Are 24 x T60-LAB15s Enough? ;)

[Bill Fitzmaurice]

OK, I found the B2 design specs. It is a bandpass, it's not a horn. There's a horn like exit on the front chamber in that it's tapered, but with a length of some 40cm it would only horn load to 800Hz. Like all bandpass they have fairly high sensitivity, better than reflex but not as good as a horn, with a narrow band width.

[Seth]

Great point about a sealed option for the DR280s! And at least 3 on each side, sounds good! Do you think there would be any downsides to just strapping them down on top of the subs? I know you said the bottom one should be just above head level, but if we shade them properly, do you think it would be just as acceptable to stack them on top of 2 x T60s? So about 5’ off the ground for the bottom DR280? Like we did here, but with the 2 corner pieces on top, so they are 3 high:

That has a good visual appeal, but it's not ideal for sound. It would be way better to so a three stack instead of the 2 and 1 shown in the photo and get the bottom cab above head level. Stack up on some scafolding. 8 foot if you can, 6 foot scaffolding and a 1-2 foot box/spacer under the stack would be okay too. If you have to strap them to the subs, I'd do the DR's 3 high per side, utilize the ground stack bracket, "J" array, and put something under the stack to elevate it another couple of feet if it can be done in a way that is still safe, sturdy, and highly improbable/impossible to knock over.

It's difficult to tell for sure in the photo, but it appears the DR280's may have been made without the 8 degree splay angle? Ye, ne?

Also, that is a very interesting point about the T48s having increased sensitivity above 40Hz. Maybe it is worth giving up that low low end for a bit more low end…

Which brings me to my next question…



@Bill

But if we are talking about doing 4+ x T60s, then does that benefit/tradeoff disappear? So the T60 is the best way to go if we are talking 16+? Because we get all the sensitivity of the Titans in that 40-60Hz range, in addition to the lower extension of the Tubas? And this holds true no matter how many Titans we have, even if they significantly outnumber a set amount of Tubas? Is that what you meant?

Or, to put it another way, if we have something bonkers like 32 x T48s, is that not any better than 16 x T60s? I guess that assumes the same amount of power going through them, and all other things held constant… But what if we have twice the power as well? Or does that matter at all?

If I understood Bill correctly, and Bill please correct me if I'm off base, the first 8 max width cabs of either design will scale at 6dB per doubling cab count (3dB for increased efficiency, 3dB for doubling power) and additional cabs beyond that are just 3dB per doubling of cab count for doubling system power, but no additional increase in efficiency.

I have to assume this is a product of the throat and/or mouth area and not an actual cab count, so 8 minimum width cabs would probably not meet maximum efficiency. Just a guess though.

Calculated out this way, using 8 cabs as the point at which 40Hz is at it's maximum efficiency gain:

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

In this thread you say you have 8 T60's, but the photo shows 12. In any case, it looks like you will need 80 cabs to double the perceived output (10dB) if you used 8 before. Yikes!! You can add the figures above to your calculated max SPL of a single cab to get the entire array's potential output at 1 meter (3.28 feet). To calculate SPL at distance, subtract 6dB for every doubling of distance. Two meters away, minus 6dB. Four meters away, minus another 6dB...

As I mentioned in the original post, we are going up against the gold standard, which happens to be a D&B system…

If you do this right, you'll be the new Gold Standard.

What does this mean, exactly? What is max SPL? Is it just like it sounds? The absolute highest decibel level at whichever frequency(ies) a speaker can reproduce, before it done get all blowed up? So in this case, would it mean that the B-2 gets 139db at 50Hz-ish when they are running at max power indoors? Which the manual says is 600W RMS / 2400W peak 10ms. Nominal impedance 4 ohms.

I've found in nearly all cases, advertised max SPL is simply calculated by adding sensitivity dB to Rated Power converted to dB. In nearly every advertisement/info/spec sheet I've ever seen, they usually use the unreasonably lofty "peak" power rating to inflate the number making it look better than it actually is in reality. Furthermore, some of the shadier manufacturers use the highest sensitivity that occurs in the sweep. More reputable manufacturers use the average sensitivity. Personally, when I do my calculations, I like to use the least sensitive reading in the usable frequency range and the more realistic RMS power rating. This results in a figure that is achievable for realistic long term output.

