Lol, you must have a commercial subwoofer 😀 15" woofer is the norm in DIY land.
Sorry, no. Show me any multiples of 12" drivers that can dig as deep and play as loud (let alone as cleanly) as a single $275 Avalanche 18 in a large and low tuned enclosure using only 600 watts. In other wordsm -3db at ~13.7hz with 116db output +/-1.5db from 80-14.5hz anechoic. Just can't be done.
That's fine if you want big output above 20hz, what if you want big output to 10hz?
The Avalanche 18 will easily sweep more air and dig deeper than a 15" Tempest for less money - and it also uses XBL^2.
Well, you seemed to be taking issue with someone who got it right:
He :"no! they are different..."work done" not equal to "torque"
You: "Read again -same units
they are both a force applied over a distance."
He :"no! they are different..."work done" not equal to "torque"
You: "Read again -same units
they are both a force applied over a distance."
So everyone would agree then that a 18" driver can be just as quick as an 8" driver working in it's passband ?
--Sincerely,
--Sincerely,
I guess they battle on uneven terms - sensitivity is mostly different fore the two of them - an 8" will need more power at the same SPL, it will move longer and have to move faster in the same time domain, it will eventually get into trouble and loose precision, while the 18" will do it with ease
Since mass affects efficiency it will also affect SPL, correct ? If SPL is affected then would acceleration not be affected too if SPL is accerelation ?
--Sincerely,
--Sincerely,
Yes, it is a basic tenet that F = ma, or a = F/m. Decrease mass, increase acceleration if force is kept the same. However, it's a little more iffy for bass output since mass also affects Fs (and other things, I think), which affects bass in ways I'm not sure about.
Then again, surely the engineers would overcome that efficiency problem using bigger magnets to overcome the weight issue of the driver ?
--Sincerely,
--Sincerely,
If you spend time in FEMM or a similar program, you would see that increasing magnet size doesn't increase B as much as you think (depends on geometry, of course). Widening the magnet does get you more than thickening it, assuming a conventional ferrite design.
Doesn't the gap size affect B, more so than simple magnet size ? I mean, the cross sectional area of the gap has more of an influence on total B than just a bigger magnet ?
And wouldn't the different pole piece types also affect B as well ? Just asking.
--Sincerely,
And wouldn't the different pole piece types also affect B as well ? Just asking.
--Sincerely,
Yes! and the size of voice coil, and thereby the amount of cobberwire inside the gab - but theres a limit to everything
So are there examples of 18" drivers that are "slow" because of high amounts of inductance or is this a very rare thing ? I now understand quite well that driver size alone has nothing to do with speed.
But according to Dan, driver inductance is a factor that influences speed. Perhaps someone could explain what he is getting at with the spiel on inductance.
I would think that room acoustics play a far bigger role in subjective bass "speed" due to ringing or decay of low frequencies than simply the driver.
I would think so. I mean, if bass notes are decaying 1/4 of a second after the bass player stops playing, I would be concerned.
--Sincerely,
But according to Dan, driver inductance is a factor that influences speed. Perhaps someone could explain what he is getting at with the spiel on inductance.
I would think that room acoustics play a far bigger role in subjective bass "speed" due to ringing or decay of low frequencies than simply the driver.
I would think so. I mean, if bass notes are decaying 1/4 of a second after the bass player stops playing, I would be concerned.
--Sincerely,
I always find bass notes to be rather slow and relaxed, and when bass gets quick I often find that its due to phase problems which I find very stressing😉
Bigger is always better...almost.
Other than cabinet wall flexing...bigger is always better at low frequencies. Bigger cabinets...bigger woofers....bigger is better. The "transfer function" (frequency response) of the complete bass system and it's maximum acoustic output response together define the performance of the system. In every case, the lower the bass cutoff and the higher the maximum output, the better. Big boxes and big woofers can do this easier/better and possibly even cheaper.
