Guys,
When structural engineers like civil engineers do some concrete column calculation they just add the right amount of rebar inside the column.
There is a point that too little rebar will make the concrete column more brittle or weak and there is a point where adding more iron rebar to the column will not make it stronger , it will be only a waste of money.
Another example is when doing laundry , there is a point that if you add more soap to the washer machine your clothes do not get any more clean , is just a waste of resources. (And you make a mess overflowing the bubbles if soap out the machine )
So, when you are calculating a given design like a TH , FLH, TL or a BR box.
1st question
How to know when the the cabinet volume is at the critical point of just being the maximum efficiency you can get out of it, that making the volume bigger will only waste wood and or degrade the efficiency.
And I mean to squeeze out the last drop of SPL from a driver and amp combination.
For that let's assume you have a matched driver with the right TS parameters for the cabinet type application, let's say a BR cabinet.
2nd question
Does the sensitivity rating on the driver affect the overall SPL of the speaker system (cabinet with driver )
Let's say an 8ohm 96dB rated driver inside that BR box,and I feed it 100 watts.
If I swap it for a 90dB rated driver ,does my SPL will change ?
When structural engineers like civil engineers do some concrete column calculation they just add the right amount of rebar inside the column.
There is a point that too little rebar will make the concrete column more brittle or weak and there is a point where adding more iron rebar to the column will not make it stronger , it will be only a waste of money.
Another example is when doing laundry , there is a point that if you add more soap to the washer machine your clothes do not get any more clean , is just a waste of resources. (And you make a mess overflowing the bubbles if soap out the machine )
So, when you are calculating a given design like a TH , FLH, TL or a BR box.
1st question
How to know when the the cabinet volume is at the critical point of just being the maximum efficiency you can get out of it, that making the volume bigger will only waste wood and or degrade the efficiency.
And I mean to squeeze out the last drop of SPL from a driver and amp combination.
For that let's assume you have a matched driver with the right TS parameters for the cabinet type application, let's say a BR cabinet.
2nd question
Does the sensitivity rating on the driver affect the overall SPL of the speaker system (cabinet with driver )
Let's say an 8ohm 96dB rated driver inside that BR box,and I feed it 100 watts.
If I swap it for a 90dB rated driver ,does my SPL will change ?
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Yes it would be about 1/4 less loud besides most measurements are referred to infinite baffle in anechoic chamber which is more or less nothing we can achieve in practice. Would you hear the difference? I guess you would as well as having to turn the amp volume up for the same SPL.
With regard your first question. I do not think there is any optimum volume at all, any volume of air trapped behind a speaker would affect its given response whether it was tested or calculated. A friend mounted two speakers in a wall, the back vented into another room. Was he impressed by this fact. Not really it was still a box. If you drop a marble into a pool, the water will raise by that of the volume of the marble. Is this critical, well it depends if you are satisfied with the results and if it makes any meaningful difference in what it sounds like.
I have even see Ravens do that with small pebbles dropped in a glass of water until the surface raised to the level that he could reach the insect floating on top. Even birds find practical solutions to a problem very quickly.
I have even see Ravens do that with small pebbles dropped in a glass of water until the surface raised to the level that he could reach the insect floating on top. Even birds find practical solutions to a problem very quickly.
For practical audio use, you may want to add some qualifiers to that. There are ways to squeeze more sensitivity out of a driver/box combination over a limited band, but they tend to come at the cost of poorer transient abilities, rapid roll-off, increased distortion, etc. How much of those you add is typically related to how far you push things.
The base case for something like a ported or passive radiator box is typically what would be considered an optimized alignment where there is no peaking, excessively fast or slow roll-off, etc. Most simulators will give you that as a starting point. From there you can adjust things and see how bad they get and in what ways compared to the original.
They are implied in my previous post (which was a response to the original poster): reasonable transient response, flat frequency response, normal roll-off.
Example from UniBox's suggested vented enclosure alignment, which has those characteristics.
Same driver and power level in an exaggerated, decidedly non-audiophile bandpass box which has much higher output, but at multiple costs:
The individual designer has to decide where on the continuum of tuning options their speaker should reside. Beyond generalities, there are far too many possibilities to delineate them all concisely.
Example from UniBox's suggested vented enclosure alignment, which has those characteristics.
