Jmmlc said:
Hi Jean-Michel,
The measured acoustical impedance results were taken from the dissertation by John Theodore Post titled: “A Modeling and Measurement Study of Acoustic Horns”. The dissertation was presented to the Faculty of the Graduate School of the University of Texas at Austin in partial fulfillment of the requirements for the degree of Doctor of Philosophy. The document is copyrighted, and is dated May 1994.
Kind regards,
David
HORNRESP VERSION 19.20
Hi Everyone,
Just letting you know that the Hornresp Tapped Horn Wizard tool has been further enhanced. Throat and mouth areas can now be adjusted from within the tool. Version 19.20 refers.
Please note that each time one of the area sliders is moved to the far right-hand side, the range of all area sliders is automatically increased by 1000 sq cm. The range is also automatically decreased as appropriate to maintain maximum control sensitivity.
THREE SEGMENT TAPPED HORNS
Before selecting the TH Wizard:
1. Set L12 + L23 + L34 to the required overall tapped horn length.
2. Set L23 to the required tapped horn flare (Con or Exp).
Note that the operation of L34 slider has been reversed with the new release. The minimum value is now on the right-hand rather than the left-hand side of the slide control.
FOUR SEGMENT TAPPED HORNS
Before selecting the TH Wizard:
1. Set L12 + L23 + L34 + L45 to the required overall tapped horn length. Note that the position of S3 is specified by L12 + L23 and L34 + L45 and is fixed relative to S1 and S5.
2. Set L23 and L34 to the two required tapped horn flares (Con and/or Exp).
Note that the operation of L45 slider has been reversed with the new release. The minimum value is now on the right-hand rather than the left-hand side of the slide control.
As always, please do not hesitate to advise me either by e-mail or by posting to this forum, if you find any bugs in Hornresp (no matter how trivial they may seem to you).
My thanks go to Erik (‘Volvotreter’) for encouraging me to include this new feature.
Kind regards,
David
Hi Everyone,
Just letting you know that the Hornresp Tapped Horn Wizard tool has been further enhanced. Throat and mouth areas can now be adjusted from within the tool. Version 19.20 refers.
Please note that each time one of the area sliders is moved to the far right-hand side, the range of all area sliders is automatically increased by 1000 sq cm. The range is also automatically decreased as appropriate to maintain maximum control sensitivity.
THREE SEGMENT TAPPED HORNS
Before selecting the TH Wizard:
1. Set L12 + L23 + L34 to the required overall tapped horn length.
2. Set L23 to the required tapped horn flare (Con or Exp).
Note that the operation of L34 slider has been reversed with the new release. The minimum value is now on the right-hand rather than the left-hand side of the slide control.
FOUR SEGMENT TAPPED HORNS
Before selecting the TH Wizard:
1. Set L12 + L23 + L34 + L45 to the required overall tapped horn length. Note that the position of S3 is specified by L12 + L23 and L34 + L45 and is fixed relative to S1 and S5.
2. Set L23 and L34 to the two required tapped horn flares (Con and/or Exp).
Note that the operation of L45 slider has been reversed with the new release. The minimum value is now on the right-hand rather than the left-hand side of the slide control.
As always, please do not hesitate to advise me either by e-mail or by posting to this forum, if you find any bugs in Hornresp (no matter how trivial they may seem to you).
My thanks go to Erik (‘Volvotreter’) for encouraging me to include this new feature.
Kind regards,
David
Hello David,
As we are into midrangehorns do you have a working model for a 2"-driver? Jean-Michel has kindly supported with a 1" TAD 2001 but I am not sure that my attempt to convert it to JBL 375/2441 is reliable .
Saw you also have a new version up, will install and enjoy!
Greetings from Sweden!
Jmmlc said:
Hi Jean-Michel,
The attachment below compares Hornresp predictions for the throat acoustical impedance of the tractrix horn measured by John Post against the throat acoustical impedance of a conical horn having the same throat area, mouth area and axial length as the measured tractrix horn. The red and black traces apply to the conical horn, the pink and grey traces apply to the tractrix horn.
We already know that predicted and measured results for the tractrix horn compare quite favourably. The same outcome is likely to be the case for the conical horn.
