Are 24 x T60-LAB15s Enough? ;)

[Levi]

There might be some errors in your thinking about 3 phase. I don't think it's as easy as just a 208v sine wave.

The way you get 208v using 120v per phase is by taking the difference between 2 different of the 3 sine waves that are 120v each. In theory, I guess I could change the genny's alternator to a high wye 240v per phase, and dial the voltage meter all the way down, but I'm not sure that dial would make the voltage per phase go from 240v all the way down to 208v. I think it can only do plus or minus 10% or something. I know we crank up the voltage in the low wye 120v to 130v to help with any voltage drop in our main distribution lines, which are about 100' each to the spider boxes.



Oh, and don't worry, we make our own banded cables! We get higher ampacity using THHN instead of SJOOW jacketing for our main runs. THHN is not nearly as flexible, but it is much lighter and can withstand much higher temperatures, hence the higher ampacity. And it's less expensive.




There are a couple things I'm not sure about the 3 phase 208v option...




The first and most practical question is about what the amp can actually handle as its power supply. 3 phase in our grid will have 3 hots, 1 neutral, and a ground. 5 wires altogether. I've tried to see how many terminals are inside the 410 in the pictures, but it's tough to tell.

If there's just one spot for a hot, then all it can take probably is single phase. And the only way it can get 240v is if that single phase goes to 240v.

If there are 2 spots for a hot, that gives more options. It would still do single phase 240v. And I'm guessing it could do split phase 240v if each phase goes to 120v.

I'm going to assume it definitely does not have 3 spots for a hot. that would just be way too easy convenient. So, there is basically a 100% chance of that not being the case.




The second question is how "smart" this amp is. With 3 phase in our grid, we can only use the low wye (120v per phase) setting on the genny's alternator. The high wye goes to 240v per phase, but since we are in the US, all the rest of our stuff runs on 120v and probably couldn't handle that higher voltage. So that's probably a non-starter.

So, with the low wye, again the only way we get 208v is by taking the difference between two of the three phases at any point in which they have that difference to offer. As long as the 410 is smart enough to recognize when 208v occurs, and pull 208v between 2 phases instead of just taking 120v from either one of the phases, then great!

Maybe I'm overthinking this, but it seems like the timing would be key.

If we just have single phase 120v, it can grab the full 120v twice per cycle, at +120v and -120v. Let's say those occur at 90 and 270 degrees.

If we have split phase, then it can grab the full 240v twice per cycle as well, when the two 120v phases are as far away from each other as possible. Again, at 90 and 270 degrees.

If we have 2 legs of three phase, then it's much more complicated. The 208v occurs continuously between the phases in a few places. There is a precise answer, but by just eyeballing it, I'd guess that happens in 2 sets of continuous chunks. The chunk's starting and stopping place just depends on which 2 of the 3 phases are included. If we look at the blue and green phases, then maybe the first chunk starts at 0 and goes to 90 degrees. Then the second chunk maybe starts at 180 degrees and goes to 270 degrees. So maybe 208v is available half the time, not at just two points in the cycle like single and split phase. But, since with green and blue it looks like 208v would be available at the same 90 and 270 degree points as single and split phase, it should work if the amp knows to pull at those points. However, that might not be the case if instead the phases were green and red, or red and blue. At 90 and 270 degrees, both of those options might not have 208v to offer.

Hmmm... this is a tough one...

[Bruce Weldy]

Geez....you guys are getting out in the weeds.....

Less talk, more sawdust.

[Levi]

Hahaha!!! Don't worry, Bruce! The weekends are all sawdust!

[Seth]

There might be some errors in your thinking about 3 phase. I don't think it's as easy as just a 208v sine wave.

Perhaps. I don't love being wrong, but I love learning. The two just seem to go hand in hand more often than not for me. LOL

So, with the low wye, again the only way we get 208v is by taking the difference between two of the three phases at any point in which they have that difference to offer. As long as the 410 is smart enough to recognize when 208v occurs, and pull 208v between 2 phases instead of just taking 120v from either one of the phases, then great!

