How hard can you push a speaker?

[cowboy]

Hi! I'm planning to build a 2x12 guitar cab for a 50W amp, I'm planning to put jensens in it, but I'm not 100% sure 'bout which model i shoud go for. I'm choosing between the C12Q(35W) and the C12N(50W). I was pretty sure that I'd go for the 35W until someone said that two 35W speakers wouldn't be enough power for a 50W amp(the amp would "push the speakers too hard"), and recommended to go for two 50 watts instead(to kinda be on the safe side). I think that this sounds a little strange? Can someone please explain?

[J M Fahey]

Those 50 (clean) watts can turn into theoric 100W squarewave when heavily overdriven.
Real world power supplies won't allow that, but you could easily slam your speakers with 80 or more dirty watts.
Voice coils don't know about clean or dirty, they just heat up, in this case beyond their safe temperature limit.

[cowboy]

So it's OK to go with two 35(clean) watts on a 50 watt amp?

[Robert M. Martinelli]

Hi,

a decent 50W amp with a decent PS section will easily put out 70W or more during loud transients, as JM wisely said.

A good rule of thumb is that the speaker(s) has (have) to be able to withstand twice the amp's RMS rated power. By doing so the chances to damage the speaker(s) by overheating the voice coil(s) are practically non-existent, even keeping the amp continuously cranked at its max.

I'd definitely go ahead with the 2 x 50W speakers arrangement

Hope this helps

Best regards

Bob

[txstrat]

I've had a look on the Jensen website for the C12Q (website for the C12Q) and they claim 35W RMS as well as 70W musical power. I don't know if musical power means peak (for a short amount of time) or continuous in their sense of manufacturing.
I can't think of an amp (at least not in my 32 year experience in guitar playing) which is all the time at full output (i.e. distorted) unless you play power chords and never release the strings (but that wouldn't be music anymore and you might as well buy a jackhammer ).
Musicians are usually (IMHE) short of money for their equipment and the C12Q cost a good amount less than the C12N (I believe that was partly your intention of the question rather than sound differences?).
I'd say if you don't abuse the C12Q too much you could get away with them.
Too be on the save side I'd definitely go with Bob.
I know this doesn't make the choice much easier.

[cowboy]

I've had a look on the Jensen website for the C12Q (website for the C12Q) and they claim 35W RMS as well as 70W musical power. I don't know if musical power means peak (for a short amount of time) or continuous in their sense of manufacturing.
I can't think of an amp (at least not in my 32 year experience in guitar playing) which is all the time at full output (i.e. distorted) unless you play power chords and never release the strings (but that wouldn't be music anymore and you might as well buy a jackhammer ).
Musicians are usually (IMHE) short of money for their equipment and the C12Q cost a good amount less than the C12N (I believe that was partly your intention of the question rather than sound differences?).
I'd say if you don't abuse the C12Q too much you could get away with them.
Too be on the save side I'd definitely go with Bob.
I know this doesn't make the choice much easier.

Nope, that didn't make the choice easier, haha! But the amp I'm gonna use for the cab is a Silvertone 1484(Twin Twelve), and I believe that the original 1484 cab was fitted with two C12Qs, but I'm not 100% sure. Amazingally enough, money isn't a problem(this time). The 35 watts has a midrange bite that the Ns doesn't have, but if it's safer to go with the 50 watts I guess that's what I'll do! Thanks!

[Brad1]

Keep in mind that more than one speaker will share the load, so you can use lower power-rated speakers...to a point.

Otherwise, all those many thousands of 25W Greenbacks in 4x12 Marshall cabs pushed by cranked 100W Marshall heads would never have worked.

Brad1

[txstrat]

If you compare the wattage (RMS or cranked) it might be like this:

amp: clean (RMS) 50W - speakers: clean (RMS) 70W (for two C12Q)
amp: cranked (I don't know, some 80Watts?) - speakers (musical power) 140W

This would confirm Brad1's conclusion and might confuse a good heap more.

[Bruce / Mission Amps]

Hi! I'm planning to build a 2x12 guitar cab for a 50W amp, I'm planning to put jensens in it, but I'm not 100% sure 'bout which model i shoud go for. I'm choosing between the C12Q(35W) and the C12N(50W). I was pretty sure that I'd go for the 35W until someone said that two 35W speakers wouldn't be enough power for a 50W amp(the amp would "push the speakers too hard"), and recommended to go for two 50 watts instead(to kinda be on the safe side). I think that this sounds a little strange? Can someone please explain?

