I hope at the end of this thread, a few types of compact transmission line enclosures will be put forward so several of us can build and test standard and maybe innovative new designs. After a robust discussion, I, being an MSExcel programmer, will download all posts and make a readable, searchable guide. This guide will be parsed into different sections: Design types (folded, spiral, helix, etc), structure (MDF, PVC tubes, foamcore, etc) , speaker selection, electronics (baffle step and EQ), stuffing, prototyping and final construction.
I suggest, (but what do I know), that we start off using these parameters to narrow the focus:
1. Tapered Mass loaded quarter wave ( ML-TW ) as I think it is generally accepted that this type of T-Line enclosure is the most compact – if not, then feel free to add your transmission line type to the discussion.
2. Near field so SPL is not as much of an issue
3. If a design requires, use a baffle step and/or moderate EQ
4. To make it interesting, let’s see how we can make it somewhat adjustable to handle using similar 3 and 4 inch, high QTS (>.38), low Fs and low VAS drivers.
5. And to have a reference driver so we can somewhat compare designs, let’s go with a $22 AuraSound NS3-193 = Fs=80, QTS = .67, Sd=31 cm2, vas=.0441 cuft, Xmax=4.25.
To start off, here are some questions I have (which shows my lack of knowledge, therefore this post
I suggest, (but what do I know), that we start off using these parameters to narrow the focus:
1. Tapered Mass loaded quarter wave ( ML-TW ) as I think it is generally accepted that this type of T-Line enclosure is the most compact – if not, then feel free to add your transmission line type to the discussion.
2. Near field so SPL is not as much of an issue
3. If a design requires, use a baffle step and/or moderate EQ
4. To make it interesting, let’s see how we can make it somewhat adjustable to handle using similar 3 and 4 inch, high QTS (>.38), low Fs and low VAS drivers.
5. And to have a reference driver so we can somewhat compare designs, let’s go with a $22 AuraSound NS3-193 = Fs=80, QTS = .67, Sd=31 cm2, vas=.0441 cuft, Xmax=4.25.
To start off, here are some questions I have (which shows my lack of knowledge, therefore this post
- Will the volume be about the same in all Ml-TW enclosure types using the same driver parameters, ie, box, cylinder, spiral, cornu, etc?
- How important is the smoothness of the “tunnel” when listening to normal music, iestraight, vs folded with 45’s in the corners, vs spiral?
- Based on the law of diminishing returns, how much will placing a driver at the end of the tunnel and using stuffing, effect normal music vs placing the driver about 1/3 of the way into the tunnel and using stuffing?
- And is it feasible to make a cylinder transmission line out of cardboard or PVC pipe?
A few snippets.
Small & TL usually do not go together.
A heavily tapered line will be smaller than a straight (no) taper or expanding taper. ML-TL might be smaller (certainly they tend to be shorter)
Typically a TL is done to use some of the rear radiation to enhance the bass. The pipe has a series of resonances, you want to supress all but the lowest of them. This is done with damping, driver offset in the line to supress the 1st unwanted harmonic, allowing the use of less damping and thus retaining more of the desired fundamental. A bend in the pipe (without a 45) increases of cross-section of the pipe around the bend which acts as a low-pass filter (ie the 45 is counter productive except for acting as a brace).
It is certainly possible to use a cyclindrical pipe for a TL — the LFs don’t really care what shape the pipe is since their wavelengths are much larger than the pipe cross-section.
It is not a good idea to tune the peipe below (root(2)/2)*Fs.
A TL should be designed for the target driver… ultimate size is determined by Fs, Qt, Vas so a generalized line is not very fruitful.
dave
Small & TL usually do not go together.
A heavily tapered line will be smaller than a straight (no) taper or expanding taper. ML-TL might be smaller (certainly they tend to be shorter)
Typically a TL is done to use some of the rear radiation to enhance the bass. The pipe has a series of resonances, you want to supress all but the lowest of them. This is done with damping, driver offset in the line to supress the 1st unwanted harmonic, allowing the use of less damping and thus retaining more of the desired fundamental. A bend in the pipe (without a 45) increases of cross-section of the pipe around the bend which acts as a low-pass filter (ie the 45 is counter productive except for acting as a brace).
It is certainly possible to use a cyclindrical pipe for a TL — the LFs don’t really care what shape the pipe is since their wavelengths are much larger than the pipe cross-section.
It is not a good idea to tune the peipe below (root(2)/2)*Fs.
