# Small sealed box= MORE cone control



## BuickGN

This is one I see a lot, a small sealed box offers more cone control than a large sealed box or IB. My opinion is a small box means less cone control and drives down efficiency and this is why over damped subs (.4 Qts and lower) work best in small boxes.

I write this because I read nearly every day that small boxes increase cone control. I think people get confused that limiting excursion and controlling the cone is the same thing when it's not. And also that high Qts subs are usually referred to as having more damping and control when I believe the opposite to be true. 

It seems like the old way of thinking that IB "needs" a high Qts sub is starting to go away.

I guess .707 vs .5 critically damped Qtc would be for another thread lol. 

Maybe this is another topic but why would you ever limit excursion mechanically with the air spring of a small box, reducing efficiency when you can do it electronically and retain efficiency? This is assuming your install allows a large box or IB. Serious question. 

Am I right, wrong, thoughts?


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## [email protected]

Control by the air spring resulting in better transient response is not a myth.


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## BuickGN

BeatsDownLow said:


> Control by the air spring resulting in better transient response is not a myth.


That was an excellent rebuttal but you got anything to back that up? I'm pretty sure its the other way around.


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## Spyke

IMO, I don't think it really matters what the qts is. I have always preferred high qts when doing ib for car doors and such(5-8" drivers). I have never done an ib sub install but i've used a set of very low qts 5.25's and those things put out incredible bass, well incredible for 5.25's. They would blur mirrors and give a bit of chest thump. The downside is that they sounded like **** for any kind of midrange. So just based on my experience with that I would say low qts ib subs should do well. 

I get your point though. The size of the box doesn't dictate cone movement the amplifier and source unit do that. A small encl will prevent over excursion to a point but while doing so will prob limit eff. (oh you just said that) I think people think that way because you can dump a **** ton of power into a small encl without it distorting. On the other hand you need a **** ton of power because it's a small encl.


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## GouRiki

BuickGN said:


> It seems like the old way of thinking that IB "needs" a high Qts sub is starting to go away.


Hey Buick-

I just wanted to add I've used a pair of 10"s with qts of .37 in IB and spent a good amount of time listening to a pair of 12"s with a qts of .47 in IB.

As far as the 10"s go, I loved the sq in IB considerably more than when they were sealed in a .6 cu ft per driver box. The low end extension was also much nicer, limited by the subsonic.

My w15 GTI has a qts of .48 based on the spec sheet and no one will argue that sub doesn't perform well in IB.

Sorry don't know enough to put any science behind what I hear. But I can say I have really good hearing :laugh:.


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## BuickGN

Here are some links that support my argument of smaller box= less cone control and worse transients.

subwoofer

I don't know how many times I've heard it...but it doesn't matter how many times...it's still wrong.

Putting a subwoofer in a smaller box does not increase power handling, it simply reduces efficiency and thus requires a larger amplifier. When designing a subwoofer especially one using equalization like a Bi-Quad (Linkwitz Transform) one of the primary considerations is the amplifier power required to drive the cone to it's maximum linear excursion. A bigger number here is a bad thing...not a good thing. The smaller the box, the bigger this number will be so you may want to look at the curve generated by your Linkwitz Transform software and think it is telling you that you have very high power handling but that's not what it's telling you. It's telling you that you have a very high power requirement...not power handling. It's probably telling you that the thermal limitation of the voice coil will be reached long before the excursion limitation. Contrary to popular belief, that's not a good thing. When I 'm designing a subwoofer I'm hoping that curve will tell me that 10 watts will drive the woofer to it's maximum excursion. Of course this is a very unrealistic expectation but it would be a very good thing if it were possible. 

"I have +/- 25 mm linear excursion and I get it at 20 Hz with 10 watts"! Not... "I've got +/- 25 mm linear excursion and it would take 25,000 watts to exceed it at 20 Hz so I've got great power handling...I never have to worry about bottoming"! That second statement is just the wrong way to look at it folks! The less power required to bottom the woofer the better!

What your subwoofer can produce at any given low frequency is determined by one thing and one thing only. It is determined by how much air volume the woofer can displace. So, if my unrealistic subwoofer idea above were possible, it would get the most out of the woofer with just a 10 watt amplifier. If on the other hand someone has told you that you can increase your subwoofers power handling by putting it in a smaller box you will likely end up with a subwoofer that can no longer reach its full potential. With the smaller box, you have introduced a second limitation on what your woofer can produce, that is, the thermal limit of the voice coil. 

