BillFitzmaurice.info

The thought of adequately competing against ultra high dollar commercial systems with a cab loaded with $130 drivers tickles the heck out of me. I love the idea.

As always, I am a total stand and ambassador for building maximum width cabs. Let the horn do as much work as possible. Every decibel earned at one watt of input is worth hundreds, if not thousands
or tens of thousands of watts at the maximum potential output of a system like this. However, a system like this could also benefit from double loaded cabs, wiring the drivers in series, maximizing the number of cabs that can be run on an amplifier channel. But, a 40" wide 2x 12 T60 would be an absolute behemoth and PITA to transport.

If it were me, I think I'd build single loaded max width cabs and just create exterior wiring harnesses that connect two cabs in series and have parallel pass through. Although, running two series wired 8Ω drivers to their limited peak voltage would take an amplifier rated and capable of an honest 1600 watts per channel RMS at 8Ω. Granted you can run 16 cabs on a single amp that way and still only be at a 4Ω load, the argument could also be made that splitting the load among multiple amplifiers of lower rated power could add safety and backup should a failure occur. Or it could also be possible that 4 amplifiers in the 400wpc neighborhood could cost less than one amplifier rated at 1600wpc.

In any case, the point is, if it were me, I'd probably opt to make single loaded max width cabs and doing so with $130 drivers is ridiculous (in a good way).

Calculating it out (and assuming my figures are roughly accurate, although not perfect), it would take twenty-seven single LAB12 loaded 20" wide T60's to match or exceed the maximum output potential of sixteen 27" LAB15 loaded cabs for their entire operating range of 25Hz and above.

Levi wrote: ↑Sun Mar 17, 2024 2:47 pm<snip> We will not go wider than 30", because we have about 90" total width to store them. So 3x30" would be just right. <snip>

If all you have is 90" and no more, then I suggest building the cabs at 29 1/2". The reason is that the Duratex will add a touch of thickness, and so will the cab corners (if installed). Also, it's nice to have just a bit of wiggle room when loading into a narrow width storage.

Can you imagine the look on peoples faces if/when you told them you were using 12" drivers? (especially people from other camps with respectable systems) And then told them they cost $130. Then casually mumble under your breath, something about only having 11kW worth of sub amps. My guess is they'd think you were lying, pulling their leg.

Seth wrote: ↑Sun Mar 17, 2024 8:17 pm Again, point of view. From the standpoint of maximum volume potential 3-4dB isn't a big difference in perceived volume, barely perceptible actually. However, if you wanted to increase your maximum output 3-4dB, it's absolutely MASSIVE when talking about a system of this magnitude.

I'm glad you mentioned this Seth, can you explain the difference between db value of maximum volume potential and maximum output please?

Keryn O'Shea wrote: ↑Mon Mar 18, 2024 4:12 am

Seth wrote: ↑Sun Mar 17, 2024 8:17 pm Again, point of view. From the standpoint of maximum volume potential 3-4dB isn't a big difference in perceived volume, barely perceptible actually. However, if you wanted to increase your maximum output 3-4dB, it's absolutely MASSIVE when talking about a system of this magnitude.

I'm glad you mentioned this Seth, can you explain the difference between db value of maximum volume potential and maximum output please?

Maximum volume potential and maximum output are the same thing, with the possible exception of potential meaning it's not turned up and max volume suggesting it is. The context of the statement is essentially that 3-4dB is almost insignificant when viewed from the perspective of the listener. But, if you were to want to plan and design a system like we're discussing and have an additional 3-4dB of headroom (or actual output), that equates to doubling the cab and amplifier count, which is a MASSIVE undertaking and very significant. Sometimes I talk about a couple/few dB like it's nothing and other times I talk about a couple/few dB like it's a big deal and that's why. It's not that I'm flippy floppy with my opinion, it's that in one context it's not such a big deal and in another context it is.

@Seth

Right on, thanks again for indulging me on all the things!

Wow, that is an insane amount of cabs!

