[ITEM]
19.02.2019

Quarter Wave Box Calculator

63

Photo 1: The TABAQ speaker A transmission line designed and optimized for the Tang Band 3” full- range drivers. Adapter Inspired by debates on the Internet about quarter wave designs with Tang Band 3˝ full-range drivers, I decided to design my own quarter wave loudspeakers. They sure deserve a better construction than those found on the Internet. In the last couple of years, I have worked with the useful simulation models from Martin J.

King and designed and built a successful TL sub (“The HideAway TL Sub,” 7/06 aX). Working with Martin’s models is quite educational, and I feel confident about quarter wave (transmission line) design. Please refer to my article “Martin J. King for Dummies” on. The TABAQ Sound Pressure Level (SPL) is impressive for such a small driver, with a very smooth and broad frequency response.

The dashed line in Fig. 1 is the Infinite Baffle (IB) response, and the solid line is the summed output from the driver and the opening. The sound is open with no unwanted resonances, and the bass is relatively deep and clean. The first time you listen to this speaker, you will be impressed by the quality of the sound and performance of the bass, bearing in mind the size of the driver and the lack of financial problems building it. The problems with baffle step are corrected with a simple filter, which balances the SPL in the listening room. Figure 1: TABAQ sound pressure level.

Under the “Enclosure Specifications” section, you will notice the fields labeled, “1/4 Wave Tuning Point,” “Port Frequency 1,” “Port Frequency 2,” and “Box Frequency.” In order to achieve the intended alignment model of the formulas in the calculator, you must try and get these numbers as close to the same as each other. This calculator is designed to give the vertical length (height) of a quarter wave ground plane antenna, and the length of each of the four radials.

Tang Band Drivers You can use all the 3˝ drivers in this construction. My first test was with W3-926S, which I replaced with W3-315SC. The Tang Band drivers have a relatively high Fs and very high Qts, which means the rolloff is more gentle than a low Qts driver, and it is therefore possible to design a quarter wave with useful output well below Fs. However, high Qts drivers can be difficult to control. The whole idea with a quarter wave — or transmission line — is to extend the bass by the contribution from the opening. At the cabinet resonance, the output adds to the driver output. However, there are some unwanted higher harmonics, which are out of phase with the driver, causing uneven frequency response.

These problems can be solved by different design parameters, which I have successfully used with the TABAQ design. Figure 2: TABAQ design. Design The tuning frequency of the cabinet alone should be set lower than the driver Fs. Because the drivers all have a very high Qts, I started to see how low I could go, getting maximum bass performance out of the drivers without losing the overall frequency balance. After hours of simulation with Martin’s MathCad models, I found the best compromise was 55Hz, which is low for drivers with an Fs of 100 or 110Hz.

But it works! The tuning frequency is set by the length of the pipe and the geometry. A tapered pipe is shorter than a straight pipe for the same tuning frequency. TABAQ uses the mass loading principle, in which the last part of the pipe has a smaller area than the rest of the pipe. The air in this part of the pipe adds resistance to the driver (more mass-mass loading). Compared to a straight pipe, the length is shorter. The problems with unwanted higher harmonics are solved by driver placement, stuffing, and applied the geometry as in the mass loading. Rapidweaver The driver is one-third down the pipe, a common and well-known trick to attenuate the upper harmonics.

However, this is not enough, and damping of the cabinet is needed (as it is in every quarter wave). The damping is high (1 lb per cubic foot) and is placed in the upper part of the pipe. The last third of the pipe is not stuffed.

The stuffing will attenuate the output from the opening, so I solved this by increasing the volume of the cabinet. Increasing the volume also increases the output from the opening, so this compensates for the high density stuffing. The area of the pipe is four times the area of the driver (Sd). The TABAQ design is shown in Fig. Don’t be confused. This is not a bass reflex enclosure; it is a quarterwave.

Quarter wave box calculator

Figure 4: TABAQ compared to other designs. Cyburg’s Needle (top), Long Tall (middle), TABAQ (bottom). Listening Room Until now, I have focused on design theory. Real life is different, and I must deal with the baffle step problem, which generally applies to all full-range designs. You already know that a speaker placed in the middle of the room has a weaker bass than one placed against the wall. The same thing happens for the middle and high tones, which get extra help from the front of the cabinet. The result is a speaker that sounds bright with a focused middle tone. This “analytical” sound will be irritating after some time.

