I am in the design stage of a mid-bass system
to cover from 50 Hz -500hz. I realize 500 hz is above the so called mid-bass zone, but I need to cover that high.
I can choose between a 15" driver, or I also have some 12's. For this sake of discussion, let's take the difference in SD, or effectice cone area, out of the equation for now. I noticed the 12" version has a moving mass of 62.1 grams with a BL of 16.94 thus giving an FA of 272 (considered excellent)
as oppossed to the 15":
It's moving mass is 127 grams with an even higher BL of 23.44, none the less, the FA only comes out to 184.
I read somewhere else on these forums where the force factor (FA) is the BL product divided by the moving mass(?)
The 15 " has a Fs of 28 and a Qts of .24 while the 12's fs = 44 and a Qts of .32
Which unit, do you think, would be better for Mid-Bass (sound quality wise) ?
to cover from 50 Hz -500hz. I realize 500 hz is above the so called mid-bass zone, but I need to cover that high.
I can choose between a 15" driver, or I also have some 12's. For this sake of discussion, let's take the difference in SD, or effectice cone area, out of the equation for now. I noticed the 12" version has a moving mass of 62.1 grams with a BL of 16.94 thus giving an FA of 272 (considered excellent)
as oppossed to the 15":
It's moving mass is 127 grams with an even higher BL of 23.44, none the less, the FA only comes out to 184.
I read somewhere else on these forums where the force factor (FA) is the BL product divided by the moving mass(?)
The 15 " has a Fs of 28 and a Qts of .24 while the 12's fs = 44 and a Qts of .32
Which unit, do you think, would be better for Mid-Bass (sound quality wise) ?
Neither. Remember Newton's law of motion, whereby force equals mass times acceleration. Now picture your woofer accelerating forward as a result of the force applied upon it by the voice coil. The woofer has no foreknowledge as to what kind of signal it is reproducing. It can be a large 90 Hz sine, for example, or it can be a small 900 Hz sine. Midway up a slope, a woofer cannot know which is which. Maximum acceleration a woofer can sustain is reflected in its frequency response. As long as it is asked to reproduce signals within its flat passband, it can accelerate well enough. The quality of reproduction will then depend on other parameters such as distortion, eddy currents, baffle rigidity, internal reflections, etc etc. In practice a woofer's maximum acceleration reflects the maximum allowed rate of change in current flow, which in turn will be limited by the high pass filter feeding the woofer.
What is "Sound Quality"?
just kidding. 😛
Please list the multitude of variables needed to determine if a driver is right for the application?
Sincerely,
revb.
just kidding. 😛
Please list the multitude of variables needed to determine if a driver is right for the application?
Sincerely,
revb.
You might want to read up on VC inductance (Le). I think that's part of what you are looking for.
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If I have read this right, given the option of hi-passing or not hi-passing the mid bass, the better choice would be no- high pass (?) Then all the other variables you listed come in to play.----Also, I have a 3rd set of woofers to choose from for this application, and low and behold, they have the lowest
Le of the bunch.Thanks for helping me see this.
I would think that a dedicated mid/bass driver would require a limited bandpass signal from the amplifier to allow it to perform near it's best.
That would require the wideband audio signal arriving at the amplifier input to be filtered to attenuate the LF signals and similarly that the HF signals should also be filtered.
That would require the wideband audio signal arriving at the amplifier input to be filtered to attenuate the LF signals and similarly that the HF signals should also be filtered.
I'm sorry, my bad, I wrote high pass when I should have written low pass. The answer is no, but some may disagree.
Is 50Hz a mid bass frequency?
There are plenty of PA bass drivers that will reproduce 50Hz but not many that will go lower without x-max limitations.
What is the maximum spl that is required?
Regards Xoc1
As for your original question, you'll be better off if you post the drivers you are considering and ask for advice directly. There are many people here who will give you a thoughtful opinion. Posting riddles is not really going to help you much, especially so since you seem to be unfamiliar with the basics.
The Force Factor (in N/A, force in Newton obtained for 1 Ampere) is equal to the Bl product (in T.m, induction in the gap B in Tesla multiplied by the "effective" length of the coil wire submitted to the magnetic field).
The Bl product multiplied by the current value (i) in the coil gives the force applied to the moving mass Mms. This force is then equal to :
Bl* i
The acceleration in m/s² of the moving mass is equal to the force divived by the moving mass :
(Bl) * i / Mms
The so-called Acceleration Factor, AF, is the Bl product divided by the moving mass Mms. Many people think of it as a quality criterion for the drivers, it is not a good conception.
The moving mass has no way to "know" the origin of the force applied to it.
It will be accelerated with the same manner, be it from a driving force issued of a given Bl and a given current or from a driving force issued of half this Bl and twice this current.
Of course, the efficiency of the first driver is better but as the movements are identical, it is not per se an indicator of better sound reproduction.
