NEWSFLASH: A rehash of old info that pertains to this new thread about old gear : )
I was digging through some audio rags and ran across some information that might explain some of the variances regarding these amps. Moncrieff of IAR stated that the majority of the Nelson Pass designed Threshold amps were quite load sensitive. As such, changing speakers and / or cables could change tonal balance to a very noticeable degree. Depending on the impedance / type of load that the amp was seeing, the tonal balance could swing one way or the other. Since Nelson designed the Forte' amps, i would imagine that much of this syndrome carries over to that product line also.
According to what "J. Peter" had to say, these amps could sound bright and thin if used with speakers that were relatively resistive by nature ( non-reactive ) and / or had a relatively higher average impedance. Going to a speaker that was higher in reactance and / or lower in impedance would tend to bring the amp closer to a flat response or even towards the warm and rolled off side of neutral. I think that THIS explains a LOT of what we might be encountering with these amps.
Since most of my speakers are of lower impedance than average and generate a relatively high amount of reflected EMF due to large motor structures ( making them more reactive than resistive ), one could see how i might hear them as being relatively well balanced & smooth but still lacking in extreme bottom end. Hooking them up to speakers that were nominally 8 ohms or so and resistive might give me similar results to what others have already commented on.
So, in plain English, EVERYBODY is "right" on this one. Given the variables with all of our experiences and selection of speakers / cables / support components, these amps could end up creating quite a varied response from user to user and system to system. This goes to show just how important it is to check a component in YOUR system when striving for the ultimate in "system synergy".
With all of that in mind, it kind of confirms what cables i've found to work well with these amps. For the record, i've always liked Goertz the best with these amps. The fact that they are highly reactive ( capacitive ) by nature and offer a much lower nominal impedance ( about 2-4 ohms ) than most other cables somewhat confirms what Moncrieff stated. Chris VH's 27 pair Teflon CAT5 design actually gave me the most bass foundation, but i found the Goertz to be quite a bit more liquid in the mids with more air and detail up top. Since both of these cables are capacitive and could cause wide bandwidth amps to oscillate, i would recommend the use of Zobel Networks should someone else choose to use either in their system. Other speaker cables that i've tried in this system are Kimber's, XLO, Audioquest, Axon, Monster, YBA Diamond's, etc.. and various home-brew designs. While some sounded notably better than others, the Goertz are still hooked up in this specific system.
Hope this helps and explains some of the variables that we've encountered along the way in this thread. I would be curious as to find out if the other "fans of Forte" are using low impedance / reactive speakers and what type of speaker cables that they are coupled to. Sean
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