Sunn stuff is not reknowned for its clean headroom or shimmering treble.
It's more in the Ampeg end of the spectrum. Pretty much always a little dirty, and sounding most excellent if you want it to get really dirty.
That isn't my experience with Sunns at all.
I'm referring to the vintage tube amps as I don't care much for transistors in MI amplification, but in fact one of the reasons Sunn was less popular with
guitarists in their peak years is that guitar was transitioning away from the 50's and 60's squeaky clean guitar tone and a more distorted dirty tone was becoming the preferred style, and Sunns were just
too clean for most players.
Bass players still wanted the big clean headroom, so Sunn became more popular with the bottom feeders than with guitarists.
Of course
any amp in need of maintenance will get distorted, as will
almost any tube amp that's run wide open, but my
healthy Sunns are far more Hiwattish than Ampegish.
Not quite as crisp and clean as a Reeves or Hiwatt, but certainly more defined and dynamic than an Ampeg, and tonally closer to the Dave Reeves circuits.
I have actually heard a few Sunn 2x15 cabs that sounded huge. Mostly the shelf ported TL606 style cabs. Though there are a few oddball ones that sunn made, such as the 4x15 cabinet and the diagonal baffled enclosures. The main problem with most of them isn't the cab (seriously they are built better than some houses) it's the speakers.
The
original Sundholm era Sunn bass cabs, the 200S and 2000S, are
huge sounding cabs.
The "oddball" cabs were Hartzell era designs, and the Hartzell era is also when Sunn cut back tube amp production dramatically and transitioned to almost all transistor amplifiers. In defense of Hartzell engineers, they were just trying to stay on the cutting edge, in the early 70's
EVERYBODY was going solid state; not just the MI industry, the entire electronics universe.
For the vast majority of applications its infinitely better, and even more so more practical.
It took a decade or two for people to realize, and the MI industry to react to, the fact that tubes just
sound more musical, and for tube MI amps to have a resurgence in popularity that they still enjoy today.
The Hartzell era stuff has a strong following, but IMO is a totally different animal from the Sundholm designed gear.
The shelf port Sunns are actually just Fenders wearing Sunn badges
As far as Sunn speakers, JBL D130F and D140F were OEM for Sunn cabs until 1972. Whats the problem with those? They dont handle the
power of modern drivers, but they sound magnificent and when you are using 200-300 watt amps how is power handling really an issue?
Exactly. Sunn was great when you could buy a beta bass for $100 and nobody wanted those "weird, ugly" tube amps with the slanted fronts.
At collector prices I'd rather buy a Hiwatt or Superbass.
I never did like the slanted fronts either. I
still think they look a little goofy, but old Sunns are still a
bargain compared to old Hiwatts and/or Marshalls.
If the OP wants to know about Sunns, this
isn't the place though.
Link Removed is where the
real Sunn experts hang out!

A much lower traffic site, nowhere near as quick moving as TB, but friendlier and
substantially more knowledgeable Sunn info there.