*A stiffer restoring force from the smaller box does not, "increase cone control". This is determined by the damping of the system. Qtc is Qtc...and this is what describes the control of the cone motion. Actually, decreasing the box size will increase Qtc and thus increase the chance of ringing...it will reduce cone motion control.*

So, smaller box...more power required, possibly beyond the thermal limit...not more power handling. Also, smaller box...less control of cone not more control. 

So if all the above is true how do we stop a woofer from bottoming? Well, we stop driving it in such a way as to bottom it! The question is, what is the woofer capable of based on its excursion limits. Once we know this, we can determine what HP filtering can resolve the problem. It could be that this woofer just can not produce 20 Hz at 115 db like you might want it to. That might require several times the excursion limit of the driver depending on what driver you are using. So, if you don't want it to bottom you just can't try to make it do something it can't do. Putting it in a smaller box isn't going to somehow magically enable it to do the 20 Hz at 115 db. The only viable solution is to use a HP filter. Just as with all speaker building this will be based on a balance of trade offs. If you want 20 Hz you will need to settle for less than the 115 db you hoped for or optionally you can keep your 115 db and settle for something higher than 20 Hz. You can't have both unless you get more or bigger woofers. No smaller box will change this. So, the solution is to use a HP filter to limit your woofer to a frequency range it can handle at the output level you desire. That's how you prevent bottoming, you don't put it in a smaller box and thus in a position such that it can never reach it's full potential.

Keep this one thought in mind, Infinite Baffle is better than sealed box. Infinite baffle has always been better than sealed box and it will always be better than sealed box. What is a smaller box doing? Moving farther away from infinite baffle! So, acoustically, a bigger sealed box is always better than a smaller one. The limitation should be based more on space limitations because making it smaller will never be a move toward optimization. Depending on the Q of the driver a very large box might move Qtc below the desired level but this can be corrected using the Linkwitz Transform. So the, "too big" box is still better assuming you correct the Q with a bi-quad. Of course a point of diminishing return can be reached with the box volume as the restoring force of the box becomes very small relative to that of the driver. At some point the large sealed box is essentially infinite baffle so making it bigger beyond this is not necessary.


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## BuickGN

Another: IB subwoofer FAQ page



"9) How do I choose my drivers?

Look for woofers with a Qts that is in keeping with the sonic characteristics you want. Generally a low Fs is desirable, however drivers with a higher Fs will work, they simply require slightly more EQ. (Note; contrary to popular belief driver and and do play well below their Fs) 

10) Which Qts/Qtc should I chose?

For an IB, the Qtc of the system is approximately the Qts of the driver. If you like very tight bass, chose a lower Qts driver. If you like the "HT" sound, then chose a driver with a higher Qts." 


Hmmm low Qts for "tight bass". BDL, would you consider this good transient response as most do? A box raises Qtc and does not help with cone control. It's starting to look like smaller box= worse transients.


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## Spyke

Very nice write up. You were just hoping for someone to disagree with you weren't you?


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## Spyke

Buick, Can you suggest a good/free enclosure calculator? I currently use winisd but am looking for something that takes xmax into account.


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## BuickGN

Spyke said:


> Very nice write up. You were just hoping for someone to disagree with you weren't you?


Nah, not at all. I wish I could take credit but I didn't write the last couple of posts up. I just wanted to get the enclosure size vs cone control discussed, I've never seen it as a topic, just touched on in other threads. 

Part of what triggered it was going IB. I expected to have this slow, sloppy bass from what I've read on the internet but it was a real surprise when it sounded so much more natural and "quick" than the same subs in a sealed box.


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## Spyke

BuickGN said:


> Nah, not at all. I wish I could take credit but I didn't write the last couple of posts up. I just wanted to get the enclosure size vs cone control discussed, I've never seen it as a topic, just touched on in other threads.
> 
> Part of what triggered it was going IB. I expected to have this slow, sloppy bass from what I've read on the internet but it was a real surprise when it sounded so much more natural and "quick" than the same subs in a sealed box.


Be careful describing a sub as "quick". I can imagine what you mean but I can't think of a good way to describe it.(this just based on those low q 5"mids I had) The bass was very clean almost surreal. I would love to hear some ib 15's. Is that what you have? I do like higher q for mids but I think it might be beneficial to use low q subs.


