Evolution of the Tapped Horn
Figure 1. shows a conventional front loaded bass horn, the type that has
been used for nearly 90 years. The back chamber provides a "spring" to
keep the driver cone from exceeding it's travel, and the tapered front
allows the pressure from the front of the driver to gradually transform
and fill the mouth (where the red arrow is) with a much louder sound.
Figure 2. is a horn-like device invented by Tom Danley. As shown, it has
a single driver at the apex of the cone, and four drivers a little way
along the cone.
This has several benefits.
1. The sound direction is well controlled.
2. The "source" of the sound appears to be a single point.
3. Multiple units can be arrayed without "lobeing."
In addition, figure 2 opens up the possibility of adding drivers anywhere
along the horn.
Figure 3. is a tapered organ pipe. Most organ pipes are not tapered,
and most organ pipes are circular in cross section, not rectangular.
Playing certant notes, the driver would cause the air to resonate and
make a lot of sound. Unfortunately, other notes would be very quiet.
Taking a page from Tom's horn (figure 2), we can add a second driver in
the horn as shown in figure 4. Assuming we can block the sound comming
from the back of the left driver, and that comming from the front of
the right driver, the spacing of the drivers can be chosen to add to the
sound of the quiet notes, while reducing the sound of the loud notes.
Problem: when did you last transport an organ pipe? We gotta make this
thing more portable. If we remove the right hand driver, and fold figure
4 by rotating the left half clockwise over the right half, we end up
with figure 5. Now, one driver can provide the input into the small end
of the horn, while the back of that driver provides the input into the
large end of the horn. And we don't have to block anything!
Figure 6 is a variation made by folding the left half of figure 5, and
figure 7 is the same as figure 5 with the mouth rotated. Several other
variations are possible.
Figure 1. shows a conventional front loaded bass horn, the type that has
been used for nearly 90 years. The back chamber provides a "spring" to
keep the driver cone from exceeding it's travel, and the tapered front
allows the pressure from the front of the driver to gradually transform
and fill the mouth (where the red arrow is) with a much louder sound.
Figure 2. is a horn-like device invented by Tom Danley. As shown, it has
a single driver at the apex of the cone, and four drivers a little way
along the cone.
This has several benefits.
1. The sound direction is well controlled.
2. The "source" of the sound appears to be a single point.
3. Multiple units can be arrayed without "lobeing."
In addition, figure 2 opens up the possibility of adding drivers anywhere
along the horn.
Figure 3. is a tapered organ pipe. Most organ pipes are not tapered,
and most organ pipes are circular in cross section, not rectangular.
Playing certant notes, the driver would cause the air to resonate and
make a lot of sound. Unfortunately, other notes would be very quiet.
Taking a page from Tom's horn (figure 2), we can add a second driver in
the horn as shown in figure 4. Assuming we can block the sound comming
from the back of the left driver, and that comming from the front of
the right driver, the spacing of the drivers can be chosen to add to the
sound of the quiet notes, while reducing the sound of the loud notes.
Problem: when did you last transport an organ pipe? We gotta make this
thing more portable. If we remove the right hand driver, and fold figure
4 by rotating the left half clockwise over the right half, we end up
with figure 5. Now, one driver can provide the input into the small end
of the horn, while the back of that driver provides the input into the
large end of the horn. And we don't have to block anything!
Figure 6 is a variation made by folding the left half of figure 5, and
figure 7 is the same as figure 5 with the mouth rotated. Several other
variations are possible.
Attachments
Uh..OK..
I wouldn't call that the evolution of a Tapped horn.
No disrespect to Mr. Danley but he did not event the Tapped Horn. They have been around Since at least the 40's. Albeit I think Danley has taken this to another level if all the specs given for the TH subs on his site are 100% accurate.
I wouldn't call that the evolution of a Tapped horn.
No disrespect to Mr. Danley but he did not event the Tapped Horn. They have been around Since at least the 40's. Albeit I think Danley has taken this to another level if all the specs given for the TH subs on his site are 100% accurate.
In my humble opinion:
The question of Tom's patent is not about the original idea of trying to use both sides of the driver. This is simply a course of action that makes practical sense and has been tried before in many different ways. I believe it is the art of actually making the concept work and the method he uses to do so that are covered in the patent.
