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The easiest thing for you to do, is take a subwoofer, make a super small enclosure and one that is considerably larger. Install said sub in each. Press the cone down. Then tell me which one returns to its rest point faster. This right here will show you the smaller the box, the more the air spring works. Which controls the diaphragm by pushing or pulling it.
If you take the same sub out of the box and push on it, it will return to the rest point immediately. Same thing in a box that's .1cu or one that's 100cu, it doesn't matter. The way you describe it just means that your enclosure is leaking.
 

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If you take the same sub out of the box and push on it, it will return to the rest point immediately. Same thing in a box that's .1cu or one that's 100cu, it doesn't matter. The way you describe it just means that your enclosure is leaking.

Ever had a sub have a puncture somewhere in the surround that takes you too long to find?






on a positive note to lighten the mood:
 

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This is exactly right and is expressed in the relationship between the various Q values in thiele and small parameters.

Qes is the amount of overshoot that the motor allows.
Qms is the amount of overshoot that the suspension allows.
Qts is the product of those two over the sum (same as resistors in parallel) and the fact that the result (Qts) is much closer to the Qes value than the Qms value indicates that the MOTOR provides more cone control.

So...when you put your woofer in a sealed box, Qts becomes Qtc. Qtc is the amount of overshoot that the system allows and it's higher than Qts and higher than Qms too. By the nuumbers, that means that the box increases overshoot.
Andy,

Is there ever a point that a low qts (say .4 from a low qtc driver in ib) that it is detrimental to the sq of the woofer? What would suffer from such a low qts?
 

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Andy,

Is there ever a point that a low qts (say .4 from a low qtc driver in ib) that it is detrimental to the sq of the woofer? What would suffer from such a low qts?
No, just less bass. Think of the box as pushing the response up a bit at resonance and making the rolloff a little steeper. Usually a low Q woofer is designed so that it'll provide acceptable performance in a smaller box. A Q of .707 is the best compromise between low frequency extension and flat response above the rolloff. Lower Q begins rolloff at a higher frequency but at the very lowest frequencies it makes a little more bass.
 

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Discussion Starter #45
Thanks again, Andy, for clearing this up. You have a way of making this stuff so easy to understand.

I've been looking into this more lately because I have a set of 10" midbasses in the doors with a Qts of .6 and a 3.5" midrange in the kicks with a Qts of .2, both running IB (well almost IB on the midbass). No complaints with the sound, just trying to understand it better.
 

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Discussion Starter #46
Control by the air spring resulting in better transient response is not a myth.
Looks like it is a myth afterall.

Air spring or air suspension, is control over the cone, there really is no debating this. The smaller the box, the stronger the spring. Its just logic. You know, I am at a loss for the losing efficiency part from JL's site, when they say make the enclosure too big. But JL has never put out wrong info for sales. Maybe whoever was typing that up made a mistake. But that is the only mistake on that page. I have yet to pull up one thing that says differently.

But here are some more links, all stating cone control in sealed enclosures by the air spring.

From kicker
Sealed Enclosure Pros and Cons | KICKER


Here is a link to a article that was copied to this the forum from the University of Michigans Engineering department. Only thing relavent to this discussion is the part about sealed enclosure or the acoustic suspension
Main Speaker Design Theory compared to Transmission Line - The Classic Speaker Pages Discussion Forums

Here is some info on Ebay among all places
eBay Guides - Ported vs Sealed Box Enclosure

also talks alittle about air spring
Speakers, Part 4: Enclosures | Frugal Home A/V



I can find tons more info, and it all says the same thing. Attack and decay are considered faster in sealed enclosures, thats because of the air spring bringing the cone back to its resting position faster.




The easiest thing for you to do, is take a subwoofer, make a super small enclosure and one that is considerably larger. Install said sub in each. Press the cone down. Then tell me which one returns to its rest point faster. This right here will show you the smaller the box, the more the air spring works. Which controls the diaphragm by pushing or pulling it.


I am talking about air spring and its effects on the diaphragm, not the frequency response of a sub in too small of an enclosure.

This myth section is retarded, its mainly just people spreading myths about myths or truths, and thats the truth :laugh:

Why do you think subs geared towards sealed enclosures have a softer suspension? Its because the air spring.
This goes to show how many internet "experts" are wrong.
 

