What's to chat about?

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Seth
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Re: What's to chat about?

#1036 Post by Seth » Sun Aug 29, 2021 2:26 am

Bill Fitzmaurice wrote:
Sat Aug 28, 2021 7:27 am
You can't consider any one spec for maximum voltage. You have to consider all of them, and then model the driver in HornResp to see their combined result. Sometimes the overall limiting factor is Pe, sometimes it's xmax, sometimes it's xlim, and sometimes it's none of them.
I figured that may be the case. Seems like there's always at least 3 factors, with things in general, that can have different values and equate to similar results. Perhaps I'll get around to really learning some of this T/S stuff sometime, as well as gain some proficiency in horn theory and fiddling with Hornresp.

In the meantime, thanks for shedding a little light on my curiosities Bill. :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: What's to chat about?

#1037 Post by Seth » Thu Sep 02, 2021 10:22 am

Seth wrote:
Fri Aug 27, 2021 9:28 pm
By show of hands ✋, how many of you guys actually have an Excel spreadsheet with audio formulas too?
37602
Tom Smit wrote:
Fri Aug 27, 2021 9:51 pm
Handsdown.
Grant Bunter wrote:
Sat Aug 28, 2021 1:20 am
No Seth,
It's all in my head...
himhimself wrote:
Sat Aug 28, 2021 7:01 am
✋

:oops:
Well Brent, after more than 150 thread "views"... I guess it's just me and you.

The other day I was just jotting some equation notes in mine, then figured I'd go ahead and make quick, simple, working "calculators" to go along with the notes... That was a bit of a mistake; I led myself right down a rabbit hole and the next thing I know I'm creating a multifaceted calculator with dropdown menu's, auto-populating conditional values, along with color changing boxes and warning text when values are out of range. :roll:

Here's one of the longer cell formulas. LOL It auto populates one cell (Sensitivity) based on the values of two other cells (Cab and Driver)

=IF(AND(O52="T24",P52="S2010"),91,IF(AND(O52="T24",P52="BP102"),88,IF(AND(O52="T24",P52="KappaPro10LF"),88,IF(AND(O52="T24",P52="KL3010LF"),91,IF(AND(O52="T30",P52="S2010"),91.5,IF(AND(O52="T30",P52="BP102"),90,IF(AND(O52="T30",P52="KappaPro10LF"),90,IF(AND(O52="T30",P52="KL3010LF"),90,IF(AND(O52="T30",P52="S2012"),90,IF(AND(O52="T30",P52="Delta12LFA"),93,IF(AND(O52="T30",P52="3012LF"),93,IF(AND(O52="T30",P52="LAB12"),95.75,IF(AND(O52="T30",P52="12NLW9300"),92,IF(AND(O52="T45",P52="S2010"),91.5,IF(AND(O52="T45",P52="BP102"),90,IF(AND(O52="T45",P52="KappaPro10LF"),93,IF(AND(O52="T45",P52="KL3010LF"),90,IF(AND(O52="T45",P52="S2012"),90,IF(AND(O52="T45",P52="Delta12LFA"),93,IF(AND(O52="T45",P52="3012LF"),93,IF(AND(O52="T45",P52="LAB12"),95.75,IF(AND(O52="T45",P52="12NLW9300"),92,IF(AND(O52="T39",P52="12NLW9300"),101.5,IF(AND(O52="T39",P52="LAB12"),96.75,IF(AND(O52="T39",P52="3012LF"),101,IF(AND(O52="T39",P52="Delta12LFA"),95,IF(AND(O52="T39",P52="S2012"),98,IF(AND(O52="T39",P52="KL3010LF"),95,IF(AND(O52="T39",P52="KappaPro10LF"),95,IF(AND(O52="T39",P52="BP102"),95,IF(AND(O52="T39",P52="S2010"),97.5,IF(AND(O52="T60",P52="LAB15"),93.75,IF(AND(O52="T60",P52="LAB12x2"),92.75,IF(AND(O52="T60",P52="LAB12"),91.75,IF(AND(O52="T48",P52="15NLW9300"),103,IF(AND(O52="T48",P52="LAB15"),100.75,IF(AND(O52="T48",P52="3015LF"),102,IF(AND(O52="T48",P52="KappaPro15LF"),101,IF(AND(O52="T48",P52="Kappa15LF"),101,IF(AND(O52="T48",P52="12NLW9300"),99,IF(AND(O52="T48",P52="LAB12"),96.75,IF(AND(O52="T48",P52="3012LF"),98,IF(AND(O52="T48",P52="Delta12LFA"),98,IF(AND(O52="T48",P52="S2012"),98,IF(AND(O52="SRX728S",P52="2x18"),96,"Driver")))))))))))))))))))))))))))))))))))))))))))))




