Hello,
So i am struggling to get to grips with sealed speaker enclosure volume math.
I have read and read and some is starting to make sense, plus this little tool is proving a great help.
Speaker Box Enclosure Designer / Calculator
But what to do when Vas is less than Qts as in:
Vas = 0.9l
Qts = 1.04
FRS 8 - 8 Ohm | Visaton
or
Vas = 0.3l
Qts = 1.28
FRS 7 - 8 Ohm | Visaton
or did i miss something (probably)?
Many thanks in advance imk
So i am struggling to get to grips with sealed speaker enclosure volume math.
I have read and read and some is starting to make sense, plus this little tool is proving a great help.
Speaker Box Enclosure Designer / Calculator
But what to do when Vas is less than Qts as in:
Vas = 0.9l
Qts = 1.04
FRS 8 - 8 Ohm | Visaton
or
Vas = 0.3l
Qts = 1.28
FRS 7 - 8 Ohm | Visaton
or did i miss something (probably)?
Many thanks in advance imk
Looking at the linked page, the Qtc value specified defaults to 0.707
imk, perhaps you're concerned that Qtc (not Vas) is less than Qts?
Qtc cannot be lower than Qts. An enclosure will reduce damping and therefore result in a value higher value for Qtc than Qts.
Looking at the formulas GM provided, you can see that if (Qtc<Qts), then Qtc÷Qts would be less than 1. This would result in a negative number for alpha and consequently, a negative box volume.
imk, perhaps you're concerned that Qtc (not Vas) is less than Qts?
Qtc cannot be lower than Qts. An enclosure will reduce damping and therefore result in a value higher value for Qtc than Qts.
Looking at the formulas GM provided, you can see that if (Qtc<Qts), then Qtc÷Qts would be less than 1. This would result in a negative number for alpha and consequently, a negative box volume.
Vas and Qtc or Qts are just different things.
Vas is the volume of air that has the same compliance as the speaker's suspension.
Qts describes the resonance and is based on electrical and mechanical components. Qts is in free air.
Qtc describes the resonance when the driver is in a sealed box.
Fs describes resonance frequency in free air. Fc is in a box.
It might help if I describe what happens when you put a driver in a box. If the box is an infinite size, fs would not change. Qts would equal Qtc.
As the box gets smaller, fs will increase. Qtc will start to get higher than Qts. Fs and Qtc will continue to rise as the box gets smaller.
We sometimes try to acquire maximum flatness at the rolloff point. A Qtc of .707 is considered perfect. Anything higher then .707 will start to have a peak at Fc.
Also adding series resistance to a driver can increase Qts overall and should be considered if there is sufficient crossover resistance or high amplifier impedance.
Vas is the volume of air that has the same compliance as the speaker's suspension.
Qts describes the resonance and is based on electrical and mechanical components. Qts is in free air.
Qtc describes the resonance when the driver is in a sealed box.
Fs describes resonance frequency in free air. Fc is in a box.
It might help if I describe what happens when you put a driver in a box. If the box is an infinite size, fs would not change. Qts would equal Qtc.
As the box gets smaller, fs will increase. Qtc will start to get higher than Qts. Fs and Qtc will continue to rise as the box gets smaller.
We sometimes try to acquire maximum flatness at the rolloff point. A Qtc of .707 is considered perfect. Anything higher then .707 will start to have a peak at Fc.
Also adding series resistance to a driver can increase Qts overall and should be considered if there is sufficient crossover resistance or high amplifier impedance.
I missed the fact that Qts is higher than .707 for the drivers listed. You cannot have a Qts lower than Qts.
Drivers with a high Qts are usually meant for open baffle use or enough sealed box volume that Qtc does not get higher than maybe 1.5.
Drivers with a high Qts are usually meant for open baffle use or enough sealed box volume that Qtc does not get higher than maybe 1.5.
I knew it would be pointless asking this question but worth a try.
