I haven't found the problem to be with the material. As far as I can tell my experience shows negative impact on sound (dramatically) near 100% for when any ferrite device does a 360° wrap around wires. This is especially true for anything transmitting dynamic power, and signal.
Power cords, IC's, DC link cables in amps, speaker cables, all of those were so clearly detrimental that they could probably be measured easily.
However in my old CD player (Bel Canto CD1) they are needed for good sound between the PCB boards. There's no AC signal through any of them. And the power is probably regulated down heavily after. The only signal is digital that goes through one.
For classD the most important factor with ferrite is using toroidial or wound cores on output (Hypex uses them), as opposed to the ferrite cased versions.
George,
Few ideas to elicit the effect (if possible)
1.) Constant tone to one driver with the second being swept?
2.) Constant tone in one driver with a pulse in the second? (Can't quite get a delta) Watch for ringing in the transient.
Then again, likelihood that I'm out to lunch is high.
Thank you for making the measurements!
Few ideas to elicit the effect (if possible)
1.) Constant tone to one driver with the second being swept?
2.) Constant tone in one driver with a pulse in the second? (Can't quite get a delta) Watch for ringing in the transient.
Then again, likelihood that I'm out to lunch is high.
Thank you for making the measurements!
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I still say this claim violates superposition in some way requiring an outside agency or some kind of non-linear or non-time invariant behavior to be excited.
This was a mistake I made years ago with a ferrite bead slipped over the leg of a series output resistor (in the speaker feed) on an amp. It seemed a good idea at the time, hazy thinking suggesting that the bead would stop RF from entering the amplifier picked up via the long speaker leads. It all seemed OK but a 10kHz check into 6 ohms showed dramatic distortion at anything more than few volts output. We are not talking subtle either, it looked like slew limited crossover distortion if you can visualise that.
The cause was the bead saturating.
one thing Otala did get right, is acknowledged and included in Cordell and Self books
simple idea is to pump the mass-spring resonance, then suddenly reverse the phase of the electrical drive signal at the worst point in the cycle
multi-way with the extra drivers, additional energy storage in XO parts can be worse than single drivers for this artificial current peaking by usiong the multiple different resonance frequencies at once
simple idea is to pump the mass-spring resonance, then suddenly reverse the phase of the electrical drive signal at the worst point in the cycle
multi-way with the extra drivers, additional energy storage in XO parts can be worse than single drivers for this artificial current peaking by usiong the multiple different resonance frequencies at once
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When we test loudspeakers in stadiums, the wind certainly causes wild swings in the impedance being measured. If the meter went to negative numbers we would probably see those as the test voltage is low and with excitation the transducers can probably produce more voltage than that.
Now as to non-linear, that really is the case for many acoustic systems. The transducer is only part of the system.
As to George's bit he says if he drove the drivers parallel or series, which I suspect means he was measuring coupled pairs, not quite the issue under discussion. But it does keep us on track as rarely able to actually communicate.
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As to George's bit he says if he drove the drivers parallel or series, which I suspect means he was measuring coupled pairs, not quite the issue under discussion. But it does keep us on track as rarely able to actually communicate.
Are you sure that information is not embedded in his suite of measurements. You did say the drivers are both driven with the same signal coupled face to face by symmetry in either case they are doing the same thing.
Not exactly. If the device under test is not driven electrically but only acoustically what will the impedance be?
OK that's not what you said exactly the first time. But I still feel it's like asking what's the impedance of a signal generator if it's on or set to DC.
Say you couple the drivers and short one and measure the terminal impedance, then apply a signal instead of short from and amp (Rout ~ 0) and again measure the impedance. To extract the impedance you have to account for the outside input. If you try to measure a 50 Ohm generator outputting an in phase signal of exactly the same amplitude as your stimulus you get nothing. You have to do the Norton/Thevenin superposition thing and remove the outside input.
The wind causes unexpected current it does not change the impedance.
When wind creates currents less than the drive then the measured impedance can go up or down depending on phase etc. The audio power amplifier may need to increase the current output to maintain the terminal voltage.
In multi-driver cabinets when one driver fails the others show a drop in impedance due to greater loading and will fail quickly thereafter if not repaired promptly.
The issue is if the transducer excites a resonance and then the activation signal stops can this induce impedance changes. In particular a drop in the impedance that measures as below the DCR. That is the issue as I see it.
No question external forces can affect loudspeaker performance.
No, this is not the impedance you are measuring. What was wrong with my analogy? Take a 50 Ohm generator putting out 1V at 1kHz and try and measure the impedance with a 1V at 1k in-phase source you get nothing, it looks like an open, but the generator still has a 50 Ohm impedance.
You have to remove the current produced by the wind, it is superimposed on your measurement. Yes the wind makes your amp have to supply more current but it has nothing to do with impedance. Instantaneous voltage and current when an outside input is present has nothing to do with impedance it is only a confounder (which you like, I know).
If you have an enclosure with multiple drivers and one of those fails you have to know whether it fails as an open circuit or if the voicecoil fails in a shorted manner. If it is a short then you have a vary low impedance connection which will affect the other drivers in that cabinet. If the driver fails open the total impedance in the enclosure will rise and each device will see higher power. Seems simple enough to understand the two failure modes.
Kindly,
I have never seen a driver fail by shorting. It is pretty standard for a dual driver subwoofer wired in parallel or even dual amplifiers to loose one driver and then the other. The rest of the bunch usually continue to work. The demonstration of woofer coupling is to tap one cone and watch the other follow. The thinking is that when one coil fails the other loudspeaker drives the first as a drone cone, the increase in load causes a soon to follow failure.
Scott,
Impedance is more than RLC. If you measure a transducer in a vacuum the impedance changes. If you horn load it, again it changes. If it drives a resonance.... The transducer moves the air and the air moves the transducer. The accoustic load is part of the impedance.
When the audio power amplifier has to produce more current for a given voltage that is considered an impedance drop, no matter what the cause.
I have never seen a driver fail by shorting. It is pretty standard for a dual driver subwoofer wired in parallel or even dual amplifiers to loose one driver and then the other. The rest of the bunch usually continue to work. The demonstration of woofer coupling is to tap one cone and watch the other follow. The thinking is that when one coil fails the other loudspeaker drives the first as a drone cone, the increase in load causes a soon to follow failure.
Scott,
Impedance is more than RLC. If you measure a transducer in a vacuum the impedance changes. If you horn load it, again it changes. If it drives a resonance.... The transducer moves the air and the air moves the transducer. The accoustic load is part of the impedance.
When the audio power amplifier has to produce more current for a given voltage that is considered an impedance drop, no matter what the cause.
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