All this can be demonstrated using a dual-voice-coil driver.
The Bl product multiplied by the current value (i) in the coil gives the force applied to the moving mass Mms. This force is then equal to :
Bl* i
The acceleration in m/s² of the moving mass is equal to the force divived by the moving mass :
(Bl) * i / Mms
The so-called Acceleration Factor, AF, is the Bl product divided by the moving mass Mms. Many people think of it as a quality criterion for the drivers, it is not a good conception.
The moving mass has no way to "know" the origin of the force applied to it.
It will be accelerated with the same manner, be it from a driving force issued of a given Bl and a given current or from a driving force issued of half this Bl and twice this current.
Of course, the efficiency of the first driver is better but as the movements are identical, it is not per se an indicator of better sound reproduction.
All this can be demonstrated using a dual-voice-coil driver.
Specifics
In a nutshell: I have a 4-way system. All but the mid-bass "section"
perform to my satisfaction. Subs are mono infinite baffle and operate fine below
50 Hz, but could raised to as high as 80Hz I suppose. Trying a 60Hz x-over frq
next is very possible. Mid range is a large horn, but covering much below 500Hz
would be a real push. Above 2500 is the Stage Accompany SA8535.
For mid-bass, I have three sets of possible drivers:
Dayton Audio PRO 15" version (PA-380); the same Dayton Audio PRO, but the
12 inch version, or, the Eminence Definimax HO4012's which are also 12"
At first I was leaning towards the 15's just based on the larger available cone area, plus that really nice BL value of 23+ but since learning more through reading here on this forum, there's much more to it than just the BL or force factor. The Eminence have the lowest Le of the bunch.
Also, I intend to use 2 drivers per channel. All opinions and insights welcome.
In a nutshell: I have a 4-way system. All but the mid-bass "section"
perform to my satisfaction. Subs are mono infinite baffle and operate fine below
50 Hz, but could raised to as high as 80Hz I suppose. Trying a 60Hz x-over frq
next is very possible. Mid range is a large horn, but covering much below 500Hz
would be a real push. Above 2500 is the Stage Accompany SA8535.
For mid-bass, I have three sets of possible drivers:
Dayton Audio PRO 15" version (PA-380); the same Dayton Audio PRO, but the
12 inch version, or, the Eminence Definimax HO4012's which are also 12"
At first I was leaning towards the 15's just based on the larger available cone area, plus that really nice BL value of 23+ but since learning more through reading here on this forum, there's much more to it than just the BL or force factor. The Eminence have the lowest Le of the bunch.
Also, I intend to use 2 drivers per channel. All opinions and insights welcome.
The posted Le for most drivers is mesured at 1kHz and changes with frequency. generally it goes down as frequency goes down untill you near resonance, common stuff. The thing I look at is how fast it goes up from it's minimum. The Impedance generally mirrors the inductance, so you can look at the Impedance chart and get a good idea about how "fast" the coil will change direction at any given frequency.
For these three drivers with no other considerations. (we have not considered enclosure, application, or anything else) The driver with the most gradual impedance rollup is the Dayton 12". Charts attached. Although the Dayton 15" is a close second and if more SPL is needed it would work almost as well from 50-500Hz
For these three drivers with no other considerations. (we have not considered enclosure, application, or anything else) The driver with the most gradual impedance rollup is the Dayton 12". Charts attached. Although the Dayton 15" is a close second and if more SPL is needed it would work almost as well from 50-500Hz
Attachments
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You don't specify what your SPL target is for any of your drivers.
I doubt that you need 15" nor dual 15" for a lower Mid/upper bass driver.
Look up the data that shows Litres of displacement for desired SPL at various frequencies.
You should be able to identify a medium excursion, medium diameter driver than can theoretically achieve your desired SPL. From there you consult the driver database and determine which individual driver (or combination) can meet your SPL requirement.
Simply guessing at a driver size and displacement capability seems a waste of time to me.
I doubt that you need 15" nor dual 15" for a lower Mid/upper bass driver.
Look up the data that shows Litres of displacement for desired SPL at various frequencies.
You should be able to identify a medium excursion, medium diameter driver than can theoretically achieve your desired SPL. From there you consult the driver database and determine which individual driver (or combination) can meet your SPL requirement.
Simply guessing at a driver size and displacement capability seems a waste of time to me.
Educated guess
I'm leaning towards using the Dayton 12 inchers for this application. Although it my seem like I am a novice- due to the simplistic and mysterious nature of my posting, I actually very experienced in speaker building. It's just that during my formative years, all the sims and calcs that you guys do second nature like, were simply not available years ago. I strictly remember the requirement for one acoustical watt at 50Hz requires .53 of the capabilities of one 15 inch driver. Two twelves equals a bit more than one fifteen, so, that-plus my intended loading technique should work fine. Having noted my hands-on-only experience, I also note I do not have any formal engineering back ground, which was why I was asking for help. How far back do I go? Well, to give you an idea: I walked into Lafayette Radio electronics asking for 2.5 mH air core inductor, and they looked at me like I was from Mars. Five years after that episode
Thiele Small Theory was introduced.
