# Noobish question but I've never heard it answered fully. Sealed vs IB and output....



## BuickGN (May 29, 2009)

I'm still not understanding why a sealed box would have more output than an IB in any frequency range. Ported is obvious so I'll leave that out.

If the same sub in both configurations can hit xmax over it's intended frequency range, how can the sealed setup offer more output? I've heard acceleration as an answer but at a given excursion at a given frequency how can acceleration be any different?

I hear the fact that IB setups can take less power than sealed thrown around as a con but if it takes less power to hit full excursion, isn't this a very good thing? 

What's the big piece to the puzzle that I'm missing or is this one of those myths like a small sub is quicker and large is slower? If two identical subs are moving the same distance, how can one be louder than the other?


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## cobra93 (Dec 22, 2009)

If I understand your question correctly, acceleration does make a difference.
I don't think I would be able to explain this without hanging myself. 
This was a good read and the reason for posting it here. I don't know if you've run across this before.
All else being equal, more power and acceleration will make a difference.
This is exactly what a (sealed) box allows you to do.

The relationship between Xmax and SPL - SSA Car Audio Forum

I hope this helps.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

I'm in the position to agree with buickgn.

Lets take two identical subs. Meaning both measure the same. Now put one in the ideal box, and put the other in IB. Give each one enough power to reach xmax at 20hz in their repective setups. Now, at 20hz, they should reach the same spl, given that they are mounted in the same place and orientation in a car.

If they are both playing 20hz, and they are both hitting the same xmax, acceleration cant come into play. If it did, then it wouldnt be playing a true 20hz anymore, and the waveform would deviate. The only way that one sub could accelerate faster in this scenario would be if one was playing a clipped 20hz tone.


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## cobra93 (Dec 22, 2009)

I'm not an authority on this subject by any means.

If you put a sealed box woofer in it's ideal enclosure and an infinite baffle woofer in it's respective ideal enclosure, they are now in their ideal "box". The IB woofer is just a much larger box, correct.

From what I understand, a sealed box woofer is able to handle much more power due to the box helping the suspension do its job.

The equation> force= mass x acceleration has to apply to this situation as well.

If all else is equal (displacement), then power handling is the only differential.
The sealed woofer will handle more. A doubling of power, to a point, is a +3 db gain.

If sealed vs. IB doesn't matter from an output standpoint, why don't you see more 10" or 12" IB systems? I only see builds with as much cone area as people can fit, usually 15" or 18" in multiples. These aren't spl builds either. They typically SQ builds.

I wish I had a better understanding of the why and could prove what I believe to be correct, but I don't, so my argument could be incorrect.


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## BuickGN (May 29, 2009)

cobra93 said:


> I'm not an authority on this subject by any means.
> 
> If you put a sealed box woofer in it's ideal enclosure and an infinite baffle woofer in it's respective ideal enclosure, they are now in their ideal "box". The IB woofer is just a much larger box, correct.
> 
> ...


The problem with that is while it can take more power in the sealed box, it requires more power to hit the same excursion. It just seems like if anything you lose a bunch of efficiency in the sealed box. I'm sorry I haven't had time to read the link you posted, it's the GF's birthday and I'm sneaking posts in when no one is looking.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

That was exactly what I was thinking. If both subs are playing a 20hz tone, and both speakers are hitting 20mm xmax, then acceleration cant be different, because if it was, one of them wouldnt be playing 20hz (unless one was playing a clipped tone)

That said, spl is created by moving air, no? So if both speakers are displacing the same amount of air (identical size and xmax) and at the same speed (20hz) then power and box type shouldnt matter, sealed vs ib at least.

I think that double the power only adds 3db before xmax comes into play. If you have a speaker thats hitting xmax, and then you double the power, you'll mechanically damage the speaker, and wont gain any spl. On the other hand, if your giving a speaker 300 watts, and its hitting half of xmax, then doubling power should give a 3db gain, but you'll also be doubling the excursion to xmax.


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## XtremeRevolution (Dec 3, 2010)

BuickGN said:


> The problem with that is while it can take more power in the sealed box, it requires more power to hit the same excursion. It just seems like if anything you lose a bunch of efficiency in the sealed box. I'm sorry I haven't had time to read the link you posted, it's the GF's birthday and I'm sneaking posts in when no one is looking.





TOOSTUBBORN2FAIL said:


> That was exactly what I was thinking. If both subs are playing a 20hz tone, and both speakers are hitting 20mm xmax, then acceleration cant be different, because if it was, one of them wouldnt be playing 20hz (unless one was playing a clipped tone)
> 
> That said, spl is created by moving air, no? So if both speakers are displacing the same amount of air (identical size and xmax) and at the same speed (20hz) then power and box type shouldnt matter, sealed vs ib at least.
> 
> I think that double the power only adds 3db before xmax comes into play. If you have a speaker thats hitting xmax, and then you double the power, you'll mechanically damage the speaker, and wont gain any spl. On the other hand, if your giving a speaker 300 watts, and its hitting half of xmax, then doubling power should give a 3db gain, but you'll also be doubling the excursion to xmax.


People have hit insanely high SPL levels with low excursion, high sensitivity subs. Its not just about SPL.

Power increases output regardless of of excursion. If you reach excursion much too quickly in an extremely large box (IB), you will not reach the same output as a sealed box that controls excursion. All sub box modeling software will reflect this. 

