DIY-ers,
I'm modelling a few enclosures for a sub, and it has been several years since I've been doing anything with loudspeakers so things are a bit rusty, could you help out a little?
XLS10 in a 30-liter closed box
F3 = 78Hz
Qtc = 0.30
If my mind is not playing tricks on me below F3 the slope should be 12db/oct, hence with a reduction in frequency by 1/2 the output should be -12db lower right? Now look at the below graphs.
BassBox 6 Pro tells me I'll only see a -6db reduction, I'm sure I'm missing something here, but I just don't see it. Anybody care to enlighten me?
Thanks,
Sander Sassen
http://www.hardwareanalysis.com
I'm modelling a few enclosures for a sub, and it has been several years since I've been doing anything with loudspeakers so things are a bit rusty, could you help out a little?
XLS10 in a 30-liter closed box
F3 = 78Hz
Qtc = 0.30
If my mind is not playing tricks on me below F3 the slope should be 12db/oct, hence with a reduction in frequency by 1/2 the output should be -12db lower right? Now look at the below graphs.
BassBox 6 Pro tells me I'll only see a -6db reduction, I'm sure I'm missing something here, but I just don't see it. Anybody care to enlighten me?
Thanks,
Sander Sassen
http://www.hardwareanalysis.com
Never mind, I overlooked the influence of Q, which is set far too low, as per the below explanation:
Qtc (closed boxes only) The system total Q. Usually Qtc should not be less than the total Q (Qts) of the driver. Many designers consider the optimum value for Qtc to be 0.707. Some commonly used Qtc values are listed below along with a description:
Qtc = 0.5 produces a “Critically Damped” closed-box response.
Qtc = 0.577 produces a “Bessel” or D2 closed-box response.
Qtc = 0.707 produces a “Butterworth” or B2 closed-box response.
The Qtc value is inversely proportional to the system damping. In other words, as the Qtc value is reduced, the system damping increases. Closed boxes with a lower Qtc value produce a “tighter” sound because they are damped more. You might conclude from this that a low Qtc (such as the critically damped 0.5 value) would often be preferred. However, this is not the case. To some listeners a low Qtc sounds a bit “thin” and they prefer a higher value—even as high as 1.0 or higher. Although Qtc values above 0.707 will produce a response bump at the system resonance frequency, the increased level produces a “warmer” sound which some prefer.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
Qtc (closed boxes only) The system total Q. Usually Qtc should not be less than the total Q (Qts) of the driver. Many designers consider the optimum value for Qtc to be 0.707. Some commonly used Qtc values are listed below along with a description:
Qtc = 0.5 produces a “Critically Damped” closed-box response.
Qtc = 0.577 produces a “Bessel” or D2 closed-box response.
Qtc = 0.707 produces a “Butterworth” or B2 closed-box response.
The Qtc value is inversely proportional to the system damping. In other words, as the Qtc value is reduced, the system damping increases. Closed boxes with a lower Qtc value produce a “tighter” sound because they are damped more. You might conclude from this that a low Qtc (such as the critically damped 0.5 value) would often be preferred. However, this is not the case. To some listeners a low Qtc sounds a bit “thin” and they prefer a higher value—even as high as 1.0 or higher. Although Qtc values above 0.707 will produce a response bump at the system resonance frequency, the increased level produces a “warmer” sound which some prefer.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
I'd certainly disagree that a Q of 0.707 (or even higher) is to be prefered. I agree with Martin Colloms that Qtc of 0.5 to 0.6 gives a much more realistic LF end, and is likely to be a much better interface with the bass enhancement in the listening room due to the 'room modes'.
High Q speakers aways remind me of a teenager showing off his car sound system; impressive but hardly qualifying to be called 'faithful to the original recording'!
High Q speakers aways remind me of a teenager showing off his car sound system; impressive but hardly qualifying to be called 'faithful to the original recording'!
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