A TL should be designed for the target driver… ultimate size is determined by Fs, Qt, Vas so a generalized line is not very fruitful.
dave
FWIW, inverse tapered are normally for when an alignment requires an unacceptably long vent, so would be for low Vas, Qts drivers, medium Qts = constant taper, high Qts = expanding taper. Your example then spans medium-high Qts.
GM
My goal is to have as close of a conscience possible (ha) the smallest size enclosure for a 40hz f3 near field environment. So let's focus on two things, for now, the driver and the type of enclosure.
1. I'm putting forth the driver= AuraSound NS3-193 = Fs=80, QTS = .67, Sd=31 cm2, vas=.0441 cuft, Xmax=4.25 but let's open it up for suggestions, let's say under $25. After some discussion, we will have to choose one, or maybe two to build and compare.
2. While we are discussing the driver, are we pretty much limited to ML-TW for the most compact transmission line. If not, what transmission type would give the smallest volume?
scott
1. I'm putting forth the driver= AuraSound NS3-193 = Fs=80, QTS = .67, Sd=31 cm2, vas=.0441 cuft, Xmax=4.25 but let's open it up for suggestions, let's say under $25. After some discussion, we will have to choose one, or maybe two to build and compare.
2. While we are discussing the driver, are we pretty much limited to ML-TW for the most compact transmission line. If not, what transmission type would give the smallest volume?
scott
Focusing in on the enclosure, we need the line length on a straight T-Line to be about 84" but that should be less in a ML-TW so what would that be assuming that stuffing probably doesn't decrease the line length much, but the taper should?
Staying with 84", if we assume at the top a 4x4 area and a taper of 10 to 1, we end up with a line volume about 750 cu in or a box, without speaker/line/bracing partitions = box somewhat larger than 12x4x16.
Keeping the driver under $25, what about compound/isobaric - two HiVi B3n at $10 and Fs=77, qts=.86 and vas=.04cuft. That will not lower the length but it does cut the CSA, and therefore the line volume of the box from 750 to about 400 with adding back the extra speaker volume.
I think we might be able to do it = 40 hz near field in a 12 x 5 x 16 box, maybe even in the 30s. What do you think?
Staying with 84", if we assume at the top a 4x4 area and a taper of 10 to 1, we end up with a line volume about 750 cu in or a box, without speaker/line/bracing partitions = box somewhat larger than 12x4x16.
Keeping the driver under $25, what about compound/isobaric - two HiVi B3n at $10 and Fs=77, qts=.86 and vas=.04cuft. That will not lower the length but it does cut the CSA, and therefore the line volume of the box from 750 to about 400 with adding back the extra speaker volume.
I think we might be able to do it = 40 hz near field in a 12 x 5 x 16 box, maybe even in the 30s. What do you think?
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Well, it takes 'x' amount of net volume [Vb] to make 'y' gain bandwidth [BW] with the taper governing the amount of passband 'ripple', hence amount of damping required, so in theory they will all be the same size volume wise, though not quite the same performance. Not many 'free lunches' in speaker design.
As tuning [Fp] goes down in frequency, the driver must have a lower Qts' for a given HF mass corner [2*Fs/Qts'], i.e. wider BW; conversely, a higher Qts' is desirable for a 'sub' system to limit its BW.
Qts' = Qts + any added series resistance: mh-audio.nl - Home
IIRC, the balance between size, gain BW = 0.312 Qts'.
All that said, mass loaded TLs [MLTL] typically are the smallest, best overall performing for 'full-range' apps as they have much less passband 'ripple' plus the vent's added gain BW.
You can do your own comparisons using MJK's most excellent Classic TL Alignment Tables and its companion Excel SS:
http://www.quarter-wave.com/TLs/Alignment_Tables.pdf
http://www.quarter-wave.com/TLs/Alignment_Tables_Calculator_3_3_09.xls
GM
As tuning [Fp] goes down in frequency, the driver must have a lower Qts' for a given HF mass corner [2*Fs/Qts'], i.e. wider BW; conversely, a higher Qts' is desirable for a 'sub' system to limit its BW.
Qts' = Qts + any added series resistance: mh-audio.nl - Home
IIRC, the balance between size, gain BW = 0.312 Qts'.
All that said, mass loaded TLs [MLTL] typically are the smallest, best overall performing for 'full-range' apps as they have much less passband 'ripple' plus the vent's added gain BW.