Most subs that are designed for IB have a stiff enough suspension so that it will compensate for the lack of air suspension in what would otherwise be a box. Of course, increasing suspension stiffness requires an increase in motor strength, or a decrease in efficiency. 

Its complicated, but the general idea is that if you can give a sub 500W to reach xmax in a sealed box, and 250W to reach xmax in infinite baffle, the sealed box will be louder. You could find another sub that can handle 10,000W, put it in a sealed box that controls excursion, and given the same piston area, it will still be louder than the aforementioned 500W sub. 

Like I said before, its not just about xmax. I'm much too tired to explain it all right now, but model it for yourself and you'll see what I mean.


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## ErinH (Feb 14, 2007)

XtremeRevolution said:


> *People have hit insanely high SPL levels* with low excursion, high sensitivity subs.* Its not just about SPL*.


Not sure I understand what this is supposed to mean. Typo? Otherwise, you seem to contradict yourself... well, not even contradict... the sentence just doesn't make sense. At least to me. 

Regardless, of course people can hit high SPL levels with little excursion when you fail to mention surface area. If you're moving a volumetric unit of air then you need both xmax (length) and surface area (height*width). I think most of us here would agree without mentioning both parameters, the information isn't enough to draw a real conclusion unless you assume the parameter not given is the same between compared units.




XtremeRevolution said:


> Power increases output regardless of of excursion.


until you reach driver failure or, if the driver is built well enough, it's made to protect itself in extreme situations. If the driver does jump out of the coil, though, and you blow the VC, you short the circuit and the amp's output no longer matters. right?




XtremeRevolution said:


> Power increases output regardless of of excursion. If you reach excursion much too quickly in an extremely large box (IB), you will not reach the same output as a sealed box that controls excursion. All sub box modeling software will reflect this.


I'm not saying you're wrong, but I'm not following this either. If you have two identical woofers and one is pushed 'harder' than the other, thus pushing it beyond xmax, doesn't the one with further xmax have the higher spl, given it doesn't blow out of the basket regardless of how hard it's pushed?
Unless, of course, you're talking about running a sub so damn hard it's no longer linear and is just flopping around; gap-stopping itself to the point where it literally has instantaneous pauses in movement because it's crashing in to the basket or jumping out of the coil. 




XtremeRevolution said:


> Most subs that are designed for IB have a stiff enough suspension so that it will compensate for the lack of air suspension in what would otherwise be a box. Of course, increasing suspension stiffness requires an increase in motor strength, or a decrease in efficiency.


Agreed. Although, I'm not versed enough in the equations to know if the last sentence is completely true. 




XtremeRevolution said:


> Its complicated, but the general idea is that if you can give a sub 500W to reach xmax in a sealed box, and 250W to reach xmax in infinite baffle, the sealed box will be louder. You could find another sub that can handle 10,000W, put it in a sealed box that controls excursion, and given the same piston area, it will still be louder than the aforementioned 500W sub.


While I understand where you're going and agree for the most part, I don't know if you can generalize _that _much. If you take two woofers designed for IB, put one in a small box (say, 2ft^3) and another in the typical car trunk (say, 10ft^3) and apply power to them, you will likely bottom the IB one first as you apply the same amount of power. However, you'll likely find that although you hit xmax sooner, your low end response is better on the lower powered, IB, setup even before hitting xmax. A subsonic filter (aka: high pass) will remedy this; if it's even needed given cabin gain and the fact that most won't be pressing the driver that hard that low. 

Here's an example I managed to throw together. Go easy... I haven't modeled a woofer as much as you have this month.  

Sub: AE IB15
Yellow is sealed. 2ft^3. 500w
Red is sealed. 10ft^3. (note: anything larger becomes moot). 250w. 

Excursion plot:










You can see here that the IB woofer (red) clearly reaches xmax before the yellow (2ft^3) woofer enclosure. Note the xmax for the IB occurs @ ~25hz. This is key.

Now look at the SPL between the two. Again, yellow = 2ft^3 and red = IB.











While the SPL is higher for the small sealed enclosure for the most part, the IB setup has more output (higher SPL) below 40hz. That means there's a good 10-15hz range where the IB-type setup outperforms the small sealed setup on numbers alone at half the power. 
Also notice how steep the rolloff of the small sealed enclosure is. Consider the standard bandpass for subwoofers in a car for _our_ purposes (ie: not the neighbor kid wanting to hit every bass note below 200hz like it's a world record attempt). 

We can certainly change parameters, etc around to fit any argument we want to make. I just did the above to show that it's hard to pigeonholed one design over another absolutely. 





OT:
Notice how the high Q of the 2ft^3 enclosure causes a bump @ ~85hz. This will sound HORRIBLE in the car. The Q is >1. I wouldn't touch that with a twenty foot pole.


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## sonikaccord (Jun 15, 2008)

A sealed box acts as a physical high-pass right? In that case you should be able to add a subsonic to the IB sub to imitate a sealed box response. It's impossible for the sealed box to be louder if both subs are moving the exact same amount of air.


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## BuickGN (May 29, 2009)

XtremeRevolution said:


> People have hit insanely high SPL levels with low excursion, high sensitivity subs. Its not just about SPL.
> 
> Power increases output regardless of of excursion. If you reach excursion much too quickly in an extremely large box (IB), you will not reach the same output as a sealed box that controls excursion. All sub box modeling software will reflect this.