So… going from 8 to 16 cabs will only give an additional 3db or so? 3.1db? Is that with the same amount of power that it takes for just 8? Or double the amount of power, so that each of the 16 cabs is getting the same amount that the 8 would before the doubling? I suppose your list from before assumes the doubling of cabs AND power.

"2 cabs +6dB
4 Cabs +12dB
8 cabs +18dB
12 cabs +19.8dB
16 cabs +21.1dB
20 cabs +22dB
24 cabs +22.8dB
28 cabs +23.5dB
32 cabs +24dB
36 cabs +24.6dB"

I guess I’m not understanding the efficiency limit concept. Or, I just refuse to accept it. To use the terminal velocity analogy, yes, I reach a limit with my current body weight, jumpsuit, body position, etc. But wouldn’t doubling my weight still allow me to fall faster? Yes. But then there’s even more air resistance at the faster falling speed. So, I fall faster, but at a slower rate compared to the previous doubling. Okay, this makes sense. It’s just tough to believe there is such a sharp decline in gain from the 8 to 16 level! From 4 to 8, there’s no problem gaining an extra 6db. But, according to that list, from 8 to 16, there’s only a 3.1db gain… Man, what a difference!

So far we have only done cursory autopsies of the cabs. Most of them are rattling. The exact source of the rattling varies. Some are failed joints. Maybe this is from hard bumps on the road, or maybe the over tightening of straps on the trailer. Or both. Some are failed seals. They might work fine once replaced, I don’t know yet. Some have blown drivers. Some are just dead - no sound at all. Might be that the actual driver is cooked, or maybe wiring came loose, or was severed, not sure yet. We believe these dead ones are the result of a rogue operator last year who decided that one night, against explicit instructions strictly forbidding it, switched around cables and such to bypass the limiter. Of course, that is a big boo boo. This person is now forever blacklisted from our camp. When we get a weekend to do the full autopsies, I will definitely post updates!

Point taken on the nominal impedance levels. Just to clarify, don't the charts already take into account the extra 2 ohms from the cabs, so all is well for comparison from that angle? So Bill’s T-60LAB15 chart is okay for the 101db ish at 50Hz?

Side note, I know I am probably using the word “power” in a clumsy manner, but it was meant in a sense that the cabs would get what they need - from appropriately sized amps, and an upstream electrical source, to get what they needed for more sound output.

Great point on the additional 3-4db additional output at high levels! Seems like it’s definitely worth thinking about now in the planning stages!!!

Thanks for the link on loudness contours! Can’t wait to get into that side of the process!

Oh, and what is this “Stars Wars” talk you speak of?

And yes!!!

“The thought of adequately competing against ultra high dollar commercial systems with a cab loaded with $130 drivers tickles the heck out of me. I love the idea.”

Right?! Right?!!!

Agreed, the 2x12 20” version seems like the way to go for max output. To address the PITA transport and storage, I am flirting hard with doubling up with the 1x12 version, with the series harness, and the rest of your recommendations.

We’d definitely split the load between multiple amps. So many things go wrong out there every year. It’s nice to have backups and all that.

We’d most likely be running Crown Macro-Tech 5000i amps, but I am open to suggestions! We currently run 4 x T60-LAB15s per amp, which seemed to work out perfectly for the 1200w program power per LAB15… 4 x 1200 = 4800… Just under 5000. Or, probably the better way to read it, is 1250w rated for 8 ohms dual per channel.

https://www.crownaudio.com/en-US/products/ma-5000i

What do you think?

Oh man, we are on the same wavelength! Again, most of these big sound camps and art cars have exponentially higher budgets than us. (As you might recall, we are single-celled potatoes after all!) Being able to own our system (instead of renting), powering it with way less equipment, and still dishing out dirty beatz… for pennies on the dollar… jaws will be dropping! That’s right, fellas, we said 12” drivers. 12 inch!!!




@Tom

Hi, Tom! Thanks for the insights!

Sorry, I should have clarified. The 90” accounts for a little wiggle room in a 8’x8’x20’ shipping container. It’s more like 91-92” or so, from the inner corrugation on one side, to the inner corrugation on the other side. We already have other materials in there that are 90” that fit comfortably.

