Hi all!
This is my first post here.
I´m thinking of building a pair of folded TL subs with dual Vifa XT18W009 (www.d-s-t.com/vifa/index.htm) units. If I want to use 2 woofers i a TL, do I simply take the woofer´s conearea x2 when determining the area of the TL?
The advantage of using 2 woofer TL is that it´s possible to use a bit lower tuningfreq. than the 1 woofer TL. Have I got it right?
Any other advantages in using dual woofers?
Any disadvantages?
regards/Per
This is my first post here.
I´m thinking of building a pair of folded TL subs with dual Vifa XT18W009 (www.d-s-t.com/vifa/index.htm) units. If I want to use 2 woofers i a TL, do I simply take the woofer´s conearea x2 when determining the area of the TL?
The advantage of using 2 woofer TL is that it´s possible to use a bit lower tuningfreq. than the 1 woofer TL. Have I got it right?
Any other advantages in using dual woofers?
Any disadvantages?
regards/Per
By clever placement you can dampen some higher resonant frequencies that are responsible for the irregular FR in the upper-bass/lower-midrange of some TLs.
I'm not sure anymore whether it was at one fith and one third of the linelength. If there is noone else on the forum (Dave ?) who can supply details i could dig the info out but this might take some time.
Regards
Charles
I'm not sure anymore whether it was at one fith and one third of the linelength. If there is noone else on the forum (Dave ?) who can supply details i could dig the info out but this might take some time.
Regards
Charles
Hi Charles.
Interesting. It would be great if you could find the info. I'm in no hurry, though - Haven´t bought the drivers yet.
I found this at http://www.seas.no/thor.htm
/Per
Interesting. It would be great if you could find the info. I'm in no hurry, though - Haven´t bought the drivers yet.
I found this at http://www.seas.no/thor.htm
/Per
Look here:http://www.quarter-wave.com/General/General_Articles.html
the rest of this site is very interesting also. You should look on the website of planet10 as well. He is the TL guru here.http://www.t-linespeakers.org/index.html
the rest of this site is very interesting also. You should look on the website of planet10 as well. He is the TL guru here.http://www.t-linespeakers.org/index.html
take a look at this site : www.theloudspeakerkit.com
They have a project (actually a kit) named TL6 that uses 2 P17WJ from Vifa in a TL.
Since I have 4 of these woofers I wanted to build one, but I have no drawing sheets, so I should make a sort of reverse-engineering from the photos in the mounting instructions.
Since they sell a kit I don't think they will be willing to give anyone drawings for the enclosure (unless you purchase the kit without cabinet of course)... that's a pity.
Reverse-engineering can give approximated measures, but to be true I don't know how much TL systems are sensitive to slight changes in the cabinet.
Does anybody know?
Cheers
Andrea
They have a project (actually a kit) named TL6 that uses 2 P17WJ from Vifa in a TL.
Since I have 4 of these woofers I wanted to build one, but I have no drawing sheets, so I should make a sort of reverse-engineering from the photos in the mounting instructions.
Since they sell a kit I don't think they will be willing to give anyone drawings for the enclosure (unless you purchase the kit without cabinet of course)... that's a pity.
Reverse-engineering can give approximated measures, but to be true I don't know how much TL systems are sensitive to slight changes in the cabinet.
Does anybody know?
Cheers
Andrea
TL Bose Acoustimas modules
I have seen some of the newer Bose acoustimass modules that use long-excursion 5.25" woofers (I actually looked at them while they were running and they were VERY high excursion woofers) and they look like they use transmission lines. How does Bose get away with using transmission lines that are much smaller than the woofer's surface area?
(The results aren't bad, either. They're still Acoustimass modules and they're still Bose, but they are a major step up from the older 8th-order Bandpass modules in the area of impact and deeper response that seems like it goes down to about 40 Hz. Much better than the old modules' measured 62 Hz.)
I have seen some of the newer Bose acoustimass modules that use long-excursion 5.25" woofers (I actually looked at them while they were running and they were VERY high excursion woofers) and they look like they use transmission lines. How does Bose get away with using transmission lines that are much smaller than the woofer's surface area?
(The results aren't bad, either. They're still Acoustimass modules and they're still Bose, but they are a major step up from the older 8th-order Bandpass modules in the area of impact and deeper response that seems like it goes down to about 40 Hz. Much better than the old modules' measured 62 Hz.)
I found the article again. It was in the German magazine Klang & Ton issue #2 2002.
The drivers are in fact placed at one third and at one fith of the linelength.
Because they can be quite far apart from each other, the principle is best suited for three-way systems.
I am not sure wheter it would work fine with a 2.5 way as well.