I can see this in a ported setup. How can power increase SPL if excursion does not increase in a sealed or IB setup? How is 20mm excursion from a sealed box any different than 20mm in IB?

I thought high sensitivity meant less power required for a given excursion?


XtremeRevolution said:


> Most subs that are designed for IB have a stiff enough suspension so that it will compensate for the lack of air suspension in what would otherwise be a box. Of course, increasing suspension stiffness requires an increase in motor strength, or a decrease in efficiency.


My IB15s are over 91db efficient and don't have a lot of motor strength. They seem to have a pretty loose suspension right until you get to the limit of travel, well past xmax. Just from a "primitive" push test, pushing on the cone, the IB15s feel like they forgot the spider they're so "loose". I don't want to mis-quote John but I remember something about the motor controlling the cone and not relying on the suspension.


XtremeRevolution said:


> Its complicated, but the general idea is that if you can give a sub 500W to reach xmax in a sealed box, and 250W to reach xmax in infinite baffle, the sealed box will be louder. You could find another sub that can handle 10,000W, put it in a sealed box that controls excursion, and given the same piston area, it will still be louder than the aforementioned 500W sub.
> 
> Like I said before, its not just about xmax. I'm much too tired to explain it all right now, but model it for yourself and you'll see what I mean.


I just don't get it. If you add power but have no physical reaction, how does it get louder? The only difference I can see is that you have to use a subsonic in IB to limit excursion which the box does for you in a sealed setup.

Lastly, I'm not in any way arguing, I realize I still have a lot to learn which is what I'm trying to do. This one thing keeps popping back in my mind and it will bother me until I understand it. I have tons of respect for all of the work you've done around here.


sonikaccord said:


> A sealed box acts as a physical high-pass right? In that case you should be able to add a subsonic to the IB sub to imitate a sealed box response. It's impossible for the sealed box to be louder if both subs are moving the exact same amount of air.



That's exactly the way I'm thinking.


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## BuickGN (May 29, 2009)

bikinpunk said:


> Not sure I understand what this is supposed to mean. Typo? Otherwise, you seem to contradict yourself... well, not even contradict... the sentence just doesn't make sense. At least to me.
> 
> Regardless, of course people can hit high SPL levels with little excursion when you fail to mention surface area. If you're moving a volumetric unit of air then you need both xmax (length) and surface area (height*width). I think most of us here would agree without mentioning both parameters, the information isn't enough to draw a real conclusion unless you assume the parameter not given is the same between compared units.
> 
> ...


I finally got a chance to look at this. Is it safe to say that if you increased the power in the IB setup as frequency rises to keep it right at xmax or 500w (which ever comes first), the IB would have roughly the same output as the sealed even past 40hz? Or said another way, with an intelligent sub sonic filter, shouldn't the IB setup have at least the same output as the sealed from 20hz all the way up?


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

I like this thread. I wish there were more like this. My basic question still stands.

Lets take a theoretical sub. Lets say that in true infinite baffle, it will reach xmax at 20hz at 250watts. Lets say this same sub will take 500 watts to reach xmax at 20hz in a 3cf box. Lets say xmax is 1 inch, and total surface area is 100 square inches.

So, you take a room that is 100 cubic feet. This is the listening area. Put a hole for the sub, and mount it true infinite baffle, and give it 250 watts, and play a 20hz tone through it. The sub will be displacing 100 cubic inches of air every stroke, and lets say that gives an spl of 100db, in the center of the room.

Now, take that sub, put it in a 3cf sealed box, and mount that box to the same hole. Give it 500 watts, and play a 20hz tone through it. The sub will still be displacing 100 cubic inches of air every stroke, and it would be impossible for the spl to be any different than 100db.

How, mathematically, could the 2x increase in power, add 3db, if the cone is moving in the same pattern, and displacing the same amount of air, and being that spl is a measurement of pressure?


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## BuickGN (May 29, 2009)

From the earlier link, I saw this:

*" It stands to reason that as the voice coil moves out of the gap, BL decreases, and based on our previous conclusions, so does the rate of acceleration! In this sense, high Xmax is a good thing because it means the driver is capable of moving further without an alarming decrease in BL. In this sense, high Xmax is a great thing. A driver that can move great distances while keeping BL very linear can make for a very good, very loud driver. This is handy for competitions like Bass Race, where everyday music is played for longer durations.

With that said, there is another aspect of SPL competitions where high Xmax may not matter so much. In DBDrag style competition, high Xmax is not always critical. Typically, a competitor plays a short burst sine wave near the resonant frequency of the port(s) used in their enclosure. This excites the air mass in the port, causing it to become the primary source of our pressure. Meanwhile, the driver that is exciting the air mass is relatively stationary; it is not excurting itself very much at all. If your driver is only moving +/- 2mm, what is the difference in BL between a driver with 16mm of Xmax and a driver with 100mm of Xmax? Not much at all."*

I think the second part only applies to ported boxes playing only at their resonant frequency and the first part could apply to ported, sealed, and IB that play actual music. Am I wrong?


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## BuickGN (May 29, 2009)

Found this old one also.

http://www.diymobileaudio.com/forum...aller-enclosures-have-higher-maximum-spl.html


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

I didn't read it all BGN... BUT.. my understanding is this... 