The way I understand it is, while 208v between two of three legs is comprised of two independent 120V sinewaves that are 120º out of phase, they combine to create a single phase 208V sinewave. Where if they were identically in phase they would combine to create 240V Single Phase, or 180º out of phase to create 240V Split Phase.

Being as there's 3 120V Phases out of the genny, there are also three possible 208V single phase circuits

In regards to how to wire the amplifier, one leg from the genny to neutral on the amp, another leg from the genny to hot on the amp. Neutral from the genny wouldn't be used for 208V circuits, only 120V circuits. So you could run 5 wires into the amp rack and essentially have 3 circuits of single phase 120V and 3 circuits of single phase 208V. Only loads like electric motors that are designed to run on 3 phase take a lead from all 3 phases and are technically 3 phase loads. Loads that only take leads from two of the three phases are technically single phase loads.

At least that's the way I think it is, based on a little reading.

[Seth]

Had a little chat with Herson at VIP Pro Audio this morning.

[Seth]

Geez....you guys are getting out in the weeds.....

Less talk, more sawdust.

LOL. Get the weed whacker out!

Bruce, do you have anything to add in regards to Class AB vs Class D amplifiers? How do you like the amps you use now? Do you feel like they could be better in some way? Any sound quality issues?

[Seth]

...180º out of phase to create 240V Split Phase.

Not super relevant to the power solution needed in this thread, but thought I'd correct myself here anyway. Split phase electricity in North American homes is actually not 180º out of phase when wired for 240V. The 240V secondary coil in the service transformer, being tapped and referenced to ground in the middle creates two 120V circuits that are technically in phase with each other. But since the center tap is Neutral, when viewing the waveforms on an oscilloscope one circuit is viewed from north to south and the other is viewed from south to north. But really, when the two hots are used to get 240V, it just completes the original full length of secondary windings in the transformer, no opposing waveforms 180º out of phase to each other. Just straight single phase 240V.

[Levi]

Yes, I agree! The two 120v waves that are 120 degrees apart create 208v. But just like the other options, only at certain times.

Here's how I see it:

If you plot the voltage difference between green and blue, I guess it is still a sine wave, but it is a very modified one. It starts at zero, then quickly gets up to 208v, then stays at 208v for 90 degrees or so, then quickly back to zero. Never goes negative. Or maybe it does go negative. Either way, though, instead of a lot of regular parabola shapes, you instead get a series of flat top humps.

If they were identical in phase, I think the voltage stays the same. It wouldn't combine to get 240v. You'd just get double the amperage versus a single 120v phase. But you only get 120v if you go line to neutral. If you tried to go line to line, you'd get nothing because there is no voltage difference. If you are looking at that big black sine wave in the picture above, it is just a plot of the difference between the red and black phases, and represents split phase, not a doubling up of synced up single phases. That's what the note under the chart says anyway. Or, if we were in the UK, it could be a monster single phase, and maybe other commonwealth countries. I think that's how their grids work.

And yes, if they are 180 degrees offset, then you can get 240v at the points where one phase is at +120v and the other at -120v.




I agree - you can get 208v three separate ways, by taking the difference between each combination of phases.




I didn't think of wiring two hots, and leaving out the neutral! Interesting! And I completely agree on the rest of that thought.

I just wonder, would anything crazy happen if two hots are wired that way?

One thought I had is a potential crossover event. I can't picture exactly how that would happen in this case, but anytime two different phases cross paths, it can be risky business.

Also, without a neutral, how would the circuit complete? How would it induce electrons to flow? Is the difference in voltage between the lines enough to do it?

Or maybe we would use the ground and have the circuit complete through the big ole copper rod we ground the genny with? No, because then there would create an open circuit and so much amperage would rush that the breaker would flip. I think.