Sensitivity is typically done as a half space measurement, which is essentially the same as sitting on the ground outdoors.

In the spec you posted, 2400 watts is +33.8dB. Subtract that from 139dB max SPL should give us the sensitivity they "think" they have, 105.2dB on 1 watt measured at 1 meter. Ultra unlikely that's a real number. And if it is, I guarantee it's above 100Hz, not even in the usable frequency range.

A little more about why calculating it this way is complete bullshit is, there's a certain amount of cone travel in a driver where cone movement is very closely relative and linear to the signal voltage, where the coil is within the flux of the magnet. All of Bills limits are based on keeping the driver within it's designed operational limits. When a driver is pushed beyond and the excursion is such that the coil becomes less and less in the magnetic flux, the cone movement becomes less and less linear. Just making up numbers to illustrate the point, if a driver is moving 10mm one direction with 50 volts, and 10mm is it's limit for linear travel, 100 volts will not move the cone another 10mm because the coil is too far out of the magnetic flux to have a linear effect. Soooooo, calculating maximum SPL with a driver's thermal power failure limit as if the cane travel is linear all the way to that number is complete marketing bullshit and has zero usefulness in gig planning and deployment. It's a number for unknowing people with credit cards. That's it.

So that we can compare apples to apples, do we know what a “max SPL” of a T60-LAB15 is? Or does that even matter? I don’t know…

Since their apples are rotten, we can't really compare unless you want to use rotten numbers too. I'd rather not, but why not? Let's see what a load of bullshit useless figures equates to. Using 107dB sensitivity (highest I see on the plot) and 1200 watts (LAB15 peak power rating) equals 137.8dB of bullshit 27" wide 1x 15" loaded T60 max SPL.

Now, if you want to calculate usable maximum SPL, I recommend you use RMS power and the lowest SPL in the intended usable frequency range. That will give you data you can use in planning the needs and requirements at different venues.

There are a couple easy ways to convert power to dB. On a scientific calculator (smartphone or PC has this), simply enter the power number and press LOG, then multiply by 10. Or in a spreadsheet, =LOG(watts)*10.

Since the voltage limit for the LAB15 T60 is 60volts and the drivers nominal impedance is 6Ω, Volts x Volts ÷ Ohms = Watts... 600 Watts. 600 LOG x 10 = 27.8dB



I like to use 40Hz figures, 98dB + 27.8 (600W in dB) = 125.8dB minimum maximum usable long term SPL. That's a real number you can realistically expect to actually measure in the real world.

The reason I use the least sensitive figure for calculations is, the lest sensitive is usually the bottom of the frequency range. Once it's all EQ'd, it's likely that 40Hz is 12-15dB hotter than 125Hz, which means there will be a boost/cut spread of nearly 25dB in this case. Who cares what the sensitivity is at 100Hz when it's going to be attenuated 25dB and it's resultant peak output at that frequency is dictated by the sensitivity of the lowest, least sensitive frequency. Anyway, a little rambly there. Hopefully the point comes across.

If they have 12 of the B-2s, with max SPL of 139/136 db at let’s say 50 Hz for one cab…

Then for 12 cabs, they might get an additional 3.5 x 6 db = 21 db…?

So 139 + 21 = 160/157 db in that range? Whoa…

Yes, using traditional math and not accounting for an efficiency limit, 12 cabs is +21.58dB. But, as I mentioned above, their "max SPL" is a bogus figure and the multiple cab calculation has changed. I don't even want to venture a guess as to what the might be able to produce in the real world, but it's 100% not as advertised.

All I know is that when you stand in their sweet spot vs ours, it’s a big difference. Does that just mean they are 10, 20, 30+ decibels higher in the 50-60Hz (or lower) range? Silly question, because probably no one has been out on their dance floor, but when you compare different systems that you have experienced in your own life, do you think that is the main difference between higher and lower quality systems? Just having the right decibels levels at the right frequencies? Or is there something(s) more to it?

