Higher wattage amp or Cab?

[Old Garage-Bander]

But that is still over powering the speakers. It isnt that the amp is too low powered for the cab, it is still a case of too much power. Its not like a 25 watt amp is going to blow an 810 just because it is pushed in to clipping.

Yes! It is overpowering the speakers. But you and I understand how that can happen, where others may not.
Going just by the rated specifications of the equipment offers no guarantee of safe operation.
The power output rating for an amp is measured under a certain set of operating parameters.
The rated power handling capacity of the speakers are also measured under a certain set of operating parameters.
And the operating parameters used to rate the amp output, may not be the same as what is used to rate the cab's capacity.
If you operate the cab or the amp in a manner that is outside the test parameters used to rate power, which is just about all of the time, you may risk damage.
There are some people here who may not be aware of that.

If you read what I posted earlier. I believe the example I gave was a 75 watt amp and a 100 watt speaker.
I never said a 25 watt amp into an 8x10 cab.
If you are implying that I said anything other than 75 W amp /100 W cab, then you are twisting my words.
Also when I posted that, I made it very clear to all readers who paid attention to what I wrote, that I was only offering my opinion on the matter. I also allowed that other opinions may differ from mine and the the OP's mileage may vary. "YMMV."

You are entitled to your opinion and I respect your opinion even if it differs from mine.
As I hope is the case with the OP, I take into consideration all opinions, but then make my choices based on my willingness to experiment. Everyone who contributed to this conversation has given the OP plenty to think about. He must decide what to do with it.
I had not, at any point drawn a line in the sand and said that if you step over that line you will do damage to your speakers.
Nor did I say that staying on this side of the line, will in all cases prevent damage.

Please also note that by quoting my previous post you are not disagreeing with me.
Rather you are disagreeing with the person that I quoted.
I added no new information about the topic in my previous post. I simply thanked Agedhorse for his comments on the matter.
I then threw in a little explanation about how my brain may be wired in such a way that I sometimes have difficulty, explaining my thoughts so that others can understand. I even suggested that it might be best for all, if I don't try to explain things for others.
I hope you don't have a problem with any of that?

 

[CL400Peavey]

Yes! It is overpowering the speakers. But you and I understand how that can happen, where others may not.
Going just by the rated specifications of the equipment offers no guarantee of safe operation.
The power output rating for an amp is measured under a certain set of operating parameters.
The rated power handling capacity of the speakers are also measured under a certain set of operating parameters.
And the operating parameters used to rate the amp output, may not be the same as what is used to rate the cab's capacity.
If you operate the cab or the amp in a manner that is outside the test parameters used to rate power, which is just about all of the time, you may risk damage.
There are some people here who may not be aware of that.

If you read what I posted earlier. I believe the example I gave was a 75 watt amp and a 100 watt speaker.
I never said a 25 watt amp into an 8x10 cab.
If you are implying that I said anything other than 75 W amp /100 W cab, then you are twisting my words.
Also when I posted that, I made it very clear to all readers who paid attention to what I wrote, that I was only offering my opinion on the matter. I also allowed that other opinions may differ from mine and the the OP's mileage may vary. "YMMV."

You are entitled to your opinion and I respect your opinion even if it differs from mine.
As I hope is the case with the OP, I take into consideration all opinions, but then make my choices based on my willingness to experiment. Everyone who contributed to this conversation has given the OP plenty to think about. He must decide what to do with it.
I had not, at any point drawn a line in the sand and said that if you step over that line you will do damage to your speakers.
Nor did I say that staying on this side of the line, will in all cases prevent damage.

Please also note that by quoting my previous post you are not disagreeing with me.
Rather you are disagreeing with the person that I quoted.
I added no new information about the topic in my previous post. I simply thanked Agedhorse for his comments on the matter.
I then threw in a little explanation about how my brain may be wired in such a way that I sometimes have difficulty, explaining my thoughts so that others can understand. I even suggested that it might be best for all, if I don't try to explain things for others.
I hope you don't have a problem with any of that?

Nope not disagreeing with you at all, just quoting through the chain/tagging.

There are some people that would tell you that a clipped signal is dangerous for speakers. They will then to and talk about square waves, saw tooth, and DC and a bunch of other malarky. The shape of the signal doesnt matter, as long as the total and average power don't exceed the mechanical and thermal limits of the speaker.

A 75 watt amp might damage a 100 watt speaker, because it over powered it. Never because it under powered it. Yes a 75 watt amp can over power a 100 watt speaker.