This means that there will be a noticeable difference at lower frequencies between the throat acoustical impedance of a conical horn when compared to a tractrix horn of similar dimensions. This lends support to the contention that the statement in question does not hold up in all situations
.Kind regards,
David
Attachments
Hi Jean-Michel,
I had a discussion with Earl on loading, efficiency and displacement a while ago here.
Earl's experience seems to be (from what I can see from the AES papers he has published) with mid/high frequency horns, and the exponential horns he has inverstigated seems to have been poorly executed designs. He does not seem to have much experiencie (if any) with bass horns.
One point that I didn't make in the thread linked to above, is that the effects that loading has on displacement does not depend on efficiency, which Earl seems to believe. The relation is like this: Power radiated equals the squared magnitude of the throat volume velocity times the resistive part of the acoustic load impedance (Ra):
Pout = |U|^2 * Ra
Since the volume velocity U equals the diaphragm velocity times the diaphragm area, and diaphragm displacement equals diaphragm velocity divided by 2*Pi*f, we get the relation for peak displacement:
d = sqrt(2*Pout/[(2*Pi*f)^2 * Ra])
So for a given power output, displacement increases as 1/sqrt(Ra).
In the thread linked to, I also show the difference between a big hyperbolic (T=0.65) horn (post #95), and a conical horn of the exact same length and mouth/throat areas. The difference is obvious.
Also note that when using horns with different loading properties on the same driver, just comparing SPL response and diaphragm displacement with the same input to the system does not show the real difference. Different acoustic loading translates to differences in power drawn from the amplifier, and differences in efficiency. The horns should really be equalized to the same power response to truly see the how the changes affect performance.
In the frequency range where Earl uses horns/waveguides (above 800Hz), the differences will be less than for bass horns, since the driver will mostly work in its mass-controlled range. The horns are also usually quite small and rapidly flaring. Directivity also gets increasingly more pronounced.
That there is a difference in loading between different profiles is easily measured. That the differences does not translate to a difference great enought for Earl to consider them important (in the frequency range he is concerned about) does not change that fact. Neither that the Webster horn equation is not 100% accurate. The physical fact is that slower flaring horns do present a high resistive impedance down to a lower frequency than a rapidly flaring horn.
An example: Many years ago I built a clone of the Unity horn. The measured throat impedance of this horn (where the HF driver attaches) was exactly as Hornresp predicted, and started to fall below about 10kHz. Later I reworked the horn, so it now has an about 20 cm long exponential section before the conical section. Loading is now high down to about 5-600Hz. This by adding a slow flaring throat part.
Attached is the measured and simulated throat impedance of a similar horn.
Best regards,
Bjørn
I had a discussion with Earl on loading, efficiency and displacement a while ago here.
Earl's experience seems to be (from what I can see from the AES papers he has published) with mid/high frequency horns, and the exponential horns he has inverstigated seems to have been poorly executed designs. He does not seem to have much experiencie (if any) with bass horns.
One point that I didn't make in the thread linked to above, is that the effects that loading has on displacement does not depend on efficiency, which Earl seems to believe. The relation is like this: Power radiated equals the squared magnitude of the throat volume velocity times the resistive part of the acoustic load impedance (Ra):
Pout = |U|^2 * Ra
Since the volume velocity U equals the diaphragm velocity times the diaphragm area, and diaphragm displacement equals diaphragm velocity divided by 2*Pi*f, we get the relation for peak displacement:
d = sqrt(2*Pout/[(2*Pi*f)^2 * Ra])
So for a given power output, displacement increases as 1/sqrt(Ra).
In the thread linked to, I also show the difference between a big hyperbolic (T=0.65) horn (post #95), and a conical horn of the exact same length and mouth/throat areas. The difference is obvious.
Also note that when using horns with different loading properties on the same driver, just comparing SPL response and diaphragm displacement with the same input to the system does not show the real difference. Different acoustic loading translates to differences in power drawn from the amplifier, and differences in efficiency. The horns should really be equalized to the same power response to truly see the how the changes affect performance.
In the frequency range where Earl uses horns/waveguides (above 800Hz), the differences will be less than for bass horns, since the driver will mostly work in its mass-controlled range. The horns are also usually quite small and rapidly flaring. Directivity also gets increasingly more pronounced.
