RS 1354 2 Driver bass-reflex by Todd Lee A little history I happened upon these Radio Shack drivers a few years back (1989) when an acquaintance of mine was trying to unload some 'Rat Shack' stuff before he went on cruise (we were in the US Navy at the time). He had four 1354 drivers and some others. I thought the 1354s looked interesting so I made an offer and he accepted. It took another year before I'd get around to them, but I finally put these drivers to use. Two of them I installed in small bookshelf cabinets I built using 3/4" particle board, commercial grade (8"w-12"t-6"d), w/ a 2"id port, 3" deep. This was before I really new anything about box tuning. Needless to say, they didn't fair well. Compressed soundstage, poor bass, and the highs were non-existent. I replaced these 1354 drivers with RS 1284s, which yielded slightly better highs, but less bass. These saw limited use over the next 7 or 8 years, while I concentrated on projects for cars, and speakers for PA or DJ use. Then I got a computer. Enter the internet I'm not a computer buff, but I do like what this computer has done for me as far as education goes. I'd rather refer to it as the 'info-net'. I did a word search for speakers, and after much sifting, found some very interesting sites. Then in late '99, after much browsing, I happened upon the Single Driver Website, and subsequently, the Full-range Forum. I was amazed at how much buzz there was about Radio Shack drivers, especially the RS 1354. I had four of these that I had mounted in a bandpass design and was using with a rather large portable unit, which worked, well...ok. I wanted to try some of the designs I had read about, but the whizzers on the my drivers were removed some years back. After a few more months went by, I saw these drivers on sale at Radio Shack for $7.49US. I bought 8 of them. I had larger cabinets that I'd built a few years ago and was running the 1284s in them. The cabs were .35 cu.in. internal volume and tuned to about 70hz. I placed the 1354s in them, and while they sounded better than I'd remembered them, they still weren't much in the bass department. I used poly fill for internal attenuation, but found that I couldn't get a happy medium trying different amounts. I decided to try 1/2" foam carpet padding, lining all the internal walls. This was much better, with better bass IMO, and slightly better HF extension, though not great. They did image very well how ever. I experimented with dammar, to the extent that I had put three coats on these drivers. It reduced the peakiness, but I found later that three coats on the main cone were over-kill. I also realized that the cabinet was too small. But this little project educated me on a few points, which were necessary in propelling me to my next project. Also, I asked a ton of questions on the Full-range Driver forum... more on this later. The Project I decided that I'd build a larger cabinet, perhaps try a line array design (because I had 8 drivers), but decided to stay within my comfort zone. I wanted something a little more efficient, but didn't want to build a horn. I saw an old set of Radio Shack speakers in a pawn shop that had real wood veneer, and an internal volume of 1.5 cu.in., enough for three drivers. I decided on two drivers, wired in parallel, with a RS linaeum tweeter module to extend the HF. I wanted to keep the purity of a full-range design, so I eschewed any contour circuits, however I did replace the cap in the tweeter mod with a 1uf cap. I carefully cut out the front baffle of the old cabinet, (leaving a 1/2 lip around the edges) and replaced it with one that would have the cut-outs for my two 1354s and the port. I wanted a 1" thick baffle. So I cut two pieces of 1/2" commercial grade particle board, one smaller than the other, and glued them together. Since the original baffle was recessed 3/4inch from the leading edge of the cabinet, I wanted to extend it closer to the edge. I don't own a router, so that's why I made the new baffle laminent with two different sized cuts, the inner piece would fit between the 1/2 lip I'd left from the old baffle, and the outer piece would fit snuggly between the cabinet walls. I was able to do this quite precisely with my Father-in-law's very nice Delta industrial table saw. So precise in fact that there is no air escaping around the baffle, even without glue or caulk (I will caulk eventually) The front baffle is still recessed slightly. This will facilitate my covering, which will be a tube stocking type. I lined the rear and top insides of the cabinet with 1/2" thick foam carpet padding. This was one of those tweaks I'd learned in my previous project. I thought that I might not need as much attenuation in a larger box. I feel I was right. The box is tuned to 55hz with a 3"i.d.-by- 3.25"long port made from schedule 40 PVC pipe. the 1354s are aligned vertically and off-set from the center of the baffle, left and right respectively, with the port directly below, firing forward. The Sound I was a little disappointed with the sound at first, even though I gave these drivers at least a 100 hours of break-in. I did not dammar these drivers because I wanted to see if they'd improve with break-in alone. They did, but only a little. I removed them and varnished them, 2 coats on the main cone, 3 coats on the whizzers (after listening to the previous project I decided that it sounded better than just two coats, but YMMV), and 5 coats on the dome, or dust cover. This last step was derived from all that I'd read on the subject of dust cover tweaks, from burning a hole through the dome to placing small pieces of tape to the dome. I think that a super stiff dome sounds IMO better than a mere two coats. Plus, the domes look way cool, as the extra coats make them real shiny. I can now say with all confidence that the Dammar varnish tweak is quite possibly the best, most effective tweak I've ever heard. I also dampened the frames with a heavy caulk and I place foam stick tape on the insides of then frame as well. I can drive these things hard. Before (in the single driver design), I got such a sqwaking mid-range and HF distortion from these, but I think the extra coats on the whizzer and dome, as well as the frame dampening alleviated that. I get such bass from these, they even hold their own with my Polk Audio SDA CRS+ (two 6.5 mid-bass drivers in a slightly smaller box, w/ 10" PR and Linaeum tweeter mod). Very refined sounding. Better, deeper bass than my previous project, due to the larger cabinet. Also, I think that the mids and HF sound better in the bigger cabinet. These image very well also, even better than my $700 Polks. Conclusion I'm very pleased with the sound of these speakers. I was shocked by the difference that varnishing made. And I'm pleased at how little money I've actually got into these things. One observation: although I'm pleased with these speakers' ability to image, it is my opinion that the best imaging and coherence is derived from one full-range speaker. Of course, this is not a news flash to most of you. The two driver set-up is more efficient (plays louder) and has more bass and I feel I only need the super tweeter on certain material. I do not use the loudness circuitry on my amp (too muddy), but I do use a graphic EQ in my system, which consists of a CD player and a solid state amp. (sorry, bottleheads) I believe that if one were to build a .8 cu.in. or 1 cu.in. cabinet for one of these drivers, bass-reflex tuned to around 50-60hz, you'd have a pretty darn good speaker for real cheap. Thanks to all at the full-range driver forum. My interest in DIY had grown stale until I found this site. I am by all means, a novice at DIY speaker building. The fact that I was able to create such a good sounding speaker is credited to those on the Forum who put up with my questions, as well as taking the time to answer them. Top