 

[Spoono Ghiefardi]

So here's part of the answer for the OP about the amp being able to put out more power than the speakers can handle. You almost never run your amp at maximum output because you rarely need to, especially if you have an 800 watt amp. If you run an amp that is capable of delivering more watts than the speaker can handle, your amp is going to just cruise along and easily put out whatever lower amount of watts it is you need. That means the amp runs with less heat and less heat means more reliability and less wear and tear on internal components - longer life for you amp. So that's a good thing. However it does mean that you need to pay attention to what you are hearing and if you start hearing farting sounds from your speakers, either turn your bass EQ down a couple of clicks and then drop the master if needed, or just go right to the master and drop it down. Just pay attention to what you are playing and how it sounds. Having an amp with more than enough power also makes it easier to add more cabinets if you want to.

I ran a couple of cabs off a 400 watt amp for a while. One cab had power handling of 200 watts and the other only 100-watts. If I played to aggressively - got too loud - the 100-watt cab would start to distort and I would have to back off immediately. I later replaced that 100-watt cab with a 400-watt power-handling cab and no longer needed to worry much about it. However, I could still hurt the cabs even though they were capable of handling more watts than the amp could deliver if I boosted the bass EQ too much. So you still have to pay attention to what you're playing and how you're playing it.

OK...this is the part where I tell you I now play with a cabinet that can handle more power than my amp can put out. I have an 800-watt amp and the DNS410 cab can handle 1400-watts. So I really don't need to worry much about it. Good news is that the cab is so efficient that it gets unbearably loud before I can run 800-watts into it. I'm not worried about hurting the speakers in my cab. That efficiency allows my amp to use less power for more than enough volume so I run the master typically between 9 o'clock and 9:30 , and my amp gets warm but not hot. Truth be known, I don't need an 800-watt amp to drive this cab to gig levels, but you never know when you might be asked to play a stadium...always be prepared.

Another variable that perhaps hasn't been thought about is speaker efficiency. If your speakers have high efficiency to start with, it doesn't take as much power to make them loud, so you may not need a particularly powerful amp. If on the other hand you have a speaker cab that has high power handling but it isn't efficient, then your lower-watt amp might not be able to get your speaker cab up to gig volumes. My current, high-watt handling 410 has an SPL rating of 106db 1W/1M (2.83v/1M), which is huge. The 410 it replaced had an SPL of 92 db 1W/1M (2.83v/1M), which is pretty poor. So my newer cab not only handles 3 times the watts, it's also far more efficient - 14db louder with 1 watt powering it.

So this stuff really is a balance kind of thing and there are many ways to make it work satisfactorily. If you have a cab capable of handling far more watts than your amp can put out and your amp doesn't have enough watts to drive that cab to gig volumes, then you have a problem where you should either use a more powerful amp OR more efficient speaker cabs. So there are a couple of choices for that problem.

On the other hand, if you amp can put out more than the speakers can handle, then you have to be sure to pay attention to your sound so you cam recognize and compensate for any speaker stress before it creases your speaker, melts your voice coil, or just tears the cones apart. Listening to what you're playing really isn't that hard to do.

Lots of ways to skin this cat.

Thanks. That's what I gathered from all the reply's. You just have to pay attention to your gear. Which in hindsight, I should have already known Just for the info, I just bought a Hartke LH1000 and was trying to find a cab for it. I didn't want to buy the matching cab since it has the aluminum in it. When I started researching other cabs, I found out that its not as simple as just buying a cab and playing. So thanks everyone for all the reply's. Its been a learning experience.

 

[BadExample]

Thanks. That's what I gathered from all the reply's. You just have to pay attention to your gear. Which in hindsight, I should have already known Just for the info, I just bought a Hartke LH1000 and was trying to find a cab for it. I didn't want to buy the matching cab since it has the aluminum in it. When I started researching other cabs, I found out that its not as simple as just buying a cab and playing. So thanks everyone for all the reply's. Its been a learning experience.

IMO, if you really want you gear to last a long time, I think its not a bad idea to get to now it well, under normal conditions. By that I mean play it loud away from your band and get to know the normal tone. Learn what it sounds like when played hard but not into distortion. Then you will notice anomlles in tone sooner if there is a problem. Should last very long if not constantly pushed to the edge. At half or 3/4 power amp and cab should be happy for a long time. If always pushed to the edge maybe not so long. Things run cooler if not pushed to the limit and should last a long time. If you find you always have to push it hard, maybe time to upgrade. God luck and rock on!

