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Discussion Starter #1 (Edited)
To me, the overall Vd is basically what determines SPL at any given frequency. If you have 1244cm Sd moving at 33mm 1 way, 66mm p-p... it doesn't matter if it is taking 100 watts or 10000 watts to get there if they are in the same enclosure. So a super loose suspension driver vs a multi-stiff-spider should have the same SPL if they have the same Sd, same excursion, and in the same enclosure.

So I just saw this vid of a 15" taking a wall socket free air, and it doen't even near it's mechanical limits. It states 19.4 amps 120 volts... all the wall has to offer...over 2000 watts. So if this thing were in an SPL or even an SQL enclosure, it must require crazy amounts of power to get any decent level of SPL. So if the same basket and cone were used, but a different motor and suspension, and it could reach the same excursion with less power, wouldn't that driver be capeable of the same SPL...and require less power doing it?

I guess I just dont understand how high power high BL stiff suspension drivers actually get louder than a SQ driver with a loose suspension and smaller power requirement driver could with the same excursion.


 

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While I think I know what you mean by "SPL or even an SQL enclosure" and "BL," your use of acronymns is difficult to follow, particularly on a forum that does not have a strong car audio context. I suggest that you be more precise in your language and don't assume that every one is familiar with these terms as you are using them.

It sounds like you are asking if a higher sensitivity driver gets louder with the same power. If that is what you are asking, the answer is mostly yes, but you can't really divorce that issue from the box design that is most appropriate for the driver.
 

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To me, the overall Vd is basically what determines SPL at any given frequency.
Actually, Vd only determines the maximum SPL at a given frequency, for a given box. Actual SPL is determined by frequency, power input, and the cabinet design. That is, unless by Vd you are speaking of volume being displaced, rather than what it should be, which is maximum linear swept volume (Sd * Xmax).

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I guess I just dont understand how high power high BL stiff suspension drivers actually get louder than a SQ driver with a loose suspension and smaller power requirement driver could with the same excursion.
If both drivers have the same cone area (Sd), both are in boxes which produce identical response curves, and both have the same excursion, then the SPL from each will be the same. However, it's rare that so many things are identical. And especially at higher frequencies with very large drivers, what are small absolute changes in excursion (say 5mm) may be quite large changes in SPL.
 

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Discussion Starter #4
If both drivers have the same cone area (Sd), both are in boxes which produce identical response curves, and both have the same excursion, then the SPL from each will be the same. However, it's rare that so many things are identical. And especially at higher frequencies with very large drivers, what are small absolute changes in excursion (say 5mm) may be quite large changes in SPL.
That's what I was looking for... Thanks Aaron.
 

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Jordan,

You are asking: Why a big SPL woofer will have a long throw, multiple spiders, very heavy vc and cone assembly, all of which lowers the sensitivity, so why not just have a much higher sensitivity to begin with and use less power...Correct?

If you have 2 drivers with the exact same SD and one has an 88db 2.83v sensitivity while the other has a 96db rating at the same input power, they will both need to move exactly the same amount of air (cone excursion) to generate 105db spl, but the power levels required for each to do this will be dramatically different. The less sensitive one will require nearly 8x the power.

So why aren't people using pro audio woofers with 98db ratings for SPL comps? Care to guess?
 

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Basically yes. Even though the pro audio drivers are much more sensitive they still have to physically move the same amount of air, and many of them are just not made to sweep a huge volume of air. Even though SPL burps are in the 40-60hz range usually it is still all about displacement and you need a long throw to do this, which many of the pro drivers just don't have. Also to create that much xmax up in that part of the bass range requires a ton of power input even for something as efficient as a good pro woofer. Also the ports in the SPL boxes will be optomized to have a huge peak in the FR netting a lot of free SPL there partially making up for the comparatively low sensitivity of the driver.
 

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Discussion Starter #8
I think back to Scotty Johnson with his Brahma's... SQ subs with low Fs, high Xmax..

there's SPL drivers... DD subs, solox, so so many... then there's real good SQ subs... mael-x TCSounds...

Can't the mael-x and TCSounds be "just as loud"

Why all these bullet proof subs that need beat into submission when these easy going subs need a little tickle....
 

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Discussion Starter #9
Also to create that much xmax up in that part of the bass range requires a ton of power input even for something as efficient as a good pro woofer.
now that part tripps me up, because that's just it... these saturated high BL drivers have lower Xmax ratings generally.... so really, my sub that has 30mm or more should be louder than their sub that might have 20mm at most Xmax...