I've got to imagine Mr. Chris Allen has an audio spreadsheet or two too.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: What's to chat about?

#1038 Post by Seth » Thu Sep 02, 2021 12:56 pm

Pic for context. It's still a work in progress. The highpass frequency figures, sensitivity at those values, and the HZ values still need to be set up to work properly. The sensitivity indicated for these two cabs is actually at 40Hz for both.
Screenshot (117).png
The red box indicates the value is beyond the limits of the combination. The "V-Plate" option adds 3dB to the sensitivity, but the function disabled for T45, T60, and SRX728S cabs... even if it's says "Y", it's not factored in.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

himhimself
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Re: What's to chat about?

#1039 Post by himhimself » Thu Sep 02, 2021 5:46 pm

Lovely Seth! Team Geeks United?
2xT30 (20", 3012LF)
2xT30 (21", 3012LF)
4xOtop J-array (Beta12, melded/straight piezos)
Truck Tuba (MCM)
Next up: 2xJack12 or family of table tubas

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Re: What's to chat about?

#1040 Post by Grant Bunter » Thu Sep 02, 2021 7:09 pm

Seth wrote:
Sat Aug 21, 2021 12:19 pm
Calculations note:

The 1.122 constant used in the Voltage/dB equation also works with comparing Vd and/or Xmax as well.

In another thread we were comparing drivers
Seth wrote:
Wed Aug 11, 2021 10:01 pm
Vd... based on stated xmax.
3012LF - 496cc
12XL1200 - 584cc
LAB12 - 659cc
If we want to know how much Vd we'd need to make a certain gain, or how much of an increase/decrease to expect from one driver to another, just adjust the dB value...

(1.122^dB) x initial Xmax or Vd value = final value

(1.122^1.42dB)*496cc=584cc
(1.122^2.47dB)*496cc=659cc

3012LF - 496cc - Baseline 0dB
12XL1200 - 584cc - +1.42dB
LAB12 - 659cc - +2.47dB

Or say we want to see what the loss would be going to a Delta 12LFA...

(1.122^-6.19dB)*496= 243cc

Delta 12LFA - 243cc - -6.19dB compared to a 3012LF
I've read, and re read this a number of times, and I've come to the conclusion there are irregularities in the math.
No, wait up, not a problem with the math, as the math is spot on, but doesn't wash with all the information available.
And I'm wondering if those irregularities are due to at least one other factor which hasn't been been factored in.

How did this thought arise?
Well, it's the discrepancy between the math result and other information.

The lab12, if solely based on Vd, should win hands down in dB.
Your equation comes up with a figure approaching +3dB over the 3012lf, suggesting it does.

Yet, it's often enough been said here in the forum that the 3012lf and the lab12 in, say a T39, have output "much the same", or perhaps "there is a very slight advantage to the Lab 12 loaded cab".
ie, not statistically significant to the point it can be discerned without measuring.
In other words, by ear, "Not noticeably louder" or less than +3dB, but also "no notable difference", or maybe +1dB louder.
To be fair, discrepancy will often occur when there is a comparison of subjective to objective results.
What's different in these 2 drivers for their displacement voltage limit?
Nominal impedance is the most obvious.

