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Ive been doing a good bit of research in hopes to build up an effective PA so that I can run sound for bands.

The following is what I have put together for a proper system, but of course many of you are far more knowledgable than I. So, I present you with my plan for you to analyze and critique. tell me where I'm wrong :)

Looking to be able to run sound in small to medium sized venues

(4) Yamaha BR15 Cabs
Crown XLS 802 Power Amp

(4) Yamaha BR12m Monitors
Crown XLS 602 Power Amp

(2) Yamaha SW118v Subs OR (2) JBL JRX118s Subs (opinions?)
Crown XLS 602 Power Amp

Yamaha MG166cx Mixer
dbx DriveRack PA Processor w/RTA-M Mic

Topic Tags


anonymous Wed, 11/12/2008 - 19:35

small scale? i thought my 2 br15s and xls 202 was small scale lol

1) acoustic, rock, hardcore
2) smalled to medium sized i guess (up to maybe 300 people?)
3) ive got mics!
4) about $3500 in 4 mains, 4 monitors, 2 subs and amps.

ive already got 2 br15s and the yamaha board which i plan on keeping to use

moonbaby Thu, 11/13/2008 - 02:26

BR's for hardcore??? For 300 hardcorees? Those are pretty light duty boxes, using stamped-frame woofers. Ditto for the JBL JRX crap. Those cabs don't hold up and don't like to be pumped...period. These cheaper lines from JBL, Yamaha, Peavey, etc., are not designed to be carted around and punished the way cabs tend to be treated in hardore venues.
You really need to look at boxes that have cast-frame drivers, REAL wood (NOT MDF or particleboard). Or at least those molded-plastic cabs from JBL EON or Mackie will out-perform the gear you've listed. A liitle more money spent up front will keep you from spending more in the long run...

anonymous Thu, 11/13/2008 - 03:40

I'm very good about how I treat my equipment, getting thrashed around isnt a concern of mine since I am the only one that touches it.

Ive had great success with the 2 BR15s I currently have. With this said, is it really worth spending the extra money on say Yamaha S115v Club Series V, or C115v Club Concert Series just because of them getting thrashed around?

And I'm assuming you are suggesting the Yamaha SW118 over the JBL JRX118....?

moonbaby Wed, 11/19/2008 - 02:06

Getting the sound "up in the air" can be a very big advantage, that's why S-O-S ("sound-on-a-stick" or "speaker-on-stand") are so popular. Can't do that with a 2x15 box. You can also spread the 4 boxes out to where you may need the sound, depending on the venue. In addition, if you can take each pair of the 115's and if you put them up in the air side-by-side, you can take advantage of their trapezoidal design and create a wider dispersion pattern by coupling the cabs. The bottom line is there will be more versatility in your applications, depending upon the situations you may encounter.

Boswell Tue, 11/25/2008 - 20:13

The SW118 does not have a built-in crossover, meaning that there is no output for connecting the mid/highs. You need an external crossover, and at these powers, electronic crossovers driving separate power amps are the norm.

For accurate amplitude and phase response through the crossover region, you should try to get a crossover that uses Linkwitz-Riley filters. These are even-order cascaded Butterworth filters that have 6dB of attenuation at the nominal crossover frequency (as opposed to 3dB for normal filters) and phase responses for the two outputs that align the phase through the crossover region.

anonymous Tue, 11/25/2008 - 20:37

linkwitz-riley filters, even-order cascaded butterworth filters....

this is like a foreign language to me. all i understood was butterworth, as in pancake syrup and i doubt thats what you are talking about.

i want to understand everything, but is there a quality, budget minded crossover you can suggest? or any input on the dod sr835?

and, the reason i thought the sw118 had a built in crossover is due to it saying it has "redesigned crossovers" in the description....

moonbaby Wed, 11/26/2008 - 01:54

I would skip the DOD x-over. A very good alternative would be an Ashley.
These have MUCH better headroom, a smoother filter slope, and better protection against possible driver damage. Ashleys are renowned for their filter designs, and you can usually find used ones on e-Bay ata good price. Rane also makes good x-overs.

