Vintage Japanese Drivers
One of the main reasons audio lovers have been apprehensive about getting into single ended micro power amps is the relative scarcity of efficient speakers. There are a few decent commercially available units but they are hard to find and audition. DIYers have discovered Fostex drivers which are not cheap but some of their mid-priced models are affordable and represent good value for the money. Prices asked for vintage WE, Altecs, EVs, Jensens and etc. have soared because of the demand from collectors. Another complicating factor is the size of vintage horn systems. Aficonados have also discovered old German radios and consoles from Telefunken, Saba and Siemens.
Vintage Japanese speaker units are just beginning to be appreciated. Prices at eBay for desireable Pioneer and Coral, full range, coaxial and triaxial units are starting to rise due to collectors and SE amp users realizing their merits. Look for old stereo consoles or table top radios and even early solid state models. The logic behind this is, power was at a premium in those days and for mass market consumption, manufacturers used efficient drivers to fill the living room with sound from amps with less than 10wpc. Likewise some of the speakers [plywood cabinets usually indicate good drivers inside] that were sold along with compact stereo systems are good candidates for SE amp use.
In my opinion, some units like the SK98, is on par or better than some of their Altec or Jensen counterparts. The others are good alternatives to mid-priced Fostex drivers which can be acquired cheaply at thrift stores.
The following drivers are no longer easy to find especially the alnico models, but the ceramic versions sound good too. These still come up at thrift stores or maybe sitting in the basement or attic of an older relative. This list is notcomprehensive, it is just a guide for those of you who like rummaging through yard sales, flea markets and thrift stores. Enjoy!
6" Full Range
Pioneer PIM16 OEM for Lafayette as found in SK124 bass reflex cabinets. This is the predecessor of the PE16M re-issue.Mechanical "2-way", perhaps a Japanese interpretation of the Altec "Bi-Flex"? MJ issue no. 2/2001 listed the following specs for this unit: 3W nominal, 70-16Khz frequency response, 11,000 gauss 850 gram Alnico magnet, 90db/1W/1M sensitivity and Fs = 70-85hz. Introduced in 1959.
Found inside a pair of Sony speakers originally sold with a compact system at department stores.
Same story as the Sony above, but these came from Panasonic branded boxes.
Another Panasonic but bigger magnet, 16 ohm voice coil and a whizzer cone.
Sonic Impressions - The PIM16 is probably the best of this bunch, it has slightly less bass response than a DiatonePM610B but the midrange is more 3 dimensional and has a smoother top end. The Panasonic RAS16PO2 above is also pretty good, although one can hear a slightly grainier midrange and top end, perhaps due to the ceramic magnet. The Sony and other Panasonic are decent too but not in the same league as the latter two.
I use these drivers in a recycled Coral cabinet - 14.5"H x 10.5"W x 8.75"D approximate outer dimensions and built with 3/4" plywood.
I modified this into a bass reflex by replacing the front baffle and back cover with a 1.5" x 4" rectangular port with light poly-fill damping.
I use them as rear surrounds but they are also ideal SE friendly mini-monitors for those who live in small apartments or dormitories. I have tried them also in open baffles, but given the foot print of the baffles and the frequency range of a 6" driver, I don't deem it practical since a decent 8" can give better bass extension.
8" Full Range
Lafayette SK98, the 1961 catalog list the following specs: freq. response = 40-16,000 cycles, Fs = 55-70 cycles, 99.5dB/watt sensitivity, 10,500 gauss/56,000 maxwells alnico magnet and 8 ohm voice coil. Notice the similarity of cone construction to the above Pioneer PIM16 and PIM8L below. I'm almost sure these were Pioneer OEM units.
This Pioneer PIM8L is very similar to the SK98 with economy cosmetics - bare metal frame and no magnet cover. Voice coil impedance is 16 ohms. These 8" drivers are pretty damn good sounding, Perhaps these are Japan's answer to the Altec 755. I rate them as the equal of a 755C or 755E with a slightly lightweight presentation. If I'll draw a car analogy, it is rather like a Honda Civic Si, smooth and high revving but light on torque as opposed to a torquey VW Golf GTi [755C or E].
Lafayette SK58 12" driver with a co-ax mounted 3" cone tweeter. I modified the crossover slightly to get rid of the slight upper midrange harshness by adding another 4uf cap in series with the stock 4uf paper in oil can type. This shifts the crossover an octave higher and sounds smoother, very efficient not quite the snap in the midsas the SK98/PIM8L and the 3" tweeter not quite extended but still very satisfying.
Pioneer PT-3K horn tweeters came with the PIM8L above. This tweeter is in between the size of an Altec 3000 and Jensen RP103 with a 1 5/8"H x 4"W horn mouth. 16 ohm voice coil and 2.8khz recommended crossover. I use it as a super tweeter [x'over above 7khz] and this unit sounds sweet, silky and extended highs. Better than the Fostex FT17H in my opinion. Not quite as good as an Altec 3000 but quite close.
Trio/Kenwood horn tweeter Jensen RP103 clone[?], same horn dimensions. Can't remove the magnet cover but my gut feel is that this uses a ceramic magnet, the diaphragm is probably mylar. Not quite as articulate as an RP103 but slightly more extended in the top end.
Sonics AS-304A, 70s Japanese 4-way speaker with a 12" woofer, 5" midrange, 2" cone tweeter and horn loaded super tweeter. I guesstimate efficiency to be in the lower 90s but plays loud with an SE2A3 amp. It can be used "as-is", but for best sound I probably will pull out the drivers and mount the purest sounding combination of woofer + high frequency driver in an open baffle.
Have fun and happy listening!