Then off to the T39 SPL charts.
Where it tells us the S2010 has a voltage displacement limit of 28V and the 3012lf 56V meaning we can add an extra +6dB if using the 3012lf in terms of max output (compared to the S2010), and that it "would take 2 x S2010 loaded cabs to = 1 x 3012lf loaded cab".
If Vd is the criteria, then should we perhaps expect that the 3012lf also has double the Vd of the S2010?
It turns out the 3012lf has roughly 3.5 times the Vd of the S2010, yet has double the voltage displacement limit.

Since Nominal impedance is the same for these two drivers, is that then still a factor?
Yes.

Similarly, the BP102 Vd is less than half the 3012lf. Yet it's voltage displacement limit isn't half or less.
Nominal impedance is the same.
And I've said before, without measuring, (I know you want me to lol), I "feel" 2 x 28" 3012lf loaded T39's have at least the same as, or greater output, than 4 x 20" BP102 loaded T39's.

The one figure that disturbs me the most though is the comparison of the 12LFA and the 3012LF.
You get a result of -6.xxdB for the 12LFA.
Yet it's voltage displacement limit isn't the same as the S2010 (28V), it's voltage displacement limit is the same as the BP102 (35V), in a T39, but it's Vd is greater than either of the other 2 drivers, yet less than half the 3012LF.
A calculation of -6.xxdB should mean, if nothing else, a voltage displacement limit half that of the 3012LF (or the same as the S2010), but that's not the case.

Bill's response since has already alluded to the fact that in any given situation, the factors determining voltage displacement limit vary, and can only be calculated in conjunction with simming in Hornsresp.
IIRC, the most important factors are impedance and Xmax.

Does that mean basing calculations on dB output shouldn't solely rely on Vd?
I think so.
When I first got here, it was explained to me that Vd is a valuable tool when comparing drivers.
And when I re read what I've written above, it seems that the correlation of Vd and output in dB due to displacement voltage limiting doesn't particularly match.

This makes me wonder if a more valuable tool would be Displacement voltage limiting with X driver and consequent output calculator, rather than Vd to dB, because voltage displacement limiting has already taken into consideration a host of other factors.

Apologies for the essay.
It wouldn't surprise me for more than a second or so that I'm totally off the mark with this line of thinking :wall:
Last edited by Grant Bunter on Thu Sep 02, 2021 9:55 pm, edited 1 time in total.
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Bill Fitzmaurice
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Re: What's to chat about?

#1041 Post by Bill Fitzmaurice » Thu Sep 02, 2021 8:46 pm

Grant Bunter wrote:
Thu Sep 02, 2021 7:09 pm
Bill's response since has already alluded to the fact that in any given situation, the factors determining voltage displacement limit vary, and can only be calculated in conjunction with simming in Hornsresp.
+1. We're not talking about simple addition here, we're talking about calculus. It's made relatively easy thanks to HornResp. If you were to see all the calculations involved it would make your head spin. For instance this from Olson's Elements of Acoustical Engineering: The acoustical power output, in watts, of a horn loudspeaker in which the diaphragm is terminated in an acoustical resistance is P = pc(27rJ)2d2An2/2AH 10(-7).

And that's just for starters.

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Re: What's to chat about?

#1042 Post by Seth » Tue Sep 07, 2021 5:12 pm

Grant Bunter wrote:
Thu Sep 02, 2021 7:09 pm
...Apologies for the essay...
I sure wouldn't apologize for that post. It's fantastic! I think you've identified a lot of really good points, touched on some curiosities and inconsistencies I've had too, and brought to light some things I hadn't even considered. I'm away on holiday for the rest of the week and have some pretty important stuff demanding my time and attention early next week too. I look forward to responding to your post with the attention such a masterpiece deserves.