Boswell Wed, 11/26/2008 - 02:57

stealthy wrote: linkwitz-riley filters, even-order cascaded butterworth filters....

this is like a foreign language to me. all i understood was butterworth, as in pancake syrup and i doubt thats what you are talking about.

i want to understand everything, but is there a quality, budget minded crossover you can suggest? or any input on the dod sr835?

and, the reason i thought the sw118 had a built in crossover is due to it saying it has "redesigned crossovers" in the description....

I think the description applied to the whole Club V range, of which the SW118V is a member. The full-range cabinets have internal crossovers to feed the internal bass and HF units. It's possible the subwoofer cabinets have low-pass filters, but not crossovers.

As Moonbaby says, the DOD unit will not cut it here. Take his advice on Ashley or Rane. I've got an old C-Audio crossover that works pretty well, but they are long since discontinued.

Boswell Tue, 12/02/2008 - 20:10

stealthy wrote: random question but is there any way to tie 2 power amps together.

for example, if you have 2 8ohm speakers and you cant get enough power out of one amp....can you link 2 amps together to power the 2 speakers?

Easy. Use one amp to drive one speaker and the other amp to drive the other speaker. Common the amplifier inputs. Don't even think about paralleling the amplifier outputs.

anonymous Tue, 12/02/2008 - 20:11

Boswell wrote: [quote=stealthy]random question but is there any way to tie 2 power amps together.

for example, if you have 2 8ohm speakers and you cant get enough power out of one amp....can you link 2 amps together to power the 2 speakers?

Easy. Use one amp to drive one speaker and the other amp to drive the other speaker. Common the amplifier inputs. Don't even think about paralleling the amplifier outputs.
what if the amps are of different wattage?

dvdhawk Fri, 01/02/2009 - 17:28

A: The DriveRack PA is a very cool piece of gear. The RTA mic works well and gives you a good place to start every time.

B: NEVER hook two amps to the same speaker or you will have zero amps after they both go up in smoke.

As CodeMonkey suggests one amp bridged into each speaker, is the closest you will get, until you can find the money for another amp or (two).

Boswell Mon, 01/05/2009 - 05:22

stealthy wrote: [quote=stealthy]if an amp is rated at 800w/CH @ 4ohm, and you parrallel two 8ohm speaker cabs to it, then each cabinet is going to be getting 400w right?

still not understanding if this is a true statement or not....
Invoking Ohm's law, yes, that's correct. BUT.. the problem is that the impedance rating of a loudspeaker cabinet is only nominal. An 8-Ohm nominal cabinet may actually be something like 25 Ohm around its bass resonance frequency, only 3 Ohm at the crossover between LF and HF units, and somewhere in between those values at other frequencies. If you parallel up two dissimilar cabinets, the highs and lows of impedance are going to occur at different frequencies for the two cabinets, meaning that the amplifier power is not going to be shared equally between them, leading to over-driving one cabinet or the other. So, to be safe, always parallel up identical cabinets.

Looking at it from another point of view, though, an 800W amp is reasonable to use with a 400W cabinet, and preferable to driving a 400W amp into clipping.

When parallelling up cabinets, unless you have very substantial cable, try to run separate leads back to the power amp for the two cabinets in order to reduce the power losses in the cable.

anonymous Sun, 01/11/2009 - 19:53


Ive got a few upgrades over the last couple of weeks. i had a crown xls 202d and 2 yamaha br15s for mains, i just added a crown xls 802d and 2 yamaha br12m monitors.

i plan to run the 2 monitors with the 202d in bridged mode. and i plan to run the 2 mains with the 802d in stereo mode at 8 ohms per side.

does this sound like the best way for my given situation?

also, i plan on adding a yamaha sw118 sub and crossover in the next month. once i get this, i plan on using the 202d in bridged mode for the sub, and the 802d on the monitors and mains. this should be ok for the time being, correct?

dvdhawk Mon, 01/12/2009 - 20:48

I'd just add to the thread by saying, don't get too hung up on the numbers.

A) More speakers are destroyed by under-powered amplifiers than too much power.

B) Just because your amp can run at 2 ohms, to get a higher output wattage rating, that doesn't mean it's a good trade-off. An amp running at 2 ohms, runs hotter (temperature) which increases the chance of amp failure. And, I never liked the way an amp sounds running at 2 ohms, it's more harsh and prone to distortion. When you're running the amp just 2 ohms from short-circuiting (zero ohms), something's gotta give. That energy has to go somewhere (heat).