That there is a difference in loading between different profiles is easily measured. That the differences does not translate to a difference great enought for Earl to consider them important (in the frequency range he is concerned about) does not change that fact. Neither that the Webster horn equation is not 100% accurate. The physical fact is that slower flaring horns do present a high resistive impedance down to a lower frequency than a rapidly flaring horn.
An example: Many years ago I built a clone of the Unity horn. The measured throat impedance of this horn (where the HF driver attaches) was exactly as Hornresp predicted, and started to fall below about 10kHz. Later I reworked the horn, so it now has an about 20 cm long exponential section before the conical section. Loading is now high down to about 5-600Hz. This by adding a slow flaring throat part.
Attached is the measured and simulated throat impedance of a similar horn.
Best regards,
Bjørn
Attachments
Fantastic to see the new changes to hornresp. I had a look at the tapped horn wizard. I notice that it now has a max spl feature which is very handy. I also notice that it appears to predict a greater SPL than before.
I entered in a big 20 Hz horn with two older AE speakers AV12s. It's telling me it can hit almost 150 db in the midbass with the Behringer EP2500 amp! Two drivers. 2.7m high x 0.5m mouth.
If I put it in the tapped horn I can squeeze out more like 130 db.
In a vented box with WinISD I get 120 db.
I thought a TH only gets more output than vented due to being able to feed in more power, since excursion is roughly halved but efficiency isn't improved. Or am I mistaken?
If this is the case, then a TH should only get more output where the driver is able to handle more power thermally.
This would suggest that to really get the benefit, a typical sub driver won't be suitable. It will be thermally limited. A typical pro driver with very high thermal power handling and high efficiency and not so high excursion would seem ideal. Say a 7mm xmax driver.
I entered in a big 20 Hz horn with two older AE speakers AV12s. It's telling me it can hit almost 150 db in the midbass with the Behringer EP2500 amp! Two drivers. 2.7m high x 0.5m mouth.
If I put it in the tapped horn I can squeeze out more like 130 db.
In a vented box with WinISD I get 120 db.
I thought a TH only gets more output than vented due to being able to feed in more power, since excursion is roughly halved but efficiency isn't improved. Or am I mistaken?
If this is the case, then a TH should only get more output where the driver is able to handle more power thermally.
This would suggest that to really get the benefit, a typical sub driver won't be suitable. It will be thermally limited. A typical pro driver with very high thermal power handling and high efficiency and not so high excursion would seem ideal. Say a 7mm xmax driver.
Sabbelbacke said:
Can´t find it in the wizards dialog. Is it hidden? Just downloaded the recent build.
Maybe I need more coffee
Hi Sabbelbacke,
I can't find it in the Tapped Horn Wizard either
.I think that Paul is probably just using the Maximum SPL tool in conjunction with the TH Wizard tool.
Perhaps he could do with some of your coffee
.Kind regards,
David
G'day Paul
That's the conclusion I have come to as well. I recently built a pair of 32Hz tapped horns using Peerless XLS 12" drivers for a friend. When pushed you could smell the voice coils, yet excusion was less than half what these drivers are capable of. The extra excursion does buy you quite a bit of protection below cut off.
I'm going to have a play with some 4" coil pro drivers with a lower x-max and see how they go.
David, your little program keeps getting better and better. I'm so glad the goup has been able to keep you motivated!
Cheers
William Cowan
That's the conclusion I have come to as well. I recently built a pair of 32Hz tapped horns using Peerless XLS 12" drivers for a friend. When pushed you could smell the voice coils, yet excusion was less than half what these drivers are capable of. The extra excursion does buy you quite a bit of protection below cut off.
I'm going to have a play with some 4" coil pro drivers with a lower x-max and see how they go.
David, your little program keeps getting better and better. I'm so glad the goup has been able to keep you motivated!
Cheers
William Cowan
Yes, Paul was using both tools, it was quite clever of him don't you think?! After you have run calcs, the max SPL option comes up. I used to just keep increasing the input until I went beyond what my amp could do or max excursion was predicted. Now I reach that point much quicker.