Same driver and power level in an exaggerated, decidedly non-audiophile bandpass box which has much higher output, but at multiple costs:
The individual designer has to decide where on the continuum of tuning options their speaker should reside. Beyond generalities, there are far too many possibilities to delineate them all concisely.
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Practical for what becomes the question.
If you look at the world record holders for vehicle SPL, you will often see highly refined tunings optimized for maximum SPL over a limited bandwidth. This is often done in ways that aren't obvious to a casual observer. In trucks/vans they sometimes add a dividing wall to separate the cabin into 2 chambers with a port between them that's about half the cabin height/width. The wall is typically only about 6 inches deep, so it's not as obvious that it's a tuned port if you aren't thinking along these lines.
If you run the numbers on some of the basics it would seem that maximizing enclosure and cabin gain is the only way to get to the extremes they can now achieve. An example: "Alan Dante from Lorton, Virginia, set a new world record on August 31st 2007 in a dB Drag competition with a 180.5dB peak using a single Digital Designs subwoofer. Dante's concrete filled Volvo contained a Digital Designs 9918Z 18″ subwoofer receiving 26,000 watts of power from four Stetsom 7KD amplifiers."
Again, a frequency response like this is not what you would choose for typical audio playback, and certainly not for an audiophile application. But if you're really going for maximum SPL only, it has its uses.
If you look at the world record holders for vehicle SPL, you will often see highly refined tunings optimized for maximum SPL over a limited bandwidth. This is often done in ways that aren't obvious to a casual observer. In trucks/vans they sometimes add a dividing wall to separate the cabin into 2 chambers with a port between them that's about half the cabin height/width. The wall is typically only about 6 inches deep, so it's not as obvious that it's a tuned port if you aren't thinking along these lines.
If you run the numbers on some of the basics it would seem that maximizing enclosure and cabin gain is the only way to get to the extremes they can now achieve. An example: "Alan Dante from Lorton, Virginia, set a new world record on August 31st 2007 in a dB Drag competition with a 180.5dB peak using a single Digital Designs subwoofer. Dante's concrete filled Volvo contained a Digital Designs 9918Z 18″ subwoofer receiving 26,000 watts of power from four Stetsom 7KD amplifiers."
Again, a frequency response like this is not what you would choose for typical audio playback, and certainly not for an audiophile application. But if you're really going for maximum SPL only, it has its uses.
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When is it ‘appropriate’ to move from a bass reflex design to a TL instead because of diminishing returns on size/output/extension ?
and then…. From ‘TL’ to tapped horn?
how do you navigate those ‘levels’ of heiarchy?
and then…. From ‘TL’ to tapped horn?
how do you navigate those ‘levels’ of heiarchy?
Once you are hooked on TL you will not look at any other design, it is just feels like effortless delivery of sound. In my opinion and many others I know. Bass reflex sounds like a wet fart.
Max SPL is mostly controlled by the driver power handling or Xmax below a certain frequency. I recommend you spend a few minutes playing with the free software WinISD. You can overlay different projects quickly and easily to see the effect of box size or any parameter.
It would be nice if you could listen to WinISD instead of looking at it. 🤔
That's when the BR reaches the size of the TL.
That's when the TL max spl isn't enough. Or you just love the extreme dynamics of a TH.
You can't. It's use specific and floating, always depending on the requirements and preferences. 'one is best' doesn't exist. For example, instead of a TL or TH you can usually place two BR subwoofers. Or, if you want the best possible fidelity, put 3-4 sealed enclosures there instead. Nothing is better in impulse response and decay than sealed.
Sealed have faster decay than reality. Take mic and amp in one room, speakers in the next so isolated. bang on something. compare input to acoustic output of speaker. Simple and realistic. Try the same with different boxes. Which performs closest to the input. Answer, driver in free air.
While that is indeed impressive, you are absolutely right about audiophile application. But let me rephrase that: Such a subwoofer isn't suitablel for audiophile, no, it's not even suitable for any HiFi or home cinema application. It's a one-note-subwoofer. It can do extremely high spl on just one frequency, everything above and below drops very fast in level. And it got a slow impulse response and an abysmal decay.