C) Specs are too easy for amp-makers and speaker-makers to 'fudge'. Real world performance has less to do with the numbers, than the method used during the test. Stick to the top amp manufacturers, they are much more honest about their specs and provide all the details on the methods used in measuring. ( if you want my opinion on which manufacturers would be best, you'll have to ask - I don't want to start a debate unnecessarily )

But the cheap ones are just that... cheap ones that .


If you've ever been walking through ___-Mart (the mart of your choice) and seen a 4000-watt car stereo kit red flags should be going off in your mind. By my calculations, assuming the car stereo was 100% efficient - which is impossible - your car would require 333.33 amps of 12v power just to run the stereo. I'm sure someone here with more textbooks under their belt than I have will correct me if I'm wrong, but this is calculated by Amps = Watts/Volts. Does the kit include two heavy duty truck alternators and spare car battery or two? No, they're lying about the 4000 watts. It might achieve that output wattage for a millisecond, with an over-voltaged alternator, in a vaccuum, at absolute zero, running through 4/0 power cables, in a gold plated centrifuge, on the planet Krypton.

Anyway, since the same is true in high-voltage (W/V=A) if someone claims their Brand X amplifier puts out more that 2400 watts total, the same red flags should go off. ( 2400Watts/120Volts = 20Amperes ) You should start wondering how that's possible if it still has a normal AC plug on the end. Unless it has high-tech current storage built-in, 2400 total watts is the theoretical limit of that device. Or in the event it's professional tour-grade and truly puts out more than 2400w, it's probably beyond the budget of most of us, and it will definitely have a special AC cord (30A or more).

If you're dealing with a lower power amplifier, it's always interesting to find out what size fuse or breaker it has. That's a much more realistic indication of the maximum power it will consume running flat out. And it's total output will absolutely be less than that fuse/breaker rating if you do the math the other way ( AC Amperes x Volts = Watts ). We can assume no amplifier is 100% efficient, because no electrical device is, and it can't put out more than the resulting number.

A 20-amp electrical circuit cannot sustain 2400 watt RMS amp. Because really, how often do you get a true 120V? The 20-amp circuit will survive some 2400 watt spikes, but will throw the electrical breaker once it happens frequently enough for the breaker to reach a specified temperature. It's made to withstand considerably more, but only for a fraction of a second (preferably while it's still cool). It has to be able to withstand the in-rush that occurs when you switch the amplifier(s), or big motors, or whatever.

What? You have more than one amp in your rack?... If the numbers aren't at least a little misleading, I hope you brought a generator the size of a D9 bulldozer that can power a small city to power your 4-way PA, monitor amps, and stage gear plus light show. (Light bulbs on the other hand, use exactly what they say and it's constant, *unless running through dimmers.)


So you're thinking, 'what's with all the numbers and math if the numbers don't matter?'. That's the thing, real numbers matter. Manufacturers specs can be total BS, partial BS, or legit. It's up to you to sort them out. Because even the most reputable manufacturers may have to hedge their numbers so they can still compete against the ones who outright lie.

Here's a link to Crown's tech page on power recommendation. And a link to JBL's tech library that explains how overdriving under-powered amplifiers kills speakers.

anonymous Mon, 01/12/2009 - 21:25

You always seem to have a wealth of information...I read it all, most of it made sense to me. I do have one question though that I came up with while reading. As I said, I have 2 amps (Crown 202d and 802d). I have them both plugged into a Furman Power Conditioner, then the power conditioner plugged into an additional power conditioner (to help separate two racks I sit on each other).....I run the "main" power conditioner to the wall, or extension cord. Acceptable?

dvdhawk Fri, 01/16/2009 - 13:49

Hi BJ,

Sorry, it's been a couple days since I checked this thread. Your set-up, doesn't sound like a problem to me. There are distinct advantages to having your system powered by the same circuit. Keeping everything on the same phase and ground will keep potential electrical noise to a minimum. Furman makes 15-amp power conditioners and 20-amp conditioners. Hopefully the one conditioner you have connected to the wall is a 20-amp model. If you are using 2 of the 15-amp models and can't reach the wall sockets, I would pull a heavy duty extension cord with a 2-box and plug each conditioner directly into the 2-box.