Our current cabs do not have corner protectors. The corners are actually in good shape, so we probably won’t install them on the new builds either.

Great point about the Duratex! You have opened another can of worms!

We did not paint the old cabs. Instead, we stained them. The stain held up surprisingly well, even with the absurd amount of alkaline dust and occasional rainstorm that they have seen.

When stored in the off season, the cabs will be in the aforementioned shipping container. That container is then stored near to where the event occurs. It is on the outskirts of the Black Rock Desert, just out in the open. This means the conditions inside of it vary wildly by season. It gets cold and snows. It rains from time to time. And it gets blisteringly hot, of course. Drastic changes in temperature and humidity over the course of a year.

A big question in our internal discussions, therefore, has been…

How the hell do we make these things as bulletproof as possible?!

Sanding, edge sealing, adequate staining, and then some type of UV varnish?

Also, I’ve called the local lumber yards. We can get two types of Baltic birch plywood. The 5’x5’ version, and the 4’x8’ version. Both are 9 ply, BB grade, and about the same price per square foot. The 5x5 is what we used for our old cabs.

One thing I discovered this time around, though, is that the 5x5 uses an interior grade clear glue to hold the plys together. The 4x8, on the other hand, uses an exterior grade phenolic resin. Does this matter?

If we end up staining again, is it worth it to go for the exterior grade 4x8? For durability’s sake? I suppose I should snap some photos of how the old cabs have weathered. They didn’t seem too bad from a quick glance, but they are also still covered in dust, so it’s hard to tell. I know for sure that they aren’t exactly smooth anymore. This dust, by the way, is like talcum powder. Super fine. It gets everywhere. And it’ll instantly dry out your skin. And lungs.

The cut lists with 4x8 (versus the 5x5) would probably be better with the single 12” version, up to about 18.5-19” wide. (48”, less 30” and the saw blade width for about 18”, plus about 1” with the two side panels.) Which unfortunately would be a little over 1 inch less than the 20” width for maximum output. This is all assuming that we don’t want to do any remnant piece joining, because we don't. For this many cabs, it would be a real pain. But I also don’t want to get too crazy with extra plywood sheets, either.

Decisions, decisions. When the rubber meets the road and all that… Where exactly might the sweet spot be?





I will hopefully have tuning info to share tomorrow night!

Levi wrote: ↑Mon Mar 18, 2024 7:44 pm Agreed, the 2x12 20” version seems like the way to go for max output.

Levi, did you mean 2x12 30" version?

Levi wrote: ↑Mon Mar 18, 2024 7:44 pm To address the PITA transport and storage, I am flirting hard with doubling up with the 1x12 version

Do you have help to setup? I'm trying to see the advantage performance wise, with using the single 12" driver in light of this..

Seth wrote: ↑Sun Mar 17, 2024 9:52 pm Calculating it out (and assuming my figures are roughly accurate, although not perfect), it would take twenty-seven single LAB12 loaded 20" wide T60's to match or exceed the maximum output potential of sixteen 27" LAB15 loaded cabs for their entire operating range of 25Hz and above.

I would see myself in your situation with a deadline; Taking stock of the original subs to see if you have much to work with there, if you can salvage more than 4, I'd build the rest the same. If not, I would start fresh with the 2x12 30". The LaVoce driver looks impressive! Just my view from a building perspective, not trying to advise you. I deliberated on this post as I don't want to cause you any more confusion in your decision!
Are you building the subs yourself?

Levi wrote: ↑Mon Mar 18, 2024 7:44 pm So… going from 8 to 16 cabs will only give an additional 3db or so? 3.1db? Is that with the same amount of power that it takes for just 8? Or double the amount of power, so that each of the 16 cabs is getting the same amount that the 8 would before the doubling? I suppose your list from before assumes the doubling of cabs AND power.

I guess I’m not understanding the efficiency limit concept.

This audio concept is new to me too, so I did a little digging around. I'll explain what I've gathered, but take it for what it's worth. I like math and I know some audio stuff, but I'm not a guru. Just a dude that's happy to pass on what I've learned and hopefully learn some more stuff along the way too. I'm pretty sure this is accurate information. However, it may not be 100% so.

