Avoid blowing speakers!

[Guest bassman7755]

Well speaking as someone with amateur interest in electronics (and therefore not really and "expert"), a pure square wave requires infinite signal bandwidth to amplify accurately and most audio signal chains have various filters which will attenuate the extreme high and low frequency content so what arrives at your speaker probably wont look much like a square ware. Many amp power stages for example have a high pass filter which removes DC and near DC output. The clipped signal still contains more energy for a given amplitude though than a clean signal and so yes you will have to make some allowance for that.

[JTUK]

This is why I don't like FX's that are a massive booster... especially if the clour of the
FX can mask distress.

In an reasonable sound checked environment you shouldn't be competing with cymbals and
gtrs to be heard anyway... so you can help yourself there. Understand that this is a common
problem in these pages, but I don't quite understand the lack of desire to address basic
monitoring problems...and..to fight back with a louder rig...!!!

So, you can see how and why cabs blow if you basically can't hear what is happening to it.

[Bill Fitzmaurice]

[quote name='bassman7755' timestamp='1446705176' post='2901549']
Well speaking as someone with amateur interest in electronics (and therefore not really and "expert"), a pure square wave requires infinite signal bandwidth to amplify accurately and most audio signal chains have various filters which will attenuate the extreme high and low frequency content so what arrives at your speaker probably wont look much like a square ware.[/quote]Correct. First and foremost of those filters are voice coils, which are inductors, and as such function as first order low-pass filters. [quote]The clipped signal still contains more energy for a given amplitude though than a clean signal and so yes you will have to make some allowance for that.
[/quote]Close. At the fundamental frequency the power density of a pure sine and pure square wave is identical. It's only in the harmonics where power density of a square wave is higher, and that's why tweeters and the occasional midrange can be vulnerable to the higher power density of a clipped waveform, while woofers and subs are not. That's one reason why guitar amps don't use tweeters, and why if you're a bass player running distortion pedals you shouldn't unless you roll off the high frequency EQ on your amp to compensate for the high frequency boost that most pedals create. The exception, and there are always exceptions, would be a bass specific pedal that has internal EQ compensation to tame the highs.

[Phil Starr]

[quote name='Dad3353' timestamp='1446683508' post='2901521']
All precious stuff so far, with the different spotlights on the subject adding to the usefulness. If I may, I'd like to have some expert opinions on the rather modern tendency to use, not simple distortion, but outright fuzz on bass, giving a waveform much closer to square wave than sine. Does this not have a bearing on the cone behaviour, as it is effectively receiving almost a DC element for a good deal of its cycle. Would that increase the heat dispersion problems..? Is this negligible, or something worth considering when estimating power handling requirements for speakers..? Please ignore if too far off topic.
[/quote]

That's kind of true, and I like the idea of different spotlights, often a difference of technical opinion is down to a different perspective or at least answering a different question. For example what Bill says is true if you have a speaker with a crossover and a tweeter, and is the reason why you need to be so careful running a distorted signal through a poorly rated horn. If however you are putting the whole signal into a single drive unit and the signal is reaching the maximum voltage the amp can produce then the square wave will have 1.414 times the energy of an undistorted sine wave. The Cone and the coil will be travelling the same distance in each case so air movement and air cooling will be similar, depending just a little on frequency. However you can potentially have a little more heat to dissipate with a distorted signal and what actually happens will be down to the detailed design of the speaker and the amplifier in question.

In practice of course even if you have a pure square wave you will still be producing notes, which will have a loud start and fade with time and then a gap before the next note, even with metal So you may be producing 300W peaks or whatever but the power averaged over a few minutes will be a lot lower, allowing the speaker to cool between bursts of power.

Your poor tweeter though may be rated at 30W thermal in a 300W system and if you have a crossover the extra 0.414 of your 300W will be diverted that way so without some protection it is going to smell of scorching.