The system tune is monumental and can make or break the listening experience. What was it that made a difference for you. What do you feel your setup was lacking in comparison? Was it volume? Was it something else? Could be both, but a good tune will sound better than a not-so-good tune at any volume.

Can you tell me a little about how your system was tuned? Do you have any screen shots of the system's final response curve or even a target response curve? Response plots/graphs would be the best way for us to help you in regards to the tune. What did you use to tune? Open Sound Meter/SMAART? Just the auto tune in the Driverack? Just be ear?

An expertly tuned system sounds amazing.

[Bill Fitzmaurice]

If I understood Bill correctly, and Bill please correct me if I'm off base, the first 8 max width cabs of either design will scale at 6dB per doubling cab count (3dB for increased efficiency, 3dB for doubling power) and additional cabs beyond that are just 3dB per doubling of cab count for doubling system power, but no additional increase in efficiency.

When you double the cab count while maintaining the same voltage you get 6dB higher sensitivity by dint of the doubled cone displacement. That also results in increased efficiency. But you only get that full 6dB where 6dB of increased sensitivity and the associated efficiency is available. At the upper end of the spectrum you may only get 3 or 4dB. In the case of the T48 and T60 eight cabs is what it takes to get maximum sensitivity and efficiency all the way down to their respective horn cut off frequencies. It's 115dB. More cabs won't give more sensitivity, but with sufficient power you'll still get 6dB more maximum output with 16 cabs.
It's common to see the 6dB sensitivity increase per doubling of drivers or cabs used as a rule of thumb, because it's usually applied to direct radiators that start off with low sensitivity and efficiency, so they've got lots of room for increases.

[Radian]

Who does the OP intend to tune the system once it’s built? A large part of the apparent sound quality of a rig is who’s allowed to dial things in.

A single person can bring a high-dollar system to its knees just by getting the setup wrong. There’s a lot of details to get right that all add up to that kick butt sound.

Safe to say, that D&B rig has been tuned/directed by someone other than just their investors, if not a D&B authorized tech. Funktion One used to be the same way.

[Seth]

When you double the cab count while maintaining the same voltage you get 6dB higher sensitivity by dint of the doubled cone displacement. That also results in increased efficiency. But you only get that full 6dB where 6dB of increased sensitivity and the associated efficiency is available. At the upper end of the spectrum you may only get 3 or 4dB. In the case of the T48 and T60 eight cabs is what it takes to get maximum sensitivity and efficiency all the way down to their respective horn cut off frequencies. It's 115dB. More cabs won't give more sensitivity, but with sufficient power you'll still get 6dB more maximum output with 16 cabs.
It's common to see the 6dB sensitivity increase per doubling of drivers or cabs used as a rule of thumb, because it's usually applied to direct radiators that start off with low sensitivity and efficiency, so they've got lots of room for increases.

Again, a little confused. The graph below for presumably 24" wide T48's indicates eight cabs aren't yet flat to 35 or 40Hz, so I'm guessing it's eight 36" cabs that would be so. However, I also see that if the eight cabs were flat to the cutoff frequency, the sensitivity would be about 118dB, 3dB more than the 115 you stated above.



And looking at the chart below, (which also verifies that the one above is 24" cabs, based on the trace contour) it shows the higher frequencies measure nearly identical, so I'd imagine 8 36" cabs would be right at 118dB down to the cutoff frequency and also the T60. Is 118 correct, or is it in fact 115? Perhaps just a typo?



Also unclear about this part, "More cabs won't give more sensitivity, but with sufficient power you'll still get 6dB more maximum output with 16 cabs."

If 115/118dB is the Sensitivity of 8 cabs at one watt per cab, maximum SPL should be 142.8/145.8 on the limiter for the first 8, correct? And we can still get +6dB if we double the cab count to 16 cabs even though we're limited to only doubling the power of the system? Or does "sufficient power" imply more power/voltage than what we limit to? +3dB makes sense. +6dB does not make sense.

Looking at the first graph, the higher frequencies that are presumably at maximum efficiency only increase 3dB per doubling, where the low frequencies are about 6dB. Seems to affirm what you originally said. (or what I heard)

I'd really like to understand this clearly if there's anything you can add to help. Or maybe point me in the right direction with a few key words/phrases and I'll climb down a google rabbit hole on my own.

