Music modulation with 20Hz effects

Bazukaz · 24th March 2006, 05:05 PM

Hi,
I have a DIY 3-way speaker system and a "gainclone" DIY amplifier.
The amp has no capacitors at its input.

Today i tried to mudulate a music signal with 20Hz sinewave.I used
spectraPLUS as a generator and Windows Media player as a sound player.The output was set at moderate listening level. The sound changed A LOT when a 20Hz signal was applied.It was quiter and more distorted.
How could this be explained ?
Note that other tones , like 30Hz , does the same effect.

Regards,
Lukas.

angsuman · 24th March 2006, 07:11 PM

What you were hearing is an extreme case of doppler distortion (someone correct me if i'm wrong here). I tried that once when i ran music through a 6in woofer and then modulated with a 20hz tone. At 30hz the cone movement is probably not even to facilliate doppler distortion. The sound is like talking into a fan.

Bazukaz · 24th March 2006, 08:06 PM

Another test i did was to set 1Hz tone ... The cone was moving without sound.Then i played some music ... The music volume was modulated by cone movement.I think it might be caused by loadspeakers , which have non-linear magnetic field and mechanical force ...

maxro · 24th March 2006, 10:24 PM

Quote:

Originally posted by angsuman
What you were hearing is an extreme case of doppler distortion (someone correct me if i'm wrong here). I tried that once when i ran music through a 6in woofer and then modulated with a 20hz tone. At 30hz the cone movement is probably not even to facilliate doppler distortion. The sound is like talking into a fan.

Actually, it's intermodular distortion (IMD). Doppler distortion is from a moving sound source, ie a train's whistle sounds higher pitched when approaching than when moving away from you.

Max

pinkmouse · 24th March 2006, 11:27 PM

Personally I would have thought it would be more likely that the PSU can't cope with the demands put on it, or the two superimposed waves are driving the amp into clipping.

darkfenriz · 24th March 2006, 11:36 PM

Quote:

modulation

You mean you modulated envelope (AM) or multiplied with 20 Hz (DSB-SC)? Or just added and played together?

Bazukaz · 25th March 2006, 08:28 AM

Hi,
I simply played together. PSU cannot be the cause , because volume levels were low.

Regards,
Lukas.

AndrewT · 25th March 2006, 09:10 AM

Hi,
the sound volume level may have been low but the voltage drive to the speaker could be very high.

You just could not hear the 1Hz or 20Hz tone.

The normal music signal would be riding on the low frequency waveform.

I support Pinks thought. Clipping or severe PSU rail droop.

Bazukaz · 25th March 2006, 10:08 AM

Hi,
You were right - at even lower listening levels , the effect does not show up.However , distortion increase can be heard - probably showing that loadspeakers suffer from high IMD.

About the doppler effect - there is an article : http://sound.westhost.com/doppler.htm

soongsc · 25th March 2006, 12:58 PM

Possibly larger cone area with lower travel provides less doppler effects. I also think one should not just consider music effects just by simple signals alone. When we hear bass, we listen in terms of relationship between the initial transient and the continued resonance to determine how realistic sound is produced.

24th March 2006, 05:05 PM	#1
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	Music modulation with 20Hz effects Hi, I have a DIY 3-way speaker system and a "gainclone" DIY amplifier. The amp has no capacitors at its input. Today i tried to mudulate a music signal with 20Hz sinewave.I used spectraPLUS as a generator and Windows Media player as a sound player.The output was set at moderate listening level. The sound changed A LOT when a 20Hz signal was applied.It was quiter and more distorted. How could this be explained ? Note that other tones , like 30Hz , does the same effect. Regards, Lukas.

24th March 2006, 11:27 PM	#5
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Personally I would have thought it would be more likely that the PSU can't cope with the demands put on it, or the two superimposed waves are driving the amp into clipping. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

25th March 2006, 09:10 AM	#8
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the sound volume level may have been low but the voltage drive to the speaker could be very high. You just could not hear the 1Hz or 20Hz tone. The normal music signal would be riding on the low frequency waveform. I support Pinks thought. Clipping or severe PSU rail droop. __________________ regards Andrew T.

25th March 2006, 12:58 PM	#10
soongsc diyAudio Member Join Date: Mar 2005 Location: Taiwan	Possibly larger cone area with lower travel provides less doppler effects. I also think one should not just consider music effects just by simple signals alone. When we hear bass, we listen in terms of relationship between the initial transient and the continued resonance to determine how realistic sound is produced. __________________ Hear the real thing!

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24th March 2006, 07:11 PM	#2
angsuman diyAudio Member Join Date: Mar 2005 Location: Las Vegas NV	What you were hearing is an extreme case of doppler distortion (someone correct me if i'm wrong here). I tried that once when i ran music through a 6in woofer and then modulated with a 20hz tone. At 30hz the cone movement is probably not even to facilliate doppler distortion. The sound is like talking into a fan.

24th March 2006, 08:06 PM	#3
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	Another test i did was to set 1Hz tone ... The cone was moving without sound.Then i played some music ... The music volume was modulated by cone movement.I think it might be caused by loadspeakers , which have non-linear magnetic field and mechanical force ...

25th March 2006, 08:28 AM	#7
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	Hi, I simply played together. PSU cannot be the cause , because volume levels were low. Regards, Lukas.

25th March 2006, 10:08 AM	#9
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	Hi, You were right - at even lower listening levels , the effect does not show up.However , distortion increase can be heard - probably showing that loadspeakers suffer from high IMD. About the doppler effect - there is an article : http://sound.westhost.com/doppler.htm

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