[2008-06-23]

I have been playing around with trying to combine the virtues of fullrange drivers with enough bass to be happy. I started with my Fostex FX-120 and Eminence Alpha 10 configuration, but the boxes would have to be huge, and that ain't gonna fly in my puny listening room. In fact, I need a bookshelf solution. Currently I am listening to a pair of AR-4x bookshelf speakers with modified Dayton Silk Dome tweeters. they are pretty good, and the bass is fine, but they just don't have that fullrange magic that I have come to love.

2 things happened that made me scrap my "just add a big woofer" plans and return to pure fullrange speakers. The first was the opportunity to hear Robert's Nagaoka Swans. Those goofy looking speakers blew my mind. Looking at them I had an idea of how they would sound that included a lack of midrange weight owing to the super tiny baffle area. Well, they had weight to spare. They sounded amazing, and had all the bass and midrange weight I could want. I mean sure, like all fullrange designs, they miss an ocatve or 2 of bass, but I can live with that.

The second thing was while discussing this with the Audionerdz, Robert came up with a design I hadn't seen - the Bigger is Better (BiB) horns. The Bib are basically an oversized folded TQWT designed using Martin King's Mathcad models. This design seems to be very popular and can be made to work with just about any driver. And construction is about 50 times easier than the Swans!

So I picked up a couple sheets of AC plywood (I would have preferred MDF, but they didn't have it) and went to work. These speakers are very easy to build, and I had them put together in about 3 hours. As faithful BZL readers will remember, I hate finishing work, so they are pretty rough, but they do play music and I was going for more of a prototype than a finished speaker.

I decided that I didn't want the horn terminus to face upwards. I was imagining a cat falling in there and not being able to get out. Plus I like th elook of a traditional forward-firing folded horn, so I reworked the design a bit. I turned it upside-down and added a 90 degree bend so that the horn opening is floor loaded.

Here are the completed speakers in my listening room - the "Boon Boom Room". I forgot to add binding posts while I was building them, so the cables come out of the horn. I added a bit of Polyfill below the driver, and a 12" sheet of imitation wool carpet padding behind the driver, which clarified the midrange dramatically. I thought I might be able to get away with using only a single layer of wood on the front baffle because it was so narrow, but I think the front baffle contributes a significant amount of sound, blurring the image and adding a peak in the upper midrange. Next time, I will make the baffle 1.5" thick, and use at least one layer of MDF.

While the midrange is great, there is plenty of lower midrange weight, the treble form the FX-120 is very smooth and listenable, and the bass down to about 50Hz is effortless and well balanced, there is just plain nothing lower than that. I think this is a function of the relatively high Fs of the FX-120 and of the horn design, which rolls off more quickly than a sealed box for example. I am also a little worried that perhaps the added fold makes the horn effectively shorter. I think the next pair will have to do the added fold a bit better, or maybe remain an upside-down BiB that is simply raised off the floor by some amount.