Can anything blow a speaker in a tube amp besides overpowering it?

[Gaz]

I recently had a 80W Showman head kill two brand new Celestions Creamback speakers. They are 65W speakers, and were wired in parallel. All the wiring checks out, but both speakers are reading open (infinite DC resistance). Amp seems totally fine playing through other cabs now.

Any thoughts on how this may have happened? These are the first speakers I've ever fried in my lifetime.

[Tom Phillips]

If it was a solid state amp then we would be considering the possivbility of DC at the output terminals. Since I think you are talking about a tube type Showman then one possibility is that the amp temporarily went into ultrasonic oscillation. That could fry the voice coils. Why it seems to be fine with other speakers now is unknown. Keep in mind that this is just one possible theory that answers your question.

[TomCarlos]

Gaz.... Just curious... You were using 2 Creamback speakers ... what was the speaker impedance of each speaker?

[g1]

Brand new? Will you be sending them back for warranty evaluation? They will do an autopsy and perhaps they are defective.
Do the cones move freely by hand now or is there resistance and noise like they are burnt?

[The Dude]

Do at least reach in past the terminals and check continuity on the tinsel leads themselves. Sometimes the leads burn right at the terminals from too much heat. It's an easy repair.

[olddawg]

Low frequency will kill speakers. A bass or a keyboard through a guitar speaker can blow it immediately. A lot of people use Showmans for bass.

[J M Fahey]

Not everybody rates speakers the same way.
For some, "65W" means "I can tolerate 75/80W for up to 30 minutes", for others "75/80W will fry me in about 2 minutes".

Notice that besides power rating I added a time constant, which is almost never mentioned in ratings.

In the particular case of Creambacks, I think they are "improved Greenbacks".

Havenīt had them on my bench yet but I guess they are "Greenbacks in all aspects except they use Nomex voice coils and are glued with modern adhesives".

Whatīs the difference?

You can build different speakers on basically same frame and magnet structure.

* use a paper voice coil (cellullose toasts, becomes brittle and crumbles at 100C and above) , old Duco/nitrocellulose adhesives, which soften at 90C , bubble above 100C and catch fire at 140C, and you get a very light and nervous voice coil which sounds like Heaven but stands only 20W ; or 25W if you wind your voice coil on somewhat stronger brown Kraft paper (the one used in flour/cement bags). You can slap a green plastic cover on these and call them Greenbacks

* wind it on Kapton space age plastic, which stands up to 400C , glue it with Epoxy which stands 180>250C depennding on type, do NOT use a cover, leave metal exposed which helps with dissipation, and call it G12T75 , will stand 75W all day long and bursts of 80/90W for short times.
Itīs the current standard Marshall speaker (typical one in 4 x 12, single 12 Valvestates, etc.) , not bad at all but seen by many as harsh and "barking".

* so how to get (most of) Greenback sound with (almost) Kapton power handling?
you wind your voice coil using modern adhesives (which are strong but heavy and take some sparkle away) and use Nomex , which is "modern paper": it *is* "Paper" no doubt: instead of the solid (*heavy*) laminated plastic sheet which Kapton offers, you get fluffier "paper" made out of random unwoven fibers (just like the real one) , with air in between (again) but said fiber are not cellulose but synthetic Aramid plastic which are guaranteed to some 200C.

Looks like best of both worlds, a very reasonable compromise, and speaker will almost sound like a Greenback but stand almost like a 12G75T .
You may slap a cream coloured plastic over it if you wish

Personal observation: the idea is very good, but they were somewhat optimistic on rating.

Although as said above I have not yet repaired a dead Creamback, I wind my own voice coils, including "modern adhesives on Nomex paper" and prsonally wouldnever rate them for 65W each, no way.
50W each sounds way more realistic and I guess Weber rates them about the same in that size (44 mm "British" diameter), he definitely rates them 30W in 38mm "Jensen" diameter.