 

[ThisBass]

Headroom is not headroom if you end up using it. Headroom is available power that is not used, if it is used for transients then it's not headroom. This is a common misunderstanding.

I'd wish this fine explanation of headroom was more common to the crowd.

 

[Bob Lee (QSC)]

I'd wish this fine explanation of headroom was more common to the crowd.

I frequently encounter people mistaking volume for headroom—that is, turning up the volume = increasing headroom. I have to explain that it's actually the opposite.

 

[ThisBass]

Playing hard and NOT into distortion is like winning a contradiction at it's best.
Playing hard means clipping of transients which means headroom was gone long before starting playing hard anyway.

If there is an audible indicator of "clipping" anyway, let me tell it this way, the more the transients become clipped the more the sound becomes a feel of somewhat "smooth" compression without nasty clipping artifacts, the more the sound gets compressed and then (at a distinct point) the ears actually detect "clipping" but, clipping itself started at a much smaller power level before the ears really can detect it.

edit btw, at first view it makes no difference if transients are hard or soft clipped.
The crowd likes to consider an essential difference of tube vers. SS clipping but, for transients that makes no essential difference nothing at all.
The difference of tube versus SS becomes more significant when the transients are long gone and the signals envelope gets into the more sustained period of a played note (or a chord). That's then a huge number of difference of around may be 10..15dB (it depends of course) of difference between the transients and the perceived signal "sound" which we all feel and perceive as "loudness".

Hope someone might complete this thoughts in better understanding english words.

 

[Sid Fang]

Nope not disagreeing with you at all, just quoting through the chain/tagging.

There are some people that would tell you that a clipped signal is dangerous for speakers. They will then to and talk about square waves, saw tooth, and DC and a bunch of other malarky. The shape of the signal doesnt matter, as long as the total and average power don't exceed the mechanical and thermal limits of the speaker.

A 75 watt amp might damage a 100 watt speaker, because it over powered it. Never because it under powered it. Yes a 75 watt amp can over power a 100 watt speaker.

Maybe a diagram would be useful here.

You can think of the power being consumed and dissipated as being the area under the curves between the 0 axis and the Vc rails. When the signal is being clipped to the rails, the trapezoidal area is greater than that under the sinusoid of the same amplitude, and the power is higher, even though the frequency and max output voltages are the same.

 

[Korladis]

Maybe a diagram would be useful here.

You can think of the power being consumed and dissipated as being the area under the curves between the 0 axis and the Vc rails. When the signal is being clipped to the rails, the trapezoidal area is greater than that under the sinusoid of the same amplitude, and the power is higher, even though the frequency and max output voltages are the same.

Yes, but unless the cab can't handle that amount of power, it doesn't matter.

You can square wave a B-15 into an 810 all day long, and the cab will be fine.

 

[ThisBass]

why oh why I don't like sine waves to consider audio program material?
Sine waves may be good enough to explain something but they can't substitude audio program material.
If steady sine waves are referenced then there should be stated (at least) an quality meaning for audio program material IMHO.

 

[Sid Fang]

Yes, but unless the cab can't handle that amount of power, it doesn't matter.

You can square wave a B-15 into an 810 all day long, and the cab will be fine.

Don't know if you noticed, but I was replying to illustrate CL400Peavey's comment about how a "75W" rated amp could damage a "100W" rated speaker. But - and I should emphasize that I'm an engineer, but not a EE - it should be possible to compute the worst-case overdriven output power based on the rated clean output, and I *think* the worst case limit would be a signal so overdriven as to look like a square wave, which has an area that's pi/2 (1.57) times that of a sine wave of the same amplitude. So CL400Peavey's 75W amp just might be able to put out something over 110W of clipped output, and cook that 100W speaker, but your 810 should be able to handle the worst-case ~50W of a B-15 under duress.

Correct me if I am wrong, O Agedhorse.

 

[Sid Fang]

why oh why I don't like sine waves to consider audio program material?

Well, in theory, it can all be expressed as the sum of a large enough number of sine waves...

 

[ThisBass]

Well, in theory, it can all be expressed as the sum of a large enough number of sine waves...

In theory, No, not this way, not these easy understanding helping words.

Fourier Analysis is nothing but a basic to understand what's really going on under the hood.

Transients like it to change distinct frequency spectrum steadily within it's every own cycle, so how do you do a prediction of a sum of large enough sine waves for transients?