Why not try adding the values into the calculator yourself; as the reply is:
Qtc must be greater than driver's Qts.
for VAS 0.9l QTS 1.04 which is the spec of the FRS8 8
Why not try adding the values into the calculator yourself; as the reply is:
Qtc must be greater than driver's Qts.
for VAS 0.9l QTS 1.04 which is the spec of the FRS8 8
daqvin_carter many thanks for the open baffle tip, that makes sense.
Question; can and open baffle be a tube or does it have to be just a flat panel
Please?
A tube on the backside of a speaker with an open end might be considered an open baffle. The tube can cause problem though as far as resonances and should be avoided.
Open baffles cause a loss of low frequencies when the back wave can meet the front. The loss is reduced as the baffle side and distance from back to front increases.
In the case of a small driver with a 120Hz Fs, you may need something like a 1 foot wide baffle to not avoid bass loss.
The higher driver Q works well with open baffle as the expected driver peak that is greater than .707 will be countered by the baffle loss.
Open baffles cause a loss of low frequencies when the back wave can meet the front. The loss is reduced as the baffle side and distance from back to front increases.
In the case of a small driver with a 120Hz Fs, you may need something like a 1 foot wide baffle to not avoid bass loss.
The higher driver Q works well with open baffle as the expected driver peak that is greater than .707 will be countered by the baffle loss.
Correct, as others have noted, Qtc must be = Qts [or higher], so box volume [Vb] = infinity, i.e. infinite baffle, ergo making Qtc = 1.05, box net volume [Vb] = 46.58 L
If too large, then find a higher Qtc that's small enough to see its calculated performance.
I didn't see its effective cone diameter [D] in the specs, just its area [Sd], so to convert in case you want to try a vented alignment:
[31*4/pi]^0.5 = 6.2825 cm
GM
To all please forgive the glib remark...
Quote:
You get to choose the Qtc value yourself. So specify a Qtc that's higher than the speaker's 1.04 value and you shouldn't get the error.
Now it all makes MUCH more sense, Q=Quality and i get to choose what is acceptable. played with the params and get a mega size box for such a small speaker.
Hence only deal in town for these little drivers that makes sense is simple baffle board and maybe putting shallow sides on it to decrease the overall width. Narrow tube not good as going the behave like woodwind instrument, but I have some 110mm soil pipe with baffle board front open back that might be worth a try. Wish me luck.
Again sorry for glib remark but been up all night with tinnitus, never let a cold get out of control!
Good news is just got email from post office and my Audio Labs DQ40TZF-02 arrive today, interesting week ahead. I hope there are as good as they say and not as bad, wish me luck.
imk
Quote:
You get to choose the Qtc value yourself. So specify a Qtc that's higher than the speaker's 1.04 value and you shouldn't get the error.
Now it all makes MUCH more sense, Q=Quality and i get to choose what is acceptable. played with the params and get a mega size box for such a small speaker.
Hence only deal in town for these little drivers that makes sense is simple baffle board and maybe putting shallow sides on it to decrease the overall width. Narrow tube not good as going the behave like woodwind instrument, but I have some 110mm soil pipe with baffle board front open back that might be worth a try. Wish me luck.
Again sorry for glib remark but been up all night with tinnitus, never let a cold get out of control!
Good news is just got email from post office and my Audio Labs DQ40TZF-02 arrive today, interesting week ahead. I hope there are as good as they say and not as bad, wish me luck.
imk
Good imk, you have seen how an enclosure increases the Qtc, but already Qtc=1 is a bit much. There are also some measures to lower it:
1. put some absorbent stuff near the back of the speaker
2. increase the magnetic field by putting a magnet to the back of the speaker the way it sticks stronger to it, like the shielding magnets but in the opposite direction.
3. and most effective put a serial bipolar 220uF or 330uF capacitor, this extends even the low end to 100Hz an linearizes the boost above the resonance.
Test for covid, it tends to create tinnitus
1. put some absorbent stuff near the back of the speaker
2. increase the magnetic field by putting a magnet to the back of the speaker the way it sticks stronger to it, like the shielding magnets but in the opposite direction.
3. and most effective put a serial bipolar 220uF or 330uF capacitor, this extends even the low end to 100Hz an linearizes the boost above the resonance.
Test for covid, it tends to create tinnitus