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## minbari

I dont disagree with you one bit. over damped with a really small box means the more the sub moves, the harder it has to work to move. this is exponential since the farther you compress the air the stiffer it gets. the stiffer it gets the less likely it is to faithfully reproduce the waveform.

also, if you look at cone excursion on really small boxes vs larger boxes, it tells it all.


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## underdog

What i think i learned? 
In a vehicle there is not true IB.
large enclosure. Yes
You mount them in a sealed trunk: Measure the Sq Ft of trunk 
You mount them where the back seat was: Measure the Sq Ft of cabin

So what we are really looking at is very large or small enclosures.
There is supposed to be an ideal Q number when you get the sub and enclosure together. 
".707 (which some consider a perfect q)." 

Ready for my learning


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## Patrick Bateman

BuickGN said:


> Nah, not at all. I wish I could take credit but I didn't write the last couple of posts up. I just wanted to get the enclosure size vs cone control discussed, I've never seen it as a topic, just touched on in other threads.
> 
> Part of what triggered it was going IB. I expected to have this slow, sloppy bass from what I've read on the internet but it was a real surprise when it sounded so much more natural and "quick" than the same subs in a sealed box.


Have you ever listened to one of those 'boom' cars, where the bass is super loud, but the notes seem to resonate forever? Instead of a nice tight bassline, you get this big boomy bass with no definition?

That's due to resonance in the enclosure. (not the box, but the woofer alignment)

So you get this super high efficiency, but the group delay is horrendous. 

Something similar happens with small sealed boxes. 

That's the bad news. 

The good thing is that it's all relative. If you put a woofer with a qts of 0.6 in a small sealed box, you might end up with a QTc of 1.2. But if you stick with a lowish qts, you won't get those obnoxious resonant beats. 

Basically there's nothing wrong with small sealed boxes, as long as the final QTC isn't too high.


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## GouRiki

underdog said:


> What i think i learned? In a vehicle there is not true IB.
> large enclosure. Yes


From the way I understand Infinite Baffle, it is possible to replicate IB in a car. 

For example, take a pair of 10" subs, qts of .37. 
Per specs, they are designed for .6 cu ft sealed enclosure each, so 1.2 cu ft. total
If I want them in IB, model them in an enclosure 3x the recommended, which gives me a flatter graph. 
Compare that graph to my trunk size, ~15.5 cu ft, the graph doesn't change from the 3x normal spec enclosure (3.6 cu ft)
Compare that graph of the trunk space to 1,000 cu ft., graph doesn't change again.

IB is an enclosure "infinitely" large so that the enclosure no longer affects the response of the drivers, with the front wave and rear wave "infinitely" separated, correct? 

Then by that definition, for those subs, I've created an IB situation in my trunk, since the space doesn't affect the response, correct?


Now situation #2, take some high qtc or multiple drivers, and you will not get the same affect. Depending on the size of the trunk and the sub(s) used, it would possibly just act like a large box at that point.




underdog said:


> You mount them in a sealed trunk: Measure the Sq Ft of trunk
> You mount them where the back seat was: Measure the Sq Ft of cabin


It doesn't matter which way the subs are facing. The cabin is suppose to be sealed from the trunk so the smaller volume of the two (cabin vs trunk) will be considered the enclosure. 


Please correct me if I'm wrong guys, I'd like to learn too and this is just what I've picked up along the way so far.


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## ErinH

Patrick Bateman said:


> Basically there's nothing wrong with small sealed boxes, as long as the final QTC isn't too high.


Agreed.


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## BuickGN

I have to say, I'm a bit surprised at the responses so far. I thought more people would be opposed to the idea.


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## ErinH

GouRiki said:


> From the way I understand Infinite Baffle, it is possible to replicate IB in a car.
> 
> *For example, take a pair of 10" subs, qts of .37. *
> Per specs, they are designed for .6 cu ft sealed enclosure each, so 1.2 cu ft. total
> If I want them in IB, model them in an enclosure 3x the recommended, which gives me a flatter graph.
> Compare that graph to my trunk size, ~15.5 cu ft, the graph doesn't change from the 3x normal spec enclosure (3.6 cu ft)
> Compare that graph of the trunk space to 1,000 cu ft., graph doesn't change again.
> 
> IB is an enclosure "infinitely" large so that the enclosure no longer affects the response of the drivers, with the front wave and rear wave "infinitely" separated, correct?
> 
> Then by that definition, for those subs, I've created an IB situation in my trunk, since the space doesn't affect the response, correct?
> 
> 
> Now situation #2, take some high qtc or multiple drivers, and you will not get the same affect. Depending on the size of the trunk and the sub(s) used, it would possibly just act like a large box at that point.


