I have been unable to find much information on this topic. Anyone has some literature/experience?
Thank you,
M
Thank you,
M
I was contemplating making some rectangular horns out of hardwood for a pair of Dayton PT-2 planar tweeters. The reason is that I need to mount them back of the baffle to time align the diaphragm with the mid range drivers in one of my experimental designs. I was just going to 'do it' and see what happens. That is project 8,547.
I don't know what the point is sonically, but to make one probably best get hold of a local enthusiast wood Turner,
Here's a strange link the though http://vincent.brient.free.fr/round_horns.htm
Here's a strange link the though http://vincent.brient.free.fr/round_horns.htm
WaveGuide
Horns are pressure to volume translators that work best with a transducer that has a stiff radiator and a low Qts for tight control of the air mass.
The principal virtue of a horn resides in the possibility of presenting practically any value of acoustical impedance to the sound generator. As a side benefit, it provides directivity contol to the dispersion of acoustical energy. A wafeguide is a horn with the directional characteristics being the prime criteria over optimum driver loading. Many planar transducers are fair candidates for horn loading.
A true ribbon, built with 2-10 micron thick aluminum supported at two ends, is better suited for a waveguide...a very shallow horn with wide radius to control dispersion and diffraction. Some designers use a waveguide to both control ribbon dispersion, and reduce the effects of a deep magnet cavity.
Geddes has a few recent papers on waveguides.
Horns are pressure to volume translators that work best with a transducer that has a stiff radiator and a low Qts for tight control of the air mass.
The principal virtue of a horn resides in the possibility of presenting practically any value of acoustical impedance to the sound generator. As a side benefit, it provides directivity contol to the dispersion of acoustical energy. A wafeguide is a horn with the directional characteristics being the prime criteria over optimum driver loading. Many planar transducers are fair candidates for horn loading.
A true ribbon, built with 2-10 micron thick aluminum supported at two ends, is better suited for a waveguide...a very shallow horn with wide radius to control dispersion and diffraction. Some designers use a waveguide to both control ribbon dispersion, and reduce the effects of a deep magnet cavity.
Geddes has a few recent papers on waveguides.
Re: WaveGuide
Thanx for this encouraging news. Now all I need is time to experiment.
I come into this speaker design with a background in microwave antennas. To me a waveguide is usually many wavelengths long and is used to move radio frequency energy with very low loss from point a to point b. If the end of the waveguide contains, steps or tapers, parallel plates, etc. for the purpose of launching a wave into open air while shaping it's field distribution or pattern it becomes either a horn or a lens.
IMO, I do not think that these short tapered shapes that are placed on the front of a tweeter should be called "wave guides". They are probably short horns. IMO the treatment on the front of the Dayton PT-s planar tweeter is a short horn. JBL was correct in calling some of their "wave guiding" contraptions "acoustical lenses".
LineSource said:
Thanx for this encouraging news. Now all I need is time to experiment.
I come into this speaker design with a background in microwave antennas. To me a waveguide is usually many wavelengths long and is used to move radio frequency energy with very low loss from point a to point b. If the end of the waveguide contains, steps or tapers, parallel plates, etc. for the purpose of launching a wave into open air while shaping it's field distribution or pattern it becomes either a horn or a lens.
IMO, I do not think that these short tapered shapes that are placed on the front of a tweeter should be called "wave guides". They are probably short horns. IMO the treatment on the front of the Dayton PT-s planar tweeter is a short horn. JBL was correct in calling some of their "wave guiding" contraptions "acoustical lenses".
LinSource wrote:
Yes, this is exactly, what I am after. Could you please give me some examples of the:
Thank you very much,
M
Yes, this is exactly, what I am after. Could you please give me some examples of the:
Thank you very much,
M
my take on the loading of a ribbon or other non compression driver with a horn of any sort is this:
If you start with a driver that has a flat response and add a horn, you will get a response that rises - highest at the most effective frequency of the horn, which is usually a function of the expansion. The ability of any horn to be "flat" without ripples is related to the mouth size's relationship to the expansion rate
(which in turn is related to some "frequency"). So that's a bump in the response at the bottom end of the useful response range.
Generally speaking the best candidates for horn loading are drivers that are non flat in free air - having a rising response. The ability to be "stiff" as in the case of a compression driver (the air load *not* being so great as to overcome the force on the diaphragm) is what permits the wide range operation of the compression driver loaded into a horn. In free air it acts like a rather bandwidth limited tweeter... (thus the stiff diaphragm and BIG high Tesla magnet structure, limited excursion)
In the case of the compression driver, the horn acts like a lever whose motion increases with frequency in exact ratio to the falling response of the diaphragm... thus the output of the horn system is increases as the frequency drops, while the excursion of the diaphragm is not - whereas in a direct radiator the excursion increases as the frequency drops. In the compression driver the *force* of the diaphragm's motion is transformed into air motion by the horn's loading - a strong short force is transformed into a large not so strong force... a lever.
