I'm looking for a speaker to replace the C90 Black Shadow speaker in an older open-back Mesa Widebody 1x12 Cab. I like the speaker running wide open but less so at medium and lower volumes as it seems a bit dark and lacking in dynamics.
Usage is entirely home but I can still exercise some tubes -- just not cranked where I feel the C90 shines. I have no plans for playing in a band setting so there are no concerns with fitting into or rising above a mix. I play a wide spectrum of rock but don't venture into into high-gain djenty territory. I live in the crunch. Current pairing is with an Egnater Rebel 30 but I'm really planning ahead for a Marshall Origin 20 on order.
I like the ET-65 in video and on paper, but I'm concerned the larger geometry of the cab may have an adverse effect on the bottom end and other frequency ranges through the lower half of the master volume.
Any advice is greatly appreciated.
Hummm ... yes, my first impression is to suggest the ET65.
But ... your key statement about the Mesa C90 is "at medium and lower volumes as it seems a bit dark and lacking in dynamics."
That is a common problem with speakers in that power range when they are not being pushed! Sooo...
Since you are not using high power amps I'd go with a Green Beret ... especially with that Marshall- a match made in heaven! I heard those amps at NAMM and they are flat out the best classic sounding Marshall amps this side of a vintage JTM45. The Rebel by comparison is stiff and lifeless!
I agree those amps sound vintagey gorgeous. I'd swap out some of the Chinese tubes for a smoother high end and better dynamic articulation, especially with a brighter speaker like the GB. I always suggest the dynamic long plate JJ ECC803S for the V3 PI slot and at least one smooth sounding ECC83MG for either of the other slots. I might also try the JJ 6CA7 beam power tubes for bigger/deeper/cleaner bass and sweeter high end sparkle (like KT66 with EL34 midrange) if changing bias components isn't necessary. It may not be required with a cathode-biased amp, but Vaughn should know.
I'm a big fan of JJ too ... unlike other manufacturers, they have REALLY brought back better sounding tubes to the world ... and some actual advancements to 50-70 year old designs, too ... very cool!
However, unless a tube is actually faulty in some way (microphonic, noisey/hissy, etc) tube changes generally only slightly re-voice an amp ... where speaker changes turn it into a whole new amp!
Absolutely Vaughn. A different speaker will have a bigger effect on tonal character, and will even effect amp compression. My tube recommendations will mainly fine-tune the harmonic structure in way the tubes overdrive into each other for an overall deeper and less-grainy/fizzy overdrive with a dynamic response--the long plate tube in the PI slot probably having the biggest effect. On that, the long plate Sovtek 12ax7LPS is also a popular PI tube with a softer/more-compressed response than the JJ. It may be worth trying both.
I'd ask on the Marshall forums, but my understanding is a cathode-biased amp can accept different power tubes without any rebiasing, although the OT impedance and possibly the tube jack wiring need be considered concerning type. Either way, I'd stick with EL34 types with this amp. The JJ 6CA7 should reduce fizz and deepen the mid push compared to the stock Chinese EL34, but you may like the compression and upper-harmonic character of the stock tubes just fine. The JJ KT77 is a cleaner/more-open/brighter, but sweet/big/tight sounding tube that might be better with a darker speaker like the Invader 50, unless you prefer lots of sparkle. They do have a more open high end, but not at all harsh and get nice and "creamy" when driven. Popular for NuMetal styles. Not typically vintage Pexi. The Ruby EL34 BHT should have a deepening effect, while retaining the pentode-type stronger 3rd harmonics and "swirl"--being a modern replacement for the coveted EL34 =C= with perhaps a sharper upper-mid quality possibly accentuated by the strong 3~3.7kHz peak of the WGS GB speaker. The JJ EL34II may be a bit sweeter, and with a big 6L6GC bass response, essentially like a more resonant 6CA7 with stronger 3rd harmonics and swirl. AFAIK, not as bright as the Shuguang or Tung Sol EL34B. The standard JJ EL34 is a "neutral" sounding pentode that might be just great with the GB speaker. Should be milkshake thick when driven in the Origin 20. The Mullard EL34 RI is reportedly quite warm and smooth with deep bass. Maybe a bit "dull" in a cathode-biased amp, and I'm not sure about the long term reliability of Russian tubes. The JJ's or EL34 BHT should last longer. Those are the affordable power tubes I'd consider for the amp, but someone with direct experience might have more insight. I'll leave off at that.