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. 



GouRiki said:


> It doesn't matter which way the subs are facing. The cabin is suppose to be sealed from the trunk so the smaller volume of the two (cabin vs trunk) will be considered the enclosure.
> 
> 
> Please correct me if I'm wrong guys, I'd like to learn too and this is just what I've picked up along the way so far.


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.


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## ErinH

BuickGN said:


> I have to say, I'm a bit surprised at the responses so far. I thought more people would be opposed to the idea.


what idea? That a small box = more cone control? It just seems like a blanket statement to me. I think it has to do with the system and application as a whole rather than just one component. I use a Alpine Type-R 10" shallow sub in my wife's car. The enclosure is a measly 0.38ft^3 (net), stuffed with fill, and it performs well. It doesn't dig low, but that was a given and not an issue for me. 
It models at a Qtc of about 0.68 and the real life measurements give me 0.697. 
Here's a screenshot of the model:











This model shows the box unstuffed with a Qtc of 0.84. You can see the FR sims compared as well.











If I told you I was using a box that small, without mentioning the subwoofer and goals of the system, you'd think I was stupid. I'd think I was stupid... but then I'd ask some follow up questions. 
Things in subwoofer land have changed a lot since I've been in car audio... and that's only been about 5 years.


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## BuickGN

Patrick Bateman said:


> Have you ever listened to one of those 'boom' cars, where the bass is super loud, but the notes seem to resonate forever? Instead of a nice tight bassline, you get this big boomy bass with no definition?
> 
> That's due to resonance in the enclosure. (not the box, but the woofer alignment)
> 
> So you get this super high efficiency, but the group delay is horrendous.
> 
> Something similar happens with small sealed boxes.
> 
> That's the bad news.
> 
> The good thing is that it's all relative. If you put a woofer with a qts of 0.6 in a small sealed box, you might end up with a QTc of 1.2. But if you stick with a lowish qts, you won't get those obnoxious resonant beats.
> 
> Basically there's nothing wrong with small sealed boxes, as long as the final QTC isn't too high.


I agree. I should have been more specific in my original post. I assumed the "small sealed box" meant a very high Qtc.


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## BuickGN

Erin, the purpose of this thread was to discuss the blanket statement that's always thrown around that a smaller box equals more cone control. Usually used when talking about IB, some people act as if the cone will just flop around uncontrollably if the box is taken away. I know Qts matters and Qtc is ultimately what matters but regardless of Qts, wouldn't you say that putting any sub into a smaller enclosure causes it to have less but not necessarily too little "cone control"?


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## GouRiki

Thank you for the explanation Erin. There's so many factors to consider, and lots more reading to do 

Also on a sidenote, going along with Spyke, what box building software do you recommend Erin? I notice you are using BassBox Pro on what you uploaded. And I guess from looking around PWK uses his own custom software to take into account cabin response and location correct? Just wondering what would be an all around good program to get a close approximation of performance in a car. I just fiddle with WinISD.

Oh and I posted in one of your threads, I was wondering if you could point me to a pic of the finished product of the kicks you showed in Bing's installer review subforum. Sorry for being off topic...


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## ErinH

I use BBP, correct.

You can use Jeff Bagby's stuff though:
jbagby

It's free.


I'll post in the other thread about the kicks.


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## Spyke

Patrick Bateman said:


> The good thing is that it's all relative. If you put a woofer with a qts of 0.6 in a small sealed box, you might end up with a QTc of 1.2. But if you stick with a lowish qts, you won't get those obnoxious resonant beats.
> 
> Basically there's nothing wrong with small sealed boxes,* as long as the final QTC isn't too high.*


Agreed. I used to have 10" in a .63 sealed with a qtc of .7 and it sounded great, I kinda wished it was more boomy actually.


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## Niebur3

So, for arguments sake (and hopefully this is enough information), lets compare a couple of scenarios (assume all have the same x-max and power available)....

1) a subwoofer, say 15" that has a QTC of .3 in infinite baffle and when tested in car, it has a final QTS of .35....what characteristics about how this setup should sound like should one expect?

2) the same subwoofer now put in an enclosure that models to a final QTS (in car for arguments sake) of .707. Is the cone experiencing more control from the enclosure? How does this sound as compared to the IB install?

