Hi
I have on my hands some Faital Pro subwoofers. The factory recommends 35hz and up. Fs is 35Hz, model 18HP1030. I tuned the box to 30 Hz, thinking I could get it to play that low. After putting it in the test box - 35Hz is as low as it goes, then it starts to just move air. Could this be because it is not broken in, because it is a stiff speaker? Or are there other parameters that come into play that limits the low freq response?
A
I have on my hands some Faital Pro subwoofers. The factory recommends 35hz and up. Fs is 35Hz, model 18HP1030. I tuned the box to 30 Hz, thinking I could get it to play that low. After putting it in the test box - 35Hz is as low as it goes, then it starts to just move air. Could this be because it is not broken in, because it is a stiff speaker? Or are there other parameters that come into play that limits the low freq response?
A
Here we go again. A vague complaint about sound likely to be followed by many well-intentioned fix suggestions. It takes a lot of cone movement to hear low bass.
The impedance plot is quite coherent and helpful to see. I am assuming you have the passive crossover in there.
The BR tuning is fudged on the low side with benefits to the FR but maybe not to SQ. At the upper impedance peak, the port and the cone are pumping in unison. Below the tuned freq, they are pumping antagonistically (opposite phase) and so sound level is diminished.
The driver free air resonance is 95% of the story as far as low-end cut-off. With a driver at 35 Hz, you might get nice bass but you aren't going to get low bass.
In the Golden Age of woofers, 20 Hz was the target - in 1965. Today, power handling and destruction of your hearing by means of automobile sound systems is the target.... which leads to robust devices with high resonance.
The impedance plot is quite coherent and helpful to see. I am assuming you have the passive crossover in there.
The BR tuning is fudged on the low side with benefits to the FR but maybe not to SQ. At the upper impedance peak, the port and the cone are pumping in unison. Below the tuned freq, they are pumping antagonistically (opposite phase) and so sound level is diminished.
The driver free air resonance is 95% of the story as far as low-end cut-off. With a driver at 35 Hz, you might get nice bass but you aren't going to get low bass.
In the Golden Age of woofers, 20 Hz was the target - in 1965. Today, power handling and destruction of your hearing by means of automobile sound systems is the target.... which leads to robust devices with high resonance.
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The box was not braced, but the walls are 2cm thick and it was a low voltage measurement.
The woofer specs are totally off. The manufacturer indicates 35 Fs but in reality it was 45Hz. After break in it could probably be 42Hz?
At 30 Hz where the woofer was pumping air when I put my ear to the port opening, the sound was there.
But below 30Hz at about 25 - 20Hz there was bass again as it should be - not loud but it could be heard comparing to that at 30hz sine.
The woofer specs are totally off. The manufacturer indicates 35 Fs but in reality it was 45Hz. After break in it could probably be 42Hz?
At 30 Hz where the woofer was pumping air when I put my ear to the port opening, the sound was there.
But below 30Hz at about 25 - 20Hz there was bass again as it should be - not loud but it could be heard comparing to that at 30hz sine.
Bass below Fb (30 Hz for your design) is usually not any decent output level and because the driver is now unloaded, can lead to mechanical damage of the driver if you boost frequencies in that range.
I understand that.
The question was - why is there a gap at 30hz. I described the situation to illustrate that that even at 20 hz it had more output than at 30
Did you measured response curve with a mic to say it goes as low as 35 hz or do you say it from what you eared ? What/How did you test ? sin waves at low frequencies ? You mean you ear it at 35 Hz, and no more below ?
If it is the case, it seems pretty normal. Below 35 hz at reasonable level, with not a lot of distortion, there's not a lot of content "to ear". It need more level to be "feeled", and no more "eared". So, below 35hz, "sound" became pressure. I don't explain it perfectly right, with the good words, but you got the idea. Still, i maybe misinterpreted and understood the wrong question.
I can "ear" 20 hz. Measurement was done with a sine generator and my ears
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You are hearing the distortion products below 30 Hz where they can be well above 10%. But if you have a sub driver struggling to play 25 Hz, the partials at 50 Hz, 75 Hz, etc are vastly easier to hear.
While some might say they can tell 50 Hz from 25 HZ (really sure of that??*), they forget their hearing inserts fundamentals.
B
* a lot of folks blast double-bass notes at 80 Hz and think they have great bass
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