DF theory question

[loudthud]

I should have mentioned that the 4x6550 bass amp in post #6 has a "Resonance" control. This acts as a bass boost, and when boosting the bass, it lowers the damping factor. One thing that controls flab is using two speaker cabinets with different resonant frequencies in parallel. I posted a plot of the load impedance of my bass rig somewhere, I'll see if I can find it.

Edit: Found it ! Post #9 in this thread: https://music-electronics-forum.com/...-design/35273-

[Helmholtz]

I found in any amp the lack of global nfb makes sound more dynamical, more open.

That's probably not due to NFB per se, but rather caused by the different DFs.

Low DF not only emphasizes the speaker's bass resonance but also speaker treble response.

[tedmich]

Some in the tube audiophile crowd claims open baffled speakers can (best) play reasonable bass with a DF less than 1, seriously.

Maybe this is worth a try, but a speaker which can do 30Hz in an open baffle design is quite rare, maybe the so called infinite baffle subs at PE would be worth a try? You'd need mids and high from elsewhere, so you're in for a crossover and multiple drivers in the simplest approximation.

[J M Fahey]

Given the dropping response in almost all cabinets except HUGE or very inefficient ones, any boost in that weak area is welcome, even if a hump or two, "better than nothing".

FWIW all my Bass amps have damping=1
It helps, Musicians like it.

Is it "realistic"?

Compared to what?, 99% Bass instruments are acoustically mute, just a string and a pickup floating in an empty Universe

[The Dude]

Well, it's triode mode.

I am aware of that. I asked because I wondered if triode mode was the intent.

[Helmholtz]

I am aware of that. I asked because I wondered if triode mode was the intent.

I expected triode mode because it gives a much lower output impedance than pentode/tetrode mode without global NFB.
Also 100W with 4xKT88 points to triode mode.

[tedmich]

The interesting GRS 12SW-4 driver is back in stock at PE, its up to $35 but reportedly works well in infinite/open baffle. It should do close to 35Hz