I'm having a hard time finding any 300B-friendly speakers I’d actually want, outside of the Klipsch Heritage line or something horn-based. Is it even possible to design a conventional TMW speaker that hits hard in the bass and still plays well with a 300B SET? I need an 8-ohm load since the amp I’m looking to use only has an 8-ohm tap, and as most of us know, SET amps don’t like lower impedances. Also, contrary to popular belief, a lower impedance speaker isn’t really more sensitive when used with tubes—they don’t "double down" on power like solid-state.
I’ve been eyeing the AE TD18+, Bliesma 74B or 74S dome mid, and Viawave ribbon—all 8-ohm and around 98dB sensitivity. The Viawave actually measures about 3dB hotter than the spec sheet says. But then I remembered: baffle step loss is going to kill that sensitivity unless compensated carefully.
The TD15X is a more realistic option, but it's only rated at 94.8dB (1W/1m). Still, I was intrigued by Zaph’s SB12.3 design—he got around 91–92dB anechoic with a 90dB SB34NRX75-6. So now I’m wondering… could a TD15X be part of a design that hits 97–98dB in-room?
Something ATC SCM100-inspired (sealed or ported box, dome mid, wide directivity) would be ideal—just done with higher-efficiency components and optimized for use with low-power SETs. Given how many 300B amps are out there, I’m honestly surprised there aren’t more high-efficiency, no-horns TMW speakers using top-tier drivers. Is this just a pipe dream?
I’ve been eyeing the AE TD18+, Bliesma 74B or 74S dome mid, and Viawave ribbon—all 8-ohm and around 98dB sensitivity. The Viawave actually measures about 3dB hotter than the spec sheet says. But then I remembered: baffle step loss is going to kill that sensitivity unless compensated carefully.
The TD15X is a more realistic option, but it's only rated at 94.8dB (1W/1m). Still, I was intrigued by Zaph’s SB12.3 design—he got around 91–92dB anechoic with a 90dB SB34NRX75-6. So now I’m wondering… could a TD15X be part of a design that hits 97–98dB in-room?
Something ATC SCM100-inspired (sealed or ported box, dome mid, wide directivity) would be ideal—just done with higher-efficiency components and optimized for use with low-power SETs. Given how many 300B amps are out there, I’m honestly surprised there aren’t more high-efficiency, no-horns TMW speakers using top-tier drivers. Is this just a pipe dream?
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An 18" woofer to dome mid transition isn't the easiest thing to do. The Bliesma M74B-6 looks like it starts a gradual roll-off at 1kHz. If you want to use it below there, you'll probably lose some sensitivity.
How much the 18" beams at the cross point is an open question, as is the range where breakup starts seriously. I didn't see response data on their site.
Using speakers against or close to the wall is another option to gain some apparent sensitivity. That often comes with some loss of soundstage depth, but that might not matter to you.
High sensitivity woofers that go low typically require very large enclosures. Those are out of favor these days, especially since cheap DSP, high power amplifiers, and high excursion woofers are so prevalent now.
Tradeoffs like these might be acceptable for your particular use case. When trying to make a mass-market product, it gets harder to compromise, especially if the driver cost is very high.
How much the 18" beams at the cross point is an open question, as is the range where breakup starts seriously. I didn't see response data on their site.
Using speakers against or close to the wall is another option to gain some apparent sensitivity. That often comes with some loss of soundstage depth, but that might not matter to you.
High sensitivity woofers that go low typically require very large enclosures. Those are out of favor these days, especially since cheap DSP, high power amplifiers, and high excursion woofers are so prevalent now.
Tradeoffs like these might be acceptable for your particular use case. When trying to make a mass-market product, it gets harder to compromise, especially if the driver cost is very high.
I had originally thought the natural roll-off of the Bliesma M74SA-6 could support a crossover around 500–600 Hz, but I may have been mistaken. Still, even if a true 300B-friendly speaker without resorting to horns isn’t feasible, the concept remains very compelling for lower-wattage push-pull tube amps—which many tube designs are. A 92–94dB sensitive TMW based around an AE TD15 could be a great match for 20–45W tube amplifiers.
you want wide dispersion mid with a ribbon up top?
Rather look at combining the M74's with the T25/T34's.
If wide directivity is a high priority the A versions *unique' shape gives you that to a larger degree then the others.
The T34A has high sensitivty, output capability, and a wider dispersion then many 1" domes fx.
But creates a short useable range for the M74 and a longer CTC distance.
If you are sensible about the low end extension, and willing to incorporate subs for the lower range then absolutely yes.
Take advantage of a well shaped and dimensioned baffle.
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Those 15”/18” woofers have high sensitivities but still need current to shine. I suggest using the 300b for the midrange and tweeter only, and leave the woofer to a solid state amp, or if you must, a push pull pentode amp.
The OSMC developed on this forum is said to sound good with the 8W (solid state) ACA, but a 300b SE will lack in the low end.
The OSMC developed on this forum is said to sound good with the 8W (solid state) ACA, but a 300b SE will lack in the low end.
Sorry, I was being lazy and didn't look at all of them. That one seems to have flatter frequency response overall, so probably a little easier to use if you want a simpler and lower crossover.
This page has distortion data for a few of their mid domes. Distortion typically increases below 1 kHz, but that might be an acceptable trade-off for your use case.
https://hificompass.com/en/reviews/bliesma-m74a-6-m74b-6-m74p-6-and-m74s-6
I'm not trying to discourage you from pursuing a design like this, just bringing up some things to keep an eye on and ideas about why you don't see a lot of commercial designs like this.
I've developed a strong desire to hear a 300B amplifier firsthand—there’s something captivating about the legend surrounding this valve. That, along with the lasting impression left by the Marantz Model 9s, has really fueled my interest.
To make this happen, I’ve been looking into the Klipsch Heritage line, but I’m hesitant to fully commit to horns. I’m not entirely convinced they can match the finesse and fidelity of a top-tier beryllium or silk dome midrange, or deliver highs on par with the best domes or ribbons. A proper dealer listening session is definitely in order before I can draw any solid conclusions.
Still, I think the concept I’ve been exploring has real potential—just perhaps not for a 300B setup. A well-executed speaker with 94dB sensitivity would be a great match for a 20–40W push-pull triode amp. As for higher-powered DHTs like the 845, that’s a path I won’t be taking—I’m not interested in wrangling with 900 volts on the plates.
To make this happen, I’ve been looking into the Klipsch Heritage line, but I’m hesitant to fully commit to horns. I’m not entirely convinced they can match the finesse and fidelity of a top-tier beryllium or silk dome midrange, or deliver highs on par with the best domes or ribbons. A proper dealer listening session is definitely in order before I can draw any solid conclusions.
Still, I think the concept I’ve been exploring has real potential—just perhaps not for a 300B setup. A well-executed speaker with 94dB sensitivity would be a great match for a 20–40W push-pull triode amp. As for higher-powered DHTs like the 845, that’s a path I won’t be taking—I’m not interested in wrangling with 900 volts on the plates.