Double Bass amp wattage - does it need to be higher than the cabinet's?

[drurb]

So it is still over powering that damages the speaker, not square waves

More absurdity. No one I know of ever made the ridiculous argument that square-waves, per se, are what damage speakers. One could, of course, safely play a low-level square wave through a speaker and be just fine. Once again, when an amplifier clips at high output over a sustained period, the waveform becomes like a square-wave. The spectral consequences of squaring off the wave at what is essentially full power output for the amp are that energy is spread to high frequencies (time-domain/frequency-domain duality). That massive energy at high frequencies is what fries a tweeter. Yes, it's overpowered. That's what I explained from the beginning. The clipping and spectral spread are how the tweeter becomes overdriven.

Suppose you put a 500-Hz tone through your 400-watt amp at near full power. Given typical crossovers, the tweeter receives almost no energy. Now, drive the amp into hard, sustained clipping. There will suddenly be huge amounts of sustained high-frequency energy that would fry the typical tweeter in a typical cab rated at, say, a few hundred watts. Yes, the tweeter is overdriven because a square wave, and thus high frequencies, were generated at high power. The tweeter doesn't fry because it's a square-wave, per se. That's silly. It fries because it is hit with high-frequency energy that, as a direct consequence of clipping, exceeds its power-handling capability.

Maybe reading this again will help you and brendanbassist.

Yeesh!

 

[Hopkins]

More absurdity. No one I know of ever made the ridiculous argument that square-waves, per se, are what damage speakers. One could, of course, safely play a low-level square wave through a speaker and be just fine. Once again, when an amplifier clips at high output over a sustained period, the waveform becomes like a square-wave. The spectral consequences of squaring off the wave at what is essentially full power output for the amp are that energy is spread to high frequencies (time-domain/frequency-domain duality). That massive energy at high frequencies is what fries a tweeter. Yes, it's overpowered. That's what I explained from the beginning. The clipping and spectral spread are how the tweeter becomes overdriven.

Suppose you put a 500-Hz tone through your 400-watt amp at near full power. Given typical crossovers, the tweeter receives almost no energy. Now, drive the amp into hard, sustained clipping. There will suddenly be huge amounts of sustained high-frequency energy that would fry the typical tweeter in a typical cab rated at, say, a few hundred watts. Yes, the tweeter is overdriven because a square wave, and thus high frequencies, were generated at high power. The tweeter doesn't fry because it's a square-wave, per se. That's silly. It fries because it is hit with high-frequency energy that, as a direct consequence of clipping, exceeds its power-handling capability.

Maybe reading this again will help you and brendanbassist.

Yeesh!

So explain to me how it is different than using a very dirty fuzz through a higher powered amp. Is the square-wave not acting upon the cross over in the same way as the lower powered amp clipping? But anyway, what the hell are we arguing about, if we both agree that speakers are only damaged by being over powered. And none of this matters in a real world application, because if you push your amp to that point of clipping it is going to sound horrible. In a real world application, matching the wattage rating of a cab to the output power of an amp is not that important.

 

[drurb]

So explain to me how it is different than using a very dirty fuzz through a higher powered amp. Is the square-wave not acting upon the cross over in the same way as the lower powered amp clipping? But anyway, what the hell are we arguing about, if we both agree that speakers are only damaged by being over powered. And none of this matters in a real world application, because if you push your amp to that point of clipping it is going to sound horrible. In a real world application, matching the wattage rating of a cab to the output power of an amp is not that important.

It is not different. Play a highly distorted signal containing a great deal of high-frequency content at high power and you risk burning a tweeter as well. Take my example above of the 500-Hz tone and the 400-watt amp that is pushed into clipping such that a tweeter is blown. Under those very same conditions, if one had been using an 800-watt amp, it would not clip so only the 500-Hz tone would be transduced and the tweeter would not be blown. This is what people mean when they refer to an amp being under-powered. They do not mean that the amp has too little power for the speaker. They mean it has too little power for the conditions under which it is used.

For decades, people have pointed out how using such an "under-powered" amp leads to clipping which leads to the generation of high-frequency content, which leads to damage. That's correct. It's a fact. It's undeniable.

What's amazing to me is that people have misinterpreted this to mean that clipping, per se, or high-frequency content, per se is what damages speakers and so they write misguided internet articles about it. One can show in trivial ways this is not true. I've mentioned them here. One can play a square wave at low power through a typical cab with a tweeter. No problem. One can build a 2-watt amp and make it clip and play it through a typical cab. No problem. That's all beside the point.