IB= zero natural boost (hence the flat signal shown above and the hump on the sealed box)
Sealed = +3db
Ported= +6db
Bandpass= +8-9db 

This gets accentuated by transfer function...


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## turbo5upra (Oct 3, 2008)

My take. not that it matters: This doesn't belong in the dumb ? forum 

In my girlfriends car with 2 10's it will go really low... and rather violent @ low frequencies. 

If you could put a subsonic filter on the IB setup and feed the subs the same amount of power the whole way across the board it should be equally as loud.

I think the issue with ib not being as loud comes with trying to keep them together on the bottom end and building the training wheels in.

I don't really see how a cone moving the same distance (full xmax) @ the same speed (hz) it could be louder.


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## XtremeRevolution (Dec 3, 2010)

turbo5upra said:


> My take. not that it matters: This doesn't belong in the dumb ? forum
> 
> In my girlfriends car with 2 10's it will go really low... and rather violent @ low frequencies.
> 
> ...


Then you entirely miss the point of power handling. Why would we need high powered, high excursion drivers like those from Digital Designs, when we could instead take a ****ty $50 speaker with a high excursion and get the same result? Why do companies make 5000W power handling subs when you could get 15mm of xmax with 100w or less? Why even make a stupidly high powered sub with an enormous motor and a gigantic voice coil when we could get the same excursion with a loose suspension, a small motor, and a light cone?

Sent from my HTC Awesome using Tapatalk


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## turbo5upra (Oct 3, 2008)

XtremeRevolution said:


> Then you entirely miss the point of power handling. Why would we need high powered, high excursion drivers like those from Digital Designs, when we could instead take a ****ty $50 speaker with a high excursion and get the same result? Why do companies make 5000W power handling subs when you could get 15mm of xmax with 100w or less? Why even make a stupidly high powered sub with an enormous motor and a gigantic voice coil when we could get the same excursion with a loose suspension, a small motor, and a light cone?
> 
> Sent from my HTC Awesome using Tapatalk


really confused.... we are talking same sub in ib vs sealed no? if the same sub is moving the same distance at the same speed then??? ib is just taking less power to do it...


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

XtremeRevolution said:


> Then you entirely miss the point of power handling. Why would we need high powered, high excursion drivers like those from Digital Designs, when we could instead take a ****ty $50 speaker with a high excursion and get the same result? Why do companies make 5000W power handling subs when you could get 15mm of xmax with 100w or less? Why even make a stupidly high powered sub with an enormous motor and a gigantic voice coil when we could get the same excursion with a loose suspension, a small motor, and a light cone?
> 
> Sent from my HTC Awesome using Tapatalk



To sell wattz and DB'z and VBA'z... :laugh:


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## sonikaccord (Jun 15, 2008)

XtremeRevolution said:


> Then you entirely miss the point of power handling. Why would we need high powered, high excursion drivers like those from Digital Designs, when we could instead take a ****ty $50 speaker with a high excursion and get the same result? Why do companies make 5000W power handling subs when you could get 15mm of xmax with 100w or less? Why even make a stupidly high powered sub with an enormous motor and a gigantic voice coil when we could get the same excursion with a loose suspension, a small motor, and a light cone?
> 
> Sent from my HTC Awesome using Tapatalk


Hoffman's Iron Law.

That DD sub will probably work well in a small(ish) box, while the $50 will more than likely need a larger box. To get the same output from a smaller box you have to increase power which gives the manufacturer no choice but to raise power handling.


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## ErinH (Feb 14, 2007)

just because a sub has higher thermal/power ratings doesn't mean it will have higher output inherently. some subs simply require more power to achieve the xmax it's capable of. whereas others don't have as much stroke, thus requiring less power to achieve it's maximum limits. 

the reason some are built much more robustly in this regard is because the user will BEAT on the subs. they have to have a way to mitigate the heat properly, otherwise they fail. that's why we see these "SPL" subs that are built like TANKS. The companies developing these particular products know the end user well and design the sub to handle the beating it will certainly receive. it has more to do with design for long term use (and abuse) rather than design for high SPL level for short term. In the short term, the same sub with same Sd but varying xmax will have different attainable levels. The power is required to push the sub to the limits of excursion.


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## TOOSTUBBORN2FAIL (Jan 31, 2011)

XtremeRevolution said:


> Then you entirely miss the point of power handling. Why would we need high powered, high excursion drivers like those from Digital Designs, when we could instead take a ****ty $50 speaker with a high excursion and get the same result? Why do companies make 5000W power handling subs when you could get 15mm of xmax with 100w or less? Why even make a stupidly high powered sub with an enormous motor and a gigantic voice coil when we could get the same excursion with a loose suspension, a small motor, and a light cone?
> 
> Sent from my HTC Awesome using Tapatalk




SPL is still a measurement of pressure. If the cone size is the same, and the excursion is the same, and the tone being played is the same, then the pressure created is the same, period, reguardless of the power it took to get there.


I'm going to say that the only reason high power handling drivers are sold, is because your can then fit more subs in the car, and THAT could increase SPL. 

For example, you could use "Brand A", which needs the whole trunk for airspace, is an 18" speaker and has 1" of xmax, and takes 250 watts.

Now, you could take "Brand B", which needs a 3cf box, is an 18" speaker and has 1" of xmax, and takes 500 watts. 