But, for the time being... thanks for the good read Grant. I enjoyed it. :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: What's to chat about?

#1043 Post by Rich4349 » Fri Sep 10, 2021 10:01 am

So Bill, how many unreleased designs do you have floating around your drafting software? Maybe you've held off on some due to overly complex designs that would overwhelm the average hobbyist and lead to too many underperforming builds?
2 DR250s, 2 27" Lab15 T-60s, 2 30" Neo Titan 39s, 1 Autotuba...and looking for more!

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Re: What's to chat about?

#1044 Post by Bill Fitzmaurice » Fri Sep 10, 2021 10:07 am

None. If it's too difficult for anyone to build there's no point to it.

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Re: What's to chat about?

#1045 Post by Rich4349 » Fri Sep 10, 2021 10:30 am

I didn't mean too difficult for ANYONE, just most. Ok, disregard!
2 DR250s, 2 27" Lab15 T-60s, 2 30" Neo Titan 39s, 1 Autotuba...and looking for more!

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Re: What's to chat about?

#1046 Post by Seth » Sat Sep 11, 2021 6:41 pm

Grant Bunter wrote:
Thu Sep 02, 2021 7:09 pm
...The lab12, if solely based on Vd, should win hands down in dB.
Your equation comes up with a figure approaching +3dB over the 3012lf, suggesting it does.

Yet, it's often enough been said here in the forum that the 3012lf and the lab12 in, say a T39, have output "much the same", or perhaps "there is a very slight advantage to the Lab 12 loaded cab".
ie, not statistically significant to the point it can be discerned without measuring.
In other words, by ear, "Not noticeably louder" or less than +3dB, but also "no notable difference", or maybe +1dB louder.
To be fair, discrepancy will often occur when there is a comparison of subjective to objective results.
What's different in these 2 drivers for their displacement voltage limit?
Nominal impedance is the most obvious.
That's a great point. I don't disagree. I'd be curious to know what the actual measured difference would be and which of the two sources is more accurate; the loose math or the "often said".

Using power to calculate the potential difference equates to +1.2dB in favor of the LAB12 and using displacement indicates 2.47dB. So, even in the math, there are discrepancies that don't add up as well.

Then off to the T39 SPL charts.
Where it tells us the S2010 has a voltage displacement limit of 28V and the 3012lf 56V meaning we can add an extra +6dB if using the 3012lf in terms of max output (compared to the S2010), and that it "would take 2 x S2010 loaded cabs to = 1 x 3012lf loaded cab".
If Vd is the criteria, then should we perhaps expect that the 3012lf also has double the Vd of the S2010?
It turns out the 3012lf has roughly 3.5 times the Vd of the S2010, yet has double the voltage displacement limit.
Another good thought. I assume you're referring to the SPL Charts and the information provided there. I also find that a little perplexing. However, not from the standpoint of the math equations. But, more so what you said (and it says). By the voltage limits and resultant power, the 20dB and 26dB are spot on. But, as you've pointed out, two S2010's have 280cc Vd and a single 3012LF has 496cc Vd, which equates to a +5dB advantage with a single 3012LF over two S2010's.

Is it that one's voltage limit is RMS power and the other is displacement limited? Is it that the S2010 is more efficient in some way, creating more from less? Is it that one or the other, or both methods of calculating peak output aren't 100% accurate and are more of an educated guess as to what the peak output will actually be?


Similarly, the BP102 Vd is less than half the 3012lf. Yet it's voltage displacement limit isn't half or less.
Nominal impedance is the same.
The voltage wouldn't be half. But, I get your point. Without looking up the voltage limits and just using the advertised RMS power figures, the 3012LF is 2.25 times what the BP102 is, and the Vd is a very similar figure at 2.39 times the BP102's Vd. So, in this particular light, the figures are similar. Not sure if that's a handy coincidence or not.

