Pogre

Pogre

Audioholic Warlord
News is breaking now that intelligence services have known about this virus since November. Apparently fever pitch work has been going on to understand this virus at the top secret biological and Chemical warfare unit at Porton Down for at four to five months. Questions are now being asked about the origin of this virus in high places. I will post more about that later.
I have a friend who has been talking about the suspiciousness of the virus' origin from the start. He first brought it to my attention in January. He does get some of his info from some of the more fringe and one-sided "news" outlets and occasionally puts on the tinfoil hat so I take everything he tells me with a grain of salt.

He's linked me to video footage and "reports" that are very disturbing and incriminating. As is usually the case with tinfoil hats, here's no way to confirm or falsify anything tho.
 
AVUser001

AVUser001

Full Audioholic
That is true even if a speaker manufacturer says his speakers are 8 ohm. Unless you can find an impedance curve for those speakers or the manufacturer at least quotes a minimum impedance value, then assume your speakers are actually 4 ohm, as they likely are. The best rule of thumb if a minimum impedance is quoted to add 10% and take that as the true impedance.
That is exactly what I did recently on the amp purchase for my Focal Electras.
Their nominal impedence is 8 ohms, but dips down to 3.5 ohms. So I just treated those as a 4 ohm speaker, for my power calculations. That doubles the power requirements of the amp, and thats fine by me. Add to that, 20 db headroom for the peaks , that multiplies the power requirement 100x , which was factored into, as well.
Rated sensitvity was 91.5dB , but measurements showed slighly lower(91db), which was used.

This is going to be my reference 2 channel system - no compromise was made.
 
P

PENG

Audioholic Slumlord
Becos
Power in a AC circuit like speaker
P = Vrms * Irms * PowerFactor
where PowerFactor = Cos(Phase angle between Current and Voltage)

Which do you think the consumer is going to easily absorb...a single measure Power in watts or a multiple factors( voltage , current and the phase angle) ;-)

jk , you know what I mean...
The power formula does not even apply to most loudspeakers as a significant portion of the "watts" are dissipated in the power amplifier that drives the speakers. So it would have been better to educate the consumers from day 1 so that they understand the amp delivers current to the speakers binding posts, from there to the crossover and then to the drivers, causing the cone/diaphragm to move and produce sound. So the more current, the louder sound it would make. Everyone seems to know Ohms law, so they can understand at 2.83 V, the speaker will draw less current than at 28.3 V. To be more technically correct, power amps should be rated for current and voltage, e.g. 40 V/5A per channel maximum RMS, instead of 200 WPC. Regarding the phase angle factor, that is very much heat related, so something would need to be said about that too otherwise you can have an amp that is rated for higher voltage/current than another amp but yet it may be practical weaker if the other amp that is rated for a little lower voltage/current but can dissipate the extra heat due to driving a highly reactive load.

Loudspeakers "power" rating is also a misnomer. What does it really mean to say a speaker is rated for 20-200 W? It makes no sense as very few, if any moving coil loudspeakers would actually consume 200 W. I suppose they mean to say the speaker should be driven by an amplifier rated for up 200 W into an 8 ohm resistor, something like that I guess..:D
 
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Verdinut

Verdinut

Audioholic Ninja
The power formula does not even apply to most loudspeakers as a significant portion of the "watts" are dissipated in the power amplifier that drives the speakers. So it would have been better to educate the consumers from day 1 so that they understand the amp delivers current to the speakers binding posts, from there to the crossover and then to the drivers, causing the cone/diaphragm to move and produce sound. So the more current, the louder sound it would make. Everyone seems to know Ohms law, so they can understand at 2.83 V, the speaker will draw less current than at 28.3 V. To be more technically correct, power amps should be rated for current and voltage, e.g. 40 V/5A per channel maximum RMS, instead of 200 WPC. Regarding the phase angle factor, that is very much heat related, so something would need to be said about that too otherwise you can have an amp that is rated for higher voltage/current than another amp but yet it may be practical weaker if the other amp that is rated for a little lower voltage/current but can dissipate the extra heat due to driving a highly reactive load.