I really appreciate the shared knowledge Bill, this is one of the better audio distinctions I've been enlightened to in a ling time. Thanks! I love this stuff!

[Keryn O'Shea]

They took that as a badge of honor, and since they did it with DR280s and T60s so do I.

Excellent, that's awesome Bill!

..but why not? Let's see what a load of bullshit useless figures equates to..

Who does the OP intend to tune the system once it’s built?

I really appreciate the shared knowledge Bill, this is one of the better audio distinctions I've been enlightened to in a ling time. Thanks! I love this stuff!

Absolutely man!

[Seth]

Who does the OP intend to tune the system once it’s built? A large part of the apparent sound quality of a rig is who’s allowed to dial things in.

A single person can bring a high-dollar system to its knees just by getting the setup wrong. There’s a lot of details to get right that all add up to that kick butt sound.

Safe to say, that D&B rig has been tuned/directed by someone other than just their investors, if not a D&B authorized tech. Funktion One used to be the same way.

100%
+1

[Bill Fitzmaurice]

Yeah, I need to replace that chart, as it's not accurate. It goes back 20 years, when HornResp wasn't as sophisticated as it is now. This is 8 T48:


Again, to understand it model it. Model one cab for the base SPL, use the multiple cabs in parallel tool to see the sensitivity increase. For maximum SPL model one cab at the maximum voltage, use the multiple cabs in parallel to see the maximum SPL. Eight T60 at 60v come out to 142dB.

And we can still get +6dB if we double the cab count to 16 cabs even though we're limited to only doubling the power of the system? Or does "sufficient power" imply more power/voltage than what we limit to? +3dB makes sense. +6dB does not make sense.

That's the problem when looking at power. Don't. Look at voltage. That's why there is no line entry for power in HornResp, only voltage. The point about having enough power relates to impedance. You need sufficient power to deliver the desired voltage without exceeding the output current capability of the amps. But amps aren't rated for voltage and amperes output, they're rated for power. You need to know how much power will be required to deliver the requisite voltage and amperes. To that end there's this: https://ohmslawcalculator.com/ohms-law-calculator

[Seth]

Yeah, I need to replace that chart, as it's not accurate. It goes back 20 years, when HornResp wasn't as sophisticated as it is now. This is 8 T48:

Thank you Bill. I appreciate the clarification. What cab width is that?

[Bill Fitzmaurice]

24". Wider would fill in that low end trough.

[Levi]

Wow! Once again, look at all these responses! I got a little extra pep in my step now! Thank you everyone!!!


@Bill

Thanks for scanning the Death Star’s plans! I figured something fishy was going on… The shields are still up.. It’s a trap!!!

It’s so sneaky how they market them. With not only the peak level, but as “horn-loaded” as well. Shame, shame, shame...

And narrow bandwidth indeed! 20 - 180 Hz. Seems like they were definitely designed to have as much output as possible between 40 - 60 Hz. Chest thumping range…

It's also hilarious that, given the max 180Hz on their chart, and that 40cm/800Hz limit, that their "horn-loaded" marketing would never apply!



@Seth

Seth! Thank you so much for diving deep into this with us! Awesome! And yes, don’t worry, we definitely intend on doing everything right!!!

Point taken on the configuration, thanks! That photo is from a year when the wind was especially nasty, so we took the top ones down and just set them beside the others. Don’t worry - they were unplugged!

The tops in that photo are actually Omnis, not DR280s. And correct, no splay angle. We will definitely be building 6 x DR280s with the compression drivers for this year. We will think hard on how to safely secure them 6.5’-8’ high, too!

Efficiency math is fun! As is the law of diminishing returns. It seems that there is definitely such a thing as too much chocolate cake. Or, in this case, tubas! But 80 more?! As in eighty? No typos, right? Holy smokes! That’s a lot of tubas to get twice as loud! That said, this assumes that we have the same amount of power going into the system as we had for only 8 tubas, correct?

Yes, yes, yes. At one point we had 12 x T60s. This is a sore subject, unfortunately. The desert is not an easy environment… The journey over the last decade or so has been hard on us and the speakers both… After taking stock and testing last weekend, we are down to just 2 working T60s!

