I find myself peering down at the extreme low end at times, how does it roll off, where does the response end (IB) at 10Hz alot of times. Depending on what I'm specifically looking for would prefer a nice low sloping low end with a higher knee than an abrupt phase shift and all is lost. Usable extension of your above example is exactly what I'd hope for. Nice
Hi,
I wish people would not just spout general nonsense.
Qts with Fs tells you a lot about driver. A number for Fs/Qts
tells you next to nothing unless you know what it means.
e.g. 20Hz and 0.5 gives you 40, 40Hz and 0.5 gives you 80,
however the type of cabinet either suit is not remotely affected
by the number - it alludes to the bass depth you can expect,
i.e. the former will simply go deeper by an octave if you
put them in similar tuned cabinets, e.g. Qbox = 0.7 sealed,
but it really doesn't matter, for any sort of boxes with
identical tunings the former will go an octave lower.
In sealed boxes the ratio of Fs to Qts remains constant.
e.g. for Qts = 0.35 and Fs = 30Hz, if tuned to sealed
Qbox = 0.7, then by definition Fbox will be 60Hz.
If Qts is very low, e.g. 0.175 and Fs = 30Hz,
then for Qbox = 0.7, Fbox becomes 120Hz.
FWIW for Qts =0.35 and Fs = 30Hz :
In a box = to Vas, Qb =0.5, Fb = 1.4*30Hz
and the response is 6dB down at Fb, 43Hz.
In a box = to 1/3 Vas, Qb = 0.7, Fb = 60Hz
and the response is 3dB down at Fb.
-6dB = 46Hz.
In a box = to 1/7 Vas, Qb = 1.0, Fb = 2.8*30Hz
and the response is 0dB down at Fb, 86Hz.
-6dB = 56Hz.
In a box = 1/15 Vas, Qb = 1.4, Fb = 120Hz
and the response is 3dB up at Fb.
-6dB = 75Hz.
rgds, sreten.
I wish people would not just spout general nonsense.
Qts with Fs tells you a lot about driver. A number for Fs/Qts
tells you next to nothing unless you know what it means.
e.g. 20Hz and 0.5 gives you 40, 40Hz and 0.5 gives you 80,
however the type of cabinet either suit is not remotely affected
by the number - it alludes to the bass depth you can expect,
i.e. the former will simply go deeper by an octave if you
put them in similar tuned cabinets, e.g. Qbox = 0.7 sealed,
but it really doesn't matter, for any sort of boxes with
identical tunings the former will go an octave lower.
In sealed boxes the ratio of Fs to Qts remains constant.
e.g. for Qts = 0.35 and Fs = 30Hz, if tuned to sealed
Qbox = 0.7, then by definition Fbox will be 60Hz.
If Qts is very low, e.g. 0.175 and Fs = 30Hz,
then for Qbox = 0.7, Fbox becomes 120Hz.
FWIW for Qts =0.35 and Fs = 30Hz :
In a box = to Vas, Qb =0.5, Fb = 1.4*30Hz
and the response is 6dB down at Fb, 43Hz.
In a box = to 1/3 Vas, Qb = 0.7, Fb = 60Hz
and the response is 3dB down at Fb.
-6dB = 46Hz.
In a box = to 1/7 Vas, Qb = 1.0, Fb = 2.8*30Hz
and the response is 0dB down at Fb, 86Hz.
-6dB = 56Hz.
In a box = 1/15 Vas, Qb = 1.4, Fb = 120Hz
and the response is 3dB up at Fb.
-6dB = 75Hz.
rgds, sreten.
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I find this interesting. Have been doing distortion tests on my experiment and can clearly hear third harmonic above 3% down low (18-80) with every increase in level as it rises to a max of upwards of 30%. Anything between the two is clearly audible to my ears, in fact anything even remotely near the 20th percentile is considered unusable, mostly due to the spectral shift, but indeed the grittiness of it, including out of band eg beyond the pass band. These tests have given me a bit to think about in what all the causes are, be it room, enclosure, driver and their interactions. That should read, yes, yes, yes, and Oh heck ya!
The big grin came after cutting the wood. This is the 2nd set, and they have been putting a big grin on my face for the last couple weeks:^D
dave
I agree with you about simulations:
Your simulation has f3 about 60 Hz, with good slow rollof below (low tuning frequency, I presume). Very nice.
but...
Simple vented box tables (Vance Dickason, table 2.9) gives almost the same, f3=58.6 Hz , with steep rollof below, though. Lower tuning with somewhat bigger vented box will be more similar to your example, but ML TL box has the advantage...
Bottom line: numbers alone do give some good information about low frequency behavior of the woofer.
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Have to agree to a point. It's not one or two sets of numbers, but the sum of the total and how they interact, with experience one can run with the numbers at a glance. Wisdom allows us this ability to weed the field without resorting to calculations. If we were to sim instead it takes little time more to determine if it's acceptable for the application. A good example of this is the required Xmax to achieve a given result. I can take most any small speaker and make it sound well enough down low, but if it doesn't have the excursion required, what is the point in doing simple calculations when a sim is required.
Nothing as it's normally a sealed back driver with a Qtc typically around 0.7-1.0, though seen some such as the [old] Vifa D27TG ? coated silk fabric dome with a Qtc down around ~0.4, a really 'sweet' sounding tweeter suitable for mating to a wide BW 12" around 1500 Hz such as the equally 'sweet' sounding Altec 414 when coupled to a matching impedance SET amp, a really nice [vintage] 2 way for folks not into HF compression horns.
GM
GM
Wrong. It's the Fs/Qts ratio that's an indication of how low a woofer will go.
A good rule of thumb is that, e.g., in a bass reflex enclosure, you can expect the bass to extend down to ~0.4*Fs/Qt.
So, for instance, if you have Fs = 40Hz, but Qt = 0.6, then you can have strong bass down to about 27Hz.
Define "quality". Qts is usually dominated by Qes, which in turn depends on magnet strength, moving mass and compliance.
A lower Qes, and hence lower Qts, will give you a more efficient woofer. But also, all else being equal, a more "damped" one, i.e. one with LESS bass.
Yes, you are trivializing too much. Sorry.
Again, what matters the most is the final overall damping, i.e., Fs/Qts, and not the individual Qts or Fs parameters. And, depending on the intended application, there is a range of "optimal" damping, and "more" isn't always "better".
Nope (see above).
Let's put it another way: the higher the Fs/Qts ratio, the less the resulting speaker unit behaves like a Woofer, and the more it start behaving like a mid-range
For an optimally (NOT maximally) damped woofer to be used in a bass-reflex box, I would personally aim for Fs/Qts = 80, more or less. Anything in between 60 and 100 would be good. But not much more, and not much less.
In the end, it all depends on what you want it to do.
Marco
EDIT: just realised this is a 4-year-old thread! Oh well...
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