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The problem and what makes it so difficult for so many to understand is that the MOTOR controls the cone movement and the suspension OPPOSES the motor. A spring is NOT a damper. A spring is the OPPOSITE of a damper. A super ball is the opposite of an avocado.

Let's use another example. Does a spring mattress or a tempurpedic mattress offer more control?
 

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Andy...Can you touch of the effects of air spring to a driver? Is air spring just something that is represented in the QTS calculation or does it show up elsewhere?
 

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Discussion Starter #50
The problem and what makes it so difficult for so many to understand is that the MOTOR controls the cone movement and the suspension OPPOSES the motor. A spring is NOT a damper. A spring is the OPPOSITE of a damper. A super ball is the opposite of an avocado.

Let's use another example. Does a spring mattress or a tempurpedic mattress offer more control?
It's so simple when you put it that way. Before this thread, I had a theory and it kind of made sense to me but now it seems so simple. A spring and damper are actually opposites. A spring stores energy and will reverberate unless you have a shock to oppose the spring, to absorb the "overshoot" of the spring. So is this overshoot why we sometimes see a peak when modeling subs in too small of a box in WinISD? Would that be considered distortion since it's not a part of the original signal?

Going a little off topic, it seems like the MS8 has an easier time "dealing" with lower Qtc subs. Would you say this is correct some of the time?

Sorry Andy but I have so many questions to ask when you're online.:D
 

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Discussion Starter #51
The problem and what makes it so difficult for so many to understand is that the MOTOR controls the cone movement and the suspension OPPOSES the motor. A spring is NOT a damper. A spring is the OPPOSITE of a damper. A super ball is the opposite of an avocado.

Let's use another example. Does a spring mattress or a tempurpedic mattress offer more control?
It's so simple when you put it that way. Before this thread, I had a theory and it kind of made sense to me but now it seems so simple. A spring and damper are actually opposites. A spring stores energy and will reverberate unless you have a shock to oppose the spring, to absorb the "overshoot" of the spring. So is this overshoot why we sometimes see a peak when modeling subs in too small of a box in WinISD? Would that be considered distortion since it's not a part of the original signal?

Going a little off topic, it seems like the MS8 has an easier time "dealing" with lower Qtc subs. Would you say this is correct some of the time?

Sorry Andy but I have so many questions to ask when you're online.:D
I swear I saw the bolded after I had posted my reply lol. I wasn't trying to copy Andy.
 

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It's so simple when you put it that way. Before this thread, I had a theory and it kind of made sense to me but now it seems so simple. A spring and damper are actually opposites. A spring stores energy and will reverberate unless you have a shock to oppose the spring, to absorb the "overshoot" of the spring. So is this overshoot why we sometimes see a peak when modeling subs in too small of a box in WinISD? Would that be considered distortion since it's not a part of the original signal?

Going a little off topic, it seems like the MS8 has an easier time "dealing" with lower Qtc subs. Would you say this is correct some of the time?

Sorry Andy but I have so many questions to ask when you're online.:D
Yes, the peak in the response of a high Q system is overshoot--also referred to as "ringing". This is what an underdamped system does and that's what a high Qtc system is.

MS-8 has A much easier time if it doesn't have to sort out a bunch of enormous peaks in the midbass. If you just have to use a high Q system with an MS-8, then enable the LPF on the sub amp to smooth out the bass a little before MS-8 tries to fix it.
 

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The further you are away from Fs with the crossover on the lowend of a passband, the less you have to worry about the Q of the driver in the enclosure. At 2x Fs it really doesn't matter. The closer to resonance, the more it matters...especially IB where Qts= system Q.

All of this deals with the anechoic shape of the lowend response.

Thanks again, Andy, for clearing this up. You have a way of making this stuff so easy to understand.

I've been looking into this more lately because I have a set of 10" midbasses in the doors with a Qts of .6 and a 3.5" midrange in the kicks with a Qts of .2, both running IB (well almost IB on the midbass). No complaints with the sound, just trying to understand it better.
 

