Fender Twin Reverb BF Reissue - Impedance Curve With Two 8 Ohm Reactive Loads

[Greenback25]

I recently wanted to use a Fender Twin Reverb blackface reissue for reamping purposes and with reactive loads, but I soon noticed that it only has 4 ohm speaker outs whereas the two reactive loads that I use (Suhr Reactive Load / St. Rock React:IR) are both rated at 8 ohm.

Knowing that the Twin Reverb has a main and extra speaker output, I was thinking about connecting both loads to the Twin simultaneously, so that two 8 ohm reactive loads in parallel represent a total load of 4 ohm for the amp, whcih would be ideal.

Is it safe to run the amp this way? What would the impedance curve look like? I assume it'll be a composite between a 25W Greenback 4x12 cab (Suhr) and a Mesa V30 4x12 (St. Rock), but maybe the impedance curve is only dictated by the load on the main speaker out?

I already tried running the amp with only one reactive load connected to the 4 ohm main speaker out, but I didn't like the congested top end that way and the amp seems to break up a bit earlier as well, which I also don't particularly like.

It just sucks that these reactive loads don't have an impedance switch and that the Twin Reverb only has 4 ohm outs...

[pdf64]

The output sockets on the amp's back panel should be wired in parallel, so electrically they're identical (apart from the shorting contacts on the main socket).
So your idea should be fine.
Running it with an 8 ohm load will change the amp's characteristics a bit, so your description of the change in response seems to be expected.
A Twin Reverb might seem to have a boomy bass response when a 4x12 type load, due to that cab type having a big impedance spike at bass resonance, typically around 100-120Hz.
The parallel combination of different 4x12 cab models might even that out a bit.

[Roe]

yes 4x12s tend to peak around 115hz, which may be overkill. but try to lower the bass, esp. at higher volumes

[Stevem]

These types of Fender tone circuits have excessive bottom so that at low volumes ( 3 or less ) they can sound full.

At high volume levels ( 5 or better) the bass needs to rolled off a ton which will give more head room , less clipping and better definition.

I went so far when I was playing thru a twin all the time and at wildly different volume levels to lower down the bass side of my neck pick up when playing a gig at the loud end of what I used the amp for.
3 seconds with a screwdriver before the start of the gig is all it takes.

I preferred this to changing out the PI out coupling caps to .022 uf, at least for my purposes.

[B Ingram]

I recently wanted to use a Fender Twin Reverb blackface reissue for reamping purposes and with reactive loads, but I soon noticed that it only has 4 ohm speaker outs whereas the two reactive loads that I use (Suhr Reactive Load / St. Rock React:IR) are both rated at 8 ohm.

Pull 1 output tube from each side of the bank of 4, and use one of your 8Ω reactive loads.

[Roe]

I recently wanted to use a Fender Twin Reverb blackface reissue for reamping purposes and with reactive loads, but I soon noticed that it only has 4 ohm speaker outs whereas the two reactive loads that I use (Suhr Reactive Load / St. Rock React:IR) are both rated at 8 ohm.

Pull 1 output tube from each side of the bank of 4, and use one of your 8Ω reactive loads.

4 tubes sound better normally

[B Ingram]

4 tubes sound better normally

I agree that an unmolested Twin Reverb sounds better normally.

But dude has an 8Ω reactive load, and a 4Ω Twin. If he wants to play, today, he can just yank 2 output tubes and have an "8Ω output Twin."

Not the same, but it is what it is.