Wrong! Sorry... The way a speaker is loaded, effects efficiency in a BIG way. Loading options can easily produce as much as a 50dB swing in efficiency for lower frequency response.
Think it through:
The size of the box is not going to change the strength of the motor.
The size of the box is not going to change the weight of the cone.
The size of the box, if it's too small, might increase the stiffness of the suspension, but do you think more resistance to motion is going to increase the efficiency?
Saying the speaker is more efficient because the bass is extended is like saying a 100 watt amp with wider bandwidth has more gain.
In fact, Thiele's equation for efficiency puts Fs in the numerator, so drivers with less bass will be louder. (It's right next to Vas, for anyone that wasn't thinking clearly in answer to my question above.)
The size of the box is not going to change the strength of the motor.
The size of the box is not going to change the weight of the cone.
The size of the box, if it's too small, might increase the stiffness of the suspension, but do you think more resistance to motion is going to increase the efficiency?
Saying the speaker is more efficient because the bass is extended is like saying a 100 watt amp with wider bandwidth has more gain.
In fact, Thiele's equation for efficiency puts Fs in the numerator, so drivers with less bass will be louder. (It's right next to Vas, for anyone that wasn't thinking clearly in answer to my question above.)
50dB variations huh ? 🙄
Assuming we're sticking to closed or bass reflex boxes not bass horns, the mid band efficiency is as I said dictated by the driver itself.
Sure, the box will affect the bottom end response at frequencies where the response is rolling off, by changing the cut-off frequency and bass alignment, (droopy response, peaking response etc) but efficiency is never defined at frequencies where the response is already rolling off, but at frequencies above the rolloff.
Five minutes with any speaker box simulator will show that the basic efficiency of a driver/box is set by the driver.
If you want to get a higher efficiency with the same cutoff frequency and rolloff curve then you do need a bigger box, but you also need a different driver. A bigger box with the same driver won't get you a higher efficiency, just a potentially lower cutoff frequency.
and you forgot to say:
if the bass box is only used for the bass range, then extra output in the bass range (due to the bigger box) for the same input signal equals higher efficiency.
if the bass box is only used for the bass range, then extra output in the bass range (due to the bigger box) for the same input signal equals higher efficiency.
But only if an appropriate driver is chosen. It's the parameters of the driver that dictate both the efficiency, and whether that bigger box contributes towards increased efficiency, or a lower cutoff frequency.
You can very easily get the same efficiency from a larger box as a smaller box, but with a lower cutoff frequency. In fact that is usually the result of using the same driver in the larger box - you get a lower cutoff frequency, but the efficiency is identical.
As I said in my previous post, to get an efficiency gain from a larger box (greater efficiency with the same cutoff frequency) requires a different driver to be selected - a driver with a higher efficiency, and the right other parameters if you're trying to get back to the same alignment.
Am I going round in circles, or is it you?
More output in the required frequency range from the same input is higher efficiency.
If a bigger box with the same driver gives more output in the required frequency range then that can only be due to higher efficiency.
I have not changed the driver to achieve the higher output.
More output in the required frequency range from the same input is higher efficiency.
If a bigger box with the same driver gives more output in the required frequency range then that can only be due to higher efficiency.
I have not changed the driver to achieve the higher output.
What you're confusing is that reference efficiency isn't defined at frequencies where the response has already rolled off, it's by definition at frequencies above the roll-off.
Your "increased efficiency" at lower frequencies is because what was once below the cutoff frequency may now be above the new cutoff frequency. Of course output falls below the cutoff frequency...
If we shift the cutoff frequency from 40Hz to 30Hz with a bigger box is the reference efficiency greater ? Nope, above 50Hz or so it takes the same amount of power to produce the same amount of output. There has been no broadband increase in efficiency. To do that requires a different driver.
Technically there is an increase in efficiency below 40Hz but that is because the cutoff frequency has changed so you're at a different point on the rolloff curve.
It's kinda pointless talking about the "efficiency" of a speaker below its cutoff frequency, unless you plan to have most of the bass range below the cutoff frequency...on the other hand if you expect to reproduce bass well then you want the majority of the bass range above the cutoff frequency, which means the reference efficiency is what matters.
Reference efficiency (that squirrly n in the datasheet) has nothing to do with our bigger box smaller box efficiency discussion.
It's the output from the box that matters.
