Will I blow the speaker?

[agedhorse]

7 hours ago, sandy_r said:

 

Well, we'll obviously have to agree to differ on that then - interestingly we don't disagree on the bottom line that the amp can be used carefully (ie. "less than 200W.") with that speaker, as long as the system is operated below clipping

 

You are obviously very welcome to have your own opinion on why the guideline value of "1/8 max. Power" (which i showed in a photoclip) was chosen by the regulating bodies to be at that level

 

Have a nice day 😊

 

 

 

You may disagree with my comments about the 1/8-rated power designation for labeling, but it’s fact not opinion. Its part of every global safety regulation and in order to legally place the CE mark under the CB scheme regulations, the power consumption that’s on the label must be the minimum of 1/8-rated audio power or higher IF the manufacturer intends for the amp to be used at higher average duty cycles. Every product that complies with CB scheme (IEC 60065 or 62368 with national differences) is required to be marked in this way.

 

I do this regulatory stuff every day as part of my design work.

[agedhorse]

6 minutes ago, Lfalex v1.1 said:

Quite apart from judicious use of the master volume control, some sort of compression and possibly an HPF (or something that acts like one) can be a worthwhile addition.

 

Tames nasty peaks, and prevents unwanted low frequencies that the cab can't reproduce  from making it past the HPF.

A HPF can certainly help by reducing the level where the cabinet is most vulnerable to mechanical damage.

 

A compressor might also help, but too much compression increases the average thermal power which may place the cabinet at risk due to increased  thermal power. With compression, a little can go a long way. 

[sandy_r]

12 minutes ago, agedhorse said:

 

 

You may disagree with my comments about the 1/8-rated power designation for labeling, but it’s fact not opinion. Its part of every global safety regulation and in order to legally place the CE mark under the CB scheme regulations, the power consumption that’s on the label must be the minimum of 1/8-rated audio power or higher IF the manufacturer intends for the amp to be used at higher average duty cycles. Every product that complies with CB scheme (IEC 60065 or 62368 with national differences) is required to be marked in this way.

 

I do this regulatory stuff every day as part of my design work.

 

I may agree or disagree with a lot of people about a whole lot of topics, but if you read my post above carefully you will see that your subsequent calculation of "less than 200W' looks vaguely similar to my earlier figure of "less than 200W"

 

So on what are we supposed to differ?  Certainly not the fact that the power rating is worded as "1/8 max. Power" (because it was me who posted the photo of it)

 

A careful read of my later post would show that i said that you are welcome to your own opinion of why the regulating body chose the level they did: ie. 1/8

 

When i see strawman arguments and appeals to authority appear in discussions then i know that subsequent discussion is going to be fruitless

 

[Bill Fitzmaurice]

3 hours ago, sandy_r said:

So, the power density of the signal to the woofer IS affected (as by clipping)

Not so. Power density is highest at the lowest frequency of the woofer passband. Go up one octave it's down 3dB. Go up another octave it's down 6dB, and so forth. No amount of clipping will cause the power density of harmonics anywhere within the woofer passband to even equal the power density at the lowest frequency of the passband, let alone exceed it.

[Bill Fitzmaurice]

2 hours ago, agedhorse said:

I do this regulatory stuff every day as part of my design work.

+1. By the same token I do this loudspeaker stuff every day as part of my design work. 😉

[sandy_r]

11 hours ago, Bill Fitzmaurice said:

Not so. Power density is highest at the lowest frequency of the woofer passband. Go up one octave it's down 3dB. Go up another octave it's down 6dB, and so forth. No amount of clipping will cause the power density of harmonics anywhere within the woofer passband to even equal the power density at the lowest frequency of the passband, let alone exceed it.

 

• A Square wave is equivalent to a single sinewave of the same fundamental frequency, plus the sum of all the odd-harmonic frequencies;
• The odd-harmonics, needed to create a square wave, decrease in power by 6dB an octave;

• So the woofer passband is decreasing 3dB/octave more slowly than that needed to create a square wave (ie. woofer passband is a non-issue);
• An amp driven increasingly into clipping converges towards a square wave type output at the same peak voltage of its max 'clean' (sine type) voltage;
• A Square wave will deliver twice the power, Into the same load, as a sine wave of the same peak voltage

ie. a 100W True RMS amp, clipping badly,can apply up to 200W (True RMS) into its usual load - hence advice to use speakers with higher power rating than the amp

 

Is this latest 'objection' supposed to divert attention from 'Why did they** choose the value: 1/8'? 

(**The regulatory body)

 

Edited January 23 by sandy_r

[sandy_r]

1 hour ago, Bill Fitzmaurice said:

+1. By the same token I do this loudspeaker stuff every day as part of my design work. 😉

 

No need to apologise - someone's got to do it 😉

 

Edited January 22 by sandy_r

[Bill Fitzmaurice]

27 minutes ago, sandy_r said:

a 100W True RMS amp, can apply up to 200W (True RMS) into its usual load - hence advice to use speakers with higher power rating than the amp

I never said it couldn't. But if that happens and as a result the the driver is blown it's not because it was underpowered, it's because it was overpowered. Too much ado is made about clipping, but it's just another complex wave form, which is what all musical tones are. The sine wave versus square wave comparison lacks any validity, as with the exception of some synthesizer patches neither are present in music. Even when that's the case it does nothing to bolster the myth that clipping kills drivers. If it did the name Robert Moog never would have been known outside of his family and friends.