SHORT ANSWER: UL may not list your present set-up and OSHA may not approve, but in the real world you should fine. If you're worried about it, find somebody with an ammeter and the necessary pigtail adaptor to tell you exactly how many amps your system is drawing when it's cranked up. You need it measured while the system is thumping near capacity. You won't get a meaningful reading if it isn't rocking at the volume you normally run things. (If you've got the top of the line Furman PM with the digital volt-meter it also has a handy-dandy ammeter built in)


According to the spec sheet, the theoretical limit of your XLS802 is 18A running at absolute peak output and the XLS 202 is listed as 10A (this one seems high to me). But at any rate, that's 28-amps. Again that's the absolute full tilt UL listed breaker rating (in other words, worst-case-scenario just prior to meltdown). To be clear the fuses and breakers are primarily intended to prevent damage and fire if the equipment experiences catastrophic failure, but it's a good indicator of what that device's maximum potential would be. With the dynamic nature of most music, your current < as in amperage > demands will fluctuate right along with the music and never pull the full 28A. And unless you have an uncommon fondness for pink noise at prolonged ear splitting volumes, and you happen to be plugged into a 30-amp circuit your amps will probably never sustain that 28A total unless they are about to shoot flames. And under normal circumstances, if you DID happen to have a transient pop or snap or boom that did hit it hard, it would probably only last a few milliseconds and be too fast of a spike to trip a modern breaker. ( however, old breakers and glass fusses can be considerably less forgiving ) A vocal mic on a stand that's tipping over will hit the floor with a lot of force and cause a hellacious thud that will light up overload lights you probably forgot you had.

For years we used to run 4 relatively high-output power amps and 2 medium-output amps from a single 20-amp power strip. These amps would have easily totaled over 60 amps - adding up fuse and breaker values of each device. We would pull a separate circuit for the 1500-watt sub amp [which had a 15-amp fuse] if we could get it, since sub is the most demanding. And even the times when we couldn't get it, I don't remember ever blowing the power strip's breaker. Although we've found some clubs with old breakers in their panel that couldn't hold up to the strain. But then again, we subscribed to the 'bigger is better' philosophy and rather than run a small system to the brink, we would bring in more cabinets and amps so we could run them all at a comfortable level. I think in the long-run this is less demanding of the venue's electric supply and it's definitely the best sounding way to fill a room. Headroom good... heat bad..... Heat kills electronic components. Lower impedances and higher output causes the equipment to run hotter. By using equipment that doesn't have to break a sweat to deliver clear powerful sound, you prolong the life of every component in the chain. You won't need to spend money re-coning or replacing speakers AND more importantly your system will sound so much better when it's more controlled. The interaction between amp and speaker is very dependent on all of these things. ( I'll let you Google slew-rate and/or damping factor as it pertains to speakers to learn more about the advantages of cone control versus worrying about the raw wattage numbers )

If you notice the lights dim with every beat of the kick drum you know you're beating the snot out of the something in the electrical system somewhere. The loads of the building may just be imbalanced at the panel. Or shoddy wiring done by some bar fly who offered to wire something up for a free drink. (The world could do without a bunch of intoxicated electricians.) If your Furman has any kind of volt-meter and you notice a big sag in voltage with every beat of the kick drum when the music gets heavy, that's also a sign. Although it's measuring the voltage, amperage demands will proportionally affect your line voltage reading while under a load. Don't forget the club has lights and coolers, and may have a deep fryer, pizza oven, and air-conditioner, whatever; making demands on their main panel too - not to mention your light show and stage gear. But you'll really know you've got an problem and you're on the brink of disaster if you start popping breakers. This is something you really want to avoid, not only does it bring your show to a screeching halt, but your power amplifiers will especially HATE it. In the simplest terms, it's like pulling the rug out from under them, and when the power is cut the sudden collapse of all that energy momentarily stored inside the amplifier is very hard on the semi-conductors and your speakers.