In short...he made it work in a usefull manner.
The question of Tom's patent is not about the original idea of trying to use both sides of the driver. This is simply a course of action that makes practical sense and has been tried before in many different ways. I believe it is the art of actually making the concept work and the method he uses to do so that are covered in the patent.
In short...he made it work in a usefull manner.
screamersusa said:In my humble opinion:
The question of Tom's patent is not about the original idea of trying to use both sides of the driver. This is simply a course of action that makes practical sense and has been tried before in many different ways. I believe it is the art of actually making the concept work and the method he uses to do so that are covered in the patent.
In short...he made it work in a usefull manner.
Absolutely correct.
But just bear in mind that the patent is applied for but hasn't been granted yet, the current status is submitted for examination. In my experience many patents either have to be rewritten to get passed or are rejected because of prior art, and it takes several yoears before you know what (if anything) will be granted.
Ian
P.S. Look here in case you think I'm bulls*itting...
http://v3.espacenet.com/searchResults?locale=en_GB&IA=Dedic,+Ian&compact=false&DB=EPODOC
Hi
Don, the write up is pretty much parallel to how it came about, thanks.
Some additional detail;
The “Tapped horn” came to life when I was thinking about the reflection that occurs when the sound from the drivers in fig#2 bounces back from the closed end and causes a cancellation notch.
That notch defines (just above) the upper limit of the usable response for the drivers in that position.
I wondered what happens “IF” I substituted an active source instead of a reflection and inverted the source to add instead of cancel similar to a transmission line..
It took some significant time doodling around in Akabak before I saw a response which looked promising and then a lot more time to discern the fine details, a process one could argue still continues.
It was well after there were working tapped horns that a speaker friend ran across a reference to the Jensen Transflex patent and sent it to me.
In my life working with loudspeakers I had never seen one or heard of it before..
Part of what governs if the patent office issues a patent is if the product offers advantages over prior art, if it is unique relative to prior art and so on.
Clearly, if anyone built a transflex as described, they would instantly find why they never caught on and went extinct.
You need to have a “horn taper” to have the loading you need to make the response flat which the transflex didn’t have, you need to have the driver parameters and acoustic dimensions appropriately sized which the transflex didn’t have. These are more difficult than even a normal horn to design.
Lastly, an individual can say I didn’t invent this if they wish, my main concern is IF the patent office, after analyzing all the prior loudspeaker art in detail, judges that it is novel enough to deserve a patent. So far, they have agreed.
It should be obvious that if these had existed before and performed like the Tapped horn does now, they would have been in widespread use all along.
FlipC do you think there is a reason the whole industry would over look a way to get to below 20Hz in a “smallish” package like the Spud or DTS-20? Or get bass out of a tiny box like the Th-mini?
Why would all the big speaker companies have let a small company like us have all the fun and eat holes in their subwoofer markets?
Best,
Tom
Don, the write up is pretty much parallel to how it came about, thanks.
Some additional detail;
The “Tapped horn” came to life when I was thinking about the reflection that occurs when the sound from the drivers in fig#2 bounces back from the closed end and causes a cancellation notch.
That notch defines (just above) the upper limit of the usable response for the drivers in that position.
I wondered what happens “IF” I substituted an active source instead of a reflection and inverted the source to add instead of cancel similar to a transmission line..
It took some significant time doodling around in Akabak before I saw a response which looked promising and then a lot more time to discern the fine details, a process one could argue still continues.
It was well after there were working tapped horns that a speaker friend ran across a reference to the Jensen Transflex patent and sent it to me.
In my life working with loudspeakers I had never seen one or heard of it before..
Part of what governs if the patent office issues a patent is if the product offers advantages over prior art, if it is unique relative to prior art and so on.
Clearly, if anyone built a transflex as described, they would instantly find why they never caught on and went extinct.
You need to have a “horn taper” to have the loading you need to make the response flat which the transflex didn’t have, you need to have the driver parameters and acoustic dimensions appropriately sized which the transflex didn’t have. These are more difficult than even a normal horn to design.
