Quarter Wave / T-Line tutorial-UPDATED

[robnie]

hello i am ronnie and for al know is the best qts for a transmisionline between 0,5 and 0,7 thats what i have raed somewere but i am not sure.

in the past i have used a t-line in a car it was verry acurat en i thougt loud to it was a t-line for a RE audio subwoofer the SE series 2x2 ohms its only a 600 watt sub i had a rockford bd1501 on it driven on a 1 ohm load giving it about 2000watts rms ps only play that amp on a 1 ohm load when you have enough power from your bateries otherwise it will go wrong.

but back on the story that sub dit 142,3 db on daily music and sounded great in every way.

it was tuned below 30hz for sure for the people who have a sub like that i try to put a drawing of the enclosure on this forum please note i did not calculate the enclosure i only build it that time the wood i used was 3cm whats that about 1,2 inch thick sorry for that i am from the netherlands now jou will all why my englisch writing is zo bad

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the only problem for you guys its al in cm its tappered 0,5 thats what they told me that time it sounded great thats all thats matter

[jeremyg]

8 inch driver..23 hz....

I have never built anything quite like it, many tlines, but not one like that....thoughts?

edesignaudio e3.8 woofer

Qts: .30

Qes: .38

Qms: 3.5

Fs: 23.00Hz

[robnie]

i see that the most time u all use straight lines i am not used to do that.

for all i know they would play the best on tunings frequentie and when they are tappered they should play better.

but thats what i hear i am not a calculater i just build them i did try it sometimes i used a eusy calculation

speed of sound 340 meters per second i shared that bij the Fs of the sub and what came out i shared that by 4.

what came out i used fore the length of the line.

i started the line at 1.5 times SD and the end of the line i used 1 time SD it was an enclosure for 4 subwoofers 4 eights from rockford fosgate i did put them al in one enclosure.

they didnt go verry low butdid hit 141db on dayly music

[Hollowstylez]

I like that box robnie. So both levels are zig zaged like that? The port must be more then 10ftI long.

[robnie]

it is not a split level enclosure.

what you see is it only one tappered T-line length about 2 meters its a small enclosure.

outside dimensions are.

length 37,4 inch hight 17.7 inch depth is 13.78 inch.

its calculated for one single resonant engineering SE 12 inch dual 2 ohm subwoofer.

every singel piece of wood i used with the build was about 1.2 inch thick.

thats alsow the wood thiknes were the drawning is based on.

and i braced it on the inside to keep the fibrations as low as posible.

[Hollowstylez]

oh, my bad. I see what your doing, cool design bro.

[stroupe79]

Is there a way to Tline 4 10s?

[Hollowstylez]

I don't see why you couldn't. It would be a pretty big box but maybe a tapped horn could help you reduce some of the vent length and in turn save some space?

[robnie]

no it was not realy big i just put 4 in one enclosure that was calculated for only one subwoofer.

for me it was just put them in and play and that was a good thing that time.

so a litle drawning to see how i did it that time.

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[robnie]

this is the story where i learned te most from maybe it helps for you guys

Transmissionline , difficult, or falls.

Dear reader, the following article is intended to give some clarity about building TL cabinets. The Quarter-wafe TL than understood.

There is still all about different systems of thought, TL-'t is but nothing – until – praised to the skies. And Yes, it is but what your preference is in view and what you can place in your listening room.

As with any speaker system is the necessary philosophy and theory at advance. Interesting of course, but you should first study all you can go now for build? Well, that remains all along. I've deliberately omitted to simplify the story, who settled there in anyway and would deepen, may be enough to find on internet. For example, on the site of M.J.King

The data in this article will be sufficient to design your own TL , because more you have not needed.

This article is so purely to build and not to reinvent Transmissionline .

Transmissionline , the theory,

The functioning

A TL is an open system, equipped with a baskamer with a tapered channel, the corresponding line in a port, Samut prakan . In order to keep the size of the closet is usually acceptable line several times folded and thus a labyrinth. When the line is in resonance, and this is at 1/4 of the wavelength of the fundamental frequency of the open end, then there will a reflection back. This reflection reaches the back of the Cone in which unwanted cone movements against phase, at resonance be reduced. The even harmonics, that occur at each quarter wavelength of the fundamental frequency (every even multiple of the fundamental frequency) are suppressed by the labyrinth. It is therefore particularly interested in the odd harmonics.

