12" speaker for Vibro Champ Build? Help please.

Howdy,

I'm building my first amp which is an "aa764" vibro champ circuit, it puts out 6 watts. I purchased the electronics from triode and upgraded the OT so I have an 8ohm out. I purchased a larger cabinet with a 12" cutout in the baffle so the search is on for a highly efficient 12" speaker.

I would like the speaker to be "clean" and "loud" and sound like a fender without making my ears bleed from shrillness. I play a telecaster and a stringmaster non pedal steel guitar so I need a smooth treble response.

I'm willing to spend more for alnico but "think" I understand that ceramic would suit my low watt amp better. Please feel free to jump in on this.

I have been considering a weber Chicago 12" w/ paper cap or perhaps a NeoMag 12" w/ paper cap but there are no efficiency ratings on webers website. I don't know if 6 watts will drive them hardly.

Jensens vintage offerings have entered my radar, and are in the running.

Vintage JBL's off of Ebay are also up for consideration.

I may use a beam blocker but want to try the speaker without it first.

I am not discounting any speaker and am willing to pay dearly for the "best" possible tone or use something not as expensive if it's better suited to my cause.

Thank you in advance for any useful advice,

Benjamin

A 12" for a SE amp can be a bit hit-and-miss. I found an old 15W Goodmans (Alnico magnet) for a 5F2A build once upon a time, and it was the bee knees. I've tried a range of modern production 12" speakers in SE builds (incl Jensen RIs and Weber Sigs) and most of them sound pretty suboptimal to me. For some reason I find SE amps like 10" speakers better. Just sayin'.

I have a Silvertone 1483 combo amp, (23 watts, 2-12AX7+2-6L6's - 1x15 ceramic Jensen). I've been running it combined with a 2x12 GK closed cab that has Celestions in it, (can't recall the model # off the top of my head but it was the lower end Celestions that were around in the '70's).
Anyway, I have been seriously looking into "Warehouse Guitar Speakers" for some time. They have a couple different versions of their Jensen 1x12 clones. Haven't purchased them yet but am about 90% sold on them.

I suppose I could make a 10" baffle, but I'm pretty set on a 12" speaker because of steel guitar. I have 10's in my super reverb they just don't have the sound i want.

Cheers,
Benjamin

Eminence Lil' Texas neo.

Or any of the Eminence line. I'd go for the Lil' Texas because it sounds a little like a JBL without the vintage D120 price tag. D120sw are nice but they're hit or miss. You can spend a lot o' bucks for a beat or badly re-coned JBL.

TDPRI member jh45gun recently went on a quest for ultimate volume from a Musicmaster Bass Amp. He gave up 1db spl in trade for tone. Track down his MMB posts for the whole story.

I suppose I could make a 10" baffle, but I'm pretty set on a 12" speaker because of steel guitar. I have 10's in my super reverb they just don't have the sound i want.

Cheers,
Benjamin

A super reverb is waaayyy different from a little single-ended vibro-champ. The reason that 10s sound good in SE amps if that they don't carry the same bass as a 12", and the SE OTs otherwise tend to be 'bassier', so the 10" cancel this out a bit. That's my take on it anyhow. YMMV

Interesting... I guess now I'll have to throw 10's into the mix. I want to try a 12" first, I have a few projects on the horizon so it won't be a waste if I end up with a 10".

Anyone know a 12" that has high efficiency so I can get some volume out of this bad boy?

Been looking at the eminence line now and I'm seriously considering a Patriot lil' texas neo.

A bit of serious money for a 6 watt, your not going to get much more benefit than if you used a 1258. I've heard those and it packs quite a punch, also a WGS G12/10C is my other recommendation.

I have been considering a weber Chicago 12" w/ paper cap or perhaps a NeoMag 12" w/ paper cap but there are no efficiency ratings on webers website. I don't know if 6 watts will drive them hardly.

The folks at Weber are really pretty helpful. Here's a quote from the "contact" portion of their site.

"To reach us by phone 8AM to 4PM EST, Monday through Friday, our Tech Line is 765-480-8163 (this line is for questions and orders. status checks are not available on this line)"

I've ordered speakers from them a few times, and each time, I've asked a boatload of questions that I'm sure they've answered hundreds of times before. Yet, they have always been polite and very cool to deal with.

I have had good success with an Emminence Red White and Blues providing the results you are looking for. Others swear by the C. Rex. Muchxs advice is always worth listening to.

Let us know how it turns out.

IIRC, Weber doesn't list efficiency ratings. I've heard people rave about the 12F150 on these boards, both about the tone and the efficiency, but no personal experience myself. You can give Weber a call -- I've always found them to be very helpful.

One last thought -- how about a Celestion Alnico Blue? If price isn't an object, I'd check one out.

Still on the hunt, I can't find an eminence lil' texas in stock anywhere so I'm calling Weber. 100+ dbs seems to be where the eminence efficiency ratings are at, pretty good. Celestion blue? I'll look into it, seems like the gold from them had been in the running.

Thanks everyone, I'll keep posting, once I order a speaker then I'll start wiring the chassis and post pictures as I go. I just finished a "6g15" reverb chassis and am awaiting a cab from mojotone, I'll post that in a different thread once I start testing. I powered it on last night and tubes glowed, jewel light glowed, no sparks so far so good.

