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dB616TLC

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This project is a center channel version of the dB616TL two way, dual woofer transmission line. The concept is for an inexpensive center channel that provide full range output and match the dB616TL in tonal balance. The cost of the TLC is about the same as one dB616TL -- about $96 not counting veneer or whatever finish is applied.

The drivers are the shielded versions of the infamous PartsExpress 6 1/2" woofer and 1 1/8" silk dome tweeter and are the same drivers used in the shielded version of the dB616TL.

The arrangement of the drivers on the baffle is designed to reduce horizontal off-axis lobing which would occur if the drivers were arranged in a horizontal line.

The multiple folded line provides approximately the same line length, cross-sectional area, and taper as the main speaker. That results in a big (!) center channel speaker.

Note to potential builders: Before you decide to build this speaker, here are a couple of comments:

1. The enclosure is not as easy to construct as it might look at first glance. It is helpful to have access to a table saw/radial arm saw and to have some experience using a router -- or have somebody helping who has. There is also some work involved in getting the stuffing and acoustic foam installed and it may need to be adjusted by listening.

2. The design goal of this, and most transmission line speakers is, to produce bass which is non-resonant and smooth. If you're looking for loud or hard kicking bass, this isn't the correct design.

3. If you have any questions about building the dB616TL, please e-mail me.

Comments or Questions, e-mail: mailto:dbrown_removethis_@d-web.com

The following are some pics of the construction and more detailed drawings are farther down the page.

All miters are cut 45 degrees. Assembly is fairly easy and even easier if all the 8 1/4" pieces are cut on the same saw set-up so they are all exactly the same width. After that, it's just a matter of careful measurement of part location. I started gluing the front baffle then the angled sides, then the sides, then the back, and then all the internal pieces.

BTW, I cut the top and bottom 1/8" oversize all around for the router trim method. I also made the back 1/8" longer each end for the same reason.

Some creative clamping may come into play.

The bottom hatch took me the longest of any part. Lots of cut and try. If you can think of a better way, go for it!

All assembled an routered. Pic shows the hatch in place.

Another pic of the front routered and flush-mounts done.

Here is the drawing with the individual parts shown. I think all the bugs are worked out of the drawings -- trust me, I found several during construction! But, if you find anything wrong, please let me know.

Here is a drawing that may help in showing how I did the bottom hatch. You can use any method you want, however, the hatch is needed to access the center line for stuffing.

A base isn't really necessary, however it can help raise the speaker a bit higher above your TV/monitor if you experience any magnetic distortion on the screen. It's built in the same style as the "Lefty-Waldron" base used on the dB616TL main speakers.

Here is the crossover design. Basically, the components are all the same as the dB616TL except for the tweeter L-pad resistor values.

Here is the SpeakerWorkshop simulation of the crossover.

These are SPL measurements -- speaker laying horizontally: on-axis (black), 30 degrees off axis (pink), and 45 degrees off axis (yellow). The midrange shows a degree of off-axis lobing which is due to the driver arrangement. This nulling effect could be reduced somewhat by rearranging the drivers on the baffle to create a sharper inverted "V" however, I elected to go with this using the logic that the primary seating position is going to be on axis. The crossover could also be adjusted either by changing components to create phase differences or by increasing the overlap to produce a flatter off-axis response. My initial listening to movie soundtracks has revealed that this phenomenon is not noticeable -- so, for now, it will remain as is.

Having only recently set up my home theater, or at least a test set-up in my living room, I have found that the dB616TL and dB616TLC perform very dynamically. They will play loud and, even with the small sub I currently have set up, they come very close to anything I've experienced in a real theater.

By the way, with the way this is set up, I don't see any distortion on the screen of my little 13" TV. As you can see, it's about 6" from the shielded tweeter.