If you use "Brand A", you can only fit one sub. Lets say its good for 100db, at 20hz, reaching xmax.

If you use one "Brand B", and its playing 20hz, reaching xmax, its impossible for it to be any louder then 100db, because its compressing the air the same amount.

BUT, you could probably fit FOUR "Brand B" subs in your car, because they need less space. Now all of them are playing 20hz and reaching xmax, on 500 watts a piece. You would now be compressing the air FOUR times as much, so you could reach 106db.

Bottom line, SPL is a measurement of pressure. If 2 different subs are compressing the air the same amount, at the same speed, then spl CANT be different, even if one sub needs more power to do it. And if the two subs both are reaching the same xmax, at the same frequency, and are the same size, then they are both doing what was said above.


Its no different than air compressors. If you have two compressors, one tankless, and one with a tank, but both put out 90psi at the line at 50cfm, both are going to power your tools the same, because the pressure at the line is the same.


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## XtremeRevolution (Dec 3, 2010)

I have a bit of time to post this as I'm on my laptop finally. I decided that since I wasn't 100% sure of what the answer would be, I'd try modeling this for myself. 

The sub is the Dayton HO 10. The goal is reaching ~12.3mm xmax in sealed and IB, and determining what power requirement will take you there, and what the modeled output will be. 

Sealed, the Dayton HO 10 requires 13 liters, or .46 cubic feet to hit 12.3mm of xmax at 500W. Output at 30hz is ~101 dB raw. 

IB (modeled at 10,000 liters), the Dayton HO 10 reaches 12.3mm of xmax with 350W of power. At that power level, the output is still at 101dB raw. 

So, I guess I've learned something today. All you really do need is to move air. I should have known, I just finished reading parts of a speaker building book which describes that all you need to do is separate the rear waves from the front waves to prevent frequency cancellation at low frequencies, and that's the sole purpose of a sealed sub or speaker enclosure, with ported and other options presenting output augmentation. 

The numbers don't lie, so I've attached the charts of excursion and frequency response.


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## turbo5upra (Oct 3, 2008)

I would have thought the sealed might have a tick more.... Nice to know it's even.... No wonder her car really doesn't lack output like I was thinking it would.


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## XtremeRevolution (Dec 3, 2010)

turbo5upra said:


> I would have thought the sealed might have a tick more.... Nice to know it's even.... No wonder her car really doesn't lack output like I was thinking it would.


Yeah, I was personally a bit surprised myself. I guess if you have the means to go IB and seal off the trunk perfectly, you're better off than going with a sealed box. The additional power handling in a sealed box at that point is not a benefit, but a requirement to get the same output. In any matter, you can provide that power with less amplifier distortion, less voice coil heat, and less overall distortion.


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## turbo5upra (Oct 3, 2008)

Ib does take a decent amount to maintain control..... We are feeding them 700 and it made a nice change compared to 500 in terms of volume and overall presence.


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## BuickGN (May 29, 2009)

turbo5upra said:


> Ib does take a decent amount to maintain control..... We are feeding them 700 and it made a nice change compared to 500 in terms of volume and overall presence.


I was messing around with a 7hz tone and got to "test" the suspension of the IB15s pretty well by accident. It's definitely not as idiot proof (me being the idiot) as sealed. If I ever go for SPL, probably going to take it from a 20hz/6db filter to a 20hz/24db filter. It was interesting to me that at 20hz/6db you still get a fair amount of excursion at 10hz and less.

Thanks to all in this thread, this question has been bugging me for so long and I thought I was missing something.


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## BuickGN (May 29, 2009)

cajunner said:


> not true.
> 
> you mistake static pressure with that of acoustic pressure, or wave propagation.
> 
> ...



I guess my question is how would this energy dissipation show itself if not in the form of more excursion? Ported was never a question, we all know how that works. Now if you were trying to say the backwave might cause more excursion at the same power level in a sealed box, that would make more sense. How else do you dissipate energy except in the form of excursion and heat?


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## XtremeRevolution (Dec 3, 2010)

BuickGN said:


> I guess my question is how would this energy dissipation show itself if not in the form of more excursion? Ported was never a question, we all know how that works. Now if you were trying to say the backwave might cause more excursion at the same power level in a sealed box, that would make more sense. How else do you dissipate energy except in the form of excursion and heat?


Standing waves aren't as much an issue with cone output and distortion at those frequencies, or we'd all be installing 3" thick open cell acoustic foam or fiberglass lining in our sub box walls. Any standing backwaves that are bounced back into the cone would create distortion. Its a serious issue with home theater speakers, and is extremely noticeable when not implemented properly. I've tried polyfill and had terrible experiences with it. All of the home theater speakers I design and build have 1.5"-3" thick acoustic foam on the walls to eliminate these standing waves. Its extremely fatiguing to listen to otherwise. 

I believe that wavelengths of the frequencies we're referring to are way too large to have any acoustical effect inside the box with regard to standing backwaves. An 80hz tone has a wavelength of 14 feet. The box itself usually absorbs these waves. I've measured the effects of standing waves in home theater speakers before, so this is not just coming out of thin air.


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## turbo5upra (Oct 3, 2008)

Drop ceiling tiles wrapped w/grill cloth makes for attractive budget room treatments....


