A remarkable (and small) two-way speaker

[Erik Mandaville]

I walked into the store's listening room and sat down about six feet away from a pair of slender floor-standers. Listening more carefully, I began to realize that the very coherent midrange and treble that even sounded exceptionally good far off axis was not coming from the speakers I thought, but from a considerably smaller pair positioned in the dark above them. Was this a trick to impress, or just a coincidence?

Granted I was only several feet away, but I have been more used to such comprehensive, full sound coming from a pair of 1960's vintage Klipschorns in the corners of our listening room. It seemed to me that based on what I was hearing, a subwoofer was probably part of the equation, and that turned out to be the case. It was rather far off to one side, though, and in that respect kind of discreet. The way these speakers pulled off the vanishing act was impressive. Had I the money on hand, I think I would have bought a pair on the spot.

Knowing I had some extra drivers from some years ago, I went home to my work room with the idea of putting together another two-way system. I have a pair that I made in the 1990s out of ceramic flue tile. They are virtually inert, despite the fact that one might be inclined to think that fired clay would ring. These things are over 1" thick, very firmly braced by a heavy wooden dowel, are almost totally non-resonant. As good as they are, I was inspired by what I heard from those in the store, and I thought I might be able to improve on the situation. It took me a couple of hours to cut through the very tough silicone adhesive that held the back panel to the enclosure, but it eventually came off. I had to remove it in order to change the length of the port for the pair of 6.5" woofers I selected from these:

[Erik Mandaville]

Guess work? No. There is a specific way of determing whether a driver is more suited to a sealed or vented enclosure. After once again determining the internal volume (almost exactly 14.5 Liters), an appropriate starting port length was determined, although the final tuning will be done by ear.

Enclosures with old drivers and back panels removed:

[Erik Mandaville]

Yes, those are Roland Electronic drums in the background. I did lots of playing in the past in bands, and Marie-Santa bought me a mesh-head set to start to get into it again.

So, the back panels were recut from MDF, the port re-sized and tuned to 50Hz, and glued into the cut-out with the adhesive I've always used for the purpose: Silicone sealant. After three days, the glue was still gummy -- obviously a bad batch. I pulled the ports out, cleaned everything up (PITA). The ports were glued in with another adhesive, and are tight as a drum.

I didn't want to use an outboard crossover this time, which isn't the best for home decore/WAF, but also didn't want to use up any more internal volume by installed the network on another board. Instead, I just attached the parts to the back panel. I built the networks after dinner tonight, and have glued the inductors down with the same adhesive. Mind you, this board will be once again glued-like iron onto the wooden enclosure, and will not lend themselves to find tuning once installed. I'm going to test with foam sealant, and then glue them down once and for all once everything, including the new acoustic foam, is sounding right.

Just for the record: This crossover was originally designed using LEAP (not by me). Testing the two pair of aluminum domes I already had, I found them well, kind of literally metallic and peaky compared to other doped silk domes I've used in the past. However, the one pair of Polydax tweeters seen above, which do have fabric domes, would not fit the round cut-out I had on the front baffle. I thus ordered another reasonably priced pair of Vifa tweeters from Madisound, and they have the same cut out and driver flange dimensions as the old tweeters I was using.

The port length was designed around the net volume of the enclosure, which accounts for the actual space used up by the vent, itself. It should be okay as is, but the old port I had in these same enclosures was about three inches too short.

Since the inside will never be seen, I didn't put makeup on them. The network is a simple first order low pass with impedance equalization, and the tweeter is a second order. I'm using Solen caps because I like a harsh, grainy, and unmusical HF response.

After testing, I'll glue the caps and resistors down, too.

[Erik Mandaville]

The out side is a little easier on the eyes. The very small two-way speakers that sparked this sudden modification were the Klipsch XB-10s. A really marvelous sounding speaker regardless of its diminutive size. Just for the record, I'm also a K-horn owner.

[Daddy Dee]

very nice Erik.

[Erik Mandaville]

Thanks, Dee. The inside of the cabinets look a little on the oriental carpet side. It's just some cheap, foam-backed carpet that I coated (about 15 years ago) with a thin film of silicone to help deaden the cabinet further. The old poly fill is removed, and new foam will be used to line the entire interior.

I've always liked two-way speakers, and the quality of sound from the little Klipsch XB-10s put me in gear to try another round using some speakers I had on hand. I'm eager to try out the new Vifa silk dome tweeters, but what I heard in the way of HF response from the XB-10s was curious in a good way. The tweeters in those things were really interesting.

I'm not trying to replace anything that I have; just trying some things out using manufacturer-provided specs for the drivers. Hopefully I will learn something in the process, and enjoy some nice sounding music at the same time. I'm going to try an in-line crossover for 100Hz to the subwoofer, which should help with power handling, and to keep the little 6.5" speakers happy at louder volume levels.

Erik

[darkside]

I really like the use of the flue tiles. Way cool indeed and great work!

[Mallette]

Looks marketable to me, Erik. Besides the obvious "audiophile in a tight space" use, looks like a great little control/production monitor as well. I've always learned a lot and gotten a big charge out of your experiments. I know you love teaching, but there are times I am convinced you are in the wrong business.

Dave