I must correct one thing!
"8 Ohm speakers surged more than 5-6 times the energy of a lab resistor"
I did not mean energy, but current.
"8 Ohm speakers surged more than 5-6 times the energy of a lab resistor"
I did not mean energy, but current.
Yes. BTW, IIRC one of the bad speakers in this respect was the Yahama NS1000.
jd
No. A transient (in audio) is music. ALL musical instruments have transients. It only becomes distortion if your amp can't handle it.
jd
janneman, I understand what you say. It seems that I have not found the right translation of what I mean (I mean the word "transient"). But I think to the last, yours mean what connotation I gave of the word.
Regards.
Regards.
Jan,
I don`t agree. Short-duration, large-magnitude, high-frequency signals are not transients. Transient distortion arises when amplifier components cannot handle the rate of change of the signal.
I don`t agree. Short-duration, large-magnitude, high-frequency signals are not transients. Transient distortion arises when amplifier components cannot handle the rate of change of the signal.
I didn't say that, so how can you agree or disagree?
Different topic, not the subject we were discussing.
Lumba, it's fine if you want to continually change the subject to find one you get right, but I don't play along.
Have a nice day,
jd
A transient in the audio context is part of the music. If your amp can't follow it because it is too slow, and distorts it, that's transient distortion. Two things. Look it up.
Now can we leave it alone, pulease?
jd
It looks like TIM has found its way into our class A discussion.
TIM works as much for class A as for any other class, and is not at all specific to class A.
To define "peak" one could say, that peak to peak voltage or current is the uncorrected voltage/current delivered to the load.
This goes for all voltages and currents, both audio and non audio.
Looking at i.e. a European wall outlet, you will mostly find around 310-325 VAC peak to peak.
The RMS (Root Mean Square) value though will be around 230V, which equals 230V DC.
All multimeters are corrected, but an oscilloscope will show you the facts.
TIM works as much for class A as for any other class, and is not at all specific to class A.
To define "peak" one could say, that peak to peak voltage or current is the uncorrected voltage/current delivered to the load.
This goes for all voltages and currents, both audio and non audio.
Looking at i.e. a European wall outlet, you will mostly find around 310-325 VAC peak to peak.
The RMS (Root Mean Square) value though will be around 230V, which equals 230V DC.
All multimeters are corrected, but an oscilloscope will show you the facts.
Last edited:
Or music as distortion ??? Playing with something that makes music and distortion (analog synth) ,I've seen a little truth in this. Playing a very high slew sawtooth wave through a low slew power amp has the same effect as changing the slew of the sawtooth at it's source.. , as far as the resulting timbre (high order harmonics).
These type of waveforms are very common in modern music and I've seen some modern digital recordings that required the amp to slew at 10's of V/us. One could expect that this (the transient) would be as fast as the weakest link (amplification stage) from artist in the studio to YOUR amplifier.
OS
Second question
Suppose that we have an ordinary Hi-Fi speaker system, with:
1) Impedance nominal = 8Ω
2) Sensitivity with 1W/1m = 87dB SPL
3) Power Handling = 150Wrms Continuous (34,64Vrms)
4) Maximum SPL = 100dB at rated power (150Wrms)
This speaker is driven by a class A amplifier powered from the usual supply of, say, +/-20Vdc. Question:
It is in effect the relation P=V.I in this case? If yes, then:
The maximum output voltage swing of amplifier it is +/-20V => 14,14Vrms. Consequently, from the relation P=V.I and because the maximum output voltage swing of amplifier is insufficient to drive the speaker in its maximum SPL, suppose that this must be covered from its plentiful output current, which in this case must be: I =P/V = 150/14,14 = 10,6Arms or 15Apeak or 30Ap-p. Right?
I am in waiting of your reply to place another one question.
Thanks
Fotios
Suppose that we have an ordinary Hi-Fi speaker system, with:
1) Impedance nominal = 8Ω
2) Sensitivity with 1W/1m = 87dB SPL
3) Power Handling = 150Wrms Continuous (34,64Vrms)
4) Maximum SPL = 100dB at rated power (150Wrms)
This speaker is driven by a class A amplifier powered from the usual supply of, say, +/-20Vdc. Question:
It is in effect the relation P=V.I in this case? If yes, then:
The maximum output voltage swing of amplifier it is +/-20V => 14,14Vrms. Consequently, from the relation P=V.I and because the maximum output voltage swing of amplifier is insufficient to drive the speaker in its maximum SPL, suppose that this must be covered from its plentiful output current, which in this case must be: I =P/V = 150/14,14 = 10,6Arms or 15Apeak or 30Ap-p. Right?
