rdp@teddy.UUCP (10/25/85)
>>I had the opportunity to compare the KEF 104/2 and the ADS L1590 >>loudspeakers. The KEF speakers were the hands down winner in >>my opinion. In fact, they were the best speakers I've ever >>heard. >> >>Mike Kaplan >I heartily agree. I have owned a pair of 103.2s for 3 years, and have been >almost totally satisfied. >Both the 104.2 and 103.2 suffer from a lack of low bass (I really like baroque >organ music.) One day, I will rectify this with a sub-woofer. I have for some time owned a slightly modified pair of KEF RS104aB's, and had sold the KEF line quite extensively during my tenure in the audio business. There are several comments I would like to add to the above. The KEF 104aB was one of the first speakers where lots of real research and design expertise came together to come up with a commercial product. The engineers, Micheal Berman and Laurie Fincham spent quite a bit of time and effort in thinking things out. One of the things they accomplished was attaining the desired acoustical response from the combined driver/ crossover system (thus the designation aB, meaning acoustic Butterworth response). This was an improvement moade to the original release of the speaker (also available as a retro-fit, for those that might have older 104's and want to upgrade) In any case. My major complaint with the speaker was its mid-bass coloration. KEF had attempted to produce a speaker with a higher than normal level of performance in a given price range, and had to make, as a consequence, some compromises. One of those was in the cabinet. The cabinet was/is constructed from high-density (but not the highest available) 1/2 particle board, with minimal internal bracing. The enclosure was then damped with about 1 1/2" of fairly reasonable foam. As a unit that could be manufactured at a given price, it was well done, but the result was an enclosure which suffered from, I felt, to much panel resonance and internal reflections in the mid-bass and low midrange (say 125-500 Hz). From that region on up, the speaker was as good as could be had practically, and decidedly better than most everything else. But the faults were obvious A solution became available when KEF announced that it was making the 104aB available as a kit. The kit consisted of the the front panels of the speakers with the drivers and crossover already mounted and wired, and damping material, (which doubled as the packing material!). All the buyer needed to do was build the cabinets to the supplied specifications. This, all at a price less than 2/3 the finished product (it may have even been 1/2, I don't remember exactly). Knowing what I did from my research into transmission lines and the effects of proper bracing and stiffness can have on perfromance, I built enclosures which, while having the correct volume, were considerably stiffer and better braced than the ones supplied by the manufacturer. The cabinets were built by first making a 1/2" thick enclosure of the correct volume from high-density (55lb/cu. ft.) chipboard. On the outside of this, a layer of 1/4" tempered masonite was securely glued, forming a "veneer", Then, another layer of 1/2" veneered chipboard skin was attached, making a 3-layer enclosure totalling 1 1/4" thick. Tests with my accelerometers that the amplitudes of cabinet resonances were reduced at most frequencies by a minimum factor of 5, and they were substantially better damped. Additionally, the internal damping was carefully chosen to reduce internal reflections. Braces were also added where deemed necessary. The result was a significant reduction in the (what I considered) objectionable mid-bass colorations. What was more interesting was that there seemed to be an extension in the deep bass, but I suspect (and measurements later pointed to) the fact that mid-bass anomolies were masking the low-frequency performance. If you count my time and materials, I may well have not saved anything in the long run, but there was an improvement in one of the last audible problems the speaker has. For those that have confidence in their box construction skills, the RS-104aB kits may well still be available (they were a year or so ago), and can provide the vehicle to getting a pair of high-performance loudspeakers at a reasonable price (~$400/pair). They are known as KefKit 104aB's. Dick Pierce
schwrtze@acf8.UUCP (E. Schwartz group) (10/26/85)
I own non-retrofitted 104aB's which I bought in England when I was in
school there. I spent a year mulling over them and I found them to be the
best speaker for the money, one that could stand up favourably to the 105 mk 1's
Kefs service in this country is also excellent, I had a new driver sent
in 2 days. (For u people curious as to why the driver (the B200) blew NEVER
let a friend fire up his homebrew amp initially though good speakers, you may
pay). Kef also has another new speaker out centered around the great B139 cone
This is an oval low freq element copied as an ABR (acoustic base resonator)
on the Kef104aB's. I am going to buy the new 104's just to have them I think.
Besides it must be time for an upgrade.
Hedley Rainnie
hedley@alaya
{ihnp4|seismo}|cmcl2|alaya|hedley