Even if you don't place them in the aforementioned positions, two woofers can offer the possibility to drive the line more evenly than one driver. I.e. the resonance will be weaker but wider.
One company selling multi-woofer TLs is the German manufacturer Newtronics: www.newtronics.de
Something special about this company is the fact that they offer kits as well. One is presented in the current issue of Klang & Ton. It uses two slightly different 18 cm Vifa woofers, one of which has a "wooden" cone.
Regards
Charles
The drivers are in fact placed at one third and at one fith of the linelength.
Because they can be quite far apart from each other, the principle is best suited for three-way systems.
I am not sure wheter it would work fine with a 2.5 way as well.
Even if you don't place them in the aforementioned positions, two woofers can offer the possibility to drive the line more evenly than one driver. I.e. the resonance will be weaker but wider.
One company selling multi-woofer TLs is the German manufacturer Newtronics: www.newtronics.de
Something special about this company is the fact that they offer kits as well. One is presented in the current issue of Klang & Ton. It uses two slightly different 18 cm Vifa woofers, one of which has a "wooden" cone.
Regards
Charles
I am trying to design a variation of the 2 woofer TL.
my idea is a 4 in line full range driver system using 4 3" 871S drviers available at CSS. CSS sells them in boxes of 20. 20 / 5 (the 5 came from 5.1) and you get 4 drivers per channel.
can any help?
the 4 drivers will be in line (sort of short line source) and will be wired as a 1.5 way (2 drivers full range and 2 drivers providing bass reinforcement / baffle step compensation only.
many moons ago I had read an article in Speaker Builder (1985/86/87) where someone has built a 4 in line TL using 2 coax drivers and 2 drivers that had their coax tweeters missing (WFFW). i dont know if anyof you have access to this article maybe it wil provide a few clues on how I can build my system.
my idea is a 4 in line full range driver system using 4 3" 871S drviers available at CSS. CSS sells them in boxes of 20. 20 / 5 (the 5 came from 5.1) and you get 4 drivers per channel.
can any help?
the 4 drivers will be in line (sort of short line source) and will be wired as a 1.5 way (2 drivers full range and 2 drivers providing bass reinforcement / baffle step compensation only.
many moons ago I had read an article in Speaker Builder (1985/86/87) where someone has built a 4 in line TL using 2 coax drivers and 2 drivers that had their coax tweeters missing (WFFW). i dont know if anyof you have access to this article maybe it wil provide a few clues on how I can build my system.
Two bass drivers in a TL can be made to work fine -- of course i suggesy push-push loading them
I am currently working on a design using Vifa P17s OEM units for PSB. (i have a box of 20 and need to make some space). After considering many options i have decided on a push-push MTM in an exolinear alphaTL*. I haven't decided what tweeter to use -- i have an aluminum dome Vifa, a Stryke magnetostat ribbon, and some DynaAudio D21(?).
* i'll be able to say more on the alphaTL after Rick's article appears in audioXpress. What it is a simple algorithm for determining optimum TL size for a tightly defined TL configuration.
Keep in mind that the old rule-of-thumb about basing the TLs x-section on the driver cone area has proven to be complete myth. X-section is mostly based on the Vas of the driver (and an entire design can be run off this, Qt, and Fs, plus some design decisions).
I would highly recommend getting into Martin's TL articles at his quarterwave.com site and a visit to my site will give you some design ideas & some historical background.
As Rick Shultz (exolinear) churns out more of his cookie cutter design algorithms (he is already working on the next one), doing a TL will become as easy as making a sealed box.
dave
I am currently working on a design using Vifa P17s OEM units for PSB. (i have a box of 20 and need to make some space). After considering many options i have decided on a push-push MTM in an exolinear alphaTL*. I haven't decided what tweeter to use -- i have an aluminum dome Vifa, a Stryke magnetostat ribbon, and some DynaAudio D21(?).
* i'll be able to say more on the alphaTL after Rick's article appears in audioXpress. What it is a simple algorithm for determining optimum TL size for a tightly defined TL configuration.
Keep in mind that the old rule-of-thumb about basing the TLs x-section on the driver cone area has proven to be complete myth. X-section is mostly based on the Vas of the driver (and an entire design can be run off this, Qt, and Fs, plus some design decisions).
I would highly recommend getting into Martin's TL articles at his quarterwave.com site and a visit to my site will give you some design ideas & some historical background.
As Rick Shultz (exolinear) churns out more of his cookie cutter design algorithms (he is already working on the next one), doing a TL will become as easy as making a sealed box.
dave
Thanx for the input guys! I't always nice to deal with people who knows what whey're talking about . I guess I have to start from scratch then. Well I'll rather do that than building a lousy sounding speaker.