Look-- one can say that ingesting cyanide is lethal. There's a context in which one says that. It's a true statement. Now, someone could come along and say. "Hey, if you ingest one billionth of an ounce of cyanide you won't die-- so it's not lethal." Well, of course!

Clipping, the squaring off of the waveform, and the concomitant spread of energy to high frequencies at high levels damages tweeters in situations under which the damage would not otherwise occur had a higher power amp been used. That's the context in which the statements about clipping and high-frequency content are made.

I suspect that when it comes right down to it, we agree.

 

[Ric Vice]

Just a side note. Most of the new "micro" heads have a built-in compressor limiter to avoid problems encountered when switchmode power amps are driven to clipping. Both of my amps do. (GK MB200 and EA Micro300). As a result, clipping these amps under normal conditions is unlikely.

+1 I remember a few discussions about this over on the BG side, and apparently this is fairly common practice now to get rid of infrasonic frequencies, that waste power.

But a different matter arises. In my experience, it's pretty annoying to be riding a compressor all night long when playing dynamically is so important to our craft. So, I would still consider sizing an amp so it's unlikely to be pushed to the limit at your typical volume levels.

My first professional amplifier was a Walter Woods MI-100-8 it sounded wonderful. My second professional amp was a Walter Woods MI-400-8 which has an identical pre amp with four times the RMS power rating. In a side by side comparison, driving the same speaker, the MI-400-8 sounds fuller even at the same volume level.

Ric

 

[drurb]

+1 I remember a few discussions about this over on the BG side, and apparently this is fairly common practice now to get rid of infrasonic frequencies, that waste power.

Ric--
A compressor won't get rid of infrasonics. As you know well, that's accomplished by a high-pass filter.

 

[teleharmonium]

Clipping, the squaring off of the waveform, and the concomitant spread of energy to high frequencies at high levels damages tweeters in situations under which the damage would not otherwise occur had a higher power amp been used. That's the context in which the statements about clipping and high-frequency content are made.

Ok, but - internet folklore about underpowering doesn't typically include the specific detail of the relatively fragile crossover/tweeter cabinet as opposed to speakers in general, and this context you describe is somewhat arbitrary. It's not a function of amp power nor the ratio of amp power to speaker power (and whether or not a tweeter is involved). User competence and attentiveness have to be in the equation too.

Clipping is the problem, and we're more clear if we put it that way.

Even if there is no tweeter and the speakers are many and very robust, we still don't want to do it with a solid state amp as a rule because it sounds bad. You could find other ways into a clipping situation, such as a player trying to make do with a relatively inefficient single driver and ending up pushing a larger power amp into clipping.

I encounter a lot more blown tweeters in bar PA systems than in bass amps. Rather than defining that problem as the PA power amp not being more highly powered, I prefer to define it as the sound guy making the shows too damn loud, not least because of their hearing damage. Because the power amp works fine and the speakers used to work fine and the master fader on the board was sitting right there as an unused solution.

I don't accept the user's perceived need to be so loud with that gear as a reasonable given that must be taken for granted.

 

[BrBss]

The OP's question was: "amp wattage - does it need to be higher than the cabinet's"? The answer is NO.

If the question was: "amp wattage - should it be high enough that I don't have to run it into clipping in order to get the volume I need?" Then Drub's posts would be valid. If I have a 500 watt cabinet, and am running a 400 watt amp into clipping, then getting a 700 watt amp so I don't have to clip is NOT the answer. I'm clipping the 400w amp because I don't have enough volume, so increasing amplifier power means I can send even more power to the cab- I can overpower the cabinet before the amp clips, plus there's nothing to stop me from clipping the 700 watt amp either. (A better plan is to keep the 400 watt amp and add another 500 watt cabinet, which is much more effective at increasing volume than adding amplifier power.)

If I have a magic speaker that can handle 10 billion watts, there's no reason why I need a 12 billion watt amp, which is what is implied when we talk about "underpowering" (Drub, I know you didn't say I would need a 12 billion watt amp- I'm just clearing that up for anyone who might be confused.) If the speaker can handle enough power, it doesn't matter if the amp is clipping; the cab can take it. If the speaker has too low of power handling, then it can get blown by an amp that isn't clipping. So the issue is NOT about having "amp wattage ... higher than the cabinet's". It's about having enough speakers with enough sensitivity, xmax, and thermal power ratings, and an amp with enough power to drive those speakers. That way none of your gear is being pushed to the max. The safest bet is to have a cab rated higher than the amp (Note that amps can put out more power than their ratings and cabs may not be able to handle power that they are rated for, so having a cabinet rated higher than the amp isn't a guarantee for safe gear. And note than more powerful amps can always be turned down, so cabs don't have to be rated higher than the amp to be safe.)

