Power amp recommendation for 1x12 cab?

[gr.788]

Hello, i'm new to these things, does anyone know if my understanding of power amp and cabinet matching is correct?

"When you’re matching a power amp to a PA speaker setup, a good rule is to pick an amplifier that can deliver power output equal to twice the speaker’s continuous rating. So, a speaker with a nominal impedance of 8 ohms and a continuous power rating of 350 watts will require an amplifier that can produce 700 watts into an 8-ohm load"

I want to buy a cabinet that it's listed power rating is 60W and it's impedance is 16ohm, so a matching power amp have to output a wattage of minimum 60w to 120w per channel right? and should be rated to handle a speaker impedance of 16ohm.
However i rarely find power amps that are rated to handle 16ohm, and if they do, often have a high wattage like the seymour duncan power stage 200.
If someone can recommend me a power amp suitable for this cab with a good price-quality ratio i'd grealty appreciated it, thanks.

 

[fantom]

IIRC the age old advice was the other way around. You want a speaker cab that can handle the output of the power amp so the power amp doesn't rip apart the speaker.

When I looked into it, I repeatedly saw the rating of the cab should be 1.5 the power amp. So a 60W cab should probably have a 40W power amp. But I didn't see any logical reason why.

So I reached out to the manufacturer of my 75W 1x12. They literally told me it doesn't matter. Just match the impedance and don't crank a 100W-200W amp into it. If you see the speaker unable to handle the vibration, lower the volume.

That makes way more sense to me, as the rating is about the physical ability for the speakers to handle the vibrations. The master volume is sending a bunch of energy to ground unless you crank it.

I ran 50W and 100W power amps into that 1x12 with no issues since then.

So if you want to be safe and play loud, buy something 25-50W so you don't accidentally ruin the speaker. If you are just playing bedroom levels, it doesn't matter at all.

 

[Christopher Har V]

IIRC the age old advice was the other way around. You want a speaker cab that can handle the output of the power amp so the power amp doesn't rip apart the speaker.

When I looked into it, I repeatedly saw the rating of the cab should be 1.5 the power amp. So a 60W cab should probably have a 40W power amp. But I didn't see any logical reason why.

So I reached out to the manufacturer of my 75W 1x12. They literally told me it doesn't matter. Just match the impedance and don't crank a 100W-200W amp into it. If you see the speaker unable to handle the vibration, lower the volume.

That makes way more sense to me, as the rating is about the physical ability for the speakers to handle the vibrations. The master volume is sending a bunch of energy to ground unless you crank it.

I ran 50W and 100W power amps into that 1x12 with no issues since then.

So if you want to be safe and play loud, buy something 25-50W so you don't accidentally ruin the speaker. If you are just playing bedroom levels, it doesn't matter at all.

I've heard that the OP is correct in that the amp should have a higher power rating than the speaker, but then you just don't crank the amp all the way. Bc if you have it the other way around, a speaker with a higher power rating than the amp, then the amp has to work it's hardest all the time to deliver what the speaker wants, and that can make the amp prone to blowing out. That's just what I've heard, idk how this stuff actually works. Both explanations make sense.

 

[Baelzebeard]

The way OP portrayed is for use with solid state amps for PA applications (or similar). In a PA you do NOT want the amps to clip/distort. Firstly, it sounds like shit. Secondly the clipped, distorted signal is a nasty powerful square wave that can be momentarily much higher wattage than the amp specs would indicate. This can blow speakers, especially HF drivers real fast.

You really want the amp to have clean headroom. You just have to listen for speaker stress to control your volume.

I suppose solid state guitar amps should be approached in a similar manner.

 

[gr.788]

thank you all for yout input, at the end i decided to buy a combo amplifier, since its a cheapiest and a more beginner friendly option, the last thing i want is to buy something with my limited budget and mess it up.

 

[fantom]

I've heard that the OP is correct in that the amp should have a higher power rating than the speaker, but then you just don't crank the amp all the way. Bc if you have it the other way around, a speaker with a higher power rating than the amp, then the amp has to work it's hardest all the time to deliver what the speaker wants, and that can make the amp prone to blowing out. That's just what I've heard, idk how this stuff actually works. Both explanations make sense.

If you run a 100W amp into a Vintage 30 4x12, you have 100W amp head and 240W cabinet. That's 2.5x. Even a Herbert or Triple Rectifier running into a 4x12 is going to be minimum cabinet load 1.3x-1.5x higher than the head. And that's assuming a 60W speaker. Some speakers are rated higher.

I get what you are saying about clean headroom, but are we talking PA or guitar amps?