If we use split phase as a comparison, then there are two hots, a neutral, and ground. I'm not sure how the actual electrical components in the power supply handle that, but they definitely pull 240v between the hots, and the electricity flows because it has a path back via the neutral, which is also connected.

I would guess the 208v phase would work exactly the same. 2 hots, a neutral, and ground. It's just that the 120 degree offset would mean that 208v would likely occur at different times than it would with the split phase wiring. The big question in my mind then is, would the amp be able to handle that? Would it figure it out? It is definitely not the same rhythm of electrical flow. I just don't know enough to know. My only other thought is that testing would be crucial, of course. Even though I said it, it goes without saying. And hopefully there's a no questions asked return policy on the amp, just in case.

Did you say you have an Admark amp? Is there any way to check its power terminals?





Thanks for looking into the availability! After all this, though, my big question for Herson would be is he absolutely sure that taking two legs of a 3 phase circuit, wired as any two of the hots + neutral + ground, would work? Or maybe he knows another solution?




That said, if we relate this back to the subs for a bit, given the limiter's effect on the T60s, would 208v even be needed?

I get that the amp could use that higher voltage to keep amperage flow down in certain parts of its guts, and thus reduce heat and improve efficiency. But eventually it has to step that 208v, or 240v, or 120v, down to 45v, and increase amperage. It doesn't seem like a big difference, but maybe that's what made the big difference in Elliot's testing and formed his opinion.

"If you live in the States, don't even waste your money if you cannot feed the K30/K35 a minimum of 208 Single Phase. Ideally, 240 volts would be best. Bear in mind, all the test I've conducted were based on 250 volts. If the voltage is less you can expect more amperage will be consumed than what I mentioned on the first page."

My guess is that he really wanted to put this amp through the gauntlet. I know I would with new unproven equipment.

I went back to his test results, and looked at the continuous sine wave section. I'll use the nearest round numbers. He had about 3400w at 4 ohms. That would mean about 116v and 29 amps, correct? So if he's cranking it up that high for the test, it definitely seems like he'd need the 240v.

But we would be nowhere near those levels for this system, correct? So even if one of these 410s fails, and we have to transfer its subs to the other amps, wouldn't the heavier load be just fine? (To a certain point?)

The limiter is set to 45v. So even if there are transients that want more than 45v, they won't get it, correct? The max a single sub would get in bursts would be 45v * 5.625a = 253.125w, correct?

Dave Rat says that drivers only actually use 10-20% of their "continuous" rating as a true continuous RMS power draw. So in the case of the LAB12s, which are rated at 400w, that would mean they actually draw 40-80w, but then momentarily use 10x or so of that for transients with compressed music.

If that's the case, then the LAB12s, limited to 45v, would use say 80w each continuously, and then peak up to 253.125w, correct?

So then if we really need to, we'd have no problem running the 410 in 2 ohms (4 cabs) per channel, times 4 channels, for 16 cabs altogether on a single amp? Its spec sheet says 2890w max power per channel in 2 ohm. 4 cabs x 253.125w = 1,012.5w per channel, which is still way way under the 2890w rating. So even at this level, maybe we'd never need more than 120v anyway? It seems like it would still be running with plenty of headroom. And if we look at it from Dave Rat's continuous RMS standpoint, then 16 cabs x 80w = 1,280w, which is way under what a 20 amp circuit can handle at 120v.

That math seems too good to be true though... Is it?

Also, does this 2890w max power rating refer to continuous or burst?

Also, do you think they are referring max power at 1kHz? If yes, driving the amp at frequencies below 60 Hz would drop that max rating by maybe 30% or more then? Even if it was 50% drop, though, it would still be fine, yes? It would just create a little more heat. But that would still be a lot less heat than a Macrotech?

[Levi]

Interesting point on the tapped 240v!

From a power transmission standpoint, that makes a lot of sense. running a single 240v phase means big savings in conductor material. Fewer AND smaller wires to run all over the country.