Oh man! Thank you so much for further dispelling all this maxSPL marketing hype! And thanks for all the detailed calculations! I like that usable maxSPL much more bettererer! It seems like a much more honest way of doing business… so much for that idea! Thank you for walking me through the numbers. This stuff is really cool!

And yes, Seth, thank you for the segway into tuning! We will get there!

But first...

Even though we are comparing rotten apples, I just can’t help myself. I guess it helps me put things in perspective. Let me see if I can pierce the veil on all this marketing hype!

Okay, so you pulled back the curtain on the B-2. After putting this all together, I now see the marketing bullshit says maxSPL of 139db at 50Hz. (50Hz looks like the apex of their normalized chart.) But really, in the absolute best case scenario, it’s more like 105.2db at 50Hz. Sneaky, sneaky, sneaky…

That said, the T60-LAB15 chart says about 101db at 50Hz. But, this is for just one T60. The B-2 has 2 x 18” drivers, you know, so let’s even this out a bit by adding another T60, shall we? In that case, we get another 6db for doubling the power and driver/cab, correct?

So…

101db + 6db = 107db

107db > 105.2db

Bam! How do you like them apples?!



Now, let’s finish this rotten apple 50Hz horse race, shall we?



Comparing 12 x B-2s with 16 x T60-LAB15s… Keeping things at 1w/1m…

1 x B-2… 105.2db… 12 x B-2s, add 3.5 (ish) x 3db = 10.5db… 105.2db + 10.5db = 115.7db

1 x T60-LAB15… 101db… 16 x T-60s, add 4 x 3db = 12db… 101db + 12db = 113db

Wow! In this completely impractical comparison, the obscenely expensive Death Star only beats the Alliance by a measly 3.7db! And they have 24 x 18” drivers, compared to only 16 x 15” drivers! Behold! The magic of Bill’s horn designs!!!

...But...

Who likes "almost" beating the Death Star? Ain't no movies being made about that!

If we build the 2 x LAB12 (or equivalent) vs the 1 x LAB15 version, then we add another 3db or so at 50Hz, right?

So...

113db + 3db = 116db

Now, we will not only match the Death Star… We will beat it! Blow it all up into stardust! And then party with a bunch of little furry Ewoks!

…Right?!



@Radian

Hi Radian! Thanks for joining us! Thanks for also bringing us to the tuning issue. We will get there, for sure!




My original goal in posting this topic was to discover the type and number of speakers that we should build given the situation. Thanks so much to Bill and everyone else. It seems we’ve done it… almost!

16 x T60s
6 x DR280s

But now, the big question is, which version of the T60 should we build?

Our default option is the 1xLAB15” version. That will be our least expensive option. If adding in the extra time and cost is worth it, we are open to other versions.

For output, the 2xLAB12 30” cab is a no brainer, correct? From the charts, it looks like we get an additional 3-6db between 20-200Hz.

@Bill

I noticed in the plans, you leave plenty of options on the table…

“You may build a 2x12, in cab widths between 29 and 39 inches. Response will be the same as two 1x12s each half the width of the 2x12, so it’s usually not worth the hassle of building, and moving, the larger box. The exception is if you have a large pro-touring rig and want to have 2x12s with the drivers wired in series, for 16 ohms impedance per cab, allowing the maximum number of cabs per amp channel.”

How much output is gained from going wider than 30”? For instance, 33”, 36”, and 39”?


For weight, I couldn’t find anything readily available on the forum. Does anyone have a good idea of each version, without paint? For some reason I have 185 pounds in my head for the 1xLAB15. Does that seem right? Any idea for the 1xLAB12 slim version? 120 pounds maybe? What about the big boy? 2xLAB12 version? 235 pounds?

For cost, I’m guessing 2xLAB12 would be 20-30% more expensive than 1xLAB15… Lots of variables I know, but does that seem like it’s in the ballpark?



Once this is settled, we can get to tuning!

My memory is a little foggy on the specifics of what we have done in the past. I’ll need a bit to dig up all the relevant details…

So stay… tuned!!!