[/ITEM]
[/MAIN]
19.02.2019

Quarter Wave Box Calculator

95

Photo 1: The TABAQ speaker A transmission line designed and optimized for the Tang Band 3” full- range drivers. Adapter Inspired by debates on the Internet about quarter wave designs with Tang Band 3˝ full-range drivers, I decided to design my own quarter wave loudspeakers. They sure deserve a better construction than those found on the Internet. In the last couple of years, I have worked with the useful simulation models from Martin J.

King and designed and built a successful TL sub (“The HideAway TL Sub,” 7/06 aX). Working with Martin’s models is quite educational, and I feel confident about quarter wave (transmission line) design. Please refer to my article “Martin J. King for Dummies” on. The TABAQ Sound Pressure Level (SPL) is impressive for such a small driver, with a very smooth and broad frequency response.

The dashed line in Fig. 1 is the Infinite Baffle (IB) response, and the solid line is the summed output from the driver and the opening. The sound is open with no unwanted resonances, and the bass is relatively deep and clean. The first time you listen to this speaker, you will be impressed by the quality of the sound and performance of the bass, bearing in mind the size of the driver and the lack of financial problems building it. The problems with baffle step are corrected with a simple filter, which balances the SPL in the listening room. Figure 1: TABAQ sound pressure level.

Under the “Enclosure Specifications” section, you will notice the fields labeled, “1/4 Wave Tuning Point,” “Port Frequency 1,” “Port Frequency 2,” and “Box Frequency.” In order to achieve the intended alignment model of the formulas in the calculator, you must try and get these numbers as close to the same as each other. This calculator is designed to give the vertical length (height) of a quarter wave ground plane antenna, and the length of each of the four radials.

Tang Band Drivers You can use all the 3˝ drivers in this construction. My first test was with W3-926S, which I replaced with W3-315SC. The Tang Band drivers have a relatively high Fs and very high Qts, which means the rolloff is more gentle than a low Qts driver, and it is therefore possible to design a quarter wave with useful output well below Fs. However, high Qts drivers can be difficult to control. The whole idea with a quarter wave — or transmission line — is to extend the bass by the contribution from the opening. At the cabinet resonance, the output adds to the driver output. However, there are some unwanted higher harmonics, which are out of phase with the driver, causing uneven frequency response.

These problems can be solved by different design parameters, which I have successfully used with the TABAQ design. Figure 2: TABAQ design. Design The tuning frequency of the cabinet alone should be set lower than the driver Fs. Because the drivers all have a very high Qts, I started to see how low I could go, getting maximum bass performance out of the drivers without losing the overall frequency balance. After hours of simulation with Martin’s MathCad models, I found the best compromise was 55Hz, which is low for drivers with an Fs of 100 or 110Hz.

But it works! The tuning frequency is set by the length of the pipe and the geometry. A tapered pipe is shorter than a straight pipe for the same tuning frequency. TABAQ uses the mass loading principle, in which the last part of the pipe has a smaller area than the rest of the pipe. The air in this part of the pipe adds resistance to the driver (more mass-mass loading). Compared to a straight pipe, the length is shorter. The problems with unwanted higher harmonics are solved by driver placement, stuffing, and applied the geometry as in the mass loading. Rapidweaver The driver is one-third down the pipe, a common and well-known trick to attenuate the upper harmonics.

However, this is not enough, and damping of the cabinet is needed (as it is in every quarter wave). The damping is high (1 lb per cubic foot) and is placed in the upper part of the pipe. The last third of the pipe is not stuffed.

The stuffing will attenuate the output from the opening, so I solved this by increasing the volume of the cabinet. Increasing the volume also increases the output from the opening, so this compensates for the high density stuffing. The area of the pipe is four times the area of the driver (Sd). The TABAQ design is shown in Fig. Don’t be confused. This is not a bass reflex enclosure; it is a quarterwave.

Quarter wave box calculator

Figure 4: TABAQ compared to other designs. Cyburg’s Needle (top), Long Tall (middle), TABAQ (bottom). Listening Room Until now, I have focused on design theory. Real life is different, and I must deal with the baffle step problem, which generally applies to all full-range designs. You already know that a speaker placed in the middle of the room has a weaker bass than one placed against the wall. The same thing happens for the middle and high tones, which get extra help from the front of the cabinet. The result is a speaker that sounds bright with a focused middle tone. This “analytical” sound will be irritating after some time.