Hello, i've recently finished building subwoofer box, but when i started measuring and listening, some problems became obvious, and i have no idea how to fix them.
I'm using URAL BULAVA 12 V.2, which is 12 inch driver with the following specs:
Fs = 26.9 hz
Vas = 45 l
Xmax = 28 mm
I've built small box for it some 1 year ago. This enclosure proved to be really good up until high levels of volume, then it starts to make cracking noise with every movement of driver.
New sub box is much worse, it makes cracking noise with any level of volume. Also new box have nasty resonance at about 160 hz.
Subs are both designed for corner use. And i have really small space with about 45 cm width, 45 cm length, but up to 1.3 m height. It is going to be used on table, so i need to keep driver low.
I was unhappy with old sub because it could not play loud without crackling noise and is too big now.
I wanted new sub to be smaller, but higher, driver pointed at the center of the square room and more internal box volume so it would produce a little more bass at frequencies lower than 50 hz, which it did.
Old sub is made of MDF(16mm), 34 liters without driver, new - of plywood (21mm), 72 liters without driver, both are sealed boxes with screws, glue and plasticine with no holes that i could find.
I'm almost positive xmax is not the case here, because i can see that driver isnt moving that far and it crackles on any frequency, not just super lows.
I tested driver without enclosure and it was working ok, i.e. no cracking noise, so probably not the case either.
I tried damping in old sub box with insulation, but it only made matters worse, so i used none in new box...
Maybe internal volume was too big, idk.
So, point me in right directions.
I need box that can handle high levels of volume without distorting sound more than driver, i.e. crackling noise.
And driver must be pointed at the center of the square room while standing in corner.
What to do with new sub box:
is it fixable?
if yes, then what i can do to fix it?
If this box is not fixable then recommend me some guides or something how to make nice triangle (or more complex, just so it would fit in triangle corner) subwoofer box.
Maybe hint with dimensions?
I'm using URAL BULAVA 12 V.2, which is 12 inch driver with the following specs:
Fs = 26.9 hz
Vas = 45 l
Xmax = 28 mm
I've built small box for it some 1 year ago. This enclosure proved to be really good up until high levels of volume, then it starts to make cracking noise with every movement of driver.
New sub box is much worse, it makes cracking noise with any level of volume. Also new box have nasty resonance at about 160 hz.
Subs are both designed for corner use. And i have really small space with about 45 cm width, 45 cm length, but up to 1.3 m height. It is going to be used on table, so i need to keep driver low.
I was unhappy with old sub because it could not play loud without crackling noise and is too big now.
I wanted new sub to be smaller, but higher, driver pointed at the center of the square room and more internal box volume so it would produce a little more bass at frequencies lower than 50 hz, which it did.
Old sub is made of MDF(16mm), 34 liters without driver, new - of plywood (21mm), 72 liters without driver, both are sealed boxes with screws, glue and plasticine with no holes that i could find.
I'm almost positive xmax is not the case here, because i can see that driver isnt moving that far and it crackles on any frequency, not just super lows.
I tested driver without enclosure and it was working ok, i.e. no cracking noise, so probably not the case either.
I tried damping in old sub box with insulation, but it only made matters worse, so i used none in new box...
Maybe internal volume was too big, idk.
So, point me in right directions.
I need box that can handle high levels of volume without distorting sound more than driver, i.e. crackling noise.
And driver must be pointed at the center of the square room while standing in corner.
What to do with new sub box:
is it fixable?
if yes, then what i can do to fix it?
If this box is not fixable then recommend me some guides or something how to make nice triangle (or more complex, just so it would fit in triangle corner) subwoofer box.
Maybe hint with dimensions?
Attachments
Mishaiger,
1) The suspension and magnet structure of the URAL BULAVA 12 V.2 do not look capable of a 28mm Xmax. It may have a (one way) Xmech/Xlim of 28mm, the mechanical limitations being either the suspension or voice coil former hitting the back plate. You can determine which is the limit by pushing the driver by hand till the suspension won't move further, or you hear the voice coil former "click" when hitting the back plate.
