It IS true when taken in the context that I made it. In fact, in the statement itself I said "THE horn", not "A horn", so the context I was using it in should have been plainly obvious - I was referring to trying to use HornResp sim its impact in the TH115. You cannt do that using the method you suggested because the TH115 is not a single-expansion TH.
I agree. And as you mention, increased path length and the stiffness the "V" adds in the throat are beneficial aspects of the layout.
Tom Danley called the TH-115 S1 volume (larger than S2) a "stub".
A "stub" is used on the TH-115, 118, 812, DTS 10 (and perhaps others I have not seen layouts of) so it is not unique to just one design.
Art
Results of a quick sim in HornResp suggest to me that adding a "stub" @ S1 would do the exact opposite of adding "cone compensation" @ S2, i.e. drop Fb slightly but deepen the first out of band notch, if all else is left the same. Hmm...
So in other words, TD DID take into consideration the impact of the volume in front of the driver's cone in his design, because if he did not, that "cross-sectional area" that you are referring to would have to be zero in the sim 😉.
To me, what TD did was pretty simple - took unused volume from the bend above (where people normally put in corner reflectors), added it to the first section of the horn, then correspondingly decreased the volume in the center of that section by adjusting the panels as pictured. Maybe his primary purpose was to increase the path length for the horn (on both sides of the bend), but the only way what he did would work is if the volume of air in the driver's cone was taken into consideration when he was planning the layout.
Of course he took it into account, it's part of the horn flare. I'm just suggesting that there were other reasons for this unique layout, not "cone correction".
Maybe there's some confusion about what constitutes a "throat chamber" and what's just part of the horn flare. Technically, if you have enough segments you can simulate everything as part of the flare, including the throat chamber. Either way, it's just an expansion in that part of the flare if there is a chamber, in this particular case the csa is reduced as the flare travels by the cone, so no chamber.
As weltersys mentioned (and I mentioned earlier either in this thread or the other one) Danley uses stubs (increased csa at S1) in a bunch of his horns, this is very different than "cone correction". Since he uses this pinch at S2 in a few designs and he's NEVER used "cone correction" in ANY horn (except what has been IMO incorrectly labelled as "cone correction in the 115/118) it doesn't make much sense to say that "cone correction" is DSL's secret ingredient. It would make more sense to say that the pinch at S2 (regardless of whether there's a cone at S2 or not) might be his secret ingredient, but even that is a stretch because AFAIK only a small percentage of his horns use the S2 pinch.
Maybe there's some confusion about what constitutes a "throat chamber" and what's just part of the horn flare. Technically, if you have enough segments you can simulate everything as part of the flare, including the throat chamber. Either way, it's just an expansion in that part of the flare if there is a chamber, in this particular case the csa is reduced as the flare travels by the cone, so no chamber.
As weltersys mentioned (and I mentioned earlier either in this thread or the other one) Danley uses stubs (increased csa at S1) in a bunch of his horns, this is very different than "cone correction". Since he uses this pinch at S2 in a few designs and he's NEVER used "cone correction" in ANY horn (except what has been IMO incorrectly labelled as "cone correction in the 115/118) it doesn't make much sense to say that "cone correction" is DSL's secret ingredient. It would make more sense to say that the pinch at S2 (regardless of whether there's a cone at S2 or not) might be his secret ingredient, but even that is a stretch because AFAIK only a small percentage of his horns use the S2 pinch.
"Cone correction", as it's being used here, is simply the taking into account the volume of air in the driver's cone in the design of the TH's layout. So you can't say that TD did not take "cone correction" into consideration and at the same time argue that he took that volume of air into account. That doesn't make sense.
The purpose of this thread I started was just to quantify what happens when that's actually done in a TH that did not feature it in the first place, to see if the effect can be sim'd in HornResp. As it is, the effect is a small one, and as such addressing it does not have to be a feature of *every* TH design, or even most of them, only those where it helps to achieve a particular design goal, as is apparently the case with the TH115/8 designs - the "design goal" apparently being to increase the horn's path lenth.
The term "cone compensation" will be hereafter abolished and "pinched" S2 will be trade marked by ME!
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Ummm... ALL designs are supposed to take into account the volume of air in the driver's cone (if the cone is internal in the design). It was never acceptable to ignore the volume of air in the cone. Accurately plotting out the horn flare has nothing to do with "cone correction". Just because this specific design uses the air in the cone as part of the horn flare, this has nothing at all to do with "cone correction".