And I've said before, without measuring, (I know you want me to lol), I "feel" 2 x 28" 3012lf loaded T39's have at least the same as, or greater output, than 4 x 20" BP102 loaded T39's.
I SO want you to measure some time! When I get my next T39's together, I plan to test two 3012LF loaded cabs against 4 cabs loaded with Delta12LFA's and/or S2012's. I'm super curious what the real world results will be. I have all the drivers (sans one S2012). Just a matter of screwing them in and seeing what the results are.
The one figure that disturbs me the most though is the comparison of the 12LFA and the 3012LF.
You get a result of -6.xxdB for the 12LFA.
Yet it's voltage displacement limit isn't the same as the S2010 (28V), it's voltage displacement limit is the same as the BP102 (35V), in a T39, but it's Vd is greater than either of the other 2 drivers, yet less than half the 3012LF.
A calculation of -6.xxdB should mean, if nothing else, a voltage displacement limit half that of the 3012LF (or the same as the S2010), but that's not the case.
I agree. Another perplexing set of values, indeed. Luckily, I'll be testing that exact scenario.
Bill's response since has already alluded to the fact that in any given situation, the factors determining voltage displacement limit vary, and can only be calculated in conjunction with simming in Hornsresp.
IIRC, the most important factors are impedance and Xmax.

Does that mean basing calculations on dB output shouldn't solely rely on Vd?
I think so.
When I first got here, it was explained to me that Vd is a valuable tool when comparing drivers.
And when I re read what I've written above, it seems that the correlation of Vd and output in dB due to displacement voltage limiting doesn't particularly match.

This makes me wonder if a more valuable tool would be Displacement voltage limiting with X driver and consequent output calculator, rather than Vd to dB, because voltage displacement limiting has already taken into consideration a host of other factors.
I'm thinking it's all the T/S parameters that create varying results between drivers that makes it unrealistic to expect precise predictions with basic calculations that only rely on one or two variables.

So, does that mean it's pointless to calculate and compare? Could be. But, I enjoy it. It's just the way my mind seems to tick.
Apologies for the essay.
It wouldn't surprise me for more than a second or so that I'm totally off the mark with this line of thinking :wall:
Again, I quite enjoyed the read Grant. And it's nice to see others putting some thought into this stuff and taking the time to bring it to the table for discussion.

And, I'm certainly not the authority, but from where I'm sitting, you're pretty well right on the mark in your line of thinking :thumbsup:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Re: What's to chat about?

#1047 Post by Grant Bunter » Sat Sep 11, 2021 9:00 pm

I think, when it comes to the lab12 and the 3012lf in particular, as per all the discussion above, "loose math" V "often said" suggests that the results vary enough that they are of significance.

Maybe the reason some wish to disagree with "often said" is they either:
Don't know what "by ear" measurements mean.
Believe the definitions don't apply to them.

To make this a little clearer.
When I say "by ear" what I mean is;

Hardly noticeable = 1 and at a stretch 2 dB. Science says most people can't pick a 1dB increase, but some say they can.
Maybe that is true, as we can train our brains to pick frequency, so why not dB.
Personally, I can't categorically say "the volume has gone up(or down) by 1dB", but I'm not interested in that level of change anyway.
But I may sense there has been a change in output.

Noticeable= around a 3dB change, not less than 2.5dB change.

Twice (or half) as loud = 10dB change.

My issue with the lab12 v 3012lf "discussion" (or any driver X vs driver Y discussion) is when people will use the "extra output" of the lab12 as a decision to go that route, but they are only going to build 2 cabs, ever.
Price is similar, weight immediately cancels out the lab12 for me, but each to their own. So, it's about trying to squeeze every last drop out a cab in terms of output, rather than saying "If I need to I will build more".
Or, "I will alter my design choice to one that can be V plated, add a V plate, and get free output greater than that provided by driver choice, at the cost of a third of a sheet of ply".
Or, "I will wall or corner load whenever I can for greater free output, even though it looks so different".

