I have done some experimenting with dsp subwoofers thru the years .
The latest has been done with Genelec SAM monitors and the 7350 subwoofers in an ordinary livingroom.
Before this I have tested one, two or four dsp subwoofer in mono and in stereo. With 4 subwoofers ( 2 in front of the listener and two behind listening position ) the measurements from listening position looks very good, but the sound is much worse than only two stereo subwoofers put in the front.
The theory is saying that one cant hear were the subwoofers are below 200 Hz . With music I find this to be not true . Even with a very steep dsp crossover at 200 Hz and using only one sub, I can easily hear that there is something wrong in the music with only one subwoofer.
In crossover design one often follows the rule of max 1/4 wavelenght distanse from the drivers regarding their crossover frequency If using a 4:th order Linkwitz Riley crossover.
One example is this: a crossover in a two way loudspeaker at 2 kHz . The wavelengt at 2 kHz is about 17 cm . 1/4 of this is 4,25 cm . The tweeter must be very closed mounted to the bassdriver in this 2-way loudspeaker, If its gonna sound as only one driver.
They say that below the rooms schroeder frequency ( about 250 Hz ) the sound cant be spatially recognized anymore .
I find that this is true with sine-tones but not true when listening with music.
The first arriving sound from the speakers are the most important - attenuating later arriving sounds about -10 dB , also below the schroeder frequency. This cant be shown in measurements, but it happens in the listener brain in the listening position when listening to real music.
From this testing, I have drawn the following conlusion :
1. Stereo subwoofers are the best. The nearer the subs are from each front L/R speaker, the higher in frequency one can cross them.
Ofcourse I mean both LP and HP filtering. This is ( in my opinion ) also true with very steep crossovers ( 48 db/oct) .
Mono coupled subwoofers placed near each speaker dont sound as good as stereo coupled subwoofers.
2. If using only one subwoofer with music - one should follow the 1/4 wavelenght rule according the distance between the frontspeakers and the subwoofer . Crossing at 100 Hz with only one subwoofer gives you = 3,43 meter wavelengt/4 = 85 cm . The subwoofer should not be placed apart from any of the L or R speaker longer than 85 cm, to avoid worse sound.
And, If the crossover is set at 50 Hz , the distance between the single subwoofer and the front L or R can be up to 170 cm without sounding unnatural.
I find this very true when listening to music.
With stereo subwoofers, because of this, one can cross them much higher because they can be put much nearer each L and R front speaker. 100 Hz in this case can be done if each subwoofer are placed very near each frontspeaker.
Whats youre experience about this ? Are mono subwoofers good enough ? Can you cross a monosubwoofer at 100 Hz and not hearing that something is wrong with the music experience ? Does 4 subwoofers placed in corners far away from the main speakers sound good with music, or are the music experience much worse ?
The latest has been done with Genelec SAM monitors and the 7350 subwoofers in an ordinary livingroom.
Before this I have tested one, two or four dsp subwoofer in mono and in stereo. With 4 subwoofers ( 2 in front of the listener and two behind listening position ) the measurements from listening position looks very good, but the sound is much worse than only two stereo subwoofers put in the front.
The theory is saying that one cant hear were the subwoofers are below 200 Hz . With music I find this to be not true . Even with a very steep dsp crossover at 200 Hz and using only one sub, I can easily hear that there is something wrong in the music with only one subwoofer.
In crossover design one often follows the rule of max 1/4 wavelenght distanse from the drivers regarding their crossover frequency If using a 4:th order Linkwitz Riley crossover.
One example is this: a crossover in a two way loudspeaker at 2 kHz . The wavelengt at 2 kHz is about 17 cm . 1/4 of this is 4,25 cm . The tweeter must be very closed mounted to the bassdriver in this 2-way loudspeaker, If its gonna sound as only one driver.
They say that below the rooms schroeder frequency ( about 250 Hz ) the sound cant be spatially recognized anymore .
I find that this is true with sine-tones but not true when listening with music.
The first arriving sound from the speakers are the most important - attenuating later arriving sounds about -10 dB , also below the schroeder frequency. This cant be shown in measurements, but it happens in the listener brain in the listening position when listening to real music.
From this testing, I have drawn the following conlusion :
1. Stereo subwoofers are the best. The nearer the subs are from each front L/R speaker, the higher in frequency one can cross them.
Ofcourse I mean both LP and HP filtering. This is ( in my opinion ) also true with very steep crossovers ( 48 db/oct) .
Mono coupled subwoofers placed near each speaker dont sound as good as stereo coupled subwoofers.
2. If using only one subwoofer with music - one should follow the 1/4 wavelenght rule according the distance between the frontspeakers and the subwoofer . Crossing at 100 Hz with only one subwoofer gives you = 3,43 meter wavelengt/4 = 85 cm . The subwoofer should not be placed apart from any of the L or R speaker longer than 85 cm, to avoid worse sound.
And, If the crossover is set at 50 Hz , the distance between the single subwoofer and the front L or R can be up to 170 cm without sounding unnatural.
I find this very true when listening to music.
With stereo subwoofers, because of this, one can cross them much higher because they can be put much nearer each L and R front speaker. 100 Hz in this case can be done if each subwoofer are placed very near each frontspeaker.
Whats youre experience about this ? Are mono subwoofers good enough ? Can you cross a monosubwoofer at 100 Hz and not hearing that something is wrong with the music experience ? Does 4 subwoofers placed in corners far away from the main speakers sound good with music, or are the music experience much worse ?
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