2) "Cracking noise with every movement of driver" would imply the driver has some mechanical damage.
3) A damaged driver should make similar noise in open air or any size box. That said, a warped baffle can bend the driver frame enough that a slight misalignment or dragging coils become worse, one (or both) boxes may have warped baffles.
4) As your driver probably has no more than 14mm Xmax, you may be expecting 6dB more than it could deliver. A smaller box will require more power to reach Xmax, that power may have partially burnt the voice coil, some coils may be dragging.
5) Description sounds like dragging coils, which sound bad at any level. Try pushing the driver by hand, both evenly and on one side to see if there is a scraping sound in, then again out of the box. Test voice coil DCR (dc resistance with ohmeter) and slow sine wave sweep.
6) Could be #3 problem.
7) The problem, other than possibly #3, does not sound like a box problem.
Good luck narrowing down what is causing the noise!
Art
Attachments
weltersys,
Unfortunately i dont have ohmmeter, i think this can be done in REW, but it requires some calibration and reasonably good microphone input.
I see your calculator showing SPL on 1 meter, but my measurement is about 3 cm from driver. That being said, when i measure at about 1 m then that cracking sound appears at about 95 db volume.
I tried pushing the driver by hand until i could no longer push it. It did not produce any sound right until i hit the bottom, and i cant describe it as cracking.
You may be right about xmax limiting at higher volumes. I then tested this driver in free air with the same power from amplifier when cracking sound is obvious in old box. And i could only hear little amount of bass, motor/engine noise (not cracking) and thats it.
But lets return to the box.
I tested this very same driver in these two enclosures (pictures show second identical subwoofer driver and box. but i tested this driver in both boxes) and in old box everything is roughly speaking fine, then i change to new box and everything is awful, then again switching to old and all is fine again.
So i'm quite sure that the problem is in the box, not driver.
Unfortunately i dont have ohmmeter, i think this can be done in REW, but it requires some calibration and reasonably good microphone input.
I see your calculator showing SPL on 1 meter, but my measurement is about 3 cm from driver. That being said, when i measure at about 1 m then that cracking sound appears at about 95 db volume.
I tried pushing the driver by hand until i could no longer push it. It did not produce any sound right until i hit the bottom, and i cant describe it as cracking.
You may be right about xmax limiting at higher volumes. I then tested this driver in free air with the same power from amplifier when cracking sound is obvious in old box. And i could only hear little amount of bass, motor/engine noise (not cracking) and thats it.
But lets return to the box.
I tested this very same driver in these two enclosures (pictures show second identical subwoofer driver and box. but i tested this driver in both boxes) and in old box everything is roughly speaking fine, then i change to new box and everything is awful, then again switching to old and all is fine again.
So i'm quite sure that the problem is in the box, not driver.
" So i'm quite sure that the problem is in the box, not driver. "
It seems clear that the problem is of the construction then.
The internal pressures inside a subwoofer enclosure are very high, especially if it is a sealed enclosure. I built two boxes similar to the new one that you have made, maybe it will help you to take a look at the reinforcements that I was adding as I received advice. What started as a quick and easy construction ended up being a slow and complex process.
I would emphasize the union of the vertex that is in blue.
https://www.diyaudio.com/forums/sub...o-18-prism-sealed-150-liters.html#post5585728
It seems clear that the problem is of the construction then.
The internal pressures inside a subwoofer enclosure are very high, especially if it is a sealed enclosure. I built two boxes similar to the new one that you have made, maybe it will help you to take a look at the reinforcements that I was adding as I received advice. What started as a quick and easy construction ended up being a slow and complex process.
I would emphasize the union of the vertex that is in blue.
https://www.diyaudio.com/forums/sub...o-18-prism-sealed-150-liters.html#post5585728