But when it all comes down to it, you will hear speakers reaching their excursion limits and you will hear an amp being driven to clipping. So use your ears, and don't ask too much of your gear. (Unless you want to drive your power amp into clipping for that overdriven tone... probably with a tube amp. Then you'll want to make sure you have a cabinet rated to handle more power than your amp can put out, certainly not less.)

 

[drurb]

...and this context you describe is somewhat arbitrary.

Except for this statement, we seem to agree.

The OP's question was: "amp wattage - does it need to be higher than the cabinet's"? The answer is NO.

Need? No, it doesn't. I explained so much more about it though.

If the question was: "amp wattage - should it be high enough that I don't have to run it into clipping in order to get the volume I need?" Then Drub's posts would be valid.

Yes, they would be valid and they still are.

If I have a 500 watt cabinet, and am running a 400 watt amp into clipping, then getting a 700 watt amp so I don't have to clip is NOT the answer. I'm clipping the 400w amp because I don't have enough volume, so increasing amplifier power means I can send even more power to the cab

A very limited view. A more powerful amp can send more clean power to the cab well before blowing the tweeter under the conditions it was blown with the amp of lesser power.

I can overpower the cabinet before the amp clips, plus there's nothing to stop me from clipping the 700 watt amp either. (A better plan is to keep the 400 watt amp and add another 500 watt cabinet, which is much more effective at increasing volume than adding amplifier power.)

Well, yes, one can always add more and bigger cabs and more and bigger amps. That really doesn't help to educate as to what are the issues.

If I have a magic speaker that can handle 10 billion watts, there's no reason why I need a 12 billion watt amp, which is what is implied when we talk about "underpowering"

No, it is not! This is decidedly NOT what is meant by underpowering. I explained in detail in post #43. Read what I wrote. You are misinterpreting and trivializing.

(Drub, I know you didn't say I would need a 12 billion watt amp- I'm just clearing that up for anyone who might be confused.)

Clearing it up? Well, you've muddied it up.

If the speaker can handle enough power, it doesn't matter if the amp is clipping; the cab can take it.

Trivially true. The point is that when considering practical specs and practical situations, running an amp into clipping can damage a tweeter. In fact, I gave the very example you just repeated in post #43. Specifically, that of a two-watt amp driven into clipping.

If the speaker has too low of power handling, then it can get blown by an amp that isn't clipping.

Of course, and trivially true.

So the issue is NOT about having "amp wattage ... higher than the cabinet's".

No, not in the trivial sense. The issue is that someone has a cab. Now, what should be the power rating of the amp? There is no simple rule. As I said earlier, one has to think intelligently. Still, however, given one has a cab, one would do better to have a more powerful than a less powerful amp. No, not an amp with a billion watts that will blow the speaker sky high. That, by the way would be fine if the speaker were fused-- another suggestion that I made.

It's about having enough speakers with enough sensitivity, xmax, and thermal power ratings, and an amp with enough power to drive those speakers. That way none of your gear is being pushed to the max.

Yes, indeed! You got one right.

The safest bet is to have a cab rated higher than the amp

Given one has an amp, then sure, buying a bigger cab is always a plus but often impractical. You see, it is you who is not paying attention to the OP's question, which started this way:

I've heard this before when buying a 350 watt cabinet -

Notice that the cabinet came first. Now, what amp should he buy. My advice is to go high. That's good advice. Now, I wouldn't twist your logic as you have twisted mine and suggest that you are saying that he should, necessarily, buy a lower power amp. What you persist in doing is inappropriately extrapolating from and simplifying what I am saying such that you end up with silly and/or nonsensical "rules" that you then challenge.

But when it all comes down to it, you will hear speakers reaching their excursion limits and you will hear an amp being driven to clipping.

Often, however, you will blow a tweeter or run into thermal overload before you can even react to the sound of the amp clipping. That's the danger.

So use your ears, and don't ask too much of your gear. (Unless you want to drive your power amp into clipping for that overdriven tone... probably with a tube amp. Then you'll want to make sure you have a cabinet rated to handle more power than your amp can put out, certainly not less.)

Now you're being dogmatic rather than considering the parameters that we both have identified. There is nothing wrong and very much right about having an amp that is rated well above the rating of the cab, especially if you are using your ears to give you fair warning. The woofer will typically complain in time for you to back down the gain. If clipping is present, you may not have that warning.