3) Same as #1, except the sub has a QTC of .65 and a final QTS of .707 infinite baffle. Will this sub sound the same as the sub in scenario #2?

Furthermore is air spring represented in the QTS? If not, how would that further impact the sound?


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## BuickGN

Niebur3 said:


> So, for arguments sake (and hopefully this is enough information), lets compare a couple of scenarios (assume all have the same x-max and power available)....
> 
> 1) a subwoofer, say 15" that has a QTC of .3 in infinite baffle and when tested in car, it has a final QTS of .35....what characteristics about how this setup should sound like should one expect?
> 
> 2) the same subwoofer now put in an enclosure that models to a final QTS (in car for arguments sake) of .707. Is the cone experiencing more control from the enclosure? How does this sound as compared to the IB install?
> 
> 3) Same as #1, except the sub has a QTC of .65 and a final QTS of .707 infinite baffle. Will this sub sound the same as the sub in scenario #2?


Thanks, Jerry, those are the kind of questions I was trying to ask.


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## sqshoestring

I always thought the whole idea of using a qts .7 sub IB was because you ended up with a proper Q= .7. That was before everyone had unlimited EQ power, in fact hardly anyone had much EQ power so it sounded like crap if you did not tune the sub correctly. Yes some cars were different/etc, but it got you close. Today you can use about anything, subs are much better so even with bad tuning you can EQ out your odds of getting a sub that does something strange is pretty slim. That said I still like to error on install tuning, its way easier to tune and rarely does something I don't like....bigger drivers look cooler and are more efficient, etc. It often makes the install harder though.

The only cone control I know of, is with a cheap sub a smaller box will control it enough to allow it to handle more power. This will result in more spl in higher frequency if it does not blow up from thermal load. It will keep the cone from xmax as soon at low frequency you are not going to be hearing much of....lol. I don't know what this has to do with SQ so I never paid that much attention to it excepting some cheaper mids/woofers I installed AP to 'control' them more lol. If you don't have a real capable xover it can help you out, since I used AP more or less as a high pass.

Cone control, funny. Not much different than 1,000 watts which tells you nothing about sound quality or how loud it can get. I like IB because the cone does move, and makes me bass. No cone moving means no bass, excepting at port tuning of course if you have a vented enclosure. By far the cone moves where the amp tells it to, above anything else.


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## BuickGN

That's just it, I was saying that a box does not control the cone, other than to reduce efficiency. My theory is that the box reduces the damping which I might be correctly or incorrectly associating with control.


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## ChrisB

Dang, I was going to say that my experience with small, sealed box, 10" subwoofers were that they made great midbass drivers. I was going to go with the pre-fab Audio Integrations subwoofer enclosure for the WRX, but, I have yet to be wowed and amazed with the output from a single sealed 10" subwoofer.

I believe I would like 3 IB 10s better than a single sealed 10... Now to find 3 decent IB 10s. I need to remeasure because I may be able to do 3 12s IB without manifolding them.

EDIT: I almost forgot... If you want cone control, build a servo drive!


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## Hanatsu

Bigger sealed enclosure (lower Qtc) sound cleaner imo, they lose power handling but in a SQ oriented system that may not matter. Group delay is a derivation of frequency response, so if you EQ a bigger/smaller enclosure to produce the same FR I bet noone can tell the difference between them. Small enclosures should have higher non linear distortion. Qtc between 0,6-0,9 often work pretty good in a car. Go for a lower Qtc if you got the space and EQ down the extended lower response to decrease cone movement and you should have pretty clean sounding subbass. Combine low Le with low Qtc and transistant response should theoreticly be as good as possible. Then again, it's so hard to control the enviroment in a car so the small differences might not be noticable. Modes and resonances are the two most important factors for crappy response. A good parametric EQ can make lot of systems sound pretty damn good. 

Ported might even be a better solution if you can EQ the peak created. I can't tell the difference between sealed/ported when FR is EQed to same curve.


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## [email protected]

BuickGN said:


> That was an excellent rebuttal but you got anything to back that up? I'm pretty sure its the other way around.


Ya, here is a article by JL. 

JL Audio » header » Support » Tutorials » Tutorial: Sealed Enclosure Characteristics


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## BuickGN

BeatsDownLow said:


> Ya, here is a article by JL.
> 
> JL Audio » header » Support » Tutorials » Tutorial: Sealed Enclosure Characteristics


I wouldn't use that as your rebuttal. There are too many glaring mistakes to believe anything in that article such as using a larger box decreases efficiency yet they also mention a larger box decreases power handling. Now which one is it? Every knowledgeable source seems to point toward a small enclosure decreasing cone control.