Loudspeakers "power" rating is also a misnomer. What does it really mean to say a speaker is rated for 20-200 W? It makes no sense as very few, if any moving coil loudspeakers would actually consume 200 W. I suppose they mean to say the speaker should be driven by an amplifier rated for up 200 W into an 8 ohm resistor, something like that I guess..:D
It means that the speaker can accept a maximum wattage of 200 watts as an instantaneous peak power for a fraction of a second, beyond which irreversible damage will occur.
 
langbecker

langbecker

Audioholic Intern
So in essence , if i have 4ohm and intend on playing movies at or close to 0db i better have an amp unless i want to cook breakfast on it.

Just sad they say its 4ohm stable and you end up frying it.

Sent from my SM-N960U using Tapatalk
 
langbecker

langbecker

Audioholic Intern
It means that the speaker can accept a maximum wattage of 200 watts as an instantaneous peak power for a fraction of a second, beyond which irreversible damage will occur.
My emotiva are pretty specific 200w rms 400 peak

Sent from my SM-N960U using Tapatalk
 
langbecker

langbecker

Audioholic Intern
Did McIntosh ever make an avr? Can't think of anyone else that might have. 2ch receivers, some. I'm west coast, TLS is in Minnesota.



Did it overheat or run very warm? What temperature was it? OTOH Marantz didn't actually rate it at 4 ohm either.
No mine hasn't yet. Just the hdmi diagnostic error "errh1-10 "


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P

PENG

Audioholic Slumlord
It means that the speaker can accept a maximum wattage of 200 watts as an instantaneous peak power for a fraction of a second, beyond which irreversible damage will occur.
I think you misunderstood my point, that is, a lot of users may be misled to believe their speakers actually take in and consume the wattage. I can use a real example to demo it if you are interested.
 
P

PENG

Audioholic Slumlord
My emotiva are pretty specific 200w rms 400 peak

Sent from my SM-N960U using Tapatalk
And they are specifically wrong, helped perpetuating an incorrect term Wrms. Electrical power is expressed as average, not rms though Emo is not the only one doing it, it seems only a few manufacturers now use the correct term "average" instead of "rms".

In simple form the power formula, as AVuser posted earlier, is:

P = V*I*Cos(Ø), where Ø is the phase angle between the V and I phasors (often called vector incorrectly)

Example: At 40 Vrms, 5 Arms, Cos(Ø) =1 for a pure resistor load, Power dissipated in an 8 ohm resistor will be:

P = 40 Vrms X 5 Arms = 200 W average or 400 Wpeak. That's for a sine wave signal only.

Note: the term rms does apply to voltage and current, just not power.

If you apply the same, using the example above, the speaker (moving coil type) will not be dissipating 200 W average, a good portion of the 200 W would be dissipated by the output devices of the amp, at large phase angle, most of the "W" would be dissipated in the amp and that would be problematic for the lesser power amps, let alone those in most multi channel AVRs.
 
Verdinut

Verdinut

Audioholic Ninja
I think you misunderstood my point, that is, a lot of users may be misled to believe their speakers actually take in and consume the wattage. I can use a real example to demo it if you are interested.
I entirely agree with you on that point. :)
 
AVUser001

AVUser001

Full Audioholic
The power formula does not even apply to most loudspeakers as a significant portion of the "watts" are dissipated in the power amplifier that drives the speakers.
I'm not arguiing for Power specifcations, but ..commenting on this particular point.

While its true a significant portion of the power is dissipated in the form of heat , due to voltage & current being out-of-phase over the frequency range, power formula still applies when the power factor is taken into account for the phase angle( & heat dissipatation).... becos loudspeaker circuits are a mix of resistance, inductance & capacitance and the voltage & current are not exactly 90 degree out of phase all of the time(infact never!).. Its varies over the frequency range.

Taken from https://sound-au.com/patd.htm

Only at a 90 deg Phase angle (worst case - never possible in loud speaker..becos there is always some resistance in voice coil) , does the Power factor & Load become zero (ie maximum heat dissipation - all power wasted)

1586449136385.png


So in most of the loudspeakers , this note applies .... "The phase varies over approximately +45°/ -60°, and while this is fairly realistic, some speakers will exceed this. The majority (and especially mid-woofers as used in most 2-way systems) will have a phase response of +/-45 degrees or so, some will be more, others less."

So at 45 deg, half the power is wasted (ie dissipated in the form of heat at the amp). This is the usually the worst case situation with most loud speakers.

Obviously, the best case situation is where Phase angle is 0 (current & voltage in phase) , where the speaker behaves like a pure DC circuit(P=VI) , and all the supplied power from amp is used by speaker, with no wastage.