Also, don't go with cheap extension cords! 12/3 cable is OK for shorter runs to less demanding equipment, but in my opinion 10-gauge is the only way to go for powering your amp rack(s). You almost have to make these yourself - assuming you know how to wire a plug and receptacle. I use heavy extension cords made of 10/3 SO cable. If you don't know how make your own cables, please don't guess, get someone qualified to do it for you. Guess wrong... and the next thing you know you're welding! In any case, a simple plug-in receptacle tester is a good $6 investment. First time in a place, I test EVERY receptacle before I plug into it - [ see reference above: intoxicated bar fly electricians ] You might be surprised ( shocked if you will ) by how many receptacles I find that have the hot and neutral reversed, open grounds, or both. Beware of electricians nicknamed Sparky!

It's important to remember that you lose a little voltage per every foot of wire. The longer the cable the more you lose. The smaller the conductor size, the more severe the voltage-drop, the higher the load at the end of that wire (amperage) the more severe the voltage-drop. As your line-voltage goes down, so does the performance of your amplifiers. Again, this will cause the amps to run hotter again making them more prone to audible distortion, thermal shutdown, and total failure. It's a vicious cycle when you run everything near the breaking point. You'll turn up, the system will put a bigger burden on the electrical supply, your gear gets less juice and it loses efficiency, you turn up ... and things just get worse from there.

The same principle is true of your AC cables AND your speaker cables. Use the heaviest gauge possible and keep them as short as is practical. NOTE: SpeakOn connectors won't take 10-gauge wire without losing a few strands, but 11-gauge fits like a glove.

Anyway, that's probably more than you wanted to know, but I've been at this a long time and these are some things I've learned along the way. I'm not an electrician, but have been using, installing, and repairing audio equipment long enough to have acquired some things to pass along. I would defer to anybody with their sheepskin in electrical engineering if I've led you astray. And if there's anything you can rely on, it's that on this forum if anyone has a differing opinion they will share it.

anonymous Sat, 01/17/2009 - 14:36

Thanks Dave....Both of my power conditioners are 15a models. My "main" one (as of now), has a volt meter display on it. Also, I do run heavy duty extension cords (25ft), however they are only 12g I believe. So instead of plugging one PC into the other and running an extension cord to the wall, I should plug them both into a "splitter" (I'm assuming thats what a "2-Box" is) type deal, then into an extension cord to the wall. Thats how I interpreted it.

I will look into a receptacle tester as well. I had no idea that so much went into just the electrical side of things. You've opened up new doors for me, thanks for the abundance of great information and experience!

dvdhawk Sun, 01/18/2009 - 13:43


Splitters and triple taps are OK, but I prefer a heavy cable with an integrated 2-Box put together like this. It's one less connection to fail.

Metal cover, metal box, commercial grade 15A or 20A receptacle, watertight fitting, SO jacketed 10/3 cable.

(the watertight fitting has a nice thick rubber bushing for strain relief - the box is full of holes, so watertight isn't the reason to use this kind of fitting. If you do outdoor shows, you might consider an outdoor water resistant box and/or a GFI receptacle)

dvdhawk Tue, 01/20/2009 - 18:17

I've never seen anything like this commercially for sale. But if you build them right they'll be trouble-free for years, maybe decades. I had one finally fail a couple months ago, that I've been using for 20 years. With a 3 minute, repair - it should be good for another 20 years.

Again, if you don't know how to do this, and if you're not absolutely sure which wire goes where - please don't attempt it. Find someone knowledgeable in electricity to help you out.

The receptacle tester we talked about before is indispensable when you're doing things like this. I test receptacles even if I've wired them myself. I was recently working on a church install and a very experienced licensed, professional electrician was putting in a receptacle in the new sound booth for us. You should have seen the daggers he shot me when he saw me headed toward the receptacle he just finished with my tester in hand. There was no doubt he was insulted by the idea. I shrugged and tried to make him feel better by saying, "I check them when I wire them myself too". But that look of contempt he shot me was almost as priceless as the sheepish look he had when I gave him the bad news that he had the hot and neutral wires reversed.

I've seen every conceivable combination of mis-wiring and usually the failure is a simple inconvenience or irritating noise, and on rare occasions it results in a potentially dangerous, potentially equipment killing, shower of sparks. ( prior to my 'test-every-receptacle' pledge ) It's easy to get disoriented when you're wiring AC plugs and receptacles or soldering XLR connectors, it can happen to anyone. So I'm a big believer is having testers and meters and learning how to use them.