 

[megafiddle]

...
There are some people that would tell you that a clipped signal is dangerous for speakers. They will then to and talk about square waves, saw tooth, and DC and a bunch of other malarky. The shape of the signal doesnt matter, as long as the total and average power don't exceed the mechanical and thermal limits of the speaker.
...

There is definitely a myth that a clipped (flat topped) waveform contains DC. With a transformer output, the lowest frequency component will equal the fundemental frequency of the waveform. A clipped 100 Hz waveform will contain nothing lower than 100 Hz. (DC would be 0 Hz) This is also true for a symmetrical signal from a directly coupled output (e.g. solid state) amp. Bass guitar signals are pretty symmetrical on average, and will have little DC component. One exception is a clipped synthesized waveform from a directly coupled output. This could have a large DC component depending on the duty cycle.

The source of the clipping can be very important. If the clipping occurs in an overdrive or fuzz pedal, the amp output signal can always be reduced as low as one likes. If the clipping occurs in the output stage however, the power will exceed the undistorted power, and with bass guitar waveforms with strong fundamentals, this will likely exceed the rated power. Assuming that the power supply doesn't sag, this could be as much as twice the rated undistorted power. This power is also continuous (not transient) as long as the signal is continuous.

...
A 75 watt amp might damage a 100 watt speaker, because it over powered it. Never because it under powered it. Yes a 75 watt amp can over power a 100 watt speaker.

Quite true, but it does depend on how one defines "underpowering":

1) Underpowering - to supply less power than the speaker is designed to handle

This is so rather obvious, that it's difficult to imagine how it ever became an interpretation of the term in relation to damaging speakers. And yet it seems to be the basis for a common myth and dominates the discussions.

2) Underpowering - to use an amp rated at less power than the speaker

This makes more sense, since it is at least possible to damage a speaker with such a setup. But then so can an amp rated at more power than the speaker.

3) Underpowering - to use an amp rated at less power than that needed to reach the required sound level

Especially makes sense, since it implies that the amp may very well be overdriven in an attempt to reach some certain volume.

The warning about underpowering speakers (in the sense of definitions 2 or 3 above) goes back at least as far as the 70's, and was also related to hi fi stereo equipment, not just musical instrument equipment. Low power stereo amps were quite capable of burning up tweeters when the amps were overdriven for "party" volume.

-

 

[Schlyder]

I prefer cabs that can take more wattage than the head puts out... by at least 100w RMS

 

[ThisBass]

Bass guitar signals are very asymmetrical thus they contain a lot of *DC" in theory, like most of audio program material but, that doesn't matter

 

[ThisBass]

Clipping of asymmetrical signal like a bass guitar signal generates "DC" which may be send to a loudspeaker but, normally that doesnt't matter cause generated DC voltage is to small to harm VC of the driver.
It's nothing but some excursion "offset" the driver easily can compensate without damage.

 

[megafiddle]

Bass guitar signals are very asymmetrical thus they contain a lot of *DC" in theory, like most of audio program material but, that doesn't matter

Bass signals do not contain a lot of DC; in fact the pickup is not even capable of generating DC.

Overall, a bass signal is symmetrical. There are transient asymmetries that may be biased towards one polarity or the other, but these hardly constitute DC by themselves.

If there really was a lot of DC present, it would force the speaker cones away from their zero rest position and severely limit the output. This obviously doesn't happen.

-

 

[agedhorse]

The asymmetry can slightly bias the speaker cone off center over a (very) short time period but it's of no consequence and would not be considered a DC component unless it was either rectified, (or present as part of a DC bandwidth amp) and used as a reference offset. The fact that amps are generally not DC coupled, and are high passed in some fashion means that the asymmetry contains an envelope of correction where the circuit re-centers itself.

Asymmetry can enhance the "mild overdrive" experience provided the time constants of the low frequency part of the circuit are suitable for the task. This can be part of the flavoring of the OD response, especially feel. Very common in guitar and tube circuits where all kinds of asymmetries exist.

 

[-Asdfgh-]

The asymmetry can slightly bias the speaker cone off center over a (very) short time period but it's of no consequence and would not be considered a DC component unless it was either rectified, (or present as part of a DC bandwidth amp) and used as a reference offset. The fact that amps are generally not DC coupled, and are high passed in some fashion means that the asymmetry contains an envelope of correction where the circuit re-centers itself.

Asymmetry can enhance the "mild overdrive" experience provided the time constants of the low frequency part of the circuit are suitable for the task. This can be part of the flavoring of the OD response, especially feel. Very common in guitar and tube circuits where all kinds of asymmetries exist.

Thank you. It's nice to start the day learning something.