The perfect horn mouth dimensions would be such that they create a mouth area equal to the area of a circle which has a circumference of the wavelength of the lowest frequency the horn is designed to reproduce. That perfect size horn mouth is as efficient as the horn can possibly be. Because that area is so large, it's impractical to make portable subwoofers with dimensions that will meet the required mouth area to achieve maximum efficiency. So, portable cabs are only capable of producing a portion of the highest potential efficiency. Multiple cabs increase output at a rate of 6dB (roughly, it's actually 6.0206dB) That 6dB is created by combined factors, 3dB for doubling system power and another 3dB for increasing the mouth area until the combined mouth (or throat) area equals the area of the specific frequency. Once that combined mouth or throat area is equal to the area of a circle with a circumference of the frequencies wavelength, maximum peak efficiency has been achieved at that frequency.
Additional cabs beyond this number will no longer contribute to having the perfect mouth area, it has already been achieved, they will only contribute additional output from the additional power they add to the system.

I know that's wordy. I'll break it down for you.

The speed of sound varies slightly with atmospheric conditions, but I always just use 1125 feet per second. If you wanna use 1123 or 1128 or any other number that's close, it's close enough for what we're doing here.

To calculate the length of a soundwave it's simply a matter of dividing the speed of sound by the frequency. 1125fps ÷ 60Hz = 18.8 feet, 50Hz = 22.5, 40 = 28.1, 30Hz = 37.5 feet, 20Hz = 56.3 feet

So to calculate the area of a circle with a circumference equal to the frequency, I first convert the circumference to diameter by simply dividing the circumference/wavelength by Pi. I'm going to do these numbers based on a Titan 39. Not a cab we're talking about, but there's a reason and a point that I'll come back to a little later. The bottom frequency of the T39 is 40Hz, 1125fps ÷ 40Hz = 28.125 feet ÷ π (3.1415) = a circle diameter of 8.95 feet. Then I just convert it to area with the 'ol πR². Half the diameter gives me a radius of 4.475... 4.475 x 4.475 x 3.1415 = the perfect horn area for 40Hz of 62.9 square feet.

So doubling the cab count of T39's will get +3dB for doubling system power and +3dB for doubling mouth area until the combined mouth area is equal to 62.9 square feet. Additional cabs will only contribute an additional +3dB after that point.

Using this info, I can easily look at the mouth dimensions of the T39 and quickly math out how many cabs it will take to reach maximum efficiency. T39 mouth height is 25" and using max 28 width results in an inside dimension of 27". 25 x 27 = 675. Divide that by 144 (inches in a square foot) will give me T39 mouth area of 4.9 SqFt. The perfect horn area of 62.9 SqFt divided by 4.9 SqFt per T39 tells me it will take 12.8 (13) max width T39's. So, the 14th T39 and beyond will only add 10LOG (3dB per cab doubling) to the system output. For practical reasons, a stack of 14 max width T39's is pretty much never going to happen.

So, why did I use the T39 and not the T60? It's easy to know the mouth dimension and the bottom frequency of a cab. But, frequencies higher than the bottom frequency aren't produced at the mouth. They come out of the mouth, but the portion of the horn that equates to a particular frequency is a quarter wavelength from the driver end of the horn and there's no easy way to determine what the throat area is at any given point within the horn path. So I could use this quick and easy calculation to determine how many T60's it would take to reach maximum efficiency at 25Hz but the calculation wont work at 40Hz since the area dimensions of that portion of the horn is not easily determined. It would take 30.8 LAB15 T60's to achieve maximum efficiency at 25Hz and from what Bill says, it will achieve max efficiency at 40Hz with eight cabs.

As you add cabs to the stack the lowest frequency that is at maximum efficiency gets pushed lower and lower. So, at the lower frequencies sensitivity is still increasing at a 20LOG rate (6dB per cab count doubling) while higher frequencies that have already maxed out efficiency are increasing at a 10LOG rate (3dB per cab count doubling). So it's something that changes every time another cab is added to the stack, not just per doubling cab count... Until the total combined cab mouth area is equal to or greater than the area of a circle of which it's circumference is equal to the wavelength of the lowest frequency.