Charles-> I have a pair of Vifa Woodfiber cone units in my possesion already, (XT18WH09) Which is designed for good midrange also. The XT18W009 has a little stronger magnet and focuses in on the lower regions.
Well, got some reading to do!
regards
Per
. I guess I have to start from scratch then. Well I'll rather do that than building a lousy sounding speaker.Charles-> I have a pair of Vifa Woodfiber cone units in my possesion already, (XT18WH09) Which is designed for good midrange also. The XT18W009 has a little stronger magnet and focuses in on the lower regions
. Well, got some reading to do!
regards
Per
Phear said:
Charles-> I have a pair of Vifa Woodfiber cone units in my possesion already, (XT18WH09) Which is designed for good midrange also. The XT18W009 has a little stronger magnet and focuses in on the lower regions
Be sure and let us know how you like those drivers, I haven't seen any comments from anyone since they're so new.
Rob
planet10 said:Two bass drivers in a TL can be made to work fine -- of course i suggesy push-push loading them
I am currently working on a design using Vifa P17s OEM units for PSB. (i have a box of 20 and need to make some space). After considering many options i have decided on a push-push MTM in an exolinear alphaTL*. I haven't decided what tweeter to use -- i have an aluminum dome Vifa, a Stryke magnetostat ribbon, and some DynaAudio D21(?).
...
As Rick Shultz (exolinear) churns out more of his cookie cutter design algorithms (he is already working on the next one), doing a TL will become as easy as making a sealed box.
dave
Wow, just what I was looking for!
At which stage the design is?
About tweeter choice I am in similar doubt: a alu dome Seas vs a Visaton ribbon (but I'm afraid it has to be crossed too high); oh, if I could can get my hands on a heil tweeter.....
Anyway if crossover freq is not too high I'd go for the ribbon.
Jus my 2 cents...
Cheers
Andrea
Re: Re: Dual Woofer TL?
Dave, by "push-pull" do you mean having both units firing outwards but with one of them mounted backwards (and with its phase reversed) to reduce harmonic distortion?
Or,
do you mean that the two units are firing outwards and mounted opposite to one another so that the mechanical vibrations are cancelled (to an extent)?
Or, both of the above?
I would guess that you mean the latter with your "cancels most of the Newtonian effects" but could you clarify "improving dynamics and reducing box load"?
Also, to what extent would you tune the line to a lower frequency when using 2 drivers (as Phear suggests you could)? When I designed my System IV , I prototyped lines using 1 and 4 drive units. I did make the line longer for 4 units as the driver excursion at the low frequency would be less with more drivers. Is there another reason?
Fascinating point about X-section being a function of driver Vas. I didn't know that. Just off to Martin's site to investigate further.
Steve
planet10 said:
Dave, by "push-pull" do you mean having both units firing outwards but with one of them mounted backwards (and with its phase reversed) to reduce harmonic distortion?
Or,
do you mean that the two units are firing outwards and mounted opposite to one another so that the mechanical vibrations are cancelled (to an extent)?
Or, both of the above?
I would guess that you mean the latter with your "cancels most of the Newtonian effects" but could you clarify "improving dynamics and reducing box load"?
Also, to what extent would you tune the line to a lower frequency when using 2 drivers (as Phear suggests you could)? When I designed my System IV , I prototyped lines using 1 and 4 drive units. I did make the line longer for 4 units as the driver excursion at the low frequency would be less with more drivers. Is there another reason?
Fascinating point about X-section being a function of driver Vas. I didn't know that. Just off to Martin's site to investigate further.
Steve
Re: Re: Re: Dual Woofer TL?
I actually say push-push, but you have correctly described push-pull. As your drivers get better this tchnique has less & less effect (ie Nick at Lambda says that his drivers are linear enuff that this has no benefit)
Yes, that is what i mean
Whenever a single driver moves in & out it moves the box -- usually by only a small amount mind you, but i am sure you have heard stories people tell of there subwoofers "walking" -- and vibrational energy is transfered into the box. If the 2 push-push drivers are tightly coupled the 1st is effectively eliminated, and the 2nd is dramatically reduced.
In the strictest sense you do not tune the box lower, you just treat it as a driver with twice the Vas. But it is coming to light that you can actually get more bass by tuning the line a little higher than the Fs of the driver.
dave
7V said:
I actually say push-push, but you have correctly described push-pull. As your drivers get better this tchnique has less & less effect (ie Nick at Lambda says that his drivers are linear enuff that this has no benefit)
Yes, that is what i mean
Whenever a single driver moves in & out it moves the box -- usually by only a small amount mind you, but i am sure you have heard stories people tell of there subwoofers "walking" -- and vibrational energy is transfered into the box. If the 2 push-push drivers are tightly coupled the 1st is effectively eliminated, and the 2nd is dramatically reduced.