[Bill Fitzmaurice]

I'd do it in 2x12, 30 inches wide, loaded with LaVoce SSF122.50L. Even eight of them should get you kicked out of Burning Man.

[Levi]

Thanks, Bill!

Sorry about the question about which width to choose. This dummy didn't look hard enough to answer his own question. After poking around, I found your chart comparing a 15" and 20" wide version of the 1xLAB12. Seems to be a 2db gain on average below 100Hz for the 20" versus the 15".

In theory, would that mean that a 2x12 chart for a 39" wide version would basically be the same curve as the 2x12 30" version, just translated 2db up?

Also, I'm guessing that building any wider than 39" for the 2x12 would not be the way to go, because the throat would too large for optimal loading... Is that correct?

I suppose I'm asking out of general curiosity than actual planning purposes. We will not go wider than 30", because we have about 90" total width to store them. So 3x30" would be just right. Unless doing 2x45" behemoths would somehow make sense?

Any reason for LaVoce vs LAB12? Cost and weight savings?

[Bill Fitzmaurice]

The LaVoce has 95% of the LAB capability at 60% of the price. If you can only have one then LAB makes sense, but with a herd not so much. Pay attention to having the holes in panel 5.

[Seth]

Efficiency math is fun! As is the law of diminishing returns. It seems that there is definitely such a thing as too much chocolate cake. Or, in this case, tubas! But 80 more?! As in eighty? No typos, right? Holy smokes! That’s a lot of tubas to get twice as loud! That said, this assumes that we have the same amount of power going into the system as we had for only 8 tubas, correct?

The perception of volume increase from one person to the next is completely subjective. I might listen and think a 12dB increase sounds twice as loud. You might listen and think an increase of 8dB sounds twice as loud. That given, it's widely accepted and assigned that a 10dB increase/decrease in volume is twice/half the perceived volume. Voltage, power, sound, sound over distance, and many other things are calculated as a logarithm, "the exponent or power to which a base must be raised to yield a given number".

According to the logarithmic math based on the first eight cabs increasing 6dB per cab count doubling (20Log) and any additional cabs at a rate of 3dB per doubling (10Log), that's correct. It would take 80 (eighty) T60's with equal voltage/power per cab to achieve a 10dB increase above 8 (eight) T60's with the same voltage/power per cab.

However, I imagine the deployment of such a mass would make the actual measurement of such a comparison supremely unrealistic. Mentioned it mostly as a mathematical novelty.

If 8 is baseline, 8 more is +3dB, another 16 (totaling 32 cabs) another +3dB (+6 total), another 32 cabs (64 total) another +3dB (+9dB total). It would take another 64 cabs to get another+3dB, but "only" takes another 17 cabs to make up that last +1dB to total +10dB and make up twice as loud as 8 cabs.

The sillyness of that number of cabs aside, what does come to light in this train of thought as a really interesting tid-bit is just how unrealistic it would be for direct radiators to match horns output potential if they're limited to a cap of half the efficiency of a horn in any number. Very interesting. Although very agreeable with the rules of thumb we've read before, that you have to have twice the number of direct radiators and twice the power to match the output potential of a horn.

Yes, yes, yes. At one point we had 12 x T60s. This is a sore subject, unfortunately. The desert is not an easy environment… The journey over the last decade or so has been hard on us and the speakers both… After taking stock and testing last weekend, we are down to just 2 working T60s!

If the cabs are properly sealed (no air leaks around the drivers, no air leaks at any of the glued joints, I can't see the environment causing issues. However, if the driver securing bolts/screws worked themselves loose causing air leaks or the speakers weren't appropriately high passed and limitted, drivers will blow without warning. Did you guys investigate any deeper than just plugging the cabs in? Take any driver chamber covers off and inspect inside at all? If so, anything interesting?

That said, the T60-LAB15 chart says about 101db at 50Hz. But, this is for just one T60. The B-2 has 2 x 18” drivers, you know, so let’s even this out a bit by adding another T60, shall we? In that case, we get another 6db for doubling the power and driver/cab, correct?

