Ohms mismatch or swap output trans

[Mypalmurph]

Hello folks! I wanted to first thank everyone who commented on my previous post before I asked another question of the group. So thankyou!  Alright-I have a 1973 bassman 10 chassis I’ve recapped and straightened out.  It has an 8ohm output transformer stamped 021848 that looks sort of smallish but I believe to be original.  The original combo cabinet had 4-10” speakers at 32ohms each so the trans would see 8ohms.  I was lucky enough to grab a 1974 combo cabinet in decent shape and also 4-16ohm eminence speakers from a mid 70’s Earth Sound Research 6x10 cabinet.  I could probably get away with simply enduring an impedance mismatch although I have read some ominous warnings about voltage flyback and such but I happened to have a couple of options at my disposal.  I have an output transformer stamped 91032099 from a blues Deville 40watt whatever  It has a 4ohm tap and looks nearly identical to the trans mounted to the bassman infact if you told me it was a replacement I’d believe you- same footprint and bell caps the old one being rounded and the near ones square. So it’s a little bit of a hassle to swap transformers but squarely in my comfort zone to do so I am just wondering if anyone has similar experience?  Am I gonna miss those 10watts- is my tone gonna be ruined?  Should I even bother swapping transformers?  Is there another option aside from $500worth of 32ohm speakers? I’ll include a picture of the two transformers - tell me what you think.

[AlNewman]

eature=shared

Should work?
You need to do a bit of legwork to figure it out. 

[Mypalmurph]

I love uncle Doug!  I will go through this and take my measurements- didn’t know how to do it- I will update my posting to reflect my findings!

[HotBluePlates]

... I have a 1973 bassman 10 chassis ...  It has an 8ohm output transformer ...  I was lucky enough to grab ... 4-16ohm eminence speakers ...  I have an output transformer ... from a blues Deville 40watt whatever  It has a 4ohm tap ...  Should I even bother swapping transformers? ...

Do the transformer swap to use your in-hand Eminence speakers for a 4Ω total load.

Or buy one (8Ω) or two (16Ω, to wire in-parallel for 8Ω total) speakers with a total power-handling of 50-100w.  There are plenty out there, depending on which way you want to push the sound of the amp.

... Is there another option aside from $500worth of 32ohm speakers? ...

It would be silly to pay much for the original 32Ω speakers, because basically nobody wants or needs them (except the rare Bassman 10 owner).  You may see listings asking for a lot, but take note of how long the item has sat unsold.  You don't necessarily have to pay asking price.

[pdf64]

I suggest to wire the 4 x 16 ohm speakers in series parallel like a regular 4x12 cab, total impedance will be 16 ohms.
That will double the reflected load on the output valves, from probably about 4k to about 8k with the original bassman OT.
That’ll reduce the audio max power output a fraction, decrease anode dissipation a bit under load, increase the output stage gain a fraction, and increase screen grid dissipation a bit when being overdriven.
None of the above should generally be a problem.
FYI Marshall JTM45 typically use an 8k OT with 6L6 family valves, so there’s plenty of precedent for this.

I guess people may say the tone changes a bit, but it’s kinda tricky to do an instant AB comparison or to establish what to compare it to.

Whatever, it’s a completely free thing to try, so I don't see why not to