Getting more from my Champ

[DaddyDom]

Hope this isn't too much of a dummy question but here goes.

I love my BF Champ. When I got it, it had a Kendrick 8" speaker fitted. Perfect for home and small gigs, I love the sound, it's plenty loud enough.

Sooo I was using our singer's SF Twin at practice until it blew a fuse so brought my Champ and - of course - really felt the size thing.
I've always loved 2 x 12"s (AC30 user from way back, now sold) but also love my amps with 1 x 12" (Harmony, Soldano) and even 1 x 10" (Selmer).

Luckily, I have a couple of old 12" cinema speakers in cool retro cabinets, containing Goodmans Audiom speakers and I think from memory, they're 15 ohms. So is there anyway I can match these up bearing in mind the ohms? What will happen? Would I need to alter the Champ even though I'd rather not?

I know there's often a bit of Champ-chat around here so hopefully someone can help out.
Many TIA

[46346]

your Champ wants to see a 4 ohm speaker.

once you verify that they are 15 or 16 ohms or so, you can wire the two cabinets in parallel, to bring them to a combined load of 8 ohms.

usually the classic Fender amps used robust output transformers that could tolerate the mismatch of 4 ohms to 8 ohms.
i have done this many times over the decades...

but the Champs have the smallest of the OT's, and i did read one account of a guy burning one out with the mismatch.

i have done it with my SF Vibro Champ - plugging in a single 12" cabinet at 8 ohms, and it does get more massive. i will record with it like that sometimes, but i mostly play it with the internal 4 ohm speaker for my living room, etc.

so if you get your wiring right, i think it's safe enough to try for a while, but if you end up having to crank it full-time to keep up for hours on end, you might be asking for trouble.

[crazyzeke]

Adding a bigger cab to an amp you like that doesn't have a big enough/powerful enough/efficient enough speaker is a good move, because then it's the tone you like, just more air being pushed to get the dB levels up.

I think what complicates it is making sure the impedance matches up perfectly regardless of how you're running it, as the original post noted. Tube amps I tend to treat as surprisingly fragile for stuff like that, and try to only use known good working tubes and speakers and never mismatch. With that in mind, I've never blown a speaker, fuse or transformer in any tube amp I've owned, usually it's just been a case of parts needing changing due to failure - Laney amps for example tend to have crappy quality pots that will crackle and not hold their value so the volume jumps around independently.

Not saying you can't mismatch impedance, I just personally wouldn't do it, output transformers aren't cheap and as it's high voltage circuit stuff (plate voltages of most Class A/B amps tends to be 350-450V and Class A amps like the Champ and AC30 are kicking 290V-310V) and unless you really know your electronics, that's a visit to a good tech, waiting in line to get it serviced etc and then after a major parts change they might test and find other components took the strain as the OT went down so you're talking more parts and labour costs. From my point of view totally not worth the risk when it's cheaper to just get speakers that do match and avoid those kinds of problems.

[øøøøøøø]

Plug it into a bigger 4 ohm speaker

You’ll have to wire up a speaker cable with an RCA jack unfortunately

[marqueemoon]

Plug it into a bigger 4 ohm speaker

You’ll have to wire up a speaker cable with an RCA jack unfortunately

Back when I had my 79 Vibro Champ I tried this with an 8 ohm 4x10 cab and to my surprise it really sounded like ass. I used this same cab with a Bassman which is also looking for an 4 ohm load and it sounded fine.

Could the impedance make that significant a difference?

I don’t own any of this gear anymore, so I guess it doesn’t matter.

[øøøøøøø]

Hard to say!

I’ve run a Moviola URS into a 4x12 and it sounded awesome

Maybe that amp just didn’t like that speaker in your case

One thing I’ll stress—the “can tolerate 0.5x mismatch” rule of thumb should only be assumed for Fenders with an “Ext Speaker” jack

Champs do not have that feature, and were likely not spec’d to have an OT that could take it (they were very cost-conscious amps, hence the RCA jack for speaker duties and the cheap On/Off switch that is not rated for the level of current it sees)

Given those cost-saving features it’s unlikely Leo/CBS would’ve sprung for an extra-burly OT

[DaddyDom]

Thanks for the replies.
So, logic seems to say, find a 4ohm 12" speaker?
Then I could use one of the cool, old cabinets with the right speaker if I liked the sound.

Thanks again, any further comments welcome!
DD

[hulakatt]

Don't plug it in to a bigger 4ohm speaker, plug it in to a better and more efficient 4 ohm speaker!

I may sound like a broken record but my first recommendation for Champ speakers is the Jupiter 8sc, I have 1 in each of my Champs and I love them! They are louder, much more full range and much higher quality than what most people are used to in an 8" speaker and esp in a Champ.

You can jack into other cabs with other speakers but I would 100% keep to matching up to 4ohms and look to more efficient speakers for more volume. If you want to really play around with other cabs and other impedances, you may want to consider swapping the OT to one with multiple ohm output windings but at that point, I'd be considering building a Champ from the ground up.

My dream Champ build is a VibroChamp head with a 15 watt, multiple ohm output windings OT on a matching 2x8 closed back cab (loaded with the Jupiters, yeah) for a mini piggyback Bandmaster/Champ setup.

[DaddyDom]

Thanks hulakatt, I was hoping you'd comment at some point.

I totally get that there are 8" speakers able to extend the Champ's abilities - and to be fair, the Kendrick should already be better than an Oxford.

Where I hesitate is in not knowing if a Jupiter would give me the feeling of more air moving like you'd get with a bigger cone. Or even if that's actually what I want to hear??
I could actually pick one up next time I travel overseas for a pretty reasonable price so you never know.
Do you know of any Jupiter/Champ sound-clips online?

TIA

[hulakatt]

I don't know of any clips but I haven't looked and I don't think clips would give much of an idea of the feeling of moving air anyway. I will say it's much closer to sounding and feeling like the full sized Fender amps I gave from the same era then before when it sounded and felt like a practice amp. Now it sounds and feels just likes it's bigger siblings, just quieter.

[crazyzeke]

So, logic seems to say, find a 4ohm 12" speaker?

Or be a bit more original and try a 4 ohm 2x10" cabinet. 10" speakers are super underrated for guitar tones especially when paired with tube circuits. I say this because an original vintage Vox AC10 Twin is one of the best amps I've ever used, and the few other times I've used 2x10" or 4x10" amps or cabinets it's been a similar kind of wow.



The one I tried belonged to a former friend of mine, a picked out of the trash and restored job (needed new tolex and logo and some TLC but wow, those little blueback 2x10" speakers sound glorious when cranked). The damn idiot later sold it for so much less than it was worth considering all the work that his father put in getting it looking original.