Something to be aware of is, on this site most of the charts are done at 2.83 volts. 2.83 volts is 1 watt into a nominal 8Ω load. However, LAB12 or LAB15 are nominal 6Ω and 2.83 volts into a 6Ω load is 1.3348 watts, a difference of 1.25dB.

To add to the confusion, the horn itself adds a couple ohms to the actual operating nominal impedance. Impedance is different at every frequency and can vary quite a bit. That's why we simplify and use nominal impedance, or average. It's great to have the charts on this site uniform and really it's the best way to do it. However, just be aware when making power to power sensitivity comparisons of one cab to another at a certain voltage, that may be variations in driver or overall cab impedance that may need correction to make a true 1:1 comparison. Ultimately, in practice using the 2.83V standard is good enough and represents what would happen when plugging the cab into an amplifier then swapping for another cab.

The reason for pointing this all out is, if you were to compare the response graph of the LaVoce cab Bill recommended, it's sensitivity will likely be lower throughout the whole graph, mainly because the difference in impedance of the drivers. Same goes for making comparisons to any other 8Ω cab. How you relate to these differences, how you value the results, and what point of view you choose is completely up to you. Just be aware the distinction exists. If you prefer to value voltage to voltage response or power to power response is up to you. I prefer power to power as it just makes more sense to me in comparing one cab to another. But, someone is more focused on the results of connecting multiple cabs to a specific amplifier, the voltage based graphs will be more useful. In the end, it's only important until you make your cab selection. After that, I'm only concerned with the general shape of the response graph.

Anyway, here's the results of 2.83V/1.3348W in red, 2.45V/1W in blue

I look at this graph and see a 50Hz sensitivity of 99dB. Although, there's nothing wrong about seeing 101, as long as you're aware of the difference and how it impacts what you're focused on. In the comparison you made below, I'd personally use the 1W/1M figure instead.

So…

101db + 6db = 107db

107db > 105.2db

Bam! How do you like them apples?!



Now, let’s finish this rotten apple 50Hz horse race, shall we?



Comparing 12 x B-2s with 16 x T60-LAB15s… Keeping things at 1w/1m…

1 x B-2… 105.2db… 12 x B-2s, add 3.5 (ish) x 3db = 10.5db… 105.2db + 10.5db = 115.7db

1 x T60-LAB15… 101db… 16 x T-60s, add 4 x 3db = 12db… 101db + 12db = 113db

Wow! In this completely impractical comparison, the obscenely expensive Death Star only beats the Alliance by a measly 3.7db! And they have 24 x 18” drivers, compared to only 16 x 15” drivers! Behold! The magic of Bill’s horn designs!!!

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.

If we build the 2 x LAB12 (or equivalent) vs the 1 x LAB15 version, then we add another 3db or so at 50Hz, right?

Again, to me it's important to use 1W/1M figures based on driver impedance and not accounting for impedance added by the cab. A 2x LAB12 cab is 3Ω. The response chart shown on the T60 sales/information page is done at 2.0 volts (1.33W, 1.24dB over 1W), although the chart tool in this forum appears to be done at 2.83V/2.67W which is 4.27dB more than 1 watt.

Adjusting both, the 27" LAB15 T60 and 30" 2x LAB12 T60 1W/1M traces indicate about 1dB greater sensitivity at 50Hz. Although, about 2dB from 25-30Hz, which is good even though it's outside the frequency range I'd primarily focus on.

Our default option is the 1xLAB15” version. That will be our least expensive option. If adding in the extra time and cost is worth it, we are open to other versions.

For output, the 2xLAB12 30” cab is a no brainer, correct? From the charts, it looks like we get an additional 3-6db between 20-200Hz.

Here's a 30" 2x LAB12 and 27" 1x LAB15 adjusted to represent response at max voltage/power. Looks like the 2x12 has a solid 2-3dB advantage in max potential SPL.

For weight... ...I have 185 pounds in my head for the 1xLAB15. Does that seem right?

That seems like it would be reasonably close.

Once this is settled, we can get to tuning!

We'll also get into the importance and impact of equal loudness contours.

Out of curiosity, is all the Star Wars talk due to a genuine infatuation with the movie series or is it just because Bill has Yoda as his avatar?