Issue may be that, loudspeaker measurements with phase angles are not readily available, in most cases..Where its unknown, maybe assume a worst case of 45 degree out-of-phase and account for half the power being heat dissipated..(ie double the power required from amp to drive the speaker..to account for "wastage/dissipation"..but also aim for amp with better/larger heat sinks for dissipating quickly + extra cooling fans ;-)).

Case-n-point was the Focal Aria 936 speaker, I was looking at earlier,..where I was prepared..,but moot now, with a different speaker.
1586451229330.png


So it would have been better to educate the consumers from day 1 so that they understand the amp delivers current to the speakers binding posts, from there to the crossover and then to the drivers, causing the cone/diaphragm to move and produce sound. So the more current, the louder sound it would make. Everyone seems to know Ohms law, so they can understand at 2.83 V, the speaker will draw less current than at 28.3 V. To be more technically correct, power amps should be rated for current and voltage, e.g. 40 V/5A per channel maximum RMS, instead of 200 WPC.
YESSS!..., but I wouldnt assume everyone knows (or care to know) Ohms law , in the consumer space. Perhaps a simpler picture, thats easily understood by an average consumer, might help drive the point.

Something like this one from
, although may not be an accurate depiction of a Loudspeaker circuit with varying impedence.
1586451866231.png



Regarding the phase angle factor, that is very much heat related, so something would need to be said about that too otherwise you can have an amp that is rated for higher voltage/current than another amp but yet it may be practical weaker if the other amp that is rated for a little lower voltage/current but can dissipate the extra heat due to driving a highly reactive load.
Right , like mentioned above... An amp with better/larger heat sink less prone to failures..when the phase angle goes south!

Loudspeakers "power" rating is also a misnomer. What does it really mean to say a speaker is rated for 20-200 W? It makes no sense as very few, if any moving coil loudspeakers would actually consume 200 W. I suppose they mean to say the speaker should be driven by an amplifier rated for up 200 W into an 8 ohm resistor, something like that I guess..:D
right ,a bit misleading..that's really the speaker manufacturer's insurance policy - "I told you so" coverage - when the speaker gets toast when you crank all the way up with high powered amp ..;-) .Its supposed to provide a guideline to the consumers on the speaker's safe operating range. In reality , its not a hard upper limit of speaker's power handling capability either. And it does not guarantee the speaker wont go toast, within this supposedly safe range (ie you can fry the tweeter with under powered amp with clipping).

I liked this particular comment, published earlier on AH , on that


"The manufacturer of the speaker might rate the speaker at “150 watts” and I had to explain that damage could still be done with a 100-watt receiver, or a 50-watt receiver, or a 350 watt-per-channel separate amplifier. If you set your mind to it, you can and will damage any speaker. If your speakers are rated at 100 watts and your receiver is rated at 100 watts per channel, you’re still not entirely safe."
 
langbecker

langbecker

Audioholic Intern
I think you misunderstood my point, that is, a lot of users may be misled to believe their speakers actually take in and consume the wattage. I can use a real example to demo it if you are interested.
Yessir please.

Sent from my SM-N960U using Tapatalk
 
TLS Guy

TLS Guy

Audioholic Slumlord
These points are important.

It is too bad that impedance curves and phase angles are not in most spec. sheets.

There is usually phase swings at bass tuning and crossover points.

Here are the results of my in wall two way mains. In general two ways are an easier drive than three ways. These impedance fluctuations are generally associated with box tuning and the crossover points.

Here is the two way mains which has two 8 ohm drivers in parallel.



It is a sealed design and the major negative phase angle is associated with one impedance peak of a sealed design. However the impedance is 6 ohms where the phase angle is around - 40 degrees. The other relatively mild disturbance is associated with the 2.5 KHz crossover. Electrically it is first order low pass and second order high pass forming a composite fourth order crossover.

It does deserve an honest rating of being a four ohm speaker. I would have thought that any amp with any claim to quality should be able to drive that speaker. If not it is to my mind not worth the trouble to purchase and set up.

Hear is the three way center. It uses the same bass drivers, the mid unit is in the same series, but smaller and the same design principles. The crossovers are 400 Hz and 4 KHz, all second order electrical.



