Pushing a 12" 25W speaker with a 5W Champ

[Steverino]

Is this practical? What can I expect from a configuration like this? It seems most 12 inch speakers are a minimun of 25W. It's a little late if it's a bad idea, as I've already ordered a cab for my diy VibroChamp to take a 12 incher.

Any recomendations? Jensen? Weber?

First post, btw, nice place!!

:wave:

[bob p]

Champs work fine with higher powered speakers. People use little amps with big cabinets all of the time. Just don't expect the little amp to push the speakers far enough to get speaker distortion.

[DirtyGeorge]

No problem. I have run my EL34 SE (less than 10w) into an 80w Celestion with excellent results. A larger speaker makes these little amps sound much bigger with more bottom end.

I have no experience with the new Jensens so I won't comment on them. I did put a couple of Weber Blue Pups (10 in. alnico) in 30w EL34 combo. They have been in there about 3 years and I could not be happier with their tone.

Weber has 12s rated at 15w. I am partial to alnico magnets for the power compression (although they cost more). But with only 5w to drive it a ceramic would make more sense.

[bob p]

I have one of the little 8-inch Weber Signature Series ceramic speakers in my SF Vibrochamp. although it seems to enjoy a favorable reputation in champ applications, I have to admit that I absolutely HATE the speaker. I bought it as a replacement for the original speaker when it blew and it just doesn't compare. After 3 years or so its still shrill and harsh sounding. Admittedly, there aren't a lot of good choices for 8 inch speakers, so I've left the baffle intact an whenever I can, I run the champ out into an external 2x12 4 ohm cabinet. the moral of the story is this: don't use an inexpensive speaker just because the amp is a champ. A good speaker still makes all the difference.

[Steverino]

I've been to the Weber site and the 10A100 alnico 15 watt looks like the way to go.

This is my first attempt at building an amp, so I'm pretty stoked. Thanks for the replies!

[stokes]

I used the Weber 10F150 ceramic,25watt in a Champ like clone with a KT66 and a heftier pair of trannies,I was going for a little extra headroom,and it is one of the best sounding speakers,he makes some great stuff.I had a Kendrick Blackframe,and a Celestion Vintage 10 in it and the Weber blew them both away.To me the Champ circuit breaks up enough,so I wanted a speaker that didnt break up so early.If you email Ted and tell him what you are looking to do soundwise he will give you great advice.I ordered three different speakers at different times and each time I described what I was trying to get and he was dead on with his recomendation.He is the best.

[Steverino]

Ordered the 12A100T Saturday. The cab is in the process of completion. The chassis is complete and I've cooked it for a few hours with no meltdowns.

[Mark Hammer]

The wattage rating of the speaker essentially describes how much heat it can successfully dissipate before the voice coil goes pfffft.

*Part* of that spec stems from the gauge of wire used for the voice coil, and aspects of the voice-coil structure that permit heat to be successfully and safely siphoned off despite lots of current moving through the coil and lots of movement (every time the coil moves foreard or backward, there is the risk of friction-related heat buildup).

Other parts of that spec stem from the physical parameters of the cone itself. So, if the cone is designed to be able to move a lot of air and push it far (i.e., big cone excursion), then the cone does have to be thick enough to remain stiff despite its large area, and the surround has to be rigid enough that it has little risk of moving too far forward or backward i response to big transients.

So, in the grand scheme of things, your gut feeling about high wattage ratings "needing" more power is sort of correct. If the speaker is made to be able to take higher wattages, it will generally have the characteristics that require a little more power to get the cone moving properly.

There is moving, though, and there is moving. There is absolutely no risk incurred from using a higher rated speaker in a lower wattage amp. One need look no farther than the Z-Vex nano-amp which is a half watt or so and is intended to driver a 4x12 cab. The larger question is whether the amount of power the amp can deliver is sufficient to move the speaker into its linear range. That is, the zone where the speaker is at "cruising speed" and can display its full bandwidth with as little corruption of the tone as possible. Added to this is the question of whether the qualities a given speaker is known and appreciated for are obtainable at the levels the amp can provide.

It's not just breakup. For instance, if a speaker is known for "bell-like highs" or some other hyperbole, then the bigger question is whether the output levels from the amp that are sufficient to achieve that full frequency response from the speaker are still clean at the amp's output. If you tried to drive a 4x12 cab with the headphone output of a $40 MP3 player, you'd certainly hear it, but the output level needed from the player to do that would probably exceed the point where the player is delivering "clean" output from its measly pair of AAA batteries. At the same time, that wattage fed to the speakers (we'll say 100mw for argument's sake) would be unlikely to move the speakers into their linear range.

