With a front loaded horn you can pick the F3. For instance, you can reduce the back chamber to raise the F3. This gives you the luxury of raising the efficiency, if you don't mind a higher F3.
You can't do that with a TH. Because there's no back chamber, you are "locked in" to a specific F3.
Basically you can't violate Hoffman's Iron Law. One design isn't more efficient than the other. Tapped Horns tend to have lower efficiencies than FLH, but that's simply because you can make them smaller. It's as simple as that.
You can't do that with a TH. Because there's no back chamber, you are "locked in" to a specific F3.
Basically you can't violate Hoffman's Iron Law. One design isn't more efficient than the other. Tapped Horns tend to have lower efficiencies than FLH, but that's simply because you can make them smaller. It's as simple as that.
Don't know about that - I've never been able to simulate 50% efficiency with a TH design, regardless of how large or how many in parallel. A sufficiently large FLH, or group of them, will simulate out at 50% across its bandwidth. Higher inbput Z for the same SPL. Real world losses (like a real stack of horns not being rigidly coupled together) will bring this down, but it will for a TH stack too.
I've been trying to bend Hoffman's Iron Law for a long time, and it seems to be really hard to do.
For a proper comparison, we'd want to take a driver and put it in a TH and put it in a FLH with the same bandwidth. That's tricky though; the TH will tend to have a lower F3 because the F3 is basically dictated by the FS.
For instance, a B&C 12" in a front loaded horn will work with a wide range of F3s. You might use a small back chamber to achieve an F3 of 150hz. Or you might use a large back chamber to achieve an F3 of 75hz. But the same driver in a tapped horn will have an F3 of about 40hz. That's because the optimal F3 of the TH is determined by the FS of the driver, which can't be changed. (But we CAN change the FB of the chamber of a FLH.)
The pic above compares the efficiences of my 8NDL51 FLH, which I actually built, and a 8NDL51 TH, which I considered, but scrapped in lieu of the FLH.
We can see that the TH has a "peaky" efficiency graph. At some frequencies, it's REALLY efficient, and at others, it's not. The FLH efficiency curve is broader.
The volume of both boxes is virtually identical - 66 and 67 liters, respectively. The TH plays lower.
Sure about that? Try varying the path length or the expansion ratio of the TH using the same driver
True, you can vary it to some extent.
But you're still stuck with with these parameters:
fs, qts, vas
In a front loaded horn, you have these parameters:
fs, qts, vas, fb (the frequency of the sealed portion of the horn) and qtc (the Q of the sealed portion of the horn)
The inability to tweak the qtc and the fb is what makes tapped horns quite a bit less flexible than front loaded horns.
And, again, I'm not saying that one is superior to the other. Just saying that both enclosures play by Hoffman's Iron Law. There isn't any inherent efficiency advantage to either one.
Sure, but I'd found so far with suitable drivers that there's quite a range of adjustment available, as not only can you change the path length and expansion of the TH, you can also vary the expansion to produce a wider or narrower passband.
Another big advantage of THs over FLHs is the displacement requirements. With a FLH, the lowest displacement minimum is in the middle of the passband, and the displacement can go crazy after that, and crazy = distortion. With a TH, the lowest displacement minimum occurs at or below Fb. This has the effect of reducing distortion at the lower end of the passband.
Totally. I think we agree on everything.
But OP asked "how much less efficient" they were, and I don't think it's that simple. Both of them have advantages and disadvantages.
(BTW, I also think that's why Danley started doing FLHs again.)
I believe TD at one point had mentioned that at or above a certain size FLHs start to be a better option. Note all the FLHs he's done are quite a bit larger than his THs...
And has a much less flat responce, the DBH218 is very undersized in singles...
Any flh that is not full size by the mathematical definition of a flh is undersized, but that doesn't mean you can't get a really nice response from a MASSIVELY undersized flh.
Here's the measured response (measured outdoors) of a VERY low tuned flh with the Mach5Audio 18 inch UXL driver. (Again, this is measured, not simulated.) Ignore the black line, the green line is the measured response.
This horn is 4 x 4.75 x 2 feet externally, so it's a really big horn, but it's MASSIVELY undersized for the frequencies it's capable of and the response curve is still really nice. And on top of all this it's a very high inductance driver too, so it's at a disadvantage from that aspect too (it's hard to get good response from high inductance drivers in undersized resonant boxes).
As I've mentioned and demonstrated at least a few dozen times, flhs don't have to be any bigger than tapped horns to get the same (or even better) response and spl (assuming the same driver and same low knee frequency). You might have to get creative with the flare and the flh might need a lot more power to get the same spl, but flhs can be the same size as tapped horns and you can get the same performance.
