The horn adds no NLD to speak of, but it adds the bulk of the linear distortion which is highly dependent on the shape of the horn. The amplification factor occurs mostly as the compression ratio in the driver itself and as such is not a distortion that I consider as part of the horn.
This "amplification" that you talk about is widely misunderstood. In any waveguide or horn there is no "amplification" at HFs as all devices approach the same rho-c / area impedance at large ka. And all devices produce the same low impedance at low ka. It is only in the area around ka = 1=> 3 that there is any "amplification" from the waveguide over that of a direct radiator. In studies that I have done there is little difference between the gains for different shapes when the device is of finite length. There is a large difference when one looks at impedances for an infinite device, but this all gets washed away for a finite device. Some have more gain at some frequencies while the others have more gain at other frequencies. There is no shape that has more gain across the entire bandwidth. And these gains are usually only a few dB
The vast majority of the "gain" (10-20 dB) comes from the compression ratio, which multiplies the entire bandwidth by the compression ratio. This is a double edge sword: most excursion related distortions are reduced due to the lower excursion for a given SPL, but the NLD from the air nonlinearity increases with this same efficiency gain. So what happens is that the higher order NLD from the cone excursions are reduced but the lower order NLD from the air is increased. As far as perception is concerned this should allow for a much lower audible effect of the NLD - which is what I have been saying all along. The THD numbers will probably not change very much, but the audible effect should be significant.
This "amplification" that you talk about is widely misunderstood. In any waveguide or horn there is no "amplification" at HFs as all devices approach the same rho-c / area impedance at large ka. And all devices produce the same low impedance at low ka. It is only in the area around ka = 1=> 3 that there is any "amplification" from the waveguide over that of a direct radiator. In studies that I have done there is little difference between the gains for different shapes when the device is of finite length. There is a large difference when one looks at impedances for an infinite device, but this all gets washed away for a finite device. Some have more gain at some frequencies while the others have more gain at other frequencies. There is no shape that has more gain across the entire bandwidth. And these gains are usually only a few dB
The vast majority of the "gain" (10-20 dB) comes from the compression ratio, which multiplies the entire bandwidth by the compression ratio. This is a double edge sword: most excursion related distortions are reduced due to the lower excursion for a given SPL, but the NLD from the air nonlinearity increases with this same efficiency gain. So what happens is that the higher order NLD from the cone excursions are reduced but the lower order NLD from the air is increased. As far as perception is concerned this should allow for a much lower audible effect of the NLD - which is what I have been saying all along. The THD numbers will probably not change very much, but the audible effect should be significant.
Thank you Earl for the pedagogy 🙂 , (very hard to understand for me all those physic behavior without knowledge)
Thanks for that gedlee very well described and explained.
What about the way a horn limits the bandwith of the driver where it falls off the loading? It seems to me this can result in lower IM and non-linear distortion provided the builder uses the driver/horn within the "gain" range?
What about the way a horn limits the bandwith of the driver where it falls off the loading? It seems to me this can result in lower IM and non-linear distortion provided the builder uses the driver/horn within the "gain" range?
By "falls off loading" you mean at low ka (low frequencies)? This is not more band-limiting than a direct radiator - both have a limited LF capability, but specifics depend on the specific situation. There is no loading limitation in a horn at HFs. The limitation up high is due to the mass of the diaphragm, and the inductance to a certain extent.
Waht I mean is the acoustic output of the horn falls off faster below and above compared to the band where the horn effectively provides amplification to the driver. At frequencies much above the flare frequency the loading provided by the horn is essentially constant, though the response of a horn/driver combination will eventually droop higher up due to several things working in combination. So relative speaking the distortion difference between a driver used as a direct radiator and in a horn the distortion will be lower Out of this band of amplification. You also gain lower heat and losses due to the lower amount of work being done by the driver for the same SPL
Pooh - the acoustic power output of a horn is complicated. AT the very lowest freq it is third order growth, then it becomes first order rising at some point depending on the driver params. It Then becomes a first order falling response as the waveguide/horn becomes efficient. This region varies a lot depending on the horn profile. It then falls at 0-6 dB throughout the pass-band depending on the horn profile and how much directivity it has. A constant directivity falls at 6 dB, a horn that beams will fall closer to 0 dB. But then the driver response falls because of the mass break point and the power response falls at 12 dB.
