The complexity and challenges are an aspect that makes the hobby MEH worth it🙂
The effortless cohesive sound is the other.
I’m primarily interested in sound quality; would such an MEH really sound that much better than an ATH loaded single driver ?
When you have heard a well designed MEH you know why you do it.
Here is a prototype I'm working on atm.
Where the drivers face each other in order to minimize the vibrations in the horn.
Maybe it's a good idea, maybe it's a bad idea.
One way to find out 🙂
Here is a prototype I'm working on atm.
Where the drivers face each other in order to minimize the vibrations in the horn.
Maybe it's a good idea, maybe it's a bad idea.
One way to find out 🙂
Mostly PLA, but I don't have much experience with different materials. Tried PETG a few times, it's really light. But those were all basically prototypes. I would definitely use something more sturdy for the final adapters (maybe I would even try to cast them instead). For petals I guess it's already good enough, as I tend to make them rahter lightweight and basically hollow with only a very sparse infill. The thickness alone seems to do a lot.
A460G2 / BMS 4554 (16 ohm), long adapter, electrical impedance.
What to take from this?
The "noise" between 700 Hz - 2.5 kHz is remarkably stable (averaging does nothing). It changes a little bit only with a different orientation of the waveguide relative to the environment. So this must be the driver picking up the sound field (?) and I guess the curve would be cleaner in an anechoic room.
Which leads me again to wonder how much is the impedance "modulated" by the picked-up signal of the reproduced sound field during playback. The driver acts as a microphone at the same time, right? I guess that a high sensitivity doesn't really help in this regard.
What to take from this?
The "noise" between 700 Hz - 2.5 kHz is remarkably stable (averaging does nothing). It changes a little bit only with a different orientation of the waveguide relative to the environment. So this must be the driver picking up the sound field (?) and I guess the curve would be cleaner in an anechoic room.
Which leads me again to wonder how much is the impedance "modulated" by the picked-up signal of the reproduced sound field during playback. The driver acts as a microphone at the same time, right? I guess that a high sensitivity doesn't really help in this regard.
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Direct (red) and with a 27ohm resistor in series with the driver (black).
Does it make sense?
Does it make sense?
Yes, it makes sense to me—the same curve, just 27 ohms higher. I would expect that if the 27-ohm resistor were in parallel with the driver, the curve would be flatter. Not sure the wiggles would go away.
The second 4554 driver sitting on the table, without a horn, with the exit open (red) and covered with a blanket (black).
- I would think that if the wiggles were due to a microphone action, they should be smaller with a series resistor but maybe I'm wrong. I'm hopelessly dumb at electronics and I gave up a long time ago.
So, what causes the wiggles?
- I would think that if the wiggles were due to a microphone action, they should be smaller with a series resistor but maybe I'm wrong. I'm hopelessly dumb at electronics and I gave up a long time ago.
So, what causes the wiggles?
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It seems to me that with the second 4554 measurements, you have shown it is not the microphone that causes the wiggles. The cause of the wiggles is unclear. I should have my 4554's on the 520G2 in a few days. I'll post FR and impedance plots.
I'm not sure it's so clear. The driver alone has only a small opening. But a big horn can "amplify" not only what comes out, but also what comes in - it can catch a lot more sound and direct it all to the diaphragm.
That's great 👍
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I think in the reverse horn direction, one actually have attenuation equal to the horn transformation ration... 😉
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The driver is fed by high impedace?
What about damping the "bell" of the 460? Something rubbery with high density...
Because it changes with the orientation of the waveguide (by turning it on the stand), I believe it's indeed somehow coupled to the surrounding/reflected sound field.
Do another impedance sweep, but yell into the device while you do it!🙂
When you add the resistor in series, while it should reduce current from microphonics it also reduces electrical damping. Try with capacitor in series for poor electical damping and "high" current from microphonics. Try also with series resistor plus an inductor between the driver and resistor, parallel to driver, to make a "sine-cap" highpass filter. This maintains low impedance at the main resonance for electical damping, while puts higher impedance higher up to reduce microphonics.
Anyway, I think the high impedance, or wiggle, is some extra velocity of the moving parts. Extra in sense that diaphragm moving induces current whose vector sum with current from amplifier (if moving parts were clamped down) makes total circuit current to reduce = impedance to increase. Thinking other way around, when there is impedance peak the diaphragm moves more than it should, with given excitation by the amplifier. ~Everything that makes impedance vary beyond Re + Le is from movement of the diaphragm, and varying forces affecting that movement, which affects circuit current (since amplifier voltage is constant).
Anyway, I think the high impedance, or wiggle, is some extra velocity of the moving parts. Extra in sense that diaphragm moving induces current whose vector sum with current from amplifier (if moving parts were clamped down) makes total circuit current to reduce = impedance to increase. Thinking other way around, when there is impedance peak the diaphragm moves more than it should, with given excitation by the amplifier. ~Everything that makes impedance vary beyond Re + Le is from movement of the diaphragm, and varying forces affecting that movement, which affects circuit current (since amplifier voltage is constant).
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Do you have the simulated acoustical impedance curves of the A520G2 and A460G2 with the T520-4554-EXT Adapters? Maybe some differences are visible?
If I remember correctly, the first simulations of an extend throat did show some ripples in impedance?
If I remember correctly, the first simulations of an extend throat did show some ripples in impedance?
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