Lastly, an individual can say I didn’t invent this if they wish, my main concern is IF the patent office, after analyzing all the prior loudspeaker art in detail, judges that it is novel enough to deserve a patent. So far, they have agreed.
It should be obvious that if these had existed before and performed like the Tapped horn does now, they would have been in widespread use all along.
FlipC do you think there is a reason the whole industry would over look a way to get to below 20Hz in a “smallish” package like the Spud or DTS-20? Or get bass out of a tiny box like the Th-mini?
Why would all the big speaker companies have let a small company like us have all the fun and eat holes in their subwoofer markets?
Best,
Tom
Tom Danley said:
I do hope Tom gets his TH patent, his work on the TH does IMHO represent a significant step forward in bass speaker design.
But it ain't over 'til the fat lady sings (the patent is granted) -- out of a batch of 6 I submitted to the EPO last year, when I got the examination reports back I found that:
-- one looks OK as is
-- two are probably OK with more explanation/rewriting
-- two will have to have the claims restricted to avoid prior art
-- one was completely blown out of the water by prior art I was unaware of :-(
At least it's an EPO patent, the European patent examiners are much more on the ball than US ones who'll let almost any old rubbish through
Ian
"out of a batch of 6 I submitted to the EPO last year, when I got the examination reports back I found that:
-- one looks OK as is
-- two are probably OK with more explanation/rewriting
-- two will have to have the claims restricted to avoid prior art
-- one was completely blown out of the water by prior art I was unaware of :-(
At least it's an EPO patent, the European patent examiners are much more on the ball than US ones who'll let almost any old rubbish through"
I have to agree, this is not an easy path. My experience has been similar, getting anything through "as is' is the rare exception, not the rule.
So far (knock on wood) they have agreed with the applications i have filed more recently.
One thing i have done differently is to file a "place holder" application first, this stretches the process out even longer than normal.
Best,
Tom
-- one looks OK as is
-- two are probably OK with more explanation/rewriting
-- two will have to have the claims restricted to avoid prior art
-- one was completely blown out of the water by prior art I was unaware of :-(
At least it's an EPO patent, the European patent examiners are much more on the ball than US ones who'll let almost any old rubbish through
"I have to agree, this is not an easy path. My experience has been similar, getting anything through "as is' is the rare exception, not the rule.
So far (knock on wood) they have agreed with the applications i have filed more recently.
One thing i have done differently is to file a "place holder" application first, this stretches the process out even longer than normal.
Best,
Tom
FlipC: The Transflex is the earliest "prior art" I have seen, and it's from
the 50's. Danley's efforts yielded the first practical tapped horn, but
determining if he is the "inventor" will be the patent office's call.
ScreamersUSA & Iand: You're right of course. You two guys have done much to
help me stay on track with Tapped Horns. After 40 years of drawing cartoons
of airplanes, I'm pretty good with cad. My contribution to the forum has
been folding up the boxes that other forum members have simulated.
Mister Danley: I have been following you since the early days of the LabSub.
You have provided me with a whirl-wind tour of the world of bass audio.
Thank you for sharing your genius!
~Don
the 50's. Danley's efforts yielded the first practical tapped horn, but
determining if he is the "inventor" will be the patent office's call.
ScreamersUSA & Iand: You're right of course. You two guys have done much to
help me stay on track with Tapped Horns. After 40 years of drawing cartoons
of airplanes, I'm pretty good with cad. My contribution to the forum has
been folding up the boxes that other forum members have simulated.
Mister Danley: I have been following you since the early days of the LabSub.
You have provided me with a whirl-wind tour of the world of bass audio.
Thank you for sharing your genius!
~Don
This one is tapered:
http://www.google.com/patents?id=_J...182&source=gbs_selected_pages&cad=0_1#PPA1,M1
It is expired, but in principle the same. The Danley claims are different, and thus a new patent could be issued on that basis. I suggest it be listed as prior art.
http://www.google.com/patents?id=_J...182&source=gbs_selected_pages&cad=0_1#PPA1,M1
It is expired, but in principle the same. The Danley claims are different, and thus a new patent could be issued on that basis. I suggest it be listed as prior art.
I had come across the Transflex some time ago
while researching the original Imperial. The other was the one djk list.
