I've no idea of the T/S parameters of my dumpster sub's driver. It's in a 16 litre ported cabinet tuned to 52hz. I like the sound the box produces. At high listening levels the driver behaves as expected. However, if I block the ports the driver readily hits Xmax.
Is this a Q thing?
Is this a Q thing?
Around the port tuning frequency, the port restricts the driver's movement. If you run a moderate-volume <40Hz tone through it, you'll almost certainly see excursion decrease as you block the port.
Chris
Chris
Don't know what behavior you expect from your dumpster sub's driver.
Don't whether you like the sound of a high Q factor, a lot of resonance and low system damping, or a low Q factor, well damped with little resonance damped.
Here is an example of the acoustical output of a ported 52Hz Fb 16 liter box (light grey) and the same sealed (black) both at a 6.5volt input level:
The high Q ported response has a lot more output above 35Hz, but some would find it "boomy".
The lower Q sealed response would sound "tighter" but having 6dB less output, may not be loud enough without running out of excursion.
The excursion of the 52Hz Fb is lower until below 40Hz, where the sealed box has less excursion and more output.
Cheap driver..
Art
I get that. I thought the suspension characteristics of the sealed cabinet would be more effective. However, the driver was removed from a cabinet with 25% less volume.
@weltersys As usual, insightful comments backed-up with data. However, the sub doesn't sound boomy. I have seven small subs (6.5 - 10") in my small apartment. In terms of music reproduction I rank it 2nd.
Looking at your graphs and discarding the irrelevant data we are left with the performance within the speaker's remit: 35-100hz. Within this duty cycle it would seem to perform well.
When it comes to a music program, and the absence of signal below 35hz, the response of the vented enclosure seems ideal.
Sidebar: I listen to UK Garage, Rnb, Hip-Hop. (I also have a bizarre penchant for Edvard Greig). I can tell the original source of an MP3 (CD or Vinyl) not by listening but observing the driver. Raising the question: How much time, money, and effort is spent reproducing inaudible sounds?
Looking at your graphs and discarding the irrelevant data we are left with the performance within the speaker's remit: 35-100hz. Within this duty cycle it would seem to perform well.
When it comes to a music program, and the absence of signal below 35hz, the response of the vented enclosure seems ideal.
Sidebar: I listen to UK Garage, Rnb, Hip-Hop. (I also have a bizarre penchant for Edvard Greig). I can tell the original source of an MP3 (CD or Vinyl) not by listening but observing the driver. Raising the question: How much time, money, and effort is spent reproducing inaudible sounds?
Hi,
there is another recent thread with similar concern, member @Hörnli brought up phenomenon of coil jumping out from the cap / hitting back plate which seems to have to do with non-linear Bl(x). This Klippel paper briefly mentions it: https://www.klippel.de/fileadmin/kl...s/Aging of loudspeaker suspension_Klippel.pdf
More about DC displacement and driver instability in these papers at least:
https://www.klippel.de/fileadmin/kl...speaker_performance_at_high_amplitudes_01.pdf
https://www.klippel.de/fileadmin/kl...Diagnosis_and_remedy_of_Nonlinearities_00.pdf
Why it happens on closed box and not on the reflex box, perhaps because the tuning happens to be so that excursion is limited around the frequency which would be prone for the jump out (driver Fs).
ps. On Hörnli thread there is speculation which tries to explain jump out bit different from Klippel papers (force affecting cone increasing when Bl drops due to current increasing more), but since Klippel has papers and is industry leader in the field then the details are likely in their papers. Did not read them fully though, perhaps it's there as well. Anyway, coil jump out happens due to non-linearities with the driver.
there is another recent thread with similar concern, member @Hörnli brought up phenomenon of coil jumping out from the cap / hitting back plate which seems to have to do with non-linear Bl(x). This Klippel paper briefly mentions it: https://www.klippel.de/fileadmin/kl...s/Aging of loudspeaker suspension_Klippel.pdf
More about DC displacement and driver instability in these papers at least:
https://www.klippel.de/fileadmin/kl...speaker_performance_at_high_amplitudes_01.pdf
https://www.klippel.de/fileadmin/kl...Diagnosis_and_remedy_of_Nonlinearities_00.pdf
Why it happens on closed box and not on the reflex box, perhaps because the tuning happens to be so that excursion is limited around the frequency which would be prone for the jump out (driver Fs).
ps. On Hörnli thread there is speculation which tries to explain jump out bit different from Klippel papers (force affecting cone increasing when Bl drops due to current increasing more), but since Klippel has papers and is industry leader in the field then the details are likely in their papers. Did not read them fully though, perhaps it's there as well. Anyway, coil jump out happens due to non-linearities with the driver.
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With no T/S parameters of your dumpster sub, the example shown was not what your sub does, it was to show the difference in "Q".
For all we know, your sub might be flat at 60Hz, and -3dB at 52Hz.
I chose speaker parameters of a sub I'd actually built for use in a little travel trailer.
I built it as 25L (gross volume) with a 33Hz Fb, the driver has a 4.5mm Xmax.
In real life, it's excursion won't go much past 6mm or so, not enough Bl(magnetic strength) to push the coil further, regardless of input power, of which I had little, the 10 watt amp (6.5V into 4ohms) could only push the driver to Xmax before it ran out of juice and sound like crap.
Comparing it to the 16L (17L gross) 52Hz Fb box, you can see that I traded low frequency extension for upper output- the 52Hz Fb box would be useless below about 40Hz, the 33Hz Fb makes it to 30Hz. I decided that 1/3 octave extension was worth the loss for the application.
I don't spend any time, money, or effort on reproducing inaudible sound, but have no problem hearing sounds down as low as 10Hz at an SPL lower than I begin to feel them.
Each DIY builder can decide their priorities based on what's important to their own music/FX preferences.
Art