Thanks for pointing that out!

[Bruce Weldy]

Bruce, do you have anything to add in regards to Class AB vs Class D amplifiers? How do you like the amps you use now? Do you feel like they could be better in some way? Any sound quality issues?

I like the Crowns that I use. Lightweight, cheap, and get the job done with some headroom.

Everything is relative.

Who is the audience? How big is the audience? Any volume limitations? What's the budget?

These are all factors that have to be balanced. There's give and take on every piece.

But, what's more important than which amp or processor you choose is whether or not you know how to properly set up the system, Balance the system, and EQ the system. Having multiple Driveracks is NOT going to make it any easier or any better. It will be much more complicated and for the most part, redundant. The only reason for using a driverack with more outputs would be if you have delay towers or frontfill/outfill.....and if you are running a tight setup, there's really no need for front fill. And if you do need it, just run a matrix out from the X32 to a separate amp for the OT12s as center fills. Much easier to control and set up.

Use the driverack to balance and get the EQ close. Since you are running through an X32, you have full range EQ (6 band parametric) to further shape what you want on the main outputs, not to mention the input channels with 4 band parametric.

Power shading? You don't need more driveracks for that.....just turn down the knob on the amp that is running the bottom speakers. Voila! Power shading.

Too often I see venues and engineers try to make the sound the same volume for everyone in the audience, but you have to remember that the public will position themselves where they enjoy the music the most - the headbangers down front getting blasted, those wanting a little rest for their ears will move farther away - don't take that option away from them... get it loud up front and let nature and physics take care of the back of the crowd.

I made this suggestion to Victor the other day on the phone, but I'll pass it along here also. While you are rightly concerned about the amps overheating - you haven't addressed the actual driver in the subs. While we don't hardly ever worry about thermal limitations, because excursion is most likely to be what's going to destroy your speakers....in the case of having those drivers moving back and forth 24/7 in 100+ degree heat - it can be a real issue (especially with music that has a kick drum on every beat and constant bass).

My suggestion is to do a scheduled shut down every 30 minutes of one amp. Then turn it back on and shut down another one. With 8 amps, every amp and its drivers will rest for 30 minutes every four hours. Yeah, it knocks out 4 subs - but hey, you've got 32 of 'em. Probably not as important at night, but letting both the amps and the drivers cool down might be what saves you from some real problems.

When making decisions on the gear and setup, try to keep in mind the old saying, "Just because you can, doesn't mean you should." You're building a pretty big system, but still not in the league of the really big boys. It will be impressive, but first and foremost - make it sound good. And usually the best way to do that is to focus on the basics. Fancy hubcaps won't make your car run any faster.

Anyway, that's the suggestions from the old curmudgeon.

[Seth]

I didn't think of wiring two hots, and leaving out the neutral! Interesting! And I completely agree on the rest of that thought.

I just wonder, would anything crazy happen if two hots are wired that way?

One thought I had is a potential crossover event. I can't picture exactly how that would happen in this case, but anytime two different phases cross paths, it can be risky business.

It's how any single phase 208V appliance would be wired to 3 Phase service, so nothing crazy.

Also, without a neutral, how would the circuit complete? How would it induce electrons to flow? Is the difference in voltage between the lines enough to do it?

When wiring across two of three hot legs of 120V each, the neutral isn't used. Instead, the two hot leads completes the circuit for each other. Each leg is rooted at the same point the neutral would connect to. As far as the how and why, I'm still in the process of wrapping my head around it all. I'm really enjoying the mental exercise! If I have any brilliant epiphanies, I'll be sure to share with the class. But, you can color me a lite shade of confused at the moment. I'm confident THAT it works as I'm saying, I'm just not super clear on the how and why it works the way it does.

...I would guess the 208v phase would work exactly the same. 2 hots, a neutral, and ground.

Just two hots and a ground. No neutral for 208 single phase.