The other useful application for horn loading, and the one that has been most often employed (generally speaking) for ribbon drivers is to use the horn to "extend" the useful LF response of the ribbon below where it would otherwise start to roll off free air (or baffle mounted). So, if ur ribbon runs out of headroom or response at say 2.5kHz, adding a horn might get you down an octave or less in additional bandwidth, with some headroom benefits as well at the 2.5kHz area... as mentioned it also serves to control the dispersion/polar response to some extent.
Keep in mind, that as far as I can tell, at sufficiently high frequencies the horn isn't doing very much and the driver tends to
act like it is sitting out in free air, and the polar response tends to narrow as the frequency goes up...
Quite frankly, I've seen polar plots of some new waveguides and I am unsure how they manage to keep the polar response "flat" - in the case of the one I saw it was "flat" in a 30 deg dispersion out to ~20kHz... which is fairly remarkable actually. Of course 30 degrees is still narrow compared to what most drivers are doing except at the HF limits of their response...
Many ribbon drivers have been made with horns, the most famous are the Decca Ribbons, Kelly Ribbons and Romagna Ribbons - all of the same heritage and vintage.
If ur thinking ur going to get the same sort of efficiency that you get with compression drivers and horns, it's not likely.
_-_-bear
If you start with a driver that has a flat response and add a horn, you will get a response that rises - highest at the most effective frequency of the horn, which is usually a function of the expansion. The ability of any horn to be "flat" without ripples is related to the mouth size's relationship to the expansion rate
(which in turn is related to some "frequency"). So that's a bump in the response at the bottom end of the useful response range.
Generally speaking the best candidates for horn loading are drivers that are non flat in free air - having a rising response. The ability to be "stiff" as in the case of a compression driver (the air load *not* being so great as to overcome the force on the diaphragm) is what permits the wide range operation of the compression driver loaded into a horn. In free air it acts like a rather bandwidth limited tweeter... (thus the stiff diaphragm and BIG high Tesla magnet structure, limited excursion)
In the case of the compression driver, the horn acts like a lever whose motion increases with frequency in exact ratio to the falling response of the diaphragm... thus the output of the horn system is increases as the frequency drops, while the excursion of the diaphragm is not - whereas in a direct radiator the excursion increases as the frequency drops. In the compression driver the *force* of the diaphragm's motion is transformed into air motion by the horn's loading - a strong short force is transformed into a large not so strong force... a lever.
The other useful application for horn loading, and the one that has been most often employed (generally speaking) for ribbon drivers is to use the horn to "extend" the useful LF response of the ribbon below where it would otherwise start to roll off free air (or baffle mounted). So, if ur ribbon runs out of headroom or response at say 2.5kHz, adding a horn might get you down an octave or less in additional bandwidth, with some headroom benefits as well at the 2.5kHz area... as mentioned it also serves to control the dispersion/polar response to some extent.
Keep in mind, that as far as I can tell, at sufficiently high frequencies the horn isn't doing very much and the driver tends to
act like it is sitting out in free air, and the polar response tends to narrow as the frequency goes up...
Quite frankly, I've seen polar plots of some new waveguides and I am unsure how they manage to keep the polar response "flat" - in the case of the one I saw it was "flat" in a 30 deg dispersion out to ~20kHz... which is fairly remarkable actually. Of course 30 degrees is still narrow compared to what most drivers are doing except at the HF limits of their response...
Many ribbon drivers have been made with horns, the most famous are the Decca Ribbons, Kelly Ribbons and Romagna Ribbons - all of the same heritage and vintage.
If ur thinking ur going to get the same sort of efficiency that you get with compression drivers and horns, it's not likely.
_-_-bear
Josef Merhaut wrote an article about building an electrostic horn in 1968. It was published in the Journal of the Audio E ngineering Society. I have it. I have not scanned it, but I will and send it to you via Email if you want.
The horn is 20" long and 18" wide. It has flat response from 19 KHz down to 1500 Hz, and is 3 dB down at 1000 Hz.
I have not scanned the article yet, but I will and Email it if you wish. Anyone who wants it can Email me.🙂
The horn is 20" long and 18" wide. It has flat response from 19 KHz down to 1500 Hz, and is 3 dB down at 1000 Hz.
I have not scanned the article yet, but I will and Email it if you wish. Anyone who wants it can Email me.🙂
That ESL horn loaded was *essentially* a compression driver set up... he used multiple diaphragms, with a phase compensated entry to a single throat entrance... but it is/was a nice project...
_-_-bear
_-_-bear
This thread started off with the idea of horn loading a PT2 tweeter. My only problem with that idea is that I do not like the low end sound of the PT2. The sub 9 kHz response is where this tweeter is weakest. The problem is not a lack of response, but rather poor quality. Most of the bottom end output is caused by resonance or diaphragm vibration mode and is smeared well into the decay portion of the transient response.
Don't take this the wrong way. The PT2 is not a bad tweeter, just difficult to work with. Horn loading is unlikely to cure the problem and is likely to make the problem more audible.
Good designing and good building,
Mark
Don't take this the wrong way. The PT2 is not a bad tweeter, just difficult to work with. Horn loading is unlikely to cure the problem and is likely to make the problem more audible.
Good designing and good building,
Mark
Member
Joined 2003
LineSource,
I've been interested in ribbons for a long time but, generally, very little interest in horns.
