Eating speakers for breakfast...

[SonicProvocateur]

So...I'm used to the fact that my 60 watt monster eats preamp tubes for lunch. I've finally settled on using chinese stuff for its high gain capabilities and reasonable cleans so I can keep piles of them around for quick swaps. I'm also lucky enough to have 2 pairs of phenomenal sounding Sylvania 6L6's that pound out almost unreasonable power.

This said - I have now melted/farted out a 120 watt Marshall cab, and now I put in a Sheffield 1230 mixed with a 80watt Celestion 70/80 and the Sheff blew up so hard I couldn't even tell it was dead until I tried to use it in stereo and there was zero sound - the 70/80 has been doing all the work.

So here's the question - I have a V30 and a G12H30 sitting around out of a Z-Best cab. Think it'll handle the 60 watt mayhem? I'm worried about that Heritage after the Sheffield kicked the bucket and the Marshall cab farting out.

 

[Rob Lockwood]

Well you could try it, but it all depends on the volume/gain levels you play at.

In a 2x12, if both speakers are the same impedance the 60W will share equally between the two so at 60W the G12H should just be ok seeing 30W, but:

Amps are usually rated at the max, power output that can be achieved with no more than 5% THD (total harmonic distortion). I dont know how 5% THD sounds, but given that it was the standard for all audio amps, not just guitar, I guess it must be what guitarists would still call a clean sound. However as you crank the amp up into more distortion the power output keeps going up well beyond that rated level. I have read that an amp that is fully cranked up and distorting well can kick out around double the rated power (and Boogies always seem loud for their rating). Thats why a Marshall 100W head would be used with say 4x12 vintage 30s giving a 240W cab, when using the old 25W greenbacks two 4x12s were needed and why a 100W Boogie Mark needed a 200W EV or similar to get away with the 1x12 combo format. Speaker ratings may be a bit on the safe side and amps are rarely 100% cranked, so I am sure there are cases where you can push the limits but its at risk.

If you are playing with loads of gain and cranking the master volume high I expect that you will blow up the 30W speaker fast as it could be seeeing double its rated power. Two V30s would probably be ok but on the limit and may not have a very long life. Obviously as you reduce the gain/volume you will get away with more but to be safe running flat out I would suggest a 150W+ cab for this amp.

 

[SonicProvocateur]

Well you could try it, but it all depends on the volume/gain levels you play at.

...

If you are playing with loads of gain and cranking the master volume high I expect that you will blow up the 30W speaker fast as it could be seeeing double its rated power.

Generally, when I play at home I'll play quietly until my ears adjust then maximize the volume until I find where I have the most loudness to dynamic range ratio. As you've pointed out and I think we all know - boogies are rediculously loud and that spot comes on early. My 60 hits that spot right about 3.5 on the master and about 5.5/6 on the lead master. Past 4 and there is not much increase in clean dynamic volume. I am always trying to peak my Mesa, which is (why I assume) I have this speaker blowing problem. Live obviously we have to adjust for the sound guy.

what preamp tubes are you using that are getting eaten up ?
I find that the sovtek lps fail really quickly for some reason in my boogies yet they last ok in other amps

Yeah. I love the dark, gainy sound of Sovteks and those have definitely been on the "got killed in 3/4 months" list. The Chinese seem to see about 75 hours before they lose their edge and get moved into the backup pile. The strong ones get to stay lol.

Report on the speakers: I put them in the 2x12; did a quick test on a low power solid state to test the stereo/mono switch and the speakers were working: all ok. Hooked it up to my 50 watt Marshall Vintage Modern. The sound is more open and less compressed than the 70/80. I kinda miss that...The "vintage" sound is there in spades when I finally cranked the VM to 75% volume (the VM puts out 50watts at 100%, unlike a JCM, Plexi, etc). There was a bit of a hiss at startup, but I attribute that to likely tube noise. Seemed to work fine once it was good and warmed up and blasting away. Very woody, open, and vintage sounding. Again, lost some midrange compression that gave the Vintage Modern a Soldano sound on the high gain - now it sounds like a plex; all the classic sounds now!. Im still kinda nervous about melting the Heritage knowing the Mesa peaks above 60 watts. Thoughts?

 

[SonicProvocateur]

Another update: I didn't blow them up, but I certainly felt like I knocked all the midrange out. Maybe breaking them in too aggressively with the Mesa? Anyone ever have this issue with G12H30's? I kept switching my EQ (set in the old Petrucci V) on and off, and it didn't seem to make a difference so I dunno if my break in techniques have done something to the speakers right there in the 750 band...

 

[McBarry]

Sounds like you've burnt out a few speakers now.. (exactly how many over what period??)
And killing the mid-range could also be an amp issue rather than a speaker one.
Equally, is it possible the mid-range was a hearing issue on the day - not trying to be funny, but at the levels you describe it's certainly possible..

It'd be sensible to have a tech look at it to see if the amp IS actually going OK.
Sort of things I'm thinking are gain anomalies giving mega-distortion and ***** waveform(s), maybe power issues (fluctuant, ripple-from-hell, bias anomalies in the power tubes etc etc)..
THEN I'd get 'em to have a look while amp is at your usual settings - no sense driving it sedately, all good, then when U open it up all hell breaks loose.

Feeding it speakers indicates a problem to me, either inherent in the amp/speakers or in the way they're being driven.

Keen to hear the outcome,
Dave

 

[SonicProvocateur]

Yeah, i've said it here before it needs its 15+ year checkup, including new filter caps, etc. No doubt the bias has likely drifted (since mine is a bias mod amp, now pushing really gnarly Sylvanias). Thing is, I hooked the virgin celstions up to my Marshall and it seemed to give the same effect - I compensated for it by backing off the presence about 25% and it brought the tone back down to where it was - granted the Marshall could likely use a rebias too. The amp didn't wicked kill the first pair of Eminence speakers, but it did the same thing, took all the beef out of the mids so you would have to crank the piss out of them to make em sing. It straight annihilated the Sheffield. The 70/80 is the long survivor and it still sounds fine. This is over a 3 year period.

I do need to fire it back up and see how she's doing though. For the last few weeks I haven't been running either amp on my power conditioner, but It doesnt brown the tone any; it does fix some low level hiss though. I run right at 120-124v here at my house. My one thought is that either V1 or V4 might be taking a dump on me since the tone was acting a fool on all channels. Thanks, Dave.