Ralph: I did not write that there is a correlation between the "size of the woofer and the ability for the amp to control it". What I was trying to convey, but did not do so clearly, is that the vast majority of tube amps do not have the high quality output transformers or beefy power supplies needed to control the woofers of the average audiophile speaker, which these days tends to present a 4 ohm load or less on average in the bass. To fill in the blanks for this gentleman, it takes twice the current to drive a 4 ohm speaker than it does to drive an 8 Ohm speaker, all things being equal. In rough terms, the output transformers convert voltage into current, and in my experience, only the very good ones (i.e., very expensive ones) do this with the efficiency required to drive low-impedence speakers with authority ("authority" meaning tight, accurate bass). The role of power supplies is to house and supply the voltage that is processed by the output transformers, and big power supplies are needed to allow a tube amp to properly drive low impedence (i.e., 4 Ohms or less) speakers because such speakers require a lot of current. There are very well known 750 watt/channel monoblocks that cannot control the woofers of typical 4 ohm speakers because they use mediocre output transformers, while there are also 8 watt/channel tube amps featuring extremely high quality output transformers and huge-ass power supplies that can very effectively control the woofers of low impedence speakers.
In suggesting a speaker of 8 Ohms or more, what you are suggesting is not inconsistent with what I wrote. Of course, most of your designs are output transformer-less, which is why you advocate an 8 Ohm speaker. Again for the author of this thread, an "output transfrmer-less" tube amp is, as the name suggests, a tube amp that has no output transformer. The advantages of such an amp are greater purity and immediacy, with the downside being that, generally speaking, they do not do well with low impedence speakers (maybe your very expensive products can, but they would present an exception to the rule). The problem is, other than horns, the majority of audiophile speakers feature an average impedence well below 8 Ohms, which is why I provided the above advice, which I stand by. Please don't get me wrong - I know you build top-quality products and have myself owned a zero-feedback, triode power amp for many years now (VAC Renaissance amps) - but with a typical 4 Ohm speaker, which is most of them these days, I believe it takes a really fine tube amp, i.e., something with top-notch transformers and lots of capacitance, to provide tight bass.
In suggesting a speaker of 8 Ohms or more, what you are suggesting is not inconsistent with what I wrote. Of course, most of your designs are output transformer-less, which is why you advocate an 8 Ohm speaker. Again for the author of this thread, an "output transfrmer-less" tube amp is, as the name suggests, a tube amp that has no output transformer. The advantages of such an amp are greater purity and immediacy, with the downside being that, generally speaking, they do not do well with low impedence speakers (maybe your very expensive products can, but they would present an exception to the rule). The problem is, other than horns, the majority of audiophile speakers feature an average impedence well below 8 Ohms, which is why I provided the above advice, which I stand by. Please don't get me wrong - I know you build top-quality products and have myself owned a zero-feedback, triode power amp for many years now (VAC Renaissance amps) - but with a typical 4 Ohm speaker, which is most of them these days, I believe it takes a really fine tube amp, i.e., something with top-notch transformers and lots of capacitance, to provide tight bass.