Cheers,
Benjamin

Here is the schematic I'm working off of. It looks like I'll have an external speaker out, I'm still trying to understand a few things about ohm's law so if I have an 8ohm speaker in the combo what can I run in an extension cabinet? If the external speaker were to be 8ohms wouldn't that give me a 4ohm load? If possible I would like to have an extension cab with an additional 12" speaker. Any Ideas?

Thanks,
Benjamin

OK, I found a lil' texas neo at Alpha Electronics. It's been ordered. I still would like to figure out what the best route would be to run an extension cabinet, but for now I think I'll start wiring the turret board. If I don't like the speaker after I break it in I'll sell it, but all signs point to it being a winner.

Cheers,
Benjamin

Personally I wouldn't get too hung up on efficiency ratings. All else being equal (or near equal) they might help guide a choice when changing from one speaker to another. But other factors can easily override small differences in dB ratings - resonant peak and Fletcher Munson effect, etc.

But, that said, the Eminence Swamp Thing is very full and transparent at lower power/volume.

Although I haven't tried any, a neo mag speaker might also be an option, since their lower mass should provide better response to fundamentals and less rounding/compression of your tone.

Well, I'm on the hunt again. Turns out my order was cancelled due to "unknown" manufacturer lead time. Anyone have any thoughts on using my external speaker output?

Thanks,
Benjamin

Here is the schematic I'm working off of. It looks like I'll have an external speaker out, I'm still trying to understand a few things about ohm's law so if I have an 8ohm speaker in the combo what can I run in an extension cabinet? If the external speaker were to be 8ohms wouldn't that give me a 4ohm load? If possible I would like to have an extension cab with an additional 12" speaker. Any Ideas?

Thanks,
Benjamin

The two jacks are wired in parallel.

Resistances/impedances wired in parallel reduce by the formula 1/x = (1/a + 1/b), where a and b are the two separate impedances and x is the combined result.

So yes, plugging in a second 8 ohm load to extension jack would result in a net 4 ohm load being seen on the secondary side of the OT.

Ideally the total load on the output transformer secondary should match whatever tap is wired up. If you wanted to use both speakers you could disconnect the 8 ohm tap from the output transformer and use the 4 ohm tap instead.

You could also run the amp with the mismatch. In general a 2:1 mismatch is considered relatively safe, with a low mismatch being somewhat safer than a high mismatch. Mismatches tend to reduce the total power output of the system, but this is often more theoretical than practical and whether it is even noticed depends on multiple factors.

Thanks Keyser! so can I wire both taps to a switch? That would give me a matched impedance in either scenario.

Thanks,
Benjamin

No, that is not what I said.

"you could disconnect the 8 ohm tap from the output transformer and use the 4 ohm tap instead."

Sorry if that was unclear. It means you can connect either single transformer secondary tap to the output jacks (as they are presently wired.)

If you want to get fancy you could add a switch to the back panel allowing you to select which tap gets connected to the jacks.

Another option would be disconnect the hot connection between the two jacks. Then you could wire the 8 ohm tap to one jack and the 4 ohm tap to the other jack. They can share a common ground. You still need to attach the proper speaker load to one or the other (not both!) jacks.

Yeah that's what I meant, a switch on the back to change which tap is hooked up to the jacks. So one side of the switch is the 8 ohm tap and the other side is the 4ohm tap and the switch goes to the jack like in the schematic. If I hook up a second 8 ohm speaker, I flip the switch to the 4ohm position. What kind of switch do I need?

Thanks,
Ben

Yeah that's what I meant, a switch on the back to change which tap is hooked up to the jacks. So one side of the switch is the 8 ohm tap and the other side is the 4ohm tap and the switch goes to the jack like in the schematic. If I hook up a second 8 ohm speaker, I flip the switch to the 4ohm position. What kind of switch do I need?

Thanks,
Ben

You'll need a 3P/SPDT, which means 3 pins (connectors on the bottom) single pole, double throw (means one line, selected between two lines). You can get a 2-position ON/ON switch of this kind, or a 3-position ON/OFF/ON for this type switch.

Sorry if you aleady know all this, but a lot of folks don't... like me about 2 months ago! :wink:

Here's my 4/8 ohm mini toggle in a 5E3. I only have one output jack, but will have another connected to a recessed plate on the back panel for easy access. Yellow 4 ohms and green 8 ohms on each side, switched and fed to the center orange pin to the tip of the output jack. Simple!

charisjapan

http://farm8.staticflickr.com/7074/7367622238_9bfdfa6418_b.jpg (http://www.flickr.com/photos/charisjapan/7367622238/)

That is precisely what I needed to know. Thank you! Now I'll be able to run a few different speaker combinations w/ the proper impedance.

Ok, so I ordered a cannabis rex and it'll be here saturday. I also got to thinking I needed an amp between practice volume 6w vibro champ and my super reverb for a gig coming up, so I ordered a used DRRI, I think I will put the c-rex in it for a little while to break it in and putz with it a little while I wait for some switches and other parts for my vibro champ. I have never engaged the bright control on my Super Reverb so that Bright Cap is bound to go and a round of new tubes are on the way:


1 NOS Phillips 5751

2 NOS RCA 12AT7

2 jj 12ax7s gold pin sorted for low noise

2 electro-harmonix 6v6 matched set

We'll see if I can find a lil' texas neo at some point but for now this is what I'm trying. I'll start a new thread soon when I start the Vibro Champ Build.

Cheers,
Benjamin