For the most part I find this forum and it's contributors very interesting and helpful, and I am greatful for that.
I'm leaning towards using the Dayton 12 inchers for this application. Although it my seem like I am a novice- due to the simplistic and mysterious nature of my posting, I actually very experienced in speaker building. It's just that during my formative years, all the sims and calcs that you guys do second nature like, were simply not available years ago. I strictly remember the requirement for one acoustical watt at 50Hz requires .53 of the capabilities of one 15 inch driver. Two twelves equals a bit more than one fifteen, so, that-plus my intended loading technique should work fine. Having noted my hands-on-only experience, I also note I do not have any formal engineering back ground, which was why I was asking for help. How far back do I go? Well, to give you an idea: I walked into Lafayette Radio electronics asking for 2.5 mH air core inductor, and they looked at me like I was from Mars. Five years after that episode
Thiele Small Theory was introduced.
For the most part I find this forum and it's contributors very interesting and helpful, and I am greatful for that.
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We still need to acertain how loud your system is to give you a meaningful answer.
There is no point in specifying a PA style monster cab if you dont need the SPL.
More info on your current speaker enclosures, drivers, and the amplifiers you are using would help to estimate what sort of speaker would be in balance with the rest of your system.😉
There is no point in specifying a PA style monster cab if you dont need the SPL.
More info on your current speaker enclosures, drivers, and the amplifiers you are using would help to estimate what sort of speaker would be in balance with the rest of your system.😉
Certainly !!
In order to match the rest of the system, the mid bass section should have at least a maximum SPL requirement of 110 db @ 1 meter, that's per channel.
The devoted mid-bass amplifier is at maximum 400 watts. I have a strong feeling I could run out of x-max long before i hit the max power rating.
I admit I'll need help figuring the max excursion for this driver at 50 Hz vs a 60 Hz x-over frq, as it's listed as a 5mm x-max. Thanks again to all.
In order to match the rest of the system, the mid bass section should have at least a maximum SPL requirement of 110 db @ 1 meter, that's per channel.
The devoted mid-bass amplifier is at maximum 400 watts. I have a strong feeling I could run out of x-max long before i hit the max power rating.
I admit I'll need help figuring the max excursion for this driver at 50 Hz vs a 60 Hz x-over frq, as it's listed as a 5mm x-max. Thanks again to all.
what is the displacement of a 12" driver with an Xmax of 5mm.
http://www.diyaudio.com/forums/multi-way/5668-volume-displacement-spl-chart.html#post55867
shows the inch units (imperial) for displacement for 50Hz and 110dB to be about 15 to 20 cub inches.
the next post shows the centimetre units (SI).
I would expect a single 12" driver to get pretty close to your SPL target.
I told you not to guess.
http://www.diyaudio.com/forums/multi-way/5668-volume-displacement-spl-chart.html#post55867
shows the inch units (imperial) for displacement for 50Hz and 110dB to be about 15 to 20 cub inches.
the next post shows the centimetre units (SI).
I would expect a single 12" driver to get pretty close to your SPL target.
I told you not to guess.
Hi Scott,
You should download WinISD and spend some time tinkering.
There isn't a law or rule that states when you reach Xmax based on frequency and Xmax ratings alone. The driver characteristics, and box loading all come into play. Entering the driver characteristics into winISD, then simulating the performance in a box will give you a graph (amongst many others) showing maximum power handling at various frequencies as limited by either Pe or Xmax. It is an incredibly useful tool and simming a handful of different drivers side by side will often reveal which driver is most well suited to your application. When doing a handful of comparisons, you'll find that higher quality, more expensive drivers, tend to provide better use of available Pe and Xmax. A lot of people here have been doing this so long, that they can spot a set of characteristics that will work better for an application without the need of the sim at all.
Eric
You should download WinISD and spend some time tinkering.
There isn't a law or rule that states when you reach Xmax based on frequency and Xmax ratings alone. The driver characteristics, and box loading all come into play. Entering the driver characteristics into winISD, then simulating the performance in a box will give you a graph (amongst many others) showing maximum power handling at various frequencies as limited by either Pe or Xmax. It is an incredibly useful tool and simming a handful of different drivers side by side will often reveal which driver is most well suited to your application. When doing a handful of comparisons, you'll find that higher quality, more expensive drivers, tend to provide better use of available Pe and Xmax. A lot of people here have been doing this so long, that they can spot a set of characteristics that will work better for an application without the need of the sim at all.
Eric
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