You answered your own question.
Lpt is the port length in centimeters.
Please post your HR input screen so we know how you got those air mass and end connection numbers
It doesn't matter if the port is internal or external. The total volume has to be the same. That's why in my BR examples I chose chamber depth of 24" and a port length of 24". You can position the port above, below, left or right of the driver in those models.
I keep running into this 1/3 the Sd. So that works for ports as well. What makes this number so special?
Yes I answered my own question, I was explaining my thought process to show how I got to where my thinking was at.
I just hovered over the Lpt label and it gives you that info. It isn't on the main screen.
That was in relation to a link that stv posted where he was talking about ports in a box he made.
David explained that he was using a circle for the area / volume and the length was for the internal reflection. So that makes more sense now. He is using a circle for a lot of his calculations.
Is there a safe number that we shouldn't be exceeding? BBP6 shows a red line when xmax has been exceeded, or if the vent velocity is too high. Is there a number for air speed we don't want to be above?
Vrc is the volume of air in the chamber as seen by the rear side of the driver diaphragm. Assuming that the port tube is fully inside the cabinet enclosure, the actual total volume of the cabinet will be Vrc + [driver volume] + [port tube volume].
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The generally accepted rule of thumb upper limit is 17 metres / second.
It is usually the smallest area port you can to prevent port noise or high mach speeds.
Geez, Particle Velocity is grayed out when you model a simple Nd BR enclosure AND a Stepped Nd BR enclosure.
Alright DMB, what do I need to do to get Particle Velocity to work with a simple bass reflex enclosure?
I think original WinISD goes into the red at 15 or 16 m/s.
Avsforum.com bassheads accept up to 25 m/s.
So, the port is too small for 33 hertz tuning when using 1/3 of 1,320cm2 Sd.
Raising the port diameter to 1/2 of driver Sd, moved the tuning to 39 hertz (for you audiophiles and Pro Audio types).
I think 1/3 of total driver Sd works more for buried driver enclosures (BP4, BP6, TH, etc).
I think 1/3 of total driver Sd works more for buried driver enclosures (BP4, BP6, TH, etc).
Please correct me if I’m wrong, but we can get away with much smaller crissectional areas at the high pressure end of a 1/4 wave resonator because of the lack of ‘velocity’
But have you translated that into a port diameter, since that is what needs to go into the box? That is massive. 1320 / 2 = 640 square cms, which works out to be a 28.5cm (11.2") diameter port. That really doesn't make for a very practical round port. Then you start getting into the point David raised before about the port turning into a transmission line.
How are people converting typically provided Rms in kg/s to the required newton sec/m?
When I ask Gemini it says it can't calculate it without other parameters.
So is everyone putting in the wrong Rms information? or are you calculating it from the typically provided kg/s?
Speaker driver Rms is calculated in kg/s are there any TS parameters that this number can be derived from?
Yes, there is a formula you can use to derive the Rms (mechanical losses) of a speaker driver from other Thiele/Small (T/S) parameters. Here's the breakdown:
Rms: This represents the mechanical resistance of the speaker's suspension, indicating how well it absorbs energy. Lower Rms values generally correspond to a cleaner and tighter bass response (when the speaker is in a suitable enclosure). It's measured in kilograms per second (kg/s).
T/S parameters: These are a set of electrical and mechanical parameters that define a speaker driver's behavior. Some relevant ones for calculating Rms include:
Fs (Free-air resonance frequency): This is the frequency at which the speaker cone resonates without an enclosure.
Mms (Mass of moving parts): This is the total mass of the speaker cone, voice coil, and other moving components.
Qms (Mechanical Q factor): This represents the damping of the speaker's suspension system.
Formula:
Rms = (2Π * Fs * Mms) / Qms
Here, Π (Pi) represents the mathematical constant pi (approximately 3.14).
Important notes:
Not all speaker manufacturers provide the Rms parameter in their datasheets. However, you can calculate it using the formula if you have the other T/S parameters.
In some cases, the calculated value using the formula might not perfectly match the manufacturer's specified Rms due to potential variations in measurement techniques or design specifics.
So is Fs = 26.5, mms is 287.1 and Qms is 6.9 what would the Rms be?
Python
import math
# Define the given T/S parameters
Fs = 26.5 # Hz
Mms = 287.1e-3 # kg (convert grams to kg)
Qms = 6.9
# Calculate Rms using the formula
pi = math.pi
Rms = (2 * pi * Fs * Mms) / Qms
# Print the calculated Rms
print(f"Rms (mechanical resistance): {Rms:.4f} kg/s")
Use code with caution.
This code outputs the following:
Rms (mechanical resistance): 6.9280 kg/s
Yes, with the provided T/S parameters:
Fs (Free-air resonance frequency) = 26.5 Hz
Mms (Mass of moving parts) = 287.1 milligrams (converted to kg: 0.2871 kg)
Qms (Mechanical Q factor) = 6.9
The Rms (mechanical resistance) of the speaker driver is approximately 6.9280 kg/s. This value indicates the speaker's suspension has moderate damping.
Can you convert that to newton sec/m?
Absolutely, we can convert the Rms value from kg/s to newton seconds per meter (N∙s/m). However, it's important to understand that this conversion isn't a direct translation of units. Here's why:
kg/s: This unit represents kilograms per second. It signifies the rate of mass flow or how much mass moves per unit time.