[sandy_r]

21 minutes ago, Bill Fitzmaurice said:

 and as a result the the driver is blown it's not because it was underpowered, it's because it was overpowered.

...

oo much ado is made about clipping, but it's just another complex wave form, which is what all musical tones are. The sine wave versus square wave comparison lacks any validity, as with the exception of some synthesizer patches neither are present in music. Even when that's the case it does nothing to bolster the myth that clipping kills drivers. If it did the name Robert Moog never would have been known outside of his family and friends.

 

Bill, welcome to the OP: 800W Amp - 200W speaker (i guess you missed that, no worries)

 

So - possibility of overdriven speaker - 600W excess drive over rating - severe clipping - in most other universes, effectively a square wave 

 

Not a Robert 'Strawman' Moog in sight

 

 

Edited January 22 by sandy_r

[sandy_r]

@alexa3020 i hope that's a family-sized tub of popcorn you've got there on the sofa! ☺

 

Interesting diversion there, reminded me of a Talking Heads song with a road backdrop

 

To clarify then, my post from 4 days back (03:11 Thurs) still stands - you're good to go with your 200W speaker and a 'clean' signal (ie. derate that amp power for 'grit', heavy compression, or indication of clipping)

 

Edited January 23 by sandy_r

[Chienmortbb]

16 hours ago, sandy_r said:

So - possibility of overdriven speaker - 600W excess drive over rating - severe clipping - in most other universes, effectively a square wave

This is an area where a little knowledge is a dangerous thing, and I admit to being an enthusiastic amateur as far as loudspeakers are concerned. However, I was an Electronic Engineer by profession.

 

The speaker is being overdriven NOT the amp, that will still be outputting the same signal. The amp will clip if the input signal is too high, within limits the speaker will not affect. As the speaker exceeds Xmax, it will become non-linear as the coil is outside the influence of the magnet, and you will get compression. Push it too far, and you could destroy the speaker (XLim or XDamage) I used a 200 watt speaker from an 800 watt amp on Friday for two hours, without any problem. 

 

17 hours ago, sandy_r said:

a 100W True RMS amp, clipping badly,can apply up to 200W (True RMS) into its usual load

 

The term "True RMS" was coined for describing the readings of voltmeters and multimeters, as the early digital voltmeters could only measure RMS voltage for a single pure sine wave. Anything else would cause an incorrect reading. True RMS meters should read accurately, whatever the waveform.

 

True RMS is not a term I recognise in amplifier specifications. In fact, to be a pedant, there is no such thing as RMS power as RMS voltage x RMS current gives average power (although some in HIFI circles dispute this definition of average power). To understand why you have to know what the terms RMS means, not the literal Root Mean Squared but the practical use. The RMS voltage is that which causes the same rise in temperature, in a given resistance, as a given DC voltage. So put 120/240 volts DC across an electric fire element, and it will give out as much heat as if you put 120/240V volts (RMS) AC across it.

 

 

 

[sandy_r]

10 minutes ago, Chienmortbb said:

...

The speaker is being overdriven NOT the amp, that will still be outputting the same signal. The amp will clip if the input signal is too high, within limits the speaker will not affect...

Push it too far, and you could destroy the speaker...

I used a 200 watt speaker from an 800 watt amp on Friday for two hours, without any problem

...

The term "True RMS" was coined for describing the readings of voltmeters and multimeters, as the early digital voltmeters could only measure RMS voltage for a single pure sine wave

...

True RMS is not a term I recognise in amplifier specifications

...

 

Aye to all that

 

Posting here is a fine line between keeping it real but understandable for folks without a tech background, asking for some direction/guidance/ok etc, and knowing that someone somewhere is going to pickup on the technicalities without regard for the background of the OP

 

Very often it seems that pronouncements are made, to be ignored at our peril (so it sounds), without explaining why things may be the way they are

 

I used the term True RMS to try and avoid unecessary sidetracks about manufacturer's flights of fancy ...i knew it was a case of damned if i do, etc

 

I feel sorry for BCers like the OP who just want a clear, honest and usable answer and they get their thread subjected to a maelström of argument/discussion when people want to turn the OP into a p*$$*ng contest or an opportunity to revisit their pet subject

 

Joy ☺

 

[alexa3020]

12 minutes ago, sandy_r said:

 

I feel sorry for BCers like the OP who just want a clear, honest and usable answer

 

I don't mind, in fact I think I got the answer reasonably early on. I just wish I could keep up with the conversation - it's a bit like trying to get a chimp to understand... Well speaker cabinet design I suppose 😂

Appreciate everyone that's commented

[sandy_r]

14 minutes ago, alexa3020 said:

I don't mind, in fact I think I got the answer reasonably early on. I just wish I could keep up with the conversation - it's a bit like trying to get a chimp to understand... Well speaker cabinet design I suppose 😂

Appreciate everyone that's commented

 

Very gracious!  Everybody has experience of something, and we could all learn new stuff all the time 👍

 

[Baloney Balderdash]

If you really put your will behind it I believe you can do it! 