You can do your own comparisons using MJK's most excellent Classic TL Alignment Tables and its companion Excel SS:
http://www.quarter-wave.com/TLs/Alignment_Tables.pdf
http://www.quarter-wave.com/TLs/Alignment_Tables_Calculator_3_3_09.xls
GM
FWIW, trying to do LF in a small box is going to be the realm of passive radiators.
Trying to get that much pathway (via a long port or TL) will result in very small cross-sectional areas, giving volume-dependent losses in the bass.
PRs are flexible with tuning, and don't need internal dividers - you'll maximise internal volume for more LF gain.
Chris
Trying to get that much pathway (via a long port or TL) will result in very small cross-sectional areas, giving volume-dependent losses in the bass.
PRs are flexible with tuning, and don't need internal dividers - you'll maximise internal volume for more LF gain.
Chris
Yes, you are correct and I have a bunch of PR's (12) and a MS-80 system that uses a WOOX PR in a 220 cu in box and hits 50 hz. But let's see how small we can take a tapered MLqwTL to hit f3 40 hz or lower.
I have done some calculations and it seems with the AURA driver above, we can get the line around 250 cu in. If we wanted just a woofer, we could use the Tangband w3-2108 (double the money) and get it to about 130 cu in and hit 42 hz with a 10:1 taper. But, I'm wondering if, with that line volume, if the box is capable of having a line that is long enough (about 45 inches?) However, we want to use a full range driver.
Also, I can't seem to find a T-line tapered calculator/program that uses VAS and not the SD, which I think is the old way to figure the CSA of the line.
I have done some calculations and it seems with the AURA driver above, we can get the line around 250 cu in. If we wanted just a woofer, we could use the Tangband w3-2108 (double the money) and get it to about 130 cu in and hit 42 hz with a 10:1 taper. But, I'm wondering if, with that line volume, if the box is capable of having a line that is long enough (about 45 inches?) However, we want to use a full range driver.
Also, I can't seem to find a T-line tapered calculator/program that uses VAS and not the SD, which I think is the old way to figure the CSA of the line.
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All the accurate modelers use Vas. Martin King used Sd in his Mathcad sheets as a unit of area but it does nothing & just confuses things.
dave
Does anyone know where do we can find the programs that use VAS or QTS as a way to decide the line length or vol. I assume that the line length begins with the quarter wave length of the F3 that you want but it probably will be shorter than that. And I assume that the combination of the Qts and Vas will decide the vol but not the line length is that correct?
There are several real active experts on this forum. It would be nice, if they have the time, to give us their insights and show how they would design, from the beginning, the most compact ML-Tqwt to hit 40Hz using either the 3 inch AURA or the Dayton ND91-4.
Let me throw out some ideas to get the juices flowing:
1. What about a 3d printed spiral helicord slipped into a 3" tube with the driver in a Tee about 1/3 of the way from the closed end?
2. How about an inline circuit before the amp that has a variable BSC ( I have the circuit for that) and a limit under 35 Hz?
3. How about a separator "board" within the pipe to vary the taper ratio from .5 to .1 to see if we can live with more ripples from the .5 to get more bass output?
Let's see if we can get this step by step design going.
scott
There are several real active experts on this forum. It would be nice, if they have the time, to give us their insights and show how they would design, from the beginning, the most compact ML-Tqwt to hit 40Hz using either the 3 inch AURA or the Dayton ND91-4.
Let me throw out some ideas to get the juices flowing:
1. What about a 3d printed spiral helicord slipped into a 3" tube with the driver in a Tee about 1/3 of the way from the closed end?
2. How about an inline circuit before the amp that has a variable BSC ( I have the circuit for that) and a limit under 35 Hz?
3. How about a separator "board" within the pipe to vary the taper ratio from .5 to .1 to see if we can live with more ripples from the .5 to get more bass output?
Let's see if we can get this step by step design going.
scott
My MTM MLTL design with AuraSound NS3 have been well received over the past 10-11 years. Some links include:
DIY Dayton - List what you're bringing - Techtalk Speaker Building, Audio, Video Discussion Forum
http://www.diyaudio.com/forums/full-range/101415-aura-ns3-193-8a.html
Jim Griffin's Aura T-line 2-way - Techtalk Speaker Building, Audio, Video Discussion Forum
Several folks built clones of this design if you search enough.
My design does not use a taper but it has a low CSA tower so it is very small.
DIY Dayton - List what you're bringing - Techtalk Speaker Building, Audio, Video Discussion Forum
http://www.diyaudio.com/forums/full-range/101415-aura-ns3-193-8a.html
Jim Griffin's Aura T-line 2-way - Techtalk Speaker Building, Audio, Video Discussion Forum
Several folks built clones of this design if you search enough.
