Building a new PA from old - HELP!!

The Bear2013

2013-02-19 11:50 am
Hello Guys,

I am looking to upgrade some old PA cabinets/enclosures with new loudspeakers and compression drivers if possible. At present I have 2 x EV Stage 200’s (full range 12” driver, 300w, 8ohm) I would use for the tops/vocals. I also have a pair of Peavey HiSys 5XT (full range 15” driver, 500w, 8ohm) for click track backing music, drum kit etc. I have a few mixers, probably either use a Behringer 12 channel or a Soundcraft folio 16 channel. For a power amp I have an American Audio 1500 (500w RMS @ 8ohms, 750w RMS @ 4ohms).

What I was going to do is run the EV’s with the American Audio power amp flat-out at 750w @ 4ohms. Then buy a Crown/Behringer etc to run the Peaveys at 1000w @ 4ohms. Could anyone recommend a good system controller for the PA?

I was looking to replace the drivers in the EV’s from the 300w to a more powerful Precision Devices PD.125SB30 - 400w or Eminence Kappa Pro 12 – 500w for added protection and headroom, as the old drivers were having issues when being driven. Would it be a simple drop-in job? I don’t want to damage the compression drivers or crossovers with the new powerful driver?

Same goes for the Peaveys – was looking at replacing the old black widows with Eminence Kappa Pro 15LF-2 (600w @ 8ohms). Again, I don’t want to blow the comp drivers or damage the crossover. I just need a more powerful, reliable PA system for my band without worrying if the cabs are being overdriven.

Any advice would be grateful?

What sort of bear are you? :D

Yes, you are overdriving your PA.

Here's why.
Consider the total power of your guitar amps on stage. Sum them. Now figure that they run at ~10% THD or more. Consider the SPL that they produce. In order for the PA to produce clean sound at the same SPL you need <1%THD (roughly speaking) or it starts to sound like total poop. That's a lot more power than what the guitar amps produce. But wait, add in the drums. Are you running your drums into the PA? In simple terms, you can't get away with this. Why? because the peak output of the drums exceeds the peak available power and SPL headroom in your PA by many dB, maybe 20dB uncompressed. You don't have 20dB OVER the average level the band plays at. Now let's talk vocals, the vocals need to be undistorted, plus they need to be heard at an average level that most bands mix above the average music level the band is playing at. Plus the average level of vocals is low compared to a guitar, especially one with any crunch or distortion.

So you've got a max SPL and max power issue with the typical small band PA that can not be overcome.

The only solutions come in using various tricks that include compression and limiting, selectively.

A bit depends on how loud you play, and exactly what is going into the mics that feed the PA. That's the other part. That and using EQ cleverly. Boost is your enemy. Headroom is your friend.

Behringer sells cheap and usable boxes that do various tricks that bands need. Used is cheaper still.

Clipping is your enemy. Never clip the PA amps. Period.

Ur best bet is probably Bi-amping.
Use high slopes on the HP for the compression drivers.
Limit the "sizzle" on the highs - it's mostly trash and hash above 10Khz in a typical band setting.

Eminence is certainly dollar wise a good value.
You should do a box simulation to see which drivers give the best results given the existing cabinets.

In a biamp situation you'd run the compression drivers directly, with a soft knee limiter before the amp to absolutely prevent the compression drivers from being over driven, and use an amp that is maybe 2x the rated power of the compression drivers. Always use a single cap in series to prevent DC destruction and accidental LF from doing damage.

The other trick is a small lightbulb in series with the compression drivers, that can act as a slow compression/protection scheme. Typically auto backup bulbs work.

Use the highest power, highest sensitivity drivers you can manage, imo.

250watt class D amp modules are dirt cheap from Parts Express, btw... they do need a power supply though. One might consider putting one of them on each speaker, for example... don't think they can be bridge though... Class D amps are sure cheap and powerful today... :D

Hope this give a few ideas...

Agree and add.
If you will replace speakers and add new power amps, it means you are only "saving" on the *empty* cabinets.
Not much logic to it, huh?
Plus you are planning to overpower every single component by at least 2X .
Not much logic either.

To better use what you already have, I'd drive the 500W 8r Peaveys with the American Audio 500W 8r per channel AA1500 (perfect match), and get another 200/250W per channel amp for the EV (also a perfect match), and add a couple good limiters between mixer and Power Amps.
As Bear (1) says, clipping is your enemy.
This way, best bang for the buck and .... a realistic goal.