It's just that the 120 degree offset would mean that 208v would likely occur at different times than it would with the split phase wiring. The big question in my mind then is, would the amp be able to handle that?

I know the two legs are 120º apart and it seems like they would create a double hump up and double hump down type of waveform instead of a sinewave. But, I'm 95% sure they actually couple and result in a pure sine wave. In which case the amp would just see the same 60Hz sinewave it would at 120V, but at 208V instead. There are a bunch of things that run on single phase 208V derived from 3 phase service. Air conditioners, motors, water heaters, commercial refrigerators, ice makers, etc. can all be specified to run on 208V, single phase. Which is any two of the three available hots and a ground, unless there is something in the appliance that also requires 120V, in which case there would be a connection for a neutral too.

From the following link "Suppose you have two sinusoidal functions with the same frequency ω but with different phases and different amplitudes... ...Then their sum is another sine wave with the same frequency"
https://www.johndcook.com/blog/2020/08/ ... ine-waves/

Thanks for looking into the availability! After all this, though, my big question for Herson would be is he absolutely sure that taking two legs of a 3 phase circuit, wired as any two of the hots + neutral + ground, would work? Or maybe he knows another solution?

You're welcome. I didn't pose that question to him, since I'm personally completely confident it will work as intended with two hots and a ground. Ground being only ground, not carrying any electricity.

That said, if we relate this back to the subs for a bit, given the limiter's effect on the T60s, would 208v even be needed?

I get that the amp could use that higher voltage to keep amperage flow down in certain parts of its guts, and thus reduce heat and improve efficiency.

But eventually it has to step that 208v, or 240v, or 120v, down to 45v, and increase amperage. It doesn't seem like a big difference, but maybe that's what made the big difference in Elliot's testing and formed his opinion.

It's not about the amp or amp efficiency, it's about minimizing amperage draw on the power grid, the required wire gauge to support it with minimal voltage sag, and distributing the load across all of the generators outputs. Apparently, the Power Factor Correction power source in the Admarks can draw dashes of large current, "120-volt Line Source: 157.8 amperes (Both Channels Driven) Estimate" (quoted from that test link you posted). Other amplifiers I've had in the past (Behringer iNuke's) that had those high amperage draw peaks usually occurred for short blips of just a few milliseconds and were able to slip through no problem without tripping the breaker. But, I'd still rather have that load on 208V instead of 120V if the option was available.

Even just calculating it out without thermal losses, you're going to have 32 x 250 watts, 6000W just in subs. That's 50A at 120V or 30A at 208V. Split into 3 separate circuits 10A each at 208V, 17A each at 120V... and that assumes the amplifiers are 100% efficient, which they're obviously not. Which is just simplified to make the point, there's obviously no way to divvy up 4 or 8 amplifiers equally onto 3 separate circuits.

"If you live in the States, don't even waste your money if you cannot feed the K30/K35 a minimum of 208 Single Phase. Ideally, 240 volts would be best. Bear in mind, all the test I've conducted were based on 250 volts. If the voltage is less you can expect more amperage will be consumed than what I mentioned on the first page."

Small note here, that he mentioned running it on minimum 208V... It can't take 208 3 Phase, but this is yet another indicator that 208V single phase will work just fine.

I went back to his test results, and looked at the continuous sine wave section. I'll use the nearest round numbers. He had about 3400w at 4 ohms. That would mean about 116v and 29 amps, correct? So if he's cranking it up that high for the test, it definitely seems like he'd need the 240v.

Your figures are correct, 3400W @ 4Ω is 116V @ 29A. To estimate the amplifier draw without knowing the specific efficiency of the unit, I just use 80% as a figure to work with for Class D amplifiers. In actuality it could be better or worse. Anyway, 3400W ÷ 80% = 4250W the amplifier would potentially consume on average with a sinewave. Could be a little more, could be a little less.

