Will I blow my Celestion Blue w/an Egnater Rebel 20? other speaker reccomendations?

[Weshunter]

I have a celestion blue in a 1x12 extension cab that I built. right now i have a fender deluxe vm (40w) which i never need to turn up that loud. anyway, long story short, i didn't realize the wattage problem and am lucky i didn't ruin it. I am getting a Egnater Rebel 20 and depending on whether or not I like it, I might sell the Deluxe and go with it. If I do that, will I be okay to run the 20w rebel through my Cel Blue at the full 20w? I've heard that Blues are actually rated higher than the 15w they're listed at, but i've also heard that 20w tube amps, when cranked w/OD actually run hotter than 20w. If you couldn't tell, I don't know alot about speakers, so any advice will be greatly appreciated.

So, should I sell the blue and buy a higher wattage speaker? I have a little extra money to throw on it and so was thinking about selling the blue, adding an extra $100 or so, and buying 2 weber bluedogs and building a 2x12 cab. Am I going to be really bummed to hear the Bluedogs after having the Celesion (which I do really love, btw)?

 

[FrankenFretter]

I'm surprised nobody has answered this yet. I would think that you'd be better off with a speaker that has a higher rating, just for the sake of safety. Better to have a little headroom that have to suddenly replace a speaker that you hadn't planned on replacing. Somebody with more speaker wisdom than I have will probably chime in soon, but I would think a 30-40 watt rating would be about right.

 

[tunghaichuan]

I'm surprised nobody has answered this yet. I would think that you'd be better off with a speaker that has a higher rating, just for the sake of safety. Better to have a little headroom that have to suddenly replace a speaker that you hadn't planned on replacing. Somebody with more speaker wisdom than I have will probably chime in soon, but I would think a 30-40 watt rating would be about right.

My rule of thumb is about 2x the RMS output for a speaker. So for the Tweaker, you'd want at least a 40w speaker. An even higher rating would increase the safety factor. And yes, you can drive a 75W (or better) guitar speaker with a 20 watt amp. Most amps are rated at clean output power and minimal distortion. When you crank a tube amp it puts out much more than the clean rating would indicate due to harmonic distortion. A "50-watt" Marshall will put out in excess of 75W when cranked up all the way.

The Blue is kind of spendy isn't it? I wouldn't use the Blue with your Tweaker. You risk burning out the voice coil.

 

[Eric]

My rule of thumb is about 2x the RMS output for a speaker. So for the Tweaker, you'd want at least a 40w speaker. An even higher rating would increase the safety factor. And yes, you can drive a 75W (or better) guitar speaker with a 20 watt amp. Most amps are rated at clean output power and minimal distortion. When you crank a tube amp it puts out much more than the clean rating would indicate due to harmonic distortion. A "50-watt" Marshall will put out in excess of 75W when cranked up all the way.

The Blue is kind of spendy isn't it? I wouldn't use the Blue with your Tweaker. You risk burning out the voice coil.

The only question I have about this is that I think you can get a Vox AC30 with Celestion Blues, which would be a 2 x 12 amp, right? Is the AC30 a class A amp? If so, I'm not understanding how a loud class A tube amp can get by with two 15-watt speakers.

I might be full of misinformation, but that's why I'm asking the question...

 

[duhvoodooman]

The only question I have about this is that I think you can get a Vox AC30 with Celestion Blues, which would be a 2 x 12 amp, right? Is the AC30 a class A amp? If so, I'm not understanding how a loud class A tube amp can get by with two 15-watt speakers.

From what I've read, though Vox claims that the AC30 is Class A, this is "marketing speak" and the amp is in fact what is called class AB1, connoting that the grid voltage is always negative with respect to the cathode . Power output is actually closer to 40W in the newer "CC" series amps. Apparently, driving the 15W rated Celestion Blues (x2 = 30W rated power handling capability) near the limit of their capacity helps create the characteristic AC30 overdriven tone. And my guess is that they'd just love to sell you a replacement speaker, if you blow one out. At a modest markup, of course...