1.) How do you know it is a 50 watt amp? 50 RMS or peak power? Most std 6L6 amps have a hard time making more then about 45 watts of clean power anyhow.
2.) That's the rub... as others have mentioned, 45 watts RMS (if there is even such a thing, RMS watts) would easily hit 60 watts in peaks.
3.) The majority of all the extra wattage you are hearing about is moving into square wave signal with muscle behind it, which means the excursion of your voice coil is about the same but now it's held out there against it's will and for a longer time, then accelerated backwards to the reverse excursion and held there against it's will, again for a longer time ... time x power is very BAD for a low power voice coil.
4.) There is a reason Fender used 35w to 50 watt speakers in their Pro Reverb, which on a good day has a hard time making 40 watts dead clean.
5.) An "80-100 watt"Twin has 50 watt speakers but most can't make more then about 80 watts.
6.) The most sought after 22 watt Deluxe Reverb amp came most frequently with a C12Na speaker.... yet it is only a 22 watt amp.... go figure.
7.) And in conclusion.... I bet two reissue 35 watt C12Qs could stand up to any normally operated "50 watt" guitar amp.

[J M Fahey]

Hi bruce.
I basically agree with you, but would like to add some small details.
If the reissue were faithful to the original, (which it is not), the voice coil should be of roundwire copper, wound on a *paper* form (real, cellullose paper, either Kraft (brown) paper or some akin to good (white) drawing paper) and glued with nitrocellulose lacquer ( similar to dope or duco type).
Sound would be heavenly, but it would handle 15/18W .
Reissues cheat using kapton forms and epoxy adhesive, and manage to handle 35 W; the sound is not bad at all, but "vintage" my 4ss!
In fact that same coil (or a close sister) is used on Celestion G12L35, G10L35, and a bunch of Laney HH or Invader 10" and 12".
*Maybe* on that particular model they use an intermediate material called Nomex, which is "paper", sort of, but its fibers don't know what a tree is, being closer to Nylon (they are called aramidic fibers).
Being intermediate means they sound closer to paper, handle a bit more, but not Kapton power levels.
That's why using a pair of 35W speakers with a 50 W amp (I agree, those 50 are a little optimistic) makes me nervous.
Being such low mass objects, you don't need 2 hours continuous squarewave to overheat them, the end of a song with 30 to 45 seconds sustained overdrive (courtesy of some pedal), or power chord feedback may be enough.
Problem is, any thermal damage is usually irreversible.
Kapton is quite strong , and burning epoxy adhesive is difficult, it will take a lot of punishment, but typical failure mode with Nomex is a bubble in the base material which later scratches so much as to make your life miserable.
Typical failures on nitrocellulose glued coils (the real vintage ones) are in order of sickness:
1) a bubble in the adhesive, that will scratch as above;
2) a partial adhesive meltdown; since the voice coil is moving back and forth at high speed, a couple turns on either side turn loose; the speaker starts buzzing until in a short time that flexing wire cuts and the coil gets open.
Nitrocellulosic starts softening an 70/80 ºC (degrees Celsius or Centigrade), bubbles at 90 ºC , browns and cracks over 100 ºC (boiling point of water) and takes fire spectacularly above that.
Why shouldn't it? It's made of smokeless gunpowder dissolved in acetone !!
That's why Bassmans used 4 x 10" speakers; 50W Plexis 4 x 12" G12 (no letter, the only ones and the moment) and Twins burnt their C12N when overdriven.
In short: those C12Q *may* stand your 2x6L6 amp, *if* they are not as vintage as they claim.

[Bruce / Mission Amps]

Start with a good speaker

If the key is "better to be safe then sorry".... I'd use the higher wattage speakers, but pick something that sounds really good for the amp in question.
Since we don't really know what that amp is, it will be up to you to determine what choice it will be.
In fact, I mostly use a 30 watt Englishy tuned speaker in my 15-18 watt 6V6 amp and a 60 watter in my 6L6GC, 32-45 watt amp.
But in my tweed Vibrolux (Modded with slightly bigger trannys, a 12" speaker, makes an honest solid, dead clean 16 watts and overdrives the 6V6s in glorious technocolor) I love the sound of a 100dB/watt NEO magnet Tonkerlite speaker, which is, (probably unfairly) rated at 125 watts!

Mojo Speakers Eminence Tonkerlite Speaker 12'' 8 OHM 125W

[R.G.]

I don't know if musical power means peak (for a short amount of time) or continuous in their sense of manufacturing.

"Musical power" literally means "I think we can sell more of these if we can somehow claim a bigger number in the advertising and not lose a court case over it."

[txstrat]

It's not funny, though.

[tedmich]

the "competition car stereo" guys use a <1s white noise "burp" to peg a db meter at >180db, and the speaker manufacturers just use these numbers for "power handling"


(The WAS 3000, (165 dB) PHOTO BY WYLE LABORATORIES)

no one wants to listen to this crap longer than 1s luckily...

[Timstonepizza]

Push

I don't know but what if it pushes you back?