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Absolutely right, size dictates max potential output. There's no way around that. But given the same size all resonant enclosure types will put out the same spl. (With a few simple caveats.) There's usually one type that's a bit better for the specific goalset but at the end of the day it's all about size, that's what determines your max spl, and even massively undersized enclosures can have very nice response curves.
To be fair though, you can't do 105 to the low knee with a small tapped horn either. (Since it's all about size.) If you make a horn (of any type) the same size as a ported box it's going to be about as loud as a ported box.
To be fair though, you can't do 105 to the low knee with a small tapped horn either. (Since it's all about size.) If you make a horn (of any type) the same size as a ported box it's going to be about as loud as a ported box.
I see we are still talking one or two variables at a time as if transient response, distortion, and Doppler were not criteria of performance and as if a few cubes up or down mattered.
I've recently begun thinking about things (traffic safety, for example) in terms of Markowitz'
"efficient frontier"*. There are various good solutions but the object is to remain near the frontier.
Ben
*1990 Nobel prize in economics
I've recently begun thinking about things (traffic safety, for example) in terms of Markowitz'
"efficient frontier"*. There are various good solutions but the object is to remain near the frontier.
Ben
*1990 Nobel prize in economics
Ben, nobody is ignoring anything. Distortion is lower in horns (much lower) than the type of boxes (or OB) that you like because efficiency is MUCH higher. Doppler is much lower as well, also because efficiency is much higher. These things are so well known they don't get mentioned much but no one is ignoring them, they are crucial and some of the best reasons to get into horns. If you want to do a head to head measured comparison of a sub like the one I showed the response curve of above vs your antique woofer OB "sub" with 2 mm xmax send me a PM and we'll set something up. We can measure every performance metric you like. I already know which one is going to win, and which one is going to sound much better, and which one will actually go louder than 80 or so db, but it would be fun.
Time to actually listen to the stuff you like to talk about, Ben. Since you've never heard a tapped horn before you have no qualification at all to talk about the evils of "trafficking in resonances", and if your Klipshorn is the only flh you've heard you are in for a shock when you hear a good flh, one that doesn't have such a wildly peaky response due to it's severe undamped resonances.
Time to actually listen to the stuff you like to talk about, Ben. Since you've never heard a tapped horn before you have no qualification at all to talk about the evils of "trafficking in resonances", and if your Klipshorn is the only flh you've heard you are in for a shock when you hear a good flh, one that doesn't have such a wildly peaky response due to it's severe undamped resonances.
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Right, because OP was asking questions which very specifically concerned 3 things: size, efficiency, and LF corner.
Your points are certainly reasonable things to think about, but given your general posting habits I can't help but wonder if attempting to derail threads is a hobby for you.
More on this - awhile ago I did a quick sim session to prove that all the resonant enclosures would have the same efficiency, same excursion* and could even have almost exactly the same response curve shape if they used the same driver, were the same size and had the same low knee frequency.
Someone posted an odd shaped tapped horn, I matched all these things (response curve shape, excursion* and efficiency) with a bunch of very different designs. I showed a couple of different tapped horns, a bowtie shape tapped horn and a front loaded horn.
Comparison is here, post 75 - 79 - http://www.diyaudio.com/forums/subw...bc-subs-reverse-engineered-8.html#post4102882
There are no magic enclosures that have more output than others. All the resonant type enclosures will have the same output if they use the same driver, same size, same low knee (with a few simple caveats).
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Yep.
When I was younger, I developed some opinions on sub boxes that were subjective. For instance, I couldn't get dual-reflex bandpass to sound good, and single reflex bandpass always sounded a bit "off."
As I get older, and begin to experiment with box types that I'd dismissed when I was younger, I find that many of the boxes that I didn't like were simply built wrong. For instance, I recently built some bandpass boxes and it took about four rounds of sealing them before the measured response matched the simulated response.
IE, it wasn't a defective design, it was sloppy construction that was causing the problem. (And note that I would have NO IDEA what the problem was if it wasn't for my handy dandy microphone.)
I think that these problems may affect a lot of builders out there; there's probably a lot of people who like sealed boxes and tapped horns and they think they're inherently better. But the truth is that a lot of the exotic box types are simply less forgiving of sloppy workmanship, particularly when it comes to air leaks. A leaky bandpass box / vented box or front loaded horn simply doesn't work as the sims predict. I think that sealed boxes are incredibly forgiving. And tapped horns are fairly forgiving too, because there's no back chamber. Dual reflex bandpass is pretty darn unforgiving.
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