The third harmonic reflection reaches the end of the line in phase and thus gives no problem. From there comes The fifth harmonic phase and should be muted. By this fifth there are 3 points in the line, which should be a weakening of muted ca 3 dB. (length divided by five gives three points between end and start)

The end korrektie.

Because the air particles leave the port with a great speed, persevere this a short time in this movement and therefore "see" a longer line than there really is. This is caused by the wervelings effect. This can be applied leaving the eindkorrektie line may be slightly shorter. But it need not necessarily.

The influence of damping material on the sound speed.

When damping material is applied in the line , there will be heat exchange by the passing air particles a place. This is called the isothermisch effect. This causes the closet is bigger and also the velocity of sound volume seemingly lower. If applied too little damping, the maximum effect is not achieved, isothermic with too much damping a mechanical obstacle arises while. The normal sound speed is 340 m/sec and is under ideal circumstances reduced to isothermal 290 m/sec. for calculations is therefore held an average of 300 m/sec.

Attenuation versus the Q-factor of the total system.

The Q-factor i.e. the q(l) is a vergrotingsfaktor where along the resonance is magnified. If too much attenuation is applied, is the Q-factor of the whole system layer and the sound thick and death. With too little damping is the Q-factor is too large and this creates a hump in the view characteristic. A sound so boemerig .

The effect that may arise in the living room as a result of rebounding sound to the speaker is negligible. There can by this effect an E.M.F. (electro-motor power) in the speaker units occur, which increases the Q-faktor . Just forget because there under normal circumstances you'll listen None of brands.

The influence of the Nuraghe of the line.

If the surface of the cross-section of the line would be equal over the entire length, one particular frequency stressed, as in an organ pipe. Therefore this intersection towards the end to be progressively reduced, in order to reduce possible and disseminate resonantie's about a wide frequency range. However, if the reduction in diameter too large is taken, this will affect the quality of the bass, which view itself through "locked up and omfloerst" sound. For clarity, then the starting opening so too small.

Summary of the operation of the TL.

1-strengthening the output below the resonance frequency of the speaker and the mitigation of unwanted conus results.

2-The mute and mastering the cone movements at resonance.

3-strengthen and obtaining a straight view of 30 to ca 120 Hz. depending on the resonance frequency of the basspeaker

4-the weakening of the fifth harmonic with ca 3 dB

5-weakening of the view above 150 Hz.

6-delivering the requisite Q-faktor.

Practice.

The length of the labyrinth is determined by dividing the speed of sound by the resonance frequency and that divided by four. So with the following formula:

L = 1/4 x C/ fs (length without end correction.)

C is the average velocity of sound in the line and 300 m/sec and therefore the resonance frequency of the fs basunit.

Or:

You can also set the length of the line reducing with a shortening factor which depends on the surface area of the cross-section. This last may but need not necessarily. The relationship between the diameter and the length L A is given in the formula:

L = 1/4 x C/fs -1.7 x the square root of A/pi (length with end correction.)

Here is the resonance frequency of the fs basunit. pi is a mathematical concept but is the number 3.14. So here is A 1,5 times the radiant surface of one driver. That 1, 7 x the square root of A/pi, so is that shortening factor. (I usually disregard, especially if the output is not at the floor)

When is now the line in resonance. Well, that is if the length of the line 1/4 wavelength is of fundamental frequency of basunit, or: the Fs of that unit. How you count than that? Well, with the following formula where we just assume that the fs of the unit is 30 Hz.

With the formula for calculating the length of the line, you come then at 2,5 mtr. So,

1/4 x C/L, so, 1/4 x 300/2.5 then you come on 30 Hz.

To obtain the desired quality must be the intersection of the beginning of the line ca 50% larger than the shining surface of the basunit, while the line ends with a surface equal to that shining surface.(is the shining surface of the basunit)

The length of the line starts directly behind the woofer. With multiple basunits I'm assuming the middle of that woofer Setup.

And how you count from the surface of a circular something?

1/4 x pi x dia kwadraad.

So, as an example the diameter is 10 cm. Then it becomes surface:

1/4 x 3.14 x 10 x 10 = 78.5 cm * beginning of the line is then completed so therefore 1.5 x 78.5 cm * 117,75 = 118.

The practical practice of from my experiences.

How to start. Well, you can start looking for a kit of course, but if you own fantasy dares, with a closet, you need to create with this story out there.