In the strictest sense you do not tune the box lower, you just treat it as a driver with twice the Vas. But it is coming to light that you can actually get more bass by tuning the line a little higher than the Fs of the driver.
dave
Re: Re: Re: Re: Dual Woofer TL?
Whoops, I misread that. Push-push, huh? So that's what it's called.
Interesting point Nick at Lambda makes. Is the improvement that is claimed for push-pull over push-push a function of linearity though?
What do mean when you say "more bass"?
----------------------------------------------------------
Incidentally, while I'm here, has anyone done any modelling of Daline behaviour (box with a line)? I'd be interested to see how well the theory ties in with the practice.
Steve
planet10 said:
Whoops, I misread that. Push-push, huh? So that's what it's called.
Interesting point Nick at Lambda makes. Is the improvement that is claimed for push-pull over push-push a function of linearity though?
What do mean when you say "more bass"?
----------------------------------------------------------
Incidentally, while I'm here, has anyone done any modelling of Daline behaviour (box with a line)? I'd be interested to see how well the theory ties in with the practice.
Steve
Re: Re: Re: Re: Re: Dual Woofer TL?
June 03 audioXpress ... Rick Shultz's alphaTL article. His modeling of this has shown gains in bass by shortening the line slightly from that determined by Fs/4 and increasing the cross-section. I know i am getting very good bottom from my 1st alphaTLs (with 2x6.5"/box)
This was one of Auspurger's example lines. Calculate the TL volume, assign a 1/3 to the pre-chamber, and the rest to a straight line of the appropriate length. The pre-chamber acts as a low-pass filter for the terminus.
dave
7V said:
June 03 audioXpress ... Rick Shultz's alphaTL article. His modeling of this has shown gains in bass by shortening the line slightly from that determined by Fs/4 and increasing the cross-section. I know i am getting very good bottom from my 1st alphaTLs (with 2x6.5"/box)
This was one of Auspurger's example lines. Calculate the TL volume, assign a 1/3 to the pre-chamber, and the rest to a straight line of the appropriate length. The pre-chamber acts as a low-pass filter for the terminus.
dave
Re: Re: Re: Re: Re: Re: Dual Woofer TL?
I arrived at approximately these dimensions by experimentation - I built a variable prototype where I could experiment with box size (pre-chamber) as well as line size. However, I don't believe that it's sufficient to just say that the pre-chamber acts as a low-pass filter for the terminus - more that the line acted as a "bass purifier" for the chamber. With my experimental prototype I could also open and close the line by sliding a piece of wood (port). When closed it formed an air-tight joint.
I found that the way for me to get the best sound with this particular design was to establish the optimum closed box size (close the port) and then add the line. The sound was very similar throughout the range with the line turned on or off, except that the bass was much more convincing when the line was open. Further experimentation and listening showed that without the line (and with tiny 2" units in a relatively large box) there was a very noticeable second harmonic distortion at the bottom end. This disappeared when I opened the port. The bass sounded deeper and more convincing with the line added.
At the time I patented the "stand-line" (here it is) that I developed as I realized that you could take any closed-box speaker, drill a hole in the bottom, and put it onto a transmission line stand. I still think that this is a good idea.
Does anyone have a closed-box speaker that they want to try this with?
Steve
planet10 said:
I arrived at approximately these dimensions by experimentation - I built a variable prototype where I could experiment with box size (pre-chamber) as well as line size. However, I don't believe that it's sufficient to just say that the pre-chamber acts as a low-pass filter for the terminus - more that the line acted as a "bass purifier" for the chamber. With my experimental prototype I could also open and close the line by sliding a piece of wood (port). When closed it formed an air-tight joint.
I found that the way for me to get the best sound with this particular design was to establish the optimum closed box size (close the port) and then add the line. The sound was very similar throughout the range with the line turned on or off, except that the bass was much more convincing when the line was open. Further experimentation and listening showed that without the line (and with tiny 2" units in a relatively large box) there was a very noticeable second harmonic distortion at the bottom end. This disappeared when I opened the port. The bass sounded deeper and more convincing with the line added.
At the time I patented the "stand-line" (here it is) that I developed as I realized that you could take any closed-box speaker, drill a hole in the bottom, and put it onto a transmission line stand. I still think that this is a good idea.
Does anyone have a closed-box speaker that they want to try this with?
Steve
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