Super reverb 4 ohm speaker load.

[Hella1hella]

Hello everyone, I have a super reverb that is currently in head form. I want to put it into a combo and I know it is a 2 ohm speaker load but here is my question. If I get two 8ohm 10's, that would equal out to 4 ohms. Can I safely run my amp like this?Will there be any long term effects? I have talked to numerous people that say it is okay to run a Super reverb at 4 ohms, and even people who prefer it. I really am only wondering this because I do not want a 4x10 setup, and the choice of speakers that leaves me is pretty slim because I would need two 4 ohm 10's which pretty much leaves weber and only weber. What would be the consequence of running it at 4 ohms? Just less power?

Thanks!

[pdf64]

The 6L6 will be running a 8k p-p load in this condition. When I flip the impedance switch of my amp from 8 to 4 ohms on an 8 ohm speaker, the tone gets more 'harmonicy', less punchy (input quieted during switchover). Similar to flipping the pickup selector switch.
Also the 6L6 screen grids will dissipate more power when overdriven. This could be mitigated by reducing the screen voltage, either by increasing the screen grid resistors or putting a resistor in series with the choke, say 1k 5 watt.

[Hella1hella]

Sorry, I do not work on amps so I am not really sure what your response means. Any way you could dumb it down a little bit and more straight forward? Its hard finding speakers to use with this amp without using 4-10's, and is also not easy on the wallet. This is where my problem lies. Maybe I made the original post too complicated. I just need to know :
A: Can I safely run a 65' super reverb with two 8 ohm speakers, Without long term effects.
B: What will this do to the overall sound of the amp?
C: Should I just suck it up and buy two 4 ohm 10's from weber?

[pdf64]

A: Probably, though if you overdrive it, the tubes may degrade faster.
B: It will sound different, in a similar way that a guitar will sound different when changing from neck to bridge pickup.
C: A 2 ohm load would be a good idea. Alternatively, replace the output transformer to one suitable for a 4 ohm load; an output transformer would be cheaper than 2 speakers but require a higher degree of competence to fit (eg you could change the speakers yourself, but may need to pay a tech to swap the transformer).

[Hella1hella]

Yeah, I guess I will just have to suck it up and order the 4ohm speakers from Weber. Its an all original 65 Super Reverb so I do not really want to touch the transformers. Thanks for the help!

[pdf64]

Regards replacing the OT, an alternative view is that much of the value of the amp will be in it having working original transformers. By fitting a replacement (and so keeping the original safe), you will be protecting it, enabling it to be refitted when you sell it.
Bear in mind that with only 2 speakers, you'll be down 3dB so are likely to crank the amp harder to compensate, thereby putting more stress on the 43 year old layer of varnish which is all that's insulating your OT windings.
It would be a shame if you got the speakers and then damaged the original OT.
I assume that the speakers aren't original?

[Hella1hella]

There is actually no speakers at all. Someone put it in head form before me but I only paid $65so I could not pass it up ha ha. So even two 4 ohm would be worse than 4 8 ohm?

[pdf64]

'So even two 4 ohm would be worse than 4 8 ohm'
It depends how you are likely to use it / how hard you intend to drive it, so it's debatable, your choice really.
Personally, if you've already got 2 10" speakers you're happy with then I'd change the OT, as you may not like the Webers.
Whereas if you fancy trying out the Webers, then it makes sense to get the 4 ohm version.

[Hella1hella]

I guess I do not quiet understand. Two 4 ohm or 4 8 ohm equal out to 2ohms. So what is the difference? I mainly want 2x10 to save weight. I do not really want to change any original parts unless its caps or something that needs to be changed. Any good suggestion for 10" 4 ohm speakers if I go that route?

[MWJB]

Run it with 2x8ohm 10" speakers if you have them. Fender' Blues Deluxe runs a primary Z a little under 8K, old tweed 6L6 Fenders were 6-7K. It's doubtful that you would notice any accellerated deterioration of power tubes...unless you always run the amp harder because it's pushing a smaller sound wave & may be harder to hear on stage.

[g1]

I guess I do not quiet understand. Two 4 ohm or 4 8 ohm equal out to 2ohms. So what is the difference?

I think what pdf64 was getting at with the 3db reference was that 4 speakers will sound louder than 2 speakers even if the total impedance is the same (you are moving more air). So if you end up turning the amp up to compensate, then you are working it harder.
For myself, I would agree with MWJB, the OT shouldn't have a problem running into a 4 ohm load. But now there are 2 places you are losing loudness, one is due to the impedance mismatch (you won't get as much power into 4 ohms as 2 ohms), the second is that you are moving less air (2 speakers rather than 4).
You only paid $65 and the original cab. is no longer original. Try it with the 2 speakers you have.

[Hella1hella]

Alright awesome. I actually do not have any speakers yet. I need to order them I just wanted to do some research prior. I DO have a weber signature 10 that I just used for messing around that is 8 ohm, and I am ordering a JD NEWELL 2x10 cab. Would it be okay if I ordered a higher end weber 4 ohm and used it with the 8 ohm creating a weird 2.67 ohm load? I dont see why not but I am no professional and am so scared to do anything because I do not want to mess this amp up haha. I will eventually buy another higher end weber 4 ohm to go with the other one I just dont have all that cash right now so saving $100 for a while until I can replenish my spending stash would help greatly. I really like the weber stuff, I have them in some of my other amps.

[olddawg]

How loud do you plan to crank it up? You can always parallel up a couple of ceramic 8 ohm 20 watt resistors (they're cheap) with the two 8 ohm speakers to better match the load. Might even be a good idea if you are trying to hit the sweet spot at a slightly lower volume. A lot of this is splitting hairs IMHO. Generally you can run a 4 ohm load on a 2 ohm tap just like you can run an 8 on a 4 or a 16 on an 8.

[Hella1hella]

I will probably play at very loudest around 8. I just played live with a band with no mic at 5. Can you really just put some resistors inline with the speakers to create what ohms you want? I have heard of this before but like I mentioned earlier, I do not know too much about technical stuff. I can solder and what not and mod pedals quite a bit but nothing serious. What about what I said earlier combining a 8 and 4 ohm speakers resulting in like 2.67ohms?

[olddawg]

I will probably play at very loudest around 8. I just played live with a band with no mic at 5. Can you really just put some resistors inline with the speakers to create what ohms you want? I have heard of this before but like I mentioned earlier, I do not know too much about technical stuff. I can solder and what not and mod pedals quite a bit but nothing serious. What about what I said earlier combining a 8 and 4 ohm speakers resulting in like 2.67ohms?

Yeah you can do it. You have two 8 ohm speakers, right? Purist will say the resistors aren't an inductive load but you have speakers there also. Just wire it up like you would four 8 ohm speakers except substitute the 8 ohm 20 watt resistors for 2 of the speakers. I would parallel a resistor with each speaker and then parallel those 2. Personally, I wouldn't bother. I would just use the 4 ohm cab.