My design does not use a taper but it has a low CSA tower so it is very small.
Thanks Jim and Dave,
I went to all the sites, read about the Aura project and installed LA software.
The information was interesting. However, I know with the coming together of many experts like yourselves (you'll are great contributors across the forums) and others like you'll , Xrk971, Cochleus, Cal Weldon, etc together, can design a more compact tapered t-line than the current tall designs, ie, maybe thinner and lighter materials, some different electronics, spiral construction, etc. I believe we can get to a "portable" tapered line that can reach to 40 hz - maybe with an amp inside with some BSC/EQ in-line circuitry before the amp that doesn't require speaker's passive xover components. Some of my calculations seem to suggest that the vol of the tunnel can be from 130 cu in to 250 with a 10:1 taper.
Before we get into the weeds, let's get a discussion going and settle on the driver that will give us the best shot of a small enclosure that will hit f3 of 40 hz. After that, we will tackle the enclosure, the length, the material, the folded tunnel, etc.
Let's have a go at it.
scott
I went to all the sites, read about the Aura project and installed LA software.
The information was interesting. However, I know with the coming together of many experts like yourselves (you'll are great contributors across the forums) and others like you'll , Xrk971, Cochleus, Cal Weldon, etc together, can design a more compact tapered t-line than the current tall designs, ie, maybe thinner and lighter materials, some different electronics, spiral construction, etc. I believe we can get to a "portable" tapered line that can reach to 40 hz - maybe with an amp inside with some BSC/EQ in-line circuitry before the amp that doesn't require speaker's passive xover components. Some of my calculations seem to suggest that the vol of the tunnel can be from 130 cu in to 250 with a 10:1 taper.
Before we get into the weeds, let's get a discussion going and settle on the driver that will give us the best shot of a small enclosure that will hit f3 of 40 hz. After that, we will tackle the enclosure, the length, the material, the folded tunnel, etc.
Let's have a go at it.
scott
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OK, good to know so that is not the driver we will be using in this thread - Does anyone have an idea about a full range driver that will work at the level we want remembering that this is a near field project?
As mentioned before, the 3" tangband woofer w3-2108 (45 fs), using the formula that Planet10 mentioned 45 *root(2)/2 would give us about 31. But we want to use a full range 3 or 3.5" so there should be one out there that has a Fs around 55 to 60.
scott
As mentioned before, the 3" tangband woofer w3-2108 (45 fs), using the formula that Planet10 mentioned 45 *root(2)/2 would give us about 31. But we want to use a full range 3 or 3.5" so there should be one out there that has a Fs around 55 to 60.
scott
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What's this for?
Anyway, according to Richard Small [the 'S' of T/S], ~40 Hz/f3 minimum is ~0.3 ft^3 net, but only at 0.2% eff. [fig. 16], so will be a quiet little bugger @ ~85 dB/W/m peak: http://www.readresearch.co.uk/thiele-small_papers/smalls_vented_box_article_1.pdf
GM
If you want a compact 40Hz capable speaker, a TL is not the way to do it, by necessity, you will need a very long line to get a 1/4-wave 40Hz fundamental - and that just takes a lot of volume.
I would instead suggest looking at something like a 6th order bandpass alignment which can be made very compact given a driver with a small Vas, low fs, and moderately low Qts.
For example, take the XKi - with 3.5in RS100-8, it could reach 50Hz. Any tiny driver asked to go that low will have distortion when played loud. However, take the same alignment and design it for a nice larger full range like a W5-2143 and you get something that sounds pretty good and can dig maybe to 50Hz. Now to go to 40Hz, you need a driver with an fs in the range of 35Hz - and generally, those only come in around 8in, maybe 6.5in sometimes.
I made an XKi with an Eminence Beta 8cx coaxial once and it hit 50Hz cleanly. Nice sensitivity and power handling to go well with a compression driver. The Vas is only 0.5 cu ft so the box was pretty compact.
I would instead suggest looking at something like a 6th order bandpass alignment which can be made very compact given a driver with a small Vas, low fs, and moderately low Qts.
For example, take the XKi - with 3.5in RS100-8, it could reach 50Hz. Any tiny driver asked to go that low will have distortion when played loud. However, take the same alignment and design it for a nice larger full range like a W5-2143 and you get something that sounds pretty good and can dig maybe to 50Hz. Now to go to 40Hz, you need a driver with an fs in the range of 35Hz - and generally, those only come in around 8in, maybe 6.5in sometimes.
