Martin has just posted the initial stage of his Lowther project. Includes measurements of T/S and FR of DX2, DX3, & DX4 models.
http://www.quarter-wave.com/Project04/Project04.html
It will be really interesting to see how this project turns out.
dave
http://www.quarter-wave.com/Project04/Project04.html
It will be really interesting to see how this project turns out.
dave
Man, those are expensive driver...
from http://www.lowther-america.com/
DX series
DX2 $695
DX3 $795
DX4 $1700
It will be interesting to see the results. The initial driver measurements look good. It is strange how having the drivers slightly off axis makes them almost perfectly flat.
--
Brian
from http://www.lowther-america.com/
DX series
DX2 $695
DX3 $795
DX4 $1700
It will be interesting to see the results. The initial driver measurements look good. It is strange how having the drivers slightly off axis makes them almost perfectly flat.
--
Brian
Re: Martin has just posted the initial stage of his Lowther project
Now I do not have to write it.
Thanks Mr Dickman
---------------------------------------------
A question:
What happens if I put a Lowther in a normal sealed enclosure?
Why did it have to be horn?
Will I be spitted on, if I do?
Precise my thought.Fred Dieckmann said:
Now I do not have to write it.
Thanks Mr Dickman ---------------------------------------------
A question:
What happens if I put a Lowther in a normal sealed enclosure?
Why did it have to be horn?
Will I be spitted on, if I do?
I wish Martin good luck with his project.
I owe a lot to Martin's TL simulation software. It enabled me to design my TLsub, and it works great.
I was wondering about his design philosophy with 200 watt SS as opposed to low wattage SEamps in order to be able to use passive correction. If you were to use ACTIVE correction would you not be able to have the best of both worlds?
I owe a lot to Martin's TL simulation software. It enabled me to design my TLsub, and it works great.
I was wondering about his design philosophy with 200 watt SS as opposed to low wattage SEamps in order to be able to use passive correction. If you were to use ACTIVE correction would you not be able to have the best of both worlds?
Thanks for the comments. I'll just add a couple of responses to some of the items above.
1) I think that Lowthers will work in a variety of enclosures, if you had a sub I think that a closed box would work well. I have a couple of new worksheets built around my quarter wave equations that will include internal acoustic filters and vibration absorbers so the enclosures I am planning on exploring will not necessarily be easily categorized.
2) Passive vs Active filtering, a couple of thoughts on why I am using passive. First I am not an amp designer or tweaker so putting an active circuit ahead of the amp is a little beyond my experience. Second, I would like my speakers to be self contained, they eventually will have to find new homes so they need to work in whatever system is available. Third, I am designing these speakers to work with a solid state amp so they will not be optimized for a tube amp. If I am using a solid state amp with the higher powers available I do not see any real disadvantage in using a passive set of filters.
3) Martin Lowther King? I guess I have been called worse. There are a whole group of guys that think the fibers move in a TL that are still calling me worse names.
OK, thats my take on things. Thanks again for the feedback.
Martin
www.quarter-wave.com
1) I think that Lowthers will work in a variety of enclosures, if you had a sub I think that a closed box would work well. I have a couple of new worksheets built around my quarter wave equations that will include internal acoustic filters and vibration absorbers so the enclosures I am planning on exploring will not necessarily be easily categorized.
2) Passive vs Active filtering, a couple of thoughts on why I am using passive. First I am not an amp designer or tweaker so putting an active circuit ahead of the amp is a little beyond my experience. Second, I would like my speakers to be self contained, they eventually will have to find new homes so they need to work in whatever system is available. Third, I am designing these speakers to work with a solid state amp so they will not be optimized for a tube amp. If I am using a solid state amp with the higher powers available I do not see any real disadvantage in using a passive set of filters.
3) Martin Lowther King? I guess I have been called worse. There are a whole group of guys that think the fibers move in a TL that are still calling me worse names.
OK, thats my take on things. Thanks again for the feedback.
Martin
www.quarter-wave.com
Sorry, I am not sure I understand your post. I am afraid I am not real sharp and the point you were trying to make zipped right over my head. Could you help me out a little?
Thanks in advance,
Martin
www.quarter-wave.com
Thanks in advance,
Martin
www.quarter-wave.com
Hey Martin check this out
I figured out how to use mathcad and your progam for TL's. I haven't built anything with it, although I read (on your website) that it's been tested and works very well.
I used the "TL open end.mcd" file to design some speakers I thought I was going to build. I noticed that the smaller ratio of driver sd/beginning line sd for a TL using your program the better the preformance according to the graphs is.
You state that 1.25 to 2.5 is normal and the focal's 3.0 is unusual, but every driver I've tried designing a TL for the higher the beginning start line sd/driver sd ratio is the more low end output. Why is this? I also noticed that a taper always hurts low end preformance.
Also that "Bl" spec sucks, many companies don't have one.
I figured out how to use mathcad and your progam for TL's. I haven't built anything with it, although I read (on your website) that it's been tested and works very well.
