In the days these terms were developed, in the '50s and '60s they were not linear. Hi-Fi was a generic term to mean an audio system above the then typical radio, including the floor standers and included more than or the ability to have more than 1 sound source, typically the tuner (well, radio) and record player. There were 4 subsets of hi-fi. Low-fi, mid-fi, high end and esoteric. Esoteric companies usually were making only 1 or 2 products such as Rabco or were so unknown that Joe Average would not generally know the company such as Jecklin and Van Alstine. Esoteric was both a sub set of hi-fi and one of the other subsets; an odd category. While most products fell into the high-end group, they could fall into any of them. High end was those products recognized as producing the best sound and having a somewhat limited distribution such as McIntosh, ARC and Krell. Mid-fi covered probably 20% plus of the market and was the staple of most of the popular audio companies such as Marantz (post-tube), Pioneer, etc. The better companies this group could and did produce sometimes a line or particular models that crossed over into the high end group, i.e. Marantz 500, 510 amps for instance as well as the CA-5000, CA-3000 and BA-3000 Sansui. HK produced the Citation line that generally crossed over to the high end. Low-fi, some times referred to as low end but I think that is a misnomer and was not used as a group back then but as a sub-group of each group of each group, is generally considered products distributed through mass merchandisers or through audio dealers that do not reproduce sound of sufficient quality to meet the needs of persons who use audio systems as a major entertainment source and are sufficiently experienced to notice sonic differences. Some companies concentrated in this market and crossed over into the mid-fi group. Some times they marketed under different names such as Panasonic and Technics, sometimes they made them look substantially different such as Sony. Hence the company itself forced the differentiation while some companies took pains to not differentiate chose to only offer certain models in one group to a dealer. Some companies crossed all 3 groups in some manner such as Sony, Marantz and others.
The problem is this is all smeared as to some equipment made back then as the collecting niche was created persons began to find that many low-fi units were as good as mid-fi units, especially in the low end (ahah) of the mid-fi group. An examples of this could be say the Sony STR 6046A or STR 3600 (think that was the model) receivers designed for distribution through mass merchandisers and only infrequently offered to audio dealers usually as a result of a dealer preparing a major sale and Sony wanted to participate, thin of the midnight madness sales. The 6046A looks quite different than the 6045 mid-fi receiver, low end receiver while sounding as good.
Confused yet? To compound this many persons apply the labels in a subjective manner based on their experiences or spending ability. This is not a condemnation. For instance, I was a lover of Marantz tube equipment and the 18 and 19 receivers. With the introduction or the 2x series many Marantz lovers, including myself considered Marantz had entered into the low end to mid range (at best) and the mid-fi market and Marantz for us became a low-fi company though it more realistically had become a mid-fi name. Also, someone affording and buying an ARC would more than likely consider a Citation amp and preamp as low-end (i.e. low-fi). As well, sometimes a company tries unsuccessfully to go into a new group and fails. McIntosh tried this with the Stereotech receiver. It tried to move into and compete against the better of the mid-fi receivers but the receiver was viewed as a lesser high end unit and competed against the company's 1900 rather than say a Marantz 2270.
Stereophile early on developed an alternative to this marketing / sound derived confusing system with the Class A, B, etc system then based on subjective listening test. Remember back the Stereophile did not accept ads. If there is a grading system, it probably was more reliable and consistent than the other system.
While most of my hobby life, I used high end and high end esoteric equipment within the past few years, the associated myth of sound quality has made me realize it does not mean anything in the vintage market.
Do not know if this helps to explain why it all seems smeared and confusing or only ads to the confusion.
... it does show how it can kind of all smear together like you say, and confuse the lines...