The only good way to determine various frequencies and cab counts to reach peak efficiency is to use the modeling software HornRepsp, which isn't as quick to do, but provides much more complete information.

Hopefully that didn't just make things more confusing.

Point taken on the nominal impedance levels. Just to clarify, don't the charts already take into account the extra 2 ohms from the cabs, so all is well for comparison from that angle? So Bill’s T-60LAB15 chart is okay for the 101db ish at 50Hz?

It's fairly standard in the industry to use the driver's impedance rating independent of any effect the cab has on impedance. So, while the charts do not take cab impedance into account, anything you compare it to hasn't either. So, you're all good in that department.

Just me personally and the way I compare things in my mind, I prefer to reference 1W/1M. So I personally look at the LAB15 T60 chart and see just shy of 100dB at 50Hz 1W/1M. Again, the difference between 6Ω and 8Ω at any voltage is 1.25dB. So you could add that to whatever 8Ω cab you may be comparing it to or remove that amount from the T60 sensitivity.

We’d most likely be running Crown Macro-Tech 5000i amps, but I am open to suggestions! We currently run 4 x T60-LAB15s per amp, which seemed to work out perfectly for the 1200w program power per LAB15… 4 x 1200 = 4800… Just under 5000. Or, probably the better way to read it, is 1250w rated for 8 ohms dual per channel.

https://www.crownaudio.com/en-US/products/ma-5000i

Those amps are well suited for your needs. And, if one failed, they actually have enough power available to power 16 cabs per amp, 8 cabs series parallel wired would be a 4Ω load per channel and only be -3dB from peak output. Not bad for an emergency backup plan. Would just have to have series/parallel adapter cables made and ready to go.

The portion I highlighted in red is a little worrisome. But, you mentioned you guys were running limiters. So I'm not sure. I'll just put it out there that if you put the drivers program power (1200W) through them it very well could have damaged them. Using the brickwall limiter in your Driverack is 100% mandatory. With a brick wall limiter properly set to 60 volts, the power is effectively limited to 600 watts. If you guys intend to continue to running 2 cabs per channel on that model amplifier, it's a little unconventional, but you may consider running each channel pair in series in an additional effort to help prevent blown drivers from stupid mistakes and stupider people. A good thing about using that amp with 2 cabs per channel is it's essentially only going to be at half capacity when the system is maxed out on the limiter, which is good to help keep them cool in such a hot environment.

We did not paint the old cabs. Instead, we stained them.

I know it's an art festival and all. And maybe it's just me, but my opinion is you should make these look as professional as you'd like them to sound.

How the hell do we make these things as bulletproof as possible?!

Construct them with the methods and supplies recommended in the plans. Don't use the minimum number of braces per panel. Treat them like they cost as much as their competition. And yeah, go easy on the ratchet straps. Too tight breaks shit. It's not like we're strapping a car to a trailer. Snug it up and test the stability. Snug it a click at a time until you get the desired result.

One thing I discovered this time around, though, is that the 5x5 uses an interior grade clear glue to hold the plys together. The 4x8, on the other hand, uses an exterior grade phenolic resin. Does this matter?

5x5 sheets have been the standard around here. I don't know about the ply glue status though. Maybe some of the other more experience woodworker guys has some input on this?

I will hopefully have tuning info to share tomorrow night!

That would help in figuring out whether what you felt you were missing was in the tune or not. I look forward to it.

@Keryn

Oops! My bad! Thanks for catching that! Actually, I meant 2x12 40” (or 39” actually). Just referring to the behemoth PITA to transport bit there.

And yes, we have a crew to help set up and strike (aka tear down). However, I know at least for this year, we will not have any room in the shipping container for sound equipment. (We are trying to get another one, but the prospects are doubtful.) Therefore, I need to plan on hauling these little piggies all the way down there AND back. And that means wrangling them onto the top deck of our layer cake of a flatbed trailer. Quite the workout!