I used the "TL open end.mcd" file to design some speakers I thought I was going to build. I noticed that the smaller ratio of driver sd/beginning line sd for a TL using your program the better the preformance according to the graphs is.
You state that 1.25 to 2.5 is normal and the focal's 3.0 is unusual, but every driver I've tried designing a TL for the higher the beginning start line sd/driver sd ratio is the more low end output. Why is this? I also noticed that a taper always hurts low end preformance.
Also that "Bl" spec sucks, many companies don't have one.
halojoy,
OK, I think I understand. Thanks for the clarrification.
Jimmy154,
Sounds like you are making progress with my worksheets. Hope you are also having some fun. The reports I have received directly and the postings I see on the various forums all seem to agree that the worksheets are very accurate. However, like any simulation program the quality of the results are directly determined by the quality of the input and the skill of the user.
I am going to try and answer your questions in reverse order.
The first quarter wave resonance of a TL is a function of S0, SL, and L. So if you change S0 and SL, without making the appropriate change in L, you will not get the same first frequency. In other words, if you leave the length the same and adjust the areas you will change the tuning of the line and the bass output will get worse assuming you are moving away from an optimum design. The best place to determine the line tuning frequency is in the acoustic impedance plot in the "TL Open End" worksheet. I have provided an example of this behavior in Section 6.0 : Advanced Modeling Techniques of the TL theory pages. Three TLs with the same volume and length are shown with expanding, tapered, and straight geometries.
I have found that almost every TL I design has a larger area, bigger volume, then the recommendations in most speaker design texts. It seems that the bigger the area the more bass you get.
Looking at Figure 1.1 of Section 1.0 : Introduction on the TL theory page, the acoustic equivalent circuit is shown for a TL with the driver mounted at one end (this circuit is the basis for the worksheet "TL Open End"). The relationship between the air velocity at the terminus and the air velocity at the driver, epsilon, is a function of the shape of the TL (the rate of taper or expansion). So if you know the driver velocity you can calculate the terminus velocity regardless of the absolute size of the TL. The acoustic impedance of the TL, Zal, is a function of the shape of the TL and 1/S0. For example the acoustic impedance of a straight pipe is shown below :
Zal = j (rho c) tan(k L) / S0
As S0 increases the impedance decreases. Now looking at Figure 1.1 again, as Zal decreases then Ud, the driver volume velocity (Ud = Sd ud) increases. If ud increases so does uL. Therefore in general, as the volume of the TL increases the output from the open end also increases. Does that any make sense?
Going back to the equation for the acoustic impedance
Zal = j (rho c) tan(k L) / S0
remember that the tangent goes to infinity at 90 degrees (phi / 2).
k L = phi / 2
k = 2 phi f / c
2 phi f L / c = phi / 2
f = c / (4 L)
This is the quarter wavelength formula for a straight TL. The equation does not work if the line is tapered or expanding. Trying to use this equation on an expanding or tapered TL geometry is the most common mistake people make when trying to size a TL. Be very careful when using this equation!
At this frequency, Zal will peak and as a result Ud will have a minimum just like a bass reflex box. As you add damping the peak of Zal will become shorter and wider and the minimum of Ud will become shallower and wider.
I hope that helps. if you have more questions please do not hesitate to ask.
Martin
www.quarter-wave.com
OK, I think I understand. Thanks for the clarrification.
Jimmy154,
Sounds like you are making progress with my worksheets. Hope you are also having some fun. The reports I have received directly and the postings I see on the various forums all seem to agree that the worksheets are very accurate. However, like any simulation program the quality of the results are directly determined by the quality of the input and the skill of the user.
I am going to try and answer your questions in reverse order.
The first quarter wave resonance of a TL is a function of S0, SL, and L. So if you change S0 and SL, without making the appropriate change in L, you will not get the same first frequency. In other words, if you leave the length the same and adjust the areas you will change the tuning of the line and the bass output will get worse assuming you are moving away from an optimum design. The best place to determine the line tuning frequency is in the acoustic impedance plot in the "TL Open End" worksheet. I have provided an example of this behavior in Section 6.0 : Advanced Modeling Techniques of the TL theory pages. Three TLs with the same volume and length are shown with expanding, tapered, and straight geometries.
I have found that almost every TL I design has a larger area, bigger volume, then the recommendations in most speaker design texts. It seems that the bigger the area the more bass you get.
Looking at Figure 1.1 of Section 1.0 : Introduction on the TL theory page, the acoustic equivalent circuit is shown for a TL with the driver mounted at one end (this circuit is the basis for the worksheet "TL Open End"). The relationship between the air velocity at the terminus and the air velocity at the driver, epsilon, is a function of the shape of the TL (the rate of taper or expansion). So if you know the driver velocity you can calculate the terminus velocity regardless of the absolute size of the TL. The acoustic impedance of the TL, Zal, is a function of the shape of the TL and 1/S0. For example the acoustic impedance of a straight pipe is shown below :
Zal = j (rho c) tan(k L) / S0
As S0 increases the impedance decreases. Now looking at Figure 1.1 again, as Zal decreases then Ud, the driver volume velocity (Ud = Sd ud) increases. If ud increases so does uL. Therefore in general, as the volume of the TL increases the output from the open end also increases. Does that any make sense?
