8 ohm speaker in a BF Vibrolux Reverb

Tom Wolverton · From: Carpinteria, CA

I friend of mine wants to change his ‘65 Vibrolux Reverb from two 10’s into a single 12” speaker (different cabinet & baffle). Can he run an 8-ohm speaker? I think the Vibrolux Reverb wants to see 4-ohms ideally. Would 8-ohms hurt it?
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Brett Lanier · From: Madison, TN

8 ohms is fine, and if he’s going from 2 Jensens to one 8ohm JBL, Altec, Black Widow (high efficiency speaker) - he probably wouldn’t notice any less output in volume. Also gives him the option of plugging in an additional 8 ohm cab.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

In general, blackface/silverface Fenders can run a moderately mismatched load (e.g., 8 or 2 Ohms for a nominal 4 Ohm setup) if not pushed too hard. But given the choice of running a vintage blackface Vibrolux Reverb into 4 Ohms vs 8 Ohms, I'd run it at 4 Ohms. Transformer is not real stout. I have two Vibroluxes, one '66 blackface, one '71 silverface. The '71 transformer is significantly more stout than the '66, and that'd be my biggest issue with running the blackface mismatched. Anyway - with an amp like a Vibrolux for pedal steel with a high-efficiency speaker, I'd probably be inclined to push it pretty hard in a loud situation, and I think that's where I wouldn't be comfortable running a smaller load (higher impedance).

If I wasn't pushing it, I wouldn't think twice about running a mismatched load. I mostly use them for guitar, but sometimes for E9 pedal steel - but I generally just use the stock speakers (2x8-Ohm 10" speakers = 4 Ohms). They sound fine for steel if not pushed hard, but they break up early if pushed. But sometimes I will set it atop a 12 or 15" external cab with a JBL, EVM, or Telonics Neo. That does extend the range significantly.

As Brett says - if you wanna run with an 8 Ohm internal speaker(s) plus 8 Ohm external speaker, that IMO is the ideal situation for pedal steel. Set up that way, Vibroluxes can have a surprisingly large amount of headroom.

Tom Wolverton · From: Carpinteria, CA

Thanks everybody.
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Dave Grafe · From: Hudson River Valley NY

If it's an original 1965 amp it would be foolish to take the risk. It will work fine at half its design impedance until it doesn't. As the Vibrolux is a relatively low-powered amp for PSG and likely to be pushed hard in a band situation that is bound to happen sooner than later. Also bear in mind that an impedance change on the secondary affects the impedance on the primary, i.e. the tube plates, rendering carefully chosen bias settings totally irrelevant. Better - and far cheaper - to spend a few hundred bucks on a RI amp to mess around with, and leave the vintage gear intact.

Thus says another grumpy old man who's seen a thing or two.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

You didn't mention the amp's originality/condition, but I meant to mention this. With the median price of an original '65 Vibrolux Reverb in excellent cosmetic shape running in the $4000-5000 range or more for a really clean original example, I think it would not be a good idea to modify the amp in any manner that could not be put back exactly to original condition.

It is not difficult to completely remove the baffle of a blackface Fender with the original speakers and all wiring (including the cable to the amp's RCA jack) completely intact. Then one can replace the whole shebang with an entirely new baffle, speaker, and wiring, allowing the amp to be put back completely stock if desired. And any other approach will be detectable, and will degrade the value of the amp. Done poorly, the amount of value degradation can be large. People paying this kind of money for an old Vibrolux Reverb want 'em clean and original, period.

If the amp has already been modified in any significant way, this is not so much of a consideration.

To pick up on what Dave G. is saying - definitely, it is sub-optimal to run a Vibrolux Reverb at anything but 4 Ohms. There is an issue of some loss of power through impedance mismatch. But IMO, the main issue is excess flyback voltage, which can not only change the sound but also damage the output transformer, especially if pushed hard. Without original transformers, a $4000-5000 VR is probably worth around half of that.

Tom Wolverton · From: Carpinteria, CA

Dave M. You said “ sub-optimal to run a Vibrolux Reverb at anything but 8 Ohms. ”

Did you mean to say 4 ohms?

Also note: my friend is running guitar, not steel thru this amp. But I think he should leave it 100% original.
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Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

Absolutely - typing too fast. 4 Ohms, not 8 Ohms. Edited to correct.

For guitar, I can't imagine changing the general speaker configuration of a Vibrolux Reverb in the slightest. IMO, the finest Tele amp on planet Earth, and great for pretty much anything. My '66 came with two original Jensen '65 C10Qs, one blown. I found another '65 C10Q, pulled them both, and put in two excellent Kendrick (Gerald Weber) replacements for daily use to make sure the '65 C12Qs didn't get blown. I've had the amp around 30 years and have used it extensively. I doubt those Jensens would have survived, and they're in a box in case I ever sell it (unlikely).

George Biner · From: Los Angeles, CA

Also, I would think the amp would sound completely different with a 8 ohm load vs. 4.
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Colin Boutilier · From: Nova Scotia, Canada

I bought a Weber Z-Matcher for my mad scientist projects, and it was money well spent. I can run whatever, with whatever and not worry about it. It was really a necessity for me, as I had picked up a '75 Super Reverb head conversion and had to contend with that 2-ohm OT.
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Jeffrey Maxwell · From: Amarillo, Texas, USA

How about a 4 ohm 12" Speaker

Tony Prior · From: Charlotte NC

The OHMS will have nothing to do with "SOUND" , thats based on speaker voicing. As we all know some speakers are voiced for a higher end brighter tone while others the opposite. If we change from 4 to 8 ohms and don't like the "TONE" it ain't the ohms !

Case in point, when I was gigging with a NV 112, I could not bond with the tone, too much mid range. I pulled the 4 ohm stock speaker and replaced it with a 50 watt rated Fender Eminence 8 ohm 12, the one with the gold/brown label. It was just what the Dr ordered. And yes of course many told me I was gonna blow up the amp due to the ohm miss match. I used that amp on a show, 2x month for over 2 years. Guess what, it didn't blow or get hot, but the MID RANGE HONK was gone ! AND I didn't notice any decrease in output either.

PS- I use those Fender Emmy speakers in all of my amps, it keeps the amps consistent.

When changing speakers, the voicing of the speaker matters.
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Tom Wolverton · From: Carpinteria, CA

You all will be happy to hear that my friend decided to leave his BF Vibrolux Reverb alone. Thanks so much for the info. He read it all and scrapped his plans to modify.
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