Again an honest rating is 4 ohm. I think any receiver should be able to drive it, as there is a zero phase angle at the point of minimum impedance, but I suspect many would object to this load, as it drops below 4 ohms at the 400 Hz crossover point.

Full details here.
 
P

PENG

Audioholic Slumlord
I'm not arguiing for Power specifcations, but ..commenting on this particular point.
Of course, it is hard to argue with facts, or even just mostly facts.:D
Thank you for taking the time to make my points!

I think instead of specifying like one of the most popular brand on AH typically would do on their spec sheets such as:

POWER HANDLING (CONT/PEAK) 150W/600W

that is so ridiculous, it would be much better if they specify it like:

Suitable for use with amplifier specified 150 W average into 8 ohm continuously and 200 W dynamic output, 20-20,000 Hz at less than 1% total harmonic distortions.

That's not much to ask right?

And by the way, for sensitivity specs, many manufacturers including the major brands such as Polk Audio, Monitor Audio, Axiom etc., still use the XdB/1W/1m. That is so "technically" wrong if you want to be technical about it. If you apply the formula to say a Klipsch that specs say 96dB/1W/1m, 8 ohm nominal, they you would think that:

At 2.83 V, it would do 96 dB at 1 meter right? And yes let's assume it is anechoic.

If so, try that power formula for the 1 kHz test signal (pure sine wave tone), but still, what is the odd that the phase angle would be 0 degree at 1 kHz?

They (all manufacturers) really should all standardize on the "2.83 V" instead of 1 W to avoid getting the technically minded people confused..

Aside from the above rant, I noticed some seemed to have improved on their specs significantly, such as Definitive Technology and Axiom, on the power requirements spec, but unfortunately not the sensitivity specs.

For example:

DefTech's
SENSITIVITY 92dBSPL IMPEDENCE 8 ohms
RECOMMENDED INPUT POWER 50-200W (1% THD, 5SEC.) 150W

is a little better than B&W's:

Recommended amplifier power
30W - 200W into 8Ω on unclipped program

Axiom's even better, though still lacking, such as the 1W/1m vs 2.83 V, and obviously the undefined "Max Dynamic Amp Wattage".

Why don't these guys all hire at least one good EE who graduated from the power and control stream, with strength on the electronic side and let him/her/them review/approve the specs written by the marketing people?:D

Max RMS Amp Wattage400 Watts
Max Dynamic Amp Wattage1600 Watts
Min Amp Power10 Watts
Freq Resp +/-3dB (Hz)34 - 20k
Freq Resp +3dB- 10dB (Hz)28 - 20k
Impedance (Ohms)4 Ohms
SPL in Room1w/1m(db)94 dB
SPL Anechoic 1w/1m(db)90 dB
 
P

PENG

Audioholic Slumlord
Yessir please.

Sent from my SM-N960U using Tapatalk
I think I might have covered that in my response to AVUser001 in post# 54 already. You can also take a look of the specs of your speakers and ask yourself what is your interpretation, than we can discuss further.
 
AVUser001

AVUser001

Full Audioholic
I think instead of specifying like one of the most popular brand on AH typically would do on their spec sheets such as:

POWER HANDLING (CONT/PEAK) 150W/600W

that is so ridiculous, it would be much better if they specify it like:

Suitable for use with amplifier specified 150 W average into 8 ohm continuously and 200 W dynamic output, 20-20,000 Hz at less than 1% total harmonic distortions.
Cant agree more!

And by the way, for sensitivity specs, many manufacturers including the major brands such as Polk Audio, Monitor Audio, Axiom etc., still use the XdB/1W/1m. That is so "technically" wrong if you want to be technical about it. If you apply the formula to say a Klipsch that specs say 96dB/1W/1m, 8 ohm nominal, they you would think that:

At 2.83 V, it would do 96 dB at 1 meter right? And yes let's assume it is anechoic.

They (all manufacturers) really should all standardize on the "2.83 V" instead of 1 W to avoid getting the technically minded people confused..
Right, seems more manufacturers are switching to Voltage based sensitivity rating.. For eg, I see Focal's sensitivity rating of the 1028 Electra, from several years back ,

1586633121025.png


Martin Logan does it too, right
1586634481355.png


A power sensitivity rating such as Xdb/1w/1m is only valid when at frequencies where the impedence exactly matches the speaker's nominal impedence (ie Power sensitivity is frequency dependent). I will go to the extent of calling its a CRIME to specify the Power sensitvity such as 90 dB/1w/1m , without also specifying the nominal impedence (4ohms,8 ohms etc) and providing an impedence over frequency curve :)

Switching to a fixed Voltage sensitivity, takes the frequency out of the equation and is valid for most of the frequency range for the speaker with a given nominal impedence.