I made an XKi with an Eminence Beta 8cx coaxial once and it hit 50Hz cleanly. Nice sensitivity and power handling to go well with a compression driver. The Vas is only 0.5 cu ft so the box was pretty compact.
Hey Gm,
"What's this for?" Well, who knows - just a little exercise to see if we can design the smallest tapered T-line that will hit F3 40hz or below using new materials, innovative thinking about the enclosure, on board electronics and a driver under $25.
Let's decide on a driver - I have made a Parts Express table as a graphic below. I used Planet 10's formula (see the top green column) to see which 2,3 or 4" driver would have a chance to get to 40 hz in a T-line. The ones in green I think are the best candidate's with yellow = maybe. I think, but I need some experts to chime in, that the best one is the one in bright green in the 2nd column. Once we all agree on one of these under $25 drivers, then all who are part of this thread can buy one, then keep on reading this thread to get all the expert's ideas. Then we can all make the same enclosure or different ones and then we can compare the builds. Hopefully, we together, will come up with a really nice sounding, compact (under 1000 cu in / 16 liters) system with an amp and BSC/EQ circuitry. Xrk971 suggested I make the project more focused and hopefully I did it.
scott
"What's this for?" Well, who knows - just a little exercise to see if we can design the smallest tapered T-line that will hit F3 40hz or below using new materials, innovative thinking about the enclosure, on board electronics and a driver under $25.
Let's decide on a driver - I have made a Parts Express table as a graphic below. I used Planet 10's formula (see the top green column) to see which 2,3 or 4" driver would have a chance to get to 40 hz in a T-line. The ones in green I think are the best candidate's with yellow = maybe. I think, but I need some experts to chime in, that the best one is the one in bright green in the 2nd column. Once we all agree on one of these under $25 drivers, then all who are part of this thread can buy one, then keep on reading this thread to get all the expert's ideas. Then we can all make the same enclosure or different ones and then we can compare the builds. Hopefully, we together, will come up with a really nice sounding, compact (under 1000 cu in / 16 liters) system with an amp and BSC/EQ circuitry. Xrk971 suggested I make the project more focused and hopefully I did it.
scott
Attachments
Just saw your note - thanks for joining. And thanks for the suggestions.
Yeah, I know the bandpass is the best but then it is not full range with one speaker - I have a bandpass, two theater systems, two 15" subs, a sunfire sub, a floating dual person theater chair with two Tv's and two planar audio systems and about 50 speakers laying around. So what am I doing (sometimes I ask that too.)
The reason I wanted to start this thread is to get a bunch of experts together (and I'm not one of them) and challenge all of us to rethink how we can reduce the size of a T-Line. I think it can be done and the calculations that I have done show that we can do it with a 45 to 55" line depending on the taper with a 3" driver (remember the goal is near field.) And I think we can get that line in a box or pipe using a Helicord, or a spiral Archimedes screw or thin stiff labyrinth strips. Then with an on board BSC/Eq circuit before an on board amp, we can make our goal. I'm assuming that a T-Line has the cleanest, lowest, and tightest bass (not in each category but all together) so let's go and find it.
My wife buys clothes and I buy speaker parts - she stays downstairs and I stay upstairs in my lab with my new 3D printer and that probably is why we have been together for 50 years. So if anyone is asking why this thread - now you know.
Yeah, I know the bandpass is the best but then it is not full range with one speaker - I have a bandpass, two theater systems, two 15" subs, a sunfire sub, a floating dual person theater chair with two Tv's and two planar audio systems and about 50 speakers laying around. So what am I doing (sometimes I ask that too.)
The reason I wanted to start this thread is to get a bunch of experts together (and I'm not one of them) and challenge all of us to rethink how we can reduce the size of a T-Line. I think it can be done and the calculations that I have done show that we can do it with a 45 to 55" line depending on the taper with a 3" driver (remember the goal is near field.) And I think we can get that line in a box or pipe using a Helicord, or a spiral Archimedes screw or thin stiff labyrinth strips. Then with an on board BSC/Eq circuit before an on board amp, we can make our goal. I'm assuming that a T-Line has the cleanest, lowest, and tightest bass (not in each category but all together) so let's go and find it.
My wife buys clothes and I buy speaker parts - she stays downstairs and I stay upstairs in my lab with my new 3D printer and that probably is why we have been together for 50 years. So if anyone is asking why this thread - now you know.
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