The only reason big woofers are almost impossible to find is that either 1) their higher output capabilities are not thought to be needed in the specific application or 2) their larger enclosures are less appealing and saleable. It has nothing at all to do with "big heavy cones" being slow (they are not) just as an electrostatic driver's low moving mass makes them faster (they are not). These are popular myths
The truth is that "heavy" only means potentially less efficient so that a larger force (motor) must be used to drive and control it and "light" means potentially more efficient so a small force is needed to drive and control it. But of course, the larger the radiating area the higher the efficiency, too.
Using a high power rifle to accelerate a piece of Mylar film versus the heavy bullet pretty much says it all. If you have the motor to drive something heavy....you'd better not be in front of it when it's fired up
Likewise, if electrostats had anything close to the force/area that moving coil drivers have, they'd rule the world. But they don't and won't.....so moving coils rule the world
(though the crossoverless opportunities of an electrostatic also gives them an advantage) 
Other than cabinet wall flexing...bigger is always better at low frequencies. Bigger cabinets...bigger woofers....bigger is better. The "transfer function" (frequency response) of the complete bass system and it's maximum acoustic output response together define the performance of the system. In every case, the lower the bass cutoff and the higher the maximum output, the better. Big boxes and big woofers can do this easier/better and possibly even cheaper.
The only reason big woofers are almost impossible to find is that either 1) their higher output capabilities are not thought to be needed in the specific application or 2) their larger enclosures are less appealing and saleable. It has nothing at all to do with "big heavy cones" being slow (they are not) just as an electrostatic driver's low moving mass makes them faster (they are not). These are popular myths
The truth is that "heavy" only means potentially less efficient so that a larger force (motor) must be used to drive and control it and "light" means potentially more efficient so a small force is needed to drive and control it. But of course, the larger the radiating area the higher the efficiency, too.
Using a high power rifle to accelerate a piece of Mylar film versus the heavy bullet pretty much says it all. If you have the motor to drive something heavy....you'd better not be in front of it when it's fired up
Likewise, if electrostats had anything close to the force/area that moving coil drivers have, they'd rule the world. But they don't and won't.....so moving coils rule the world (though the crossoverless opportunities of an electrostatic also gives them an advantage) Inductance
Regarding inductance.....it's not the inductance but the L/R break frequency (when the inductive impedance magnitude equals the voice coil's resistance). Above that frequency the power output of the transducer rolls off first order (6dB/oct) though through manipulation, the axial response can be maintain (and often is with middlers and tweeters).
High L/R is common in automotive woofers particularly because their enclosures are designed to be small (so a long heavy coiled high inductance woofer is used) and the woofer's resistance is low too (so as to obtain more power from the given and often limited, automotive amplifier voltage).
This can be true in home subwoofers too but again, their "transfer function" (frequency response) predicts the performance of the sound you will hear, and inductance is just one internal system parameter that can be manipulated to obtain the desired transfer function.
If the transducer has the response you need/desire, how the designer got to that result really makes no difference so focusing on one parameter is seldom useful and can be misleading.
Regarding inductance.....it's not the inductance but the L/R break frequency (when the inductive impedance magnitude equals the voice coil's resistance). Above that frequency the power output of the transducer rolls off first order (6dB/oct) though through manipulation, the axial response can be maintain (and often is with middlers and tweeters).
High L/R is common in automotive woofers particularly because their enclosures are designed to be small (so a long heavy coiled high inductance woofer is used) and the woofer's resistance is low too (so as to obtain more power from the given and often limited, automotive amplifier voltage).
This can be true in home subwoofers too but again, their "transfer function" (frequency response) predicts the performance of the sound you will hear, and inductance is just one internal system parameter that can be manipulated to obtain the desired transfer function.
If the transducer has the response you need/desire, how the designer got to that result really makes no difference so focusing on one parameter is seldom useful and can be misleading.
But BL in and of itself is not a pivotal factor in terms of "speed". Right ? It only defines efficiency. A low BL does not necessarily mean a slow bass.
And a high BL isn't required for big drivers either. An 18" driver with a BL less than a 15" doesn't necessarily mean that it won't be as "fast". It just means that more power will be required to move the cone at any given frequency (all things being equal).