I know that statement goes to forget actual sound quality... they may be pushing their driver to 30mm or more overall excursion, seriousely passing it's Xmax, so it may not sound the best doing it....

AND if it has such a high BL at rest, though it is passing it's 70% BL downpoint, it may still very well have more motor force than said SQ driver at it's 33mm excursion point...
 

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Discussion Starter #10
http://www.cardomain.com/ride/553176/4


6 years ago I had a pair of Audiobahn AW1500Q's in a tiny sealed box. We plugged them into the wall. It took 4 tries to blow them cuz it kept popping the fuses in the house. Both subs went full excursion stretching the surround.

Later we plugged in an S15L7 freeair. It didn't bottom out, but it went pretty close to full excursion... it didn't last anywhere near 4 minutes.

Later still, another S15L7 in 3.5 cubes @27Hz.... blew the breaker 3 times, several bursts... not 4 minutes. More excursion I'm guessing than what that other sub looked like though with more Sd.


http://realmofexcursion.com/videos/Kicker/l715.13.wmv
 

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Discussion Starter #11
While I think I know what you mean by "SPL or even an SQL enclosure" and "BL," your use of acronymns is difficult to follow, particularly on a forum that does not have a strong car audio context. I suggest that you be more precise in your language and don't assume that every one is familiar with these terms as you are using them.

It sounds like you are asking if a higher sensitivity driver gets louder with the same power. If that is what you are asking, the answer is mostly yes, but you can't really divorce that issue from the box design that is most appropriate for the driver.
I guess I realize how anoying I can be always bringing car audio into the HT areas...totally not intended, I guess I find myself conflicted... I do both, right now I am trying to get my car audio back up and running. My HT is going to have to wait. The things I talk about and want to learn about i feel apply to both... they may lean more one way or the other, but there are home theater drivers that are more power hungry and so on...

SPL, Sound Pressure Level, is the same for all audio arenas, so SPL enclosure would imply a high SPL box, vs an SQ box... Sound Quality... more atention spent on good sound, wider flatter responce.

While I can see these acronyms being more familiar in car audio, BL is a Thiele Small parameter that Pro audio and Home Theater probably use more than the car guys.

Though I don't assume everyone has any idea what these words mean, I assume most of the well informed individuals on here know what they mean, and those are the ones I would expect answers to my questions from. Those who don't know what BL means, SPL enclosure, or SQ oriented...I welcome to learn right along with me, but hope they wouldn't fake an answer if they don't know what that means.

I am torn at the moment, as my current project is car audio... which will not always be the case, however I find the car audio forums to be... I'll just say I like getting my answers here, and not there. I think thats clear. It can be difficult as we are speaking of different things, I think the more advanced general knowledge here is still more helpful in car audio applications than a lot... not all.. of what needs to be sifted through from other forums.
 

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The point is that if you use acronyms and shorthand, those who might be interested but not tuned in to your perspective may not get what you are saying. More people are likely to read with interest and learn something if they can understand what you are talking about. This forum is not dedicated only to well informed designers, but to anyone who wants to learn something or share information and ideas, therefore we try to communicate plainly using good grammar and terminology that is clear, assuming that we have a diverse audience.
 

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You CAN achieve the same bandwidth and output from a higher sensitivity driver.....it's just that it requires a much much much larger enclosure if you want to keep that sensitivity and dig low at the same time.

The reason pro sound drivers don't have crazy excursion is because their output is mostly thermally limited....if they needed more excursion, then they would be designed with more excursion. It's just that pro sound can often get away with only digging down to 40-50Hz. Though lately it seems like systems are dropping down into the 30's quite frequently...and those drivers have a lot more excursion, but still not quite what you'll see from drivers intended to dig down into the teens.
 

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Discussion Starter #14
The point is that if you use acronyms and shorthand, those who might be interested but not tuned in to your perspective may not get what you are saying. More people are likely to read with interest and learn something if they can understand what you are talking about. This forum is not dedicated only to well informed designers, but to anyone who wants to learn something or share information and ideas, therefore we try to communicate plainly using good grammar and terminology that is clear, assuming that we have a diverse audience.


:D i barelly gurgiated but i got my diplomat

point taken, and i liked your responce...it did answer my question
 

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Discussion Starter #15
You CAN achieve the same bandwidth and output from a higher sensitivity driver.....it's just that it requires a much much much larger enclosure if you want to keep that sensitivity and dig low at the same time.