But we would be nowhere near those levels for this system, correct? So even if one of these 410s fails, and we have to transfer its subs to the other amps, wouldn't the heavier load be just fine? (To a certain point?)

As a complete system, your system will have the potential to draw more than twice the numbers he's quoting for the one amplifier. Assuming the subs and tops all have a maximum of 250W each, your system could potentially draw... 7500 ÷ 80%, 9375W. 78A at 120V, 45A at 208V.

The limiter is set to 45v. So even if there are transients that want more than 45v, they won't get it, correct? The max a single sub would get in bursts would be 45v * 5.625a = 253.125w, correct?

Correct. Even if someone mashed the volume into the red, still limited to 45V/250W.

Dave Rat says that drivers only actually use 10-20% of their "continuous" rating as a true continuous RMS power draw. So in the case of the LAB12s, which are rated at 400w, that would mean they actually draw 40-80w, but then momentarily use 10x or so of that for transients with compressed music.

If that's the case, then the LAB12s, limited to 45v, would use say 80w each continuously, and then peak up to 253.125w, correct?

What it draw's on a continuous average really depends on the material it's playing and what the T60's impedance is at whatever the specific frequencies are. Something like live rock music, bass guitar and kick drum would use less average voltage than highly compressed Pop/Hip Hop/Rap music and both of those scenarios would likely use less average power than some of the sustained low notes common in EDM. I used "voltage" and "power" in that sentence to highlight that the same voltage could result in more or less power depending on the impedance at whatever the differing frequencies are. However, your point is very valid, a continuous test sinewave (or music that has nearly continuous sinewaves) will draw more power than a typical music source. I suspect this is why amplifiers are rated to draw from wall power 1/8 their rated output power figure. Based on Corona Operator's 800W peak measurement of his two 2x12 T60's, six DR250's, and other related electronics while playing heavy EDM, I'd venture a guess that you might see peaks around 3kW/25A if you ran 120V. Although, it's not impossible for the peak draw to be considerably more than that.

So then if we really need to, we'd have no problem running the 410 in 2 ohms (4 cabs) per channel, times 4 channels, for 16 cabs altogether on a single amp? Its spec sheet says 2890w max power per channel in 2 ohm. 4 cabs x 253.125w = 1,012.5w per channel, which is still way way under the 2890w rating. So even at this level, maybe we'd never need more than 120v anyway? It seems like it would still be running with plenty of headroom. And if we look at it from Dave Rat's continuous RMS standpoint, then 16 cabs x 80w = 1,280w, which is way under what a 20 amp circuit can handle at 120v.

If you were setting this up in a club and were, for whatever reason, limited to one 20A 120V circuit and adding a (or 3) 208V circuit would cost you a bunch of money, I'd say give it a go and see what happens. I'd get a kick out of seeing if a 20A 120V circuit would hold. However, your situation out on the playa is way less than ideal. Since everything is there to run 208V, I can't think of a reason not to and given the struggles you've dealt with in the past, I'd much rather suggest you take the route that is more than capable of covering your ass (instead of crossing your fingers and hoping the breaker holds) as well as spreading the load more evenly across all the outputs of the generator.

I suggest you investigate 208V single phase air conditioning options as well. I couldn't find any 208 3 Phase window units, but there's a bunch of 'em rated for 208 single phase (two hots and a ground).

Also, does this 2890w max power rating refer to continuous or burst?

Hard to say without measuring. I would err on the safe side and assume burst until proven otherwise. Unfortunately, it's more common in the audio industry to use inflated figures wherever possible. Even reputable manufacturers.

Also, do you think they are referring max power at 1kHz? If yes, driving the amp at frequencies below 60 Hz would drop that max rating by maybe 30% or more then? Even if it was 50% drop, though, it would still be fine, yes? It would just create a little more heat. But that would still be a lot less heat than a Macrotech?

I'm not sure where you got this idea. Maybe I'm not understanding. The amp test thread only showed amplifier output voltage drop below 20Hz.