You must then so looking for units and then if you've made a choice to use for the units, the cabinet size determined mainly by the woofer (s). Determine the width of the front so that the woofer fits nicely there. Then the contents of the Cabinet work you out to the back. Depending on the length of the line that will be folded one or more times.

Not forget to integrate the mid /hoog compartment. This sub-fund may optionally bass reflex or closed. Also hangs off a bit of the basmid unit. This can, of course, also a los icon.

The tuning for the layer view of the compartment is not critical because the TL does that already low though.

Now his most TL designs with one basunit designed, but multiple basunits in a TL may very well. This must be equal units.

If you want to use more than 1 basunit, then the beginning of the line to be in surface not larger. Why not?

Suppose you have 10 Watt and one unit. The cone would result than bv 1 cm. Put you now have another unit parallel or in series, then it will power on the two units will be the semi divided and this therefore still make rash. The air movement in the line therefore remains virtually the same as with one unit. It also has another advantage.

Is the effective cone woofers with multiple surface magnified, making it sound power afgestraalde relative increases one bass. Basunits multiple will suffer less so because they put together a less intermodilatievervorming need to make large Cone, to the rash than one same sound pressure to deliver.

Thinking to the following,

-If you have two woofers in series turn, they will equally play hard as the single woofer but you should keep in mind that the filter in your passive impedance is doubled. You can fit this far if you both your woofers if you want to work less hard, but amplifier not interested in larger sound pressure.

-If you have two woofers in parallel move, take the sound pressure increases by 6dB, but keep in mind that your amplifier to deliver the double power (= the dual stream).

-If you're four woofers in a combination of series and parallel turns, so the total impedance remains the same, you have increase in sound pressure, 6dB amplifier should work equally hard while you and every woofer but the need to create half a rash. That is of course a great profit but it will cost you to the necessary drivers.

.

Another advantage of two or more in a line, basunits, is that they work against each other's ongoing and standing waves, allowing the smoothing of the line easier. A thin layer damping material along the back wall of the line doing it than with me well. Be careful with the "filling" of parts in the line. That can have a negative impact. Locked up bass. Always first try to your ears say it is good.

For the woofers are units chosen with a 0.5 to 0.7 Qts . This kind of go a bit further in low units than those with a low Qts and we want to please. A unit with a lower will go through further Qts in the higher layer or low mid area.

Filtering is a matter of choice and to apply the units.

As you already may have read, is a TL only functional till ca. 150 Hz will go above it weaken the signal line . Most designs are now filtered the separator between low and mid frequency 500 Hz is located at. So, between 150 and 500 Hz, which should see the woofer but ready to play, what sometimes succeeds, but there still will have difficulty because of the negative influence of the line at those frequencies. Midtones in may against phase the exit of the reach the view line and so upset. This is called the TL hole. Nevertheless, a kind of blip in the view.

This phenomenon is sometimes resolved by an extra basunit to add in its own compartment. In that case, the "big" bass runs and the second by afgefilterd layer to the acquisition frequency of the midunit.

Information about filters can be found in the article on filters, also here on the homepage.

Well, I find it remarkable that I've not bothered with a two and a TL hole halfway filter. It gives a smooth gradient from low to mid with a simple way of filtering.

I filter than the bass off at 100 Hz, because higher has no purpose and also gives more adverse effects. Then I leave a basmid, preferably a broadband-based type, then af abandon that is filtering the acquisition frequency of the tweeter that you want to apply. And that frequency is not depending on your taste, as I so often read, but your own interpretation of that, what happens when you as a realistic reflection. A crossover between mid and high on ca meets me very good and everything 6 dB 4000Hz. But you can opt for higher order filters and other separation frequencies if you think that is better.

Than just two images of how a line can be folded. The red line indicates how the length of the measuring line in practice.

A is the midin these cases/hoog compartment. ( the beginning with there rear C and D which are getting smaller in diameter.

Finally,

I hope I have some clarity with this article created about building TL cabinets. If all is well, you need with this article in hand, only fantasy for appearance, and your ears (measure may also) for the adjustment of the units, a TL can build. Harder is not.

After this, you'll have to read and studied best still can have many questions. Well, we also have a forum where you can turn to with questions.

FLUORESCENT cabinets are often not really small and if you listening room is also the living room, then possibly a bit on there, the little flower colour scheme to suit the rest of the Interior and then everyone happy.

Good luck with build.