Danley,
First, THANK YOU. For being the master you are and willing to pass along knowledge. I have read app 109075 a few times. Trying to get the information to soak in. My fascination with you started with the BassTech 7.
And No.
I wouldn't think they (speaker companies) would have slept on it. Why I stated that you have taken this to another level. I'm just looking at a puzzle trying to figure out the magic used to get the square piece into around hole.
Off subject:
Says your in IL but DSL is in Atlanta?
Does the DTS have pipes?
Saw a picture and it had pipes of each side of the driver. If they are are they used as ports or a type of wave guide?
And lastly
Do a McCauley 6174 sub!
while researching the original Imperial. The other was the one djk list.
Danley,
First, THANK YOU. For being the master you are and willing to pass along knowledge. I have read app 109075 a few times. Trying to get the information to soak in. My fascination with you started with the BassTech 7.
And No.
I wouldn't think they (speaker companies) would have slept on it. Why I stated that you have taken this to another level. I'm just looking at a puzzle trying to figure out the magic used to get the square piece into around hole.
Off subject:
Says your in IL but DSL is in Atlanta?
Does the DTS have pipes?
Saw a picture and it had pipes of each side of the driver. If they are are they used as ports or a type of wave guide?
And lastly
Do a McCauley 6174 sub!
FlipC said:
I wouldn't recommend the 6174 for this type of application, the BL is too low and the cone isn't stiff enough, it's really optimised for large (15ft3) low-tuned (25Hz) reflex boxes. And even in such a box the power handling doesn't seem to be that good both from the AES shootout and my own personal experience, I fried the voice coil on one using an unlcipped 1200W amp -- replaced it with a Seismic 8196 which has lasted more than 5 years now.
If you really want to use an 18" driver -- and for a TH smaller drivers (15" or 12") are usually better, even if you need 2 or 4 of them -- there are other drivers around which are more suitable than the 6174.
Ian
Not necessarily, if you use a higher-Q driver and accept a non-flat upper response (the intent being to treat this with the x-over or EQ or even stuffing). See my P.O.C folded tapped-pipe here - http://www.diysubwoofers.org/projects/other/tapped-pipe/results2.html. It's basically a Jensen Transflex with some more folding. The upper peak disappeared when the first half of the pipe was stuffed.
True - it's response is VERY dependent on the parameters of the driver - as the "horn expansion" is no longer a parameter that can be varied.
OTOH, bear in mind that they did not have access to high-Pe and high-Xmax drivers in 1959 like they do now.
. My little P.O.S, erm P.O.C. is 93dB/1W/1M down to below 50 Hz, but HornResp predicts it will run out of excursion in the passband with only 4W of input (I assumed 3mm Xmax).
Tapped pipes and simple tapped horns are just TLs folded back on itself which are 6th order BPs stretched to their logical extreme and if you add filter chambers they become 8th order, same as a Karlson K15. What I perceive as a true tapped horn adheres to Prof. Leach's compression horn theory, so to understand them combined with the other is to understand TH theory, at least it seems to for me.
GM
GM
As GM points out, "Tapped Horns" are not really horns. They are "quarter and half wave" resonators. They work more like organ pipes than horns. Some people consider them to be "transmission lines", but TLs have a very different set of design objectives to tapped horns.
I gained an understanding of the theory by using pencil and paper.
I drew a pipe with an open end and plotted the maxima and minima of the waves in the pipe for both quarter and half wave resonances.
It should be possible to illustrate the same thing with the ripple tank simulator (http://www.falstad.com/). I'll see if I can work up a model.
I gained an understanding of the theory by using pencil and paper.
I drew a pipe with an open end and plotted the maxima and minima of the waves in the pipe for both quarter and half wave resonances.
It should be possible to illustrate the same thing with the ripple tank simulator (http://www.falstad.com/). I'll see if I can work up a model.
Gettin' warmer.
GM and Don -
1. Strange, why are there often 3 impedance peaks measured? What are the driver impedance (cone motion) peaks towards the bottom, how do these relate to wave/length/phase, and how to these relate to sound output?
2. How do you account for the high sound output (comparable the the enclosure-reinforcing levels you talk about) but found far north of them from say, 120 to 200 Hz?