 

[gnoll]

Ha, imagine having a 4x12 with Celestion Redbacks or something and needing a 600W tube amp

 

[TedEH]

They literally told me it doesn't matter. Just match the impedance and don't crank

This is, IMO, the only answer that matters here. All the hypothetical scenarios of some kind of harm assume that you're pushing the limits of one of the pieces of gear. If you overshoot what you need on both sides of the equation, then it doesn't matter. If you've undershot your needs, the the problem is not that you have a mismatch, it's that you've undershot your needs.

(With the exception of impedance - match your impedance as much as possible, so that you're not shooting yourself in the foot re: undershooting your needs.)

I've used a 25w head into a 240w cab. It was fine. I've used a 1100w head into a 90w cab. It was also fine. An amp will only put out as much power as you ask it to, and a cab will only explode if you push it past its physical limits.

 

[wheresthefbomb]

"don't crank your amp" is no way to live.

 

[TedEH]

"don't crank your amp" is no way to live.

Your speakers may beg to differ.

 

[wheresthefbomb]

Your speakers may beg to differ.

I've been cranking big amps for well over a decade and the only speaker I've ever blown out was an old, middling Altec Lansing in a SUNN cab and I chalk that up to mediocre manufacturing and old age.

I generally am pushing less or equivalent wattage to what the speakers are rated for, but the band SUNN uses low wattage speakers, and their rigs get far more abuse in terms of power handling than mine and probably most other people's.

The cabs I have now all have quality speakers in them and I crank them without hesitation. If they couldn't handle that I'd consider it a design flaw.

 

[TedEH]

I may be biased as a bassist who is cursed to having to deal with blown speakers. Point being, the speakers will protest before they die, so it should not be a shock to anyone.

 

[Drew]

When I looked into it, I repeatedly saw the rating of the cab should be 1.5 the power amp. So a 60W cab should probably have a 40W power amp. But I didn't see any logical reason why.

So I reached out to the manufacturer of my 75W 1x12. They literally told me it doesn't matter. Just match the impedance and don't crank a 100W-200W amp into it. If you see the speaker unable to handle the vibration, lower the volume.

tl;dr - a 75w amp may actually peak well above 75w. You can safely run a 100w amp into a cab that's rated for 75w, but you don't want to turn up the amp much if you do. I've never heard this 1.5x cab to amp wattage rule, but especially for tube amps I'd probably want a cab that can handle double the wattage of the amp, if not more.

Longer version - wattage isn't as simple as maybe the way guitarists talk about it would lead you to think. Yes, it's a measure of the output power of an amp... but look closely at how it's quoted - generally, it's measured at a certain percentage total harmonic distortion (THD) - something like 100w at 0.05% THD or something. There's a standard here and I'm afraid I don't remember it, but basically wattage is generally quoted as as loud as a poweramp will get before it perceptibly begins to break up.

You can see where I'm going here, I'm sure... but, a tube power amp, the whole POINT of the design is that it sounds good when it breaks up. So an amp tat has 100w of clean power, probably has way more power once it begins to overdrive and break up a little, and if you hook it up to a speaker cab that can handle 100w of power, you're going to be absolutely overloading the shit out of that cab.

This, incidentally, is also why everyone says "tube amps are louder than solid state amps." On one hand, they're not - if a 100w solid state amp and100w tube amp are turned up to the same total THD, they would be about the same volume. It's just, the 100w tube amp is designed to also be able to be turned up way louder than that, because tube poweramp distortion sounds great, while the solid state amp is not, because solid state poweramp distortion sounds awful.

so, again, in summary... quietly, you don't have to worry about power mismatches between a head and a cab much at all, as it rarely becomes an issue at bedroom volumes. At performing/stage volumes, you probably want at least double the wattage of your tube poweramp in your speaker cab. More wouldn't hurt.

 

[TedEH]

Kind of tangential, but I've been wondering about the effect of the availability of wattage - I'm not sure how to phrase this, but picture it this way:

I've been using a PowerStage 200 for a while. It's 200w (at that 0.05 THD, etc etc), and plenty loud. The "usable" part of the volume knob is usually between 10-oclock and 2-oclock. Less than 10 and you normally aren't pumping out enough volume. More than 2, and you start to get output clipping (if you've staged the input to be pretty hot). This is about as loud as it gets. You can go louder, of course, but you're at risk of clipping.

Then I tried the PowerStage 700. Same input. Same cab. Is it louder? Kind of. But what surprises me is that the volume knob sort of "feels" the same as the 200. That is to say that I expected a much quicker onset of usable volume, but that didn't happen. It still takes until about 10-oclock to be loud enough for jams, but at that point it ramps up a bit faster. I've not pushed this one much, because I don't want to explode my poor 1x12, but it leads me to thinking of the relationship between wattage and "cranking it".

