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#14,341
I am having the same issue with Mmd... The TS parameters are provided in Mms, so without being a math genius it is really hard to convert to Mmd. I can't help but wonder how many people are putting in the wrong driver parameters with such unusual and non standard units being required to be entered.
 
#14,343
@David McBean

Is this unit of measurement right? Either the driver is only moving 2.5mm or the unit is meant to be in cms not mm.

Screenshot from 2024-03-09 11-32-29.png
 
#14,344
3/4 of driver's Sd.
Silent Screamer said:
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.
Click to expand...

The port will be a rectangular vent.

Why waste money on a round port when you have plenty of wood and the enclosure itself can make up 3 of the 4 sides to the vent.

Our 1320 math has been jacked up!

You stated 1320 / 2 = 640, when it's 660.

1st, I used 1320 x 0.33 and got 435.60.
1320 / 3 = 440...all 1/4 mile numbers!

2nd, I used 670 when I should have used 660.

You just proved what I have been saying how BR's and TL's are the same 2nd order enclosures.
 
#14,346
Silent Screamer said:
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.
Click to expand...
When you double click on Sd or Sd field (I'm on my phone), input the T/S parameters and HR auto calculates all the other speaker specifications.
 
#14,348
Silent Screamer said:
I am having the same issue with Mmd... The TS parameters are provided in Mms, so without being a math genius it is really hard to convert to Mmd. I can't help but wonder how many people are putting in the wrong driver parameters with such unusual and non standard units being required to be entered.
Click to expand...

Like I said before, HR will auto calculate those numbers from the T/S parameter window.

Of course, you can manually put in those numbers from actual speaker measurements.
 
#14,351
Silent Screamer said:
How are people converting typically provided Rms in kg/s to the required newton sec/m?
Click to expand...

The units are equivalent, 1 kg / s = 1 N * s / m.

force = mass * acceleration

By definition 1 Newton is the force that gives a mass of 1 kilogram an acceleration of 1 metre per second per second.

1 N [force] = 1 kg [mass] * 1 m / (s ^ 2) [acceleration]

1 N = 1 kg * m / (s ^ 2)

Rearranging:

1 kg / s = 1 N * s / m
 
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#14,353
BP1Fanatic said:
You stated 1320 / 2 = 640, when it's 660.
Click to expand...

lol whoops, that's embarrassing to get such a simple math problem wrong.

BP1Fanatic said:
Why waste money on a round port when you have plenty of wood and the enclosure itself can make up 3 of the 4 sides to the vent.
Click to expand...

Not so much a waste of money as I was planning to get a mate to 3d print a flared port then get some plumbing tube from the hardware, but super impractical.
My Sd is 1194, so at 1/3 that is ~400. That still works out to be very sizable in terms of port diameter, so I immediately started thinking, that a round port is not going to be practical for these larger drivers.
As much as I wanted to go round, the rectangle port build into the box walls seems like the only sensible option, even if it is not optimal. Maybe I just go a bit bigger to avoid port chuff. Work on say 500.
 
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#14,356
BP1Fanatic said:
Like I said before, HR will auto calculate those numbers from the T/S parameter window.

Of course, you can manually put in those numbers from actual speaker measurements.
Click to expand...

I double clicked on the Mmd to see if it had an option to convert it. I tried deleting the value to see if it would auto create it but neither worked. In BBP6 on the TS page it has a calc button next to all of the different parameters so you can enter what you know of the manufacturers specs, or press the button to calculate the ones you don't know. That way you are relying less on code generated numbers. I keep forgetting that the TS parameters are only accessible via the Sd label. Wish there was a TS button.

The problem is Mms and Rms in the TS parameters on the drivers I looked at aren't in the same units as those required.
 
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