But all of this is really academic. Pumping a watt or two from a Champ will not exceed the amp's ability to be clean, and will be more than enough to move a single 12" speaker or reasonable power rating into its linear range. If we were talking about a 2W bass headphone amp trying to power a 300W rated 18" speaker, that would be one thing. But the capacity of the Champ and the rating of the speaker you have are not that far apart as to be considered mismatched.

[Regis]

I just rebuilt an old Voice of Music Hi Fi amp into a variation of a 5F1 Champ, and it positively scorches through a JBL D130 and an Eminence Private Jack I have. Now, this amp has no negative feedback and is optimized for overdrive, but I'm telling you it sounds great through those speakers.

[RickyD]

If you like the tone of a particular speaker and have heard it played at a loudness close to the loudness you will be using, you should expect the tone to be good with your amp. Don't worry about the high power rating causing a problem wth a lower powered amp. Speakers with high power ratings do not have to be played extremely loud to sound good. I submit that the speaker is affected only by the voltage applied to it; and if it sounds good at a given low volume with one amp, it should sound good at that volume driven by a different amp.

Average power of 0.1 watt (100mw) is in the neighborhood of home practice volume, difficult to talk over. I've never heard a good speaker sound bad at that volume level.

Of course, I would like to extend all due respect to Mark Hammer and others who feel otherwise. I know what I can and cannot hear, I would not presume to tell others what they can and cannot hear. 40 years of playing may have attenuated my personal frequency response a bit... These are personal preference issues.

[Ray Ivers]

Bob,

If you get the chance, you might want to try out an Eminence Beta 8. I'm using one in my living-room practice amp, and it really sounds pretty good for an 8" speaker; good bottom end, fairly flat mids, and no excessive highs. It's only available in 8 or 16 ohms, though.

Ray

[oahu]

don't worry...

hello.

i have an old super-reverb amp, which has 4 x 10'' speakers rated at 15 watt each, which is, oh well, 60 watts...

the amp is about 40 watts (+/- 20%) it sounds great, when played at a lower volume up to some point... then its just fine.

but if i turn up the volume just a little bit louder, it sounds like s*** .

i also repaired a champ from the late 70's, using a new 8'' jensen ceramic speaker, rated at 15 watts, the amp is 5 -7 watts and at a certain volume, it sounds s*** too.

but when i plugged it into a single 12'' celestion speaker cabinet, rated at 30 watts, it was just great...

so i think, it's nice to have some headroom, especially, if you're gonna turn the amp up loud. but it depends on which sound you have in mind.

ps: just try to power your home-stereo-system-speakers, rated at 200 watts each, with a hi-fi tube amp rated at 2 x 10 watts. sounds great! but don't use your marshall 50-watt top for that!!! it just blows the speakers...

[drlowlow]

weber alnico blue pup 8s

I just replaced the 8 ohm jenson ceramic 8 inch in my sf vibrochamp with a weber blue pup 8 alnico and I am satisfied with it. Of course I haven't had the amp plugged into anything else in a long time so comparing it is difficult but for the price (I thought I would be disapointed) I was pleasantly surprised. I think part of it might be that the jenson was the wrong impedance but the frequency response is much better. might want to check them out. just my 2c.

[Jammin'John]

Ordered the 12A100T Saturday. The cab is in the process of completion. The chassis is complete and I've cooked it for a few hours with no meltdowns.

I hope you like brite speakers with no bottom 'cause that's what you ordered.
It will be LOUD if that's any consolation.
You might be ok if you play humbucker guitars.


JJ

[Jammin'John]

Champ

I have one of the little 8-inch Weber Signature Series ceramic speakers in my SF Vibrochamp. although it seems to enjoy a favorable reputation in champ applications, I have to admit that I absolutely HATE the speaker. I bought it as a replacement for the original speaker when it blew and it just doesn't compare. After 3 years or so its still shrill and harsh sounding. Admittedly, there aren't a lot of good choices for 8 inch speakers, so I've left the baffle intact an whenever I can, I run the champ out into an external 2x12 4 ohm cabinet. the moral of the story is this: don't use an inexpensive speaker just because the amp is a champ. A good speaker still makes all the difference.

I have a Weber 8" Blue Pup in my tweed champ that works great !


JJ