soundminded

I would compare the dc resistance of the original inductor with that of the replacement. The replacement should be lower because the wire gage is greater. If there is much difference, I would wire a precision resistor of the value of the difference in series with the replacement inductor. My hunch is that the lower resistance would lower the value of Q, the resonance magnification factor. This would theoretically cause the bass response to drop off just a small amount. Anyway, that's how I'd compensate for the difference if I felt there was one and it meant anything. I'd be interested in your measurements if you make any and your comments. I was also hoping to get comments from Tom, Ken, or anyone else who'd care to give their thoughts about it. BTW, did you have the driver repaired? Did you find a suitable replacement? What happened? Don't leave us hanging.

Having recently studied the crossover schematic and design concepts of the AR9 which Tim Holl wrote up, I decided to take a look at the AR90 just to see what differences there are. I was especially curious about the low pass section for the woofers. I would say that if you rebuild this crossover network, it is important to reuse the original chokes (inductors.) Their DC resistance and current carrying capacity are critical to the design. They also work in combination with the final mechanical system resonance point and resulting electrical impedence versus frequency curve which is dependent not only on the drivers but importantly on the internal air volume of the cabinet and its air tightness. The design of the AR90 low pass section was surprisingly different from that of the AR9. AR9 was true to the basic concept while AR90 was much simplified not having the impedence equalization off resonance feature of the AR9. Perhaps the characteristic impedence of the drivers made that unnecessary. Strangely, the topology of the design of the crossover circuit for the upper midrange horn dome changed as well changing the 6uf choke to 8 uf and adding a 1.37 mh choke in shunt between the 24uf cap and the 0.2 mh choke. This should have changed the overall tonal balance between the AR9 and AR90 in that range slightly. Was this done to increase the power handling capacity of the system and reduce upper midrange driver failure at high volume? Perhaps Tom or Ken could shed some light on that. The program equalization switches used a slightly trickier arrangement using two resistors in series for the 6 db cuts where the AR9 used one resistor for -3db and another for -6db. No idea why but they are equivalent. I would think that given how critical the realationships are for matching the crossover to the drivers and cabinet, especially the woofers, this is one series of speakers where all of the production units would be checked or at least a fair random sampling of them would have been checked in each production run to be certain that the bass response conformed to the prototype within spec. While a lesser manufacturer probably would not have bothered, I suspect, AR would have made the effort. Personally, I'm of the opinion that in this case, "don't fix it if it ain't broke."

As I recall, the largest in the series was the floor standing W90. The double enclosure with sand fill between them was designed to damp out all cabinet resonances and I thought it was extremely clever. I've always wondered why nobody else seems to have tried it. As I recall, the W90 was a dual 3 way system, having two 3 way 12 inch systems in the same enclosure. It was their most ambitious effort at that time. Wharfedale was always regarded as a very high quality British manufacturer and their products were distributed by among others, Lafayette Radio and Electronics. Anyone recall their main store in Syosset Long Island or their large branch store on Liberty Avenue in Jamaica Queens? In the 1950s and 1960s these were among the largest retail electronics store outlets in the New York Metropolitan area. Oh how I wish I had saved their large and fascinating catalogues. They sold everything from Audio equipment, to electronics parts, to microscopes and telescopes including their own brand name products. Brings back a lot of memories.