Speaker question: Celestion g12-65 breakup

[Chevy]

Hi guys,
I've mounted a G12-65 in an open-back cab, and am running it thru a Boogie 50 Cal +. Guitar is a Strat tuned to Eb.
The speaker sounds great to me, but when I open the amp up to just number 2, the bottom end is pretty distorted (low E string). I checked out the amp on a scope, and it seems to be able to put out a clean 80Hz sine wave signal at about 42 watts output. So... although I can't be positive, seems like the breakup is from the speaker... (but then again, I can't test the amp with multiple signals into it at the same time to see if the amp is the problem.) Unfortunately, also, don't have any real decent higher powered speakers to compare with at this time.

The speaker is spec'd at 85 Hz resonant frequency... my guitar is tuned down below that. Could that be the problem? I wanted to get some nice clean punch down on my open low E at a good volume, but don't know if I can do so with this speaker or not... Would it maybe have to be in a sealed box to work better?

Thanks kindly,
Chevy

[Chuck H]

Considering all the dynamics and anamolies that can happen with guitar I'd say that live experience trumps specs every time. You'll need to try a speaker known to handle the circumstances before you'll know.

I play a strat tuned to Eb through a 1x12 open back combo all the time. The cab is loaded with a V30 (well broken in, but not known for it's bottom end) and bass is not a problem though I would not say I have more than enough. Point is that it should be working if the speaker is up to it.

I will point out that the G12-65 is typically loaded in a 4x12 closed back cabinet. Multi speaker closed back cabs have several effects that can't be relied on in a single speaker open back cabinet. Phase cancellations (most pronounced in the treble) and a much greater mass of air moving (more bass) as well as limiting speaker excrusion (tighter bass). It all adds up. A speaker that would be light on bass and a little harsh in a 1x12 open back cab might be just right for a 4X12 closed cabinet.

[Chevy]

Thanks, Chuck,

What amp are you driving the V30 with?

[Chuck H]

It's my own amp. A prototype of a design I did for someone else. So that's not really going to give you much of a point of reference. It's not a bass heavy design though, like a BF Fender can be.

I'm not that familiar with the 50 cal+. I've heard that it's one of Boogies worst amps and also that some players wouldn't use anything else. I take that to mean it's a love it or hate it, which means it has it's own sound. I can't comment on the bass character of that amp but I can say that pairing an amp to the right speaker can make all the difference in the world. What speaker were you using before, and what was wrong with it?

How the amp is set up can have a great deal to do with bottom end clarity. Because of the typical Boogie topology and values for their amps of that era I've noticed that many will "crackle" on the attack when the bass is set too high with a hot pickup. Especially when trying to get big bass on a clean tone. How hot is the input signal your feeding the amp? Is it as hot as the peak attack voltage of the pickups your using? There are a lot of variables.

I think you should try the amp through another speaker first. If the results are the same it's the amp or the way it's set up. If it cleans up then it's the speaker.

[Chevy]

This is a "new" amp for me, so I wasn't using any other speaker before on it. I've got some age-related issues, and was tired of humping around my very heavy bandmaster reverb, the boogie being much lighter. I used to use a pair of ancient anemic Carvin 12's, but am upgrading to the Celestion or something similar for the tonal improvement... it does sound great on the mids and top end. The Boogie is capable of lots of bottom end, by the way, as you can crank it up via the EQ section. It sounds very much like a Fender, just using the clean channel; don't use the overdrive.

As for the signal level, I have Van Zandt Vintage pickups, going straight into the amp, so there's no heavy level at the input. I think I'll try watch the speaker signal on the scope while it's actually connected to the speaker, and do the same test again, see if the amp is clipping or not when the speaker is starting to break up (just never thought of doing that before.... d'oh!).

[J M Fahey]

lots of bottom end, by the way, as you can crank it up via the EQ section.

That may very well be (one of) the root(s) of the problem.
Graphic (and parametric) EQs can boost insane amounts of any frequency which the speaker can't handle at all.
Personally I try amps with its own EQ (B/M/T) because it usually causes no big problems, as in it was developed "organically" as part of said amp design, but "general purpose" EQs are something else.
I try them with the graphic flat and call that sound "the real one".
You can attenuate "ugly" frequencies, but boost only very little; a couple dB at most because usually that's where the speaker is weak, mechanically, and no electronics will solve that.
Hope this makes sense to others as it does for me.

[Chuck H]

I agree JM.

It's still true that the G12-65 wouldn't be my first choice for a 1x12 combo. What about a Boogie speaker. That's what the amp was designed with. I know the Boogie "90's" were once made by Celestion and I think they still are. It's really good sounding for a 1x12 combo. Something like $120 US. I'm not a huge fan of most Eminence speakers but the Cannabis Rex is very efficient, has good top end clarity and tone but is somewhat rolled off (can be really good if your amp is harsh) and generous smooth bottom end.

If you have a year to wait for a good tone I can say that the V30 is a great speaker. Harsh and middy out of the box but smoothes out after it breaks in and sounds great for both clean and distortion tones. It's called a V30 but it's actually a 70 watt speaker.

[Chevy]

Thanks for the comments, guys.
The Boogie and V30 are good suggestions, as both have been obviously very successful.
I don't quite get something here, though... I know John Mayer uses some g12-65's in open backed cabs, and Robben Ford did as well... that's why I wanted to try this one... as both guitarists have killer tone. I would've thought that playing at the levels they do, the G12-65 would have to hold up or they just wouldn't use it. But then again, maybe they don't have the bottom end dialed up on those particular cabs... dunno. There is definitely some magic to my ears in the -65... hopefully can find it in another speaker as well.