--Sincerely,
And a high BL isn't required for big drivers either. An 18" driver with a BL less than a 15" doesn't necessarily mean that it won't be as "fast". It just means that more power will be required to move the cone at any given frequency (all things being equal).
--Sincerely,
Hi,
I have an aversion to car quality anything and my biased opinion means I do not follow the car trends, so my info may be inaccurate.
I thought that car speakers were optimised to a high q to allow them to work without the assistance of a cabinet. This car speaker Q is likely to be in the range 0.6 to 0.8.
When the driver Q is this high
A low Q driver needs to small box relative to Vas. I would never call a low Q driver an automotive woofer.
I have an aversion to car quality anything and my biased opinion means I do not follow the car trends, so my info may be inaccurate.
I thought that car speakers were optimised to a high q to allow them to work without the assistance of a cabinet. This car speaker Q is likely to be in the range 0.6 to 0.8.
When the driver Q is this high
does not apply, in fact the opposite the box volume is enormous in comparison to the Vas.
A low Q driver needs to small box relative to Vas. I would never call a low Q driver an automotive woofer.
BL and small boxes
BL is a measure of the coupling between the input current and the resultant force to drive and control the cone and coil. If the woofer is for infinite baffle (some in cars are) then BL isn't important, Qts is the key.
With a Qts of around 0.7 the response will be maximally flat and -3dB at the free air resonance. So, look at Qts and Fs for free air and very large enclosure woofers. With small enclosures (and many car woofers are used that way) the Qts must be low because it rises significantly in a small box.
If the box is vented, Qts of 0.4 gives flattest response if the box volume and tuning is correct. In sealed boxes, the lower the Qts and heavier the moving mass, the better the bass response shape (like Roy Allison discovered in his Acoustic Research "acoustic suspension" systems...way back when). But those are very inefficient and need tons of power to perform. But if you want a tiny box and impressive crunch...they can do it (with 1kW or more power to drive them).
Focusing on BL can be deceptive since excess BL gives you LESS bass output and inadequate BL gives lifted output near resonance (but with a dipole, you'll be hard pressed to find a woofer with a BL that gives a Qts higher than 0.7). So, focus on Qts unless you're doing sealed or vented boxes and then, there's a ton of info out there about how to design those systems.
BL is a measure of the coupling between the input current and the resultant force to drive and control the cone and coil. If the woofer is for infinite baffle (some in cars are) then BL isn't important, Qts is the key.
With a Qts of around 0.7 the response will be maximally flat and -3dB at the free air resonance. So, look at Qts and Fs for free air and very large enclosure woofers. With small enclosures (and many car woofers are used that way) the Qts must be low because it rises significantly in a small box.
If the box is vented, Qts of 0.4 gives flattest response if the box volume and tuning is correct. In sealed boxes, the lower the Qts and heavier the moving mass, the better the bass response shape (like Roy Allison discovered in his Acoustic Research "acoustic suspension" systems...way back when). But those are very inefficient and need tons of power to perform. But if you want a tiny box and impressive crunch...they can do it (with 1kW or more power to drive them).
Focusing on BL can be deceptive since excess BL gives you LESS bass output and inadequate BL gives lifted output near resonance (but with a dipole, you'll be hard pressed to find a woofer with a BL that gives a Qts higher than 0.7). So, focus on Qts unless you're doing sealed or vented boxes and then, there's a ton of info out there about how to design those systems.
misterears,
If the box is vented, Qts of 0.4 gives flattest response if the box volume and tuning is correct.
Wouldn't that be an overdamped alignment or am I confusing this for sealed ?
If the woofer is for infinite baffle (some in cars are) then BL isn't important, Qts is the key.
Wouldn't suspension linearity be key too, especially in an IB where the drivers are operating in free air and hence no air spring ?
--Sincerely,
If the box is vented, Qts of 0.4 gives flattest response if the box volume and tuning is correct.
Wouldn't that be an overdamped alignment or am I confusing this for sealed ?
If the woofer is for infinite baffle (some in cars are) then BL isn't important, Qts is the key.
Wouldn't suspension linearity be key too, especially in an IB where the drivers are operating in free air and hence no air spring ?
--Sincerely,
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