I imagine being out on the playa is much like being on the moon. No hardware stores and no Amazon 2 day delivery. I'd really like to set you up for an amazing success with as few surprise issues as possible and make your systems as bullet proof as possible.

If you can do 8 four channel amplifiers on subs, one sub per channel, each individual amplifier will have about half the amount of heat to dissipate. You should be fine with two subs per amp channel and 4 four channel amplifiers, but eight amplifiers just adds that much more reliability to a situation you've already had issues with in the past. If it was in my budget, I would personally rather have the one cab per amplifier channel solution. If it wasn't in the budget, two subs per channel should do the job just fine too. Just less cooling capacity per channel and reduced system redundancy. Push come to shove, all 32 subs series/parallel wired could probably be adequately powered by a single one of those amps. Not sure I'd put money on it going full tilt 24hours a day, day after day without over heating. Two additional 4 channel amplifiers could handle the DR's and OT's, or you can put the two top cabs on a channel, two middle cabs on a channel, two bottom cabs on a channel, and OT's on a channel and get it done with a single 4 channel amplifier. I'm pretty sure I'd run mono in either situation.

I'd recommend you base your power needs on the maximum the system can draw, instead of what it might realistically draw in actual operation. You don't want to size your power supply just right, you want a lot more than just right if you want it to be reliable and more importantly, worry free.

If you can split the PA power load over 3 280V circuits (you very easily can) I would absolutely do so. I can't think of a reason not to. It nearly guarantees you wont have any power issues related to the PA power draw. It also spreads the PA load relatively equally across all the outputs of the generator.

I'd recommend Class D amps to keep the power draw and heat down for additional reliability on both fronts.

Bruce brings up a good point about subwoofer driver temperature. I'd like to think you'll have enough system that you wont need to be anywhere near your planned 45V/250W limiter and that you shouldn't worry about it. But, if it's blazing hot out there and the subs are in direct sunlight, I might be curious enough to place a wireless temperature transmitter in one or two of the driver chambers. Copper doesn't melt until it gets to about 2000ºF, so I'm not super worried given your limiting. But, better to be safe than sorry, for sure.

If you end up going the 8 Class AB amplifier route, run them on one 20A 120V circuit, and do your best to keep them cool it may be okay. Might not have any issues. But if you go 5-10 class D amplifiers (4-8 to subs, 1-2 to tops), wire them at 208V as evenly as possible across all the generator leads, and do your best to keep them cool, it'll be highly unlikely you'd experience any power or thermal issues.

I'm going to continue unraveling the how and why two 120V phases separated by 120º become a single 208V sinewave. But, I highly encourage you to verify my wiring propositions with a qualified electrician.

Side note: If you guys are bumping the base voltage up to 130V per leg and you choose a wire gauge that is able to get the three legs to the amp rack with very little voltage loss, it would end up being 225V instead of 208V, which is a good thing.

To calculate final voltage across two hots 120º out of phase, voltage of one leg to neutral x the SqRt of 3 (1.73)

[Seth]

I like the Crowns that I use. Lightweight, cheap, and get the job done with some headroom.

If someone gave you a stack of used high quality class AB amps of equal power to your current amps, would you take the time to swap them into your rack? If so or no, why?

But, what's more important than which amp or processor you choose is whether or not you know how to properly set up the system, Balance the system, and EQ the system.

Stellar advice. I couldn't agree more.

Too often I see venues and engineers try to make the sound the same volume for everyone in the audience, but you have to remember that the public will position themselves where they enjoy the music the most - the headbangers down front getting blasted, those wanting a little rest for their ears will move farther away - don't take that option away from them... get it loud up front and let nature and physics take care of the back of the crowd.

I hadn't considered this point. Gotta remember that, great tip!