The reason pro sound drivers don't have crazy excursion is because their output is mostly thermally limited....if they needed more excursion, then they would be designed with more excursion. It's just that pro sound can often get away with only digging down to 40-50Hz. Though lately it seems like systems are dropping down into the 30's quite frequently...and those drivers have a lot more excursion, but still not quite what you'll see from drivers intended to dig down into the teens.
Where does all of this fit into the scheme of things strictly HT... I guess I feel more at home in here because most HT drivers seem to have loose suspension, low inductance, high linear excursion, and yet, you generally use large enclosures as well... and that is exactly what I love, thats what I am after, but in both applications.

It seems to me PRO is the most efficient, least excursion, largest enclosures...but still high power from large drivers(22" and 18" sub and 10" and 12" for mid)

HT is in between... not as efficient, not as large enclosures, a lot more linear excursion...the most Xmax??


And then car audio... I hate car audio. All bling, super stiff, super heavy, over built, and the same for enclosure...tiny and high tuned. Requires gobbs of power and generally not very good sounding.

I get that this all follows gain... pro audio is either totally open: outside, or in very large rooms where corner loading and wall loading and gains are hard to come by, home theater more gain and loading, and car audio has seriouse loading and gain...the reason I can't wait to have a huge low tuned box in-car.... seriouse sub 30Hz!
 

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The point is...
I feel like I smoked something very powerful and walked in to the middle of a conversation.

I recognize the words. The sentances make sense, but I have no clue what you guys are talking about. :dumbcrazy:

But hey, I'm happy. Give me another puff...
 

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that little wall socket demo is proof that sensitivity matters. it actually takes quite a bit of power to bottom a driver at 60Hz in free air, even if its pretty sensitive. 60 cycles a second is a lot of back and fourth and if you dont have the acceleration, you'll never reach very high displacement.

these SPL drivers take a lot of power because they are usually burped at resonance in a 4th order box which forces the drivers excursion down and the ports excursion up. Think about pushing someone on a swing... you will naturally do it at the resonance because its easier. As resonance, the active driver can take absurd amount of power before reaching xmax. I can model this out and i have seen cases where 20,000 watts will not even reach 30mm. But you can rest assure something will probably break pretty fast!

The other thing that can happen at least with very high BL drivers is that these super high BL drivers have a natural back EMF that works to restrict cone excursion. This is your every day Qes and if its really low, the woofer is not going to easly bottom out without a very high voltage source. Bob Carver calls this the "stall" effect. This is also why low Q drivers are not adviced to be loaded into a sealed box. You'll have to put +10, even +20dB EQ filters at 30Hz to get em flat. They really need to take advantage of a port.
 

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Discussion Starter #18
The other thing that can happen at least with very high BL drivers is that these super high BL drivers have a natural back EMF that works to restrict cone excursion. This is your every day Qes and if its really low, the woofer is not going to easly bottom out without a very high voltage source. Bob Carver calls this the "stall" effect. This is also why low Q drivers are not adviced to be loaded into a sealed box. You'll have to put +10, even +20dB EQ filters at 30Hz to get em flat. They really need to take advantage of a port.
Is this along the lines of EBP and alignment suitability?
 

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Good post Kyle. Much clearer than my feeble attempt to explain why SPL burp subs are the way that they are.:doh:

I've got a question about back EMF. In a driver with a really powerful motor does this force ever become strong enough to cause the amplifier difficulty or possibly even damage it? There are some things that I have noticed from messing with my Ultra and XXX's that are interesting. Also I remember a few threads about killer drivers that would smoke amplifiers. One of those was the Eclipse SW8200 I think. From reading through the Klippel papers there is mention of a DC component that can be generated by the driver under certain high excursion conditions. Can you explain a bit about that? I wonder if this is related?
 

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Discussion Starter #20
What have you noticed?

I'm guessing nothing like what I called "cone suck down" or "driver suck down" when talking to Dan Wiggins about my Avalanche moving normaly free air until a certain volume, all of a sudden the cone would have the same excursion but it would mostly be beind rest position, not equal to both sides of rest. This also happened when plugging my S15L7 into the wall free air.... most of the excursion was behind rest, little was forward of the rest position.

http://realmofexcursion.com/videos/AscendantAudio/avalanche15.6.wmv

edit: in that vid, it loooks like a bad camera refresh rate, but whats really happening is I am slightly lowering the volume so the excursion is centered, then turning it up a tad so the cone sucks down, then I turn it down again, up again, so you see smaller constant ecursion, but when you see the large shift it's actually me adjusting the volume a tad
 
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