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Factory recommended sub freq range
Factory recommended sub freq range
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Old 31st August 2019, 11:11 AM   #1
Augusts is offline Augusts  Latvia
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Default Factory recommended sub freq range

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
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Old 31st August 2019, 11:23 AM   #2
chris661 is online now chris661  United Kingdom
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Are you sure the box is tuned to 30Hz?
Going a little below Fs is generally okay, but does depend on a lot of factors.

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Old 31st August 2019, 11:35 AM   #3
Augusts is offline Augusts  Latvia
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According to box and port size, yes. But I have not had the chance to measure the impedance, that I should probably do.
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Old 31st August 2019, 09:48 PM   #4
Augusts is offline Augusts  Latvia
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I took the measurement, it shows that everything is as should be.

Click the image to open in full size.




I decided to make the box smaller and tune the subs higher. A -3db of 35Hz
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Old 1st September 2019, 02:51 AM   #5
Brian Steele is offline Brian Steele  Grenada
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That mini peak just after the main upper peak suggests that perhaps everything is not as it should be. That suggests some sort of resonance is happening at that frequency, probably box-related. Is the box properly braced?
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Old 1st September 2019, 03:14 PM   #6
bentoronto is online now bentoronto  Canada
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Factory recommended sub freq range
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.
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Last edited by bentoronto; 1st September 2019 at 03:21 PM.
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Old 4th September 2019, 02:17 PM   #7
Augusts is offline Augusts  Latvia
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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.
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Old 4th September 2019, 09:36 PM   #8
Brian Steele is offline Brian Steele  Grenada
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Quote:
Originally Posted by Augusts View Post
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.
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Old 4th September 2019, 09:46 PM   #9
Augusts is offline Augusts  Latvia
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Quote:
Originally Posted by Brian Steele View Post
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
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Old 4th September 2019, 10:00 PM   #10
Augusts is offline Augusts  Latvia
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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
I seem stupid, but I'm not that stupid actually.
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