And I think this is the ducks guts of why it's often said there may be a slight advantage to the lab 12. In measurement, it doesn't end up being of reasonable statistical significance, and by ear, the result is similar.

So, in this case, the designer says as much, and we by default should defer to that.

It's absolutely the TS parameters! But which ones when????? That's the trick.

Ultimately, we all want some sort of "simple" chart that compares the driver choice, and the resulting output per cab based on that choice, perhaps with a rough cost comparison thrown in, so we can do a bang for buck.
It's maybe 1 in 10 people who will want to know the ins and outs and the why's.
I get that for you Seth.
For me, it's just taking it beyond where I need to be with it. I do want to understand, but don't have the need to explore new to me avenues...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Re: What's to chat about?

#1048 Post by Seth » Sun Sep 12, 2021 12:23 pm

Grant Bunter wrote:
Sat Sep 11, 2021 9:00 pm
...Maybe the reason some wish to disagree with "often said" is they either:
Don't know what "by ear" measurements mean.
Believe the definitions don't apply to them.
Two very good possibilities. Among other possibilities, it could also be that some don't trust the value of what may occur to be an unsubstantiated rumor or lore passed on by word of mouth. And it may not always be disagreeance, so much as it may be a questioning of validity.
To make this a little clearer.
When I say "by ear" what I mean is;

Hardly noticeable = 1 and at a stretch 2 dB. Science says most people can't pick a 1dB increase, but some say they can.
Maybe that is true, as we can train our brains to pick frequency, so why not dB.
Personally, I can't categorically say "the volume has gone up(or down) by 1dB", but I'm not interested in that level of change anyway.
But I may sense there has been a change in output.

Noticeable= around a 3dB change, not less than 2.5dB change.

Twice (or half) as loud = 10dB change.
I can sense a 1dB change in a test tone in and A/B test with my earbuds. But, among ambient noise and a music source, I'm not so sure I'd be able to tell you if/when a music track in a room or outdoors was changed by 1dB. I tend to doubt I'd be able to call out a 1dB change in that situation with any reasonable consistency and repeatability, if at all. So, I can definitely see both sides of the can/can't hear 1dB change conversation.
My issue with the lab12 v 3012lf "discussion" (or any driver X vs driver Y discussion) is when people will use the "extra output" of the lab12 as a decision to go that route, but they are only going to build 2 cabs, ever.
Price is similar, weight immediately cancels out the lab12 for me, but each to their own. So, it's about trying to squeeze every last drop out a cab in terms of output, rather than saying "If I need to I will build more".
Or, "I will alter my design choice to one that can be V plated, add a V plate, and get free output greater than that provided by driver choice, at the cost of a third of a sheet of ply".
Or, "I will wall or corner load whenever I can for greater free output, even though it looks so different".
I see your point. But, it may be helpful to realize most men are the "go big or go home" type until some experience and/or knowledge is gained and they can make choices with wisdom instead of instinct. Even having some experience and some knowledge, I personally find my mind trying to maximize the results of my projects, just to make it as cool as it possibly can be. So, I find that I understand the desire for a builder to choose the driver with the most Vd (or more typically, the most power handing) and have little issue with people wanting to choose them. But, I do like to put forth what I think I know about the situation in an effort to educate... knowing full well most of what I say will fall on def ears and only be validated through the users experience.
And I think this is the ducks guts of why it's often said there may be a slight advantage to the lab 12. In measurement, it doesn't end up being of reasonable statistical significance, and by ear, the result is similar.

So, in this case, the designer says as much, and we by default should defer to that.
So, here's something that I frequently overlook (and maybe some of you guys do it too) when making driver comparisons, which is in complete support of your position on the 3012LF/LAB12 debate...

I don't always remember to take into account that different drivers have different response plots and sensitivities and in the case of the LAB12 vs. 3012LF in a T39, it's a significant difference favoring the 3012LF.