My point then is that Creambacks are excellent speakers, but should be treated as "safe 50W" speakers.

But do they stand 65W or not?
Definitely ... but not forever ... I wouldnīt drive them that hard.

A 4 x 6L6 amp has enough muscle to kill 2 of them, if driven hard.

IF reconing them, and still using the same head, Iīd use G1275T Kapton voice coils.

Avoid the aftermarket Aluminum base voice coils, they stand a lot of power so are often used by reconers to make certain the speaker wonīt come back (based on the logic that the original one WAS burnt after all) but itīs way heavier than Kapton, let alone Nomex or paper, and sound dulls a lot.

[Gaz]

Gaz.... Just curious... You were using 2 Creamback speakers ... what was the speaker impedance of each speaker?

Each speaker was 16 Ohms, wired in parallel for 8 Ohms.

Brand new? Will you be sending them back for warranty evaluation? They will do an autopsy and perhaps they are defective.
Do the cones move freely by hand now or is there resistance and noise like they are burnt?

Nothing odd physically with the speakers. They seem like they were just taken out of the box. No smells or seized up cones.

Yes, I had put about 10 hours of loud playing on them before they went. My theory is one failed without me realizing, then the remaining speaker was overpowered. No evidence to support this...

Do at least reach in past the terminals and check continuity on the tinsel leads themselves. Sometimes the leads burn right at the terminals from too much heat. It's an easy repair.

Yes, I did, and still nothing. No smells of any kind either.

Low frequency will kill speakers. A bass or a keyboard through a guitar speaker can blow it immediately. A lot of people use Showmans for bass.

Just guitar through this one. Jazzmaster on the bridge tuned down to Drop C. Lots of distortion, but nothing at all out of the ordinary.

[Gaz]

Thanks, Juan, what a great post. I gleaned a lot from that.

Maybe to be safe I will save the the repaired Creambacks for a 4x12. Do you think two Vintage 30's would be a safer bet based on their construction? They are nominally rated at 60W.

[olddawg]

Each speaker was 16 Ohms, wired in parallel for 8 Ohms.



Nothing odd physically with the speakers. They seem like they were just taken out of the box. No smells or seized up cones.

Yes, I had put about 10 hours of loud playing on them before they went. My theory is one failed without me realizing, then the remaining speaker was overpowered. No evidence to support this...



Yes, I did, and still nothing. No smells of any kind either.




Just guitar through this one. Jazzmaster on the bridge tuned down to Drop C. Lots of distortion, but nothing at all out of the ordinary.

Downtuning and using heavy fuzz is very hard on speakers. Like using a bass or a keyboard. If you also have the amp saturated it's putting out more than 80 watts as well. Really going to heat up a voice coil.

[J M Fahey]

Thanks, Juan, what a great post. I gleaned a lot from that.

Maybe to be safe I will save the the repaired Creambacks for a 4x12. Do you think two Vintage 30's would be a safer bet based on their construction? They are nominally rated at 60W.

I have seen 2 x G12T75 Celestions in a JCM800 combo go on for ages, but the V30 might be just too close for comfort.

To play it REALLY safe Iīd use 2 x G12T100 and sleep like a baby.

If too expensive, there is a 150W rated Eminence where a pair also should last a lifetime, but they are somewhat duller than Celestions.

[Tone Meister]

Juan is the speaker guru here on the board but I can share a recent personal experience with the same speaker.

I purchased a Celestion Creamback-M (65 watts) to evaluate about three weeks ago. Very good sounding speaker, in fact THE best sounding speaker we tried while evaluating speakers to mate with a specific amplifier. Excellent balance across the frequency spectrum, excellent clean tones and some of the best high gain tones I've ever heard ...

... for nearly three minutes. Playing at moderate volume, I literally heard a muted "snap" sound and volume dropped to half and a slight burned smell filled the room. I immediately thought "power tube failure" but a quick check of the amp proved the amp was perfectly healthy. Impedance meter on the speaker revealed a failed speaker coil.