My wife even likes it. At least she like the way the system sounds...and is even tolerating this combination of unfinished speaker cabinets and piles of electronics...at least for a while. Our plan is for a house renovation/addition which will result in a room specifically for a home theater or, more accurately, a multi-purpose room optimized for home theater. Hopefully construction starting this coming spring : )

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dB616TLC	Back to Speakers
This project is a center channel version of the dB616TL two way, dual woofer transmission line. The concept is for an inexpensive center channel that provide full range output and match the dB616TL in tonal balance. The cost of the TLC is about the same as one dB616TL -- about $96 not counting veneer or whatever finish is applied. The drivers are the shielded versions of the infamous PartsExpress 6 1/2" woofer and 1 1/8" silk dome tweeter and are the same drivers used in the shielded version of the dB616TL. The arrangement of the drivers on the baffle is designed to reduce horizontal off-axis lobing which would occur if the drivers were arranged in a horizontal line.

The multiple folded line provides approximately the same line length, cross-sectional area, and taper as the main speaker. That results in a big (!) center channel speaker.
Note to potential builders: Before you decide to build this speaker, here are a couple of comments: 1. The enclosure is not as easy to construct as it might look at first glance. It is helpful to have access to a table saw/radial arm saw and to have some experience using a router -- or have somebody helping who has. There is also some work involved in getting the stuffing and acoustic foam installed and it may need to be adjusted by listening. 2. The design goal of this, and most transmission line speakers is, to produce bass which is non-resonant and smooth. If you're looking for loud or hard kicking bass, this isn't the correct design. 3. If you have any questions about building the dB616TL, please e-mail me. Comments or Questions, e-mail: mailto:dbrown_removethis_@d-web.com


The following are some pics of the construction and more detailed drawings are farther down the page.

All miters are cut 45 degrees. Assembly is fairly easy and even easier if all the 8 1/4" pieces are cut on the same saw set-up so they are all exactly the same width. After that, it's just a matter of careful measurement of part location. I started gluing the front baffle then the angled sides, then the sides, then the back, and then all the internal pieces. BTW, I cut the top and bottom 1/8" oversize all around for the router trim method. I also made the back 1/8" longer each end for the same reason.

Some creative clamping may come into play.

The bottom hatch took me the longest of any part. Lots of cut and try. If you can think of a better way, go for it!

All assembled an routered. Pic shows the hatch in place.

Another pic of the front routered and flush-mounts done.

Here is the drawing with the individual parts shown. I think all the bugs are worked out of the drawings -- trust me, I found several during construction! But, if you find anything wrong, please let me know.

Here is a drawing that may help in showing how I did the bottom hatch. You can use any method you want, however, the hatch is needed to access the center line for stuffing.

A base isn't really necessary, however it can help raise the speaker a bit higher above your TV/monitor if you experience any magnetic distortion on the screen. It's built in the same style as the "Lefty-Waldron" base used on the dB616TL main speakers.

Here is the crossover design. Basically, the components are all the same as the dB616TL except for the tweeter L-pad resistor values.

Here is the SpeakerWorkshop simulation of the crossover.

These are SPL measurements -- speaker laying horizontally: on-axis (black), 30 degrees off axis (pink), and 45 degrees off axis (yellow). The midrange shows a degree of off-axis lobing which is due to the driver arrangement. This nulling effect could be reduced somewhat by rearranging the drivers on the baffle to create a sharper inverted "V" however, I elected to go with this using the logic that the primary seating position is going to be on axis. The crossover could also be adjusted either by changing components to create phase differences or by increasing the overlap to produce a flatter off-axis response. My initial listening to movie soundtracks has revealed that this phenomenon is not noticeable -- so, for now, it will remain as is.

Having only recently set up my home theater, or at least a test set-up in my living room, I have found that the dB616TL and dB616TLC perform very dynamically. They will play loud and, even with the small sub I currently have set up, they come very close to anything I've experienced in a real theater. By the way, with the way this is set up, I don't see any distortion on the screen of my little 13" TV. As you can see, it's about 6" from the shielded tweeter.

My wife even likes it. At least she like the way the system sounds...and is even tolerating this combination of unfinished speaker cabinets and piles of electronics...at least for a while. Our plan is for a house renovation/addition which will result in a room specifically for a home theater or, more accurately, a multi-purpose room optimized for home theater. Hopefully construction starting this coming spring : )
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