Many thanks for your help... I am sure others appreciate it too.
GM and Don -
1. Strange, why are there often 3 impedance peaks measured? What are the driver impedance (cone motion) peaks towards the bottom, how do these relate to wave/length/phase, and how to these relate to sound output?
2. How do you account for the high sound output (comparable the the enclosure-reinforcing levels you talk about) but found far north of them from say, 120 to 200 Hz?
Many thanks for your help... I am sure others appreciate it too.
The answer to all of your questions is... resonances. Multiple resonances.
Tom Danley's simple explanation goes like this:
For a classic front loaded "horn" (really, a pipe), you get good output at the lowest resonance, then a dip, then another peak. Adding the output from the rear of the driver to the other end of the horn/pipe excites a pipe resonance which fills in the dip.
You can see this for yourself with Hornresp. You will need:
- Hornresp.
- Volvotreter's tapped horn page: Tapped Horns
Start Hornresp.
On Volvotreter's page, scroll down to the Tangband 38Hz Tapped Horn.
Enter the parameters from his page into Hornresp and press "calculate".
If you've done it right, the SPL response picture should look exactly like his example.
Check the displacement and impedance curves too. Note that there are 3 peaks. This is because the pipe has multiple resonances, not just the fundamental.
Now remove the "tap" by changing from "Tapped Horn" to "Offset Driver".
To do this, use the input box at the lower right of the input panel. Either double-click on the "TH" until it cycles through to "OD", or double-click on the input box itself and select "Offset Driver" from the selection box.
Press "Calculate" and note that you have:
- A peak at 45 Hz
- A dip at 70 Hz
- A peak at 120 Hz.
Select Tools --> Compare Previous (or press F4), which will plot the Tapped Horn response behind the Offset Driver response. You can see how the dip is filled in. The dip at 170 Hz is worse with the tapped horn, because the 2 resonances excited by the 2 drivers are out of phase at that point.
Also check the impedance and displacement curves. Note that they are quite similar for both TH and OD configurations. In other words, the TH arrangement can give you a significantly better SPL response without adding much to the stress on the driver or amplifier.
For your second question, the higher order resonances cause the high output at higher frequencies. Many people have found that when you actually build the speaker, the resonances are much less pronounced than they are in the simulations. The simulations usually assume a perfect driver (suitable for fullrange use) and no losses in the enclosure.
Tom Danley's simple explanation goes like this:
For a classic front loaded "horn" (really, a pipe), you get good output at the lowest resonance, then a dip, then another peak. Adding the output from the rear of the driver to the other end of the horn/pipe excites a pipe resonance which fills in the dip.
You can see this for yourself with Hornresp. You will need:
- Hornresp.
- Volvotreter's tapped horn page: Tapped Horns
Start Hornresp.
On Volvotreter's page, scroll down to the Tangband 38Hz Tapped Horn.
Enter the parameters from his page into Hornresp and press "calculate".
If you've done it right, the SPL response picture should look exactly like his example.
Check the displacement and impedance curves too. Note that there are 3 peaks. This is because the pipe has multiple resonances, not just the fundamental.
Now remove the "tap" by changing from "Tapped Horn" to "Offset Driver".
To do this, use the input box at the lower right of the input panel. Either double-click on the "TH" until it cycles through to "OD", or double-click on the input box itself and select "Offset Driver" from the selection box.
Press "Calculate" and note that you have:
- A peak at 45 Hz
- A dip at 70 Hz
- A peak at 120 Hz.
Select Tools --> Compare Previous (or press F4), which will plot the Tapped Horn response behind the Offset Driver response. You can see how the dip is filled in. The dip at 170 Hz is worse with the tapped horn, because the 2 resonances excited by the 2 drivers are out of phase at that point.
Also check the impedance and displacement curves. Note that they are quite similar for both TH and OD configurations. In other words, the TH arrangement can give you a significantly better SPL response without adding much to the stress on the driver or amplifier.
For your second question, the higher order resonances cause the high output at higher frequencies. Many people have found that when you actually build the speaker, the resonances are much less pronounced than they are in the simulations. The simulations usually assume a perfect driver (suitable for fullrange use) and no losses in the enclosure.
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