I've got two kinda related thoughts at play -
One is knowing that loudness and watts aren't related in some linear way. Colloquially you need something like a 10x increase in watts to perceive a doubling in volume. The other is that I assume the volume knobs on something like this are also not linear - they're probably "audio" taper pots, which would explain my 10-and-2 positions on the knobs, below the midpoint you need a lot of movement to produce more watts, and above the midpoint you're ramping up much faster. But what it also means is that your wattage is not linearly associated with your volume knob positions.

If these are log pots, or something close to it, you're actually looking at the midpoints for each being more like 50w and 175w, not the 100 and 350 you might assume. Actually, that would be more like 25w and 87w because I'm using an 8ohm cab, so we're cutting that power in half.

You'd also have to consider that these are probably rated with a sin wave probably staged into the input or something - a guitar is not a constant signal, and you're not likely maxing out the headroom of the input unless you've gain staged things so meticulously - so all of those numbers are, I think, maximums that you'd expect to approach. I know that with my setup, I still have some input headroom, so the real numbers would be lower again.

Ok, so where am I going with this..... I'm mostly thinking out loud to myself, but also -
The question was about matching watts to speakers, and if you can blow up a speaker with too many solid-state watts or something. And I think this all points to: no - you won't blow up your speakers because it's very unlikely (with a solid state amp) that you're actually putting out anything close to what the rating says, and there's so many things reducing the actual number if you're not pushing it. I have what's rated at "700w" going into a 1x12 at 8ohm that is rated as a 90w speaker. But 50% on the volume knob is punishingly loud, and between the knob taper and the impedance mismatch, I'm still undershooting that 90w by a fair bit before the cab gets so loud that other band members will start yelling at me.

.....I think?

 

[JSKrev]

I also have a Power Stage 700. I run the preamp level about 9 o'clock to keep from triggering the O.C. light. This results in me having to run the volume about 1-2 o'clock for rehearsal volume.

 

[Kosthrash]

How loud will your rig be greatly depends on an underrated parameter: your speaker's sensitivity.

 

[Crungy]

I may be biased as a bassist who is cursed to having to deal with blown speakers. Point being, the speakers will protest before they die, so it should not be a shock to anyone.

I agree it's a different ball game with bass speakers VS guitar.

I popped all four 10's in an Aguilar GS410 back in the day, using a Fulltone Bassdrive and accidentally switching to the clean boost. Split second mistake that cost me $500 in speakers

 

[TedEH]

I also have a Power Stage 700. I run the preamp level about 9 o'clock to keep from triggering the O.C. light.

I kinda wish the 700 and 170 had the same lights as the 200, because they don't tell you anything about your staging, and the manual is so light on info. I assume OC is overcurrent. But the 200 has an input and output clipping light. With the 200, I can set the FM3 to Line -10, crank the volume to full, and not clip the input. The +4 setting does clip the input unless I back the volume up. Judging by ear, the volume difference wasn't enough to warrant having to guess, so I leave it at 100% volume on the -10 setting.

But does the 700 use the same input? Probably. But who knows. It's not documented. The ICEPower modules they're based on document what they're expecting, but there's something else in between on the PS, changing the level before it gets there. Would it be more efficient to maybe use the +4 output and use some kind of global out gain reduction or something to stage it so that it's below clipping but higher than the -10 output? I have no idea.

Am I overthinking it? Very probably.

 

[JSKrev]

I kinda wish the 700 and 170 had the same lights as the 200, because they don't tell you anything about your staging, and the manual is so light on info. I assume OC is overcurrent. But the 200 has an input and output clipping light. With the 200, I can set the FM3 to Line -10, crank the volume to full, and not clip the input. The +4 setting does clip the input unless I back the volume up. Judging by ear, the volume difference wasn't enough to warrant having to guess, so I leave it at 100% volume on the -10 setting.

But does the 700 use the same input? Probably. But who knows. It's not documented. The ICEPower modules they're based on document what they're expecting, but there's something else in between on the PS, changing the level before it gets there. Would it be more efficient to maybe use the +4 output and use some kind of global out gain reduction or something to stage it so that it's below clipping but higher than the -10 output? I have no idea.

Am I overthinking it? Very probably.

I'm pretty new to using a dedicated power amp. Duncan tech support told me having the OC light blinking occasionally is fine, but solid-on will likely cause thermal shutdown. My takeaway from talking to them was "use my ears."

 

[Christopher Har V]

If you run a 100W amp into a Vintage 30 4x12, you have 100W amp head and 240W cabinet. That's 2.5x. Even a Herbert or Triple Rectifier running into a 4x12 is going to be minimum cabinet load 1.3x-1.5x higher than the head. And that's assuming a 60W speaker. Some speakers are rated higher.

I get what you are saying about clean headroom, but are we talking PA or guitar amps?

Now that I think about it, what I was touching on there was what car audio guys were saying about amps, speakers, and headroom on the amp. All I know is my Mesa Boogie JP-2C into my Orange 2x12 works fine.