It's the output from the box that matters.
It has everything to do with the discussion. At and above the cutoff frequency the driver dictates the efficiency, below cutoff the efficiency falls, causing the output to roll off.
Using a bigger box with the same driver can (up to a point) allow you to lower the cutoff frequency so that the drivers own innate efficiency can be maintained to a lower frequency. That's all.
In reality we're only quibbling about the definition of the word "efficiency", not what is actually going on. The problem is that the word "efficiency" is very clearly defined in speaker and Thiele/Small nomenclature, and the efficiency of the speaker at one spot frequency below cutoff is not how it is defined, so to speak of a larger box increasing the efficiency of the same driver is simply wrong. It is changing the cutoff frequency and roll-off shape of the response.
I see. So it's your definition of "efficiency", not the accepted definition that engineers use, that applies to this "discussion"?
I'll grant the definition of "efficiency" implies consideration of bandwidth, but efficiency has always been calculated at, and sensitivity has been measured at, the midband. Don't think that will change, even if it would be convenient for your argument.
Then, simply refer to it as "total output" and we'll stop "going round in circles".
i have work so i will read this more thouroughty when i get back
the larger box increases the efficency in part of the speaker range, thats was all i ment. obviously a driver has its raited avarage efficency, but we all know that changes with frequencys
also it obviouly its mecanical limet, yes the 90l box is more efficent at 30hz but it will also take less juice than the 70l one, both are probubky capable of the same output at said frequency. correct me if i am wrong.
here is a graph to illistrate the two
what im still really wanting to know is if my port has enougth space to breath.. (16cm)
but this is all very interesting all the same
the larger box increases the efficency in part of the speaker range, thats was all i ment. obviously a driver has its raited avarage efficency, but we all know that changes with frequencys
also it obviouly its mecanical limet, yes the 90l box is more efficent at 30hz but it will also take less juice than the 70l one, both are probubky capable of the same output at said frequency. correct me if i am wrong.
here is a graph to illistrate the two
what im still really wanting to know is if my port has enougth space to breath.. (16cm)
but this is all very interesting all the same
Waveform,
now add in the crossover effect.
If the crossover is set to >=200Hz, then the overall efficiency is dominated by the upper bass/midrange efficiency.
If, conversely, the crossover is set to <=60Hz, then the overall efficiency is dominated by the lower bass efficiency.
Just ignore the reference efficiency that is quoted in the T/S parameters. You don't need that value. You don't use that value. The box design does not use that value. It is a reference value that plays virtually no part in determining the box design.
now add in the crossover effect.
If the crossover is set to >=200Hz, then the overall efficiency is dominated by the upper bass/midrange efficiency.
If, conversely, the crossover is set to <=60Hz, then the overall efficiency is dominated by the lower bass efficiency.
Just ignore the reference efficiency that is quoted in the T/S parameters. You don't need that value. You don't use that value. The box design does not use that value. It is a reference value that plays virtually no part in determining the box design.
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How much larger should we listen to this nonsense about a box being incapable of increasing efficiency and maximum SPL before someone posts the effects of horn loading a driver?
Oh well, it's entertaining I suppose...
Enjoy, carry on 🙂
Oh well, it's entertaining I suppose...
Enjoy, carry on 🙂
Very interesting descussion about box size effecting efficency...😴. but still by question has gone unanswered 🙁
my port will fire from the rear of the box, there will be 16cm between the intake of the port and the front baffle, as per my quick pic 2 pages ago...
i think, that it is fine,
i really just want to clarafiy..
does my port have enougth room to breath/ and thus produce the simmed responce?
thanks
my port will fire from the rear of the box, there will be 16cm between the intake of the port and the front baffle, as per my quick pic 2 pages ago...
i think, that it is fine,
i really just want to clarafiy..does my port have enougth room to breath/ and thus produce the simmed responce?
thanks
There was a rule that the port ends needed to be at least 1.5 diameters away from other surfaces and from the driver cone.
I don't know how valid that advice is, since it requires comparison of different builds for the same speaker design.
I don't know how valid that advice is, since it requires comparison of different builds for the same speaker design.
Thanks!
The port is 10cm x10cm internal. It is 15cm x 15cm external (25mm MDF)
There is 16cm between the port and the inside of the speakers front wall.
You stated 1.5, Ths pre-posed final design is 1.6.
So its fine🙂
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