For a short period of time, the audio store I worked in, sold those DCM's. If that's the speaker I think it is, it was a tower, with these excruciating grill covers. They were like a wrap-around "sock." Almost impossible to get on and off if you had to service them.

On the bright side, they sounded fantastic. (No pun intended.)
Yep that’s them.
I think Time Windows were the only reasonably priced vintage speakers that I wanted that I didn’t find somewhere in the heyday of used audio that was the mid ‘00s. I had a pair of the flatter DCM Timeframes but they didn’t sound as good- I bought them in Skokie which seemed really really far away. Now I like right next to Skokie.

Stereo-chasing is what introduced me to the Chicago area.

Doorway fun!
My own "doorway" was probably our old Admiral hi-fi console in the basement. Mono, with a tube amp that hummed. My dad changed out the Admiral changer for a Heathkit since my grandfather was upgrading to a Garrard Synchrolab...and probably because our changer was worn out. The "doorway" part is when he resurrected the Admiral's original speaker (he had replaced it with a newer/better speaker) and stuck it into a box and ran about 30 ft. of speaker wire to stick it on the other side of the basement.

That started the tinkering. Once he decommissioned the Admiral a few years later, I'd had him build a box for the Admiral's other speaker, and used those with a GE record player I owned, as they sounded better than the plastic cubes it came with. I built my own stereo amp from an IC as the centerpiece of a stream of cheaper components (that I could afford on my lawn mowing budget in my mid teens) that came along.

My grandfather's Heathkit building, and his cool Heathkit system in the living room, were also a fascination. Not a doorway because I didn't own it or have it under my own roof, but a huge influence. And I'm still kicking myself that my uncles stuck the old console he had installed all these components in at the curb when they cleaned out the house--had I known the Heathkit integrated amp ever would have been worth anything, I'd have grabbed it and cleaned it up for myself.
It was a Heathkit manual that taught me how to solder, when I was 13 - 14 years old. Still one of the best explanations I've seen to this day.

An entry-level unit in a particular room/category.
You can certainly go higher in level/quality/performance, once you go further into the figurative room (passed the doorway entrance).

Or…Oxford Dictionary:

  1. an entrance to a room or building through a door.
    "Beth stood there in the doorway"
it seems that "doorway" is used here the way that "gateway" is used in some other contexts. the thing that introduced you to audio
It was a Heathkit manual that taught me how to solder, when I was 13 - 14 years old. Still one of the best explanations I've seen to this day.
One of my uncles took some of the Heathkit home study courses offered back in the day, and even built a television that was part of one of those courses.

Their instructional books on electronics basics were so well written and organized that our school's electronics courses switched over to Heath's coursebooks. Our instructor had a bit of an uphill climb trying to get them approved by our district's school board but was finally successful. I had the original textbooks in my first year of electronics and they were typical "school-ish" textbooks with dry textual content about theories without much context, and typical "what have we learned?" questions at the end of each chapter.

The Heath books on the other hand were more conversational, but that made them more engaging, and the writing style made each concept easy to understand. (Even if it took an additional reading or two of the eventually clicked.) So much better than the dry theoretical concepts in the traditional textbooks. I think this is due to the writing style that made the Heath courses essentially a self-teaching exercise, whereas the traditional books were designed to be lectured as part of a daily class session. Not that our teacher quit lecturing, but it was more for reinforcement of what we'd read, vs. having to expand on the dry concepts in our old textbooks.

I wish I had a set of those books now, as I've forgotten a lot of those concepts over the years. We would work through two of those books per year, and I remember our third year was getting into logic systems.
Yup. I agree. And I wish I had built one of those Heath guitar amps. I've heard that they sound killer. I think it was a variation, (or clone), of the Sears amp, that was designed by Nathan Daniels of Danelectro fame.

But don't quote me on that.
And I wish I had built one of those Heath guitar amps.
I wish I could have built anything substantial from Heathkit. But by the time I had a job and could pay for anything myself, that was around the time that Heath's owner (Zenith) decided they needed to be a computer company, not an electronics kit manufacturer. I only built a few small things. I also built a stereo FM tuner for the car that never worked (it was a kit closeout, drastically reduced).
We built some of the Heathkit computer stuff (H-89-era) when I was in grad school. It was fun.
I've also built a whole bunch of the 400 VDC power supplies, which many labs used for electrophoretic separations of proteins. The undergrad biochem lab used them, too. I built about 8 of 'em for them one summer (and even got paid a bit for the effort, a win-win!). :)