I am in waiting of your reply to place another one question.
Thanks
Fotios
Fotios,
Not sure I follow what you mean, but I think it is this.
You cannot drive this speaker to max SPL with the 20W amp. Even if the amp is able to drive 10A RMS, this 10A will never flow, because the amp can only give 14VRMS in 8 ohms is just 1.75A. The only way to drive this speaker more is to get more output voltage (so, more supply voltage) from the amp. Or change the speaker in a 4 ohm one which doubles the current it will take from 14VRMS. Your speaker is also quite insensitive with 87dB at 1W/1m.
jd
Thanks Jan for the reply. Yes, your calculation it is right; I = V/R = 14Vrms/8Ω = 1.75Αrms. It shows maybe that the relation P=V.I it is not in effect for the calculation of the amplifier output power versus the power demand of the speaker system?
The data for the speaker that i reffer are imaginary of course, because i don't know any constructor of Hi-Fi speakers which reffers the nr.4 parameter "Maximum SPL at Rated Power". Instead, most constructors of P.A. speakers they give this parameter but this type of speakers is unrelated with class A amplifiers of course.
OTOH physics are physics. I have front of me, the instruction manual of a P.A. speaker of Peavey (118 International) for which - if you want - i can give you the 4 parameters to make an exercise. The important thing, it is that in the manual is reffered: 1) Power Handling = 350W continuous (52,9Vrms) and 2) Maximum SPL = 122dB at Rated Power (350Wrms).
This implies that the Voltage Swing has relation with the SPL produced and not the output current ability of the amplifier.
I am wondering, what can i hear from a class A amplifier driving an insensitive speaker? Where the SPL produced will be very low?
Take this please as a query and not as an obsession.
Thanks
Fotios
Well, just consider the amp as a voltage source and the speaker as a resistor for simplicity. Ohms law says V=I*R or I=V/R. If your voltage source gives off 32VRMS, the current HAS to be 4A RMS.
The power that this develops in the resistor (or in the speaker) is V*I=128W.
The SPL versus power has to do with the efficiency of the speaker to turn that electrical power into air vibrations. So if your speaker has a 90dB/1W/1m sensitivity, that 128W will give an SPL of 90dB + whatever 128 is in dB (quick calculation: 10log(128) = 21dB) gives 111dB SPL at 1m from the speaker.
That's all there is to it, really.
There's nothing so practical as a little theory 😉
jd
Thanks again Jan. Now i am wondering if a P.A. speaker which is very sensitive like the Peavey 118 Int. with a SPL/1W/1m = 99dB (swept sine input) which translated in: V = (sq.root) P.R = 2,83Vrms it is more appropriate for audition test of a class A amplifier instead of some insensitive Hi-End speakers 😀
Usually Hi-Fiers they detest a P.A. speaker mainly because the hard (accordion type) surround of its bass driver. OTOH i think that Klipsch uses drivers of this type in its recognized and very expensive speakers. I remember from the past as well, a famous studio monitor speaker of Tannoy with only one 15" coaxial bass driver with accordion type surround.
Fotios
Yeah well which speaker to use for audition is really very much taste dependent and I don't want to get involved there!
But I would think that efficiency is not a primary concern here.
jd
this is all confused.
the heating effect of a voltage feeding a pure resistance is used to compare DC voltages and rms voltages.
230Vdc has the same heating effect as 230Vac.
For a pure sinewave of 50Hz (or 60Hz) the maximum voltage is sqrt(2) * Vac.
230Vac = 325.27Vpk = 650.5Vpp
Vac peak to peak is a nonsense voltage unit and to specify 310 -325Vac peak to peak as equal to the EC 230Vac is an even bigger nonsense.
In summary for pure sinewave signals the heating effect of all the following are identical when supplying a pure resistance.
230Vdc := 230Vac := 325Vpk := 650Vpp 🙂= equivalent to)
Sorry!
I should have written 310-325 peak - and not "peak to peak." Which of course is the dobble value in an alternate current.
But I hope the idea was clear at least.
- Status
- Not open for further replies.