KatKit Single Driver Transmission Line Speaker System
| Introduction: There are several different names possible for this project, so I settled on the shortest,
the "KatKit," named after my sister Kathrine, for whom I built this system. Other possible names are:
"Portable Frugalphile HiFi," "Compromise in Transmission Line," or "Another Experiment
in PVC Transmission Line Construction." Form follows function, here, and so does sound reproduction. My sister wanted something to replace her boom box, which she uses to perform at church with split-channel music and to listen to music in a small room at home. In addition, the system had to be somewhat portable. Therefore, size and weight became an issue. Basically, we wanted a system that could be crammed into a box, then assembled and dissembled quickly and easily. So I needed to construct an entire system that would perform well in a relatively large space and a relatively small space. A small folded transmission line was the obvious solution, presuming that we avoid boxes at all costs because in heaven, there are no box-shaped speakers. However, how was a small folded transmission line also going to be lightweight? Furthermore, what kind of amplifier was going to drive a pair of TLs in these extreme spaces? Well, the solution is outlined below. Click on the thumbnails for more detailed pictures. |
||
|
|
||
| The Amplifier Enclosure Idea: Unfortunately, some practical issues proved this design to be untenable for a portables system, so I abandoned it for a project box. |
|
|
| Project Boxes: Here's your typical chipamp, with BrianGT gainclone PCB boards. This amp has absolutely no audible self-noise, and almost no DC offset. |
|
|
| Folded PVC: The 4-inch sewer grade PVC is lightweight yet sturdy. It is cut for a simple angular turn, which has many practical advantages over an elbow. |
|
|
| Speaker Construction: The trusty PC-7 epoxy I used with such success on the Seraphim was not reliable for such long pieces. Instead, I used some shelf brackets and home plumbing products (no free endorsements here!) to secure each joint. They are airtight. |
|
|
| The Baffle I: I came up with the idea of mounting the driver on the face of the pipe, firing it straight down the pipe. Again, this is to reduce size and weight of the KatKit. I used higher-grade 6-inch PVC pipe left over from a previous project as a ring. For the first ring, I cut the 6-inch pipe into two two+-inch pieces. After those where secured, I cut the 6-inch pipe into one 4+-inch piece. |
|
|
| The Baffle II: I think I may have inadvertantly stumbled onto something here. The 6-inch pipe pieces are under some fairly high tension. I was unable to secure them by hand. Considering the sound of the finished product, I'm wondering if I managed to kill some unwanted resonances in a key spot.. |
|
|
| Baffle III: Here is a detailed look at the completed baffle ring. After listening, I exclaimed to myself, "What BSC?" I cannot perceive any loss; or if there is, then these things are outperforming modelled expectations. |
|
|
| The Driver: This Vifa V2304B was available as a buyout special at Parts Express. Otherwise, it does not exist. Sounds great, though. |
|
|
| The KatKit: Lightweight, relatively small, very powerful, very flexible in application. The speakers are
unfinished and unmounted for the sake of the end-user. She can decorate them anyway she wishes, and the shape
and construction will allow her many different options for mounting them. The sound? The system sounds much better than a boom box; that's for sure. HiFi? I think it approaches hi-fi, but there are definitely some squiggles in the frequency response. The bass output is surprisingly strong. |
|
|