For some wondering, where the 2.83V came in , its essentially equivalent to 1w at 8 ohm
P=VI=Vsq/R => V=sqrt(P*R)

So at 1w & 8 Ohm
V=sqrt(1 * 8) = 2.83v

Why don't these guys all hire at least one good EE who graduated from the power and control stream, with strength on the electronic side and let him/her/them review/approve the specs written by the marketing people?:D
Are you available ;-) ? [ Edit : Replaced "open" with "available"]

continuing the rant...,

A "Power Amplifier" is a misnomer too ! It doesnt amplify power...,it amplifies voltage :) , so probably a "Voltage amplifier" is more the appropriate term! Perhaps, the marketing people decided "Power" is sexier than "Voltage" ...


But now that we're talking about all these things ;-)...,
I need to let out a pet peeve , on the Power calculator, often referred to by many of our AH members..,when someone asks in the forum , what kinda amp or AVR is suitable for my speaker for my room or how much power do I need to drive a speaker etc..Often they get pointed to this Peak SPL Calculator .

While it does adequately what its intended for (to get the SPL for a given sensitivity , power input at MLP)..., it lacks in many aspects and can infact be misleading if not applied correctly (esp by inexperienced people), I think. Lets look at this closely...,

1586637511712.png


All it takes as User inputs are Sensitivity , Amp power( the very thing the people are trying to find out! ), distance to MLP, #Speakers and boundary reinforcement and spits out dB SPL at MLP.

1st gap:
To get the required amp power, for a given SPL, you need to keep trying different Watts as input, until you hit the required SPL . The quickest and right way to do this would be to punch in your required SPL and the calculator to spit out the required power ... not the other way around like this calculator does!
There's no way to input the average SPL !

2nd gap:
This calculator implicitly assumes 8 Ohms speaker! What do you do , when your speaker has a 4 ohm nominal impedence ? An inexperienced person may not even realize this and just use the Watts as it is...leading to a gross mistake in power requirement.
To get the right Watts, for a 4 Ohm speaker, you'd have to double the amp power from this calculator
OR
derate the speaker sensitivity by 3 dB to get the watts, at the same implied 8 ohms

3rd gap:
No place to input headroom required to account for peaks in SPL.
You'd have to manually keep adjusting the Amp power ,until you hit your desired headroom (say +20 db)

4th gap:
Doesnt clearly distinguish equivalent RMS Watts and Peak Watts. Again can mislead people, where they can unwantedly double the power again , to get the peak!

There are better Amp power calculators out there...that addresses the above gaps . Maybe we should redirect people to these calculators instead ...

For eg, this one from Acoustic Frontiers
1586642182620.png


  • Allows you to enter the desired average SPL and get the required Peak & RMS watts in one shot. No need to keep trying different amp watts to find the right one!
  • Also allows you to input Speaker's nominal impedence such as 8 or 6 or 4 etc ...to account for all speakers..and not having to play around with power or sensitivity to account for speakers with impedences other than 8 ohms. Automatically adjusts's speakers sensitivity to account for impedence ( He's incorrectly calling Sensitivity as Efficiency ..thats not right..,but that's a different topic!)
  • Allows you to enter the desired headroom/peak SPL such as +10, +20, +30 etc.. No need to do any adjust amp watts further to estimate for peak listening levels
  • Clearly identifies the Peak and equivalent RMS power required...No confusion and wrong interpretation leading to costly amp mistakes (like buying double of what you really need)!
From my pov , this one https://myhometheater.homestead.com/splcalculator.html is a little use-less for the amp estimates with different conditions..(not completely useless, just less useful and error prone and can be misleading inexperienced people)...

Ofcourse we dont need these online calculators and go straight with calculations.., but they're useful for most people with a polished UI. The acoustic frontiers one (and there are others as well ) are much more verstatile, flexible and should get the job done, without trial-and-error and further error-prone manual adjustments to get the final numbers.
What do you think, can we all switch and redirect future questions to this one instead ?
 
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