 

Edited January 23 by Baloney Balderdash

[agedhorse]

On 22/01/2024 at 12:26, Bill Fitzmaurice said:

+1. By the same token I do this loudspeaker stuff every day as part of my design work. 😉

Yes, and so do I Bill, but you already know this.

Edited January 24 by agedhorse

[agedhorse]

On 22/01/2024 at 14:44, sandy_r said:

 

Bill, welcome to the OP: 800W Amp - 200W speaker (i guess you missed that, no worries)

 

So - possibility of overdriven speaker - 600W excess drive over rating - severe clipping - in most other universes, effectively a square wave 

 

Not a Robert 'Strawman' Moog in sight

 

 

Actually, Bill’s correct on this. This example has nothing to do with clipping (in this universe anyway)

[agedhorse]

First of all, these additional discussions can be valuable for those who are open to learning. that’s why some of us put in the effort to explain things the way we do. 
 

Of course the additional information are going to be frustrating for someone who is struggling with the facts yet continues to post incorrect information as though they know what they are talking about. Clearly I poked that bear here, sorry for that.

 

The term RMS power is defined by industry convention to be power based on rms voltage and current, it is a descriptor which is well understood and accepted by the industry. It’s also been accepted by all of the regulatory agencies (safety and EMC) for audio equipment testing.

 

Hopefully this isn’t going to be controversial as well.

[agedhorse]

To respond to the message I received calling me a liar, here is where the test conditions for normal conditions are defined in the IEC 62368 regulations (for the EU). The input power to be labeled is defined to be the input power under these normal conditions (or greater if the manufacturer chooses a more stringent duty cycle because of the application). For example, for the amps I design for bass and electric guitar, I typically use more than double the minimum required under the regulations but for acoustic guitar it will be a little less than double:

 

 

Also, may I ask why there's so much rudeness here? For those interested in learning, I'm providing information that most players clearly don't understand or haven't been exposed to. For those of you who don't want to learn, why challenge the facts is such a manner? 

 

 

Edited January 25 by agedhorse

[Downunderwonder]

Don't sweat it Horse. I couldn't quite see where he was joining wrong dots so thanks to you and Bill for patiently explaining it yet again.

 

The old clipping kills speakers yarn puts another experienced nose out of joint.

[Chienmortbb]

@agedhorse Thank you for posting that snippet of the Standard. It is now close to 15 years since I retired, and with retirement I lost my access to the Standards Library at work. I should also confess that whilst Audio was the driver that led to my career in Electronics, I spent just about all my working life designing and testing Video products. While having the basic grounding, I don't have the earned experience that you have.

 

In case anyone wants to see the whole standard, it is 425 Swiss francs or approx £400.

[agedhorse]

8 hours ago, Chienmortbb said:

@agedhorse Thank you for posting that snippet of the Standard. It is now close to 15 years since I retired, and with retirement I lost my access to the Standards Library at work. I should also confess that whilst Audio was the driver that led to my career in Electronics, I spent just about all my working life designing and testing Video products. While having the basic grounding, I don't have the earned experience that you have.

 

In case anyone wants to see the whole standard, it is 425 Swiss francs or approx £400.

The video world moved way too fast for my comfort level, you could be qualified one year and completely unqualified to design new products the next year as the technology changed and the big player drove the market. It's hard to have a 40 year career in the video business as a designer/engineer IME based on friends of mine who followed this path.

[BassmanPaul]

On 23/01/2024 at 10:39, Chienmortbb said:

Electronic Engineer by profession.

 

Just as a bit of levity in a somewhat contentious thread;

 

Does this mean you are a Robot??  LOL

[Chienmortbb]

57 minutes ago, agedhorse said:

The video world moved way too fast for my comfort level, you could be qualified one year and completely unqualified to design new products the next year as the technology changed and the big player drove the market. It's hard to have a 40 year career in the video business as a designer/engineer IME based on friends of mine who followed this path.

Yes indeed. One of the reasons I retired/was made redundant.

[tauzero]

On 22/01/2024 at 20:24, Bill Fitzmaurice said:

Not so. Power density is highest at the lowest frequency of the woofer passband. Go up one octave it's down 3dB. Go up another octave it's down 6dB, and so forth. No amount of clipping will cause the power density of harmonics anywhere within the woofer passband to even equal the power density at the lowest frequency of the passband, let alone exceed it.

 

A square wave consists of a sum of sine waves at the fundamental frequency and odd order harmonics with an amplitude inversely proportional to the harmonic frequency (at 3f it's 1/3 the amplitude of the fundamental, 5f is 1/5 the amplitude, etc) so there's going to be a fair few harmonics but they're going to be progressively smaller in amplitude.