20/20 Output Wattage and Speaker Selection

[btvguitar]

Hi there; this is my first post. I recently purchased a 20/20 because my old rig was just way too much for the practice space and the small clubs (100-ish folks) we play at, plus it weighed too much. I'm looking to downsize my cabinet from my current 4x12 to a 2x12, which I will have wired stereo at 8 ohms per speaker. I've been looking to put either Celestion Blues or Golds into this cab and here's my conundrum:

The blues are rated at 15 W and the golds are rated at 50 W. If the 20/20 put out say, 10-15 Watts per channel, I would just go with the blues. If it put out, say, 30-40 Watts per channel, I would go with the golds. At 20 W per channel, I'm torn. Ideally you want to push these speakers hard, but not too hard, and you don't want to substantially "under drive" them either. I'm playing with the 20/20's volume knobs at between 11:00 and Noon. Am I better going with the blues or the golds? What say folks here?

 

[screamingdaisy]

It's hard to say. The "Dyna-Watt" part of the 20/20 is a stiffening capacitor that stores energy to beef up the EL84s and provide more power when needed to reinforce low notes, which to me would put the amp up at the high end of 20w, if not slightly higher.

(for instance, the LSS is also Dyna-Watt and it produces 35w instead of 30w)

 

[RectoStudioGuy]

It's hard to say. The "Dyna-Watt" part of the 20/20 is a stiffening capacitor that stores energy to beef up the EL84s and provide more power when needed to reinforce low notes, which to me would put the amp up at the high end of 20w, if not slightly higher.

(for instance, the LSS is also Dyna-Watt and it produces 35w instead of 30w)

Agreed, but is your best utilization of the 20/20 full up? I find it responds well at no greater than about 1:30 so therefore slightly less than full power.

 

[screamingdaisy]

Agreed, but is your best utilization of the 20/20 full up? I find it responds well at no greater than about 1:30 so therefore slightly less than full power.

I haven't used the 20/20, just pointing out the Dyna-Watt part.

The thing about tube power is that they can be outputting maximum power early on in the pots taper and turning it up past that point simply increases saturation/overdrive. Chances are that if you're finding it performs well up to 1:30 it entered into overdrive well before that point.

The only way to know for sure is to measure it. $300/speaker is a lot...

 

[RectoStudioGuy]

Agreed, but is your best utilization of the 20/20 full up? I find it responds well at no greater than about 1:30 so therefore slightly less than full power.

Chances are that if you're finding it performs well up to 1:30 it entered into overdrive well before that point.

Absolutely! Between 11:30-12 it hit's a really sweet spot for all of the clean dirt it was designed for.

 

[allphourus]

Speakers are really a matter of Personal Taste aren't they? It would rest upon what type of tone your going for. These speakers have entirely different response characteristics. General rule of thumb is the Lower the power rating a spkr has( less efficient ) = earlier power amp output tube breakup and more speaker generated distortion component, The higher rated the speaker is ( The more efficient ) = More clean headroom from the power amp more punch and clarity from the speaker. Magnet material also effects tone and spkr response too. I think (?) the Blues are alnico and the golds are ceramic. Again this is just a general guide and vary much a subjective thing, ceramic think modern marshal 1960 cab type tone, alnico vintage tweed fender break up.

It all depends on what kind of tone your trying to go for.

Personally I favor high efficiency speakers, JBL's, Gauss, and EV's that for a given amp output ( watts ) produce a higher Sound Pressure Level ( SPL ). They move more air per watt. Watts are not a audio measurement of moving air molecules but an electrical measurement of electrons moving on a wire Analogous to water Flow rate through a hose (How much per hour). To clarify I do not mean to confuse power handling capability (which is how much power the speaker can safely handle without frying itself ) with efficiency ( how well the spkr converts electrical energy into sound waves and how much is wasted as heat), they are two different things. Voice coil generated heat destroys spkrs.

For me with Boogie High gain type preamp generated distortion and high head head room power amps that are ridiculously hard to drive into breakup at reasonable levels, higher efficiency spkrs seem to work best. Just my preference, opinions very. For low power amps under 30 watts (the 20/20 is for all intents and purposes is a 40 watt amp) this reverses.

About Power output, on the 20/20 were the knobs point is not the point ( I agree with the sweet spot, note that the manual does not offer up any setting suggestions as it does for every other boogie unit I have ), Amps are measured to produce rated output at a given input, It would than depend on what preamp your driving it with, how you have the gain structure set up, what pedals if any your hitting the preamp with, with the right combination of pedals, preamp high gain setting could be producing rated output with output tube clipping ( and even PI distortion ) at the volume control set barely on on the 20/20 ( just to be extremely absurd ) Vrs. Not enough signal from preamp, 20/20 dimed tone like a transistor radio from the sixties . A clue I've learned to watch for is hiss/noise, volume to low hiss, to high hiss, just right best tone and responsiveness lowest hiss. Hiss = mismatch, Use your ears . Balance Preamp master/output and 20/20 input controls, setting them both about the same works best for me. Gain structure is everything.

Note: Open back or sealed enclosure will make a big difference in tone/responsiveness too.

All that said My personal choice would be the The Golds ,

I have a four ten cab with 2 fender Jensen alnico blues and 2 ceramic Celestions that I use with both my TA-15 and my 20/20 with spkrs split into stereo inputs . Works extremely well for me. I'm looking for a suitable 2 ten cab, I'll probably load with Heritage 10's and two single ten cabs, open back with alnicos of some sort maybe Weber blue dogs. Ideally I'd like convertible cabs that can be both open and closed back. I then think I would the have the best of all worlds.

 

[elvis]

If you're worried about damaging the speakers, check into how much power they can really take. Many speakers can comfortably dissipate as much as 2X their rated power.

From the other side, an amp's rated power is based on a measurement in only one condition, usually at a fixed amount of THD (like 1%), or at flat-out for a tiny amount of time (this is how car audio gets a 30W continuous amp to give the 500W power that they print on the box, i.e peak music power).

For solid-state amps, distortion generally happens when the output hits the power supplies, so there is a hard-stop. You get pretty much the same power at 0.1% and 100% THD. For tube amps, the tubes saturate early, and can often produce more and more power as the distortion increases. So it may be 15W at 1% THD, and 40W at 100% THD. The input frequency response, amplifier design, etc all affect the actual power output.

Rated power is by no means a MAXIMUM power spec. Note: if you run two speakers, either in parallel or series, each takes only HALF of the amp's power output. Four speakers each take 1/4.

Also, music itself tends to be very low duty-cycle. This means that unless you are clipping the heck out of your source, you almost never get peak power from the amp, and you only get it for a very short amount of time.

These are some of the reasons that a 100W head into a 4x12 loaded with 15W speakers is not always a disaster.