It's so cheap and easy to test { $6 or less }, and so potentially hazardous if done wrong, it's seems crazy not to check them.

These guys are in OH if you can't get one locally. This is a good quality tester at a very good price. They are a possible source for good quality cable too.

anonymous Tue, 01/20/2009 - 18:29

Sounds great, a friend of mine is a licensed electrician....I will try to explain to him what I need done, and show him that picture you posted. Although I'm still not sure of the advantage...where does this 2-box go in the mix of everything?

As for the tester, I will look locally to save the $8 on shipping for that $6 tester :) But atleast I know what I'm looking for now.

As always, thanks for the great great information! I know you always put alot more time into your posts than mine, but trust me, I'm a good listener when I dont know the topic and have little to nothing to say!

dvdhawk Thu, 01/22/2009 - 02:00


You're right, PSX might not be a practical place to buy that tester unless you were buying other things from them on the same order - like case building hardware for instance. ( They don't have the extrusions, but they do carry a few of Penn Elcom's feet, handles, corners, rack rails, etc. ) And actually you might have trouble finding a good AC tester like that for less than $14 locally. If you have a Home Depot nearby I see they sell the same tester for $8.

Even though you haven't been blowing any fuses or breakers, you might be limiting the amount of amperage available to your rack for headroom because the last Furman in the chain is a 15A model. Amplifiers crave good power, and I think a lot of people under-estimate the value of keeping their amplifiers well-fed. Normal music can contain powerful spikes that push the electrical demand well over the breaker rating from time to time.

Most modern commercial venues will have circuits that provide up to 20-amperes of power at 120v. (seldom is every receptacle a separate circuit) And the goal is to get the full potential of the 20-amp circuit from the wall to your amplifiers with the least amount of loss possible.

So, you could either:

A) plug a heavy cord with a 2-box like we've been talking about into the wall and plug one Furman into each of the receptacles in the 2-box
B) use two normal cords and pull each one to a different circuit. (these could even be 12 gauge)
C) use two normal cords pulling them both to the wall. (these could even be 12 gauge) (more potential power, and more potential problems possible)
D) park your amp rack within reach of the wall. so that the Furman's power cables can reach the wall socket without any extension cord.
E) make your next Furman a 20A model.

Could you do more? ... in reality, probably not much, at least not without building a 220 distro . I've said before I like using 10-gauge for powering my amp rack(s) to minimize loss. And If it's a budget issue, you might be happy with a good 12-gauge. Chances are, the romex cable that connects that receptacle in the wall to the venue's main panel probably isn't any heavier than 12-gauge anyway. So I'm sure some would argue that there's no practical reason to go any heavier than 12-gauge. But for my money, I'll keep using 10/3 SO cable and build AC cables that have their lifespan measured in decades.

uh oh.... time for science class

In this case, visualizing water flow is a good way to picture the flow of electricity, both amperage and voltage.

Imagine you're siphoning water from a pond that sits at the top of a hill using a 4-inch hose. Once you get it started the water will flow downhill at a pretty good rate and provide a steady stream of water, but the gravity-fed water will just fall out of the end of the hose - soaking the ground in very small area with a slow and steady flow.

Now image the fire-company coming and putting a pumper truck between the pond and the top end of your 4-inch hose. The hose is the same size, but now you've got enough water pressure to knock grandma over from 100 yards away. Same size hose, but a huge difference in pressure. This increase in pressure moves a lot more water, with a lot more force, and the water now has the potential to do a lot more work (or damage).

The amperage is easy to equate to the water pressure, I'd say the 4-inch measurement of the hose in this example represents the voltage (or amplitude) of the electrical wave, which is a little more abstract I know. Measuring the water's rate of flow, or water consumed, would be like measuring the wattage.
Rate of flow and pressure are different, but inter-related much like watts and amperes.

The way you've been powering your rig would be limiting the flow of the electrical current available to your amplifiers by creating a bottleneck in the flow of power, at those times your rack demanded more than 15-amps of power.

Gee Mr. Wizard, learning sure is fun!

It sure is Jimmy .... it sure is....