Don’t get me wrong, loading and unloading 30-39” wide T60s is totally doable. But. But. At the end of a very short, and also a very long week, out there, in the blistering sun, making things like heavy lifting easy on weakened and fragile bodies is definitely worth it. (Some years we’ve had to exclusively work throughout the night, and not at all during the day, to get some relief from the heat and sun. Manual labor in the desert is no joke!)

So, even if it costs a little more in lumber and hardware, and even if it takes many, many more labor hours in the shop to build, making things as easy as possible out there is always the way to go. Plus, we can very easily Tetris 32 x 1x12 20” cabs into the shipping container when it becomes available. Tetrising 16 x 2x12 39” cabs… definitely not. The pieces just don’t fit as well. 30” yes, anything over that, no. Also, it seems like we might have more configuration and easier scaling options with the 1x12s. That could be fun to play with from year to year! Especially if we don’t get the plot size that we request. The Burn is like a box of chocolates…

Also, thanks for putting yourself in our shoes. Lots going on here! Lots to consider! It means a lot to get help with a project like this!

We love the idea of getting the max output that Bill’s designs can do. If that means repurposing the LAB15s for something else, and going the 12” driver route, so be it.

Also, if we do 20” wide 1x12s, as opposed to 15” wide 1x12s, that will create an impressive dancing stage/platform of tubas all in front of our DJ booth. There will be less frequent seams/gaps between the subs to deal with if we do 20” wide, and probably way less propensity to tilt side to side under people’s feet. Or would there? We never had trouble with any tilting with the 27” LAB15s. They are stout! Any wider would be just fine, too. The question is, at what point might a dancer, when dancing their danciest dance moves, land on the edge of a 1x12, in the 15”-20” range, and end up rocking the sub side to side? Maybe even tipping it over onto its side? Seems way more likely a 15” would tilt. A 20” less so. Does anyone out there have a 20”? Are you able to do a test run? Maybe we need to plan on securing at least the end one(s) down.

Yes, we will be building the subs ourselves! One of the fun parts of the Burn is that it has a strong maker/DIY vibe. (There are some that buy their burn, instead of build their burn, but they stick out like a sore thumb and get zero street credzzz.) Luckily, we have a shop with full tools that we can use. And if we must sacrifice to make the deadline happen, well then gosh golly gee we must do it! After all, there are thousands of other folks doing the same thing. And that makes it all the more exciting when it comes times for the big show-and-tell!

Hopefully, we can salvage as many of the old tubas as possible. But we are thinking we might just use them as a secondary sound system that can stay local. After all, those boys have seen enough of the desert… maybe they’d like to retire to the mountain party scene!




@Seth

Oh man! My brains are tingling, light bulbs going off all over the place! That makes so much sense! Thanks for such a thorough and elegant explanation on this!

Okay, now, riddle me this then…

Using your Hornresp skills, if I may…

What would be the chart on 32 x T60-LAB12 20” wide subs? Versus other quantities and versions of the T60 that have been discussed?

This 32x system seems to be the super-ultra-mega-awesome option that is right at the cusp of practicality. We get the maximum output while minimally respecting the party poopers of storage, transport, cost, labor, etc.

Or maybe the cusp is really somewhere different? Fewer cabs, perhaps? Or maybe we go back to the LAB15 version?

Uggh, here I go, wavering again. So annoying!

Let’s see, Bill likes the 16 x T60-2x12-30” setup...



@Bill

Is a system of 16 x T60-2x12-30” the practical cusp, then? I’m not intending to cast doubt or anything! With all these options, my head is spinning a bit. I’m trying to understand why the master thinks the way he does! Because I obviously don’t know squat.

If I had to guess, quantity 16 comes from a storage and transport perspective that I offered up initially. As well as an efficiency limit perspective... That’s why you said even just 8 would do the job, yes?

The 2x12 cab wins, versus 1x15, because it gives more output. It is enough of a gain that it is worth the extra effort, money, etc. Is that the thinking?

30” wide wins, versus any wider options, because it minimizes the weight/moving hassle. As in, the hassle isn’t worth the extra 2db gain?