You'll have *now* an excellent system for a Club situation without spending too much.

You want a larger system?
Fine, add up to this basic one (which you will then use as sidefills and monitors) and add whatever you like, but in a modular way, matching Cabinets and Power Amps.

Because if you have 5000W amps and 1000W speakers, you have a 1000W system.
A dangerous to use one, by the way.

The Bear2013

2013-02-19 11:50 am
Thanks guys!

I'm not actually using this setup at the moment. It's just a project I'm going to do. I think I'll use the AA power amp with all the said cabinets. I'm going to put 500w 8ohm drivers into the EV's and keep the Peavey's as they are. I'm going to use one side of the amp to run the EV's at 4ohm, the amp will be pushing out 750w @ 4ohm (according to the spec), and use the other side to drive the Peaveys at 4ohm. That way I think there will be enough headroom for vocals and music tracks. We don't usually mic up guitar amps or drums depending on the venue. But I will have to get a system controller for the setup. Could you advise on one for the gear I got? The driverack looks cool.
Also I need to know if I will damage the crossover/comp drivers if I choose this option?
Also I need to know if I will damage the crossover/comp drivers if I choose this option?
Probably, because you will upgrade woofers but not crossovers or drivers.
And you will end having no more than 1500W.
I suggest you set up a system like I mentioned, which needs only a relatively inexpensive 250/250 power amp, you'll still have 1500W , end everybody will be happy.
In either case, you'll need a couple *good* limiters.


2013-02-10 3:54 am
Very important to know that the original EV speakers are of very high sensitivity because of a light moving structure. So the crossover in the box is tuned to match this driver to the tweeter. An other driver with more watts will probably not be loud enough and the speaker will be missaligned.
One other thing is that if you start modifying P.A. speakers without meassuring what is happening, you end up with a random crossover region that gives you funny lobes of directivity and cancelled out angles. So moving around with a mike will be dangerous and prone to feedback out of trhe blue. Only a P.A. speaker with a smooth amplitude response will handle easy and give you maximum use of your system.
So if you can setup a somehow working meassuring setup or a friend of yours can, than i would suggest changing the 12" in the EV's for something stronger. Emmi would work, but better go for B&C or such.
I would keep the hi range driver, they are not bad. You might have to adjust HF damping or maybe use a speaker processor, with meassuring(!) can lead to a good system and has limiters.
Then don't be afraid overpowering (electricly) a modern 12" driver. They have much more peak power than a old design like the EVM 12 L or S.
They will not break so fast (my experience).
I would leave the Peavey's alone. They are optimized and will sound better if you add new speakers, x-over and a new cabinett, know what I mean?


2013-02-10 3:54 am
Your American Audio amp is much likely to put out some 400 Watts on 8 Ohms to the EV's. This is not too much as long as you don't see the red light on the amp or try to play back some HipHop sound loud.
Still swapping the EV for a decent Emminence would help. I see no need going for a PD chassis. If you re ready to spend that much, rather go for a Italian neo speaker. Will make your speakers some 6 Kilos lighter as a sideeffect. The EV 12" will break anyway as time goes by. They don't even have to be overpowered.
Processors: DBX Driverack P.A. is the minimum. I would not go for a Behringer processor. They are not very reliable and tend to having issues soundvise.
Thanks again guys.

I understand about the point of tuning of components within an enclosure. So would a direct EVM 12L/S be an obvious replacement? I thought that modern speaker builds would be more than adequate especially since the Stage 200 series was from the early ‘80s. Can you recommend a modern replacement instead of the EVM 12L/S with the correct spec for the crossover/tweeter? Or at least get close to it. PD was mentioned to be pointless, can you explain why? I’m all for reliability at the moment as I’ve had a rough time with PA gear as of late. It’s beginning to fry my brain! Ha ha.

It seems through my experience, the only thing that breaks down on the Stage 200’s is the drivers. I’ve had no problems with the tweeters or crossovers.

For basics guys, have you any information on the frequency ranges of passive/cabinet loaded crossovers I would need for a 12” full range cabinet, 15” cabinet etc?
I hope it’s not that difficult to knock together cabinets.