While you are rightly concerned about the amps overheating - you haven't addressed the actual driver in the subs. While we don't hardly ever worry about thermal limitations, because excursion is most likely to be what's going to destroy your speakers....in the case of having those drivers moving back and forth 24/7 in 100+ degree heat - it can be a real issue (especially with music that has a kick drum on every beat and constant bass).

I hadn't considered this either. A brilliant level of system awareness I have yet to achieve. I don't know whether I should bow or shake your hand. What's appropriate when addressing a Master?

Anyway, that's the suggestions from the old curmudgeon.

If you're aiming at curmudgeon, you've got a lot of work to do. Stop telling jokes, ridicule some folks now and then, stop being so damn helpful, and pretend it's of great imposition on the rare occasion you choose to take the time to help someone out.

Don't change, Bruce. The world is better as you are.

[Seth]

Levi, it looks like we may be co-authoring a book together. LOL

[Bruce Weldy]

I like the Crowns that I use. Lightweight, cheap, and get the job done with some headroom.

If someone gave you a stack of used high quality class AB amps of equal power to your current amps, would you take the time to swap them into your rack? If so or no, why?

Nope. I have something that works. Even free, I wouldn't want to add and extra 100 pounds to my rack. I have 5 amps in it. And 100 pounds may a low number considering my amp all weight in at 10-12 pounds.

Now, if I was doing an install and heavy iron was available cheap, I'd have no problem using it.

[Seth]

Hope everyone had a great weekend. I reread my last long post and on the second pass, it comes off a little bossy and absolute. If it landed that way with you Levi, I apologize. My goal is to give you the best advice I can, let you take it for whatever it's worth, and make whatever choices you feel best fit for you.

I was a little confused about some of the three phase details and posted to a physics forum I use from time to time when I can't figure stuff out, wrap my mind around something, or need to learn or verify a formula. I finally feel like I clearly understand what's going on and how it works. I'll explain the best I can.

Each series of windings is called a Leg and there are three legs, each measuring 120V to neutral. When connecting a load from the L1 (leg 1) hot to L2 hot, the circuit for PH1 (phase 1) is completed. L2 to L3 is PH2 and L3 to L1 is PH3. A load that connects to all three phases is a 208V three phase load. A load that is only connected to one phase is a 208V single phase load. A load from any one leg to neutral is a 120V single phase load.

The phases, from leg to leg, are definitely pure sinewaves. I originally thought the waveforms of the two legs combined and summed in the same way that soundwaves interact with each other, but the math was not working as it should, the summed voltages were not mathing out to what they should be with that method of thinking. On the contrary, the waveforms do not sum at all. There's nothing additive about it. As it turns out, the truth is quite the opposite. The resultant sinewave is purely a product of the voltage potential difference between the two legs at any point in time. At any point on the graph, L1 voltage minus L2 voltage equals phase voltage at that point. So, in essence, one could visualize it as the same as having a neutral, except that instead of a constant value of zero, the effective "neutral" value is changing too. If the two legs were aligned, no degree of separation, there would be no voltage differential between the two and the resultant phase voltage would be zero. And if they were 180º out of phase the voltage differential, +120V to -120V would be 240V.

In the chart below, you can see where the leg voltages cross each other above or below neutral, the voltage differential is zero and the phase voltage at that point is zero. At the phase peaks, it's the differential that creates the peak. The positive amplitude of PH1 at that point is 207.8V, L1 is at 103.9V and L2 is at -103.9V. So, the wire that would normally be connected to the neutral side of an amplifier stays at zero, where in this case the "neutral" line is moving too, creating greater differentials than if it were to remain at zero.

It helped me to visualize and grasp when I looked at blue as hot and red as "neutral". Then I was able to see the difference between them as the phase voltage above or below zero at that point in time.

Does that make sense?

You were spot on, 100% correct that a hypothetical alternator/generator with two legs aligned in phase they would have the same voltage, yet deliver twice the amperage in relation to neutral, if a neutral were connected on one side of the load and the two legs on the other side of the load.