You seem to have very specific ideas about the application of waveguides to true ribbons. What is your definition of a "shallow" horn (in terms of wavelength)? What is a "wide radius"...conical, exponential, other???
Which Geddes paper do you recommend? I'm interested enough to buy one...just one for now.
Thanks,
Paul
I've been interested in ribbons for a long time but, generally, very little interest in horns.
You seem to have very specific ideas about the application of waveguides to true ribbons. What is your definition of a "shallow" horn (in terms of wavelength)? What is a "wide radius"...conical, exponential, other???
Which Geddes paper do you recommend? I'm interested enough to buy one...just one for now.
Thanks,
Paul
I am having some troouble with my Hotmail Email box, the one diyAudio uses. It tends to fill up and cut off incoming Emails.
I have received a couple of requests already for Merhaut's Horn Loaded Electrostatic Loudspeaker article. For those who might have sent a request and had my email service reject it, please comment here in this thread and I will try to contact you.
I have received a couple of requests already for Merhaut's Horn Loaded Electrostatic Loudspeaker article. For those who might have sent a request and had my email service reject it, please comment here in this thread and I will try to contact you.
These look interesting.
http://www.e-speakers.com/products/lcy-components.html
An externally hosted image should be here but it was not working when we last tested it.
http://www.e-speakers.com/products/lcy-components.html
Mac,
Yes those do look interesting I wonder why they put a horn of radial symmetry on a rectangular source however. There has to be some mismatch here. I would have expected a smooth transition section. A "morphing transition"! That's my new patented name guys! 😀
Yes those do look interesting I wonder why they put a horn of radial symmetry on a rectangular source however. There has to be some mismatch here. I would have expected a smooth transition section. A "morphing transition"! That's my new patented name guys! 😀
As I am reading your suggestions, I realized that my subject line was purely worded. What I am after is pattern control, and not so much increased efficiency from horn loading.
So, here are the two questions I should have asked:
1. can one "force" the sound to follow the horn countour without undue disturbance of the sound wave; and
2. what ribbon tweeter could be used given the (as I understand) high pressure in the throat?
Thank you,
M
So, here are the two questions I should have asked:
1. can one "force" the sound to follow the horn countour without undue disturbance of the sound wave; and
2. what ribbon tweeter could be used given the (as I understand) high pressure in the throat?
Thank you,
M
mefistofelez said:
Not exactly... what ur interested in is more the wave launch from the horn with respect to frequency... again as you go higher in freq the horn has less of an effect and the driver tends to "not see" a horn and act like a direct radiator...
Thus the advanced "wave guide" designs like Dr. Geddes which are intended to control that aspect over the loading and efficiency aspects...
imho, none.
All the ribbon tweeters that I have seen loaded into horns are "loosely" loaded... not tightly coupled at all... so the pressure in the throat is limited quite a bit compared to the compression driver set up... nothing wrong with this. So you can use any ribbon you like, pretty much.[/quote]
_-_-bear
mac said:
To my eye these look really bad, with a sharp hard transistion from what appears to be a short parallel wall area between the ribbon and the "horn". Major diffraction going on here.
Also, the ribbon design itself appears to be a copy of a recently patented (sic) ribbon that uses this slit down the center of the ribbon itself. This design was discussed in the thread here in the ESL/Ribbon area quite recently... wonder if it is a rip-off or if it is licensed?
who knows, maybe these are just great...
_-_-bear
Dear Bear,
I have an impression that we are miscommunicationg, arguably due to my inability to express myself.
Are you referring to the fact that the driver's dispersion pattern changes (narrows) with increasing frequency?
I am aware of that, but at a certain point, the driver's dispersion pattern will be equal to or greater than the angle of the horn/waveguide attached at that frequency. What will happen?
If the above is misinterpretation of your thoughts, please correct me.
Correct me if I am wrong, but it is my understanding that the horn expansion controls the compression (loading). As such, one should be able to adjust the amount of loading by the (inital) shape of the horn, correct? If so, how?
Well, I have read his papers. And although he appears to be concerned with the matching of the diriver's characteristics to the waveguide, in my final analysis, he gives essentially "one formula fits all" interface between the driver and the oblate spheroid horn contour, and I am unable to discren, how he "control that aspect over the loading and efficiency aspects." Could you point me to the right equation/direction?
Thank you,
M
I have an impression that we are miscommunicationg, arguably due to my inability to express myself.
Are you referring to the fact that the driver's dispersion pattern changes (narrows) with increasing frequency?
I am aware of that, but at a certain point, the driver's dispersion pattern will be equal to or greater than the angle of the horn/waveguide attached at that frequency. What will happen?
If the above is misinterpretation of your thoughts, please correct me.
Correct me if I am wrong, but it is my understanding that the horn expansion controls the compression (loading). As such, one should be able to adjust the amount of loading by the (inital) shape of the horn, correct? If so, how?
Well, I have read his papers. And although he appears to be concerned with the matching of the diriver's characteristics to the waveguide, in my final analysis, he gives essentially "one formula fits all" interface between the driver and the oblate spheroid horn contour, and I am unable to discren, how he "control
Thank you,
M
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