"Cone correction" has a very specific meaning and use, it's been described and talked about here on this forum in great depth. It's placing blockages or restrictions in the horn path at S2 to attempt to make the flare expansion more even, in other words to specifically negate the extra volume that's usually added to the flare at S2 due to the cone. The (completely subjective) advantages have been said to be higher power handling, less distortion and stronger low bass performance. When you say the words "cone compression" on this forum, those words have a very specific meaning.
This is NOT what Danley was thinking about or doing in the 115/118 or any other design, so it's not "cone correction" even if it does vaguely resemble what some diy'ers on this forum call "cone correction".
This is all just semantics and you may wonder why I argue semantics. I will tell you. It's simply because there's no proof that "cone correction" does anything at all other than what Hornresp says it will do, and this concept has been so played out on this forum that it's like an urban legend, something people believe with no rational evidence. People are going as far as saying "cone correction" is DSL's "secret ingredient". It's all getting way overblown. There's still no proof that it does ANYTHING and DSL does not use "cone correction" in any way.
There have been many designs posted here that did not take it into consideration, including the first version of the SS15 and the recent "Need some advice... TH with a 15" thread, and no-one flagged them as unacceptable. Except you, of course. And only here all of a sudden. Usually you seem to be quick to jump on people when they dare post something that does not agree with your POV about how things should be done. What's up - did you miss those threads?
In other words, exactly what I said, using much more words to do so. Good grief man.
...and now you presume to know what Danley was thinking!
Oh, and while we're on the subject of the SS15, have a look at posts #1499, #1507,#1564 and #1587 in that thread. Let me know if you see anything that looks a bit familiar 😉.
http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge-150.html#post3028139
Finally, I think you are confusing the attributing of subjective and perhaps questionable attributes about a process with the process itself, the process here being cone correction/compensation. That's a bit like suggesting that because some people think that cars can fly, cars are not useful and should not be driven. The fact is that people can and do drive cars for other, perfectly valid, reasons.
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Did you miss me saying that accurate sims match measurements about 6000 times in the last few years?
I fully realize some people don't bother filling in Vtc and Atc, in fact sometimes I don't bother myself if I'm just playing around. It doesn't make a HUGE difference. But if you want an accurate sim, yes you have to ALWAYS account for the volume of air in the cone. Accounting for this volume that IS inside the enclosure and NEEDS to be accounted for in an accurate sim has NOTHING to do with cone correction, which is a new(ish) term and concept for some pretty wild subjective ideas.
The reason I'm making a big deal of this is because around here some ideas seem to be infectious, almost contageous, and spread into common mythology very quickly. I was really vocal about the idea that DSL's boundary coherent designs created a vortex of air around the mouth which created a virtual segment outside the horn mouth made of swirling air. Some ideas are just really dumb and need to be squashed. The idea that "cone correction" does anything other than what Hornresp suggests it will do isn't quite that dumb, but it needs more proof before any of these subjective advatages it provide before people consider it true. A lot of people are already convinced it's doing crazy things like increasing output at Fb, increasing power handling, and all kinds of crazy stuff.
Not even close to the same thing you said. You said "cone correction" is simply saying taking into account the volume of air in the driver. That has nothing at all to do with cone correction.
Seriously? When the guy has NEVER used "cone correction" in a design, suggesting it wasn't used in THIS particular design isn't that much of a stretch. Suggesting it WAS used in this particular design is the presumptuous opinion.
I think you are mistaking a specific process for something that DSL did ONCE that looks vaguely like something a small group of diy'ers do (the S2 pinch was used a few times but only resembles "cone correction" in the 115/118), and insisting that DSL did it for the same nonsense reasons that the diy'ers do, and insist on calling what DSL did by the name the diy'ers gave their useless process. DSL did what he did (S2 pinch, NOT cone correction) for very specific reasons, as weltersys pointed out. Diy'ers do cone correction (NOT S2 pinch) for imaginary benefits that have never been proven. Diy'er cone correction and DSL's S2 pinch are two VERY different things and should not be confused or called by the same name.
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LOL - first you're quoting me out of context. Then you're surreptitiously truncating my quotes to support your position. Go back and read my ENTIRE statement again. You know what, here, let me help you - I will highlight the part that you conveniently left out when you quoted me:
"Cone correction", as it's being used here, is simply the taking into account the volume of air in the driver's cone in the design of the TH's layout.