Also, I’m just curious… What is the “biggest” Bill Fitzmaurice system out there, in the wild? Is it a gazillion T60s with 5.37 million DR280s? Powered by its own exclusive fission plant? Can it destroy planets in one shot? Hmmm? Hmmm?



@Seth

Sorry! I should have added more detail. We got those amps based on the program power level. Because we’re supposed to size them 1.5-2 times up I thought, yes? We definitely don’t run them at that level, though. Phew!!!

About the stain… yes, it’s artsy I suppose, compared to the norm. But actually we were thinking more in practical terms - about their living conditions. I’m not super familiar with Duratex, but in our experience, anything that’s been painted that is left in the shipping container tends to stick to itself or others. In a way I guess that shipping container is more like a kiln. It sure does get hot in there… How hot? No idea. I tried to research that, and one site said that inside the construction site containers in Arizona temps got to 140 Fahrenheit. I dunno. Anyway, when it sticks, then the paint comes off in chunks when we separate them. This has been heartbreaking at times. We put in all this work to make things “pretty”, just to discover a year later when we pull them out of the shipping container, that it was for naught. Again, we haven’t done that with speakers. Maybe Duratex is different. But it would be a real bummer to see it come off in chunks! Anyway, looping that back around, we have not had that problem with anything that we have stained, T60s included.

The ratchet straps… You can crush anything with a Hi-Test! It can be a tough Goldilocks scenario getting them just right. My guess is that at some point(s) over the last ten years, a strap or two have been ratcheted too tight. Not good. But then there’s also the reverse problem. Too loose. Story time. On the way back last year, we hit a big bump on I-15 at night, and Boom! One of the tubas toggled enough that the strap came loose, and we lost a tote next to it. Man overboard! (Yes, don’t worry, we check every strap at every stop, tightening as needed.) Very scary to watch everything shift at that speed. That said, the flatbed is so long, and it was so dark, that we couldn’t see right away that anything had happened, until we stopped at the next exit. (Someone in Idaho found some hilarious treasures in that tote!) Anyway, I think we might play around with screwing 2x4s and whatever else to avoid shifting, over-tightening, and lost luggage. Just gotta be overly cautious and all. We get better with every year!



Also, I’ll throw this out randomly… What about the following sub configuration? All subs in a single row in front of the booth. This would probably be… 32 x 20” = 53’4” + 31 x ½” gaps between to prevent rattling = 54’7.5”... Whoa! That row of subs would be almost as wide as the 56’ of separation we had between stacks last year! It would almost fill in that entire hole! Crazy! Maybe we should try to condense that a little bit… Maybe stack 2 high in spots or something… Pros? Cons? Higher decibels in a narrower spread, perhaps?




Also, I tore apart the house for tuning info. No dice. I will have to make a trip to the shop and get it there. This weekend at the latest!

Levi wrote: ↑Wed Mar 20, 2024 9:08 pm
So, even if it costs a little more in lumber and hardware, and even if it takes many, many more labor hours in the shop to build, making things as easy as possible out there is always the way to go. Plus, we can very easily Tetris 32 x 1x12 20” cabs into the shipping container when it becomes available. Tetrising 16 x 2x12 39” cabs… definitely not. The pieces just don’t fit as well. 30” yes, anything over that, no. Also, it seems like we might have more configuration and easier scaling options with the 1x12s. That could be fun to play with from year to year! Especially if we don’t get the plot size that we request. The Burn is like a box of chocolates…

+1
Perhaps go 24" width?

Levi wrote: ↑Wed Mar 20, 2024 9:08 pmAlso, if we do 20” wide 1x12s, as opposed to 15” wide 1x12s, that will create an impressive dancing stage/platform of tubas all in front of our DJ booth. There will be less frequent seams/gaps between the subs to deal with if we do 20” wide, and probably way less propensity to tilt side to side under people’s feet. Or would there? We never had trouble with any tilting with the 27” LAB15s. They are stout! Any wider would be just fine, too. The question is, at what point might a dancer, when dancing their danciest dance moves, land on the edge of a 1x12, in the 15”-20” range, and end up rocking the sub side to side? Maybe even tipping it over onto its side? Seems way more likely a 15” would tilt. A 20” less so. Does anyone out there have a 20”? Are you able to do a test run? Maybe we need to plan on securing at least the end one(s) down.

