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Discussion Starter #1
If a subwoofers FS is when the drivers impedance is max, doesnt this mean the amp will be pushing much less power at this "FS"?
 

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Discussion Starter #3
Makes sense.

I asked this because of something odd I noticed when I installed my three Boston G5 10s in a sealed box a few days ago. They have a higher FS (about 32hz) than any other sub Ive ran in the last few years yet they absolutely destroy the super low bass much better than any other low FS driver Ive used. So much so that songs like the famous "Bass I love you" actually flex my side window about an inch on that one super low note in the beginning of the song. I think its around 17hz. Other songs with 25hz content play much louder too. This goes against what Ive read about low FS divers being able to play lower....

My guess was since the FS of the driver was higher, that the amp was able to push more power to the driver while playing below said FS, thus playing louder.
 

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depends on how big that sealed box is too. a sealed box will play very low with enough power and enough xmax to back it up. you have to consider cabin gain too. what vehicle is this in?
 

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Fs is moot when the driver is in a box-it's Fb you need to look at.

As Minbari says there are other factors to consider:

Box design-port may go louder and allow tuning, but has a steeper roll off so a box tuned to 35Hz can have less output than a sealed box at 20Hz.

Cabin gain makes a huge difference, my sub plays entirely below the Fb of the enclosure-76Hz, F3 of the enclosure is 76.8Hz outside of my car, inside the car it's near flat to 20Hz
 

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Discussion Starter #6
depends on how big that sealed box is too. a sealed box will play very low with enough power and enough xmax to back it up. you have to consider cabin gain too. what vehicle is this in?
Its in my 2004 Impala SS, Ive had probably 15 or so high-end sub stages in this car(all sealed) and this one definitely stands out in the super low range

Fs is moot when the driver is in a box-it's Fb you need to look at.

As Minbari says there are other factors to consider:

Box design-port may go louder and allow tuning, but has a steeper roll off so a box tuned to 35Hz can have less output than a sealed box at 20Hz.

Cabin gain makes a huge difference, my sub plays entirely below the Fb of the enclosure-76Hz, F3 of the enclosure is 76.8Hz outside of my car, inside the car it's near flat to 20Hz
I have to check what the F3 would be, the box is sealed built to Boston specs.
 

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Its in my 2004 Impala SS, Ive had probably 15 or so high-end sub stages in this car(all sealed) and this one definitely stands out in the super low range
What was the cone area/excursion of the others? Similar to these?

I have to check what the F3 would be, the box is sealed built to Boston specs.
As I said in my previous post the F3 will change when you put the sub into the car-the car acts as a mechanical EQ. Have a look at the graphs below, one shows my sub's modeled output in open space, the other the modeled response with cabin gain factored in-you can see why I was (fairly) confident a "Linkwitz Transform enclosure" would work in my car-check the box volume 0.126cf, manufacturer recommends much, much more! My sub is crossed at 63Hz atm, approx 10Hz below F3 of the box before it goes in-car!
 

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Discussion Starter #8
What was the cone area/excursion of the others? Similar to these?



As I said in my previous post the F3 will change when you put the sub into the car-the car acts as a mechanical EQ. Have a look at the graphs below, one shows my sub's modeled output in open space, the other the modeled response with cabin gain factored in-you can see why I was (fairly) confident a "Linkwitz Transform enclosure" would work in my car-check the box volume 0.126cf, manufacturer recommends much, much more! My sub is crossed at 63Hz atm, approx 10Hz below F3 of the box before it goes in-car!
Ive used another box of three 10's, a few single 15's, and MANY dual 12's. ALL sealed, all in the same position. I never used any extremely small or large boxes.
 

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A subwoofers fs and resulting box alignments all have usefulness in predicting the ouput of one enclosure versus another. There is a more important factor at work that cannot be considered with small signal t/s parameter modeling.

Large signal performance can not be modeled using simple enclosure programs and even LEAP bases it's much better models on some parameters input by the user. So if you are not familiar with compliance versus excursion and bl versus excursion for a driver you can only compare them at small signal ( less than a watt).

Subwoofers can work below Fs without damage unlike a tweeter or midrange, and the drivers Fs can give you some insight into the drivers suspension stiffness or lack there of which is termed compliance. But if the suspension stiffens dramatically as you move the diaphragm from the rest position the low frequency performance will suffer in relation to how much the compliance is reduced.

Having worked with and engineered many drivers over the years I can tell a whole lot about a speakers performance just by grabbing the cone and exercising the suspension. I have picked up some rather well regarded drivers and noticed things like the cone moves outward with a consistent stiffness until the surround or spider hits the brakes and then push the cone downward and feel it get very stiff very quickly. A driver that does not have linear compliance will no perform well in the low frequency ranges.

So the reason for what you are hearing can be attributed to a more linear compliance model at higher excursion.

And this a good reason for testing a driver for large signal performance.

Eric
 

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Discussion Starter #14
A subwoofers fs and resulting box alignments all have usefulness in predicting the ouput of one enclosure versus another. There is a more important factor a work that cannot be considered with small signal t/s parameter modeling.

Large signal performance can not be modeled using simple enclosure programs and even LEAP bases it's much better models on some parameters input by the user. So if you are not familiar with compliance versus excursion and bl versus excursion for a driver you can only compare them at small signal ( less than a watt).

Subwoofers can work below Fs without damage unlike a tweeter or midrange, and the drivers Fs can give you some insight into the drivers suspension stiffness or lack there of which is termed compliance. But if the suspension stiffens dramatically as you move the diaphragm from the rest position the low frequency performance will suffer in relation to how much the compliance is reduced.

Having worked with and engineered many drivers over the years I can tell a whole lot about a speakers performance just by grabbing the cone and excercising the suspension. I have picked up some rather well regarded drivers and noticed things like the cone moves outward with a consistent stiffness until the surround or spider hits the brakes and then push the cone downward and feel it get very stiff very quickly. A driver that does not have linear compliance will no perform well in the low frequency ranges.

So the reason what you are hearing can be attributed to a more linear compliance model at higher excursion.

And this a good reason for testing a driver for large signal performance.

Eric
I think I get what youre saying about compliance. For instance the CM UL12s I used to have were SUPER stiff pushing in, but easier to move out, and they sucked on the super low stuff. The G5s seem stiff at first, but they actually move in and out quite evenly once you get it started. Same with the ID Max's, they played the supers lows nicely too.
 

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Eric-what would you say to the fact he was running ID gear and not getting these results?-I've heard great things about the ID subs listed in his sig.
More cone area is the king for LF extension, so if this system has more Sd its is going to do better as long as you have compliance linearity to go with it.

Eric
 

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He says he's previously run:
Two ID Max 12's-so about 10sq" less
Three Arc 10's-so "same" cone area
Two Aura 12's- so about 10sq" less
Two IDQv3 12's- so about 10sq" less

So the Arcs have less compliance linearity and the rest could be around the same
 

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Discussion Starter #17
Just did a check on SD of three Boston 10's and two IDmax's.

Three G5 10 = 150in
Two ID Max 12 = 170in

(rounded to the nearest inch or so)
 
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