There aren't files available to put them up in an SPL chart, but looking at these two plots it's easy to see the 3012LF has the upper hand in the meat and potatoes of the bottom end...

Image
Image

To start off, the responses shown are with 2.83v. So, the 6ohm LAB12 plot is 1.25dB above where it would be if tested at 2.45v/1 watt. Even with that slight "handicap" (it's not really a handicap if you base your other calcs on volts) to the 3012LF, the 3012LF has considerably more output from 40-90Hz. +3dB at 45HZ, +4dB at 50Hz, 5dB at 60Hz, 3-4ish dB at 70Hz... That's a HUGE advantage in favor of the 3012LF in this specific cab. This indicates the 3012LF will do what the LAB12 will do, but on half or less than half or the required power in this frequency range. And, given the voltage limits, I suspect the 3012LF will have greater output in this frequency range, even though the LAB12 has more displacement capability.

If we use the voltage calculation to identify max output at those frequencies:
45Hz - LAB12 124dB, 3012LF 127dB
50Hz - LAB12 124dB, 3012LF 128dB
60Hz - LAB12 125dB , 3012LF 130dB
70Hz - LAB12 127dB, 3012LF 131dB

Honestly, in a T39, in spite of it's greater Vd, it appears the LAB12 is actually at a sizeable disadvantage! I can't think of any reason to choose the LAB for this particular design.

Apparently Vd isn't always the king. But still, I understand the propensity of a builder to wanna choose it. The spec we're told to look for (Vd) is greater and the spec the market has engrained in consumers as important (watts) is also greater.

Which makes me wonder a little bit about that poor lowly S2010 that got fazed out of the plans. But, that's a different conversation.

It's absolutely the TS parameters! But which ones when????? That's the trick.
I can't tell you how much I wish I knew the answer to that. Perhaps in time. And perhaps not.
Ultimately, we all want some sort of "simple" chart that compares the driver choice, and the resulting output per cab based on that choice, perhaps with a rough cost comparison thrown in, so we can do a bang for buck.
The charts function in the forum here is a pretty good tool to display just that. However, having the data for every driver in every width of every cab design is a really really really tall order.
It's maybe 1 in 10 people who will want to know the ins and outs and the why's.
I get that for you Seth.
For me, it's just taking it beyond where I need to be with it. I do want to understand, but don't have the need to explore new to me avenues...
Yup yup. I've picked up on that. Some just want to know what works and go from there. And some want to also know how it works and why. Two different trains to the same destination; one express, one scenic.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Bruce Weldy
Posts: 7659
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: What's to chat about?

#1049 Post by Bruce Weldy » Sun Sep 12, 2021 12:40 pm

Seth wrote:
Sun Sep 12, 2021 12:23 pm

I can sense a 1dB change in a test tone in and A/B test with my earbuds.
Unless you are having someone else make the 1db change and you are signaling when you hear it, it's not really a valid test. If you try to test yourself - your belief that you hear the difference is tainted by the fact that your brain is expecting a change based on your actions.

Now, you may indeed be able to hear a 1db change, but it's really hard to quantify without blind testing.

For me, 1-2db means nothing as far as output between the Lab and the 3012LF......I'm never going to run either one to the full voltage available.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Seth
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Location: Sacramento, California, USA
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Re: What's to chat about?

#1050 Post by Seth » Sun Sep 12, 2021 1:35 pm

Bruce Weldy wrote:
Sun Sep 12, 2021 12:40 pm
Seth wrote:
Sun Sep 12, 2021 12:23 pm

I can sense a 1dB change in a test tone in and A/B test with my earbuds.
Now, you may indeed be able to hear a 1db change, but it's really hard to quantify without blind testing.
Try it out for yourself Blind Tests at audiocheck.net

I recommend using earphones/ear buds.

What was the minimum change you were able to repeatably identify?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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