Now go back and read your own version and tell me how it differs in essence from mine.
And again you are still confusing a process, with the perceived advantages of that process. Driving a car is a process. That driving a car will make you fly may be a perceived (and obviously incorrect) advantage of that process. "Cone correction" is a process. Decreased distortion is a perceived advantage of that process. This is simple stuff, man.
Finally, I'm not insisting that DSL did anything. You are the only one doing that. Unless DSL chooses to share that information with us, NONE of us know the reasoning they used for the "S2 pinch", as you refer to it. We can only make educated guesses at the reasons, and for now to me it does appear like "cone correction" (which funnily enough requires a pinch at S2!) plays a part because the resulting layout looks very similar. They may have done it primarily for increasing the path length (an advantage when deployed in the TH115/8 layout), as the messages about the modified SS15 layout I provided links to clearly cover) rather than any of the other very subjective advantages mentioned previously, and no-one's arguing that - except you. YOU are the only one that's making the claim that you actually know why DSL did what they did, by saying it has nothing to do with "cone correction". What - did DSL share information about their design methodology with you?
Ok, yes this is simple. DSL uses the stub (which is probably a better description than S2 pinch) in a few designs, including the 115/118. The 115/118 is the only one of these "stubbed" designs that has a cone in the middle of S2, all the others are dual driver designs with no cone in that area. If there's no cone at S2, how can you possibly be correcting the cone? It's pretty clear that "cone correction" is not what he/they were doing if there's NO CONE in the pinched area. The 115/118 is the only one that happens to have a single driver so it only vaguely appears to be the same thing as the "cone correction" that has been going on in this forum, but it's clearly not based on the other "stubbed" designs.
To address your bold statement above, "cone correction" is NOT just taking into account the volume in the cone. Doing that is simply just doing an accurate sim. "Cone correction" in the particular context of posted info on this forum is something very different, it's placing blocks on wood in front of the driver cone to fill in the extra volume for a very specific purpose, a bunch of subjective advantages. These subjective advantages have not been proven, and some of them are pretty clearly not even possible.
If you still don't get what I'm saying there probably isn't any point to discussing it further, I can't make it any more clear.
Maybe a picture would help. In DUAL DRIVER designs it's more clear to see the difference between DSL's stub and diy "cone correction".
Clearly not the same thing.
The 115/118 has only a single driver so it vaguely looks similar to diy "cone correction" but it's clearly not, based on the "stubbed" dual driver designs. It's the same "stubbed" concept with a single driver.
Clearly not the same thing.
The 115/118 has only a single driver so it vaguely looks similar to diy "cone correction" but it's clearly not, based on the "stubbed" dual driver designs. It's the same "stubbed" concept with a single driver.
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The only thing clear here is that you are still confusing a process with the reasons given for doing the process.
No-one but you is making the claim that "cone correction is just taking into account the volume in the cone". Again you are truncating the statement I made, in which I CLEARLY went on to say "IN THE DESIGN OF THE TH's LAYOUT".
Look - whether you put blocks, cones, rods, cylinders or gummy bears in the path, or even adjust the layout of the horn entirely to "compensate" for that additional volume in the cone at that point in the TH's path, then what you're doing is employing cone correction in the design of your TH And whether you're doing it for supposed decreased distortion it provides, or for increasing the path length, or even for getting your TH to birth unicorns from its mouth, it is still cone correction. Stop confusing the *reasons* for doing it with the *process* of doing it.
Only if you believe that "cone correction" can only be done by implementing little triangles in front of each driver's cone, LOL. At the wavelengths involved here, it can be done in many more ways than that, because given the wavelengths involved, what's important is the *volume*, not the *shape*. One possible way for example would be to simply add the two cone volumes together, then pinch in S2 at the same amount to compensate. This should work if the length of the section in question is short compared to the wavelengths the horn is expected to produce.
Another thing you need to consider when looking at your specific example is that the volume displaced by the driver's basket and cone needs to be taken into consideration (it's *significantly* greater than the volume contained within the driver's cone), and could perhaps explain why there's that expansion at S1, to compensate for that volume being taken up by the driver's basket.
So, here's a little mental exercise to try with your example:
1. Flip the bottom driver and adjust the volume between S1 and S2 to compensate.
2. Increase S2 to negate any pinch that may have been implemented there for cone correction.
What do you end up with?
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