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## BuickGN (May 29, 2009)

cajunner said:


> It's energy, being forced to go somewhere (in a box) and when you have a conduit for that energy to travel, it's going to act on it, the cone is going to make additional waves at differing wavelengths depending on the amount of force being applied at that same inertial moment, which will increase the pressure directly in front of the cone/port/passive radiator so that you have an increase in SPL.
> 
> In a larger box, you have less energy at frequencies near the combined output which leaves you with less "bump" in the FR.
> 
> ...


Even still, how is this energy going to increase SPL without causing more excursion? I've been modeling sealed vs IB on different subs all morning and it's the same each time. IB has massively more low end and when you start getting into the 40-50hz range, they're either even or sealed has like a .5db bump.


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## BuickGN (May 29, 2009)

cajunner said:


> It's energy, being forced to go somewhere (in a box) and *when you have a conduit for that energy to travel, it's going to act on it, the cone is going to make additional waves at differing wavelengths depending on the amount of force being applied at that same inertial moment, which will increase the pressure directly in front of the cone/port/passive radiator so that you have an increase in SPL.
> *
> In a larger box, you have less energy at frequencies near the combined output which leaves you with less "bump" in the FR.
> 
> ...


Still not getting the part in bold. It sounds like distortion to me, "making additional waves at differing wavelengths" which in this case sounds like they were never in the signal to begin with. I guess another way to say it is do you really _want_ this back wave to act on the cone for SQ?


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## BuickGN (May 29, 2009)

cajunner said:


> now you know why subs/speakers in a box sound "boxy" lol..
> 
> your argument is valid, and it's why so many people like the Open Baffle approach.


Thanks so much! My head hurts now lol.


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## cobra93 (Dec 22, 2009)

In my original post('s), I was looking at this as "Area under the curve". Kind of like a camshaft. 
IB, in my mind, would be like a mild ramp rate, where as sealed would be more like a a solid roller. The faster/steeper the ramp rate of the lobe allows more air into the cylinder, and more potential for more power to be made.
I realize these are two different things completely, just wanted you to understand my thoughts.

This was also my thought relating to cone movement, more power applied to the cone along with more control exerted on the cone by the small volume of air in the box.

I suppose this would also apply to an IB configuration, which would make my original thought incorrect as both could be playing a clipped wave.

If you don't mind, BuikGN, I'd like to post this question in another forum to see if the results are the same or different. Possibly some math shown to back up the conclusion.


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## Moon Track (Mar 10, 2011)

I think three are used incorrect terms. Both designs with equal radiating surface and equal diaphragm movement will be equally loud. 
Speaking globally, the closed box is more efficient. 
To achieve a good low end response both designs use the resonance of whole system. In IB or closed box design, to have a similar response shape you should have similar resonance characteristics. Assuming that the weight of membrane is equal for both designs there are two springs affect on this resonance. Ideal IB uses only one big “rusty” spring - suspension. 
Closed box design uses two smaller springs , suspension and air stiffness. No necessity to speak that the air is a much better spring with low losses.


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## BuickGN (May 29, 2009)

cobra93 said:


> In my original post('s), I was looking at this as "Area under the curve". Kind of like a camshaft.
> IB, in my mind, would be like a mild ramp rate, where as sealed would be more like a a solid roller. The faster/steeper the ramp rate of the lobe allows more air into the cylinder, and more potential for more power to be made.
> I realize these are two different things completely, just wanted you to understand my thoughts.
> 
> ...


Of course. I've already linked it in other forums. The more people the better. I would love to hear other forums' opinions.


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## BuickGN (May 29, 2009)

Moon Track said:


> I think three are used incorrect terms. Both designs with equal radiating surface and equal diaphragm movement will be equally loud.
> Speaking globally, the closed box is more efficient.
> To achieve a good low end response both designs use the resonance of whole system. In IB or closed box design, to have a similar response shape you should have similar resonance characteristics. Assuming that the weight of membrane is equal for both designs there are two springs affect on this resonance. Ideal IB uses only one big “rusty” spring - suspension.
> Closed box design uses two smaller springs , suspension and air stiffness. No necessity to speak that the air is a much better spring with low losses.


How can the closed box be more efficient when it requires more, usually twice the power down low to produce the same SPL?

Why do you need these "springs" when you have the motor that controls the cone? Why would you want the motor to work harder to overcome both suspension and air pressure? I doubt there will ever be a scenario where the suspension of an IB is as stiff as the air spring of a sealed box.

Like I've said before, my IB15s feel so loose by pushing on them that it feels like they forgot the spider. It seems like the suspension locates the cone and prevents over excursion and the motor does all of the work.


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## XtremeRevolution (Dec 3, 2010)

BuickGN said:


> How can the closed box be more efficient when it requires more, usually twice the power down low to produce the same SPL?
> 
> Why do you need these "springs" when you have the motor that controls the cone? Why would you want the motor to work harder to overcome both suspension and air pressure? I doubt there will ever be a scenario where the suspension of an IB is as stiff as the air spring of a sealed box.
> 
> Like I've said before, my IB15s feel so loose by pushing on them that it feels like they forgot the spider. It seems like the suspension locates the cone and prevents over excursion and the motor does all of the work.


You need suspension to counter the momentum of the moving mass of the cone. Some cones are heavier than others to handle a greater deal of power. Some subs like the idmax and the jl w7 are built with much lighter cones, high power handling, and a lighter suspension. 