 

[Eric]

Apparently, driving the 15W rated Celestion Blues (x2 = 30W rated power handling capability) near the limit of their capacity helps create the characteristic AC30 overdriven tone. And my guess is that they'd just love to sell you a replacement speaker, if you blow one out. At a modest markup, of course...

Ah, there we go. I was wondering if speaker breakup might have something to do with it. Thanks!

 

[Weshunter]

what if i got a 30w speaker and paired it with the blue in a 2x12 cab? that would be a total of 45w. would that be safe with the 20w head? and would the difference in wattage be a problem? for instance, would the 15w speaker start to break up at a lower volume than the 30?

would it be better to go with 2 30w speakers or would that be too much wattage? i could get an additional 15w speaker, but that would only put me up to 30w, which might not be enough especially if I end up playing this rig pretty cranked up a lot, which is a strong possibility.

 

[duhvoodooman]

As long as the two speakers have matched impedances, which is what you'd want, you'll be splitting the amp's power equally between them. So it doesn't matter that one speaker was rated 30W and the other 15W--you'd nominally be pushing 10W into each. Not quite the "factor of 2" safety margin that Tung mentions, but you'd probably be OK--certainly much better than driving just the Blue by itself with the 20W head.

Keep in mind that if you run two speakers in a 2x12 cab, the resulting impedance will depend upon whether you wire them in series or in parallel. For example, two 8 ohm speakers in parallel have an impedance of 4 ohms, while in series, they'd be 16 ohms. Not a problem with the Rebel 20, since it has 4, 8 and 16 ohm output jacks.

 

[Weshunter]

is there any advantage to either series or parallel or an advantage to 4 or 16 ohms? i know the rebel will do 4, 8, or 16 ohms, but is that normal?

i figured i'd be safe with a 30 and a 15, but i wonder if it sound as good as 2 30's? seems like the 2 different wattage speakers could react very differently to the same amount of power.

 

[tunghaichuan]

is there any advantage to either series or parallel or an advantage to 4 or 16 ohms? i know the rebel will do 4, 8, or 16 ohms, but is that normal?

i figured i'd be safe with a 30 and a 15, but i wonder if it sound as good as 2 30's? seems like the 2 different wattage speakers could react very differently to the same amount of power.

The advantage to parallel wiring two (e.g., 8 ohm speakers in parallel,) is that if one of the speakers burns out (which is a real possibility when using a lower wattage handling speaker with a higher wattage handling one), you still have a speaker load attached. With speakers in series, if one blows, then you have an open circuit which can damage the amp's output transformer. With a tube amp you always want a speaker load attached to the output.

I'm not a big fan of speaker distortion (putting too much power into the speaker to get it to distort). The deciding factor in driving speakers is how senstive they are. In fact some high wattage speakers are very sensitive and will actually put out louder SPLs than some lower power rated speakers.

 

[duhvoodooman]

i figured i'd be safe with a 30 and a 15, but i wonder if it sound as good as 2 30's? seems like the 2 different wattage speakers could react very differently to the same amount of power.

The wattage rating really isn't the issue. What you want to match up is the impedance and keep the efficiency ratings of the two speakers close. For example, I have a 2x12 cab that contains an Eminence Redcoat Wizard (75W, 103 dB) and a WGS Green Beret (25W, 99 dB), and it sounds great.

 

[Weshunter]

how do you find efficiency ratings?

 

[tunghaichuan]

how do you find efficiency ratings?

Try the manufacturer's web site. The efficiency rating is expressed in dB/watt/meter. So a speaker with 103 efficiency rating will produce 103 deciBels when measured one meter away with one watt driving it. Note that the efficiency rating is independent of the power handling. Two speakers of the same efficiency will produce the same spl. So a low-powered 5W amp should be able to drive either speaker equally well. However, speakers with higher power handling capabilities will be able to take more power without burning out.

 

[Weshunter]

thanks so much, man, this is really great stuff to have learned. can't believe i made it this long without destroying any gear without looking into this stuff, guess it's cause i've always had combo amps and never changed out speakers before. anyway, this is great. thanks. now i just need to pick which 12 in speakers to put in the 2x12 cabinet i'm going to build.