subsonic filter
500 Watt CAFz'r
Joined: Oct 2004
Posts: 870
^^^^yep
Most music recorded today has quite a bit of information below 30 hz. 50 Cent, et al, seems to be the norm in music (Ok, I use the term music very generally), and the recording equipment used will definately pick up the infrasonic resonances of the studio.
When I dial in the filter on my systems, I usually play a test tone a few hz below the tuned frequency, and watch the sub as I dial up the frequecy. When the excursion starts to lessen, thats where I leave it set. I've found that setting by eye ensures that none of the box's audible tones are reduced
And no...it's not a placebo effect. There is quite an audible difference, subtle perhaps at first, but certainly perceptible.
However, my challenge still stands....try it for a week, and then remove it. Its a small price to pay, and the gains are audible.
Most music recorded today has quite a bit of information below 30 hz. 50 Cent, et al, seems to be the norm in music (Ok, I use the term music very generally), and the recording equipment used will definately pick up the infrasonic resonances of the studio.
When I dial in the filter on my systems, I usually play a test tone a few hz below the tuned frequency, and watch the sub as I dial up the frequecy. When the excursion starts to lessen, thats where I leave it set. I've found that setting by eye ensures that none of the box's audible tones are reduced
And no...it's not a placebo effect. There is quite an audible difference, subtle perhaps at first, but certainly perceptible.
However, my challenge still stands....try it for a week, and then remove it. Its a small price to pay, and the gains are audible.
Guest
Posts: n/a
Hmm, could someone please put a 50 Cent CD on an RTA? I would doubt there is much info below 45-50 Hz on one of his CD's.
There was a test in a magazine a few years ago, and there was no appreciable information below 40-50 Hz in any mainstream recordings. The only ones that really had any was a Pipe Organ and one with a recorded thunderstorm.
There was a test in a magazine a few years ago, and there was no appreciable information below 40-50 Hz in any mainstream recordings. The only ones that really had any was a Pipe Organ and one with a recorded thunderstorm.
500 Watt CAFz'r
Joined: Oct 2004
Posts: 870
Then what info is making the subs oscilate? And why can I push them harder without distortion when using a filter?
Why is there less excusion with a filter that does nothing above 20hz?
I'd be interested to see the results displayed on a 'scope with a 20hz tone and a 60hz tone played simultaneously with a filter and without, on a decent sub tuned to 30hz.
I'd bet that the 60hz tone will occillate from 58 to 62 hz, at 20 cycles per second.(just a guess...I didn't do the math).
Why is there less excusion with a filter that does nothing above 20hz?
I'd be interested to see the results displayed on a 'scope with a 20hz tone and a 60hz tone played simultaneously with a filter and without, on a decent sub tuned to 30hz.
I'd bet that the 60hz tone will occillate from 58 to 62 hz, at 20 cycles per second.(just a guess...I didn't do the math).
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Posts: n/a
How does something oscillate from 58 to 62 Hz at 20 cycles? Are you aware that the defination of Hz is how many times it 'oscillates' per second.
And I am not talking about testing test tones. I know there is 20 Hz energy in a 20 Hz tone, what I want to know is if there is any sub 40 Hz energy in a 50 Cent song. And I don't mean that a sub should be hooked up. Just feed the decks outputs straight into the RTA.
And I am not talking about testing test tones. I know there is 20 Hz energy in a 20 Hz tone, what I want to know is if there is any sub 40 Hz energy in a 50 Cent song. And I don't mean that a sub should be hooked up. Just feed the decks outputs straight into the RTA.
500 Watt CAFz'r
Joined: Dec 2000
Posts: 952
A speaker will oscillate when the amplifier driving it can't control it, and when the amplifier is recieving a signal causing it to make the speaker oscillate. There are other factors which may be responsible, but it boils down to "back to the 'ol drawing board".
500 Watt CAFz'r
Joined: Oct 2004
Posts: 870
If I'm as bored today as I was yesterday, I'll do that, and take some pics. I don't think the filters in the RTA are precise enough to distinguish between 18 and 22 hz tones tho, but we'll see if the bottom light comes on.
If you've ever heard an emergency vehicle pass by at 70k with the siren going, you'll hear a tonal shift when it passes you. The siren's output didn't lower in frequency. The relative speeds of you (0), and the siren's (70) causes you to hear a compression of the wavelengths as it's approaching, and an expansion as it's leaving, of about 7%.
The same thing occurs when a tone is played from a moving source (woofer moving 1" at 20 cycles)
Thats about 70kph average speed, relative to the listener.
So as the woofer is moving out, the 60hz tone would rise by around 7% to 64hz, and as it's moving in, it would drop to 56hz, 20 times per second.
The sound will be heard as a mixture of tones with an average of 60.
That's gotta make a difference, if there is any information on the source.
Any instability in the system's power supply will also cause low frequency oscillation that would have an affect on the final sound.
Regardless of the cause, removal of inaudible tones are better removed, as most ported boxes just sound better and handle more power with a filter.
[ September 20, 2005, 03:59 AM: Message edited by: Car Trek ]
If you've ever heard an emergency vehicle pass by at 70k with the siren going, you'll hear a tonal shift when it passes you. The siren's output didn't lower in frequency. The relative speeds of you (0), and the siren's (70) causes you to hear a compression of the wavelengths as it's approaching, and an expansion as it's leaving, of about 7%.
The same thing occurs when a tone is played from a moving source (woofer moving 1" at 20 cycles)
Thats about 70kph average speed, relative to the listener.
So as the woofer is moving out, the 60hz tone would rise by around 7% to 64hz, and as it's moving in, it would drop to 56hz, 20 times per second.
The sound will be heard as a mixture of tones with an average of 60.
That's gotta make a difference, if there is any information on the source.
Any instability in the system's power supply will also cause low frequency oscillation that would have an affect on the final sound.
Regardless of the cause, removal of inaudible tones are better removed, as most ported boxes just sound better and handle more power with a filter.
[ September 20, 2005, 03:59 AM: Message edited by: Car Trek ]
500 Watt CAFz'r
Joined: Oct 2004
Posts: 870
^^^^K...my bad math!
The sub would only be moving at about 4kph, not 70, which means the tone shift would be about .4%
the oscillation would be from 59.6 to 60.4hz.
Think I forgot to convert inches to feet.
Anyone know how to calculate the peak speed of the cone at 20hz with 1' excursion?
The sub would only be moving at about 4kph, not 70, which means the tone shift would be about .4%
the oscillation would be from 59.6 to 60.4hz.
Think I forgot to convert inches to feet.
Anyone know how to calculate the peak speed of the cone at 20hz with 1' excursion?
500 Watt CAFz'r
Joined: Oct 2004
Posts: 870
It would appear that the blue sections are the volume, with the lowest tones on the left (seems to be quite a bit of info at the furthest left of the screen).
Care to comment Jmac?
Been thinking a bit more, and perhaps the "oscillating" tones would actually give a flatter frequency response as the standing waves in the vehicle would be moving around.
I have a test album somewhere for setting up home EQs that has a warble effect on each tone, to overcome the room's standing waves.
Gotta love the topics that make you stretch the brain.
Care to comment Jmac?
Been thinking a bit more, and perhaps the "oscillating" tones would actually give a flatter frequency response as the standing waves in the vehicle would be moving around.
I have a test album somewhere for setting up home EQs that has a warble effect on each tone, to overcome the room's standing waves.
Gotta love the topics that make you stretch the brain.