A guy I know of regularly buys empty cabinets from eBay and installs crossovers, drivers and tweeters into them. They sound great and punchy, if only I had the knowledge I guess….ha.
To really build good sounding speakers, IMHO, you need a flat response mike, a measuring device (scope or AC VOM or sound card computer) a sine wave frequency generator. An an-echoic chamber is used by the manufactures to test in but you can use the outdoors (if it is quiet). I had a friend that assembled drivers from the catalog in 1970, his 4 driver enclosure sounded awful. Whereas the 2 driver speakers I bought at the store sounded good. Good drivers does not equal good sound, IMHO. Every bit of foam and wood brace changes things. More and better info is on the speaker thread of this forum.
Datasheets on what drivers you buy can give you some information on where to put the crossover frequencies. You can build crossovers out of inductors and capacitors, or op amps and drivers IC's for biamp setups. I would a lot rather calculate the knee of a crossover from parts specs, than 3 driver speaker performance.
Bass only enclosures are the easiest, those 4 driver 15" rigs the main calculation is where to put the reflex port and how big. That you can copy by looking to a certain extent. Full frequency voice or even worse keyboard is a lot more difficult because of the way high frequencies bounce around and cancel-reinforce.
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Thanks again guys.

I understand about the point of tuning of components within an enclosure. So would a direct EVM 12L/S be an obvious replacement? I thought that modern speaker builds would be more than adequate especially since the Stage 200 series was from the early ‘80s. Can you recommend a modern replacement instead of the EVM 12L/S with the correct spec for the crossover/tweeter? Or at least get close to it. PD was mentioned to be pointless, can you explain why? I’m all for reliability at the moment as I’ve had a rough time with PA gear as of late. It’s beginning to fry my brain! Ha ha.

It seems through my experience, the only thing that breaks down on the Stage 200’s is the drivers. I’ve had no problems with the tweeters or crossovers.

For basics guys, have you any information on the frequency ranges of passive/cabinet loaded crossovers I would need for a 12” full range cabinet, 15” cabinet etc?
I hope it’s not that difficult to knock together cabinets.

A guy I know of regularly buys empty cabinets from eBay and installs crossovers, drivers and tweeters into them. They sound great and punchy, if only I had the knowledge I guess….ha.

Not knowing anything about the specifics of your existing cabinets, it is impossible to even guess at what would be reasonable as a driver replacement. So, first step is to spec the cabinet dimensions, the internal volume and what the cabinet is NOW set up as (sealed, ported, other...) and how it is tuned in the case of a ported cabinet.

Next determine the T/S params for the existing EV.

Next determine the xover frequency for the tweeters (whatever they are, that would be useful to know too)

Now you are just about ready to figure out what you need or want to do.

That assumes a direct replacement with no changes.

IF you want to buy or build cabinets, then you have a wide open field and the choices are quite wide and varied. An advantage is that you can definitely build a very high performance system DIY. But you need to either follow existing plans correctly OR you need to be able to make your own design choices (don't think ur up to that just yet)

The PD is hyper overpriced (assuming it's the driver company I am thinking of...) - for that much money ur better off buying more of something else, or adding more speakers/cabinets, or buying an existing PA cabinet rather spending $$ on a premium priced driver.

The "knowledge" is pretty simple on one level:

download some freeware bass/enclosure speaker simulation software, plug in the T/S params of your existing speaker into the appropriately entered box volume and (presuming here) port dimensions and see how it looks in the bass end. Compare to the specs of other available woofers. This will tell you how it will come out *approximately* on the bass end.

next is the rest of the response - that can be seen to some extent by the mfrs published curves, if there are any. The driver needs to cover to the xover point and beyond a bit (in most cases) and not have objectionable deviations (peaks and valleys)

You need to consider impedance, that effects xover frequency and slope, as well as amplifier load.

You need the most sensitivity you can find, and the most power handling, that's a balance: power vs. SPL vs. xmax/excursion.

It's all a big compromise. Finding the best compromise is the game.

Worst case you build/modify something, and it sucks, so you sell the parts and go at it again with the knowledge you gained, not much loss $$ wise.

There is lots of information in the forum here on just this sort of thing, ur not the first to want to do this. So, read up. There are really almost endless possibilities and variations to consider and try.

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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.

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?
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.

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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.
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).
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.