The two cabs, one set on either end,...ratchet strap them together with the ratchet on the outside. This will, then, give a 40" width.

Levi wrote: ↑Wed Mar 20, 2024 9:08 pmAbout the stain… yes, it’s artsy I suppose, compared to the norm. But actually we were thinking more in practical terms - about their living conditions. I’m not super familiar with Duratex, but in our experience, anything that’s been painted that is left in the shipping container tends to stick to itself or others. In a way I guess that shipping container is more like a kiln. It sure does get hot in there… How hot? No idea. I tried to research that, and one site said that inside the construction site containers in Arizona temps got to 140 Fahrenheit. I dunno. Anyway, when it sticks, then the paint comes off in chunks when we separate them. This has been heartbreaking at times. We put in all this work to make things “pretty”, just to discover a year later when we pull them out of the shipping container, that it was for naught. Again, we haven’t done that with speakers. Maybe Duratex is different. But it would be a real bummer to see it come off in chunks! Anyway, looping that back around, we have not had that problem with anything that we have stained, T60s included.

Get the Duratexed a month before the gig so that it has a proper cure. Oh, and rotate them occasionally so that the Duratex doesn't bond to something else (I had this happen to me when I had coated some plates, and kept them sandwiched)

@Tom

I thought there was no additional gain in anything over 20" width for the 1x12 T60... Is that correct?

That's a great idea to secure the end straps! Thanks!!!

So, if Duratex completely cures, you think it will have no issues living in a shipping container/kiln/ice box for 350 ish days? We do not have easy access to the container in the off season, and will not be able to rotate them.

Levi wrote: ↑Thu Mar 21, 2024 8:53 am @Tom

I thought there was no additional gain in anything over 20" width for the 1x12 T60... Is that correct?

Ugh, silly me.

Levi wrote: ↑Thu Mar 21, 2024 8:53 amThat's a great idea to secure the end straps! Thanks!!!

You're welcome.

Levi wrote: ↑Thu Mar 21, 2024 8:53 amSo, if Duratex completely cures, you think it will have no issues living in a shipping container/kiln/ice box for 350 ish days? We do not have easy access to the container in the off season, and will not be able to rotate them.

Once fully cured, Duratex will be solid. Should be no problem as far as I can see.

Tuning

Okay! I finally got our tuning/limiting info!

Here we go, from our Driverack:

High pass: 92.6Hz
Mid pass: n/a
Low pass into subs: 26 - 70Hz
Limiter high: -10db with overeasy compression 10
Limiter low: -18db with overeasy compression 10
High EQ Band 3: 7.87kHz, 5.9db gain, slope 3
High EQ Band 2: 207Hz, 6.8db gain, slope 3
High EQ Band 1: 922Hz, 5.1db gain, Q 0.64


Again, this is for an outdoor, wide open, dried up lake bed in the desert. Thoughts?

Power Mapping

We want to run everything in parallel. (Don’t we?) How many ohms do we use? 6 ohms for the LAB12 driver? Do we add 2 ohms for the cab? So do we count 8 ohms total for amp load?

Does anyone know what the ohm rating for the DR280s is? We hope to use the KL 3012HO woofer and the NSD-2005 HF compression drivers. What if we use the BMS H4552ND drivers instead?

Also, it seems like we can get decent deals on a few different types of amps. Assuming we do 32 x T60LAB12s… and 6 x DR280s…

How would you map it all out?

How many Crown Macro-Tech 5000i amps would you use? (Having more, lower-powered amps would help bail us out if one failed...)

https://www.crownaudio.com/en-US/products/ma-5000i

How many Crown I-Tech 12000i amps would you use? (Having fewer, higher-powered amps might cost less...)

https://www.crownaudio.com/en-US/produc ... ch-12000hd