we do have some private bookings soon such as weddings, birthdays, corporate parties etc. So really I need to get this all sorted ASAP.

For example, some bands that are similar to us have PA systems such as RCF 7 Active Series – 710 tops and 905 subs – so that’s a 3.5kw rig. Another band has a Void Basys 2 system.

So I need to be to that level of PA to compete. I’ve always preferred passive systems to active, I feel they have a better presence and more punch.

So what I need to be looking at is 1000w for the tops/mids and 1000w for the sub for each side – so it’ll be a 4kw rig?
So I should get rid of the Peavey powered mixer, maybe part-ex for a few power amps to handle the power and a new mixer with modern functions such as the Auto-EQ/RTA.

The money is the issue. Clearly. Otherwise I would go out and buy a $4000 active rig and be done with it.
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Old 7th March 2013, 05:13 PM   #16
JMFahey is offline JMFahey  Argentina
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Keep the Peavey powered mixer, anyway you won't get much for it and it's valuable: absolutely last ditch emergency backup (sh*t happens)/drum submixer/rehearsals/some weddings where old people ask you to please turn volume down, etc.
I would never gig without a backup and most critical of all is the PA system, all others can (worst case) plug straight in the mixer, even the Guitar Player (thanks to a Pod or something).
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Old 8th March 2013, 04:05 PM   #17
chris661 is offline chris661  United Kingdom
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Bear, the sort of system I last used was 4x 15" 2-way tops, on top of 4x 15" subs. Active crossovers between subs and tops, lots of power from a couple of big Peavey amps.

The gig was in a big church hall. Couple of guitar amps, big stage drum kit, decent bass rig, etc etc.
The kick drum, vocals and guitars went through the PA.

The guitar amps were not loud enough on their own to play clearly to the whole audience. They're point sources on-stage, so can't hope to reach the far corner of the room: the other guitar amp will be heard more. So we DI'd both into the PA, and used the guitar amps as monitors, just as they ought to be.
The bass amp can do without the PA, as LF carries better, so we just used the PA for a bit of mid-high fill if needed.

Vocals and drum had independent limiters, and the guitars didn't need it (the bass amp had its own compressor, so a second one wasn't required).

I've also met some guys in a band that used to have a rig similar to the above, and have replaced the lot with a pair of QSC active speakers. The ones that'll do ~130dB per side. Apparently it's much easier to transport and set up, and actually sounds better.

Might be worth seeing if the OP can audition those.

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