A major point in decision which subwoofer principle to choose is completely dismissed/ignored: The room. Depending on how the room looks like (dimensions, absorbing elements like furniture, carpet etc). So if the bass experience isn't what you are expecting, it's more often than not, a problem of the placement and settings. In a lot of cases it's not better to place more subs for more bass but it would sound better by magnitudes to cancel the room modes and get a more even bass throughout the room. A DBA doesn't increase the bass (much) but the sound quality will improve vastly in the most cases.
The SPL will change with frequency.
"Sensitivity" is on axis SPL 1watt/one meter is a single number, usually at a frequency above 100 Hz, higher than the typical "subwoofer" range.
For example, Eminence LAB12 sensitivity is 89.2dB, the 4012HO is 94dB, almost +5dB more sensitive.
Neither speaker reaches their rated sensitivity below 100Hz, and at 30Hz the LAB12 is +6dB more sensitive than the 4012HO.
And sensitivity is not the same as efficiency.
https://sengpielaudio.com/calculator-efficiency.htm
The 0 dB reference level for sound is 10−12 watts.
1 acoustical watt is 120 dBSPL.
The standard measurement for a cone loudspeaker is done with it mounted flush on an infinite baffle radiating into half space at a distance of r = 1 m.
The resultant factor 2π × r2 (area of a half sphere) equals −8 dB. Therefore an efficiency of 1 = 100 % for a sensitivity of 120 − 8 = 112 dB.
This calculation is correct for a loudspeaker radiating in a hemisphere, 2π. Otherwise you must add the Q factor because of directionality.
Spherical radiation Q = 1, hemisphere Q = 2, quarter sphere Q = 4, and eighth sphere Q = 8.
Note that using the above calculation, efficiency of over 100% is possible for high Q devices like narrow coverage horns which can have on axis sensitivity of well over 112dB.
If the horn driver had uniform radiation over a half sphere, it’s efficiency would be under 50%.
Sensitivity is usually defined as on axis SPL in dB at 1 watt electrical input, measured at 1 meter.
A cone loudspeaker’s sensitivity is usually measured using an infinite baffle, a half sphere radiation.
The voltage used is often 2.83 Volts RMS, which is 1 watt into an 8 Ω (nominal) speaker impedance, though that same voltage would be double the power into half the impedance, or half the power into double the impedance.
Since a speaker’s sensitivity and Q (radiation pattern) varies with frequency, a single sensitivity number is not very useful in comparing loudspeakers.
The same efficiency driver when coupled to a narrow (high Q) horn will have a higher sensitivity, since the sound power output is covering a smaller area.
The answer depends on the frequency you want maximum efficiency, the point in space you want it at, and your acceptable level of cabinet volume increase vs dB increase.
Art
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You should add that it's way more complex, depending on column dimensions, load stress, local earthquake risk, heigth/diameter ratio, accessibility of building site, required fire rating, actual concrete/iron price, design requirements ... it may be sensible to just build a steel column or a pure concrete pillar for certain situations.
Same here: depends on water hardness, laundry quantity, washing machine specifications, washing temperature, washing programme ....
There is not one value for all cases.
The same applies to speakers and there might be even more very subjective parameters.
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That's a room problem, not a speaker problem. Sealed gives you the best possible result in sound source. That of course doesn't help if you don't place them correctly or if your room is so extreme you can't fix it at all. But a DBA resolves that in the most cases, at least if your room is rectangular. Once you've installed a DBA you can hear the difference between each subwoofer working principle very well and - more important - hear the flaws and advantages between each principle so much better. You'll very likely change your view on sealed subs after that experience.
Why not plug a very low impedance speaker into the mains outlet. You don't need an amp at all. If you are required to have electronics, maybe a 10 kVA 60 Hz inverter.
Sealed gives you the best possible result in sound source. And the proof is......
You'll very likely change your view on sealed subs after that experience. I don't have subs, they sound awful. it is like a colic baby crying all night for weeks. It is like going to the cinema and watch earth quake. You are relieved when it is over. Or a car without muffler. A kid that got a tin drum for xmas. It is not entertaining, like having a head cold and snotty nose and ringing in the head.
You'll very likely change your view on sealed subs after that experience. I don't have subs, they sound awful. it is like a colic baby crying all night for weeks. It is like going to the cinema and watch earth quake. You are relieved when it is over. Or a car without muffler. A kid that got a tin drum for xmas. It is not entertaining, like having a head cold and snotty nose and ringing in the head.
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