ML*TL = FLAT/SPL?
[Really interesting PIC goes here]
"I Think I Should Have Paid More Attention In Math Class."
The Missing Link
Mass Loaded Transmission Line... What the hell is that? Is this the Holy Grail of speaker projects? After discovering Martin King's web site and seeing the incredible amount of work he goes through for each project, including PDF documentation, measurements, and math worksheets, I knew there was a good chance this box would sound good with the FE208 driver. For docs and specs, go to Martin's site here. Hopefully, his correction circuit will cure the baffle-step problem and provide a better balanced presentation.
Here's a pic of the half completed cabs. The internal brace was added for two reasons... first to help hold up the stuffing and second to make the cabinet a bit more stiff. MDF was used throughout, except for the front baffles, which are birch plywood (not in picture). I glued tulle to the brace so that the stuffing would not fall to the bottom of the cab. Since I was going to paint the cabs before I mounted the terminal cups, I had to tape two runs of CAT-5 cable to the rear so that I could pull it out later to solder (not shown).
I will be priming the cabs this weekend or next, then the color scheme will be a black rear and a natural finish on the front birch ply, with tung oil applied for protection.
October 28, 2003
Here's the completed cabinet. It was stained and then finished with tung oil (I prefer a low-gloss look). I am still waiting on parts for the filter and zobel but I had to try out the speakers to see how much bass is available without the notch filter... seems like zilch! I then connected the filter I used from the horn - 1mh inductor, 2 uf cap, and 8 ohm resistor all in parallel and connected in series to the positive terminal of the speaker. That was a little better but I noticed that the speakers needed to be closer to the rear and toed-in more than I remembered with the horns. Placement seems key in getting decent imaging and sound. The placement of voices or singers in the soundstage is somewhat cloudy or unfocused. And there seems to be a small amount of hollowness and glare from the midrange... does this mean I might need to play with the stuffing directly behind and around the driver? I guess I will have to lug these back to the garage to spray some 3M-77 glue to coat the walls around the driver with stuffing. I think the stuffing may be falling down and exposing the bare walls at the back, top, and sides.
March 29, 2004
Sounds congested, like my stuffed nose when I have a cold. Played with the stuffing many times. No luck. Tried playing the speakers with and without filter. With the filter in place, everything sounded cloudy... overall just terrible. Without the filter, things were much more clear, louder, brighter, but there was no bass and no soundstage or image focus. I consider this a failure... On to another project.