So I had a Creamback-M 65-watter last almost three minutes, which is the only guitar speaker I have ever blown in 45+ years of playing. However, that didn't deter us in the slightest since it sounded so good. We sent back the failed driver and ordered a fresh pair of Creamback-M 65s to load in a 2x12 cabinet for touring (after some rigorous testing in the rehearsal space first)

Like Juan said, some speakers are rated conservatively and some are rated right at their breaking point, and since no parameters are included with the rating (see Juan's posts) then who the hell knows what actual meaningful value the ratings have for the end user? Celestion speakers historically are known to handle well past their nominal power ratings, but with the current lot of Creamback-Ms in the supply chain who knows. It could be a design issue (improved Greenback as per Juan) or there could be some QC issues with this particular lot.

I know from actual test bench measurements that a typical tube amp can and will exceed its rated output power by 25-30% or more on any given Sunday. Examples? We have a Landry LS100G3 here rated at 100 watts that produced a measured 133 watts RMS and an 85-watt Twin Reverb that easily produces 104 watts.

You probably just need "more speaker." Perhaps the Creamback-H may be better suited for your application if you plan to use just two drivers.

[Tone Meister]

I have seen 2 x G12T75 Celestions in a JCM800 combo go on for ages, but the V30 might be just too close for comfort.

To play it REALLY safe Iīd use 2 x G12T100 and sleep like a baby.

If too expensive, there is a 150W rated Eminence where a pair also should last a lifetime, but they are somewhat duller than Celestions.

I really like the Eminence Swamp Thang with Fender amps. We load Fender Twins (Showman reincarnate) with pairs of these all the time, and the pros on the black gospel circuit are winding those 100-watt Twins up to 7 or 8 on the volume and those 150-watt Swamp Thangs handle it without breaking a sweat. Just an excellent sounding speaker that I feel sure would "last a lifetime" under your Showman, and there's not a dull sound in them anywhere. Compare the Swamp Thang to the Texas Heat and consider them both unless you're set on the Celestion Creams.

[potatofarmer]

+1 to the Swamp Thang in Fender amps. It's definitely an "American"/Jensen-type tone though and very efficient so it may not meet the tone that the OP was looking for.

In theory an amp can put out roughly double its clean wattage when fully cranked, but guitar amps typically have power supplies that won't provide enough current for that and the "clean" power ratings are, well, optimistic at best. I always shoot for the load to be rated for double the amp's rated power.

I also found something interesting out looking at a pair of cabs I got recently - Electro-Voice S15-3. Originally EV rated these cabs at 100W, and they explained their methodology - pink noise for 24 hours, IIRC. The next iteration they labelled "S-1503" and using the same drivers and crossovers, now rated as a 200W cabinet. Again they listed their methodology - pink noise for 8 hours.

There is a standard for measuring speaker power handling - AES2-1984 - which is apparently a 2-hour test. This explains a bit more: http://eaw.com/docs/6_Technical_Info...r_Handling.pdf

buuut who knows if Celestion follows this methodology. I imagine they might at least for their PA drivers, but guitar speakers are kind of like the wild west as manufacturers know that the primary spec that customers are interested in is tone. Some manufacturers - Weber and Warehouse come to mind - don't provide any specs at all besides a thermal rating and a little poetry about how good it sounds.

[J M Fahey]

Surprisingly (or not, once you analyze it), I found worst speaker killers are not Metalheads but Punks.
Didnīt get it in the beginning, but customer statistics showed that, so ... there must (should) be a reason for it.

I *guess* metalheads, as distorted as they often sound, whether chainsaw sound or down tuned chugga chugga, ARE looking for a certain "tone" , so as soon as they start losing it they stop and back down a little, bur Punks? , they have no idea of tone and keep strumming distorted chords 24/7 ... speakers canīt "breathe" and die.