The motor doesn't control the cone, the motor moves the cone. However, when you have a cone that's moving on its own against the direction the signal is sending it, you're creating an opposing current and altering impedance. The suspension is necessary.

Sent from my HTC Awesome using Tapatalk


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## BuickGN (May 29, 2009)

XtremeRevolution said:


> You need suspension to counter the momentum of the moving mass of the cone. Some cones are heavier than others to handle a greater deal of power. Some subs like the idmax and the jl w7 are built with much lighter cones, high power handling, and a lighter suspension.
> 
> The motor doesn't control the cone, the motor moves the cone. However, when you have a cone that's moving on its own against the direction the signal is sending it, you're creating an opposing current and altering impedance. The suspension is necessary.
> 
> Sent from my HTC Awesome using Tapatalk


That would make sense, since the IB15's cone is extremely light for a 15. I guess that's why the suspension seems pretty soft. I remember from some reading of John's a long time ago that the motor does control the cone to some degree though. I'll have to freshen up on that subject. By control, I mean start and stop the cone, maybe I'm using the wrong term.


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## sonikaccord (Jun 15, 2008)

I thought I read somewhere that the motor does most of the controlling in IB and the suspension is supposed to just be there to keep the VC centered and prevent it from jumping the gap.


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## XtremeRevolution (Dec 3, 2010)

BuickGN said:


> That would make sense, since the IB15's cone is extremely light for a 15. I guess that's why the suspension seems pretty soft. I remember from some reading of John's a long time ago that the motor does control the cone to some degree though. I'll have to freshen up on that subject. By control, I mean start and stop the cone, maybe I'm using the wrong term.


Well, the motor doesn't technically stop the cone. If you cut out the suspension, apply a force to the cone using an electrical signal, then cut it off right as the cone reaches a peak, the only thing that will be pushing it back is the surround. The motor is only there to work with the electrical signal moving through the coil(s). The motor does control the cone in the sense that it produces the sound, so a perfect sine wave test tone will have a peak to peak excursion. However, I wouldn't say that the motor itself does anything to counteract the inertia of the cone's moving mass. 

For the record, the IDMax's suspension is pretty soft as well, but then again, the cone's weight competes with that of the JL W7, which while being overpriced, is a sub I greatly respect. A lot of research and technology went into both of these subs to make those cones as light as they are and allow such a high power handling.


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## XtremeRevolution (Dec 3, 2010)

sonikaccord said:


> I thought I read somewhere that the motor does most of the controlling in IB and the suspension is supposed to just be there to keep the VC centered and prevent it from jumping the gap.


This is true in the case of subs with very light cones, as there isn't much inertia to counteract.


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> not true.
> 
> you mistake static pressure with that of acoustic pressure, or wave propagation.
> 
> ...


I do not agree with you some of the points you made here, and let me explain why. 

Many subwoofers and home theater speakers are built close to a "Golden Ratio." A box built close to the golden ratio "reduces or cancels out the standing waves inside an enclosure which improves sound quality and reduces distortion."

Vented Ported Subwoofer Box Enclosure Calculator Speaker Cabinet Program

You said that the only place for those standing waves to go is back into the cone, but that's not at all true. The boxes are often built so the box itself absorbs those waves and they simply disappear. It is not something that comes into effect in subwoofer boxes like it does in home theater speakers, where installing acoustic foam or some kind of wall treatment is a requirement. That being said, many subwoofer boxes are built and designed with acoustic foam partially for this reason. The boxes are designed with the golden ratio in mind, with acoustic foam installed so that the standing waves are absorbed, and the result is a cleaner sound. 

Vented boxes don't release this stored energy in a vent in order to create more output. The following is an excerpt from Speaker Building 201, by Ray Alden:


> Bass Reflex or Vented Box: If a vent of some type is placed in a closed box where the driver is playing a range of low frequencies, the mass of air suspended in the vent will be set into vibration at a certain frequency. This is called the tuning frequency of a vented box. In fact, the vibrating air in the vent can contribute greatly to the bass region if carefully calculated.


At this point, we're creating an augmented output that's not coming directly from the cone moving air, but from the port itself. Even in a vented box, the acoustical backwaves are absorbed by the box itself. 

One must be careful how backwaves are used. The introduction of backwaves into the same environment as the frontwaves in bass frequencies results in a cancellation at those frequencies. 

If I merely misunderstood your wording, I apologize, but these acoustical backwaves have nothing to do with the output of sealed boxes, or it would be considered pure distortion.


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## turbo5upra (Oct 3, 2008)

a random thought while I was rolling this around today.... if you play a 45hz note at one volume and then turn it up does it sound the same???

the shape of the wave changes a bit.... it gets taller and the cone has to travel farther. therefore the cone is traveling faster playing the same frequency. Anyone have any input?


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> a lot of bad science going on here, the motor does in fact control the cone, it's the coil part of the magnetic field interplay that is direct in it's function of making electric energy transform into acoustic energy.
> 
> light cone, heavy cone, doesn't matter.
> 
> ...


That's a bold statement to say that I'm spewing a lot of bad science with nothing more than disagreeing statements. 

If electrical energy is required for the motor to create "acoustical energy," then the motor is not controlling the cone; its creating the movement. Controlling implies that something is counteracting a force that is being applied. If the motor is providing that force, how is it controlling that very same force?