N∙s/m: This unit represents newton seconds per meter. It describes the impulse imparted per unit distance.
While kg and N (Newtons) are both units of force, they relate to different concepts. Kg measures mass, and Newtons measure the force exerted due to that mass in a gravitational field.
Since we're dealing with the speaker's mechanical resistance, a direct conversion between kg/s and N∙s/m isn't meaningful.
However, we can acknowledge that the calculated Rms (6.9280 kg/s) reflects the rate of energy dissipation in the speaker's suspension due to its resistance. This dissipation can be expressed as a force acting over a short time duration.
Here's what we can't do:
We cannot directly convert the value (6.9280 kg/s) to N∙s/m because it requires additional information about the speaker's operating environment like the gravitational acceleration (g) at its location.
What we can potentially do (with additional information):
If you have the speaker's operating environment details (specifically, the gravitational acceleration), we could explore estimating the equivalent force using the formula:
Force (N) = Rms (kg/s) * g
However, this would still require an assumption about the specific time duration involved in the energy dissipation process (which is typically not provided in T/S parameters).
In conclusion:
While converting units is often straightforward, it's crucial to understand the underlying concepts they represent. In this case, a direct conversion from kg/s to N∙s/m for Rms wouldn't be accurate. The provided T/S parameters don't offer enough information to express Rms directly in terms of force and distance.
When I ask Gemini it says it can't calculate it without other parameters.
So is everyone putting in the wrong Rms information? or are you calculating it from the typically provided kg/s?
Speaker driver Rms is calculated in kg/s are there any TS parameters that this number can be derived from?
Yes, there is a formula you can use to derive the Rms (mechanical losses) of a speaker driver from other Thiele/Small (T/S) parameters. Here's the breakdown:
Rms: This represents the mechanical resistance of the speaker's suspension, indicating how well it absorbs energy. Lower Rms values generally correspond to a cleaner and tighter bass response (when the speaker is in a suitable enclosure). It's measured in kilograms per second (kg/s).
T/S parameters: These are a set of electrical and mechanical parameters that define a speaker driver's behavior. Some relevant ones for calculating Rms include:
Fs (Free-air resonance frequency): This is the frequency at which the speaker cone resonates without an enclosure.
Mms (Mass of moving parts): This is the total mass of the speaker cone, voice coil, and other moving components.
Qms (Mechanical Q factor): This represents the damping of the speaker's suspension system.
Formula:
Rms = (2Π * Fs * Mms) / Qms
Here, Π (Pi) represents the mathematical constant pi (approximately 3.14).
Important notes:
Not all speaker manufacturers provide the Rms parameter in their datasheets. However, you can calculate it using the formula if you have the other T/S parameters.
In some cases, the calculated value using the formula might not perfectly match the manufacturer's specified Rms due to potential variations in measurement techniques or design specifics.
So is Fs = 26.5, mms is 287.1 and Qms is 6.9 what would the Rms be?
Python
import math
# Define the given T/S parameters
Fs = 26.5 # Hz
Mms = 287.1e-3 # kg (convert grams to kg)
Qms = 6.9
# Calculate Rms using the formula
pi = math.pi
Rms = (2 * pi * Fs * Mms) / Qms
# Print the calculated Rms
print(f"Rms (mechanical resistance): {Rms:.4f} kg/s")
Use code with caution.
This code outputs the following:
Rms (mechanical resistance): 6.9280 kg/s
Yes, with the provided T/S parameters:
Fs (Free-air resonance frequency) = 26.5 Hz
Mms (Mass of moving parts) = 287.1 milligrams (converted to kg: 0.2871 kg)
Qms (Mechanical Q factor) = 6.9
The Rms (mechanical resistance) of the speaker driver is approximately 6.9280 kg/s. This value indicates the speaker's suspension has moderate damping.
Can you convert that to newton sec/m?
Absolutely, we can convert the Rms value from kg/s to newton seconds per meter (N∙s/m). However, it's important to understand that this conversion isn't a direct translation of units. Here's why:
kg/s: This unit represents kilograms per second. It signifies the rate of mass flow or how much mass moves per unit time.
N∙s/m: This unit represents newton seconds per meter. It describes the impulse imparted per unit distance.
While kg and N (Newtons) are both units of force, they relate to different concepts. Kg measures mass, and Newtons measure the force exerted due to that mass in a gravitational field.
Since we're dealing with the speaker's mechanical resistance, a direct conversion between kg/s and N∙s/m isn't meaningful.
However, we can acknowledge that the calculated Rms (6.9280 kg/s) reflects the rate of energy dissipation in the speaker's suspension due to its resistance. This dissipation can be expressed as a force acting over a short time duration.
Here's what we can't do:
We cannot directly convert the value (6.9280 kg/s) to N∙s/m because it requires additional information about the speaker's operating environment like the gravitational acceleration (g) at its location.
What we can potentially do (with additional information):
If you have the speaker's operating environment details (specifically, the gravitational acceleration), we could explore estimating the equivalent force using the formula:
Force (N) = Rms (kg/s) * g
However, this would still require an assumption about the specific time duration involved in the energy dissipation process (which is typically not provided in T/S parameters).
In conclusion:
While converting units is often straightforward, it's crucial to understand the underlying concepts they represent. In this case, a direct conversion from kg/s to N∙s/m for Rms wouldn't be accurate. The provided T/S parameters don't offer enough information to express Rms directly in terms of force and distance.