 

[Hopkins]

\As I said earlier, one has to think intelligently. Still, however, given one has a cab, one would do better to have a more powerful than a less powerful amp.

Not always, I realize that this is the double bass side of TB and this is probably not true for playing through a DB. But I purposely chose a GK 700rbII over the 1001rb because I can drive it harder to get that GK grit out of it at a much lower stage volume than the 1001rb. I have never had any tweeter issues, and never will because I never use the tweeters in my cabs.

 

[drurb]

Not always, I realize that this is the double bass side of TB and this is probably not true for playing through a DB. But I purposely chose a GK 700rbII over the 1001rb because I can drive it harder to get that GK grit out of it at a much lower stage volume than the 1001rb. I have never had any tweeter issues, and never will because I never use the tweeters in my cabs.

If you don't have tweeters, then you tend not to have tweeter issues. I was speaking from the viewpoint of it being desirable not to overdrive an amp.

 

[drurb]

Thinking about what's gone on in this thread, it strikes me that one of the problems that misleads folks is the statement of simple rules of thumb. I've been careful not to state any.

It is neither true nor helpful to say that the power-rating of an amp should be greater than, less than, or equal to the power-rating of a cab. Let's put aside the validity of those ratings for now.

Good reasons have been stated here by those posting for, under different circumstances, the desirability of ending up with an amp with a power-rating greater than that of the cab to which it's mated and the desirability of ending up with an amp with a power-rating that is less than that of the cab to which it's mated. No simple rule covers these circumstances.

As I've posted here many times before, "Think SPL, not watts." I encourage anyone interested to do a search within this forum on that phrase. Some rather enlightening discussion developed.

The optimum choice of the relative power-ratings of an amp and cabinet really stem from a consideration of the sound-pressure level one wishes to achieve, the sensitivity of the cab, and from where one begins in the choice of equipment. I'll assume for the purposes of what follows, that what's desired is clean power and not intentional distortion. That's true for the vast majority of DB players.

Now, suppose one starts with a cabinet rated at 350 watts as the OP of this thread did. What should be the power-rating of the amp that he buys? The first consideration should be the sensitivity of the cab in terms of SPL @ 1meter/watts. (These measures are usually made at 1 kHz so, yes, they may be of limited use, but let's roll with it). Keep in mind that every doubling of watts corresponds to 3 dB and every tenfold increase corresponds to 10 dB. Suppose Cab A is rated at 350 watts and has a sensitivity of 100 dB SPL/watt @ 1 meter. Now suppose Cab B also has a rating of 350 watts but has a sensitivity 90 dB SPL/watt @1 meter. Those are actually realistic values. They are 10 dB apart, meaning that, all other things being equal (e.g., frequency response, excursion limits, etc.), 10x the power will be required to reach a given SPL with Cab B as compared to Cab A. That's right. What a 10-watt amp will do with Cab A will require a 100-watt amp for Cab B. What a 100-watt amp will do with Cab A will a require a 1000-watt amp for Cab B.

Let's take a look at using the 100-, 100- and 1000-watt amps. If we want to generate 110 dB SPL @1 meter, we can do that just fine with Cab A. Just hit it with 10 watts. We'd have to hit Cab B with 100 watts to do that. If we want to generate 120 dB SPL @ 1 meter, we just apply 100 watts to Cab A. No problem, we're well within spec. To do that with Cab B, we'd need 1000 watts. Oops! We'd have smoked it!

With an extremely sensitive cab, one needs less amplifier power. Usually, such cabs are of designs that they can also handle reasonable amounts of power. Take an example from the hi-fi world. A Klispchorn is rated at 106 dB SPL/1 watt @ 1 meter. For decades, people have been running them with low-power amps and done just fine. Still, although they can absorb hundreds of watts and create ear-shattering levels of musical content easily, the poor horn-loaded tweeters were somewhat sensitive and, in fact, were damaged by running moderately-powered amps into clipping. This led the company to develop a special protection circuit.

So, for someone using those systems and wishing only to generate moderate-to-quite loud levels, a low powered amp would do fine. For those wishing to create higher levels, it was important not to drive the amp into clipping. No simple rule would do.

