Hi,
Not true. Given the compact box, say 20L, and say a target of 50Hz
Fbox with a Qbox of 0.7 what really matters is the cone mass and
motor. If the driver has Vas 60L and Fs 25Hz, the air load dominates.
Trouble is the driver Qts must be 0.35 and you can vent it in 40L.
The same driver with Vas =240L, Fs =12.5Hz and Qts =0.175,
will perform almost the same in a 20L sealed box but will be a
general disaster area in a 40L vented box below vent resonance.
It is true very low Qts, very high VAS, very low Fs drivers for
sealed only don't really exist, but did they ever really exist ?
Cone sag and such issues preclude very low Fs, very high Vas.
rgds, sreten.
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It's a sealed back midrange with a resonance near 300Hz. Because the back is sealed it doesn't matter what size box you put it in. In this case, the "Vas" isn't even really Vas, it is Vas*Vb/(Vas+Vb) - the Vb is the sealed back volume, and the actual Vas is not specified....
start a new thread if you want to understand this more.
start a new thread if you want to understand this more.
Only in the sense that it will make the box bigger since the weaker the motor, the more box compliance ideally required and vice versa, ie. in general, the effective Qts [Qts'] dominates cab net volume [Vb].
One of several basic vented box formulas used over the decades: Vb = 20*Vas*Qts'^3.3
Qts' = Qts + any added series resistance: mh-audio.nl - Home
GM
One of several basic vented box formulas used over the decades: Vb = 20*Vas*Qts'^3.3
Qts' = Qts + any added series resistance: mh-audio.nl - Home
GM
Series resistance does not affect Vas.
As GM states in a rather cryptic way, series resistance raises Qes and Qts and will generally require a bigger box.
Right, my 515Bs all have a ~0.2 Qts and some earlier units can have as low as a 0.16 Qts, so it takes a lot of series resistance to get Qt up to a ~0.403 Qts' for a Vb = Vas, Fb = Fs max flat alignment and why the norm in their heyday were high output impedance tube amps with up to 20 ohms of adjustable tone controls.
GM
To rephrase what Ron E said, Vas is just determined by the suspension (spider + surround).
Generally I'd say adding series resistance is not a good way to achieve things, to me it indicates the driver is not the right driver.
Yea, I was looking at some full rangers like the audio nirvana classic 5". Raising the qes you can easily get sealed -3db in the 70-80 hz range, which is decent, plus the other benefits of sealed. I always use equalizer APO anyways so dealing with the changes to frequency response wouldn't be a big deal, but I haven't tried it.
You mean this thing Audio Nirvana Classic 5 Fullrange Speaker Driver
I presume. So in a small sealed box, if you made the Qts 0.7, the Fc becomes like 150 or whatever-and it seems to me what you want to do is raise the Q so you get the Q you want without raising Fc. Hmmm. Maybe...sticking a resistor in series just sticks in my engineering sensibilities, since it wastes power and my gut feel is "it doesn't really work like that" though I cannot definitively say that is so because it's a long time since I thought about doing that.
It becomes kinda sorta like a high output impedance tube amp, screwing up the frequency response, and around resonance screwing it up in a dynamic way since the Thiele-Small parameters change with the drive signal magnitude. It would also reduce the whole sensitivity since you're padding down the whole speaker. But it is easy enough to try as an experiment.
I presume. So in a small sealed box, if you made the Qts 0.7, the Fc becomes like 150 or whatever-and it seems to me what you want to do is raise the Q so you get the Q you want without raising Fc. Hmmm. Maybe...sticking a resistor in series just sticks in my engineering sensibilities, since it wastes power and my gut feel is "it doesn't really work like that" though I cannot definitively say that is so because it's a long time since I thought about doing that.
It becomes kinda sorta like a high output impedance tube amp, screwing up the frequency response, and around resonance screwing it up in a dynamic way since the Thiele-Small parameters change with the drive signal magnitude. It would also reduce the whole sensitivity since you're padding down the whole speaker. But it is easy enough to try as an experiment.
Right, trading efficiency for a wider effective bandwidth [BW], so EQ can only do so much before running out of power handling.
GM
Using series resistance to change impedance lets you use drivers with powerful magnets and light cones in alignments that wouldn't normally suit them. Even using an over damped full ranger in an open baffle. I'm assuming you get the dynamics and detail. A lot of high q drivers have heavier cones or somewhat weak motors.
I wouldn't mind trying it and audio nirvana classic, maybe with a ribbon tweeter on the side. But I don't have room for any more speakers.
Yea the shorter xmax limits max volume, or requires a sub.
I wouldn't mind trying it and audio nirvana classic, maybe with a ribbon tweeter on the side. But I don't have room for any more speakers.
Yea the shorter xmax limits max volume, or requires a sub.
Hi all, nice question and I just came here to extend my knowledge about Vas.
So after reading all this through... can it be stated that for 2 same kind of animals (let's say two big woofers of the same size, both for vented box) a larger Vas is better ? Or a lower ? Or it doesn't matter at small signal but it does at large ? How shall we imagine it ?
What does it mean in practice if a 18" woofer has a bit higher Vas than a 21" ? (Both still OK for vented design).
Or when there are two 21" woofers of the same brand & line, one with neo magnets and the other with ferrite.. the neo one has a tiny little bit higher fs but almost half of the Vas of the ferrite one ?
So after reading all this through... can it be stated that for 2 same kind of animals (let's say two big woofers of the same size, both for vented box) a larger Vas is better ? Or a lower ? Or it doesn't matter at small signal but it does at large ? How shall we imagine it ?
What does it mean in practice if a 18" woofer has a bit higher Vas than a 21" ? (Both still OK for vented design).
Or when there are two 21" woofers of the same brand & line, one with neo magnets and the other with ferrite.. the neo one has a tiny little bit higher fs but almost half of the Vas of the ferrite one ?
Ferrite is heavy and brittle, neo is susceptible to corrosion in humid environment...
You can get similar alignments, flat or non-flat, from both transducers. It's just the matter of play with Vb and port length.
I suppose that air in the enclosure could be more linear than speaker suspension, generally.
But if it could be audible, I do not know...
Someone from this forum has quoted Charles-Henry Delaleu formula: S=(Vb/Vas)/qts^2
"S" is an equivalent of Q for vented boxes.
You can get similar alignments, flat or non-flat, from both transducers. It's just the matter of play with Vb and port length.
I suppose that air in the enclosure could be more linear than speaker suspension, generally.
But if it could be audible, I do not know...
Someone from this forum has quoted Charles-Henry Delaleu formula: S=(Vb/Vas)/qts^2
"S" is an equivalent of Q for vented boxes.