I am not sure that equal distortions is what we want, unless you mean equally low, i.e. bringing the phase plug side down to the back chambers NLD. But this can't happen and still have a compression ratio.
Which one will have "lower Out of this band"?
I am not sure that equal distortions is what we want, unless you mean equally low, i.e. bringing the phase plug side down to the back chambers NLD. But this can't happen and still have a compression ratio.
Does this imply, that if there were a chamber between the throat and cone of say, for arguments sake an order of magnitude greater than the minimum (if that makes a point), or say the same as the rear chamber (probably closer to what I'm trying to say), that it would negate the above mentioned gain?
To maintain high frequency loading requires a very small enclosed volume between the diaphragm and the phase plug, less than 1mm is common.
Expanding that by an order of magnitude would make a band pass, the driver will roll off steeply somewhere around 2500 Hz. Fine for a midrange driver (and the bandpass reduces harmonic distortion), but not possible for a high frequency driver.
Art
Thanks Art, so the low end isn't so much affected by this and a baffle level throat (at a cone driver front mount distance, moderate compression ratio) is reasonable for a lower mid implementation.
I have recently played with "slot loading" (sub 200Hz), not for the loading but for the acoustical low pass due to the "mixing up" of the highs.
So does it do this by geometrically disconnecting the highs from the primary horn mode or is this saying the same thing?
I have recently played with "slot loading" (sub 200Hz), not for the loading but for the acoustical low pass due to the "mixing up" of the highs.
So does it do this by geometrically disconnecting the highs from the primary horn mode or is this saying the same thing?
Don't know what you mean by "geometrically disconnecting the highs from the primary horn mode" or "this".
Given the source and the interesting way the sources mind seems to work, my guess is this is high praise and praise not easily relinquished and it would best behoove us all to take a very close look at Nate Hanson's design. A very close look indeed,.
so Nate is using an old waveguide what's so special about that. and why does it need a closer look indeed?
I believe in giving credit where credit is due. Nate's work and his results are exemplary. Few others around here show actual comprehensive results. All we usually get are no data or insufficient data and "it sounds great!"
Nate's horn is a diy not so easy to reproduce.... Technic keeped to make it in his other thread are not so easy to understand as the description is short. But it seems smart and not so expensive to do ! Not sure it's sane for ealth...to breath while you are making it !
ok maybe i need to go old school and find more info on horn design via books as all the stuff i encounter on the web seem to prescribe to flawed approaches such as ignoring the 3rd dimension or time or am i misunderstanding some of the math?
"Old school" will only teach you old approaches. Look at the thread about waveguides here at DIY for the most up to date information. Or read chapter 6 of my book (available on-line.) Yes, the math is hard, but otherwise all you can do is cookbook stuff. If you want to do something unique then you have to understand the theory - no way around that.
And yes, I don't like fiberglass either, which is why I don't use it.
And yes, I don't like fiberglass either, which is why I don't use it.
Earl, you may produce in US a well damped single wague-guide of your own to sold it to us rest of the world now you are retired and if you don't want to sell consulting anymore ! I'm sure it could have a lot of success. Too hard to protect, you prefer to focus only on the speaker line ?
The flat pack, even if only the front bafle, is limiting the design choice for the diyers when it comes to chose the drivers around the wave guide.
WHen I look at the M2 semi horn/semi wave guide of JBL, It seems there is still some trade offs choosed !
Of course just two cents, hey I understand you have more interresting things to do than a new producing adventure 🙂.
But sorry, It's tottaly off topic. Btw I like also the idea of horns not only made for compression drivers rapted for home environment !
The flat pack, even if only the front bafle, is limiting the design choice for the diyers when it comes to chose the drivers around the wave guide.
WHen I look at the M2 semi horn/semi wave guide of JBL, It seems there is still some trade offs choosed !
Of course just two cents, hey I understand you have more interresting things to do than a new producing adventure 🙂.
But sorry, It's tottaly off topic. Btw I like also the idea of horns not only made for compression drivers rapted for home environment !
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