Going back to the equation for the acoustic impedance
Zal = j (rho c) tan(k L) / S0
remember that the tangent goes to infinity at 90 degrees (phi / 2).
k L = phi / 2
k = 2 phi f / c
2 phi f L / c = phi / 2
f = c / (4 L)
This is the quarter wavelength formula for a straight TL. The equation does not work if the line is tapered or expanding. Trying to use this equation on an expanding or tapered TL geometry is the most common mistake people make when trying to size a TL. Be very careful when using this equation!
At this frequency, Zal will peak and as a result Ud will have a minimum just like a bass reflex box. As you add damping the peak of Zal will become shorter and wider and the minimum of Ud will become shallower and wider.
I hope that helps. if you have more questions please do not hesitate to ask.
Martin
www.quarter-wave.com
I thought that Falign automatically alligned the enclosure to the correct length for the frequency specified. SL is the line length, so what those L refer to or vice versa (L is the line length)? Maybe the answer is on your website, I will go read it again later.
"The best place to determine the line tuning frequency is in the acoustic impedance plot in the "TL Open End" worksheet. I have provided an example of this behavior in Section 6.0 : Advanced Modeling Techniques of the TL theory pages." I think I know what you're talking about here, but I will go read the above section again. Before adjusting the Falign I had 2 bumps (one small and one big) which seems like it would be less than optimum.
"It seems that the bigger the area the more bass you get." That's what I was saying about the SD. But T-lines are big enough to begin with, so I would gladly make a sacrifice.
I'm not too good with electronics. I don't really know what impedance (as well as inductance and uF, whatever that is) so I didn't understand what you were talking about in the last half of your post. I guess will will have to look into that someday.
I still have a lot to learn about the basics and that's my main problem. I have only built one pair of speakers and they aren't even done yet. I'm waiting for some one with the same speakers to finish designing their XO's so I can copy them, so that gives you an idea of my compitence. http://www.t-linespeakers.org was one of the first sites I came across about speaker building a years ago. And I downloaded your software a year ago, but it was too confusing at that time. It came up on this forum, so I decided to d/l it again. And this time I had enough knowlegde to at least make it work and kind of understand it. I wish I got your program to work before I started this pair.
"The best place to determine the line tuning frequency is in the acoustic impedance plot in the "TL Open End" worksheet. I have provided an example of this behavior in Section 6.0 : Advanced Modeling Techniques of the TL theory pages." I think I know what you're talking about here, but I will go read the above section again. Before adjusting the Falign I had 2 bumps (one small and one big) which seems like it would be less than optimum.
"It seems that the bigger the area the more bass you get." That's what I was saying about the SD. But T-lines are big enough to begin with, so I would gladly make a sacrifice.
I'm not too good with electronics. I don't really know what impedance (as well as inductance and uF, whatever that is) so I didn't understand what you were talking about in the last half of your post. I guess will will have to look into that someday.
I still have a lot to learn about the basics and that's my main problem. I have only built one pair of speakers and they aren't even done yet. I'm waiting for some one with the same speakers to finish designing their XO's so I can copy them, so that gives you an idea of my compitence. http://www.t-linespeakers.org was one of the first sites I came across about speaker building a years ago. And I downloaded your software a year ago, but it was too confusing at that time. It came up on this forum, so I decided to d/l it again. And this time I had enough knowlegde to at least make it work and kind of understand it. I wish I got your program to work before I started this pair.
Jimmy154,
I am not sure which version of my software you are working with but I recommend that you download the latest version from my website. I have tried to do a better job at making the input easier and labeling the variables required. From the "TL Open End" worksheet you will find that the only things you need to enter for the TL geometry are :
L = length
S0 = area at driver end
SL = area at open end
Density = stuffing density
Everything else is assigned automatically. In almost all of my worksheets the user only needs to enter the data on the first page ("TL Sections" is one exception). The acoustic impedance curve for the TL is the very first curve plotted. The magnitude is the top graph and the first hump or peak occurs at the tuning frequency for the line.
Martin
www.quarter-wave.com
I am not sure which version of my software you are working with but I recommend that you download the latest version from my website. I have tried to do a better job at making the input easier and labeling the variables required. From the "TL Open End" worksheet you will find that the only things you need to enter for the TL geometry are :
L = length
S0 = area at driver end
SL = area at open end
Density = stuffing density
Everything else is assigned automatically. In almost all of my worksheets the user only needs to enter the data on the first page ("TL Sections" is one exception). The acoustic impedance curve for the TL is the very first curve plotted. The magnitude is the top graph and the first hump or peak occurs at the tuning frequency for the line.
Martin
www.quarter-wave.com
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