William,
This makes me wonder what driver is best for a sub tapped horn. I start to think of a pro driver with 7mm xmax and 95db sensitivity. If you look at Danley's tower of power, 1000 watts at 95 db sensitivity gets 125 db down to 18 Hz. If the horn itself does not boost sensitivity, how do you get a 12" driver which would normally only go to about 40 Hz to reach down to 18 Hz?
I've had a play with a pro driver - Beyma 12" SM212 with 7mm xmax and it can pump out 125db but it won't go below 30 Hz. It only needs 50w to hit that level in a corner. While that sounds decent, I can get more output out of an AV12 drivers and deeper extension with more power.
I'm having a look at this again since I'm looking at how I can squeeze the most out of that pair of AV12 drivers for a home theatre for a friend. If my friend is happy with the idea, he might actually go for that huge 20 Hz bass horn that I was hoping to build in the past but didn't when I found the room really wasn't big enough, and I have neighbour issues! My friend could actually use the thing. So it's a choice between vented, tapped or horn. But now I'm getting off topic!
William,
This makes me wonder what driver is best for a sub tapped horn. I start to think of a pro driver with 7mm xmax and 95db sensitivity. If you look at Danley's tower of power, 1000 watts at 95 db sensitivity gets 125 db down to 18 Hz. If the horn itself does not boost sensitivity, how do you get a 12" driver which would normally only go to about 40 Hz to reach down to 18 Hz?
I've had a play with a pro driver - Beyma 12" SM212 with 7mm xmax and it can pump out 125db but it won't go below 30 Hz. It only needs 50w to hit that level in a corner. While that sounds decent, I can get more output out of an AV12 drivers and deeper extension with more power.
I'm having a look at this again since I'm looking at how I can squeeze the most out of that pair of AV12 drivers for a home theatre for a friend. If my friend is happy with the idea, he might actually go for that huge 20 Hz bass horn that I was hoping to build in the past but didn't when I found the room really wasn't big enough, and I have neighbour issues! My friend could actually use the thing. So it's a choice between vented, tapped or horn. But now I'm getting off topic!
Try modeling the Eminence Definimax 4012 in your 30Hz TH. I found it works rather well, it only really runs low on xmax below 30Hz and maybe around 40Hz also. It also has a 4" voicecoil, and it doesn't get hot when pushed, but I didn't put more than 300W into mine.cowanaudio said:
In fact I've been playing around with the "Active EQ"on my DCX2496, and found it can limit different amounts at different frequencies.
I've been using Hornresp with various voltages to find where my driver will run out of xmax at different frequencies... I was thinking it would be really to have a voltage plot on the "Max SPL" curve. Would this be possible?
So I put in say 5mm xmax, 300W power, and hornresp would produce a voltage curve as well as an SPL one. Perhaps the scale for voltage could be on the right have side and the curve itseld could be a different colour so it won't get mixed up with the SPL curve?
I'm not sure if this is possible as I'm not really sure quite how all the maths behind this works... but if it is that would be a great feature IMO.
MikeHunt79 said:
Try modeling the Eminence Definimax 4012 in your 30Hz TH. I found it works rather well, it only really runs low on xmax below 30Hz and maybe around 40Hz also. It also has a 4" voicecoil, and it doesn't get hot when pushed, but I didn't put more than 300W into mine.
In fact I've been playing around with the "Active EQ"on my DCX2496, and found it can limit different amounts at different frequencies.
I've been using Hornresp with various voltages to find where my driver will run out of xmax at different frequencies... I was thinking it would be really to have a voltage plot on the "Max SPL" curve. Would this be possible?
So I put in say 5mm xmax, 300W power, and hornresp would produce a voltage curve as well as an SPL one. Perhaps the scale for voltage could be on the right have side and the curve itseld could be a different colour so it won't get mixed up with the SPL curve?
I'm not sure if this is possible as I'm not really sure quite how all the maths behind this works... but if it is that would be a great feature IMO.
If a 15" driver will fit try the BMS 15N850, this doesn't run out of Xmax even at 1200W input.
Ian
cowanaudio said:
Hi William,
If you like the current Tapped Horn Wizard tool, then I think you are probably going to love the next enhancement
. It is most likely about a week or so away, if all goes according to plan.I am not sure that I would describe Hornresp as a "little" program though - the source code for Version 19.20 fills over 500 A4 pages when printed out
.Kind regards,
David