Testing for what.
Sub in normal real operation is likely be a Reflex design.
Which Unloads below the Reflex.
Anything reasonable will have over excursion filter.
So any sub be high passed 4th order around 25 Hz
amplifier below 10 Hz is pointless.
otherwise with any amp just make the input and feedback
capacitors so ridiculous large low frequency be down to
maybe 1 or 3 Hz.
Amplifiers shutting down, well yeah any class D will
buss pump itself to death.
But they changed topology and improved dead time.
So it is less a issue. But same thing bandwidth be limited anyways
for excursion protection. And helps regardless for bus pumpers.
At very high power, sure anything can shut down.
Usually the switcher power supply giving up on life. lol
Sub in normal real operation is likely be a Reflex design.
Which Unloads below the Reflex.
Anything reasonable will have over excursion filter.
So any sub be high passed 4th order around 25 Hz
amplifier below 10 Hz is pointless.
otherwise with any amp just make the input and feedback
capacitors so ridiculous large low frequency be down to
maybe 1 or 3 Hz.
Amplifiers shutting down, well yeah any class D will
buss pump itself to death.
But they changed topology and improved dead time.
So it is less a issue. But same thing bandwidth be limited anyways
for excursion protection. And helps regardless for bus pumpers.
At very high power, sure anything can shut down.
Usually the switcher power supply giving up on life. lol
Of course the subwoofers are going to be sealed. Allows reproductions of very low frequencies in a sealed room (way lower than what's practically needed).
That should help, cool no reflex.
Otherwise as mentioned just make the input/ feedback capacitors so large
the bandwidth of the amp goes as low as possible.
Otherwise as mentioned just make the input/ feedback capacitors so large
the bandwidth of the amp goes as low as possible.
Most standard amp designs can be changed to DC by shorting out one capacitor in the feedback network, and maybe bypassing an input cap - however its got issues, for instance if the amp has speaker protection it may work by sensing DC on the output, so you'd have to disable this protection too. And of course loudspeakers die rapidly with DC offsets as the high power dissipation is not air-cooled by the coil motion.
And without the cap in the feedback network the input-stage voltage offset gets multiplied by the gain, so even with 0V input the output DC offset could be quite large, and fluctuating with air currents over the input devices...
So unless you are planning to drive a barymetric chamber there's never need for DC gain in an audio power amp, and several good reasons not to have it. Or put another way DC for a sound wave affects barometers, not ears.
And without the cap in the feedback network the input-stage voltage offset gets multiplied by the gain, so even with 0V input the output DC offset could be quite large, and fluctuating with air currents over the input devices...
So unless you are planning to drive a barymetric chamber there's never need for DC gain in an audio power amp, and several good reasons not to have it. Or put another way DC for a sound wave affects barometers, not ears.
For my knowledge there is not a single subwoofer that can handle 0.1Hz on this planet. If I missed something, pls enlighten me.
Edit: Now I got it, steam hammer are the tools that operate in this frequency region.
Last edited:
Adding an option, solves the heat disappation problem.
But i don't think a small DC signal is going to kill most speakers.
Passive cooling of midrange elements is the norm, it works as long as the power is low enough.
Modifying an existing amplifier is of course an option. Ill look into that for my testing.
They can handle it just fine, the output signal is just going to be a lot weaker since it's well below the resonance frequency of the driver.
In a sealed room the pressure over time can still be accurately reproduced even at say 0.001hz, the issue is that you are then not reproducing the wind which is more likely to be percieved than the slow pressure change.
Where does subsonics begin, 20Hz? Below some frequency sound may not be heard so much as felt, but the effects may still be noticeable. There are reasons why some pipe organ music is performed with stops set to produce very LF beat notes. Similarly, some bass drum sounds tuned to very low frequencies can also viscerally shake the room.
Yes, good point. Is there really any musical content produced with subsonics? But then again, there's Hollywood.
Part of the issue may have to do more the time domain than the frequency domain. IIUC at lower frequencies it has become uncontroversial that humans can be sensitive to phase. When there is a corner frequency at, say, 10Hz, there may already be significant linear waveshaping distortion for complex sounds such as transients with a fundamental frequency of, say, maybe 50Hz or 100Hz. Some people appear to find that some instruments just don't sound the same when the time domain waveform has been too much linearly distorted by relative phase shifting of different harmonic components. Of course, the extent to which such an effect may be noticeable may also depend on speaker design. Some speakers rely on resonance effects to extend LF response. Depending on particulars, FR may look fine in steady state tone measurements, but not as good in terms of transient response and or waterfall decay.
OK, but let's not imagine that the woofer system will not be far more egregious in its phase error.
It could also be said that some woofer systems will more egregious than others. Question for me might be, if using a particularly favorable woofer system, will any potential benefit from improved amplifier phase response be completely swamped by the speakers?
Correct me if I am wrong but isn't flat frequency response equivalent to constant acceleration, hence cone displacement increases as the cubic (?) as frequency goes down. Seems ridiculous to attempt even 1 Hz response with any real power as perhaps even 1 watt. What would be the displacement needed (given some realistic surface area of perhaps a 15" driver) even if you had 100dB efficiency speakers?
Of course there is.
1812 overture feature cannons which has brutal subsonics.
bass i love you was specifically created to be really though to reproduce,
This is the frequency response for a more typical song:
No it's quadratic v=at, s=at²/2
a=sin(bt)
v=-cos(bt)/b
s=-sin(bt)/b²
But in a real room (not outside) the lower frequencies will get amplified so it's actually possible to get a flat frequency response down to say 0.01hz, it's just that the air will stand still rather than moving (unless you also had a fan) so it will not be a full reproduction of the ultrasonics.
Infrasound is transmitted over long distances in water (whale songs). Elephants communicate on land using infrasound. It is transmitted as vibrations of the earth and house structures during an earthquake.
Infrasound is produced by engines (in industry and transport), pile drivers, and wind turbines.
Medicine considers long-term exposure to infrasound to a person harmful to health and psyche.
Infrasound is produced by engines (in industry and transport), pile drivers, and wind turbines.
Medicine considers long-term exposure to infrasound to a person harmful to health and psyche.
Thanks. To be clear then, it seems the displacement for a low frequency driver would increase by 4x for a 1/2 frequency input? For example if the excursion is 1" at 20 Hz
20 Hz = if 1" = 1x
10 Hz = 4x
5 Hz = 16x
2.5 Hz = 64x
1.25 Hz = 256x = 21 feet pk to pk
Some reversible fans would seem in order even at 1 Hz at least in free air.
20 Hz = if 1" = 1x
10 Hz = 4x
5 Hz = 16x
2.5 Hz = 64x
1.25 Hz = 256x = 21 feet pk to pk
Some reversible fans would seem in order even at 1 Hz at least in free air.