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When you think about it, this also explains why adding "stuffing" to small enclosures with a high Q improves the perception of transient response. The fill material attenuates the ringing produced by the system, thus leading to the false assumption that the smaller box is "quicker" regardless of the compliance of the suspension.
 

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Nope. Damping is control. Springiness is the opposite of control. That's what the shock absorbers in your car do. When your shocks are bad, the car bounces around when you go over a bump. Drive over a big bump with no shocks and you may find yourself struggling to keep your car on the road.

The box stiffens the spring. Its effect is similar to the difference between dropping a ripe avocado on the kitchen floor and dropping a super ball on the floor. If "control" has anything to do with finding the avocado vs. finding the super ball after the experiment (and it does), then the air in a small sealed box reduces cone control.

The misunderstanding comes from the fact that the small sealed box reduces cone movement at low frequencies (and thus reduces output at low frequencies), but it raises the resonance frequency and raises the Q which is a measurement of overshoot at resonance (the opposite of damping). When you're talking about cone control, Q is the measurement. Any suggestion that Q isn't material in this discussion is completely wrong.
So this is an old post, but I read this article regarding shocks. Right now I am looking for an infinite baffle, but I would like to comment on this shock assessment.

I enjoy the sound of a sealed box better than ported because I tend to maintain that it is dampened by the air, not spring loaded. I enjoy my bass quick and responsive and YES, there is a SQ difference between the two.

As for the shocks in a vehicle when your shocks go out, yes it is very springy, but that is do to the springs, although this is not a poor comparison.

Associate the SPRINGS with SUSPENSION/ SPIDER of the woofer. What dampens those springs in a car is AIR, specifically nitrogen. Now, no one is going to put nitrogen in there subwoofer box (I hope). Although, 78% of our air is made up of nitrogen.

This Nitrogen in the shocks of a car is what gives you the smooth ride.

The subwoofer "engine" is magnetic which is also an amazing dampener in itself given that the amp and the driver has the power to control itself, but add an air "shock absorber" to aid that magnetic engine and it should serve to dampen the spring/ suspension/ spider of the subwoofer itself.

Thats just my take on where I stand on sealed/ ported. Perhaps a good radiator would be the "high road" on this debate j/k.

I would like to address the sealed box increasing the subs ability to handle more power. That is a complete falsehood created by manufactures. A sealed box may actually cause a driver to NOT be able to handle as much power due to the trapped heat the box would cause. In this case the power a sub can handle is designated by the driver of the woofer and that's the only thing.

Regarding bottoming out, that shouldn't happen assuming all of the specs are followed and its a decent sub. That would be the job off the "spring"/ spider, in the car analogy, not the shock.

On the other hand the sub will REQUIRE more power to create more SPL as it does have a very intensive dampening system which will indeed dampen some of the bass that you want as well as the resonance that you don't.

I hope this makes sense. I prefer the sound of a sealed subwoofer as most of the music I listen too is Rock with fast changing bass tones, but I have also heard some excellent ported systems as well.

I wish that the old "BOOMY" vs. "TIGHT" bass description were true, but it is just simply not that black and white anymore.

Around 20 year ago, when I first got into car audio, that was an easy description to go by, of course, then I didn't car too much about sound quality, just simply LOUD SOUND.
 

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The problem here, really, is terminology and definition. Infinite Baffle really means just that: infinite baffle. It's the baffle sizes' effect on the low end response. If a baffle is only 20" square and the driver is in the center, there will be no reinforcement of the sound wave below some frequency - let's say 330hz. The larger the baffle, the more reinforcement you get down to a lower frequency. So, let's just say you use a baffle size of 40" square. You get a rolloff at 160hz. *these numbers may not be correct; I can't recall 100% that 13400/x/2 gets you there or not*
So, the idea of using an infinite baffle is to decrease the baffle rolloff frequency by providing more surface area for the soundwave reinforcement.

The term has shifted to describe an infinitely large enclosure.


Now, what I've bolded...
The qts of a driver is just that. But, when you wire one or two or more together, you change the final "Q". Heck, wiring a DVC sub can change that from wiring one of the voice coils up. You'll even notice some mfg's spec a wiring configuration for a specific wiring load if the sub has DVC's rather than SVC. Just something to consider when doing your modeling. This is why box programs have that section for wiring... the section so many of us (I'm guilty as well) skip over without paying attention to. Use it.