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## [email protected]

BuickGN said:


> I wouldn't use that as your rebuttal. There are too many glaring mistakes to believe anything in that article such as using a larger box decreases efficiency yet they also mention a larger box decreases power handling. Now which one is it? Every knowledgeable source seems to point toward a small enclosure decreasing cone control.


 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.


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## BuickGN

BeatsDownLow said:


> 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.


You're spreading myths. Subs geared toward sealed enclosures don't always have softer suspensions. My IB specific subs have an extremely soft suspension to the point I thought John forgot the spiders. 

The suspension seals the subs and centers the cone. The motor controls cone motion above Fs. 

Making the diaphragm hard to move is not the same as cone control. Overshoot is a lack of cone control and the smaller the box, the more overshoot you get. I don't know about you but I would rather have the VC controlling the cone, not an air spring. 

Attack and decay being considered quicker in a sealed box is not because of the air spring, that's your own assumption. 

Lower Qts is more damping. Higher Qts is less damping. The smaller the box, the less damping.


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## 07azhhr

Control can be good and it can be bad. In this case the air spring effect is actually a resistance or limiting form of control. To me this is a negative form of control. I have always looked at this topic as you need more power to control the cone in a smaller box. I say it this way because you are fighting this air spring that is constantly applying an opposite force on the cone and suspension. With an opposing force you have a chance of causing the weakest part of the speaker to give a little. This can lead to non linear movement of the cone. Since the music signal is always changing direction fast the air spring is also changing in the opposite direction. With little power the spring might actually win. With more power you can more effectively push/pull thru this resistance (the air spring) and have better ability to prevent non linear movement i.e. more cone control.


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## 14642

BeatsDownLow said:


> Control by the air spring resulting in better transient response is not a myth.


 
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.


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## BuickGN

As always, thanks for your thoughts Andy.


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## 14642

BuickGN said:


> You're spreading myths. Subs geared toward sealed enclosures don't always have softer suspensions. My IB specific subs have an extremely soft suspension to the point I thought John forgot the spiders.
> 
> The suspension seals the subs and centers the cone. The motor controls cone motion above Fs.
> 
> Making the diaphragm hard to move is not the same as cone control. Overshoot is a lack of cone control and the smaller the box, the more overshoot you get. I don't know about you but I would rather have the VC controlling the cone, not an air spring.
> 
> Attack and decay being considered quicker in a sealed box is not because of the air spring, that's your own assumption.
> 
> Lower Qts is more damping. Higher Qts is less damping. The smaller the box, the less damping.


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.


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## legend94

bikinpunk said:


> Things in subwoofer land have changed a lot since I've been in car audio... and that's only been about 5 years.



as some know i took a sabbatical for about the last 5-6 years and getting back into car audio it seem that subwoofers have made the most advancement and next to that power is cheap(probably because its made cheap )


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## legend94

Andy Wehmeyer said:


> 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



nearly made me shart and great explanation


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## Spyke

BeatsDownLow said:


> 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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## legend94

Spyke said:


> 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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## Niebur3

Andy Wehmeyer said:


> 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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## 14642

Niebur3 said:


> 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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## BuickGN

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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## BuickGN

BeatsDownLow said:


> Control by the air spring resulting in better transient response is not a myth.


Looks like it is a myth afterall. 



BeatsDownLow said:


> 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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## 14642

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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## Niebur3

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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## ErinH

I know to some this is stating the obvious but others may benefit a lot from looking at his to get a general idea of what a damping ratio is:
http://www.physicsforums.com/showthread.php?t=144248

http://en.wikipedia.org/wiki/Damping


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## BuickGN

Andy Wehmeyer said:


> 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.


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## BuickGN

Andy Wehmeyer said:


> 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?





BuickGN said:


> 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.


I swear I saw the bolded after I had posted my reply lol. I wasn't trying to copy Andy.


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## 14642

BuickGN said:


> 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.


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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## thehatedguy

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.



BuickGN said:


> 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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## Chaos

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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## jackal28

Andy Wehmeyer said:


> 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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## dumdum

ErinH said:


> 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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## Justin Zazzi

jackal28 said:


> 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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## jackal28

Your right, sorry, I meant damping not dampening. Autocorrect is a pain.


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