Getting back to musical sound reinforcement, typical equipment, and the OP, if one starts with a typical cab rated at 350 watts, the choice of an amp really should take into account a number of factors. Given that one already has chosen such a cab and given the sensitivity of typical musical instrumental cabs with such ratings and used for bass, I think it is typically much wiser to choose an amp rated higher than that of the cab rather than to choose an amp that has a power-rating so low that, if it clips, it won't do damage because the increased average power can be absorbed by the cab. The power would have to be so low as to make the rig not very useful. That's because a 350-watt rating is not all that high in the world in which we live. IMO, in such a case, it would be better to protect against clipping. Your ears will tell you if you're pushing the cab too hard under clean, non-clipped conditions. Is this a rule then that one should always choose an amp with a rating higher than that of the cab? Absolutely not!

As others have pointed out, if one starts with a particular amp, say one rated at 500-watts and knows in advance that conditions will be such that clipping will often occur then, yes, the best choice would be a cab that can absorb the abuse. Is this a rule then that one should always choose a cab with a rating higher than that of the amp? Absolutely not!

This is what I've meant by thinking intelligently about all of this. Simple rules about these things are folly. I think (hope) this is something about which we can all agree.

 

[Hopkins]

If you don't have tweeters, then you tend not to have tweeter issues. I was speaking from the viewpoint of it being desirable not to overdrive an amp.

I understand, I doubt you would want any kind of break up when playing DB through and amp. It is a different world than bass guitar.

 

[Ric Vice]

I understand, I doubt you would want any kind of break up when playing DB through and amp. It is a different world than bass guitar.

Perhaps this subject would be more appropriate on the Electric Bass forum. ;<)

Ric

 

[Hopkins]

Perhaps this subject would be more appropriate on the Electric Bass forum. ;<)

Ric

Until my second to last post in this thread, I had no idea that it was in the DB forum. This is the type of thread that is typical on the BG side.

 

[DukeLeJeune]

...it strikes me that one of the problems that misleads folks is the statement of simple rules of thumb...

...Simple rules about these things are folly.

Well stated and well established. This principle extends beyond the present discussion.

Granting undue authority to oversimplified rules and viewpoints has caused harm in many areas of human experience, not just amp vs cab wattage ratings. Most systems are complex (to varying degrees), and complex systems call for complex analysis and understanding if they are to be intelligently managed.

Imo, ime, ymmv, etc.

 

[fdeck]

Well stated and well established. This principle extends beyond the present discussion.

Granting undue authority to oversimplified rules and viewpoints has caused harm in many areas of human experience, not just amp vs cab wattage ratings. Most systems are complex (to varying degrees), and complex systems call for complex analysis and understanding if they are to be intelligently managed.

Imo, ime, ymmv, etc.

Complex analysis is why you need to consult an imaginary bassist.

 

[Major Softie]

Until my second to last post in this thread, I had no idea that it was in the DB forum. This is the type of thread that is typical on the BG side.

I've made that mistake myself, at least twice.

 

[drurb]

Complex analysis is why you need to consult an imaginary bassist.

Very nice! I'm awarding 1.5 points for that line.

 

[Steve Freides]

Not always, I realize that this is the double bass side of TB and this is probably not true for playing through a DB. But I purposely chose a GK 700rbII over the 1001rb because I can drive it harder to get that GK grit out of it at a much lower stage volume than the 1001rb.

In 2014 (and beyond), I choose to make any effect I'm going for, including "grit," happen before the signal gets to my amp, and then choose to have the cleanest, most powerful amp I can find and the cleanest, most robust speaker(s) I can find.

I just sleep better this way know that, because I play an acoustic instrument, I want it to be able to make my amplified sound as much like my acoustic sound as possible - a pipe dream, I realize, but a very valid goal nonetheless.

It's so easy to model "grit", "overdrive", and what have you these days - I know, it doesn't sound exactly the same, and it's not, but it's my choice, for what that's worth.

I have never had any tweeter issues, and never will because I never use the tweeters in my cabs.

I just love this.

-S-

 

[Hopkins]

In 2014 (and beyond), I choose to make any effect I'm going for, including "grit," happen before the signal gets to my amp, and then choose to have the cleanest, most powerful amp I can find and the cleanest, most robust speaker(s) I can find.

I just sleep better this way know that, because I play an acoustic instrument, I want it to be able to make my amplified sound as much like my acoustic sound as possible - a pipe dream, I realize, but a very valid goal nonetheless.

It's so easy to model "grit", "overdrive", and what have you these days - I know, it doesn't sound exactly the same, and it's not, but it's my choice, for what that's worth.



I just love this.

-S-

I would do the same thing if I were playing acoustic instruments. That being said, I still have plenty of clean head room on tap with my rig. I use it to play country as well.