You got the box size correct. Really, infinte, as we use it is impractical. Just get a rough idea of your trunk size and model it. At some point, making it larger and large in the simulation has no effect and is nebulous.

As far as picking a sub by its Qts, it's a place to start, but you have to factor in the other T/S parameters as well. Not all 10", Qts=0.34 subs are created equal. I wouldn't get hung up in the differences of 1/10, but if you start going beyond that and box size is important to you, it begins to become a factor.



This isn't really true. The problem is the relationship of the placement of the driver and the listener vs the environment. That's why some will swear they've heard a difference when they move their sub to X location and people refute the idea with the (erroneous) logic of "subs have long wavelengths".

If the placement of the woofer happens to cause a boost in response due to constructive correlation then you'll get increased output at some frequency. If the reflected signal comes back out of phase at the listening position, you'll experience a null at some frequency.


Then you have the effect of room modes which, as I've found, affect frequencies as high as 600hz.
The transfer function of a room or vehicle given certain dimensions will create reinforcement and also dips in a frequency response, from my db drag days I can confirm it’s very real regardless of what people believe or choose to argue with and refute ??

I’m not disagreeing by the way, more reinforcing what happens in real life ??
 

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So this is an old post, but I read this article regarding shocks. Right now I am looking for an infinite baffle, but I would like to comment on this shock assessment.

I enjoy the sound of a sealed box better than ported because I tend to maintain that it is dampened by the air, not spring loaded. I enjoy my bass quick and responsive and YES, there is a SQ difference between the two.

As for the shocks in a vehicle when your shocks go out, yes it is very springy, but that is do to the springs, although this is not a poor comparison.

Associate the SPRINGS with SUSPENSION/ SPIDER of the woofer. What dampens those springs in a car is AIR, specifically nitrogen. Now, no one is going to put nitrogen in there subwoofer box (I hope). Although, 78% of our air is made up of nitrogen.

This Nitrogen in the shocks of a car is what gives you the smooth ride.

The subwoofer "engine" is magnetic which is also an amazing dampener in itself given that the amp and the driver has the power to control itself, but add an air "shock absorber" to aid that magnetic engine and it should serve to dampen the spring/ suspension/ spider of the subwoofer itself.
Please use the word damping instead of dampening which sounds like making something moist, which is a word people don't like for some reason.

Nitrogen in the shocks of a car create damping by forcing the nitrogen to squeeze through a tiny hole, like trying to breathe through a plastic drinking straw as narrow as a spaghetti noodle. If there were small air passages in a speaker that also restricted the passage of air, then the woofer would be damped by the air restrictions no matter what enclosure you use including ported, sealed, and even zero enclosure like infinite baffle. This is not the case because woofers are generally designed to have air passages large enough to not damp the motion of a cone like a nitrogen shock absorber does.

The motor (or the engine as you call it) usually has 10x more damping than any mechanical portion of the speaker, or the enclosure, or anything else (except for aperiodic vents but I don't think you're talking about those). This is easily visible on a spec sheet by comparing Qes to Qms. Qes is calculated from damping caused by electrical means (the motor, voice coil, and amplifier) and Qms is calculated from damping caused by the mechanical means (spider, surround, air flow restrictions, etc). The Qes is usually less than 1.0 and the Qms is usually around 10. The mechanical damping component is 1/10th as effective as the electrical damping component in this case and is essentially insignificant. You can also see by looking at Qts which is the combination of Qms and Qes. The total Q of a woofer is almost exactly the same as the electrical Q of the woofer because the mechanical damping has such a tiny influence relative to the electrical damping.

To see this for yourself, tap on the dust cap of a speaker connected to an amplifier that is powered on. Then unplug amplifier and tap again. The motion of the cone is tremendously less "controlled" (damped) when the amplifier is disconnected and the cone will ring for a much longer time (actually about 10x as long if the Qms is 10x as large as the Qes).

But seriously though, if you like the sound of sealed box then just enjoy it.
I'm not trying to change your mind, just trying to help with your understanding of how stuff works.
 
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