Why do you think 99.9% of all subwoofers ever made have a specific suspension compliance? Just to prevent them from bottoming out? Why don't we all then just create subs with absolutely no suspension whatsoever, and place them in sealed boxes that create all the suspension compliance we'll ever need?

The surround is not there to provide absolutely any braking. It is there to seal the cone with the frame, and nothing else. If you have proof of your claims otherwise, please post it. Its the suspension/spider that creates the braking and creates that compliance. The surround does not provide any compliance. 

Also, the weight of the cone matters a lot. JL Audio didn't put so much into their resources to create a more light and rigid cone with the W-cone in their W7 just so you could come around and claim they're all idiots because it doesn't make a difference.


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> it's not my wording that is the problem.
> 
> I didn't say "standing waves" because that's a whole 'nother can of worms.
> 
> ...


You stated words such as acoustical energy; things you can hear. How exactly was your choice of words correct. I quote you:



> not true.
> 
> you mistake static pressure with that of *acoustic pressure*, or wave propagation.
> 
> it's simple, in a box the wave to the rear of the speaker is trapped, it's energy has to be dissipated somewhere, and the cone is the only thing that can do it.


What wave exactly are we talking about here? There are no waves. Any acoustical waves are absorbed by the box. The only function of a sealed box is to separate the front acoustical waves from the rear, and the side effect is a controlling of the excursion of the box by way of air suspension. 

Please don't tell me I'm getting mixed up in my thinking. I was trying to be civil. If you need to clarify what you said, please do so, because I've been doing this for a while and if I can't understand what the hell you're saying and its creating a misunderstanding, you need to be more clear.

You seem to be consistently confusing waves with pressure. You bounce between words such as sonic energy, acoustical energy, and "energy" in general, which by the way is an extremely vague term. 

Kinetic activity is defined as "energy that a body possesses by virtue of being in motion." How exactly is this sonic energy possessing a kinetic activity of being in motion, and exactly how is it even relevant? 

I'd greatly appreciate it if you stuck to terminology that's more commonly used and more easily understood.


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## ErinH (Feb 14, 2007)

I encourage everyone involved in this thread to give this book a read:
Loudspeaker Design Cookbook 7th Edition Book

There's a lot of things being said here that I'm not on-board with. Keep in mind that the newcomer/ignorant take what is said here as gospel; even if it's wrong. Let's try to make sure we're not leading anyone astray...


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## XtremeRevolution (Dec 3, 2010)

bikinpunk said:


> I encourage everyone involved in this thread to give this book a read:
> Loudspeaker Design Cookbook 7th Edition Book
> 
> There's a lot of things being said here that I'm not on-board with. Keep in mind that the newcomer/ignorant take what is said here as gospel; even if it's wrong. Let's try to make sure we're not leading anyone astray...


I have been reading "speaker building 201," which has been very highly recommended by everyone on techtalk.parts-express.com. I would imagine it is equivalent to the book you just listed with regard to content. Much of what I said came directly out of this book.


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## turbo5upra (Oct 3, 2008)

but bikini said so!


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## XtremeRevolution (Dec 3, 2010)

sorry cajunner, but you have me really confused the F out right now. 

"you mistake static pressure with that of acoustic pressure, or wave propagation."

From wiki:

Acoustic pressure: Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure caused by a sound wave.

Wave Propagation:
Wave propagation is any of the ways in which waves travel.
With respect to the direction of the oscillation relative to the propagation direction, we can distinguish between longitudinal wave and transverse waves.

So you stated it as if they were the same, which they clearly are not. This is just an example of how you've confused the hell out of me by using terminology that is either irrelevant or unimportant. Exactly how is wave propagation even an issue here, or how is it even relevant to this topic?

Sometimes I get the idea that you're using a bunch of terms that you don't really have a firm understanding of. The above quote is one example of why I'd get that idea, and why you're confusing the hell out of me.


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## ErinH (Feb 14, 2007)

XtremeRevolution said:


> That's a bold statement to say that I'm spewing a lot of bad science with nothing more than disagreeing statements.


Well, it may be bold of him, but you're making some boldly wrong statements so...

Keep in mind I don't try to be an ass, so the reply below is my reaction to your statement rather than trying to be a know-it-all on the net behind a computer screen...



XtremeRevolution said:


> Why do you think 99.9% of all subwoofers ever made have a specific suspension compliance? Just to prevent them from bottoming out? Why don't we all then just create subs with absolutely no suspension whatsoever, and place them in sealed boxes that create all the suspension compliance we'll ever need?
> 
> *The surround is not there to provide absolutely any braking*. *It is there to seal the cone with the frame, and nothing else. *If you have proof of your claims otherwise, please post it. Its the suspension/spider that creates the braking and creates that compliance. *The surround does not provide any compliance. *
> 
> Also, the weight of the cone matters a lot. JL Audio didn't put so much into their resources to create a more light and rigid cone with the W-cone in their W7 just so you could come around and claim they're all idiots because it doesn't make a difference.


*WTF?* 

I mean... holy crap, dude. I can understand posting something and saying "I believe" or something to that effect, but you're so boldly wrong it's like having cold water dumped on me when I'm asleep: It's a shock to the system.

Here's why you're wrong:
The surround contributes to the suspension. In one of your paragraphs in the above q uoted, you discuss how important suspension is. Then you say the surround provides nothing to the woofer. Well, that's quite a contradiction because the suspension is influenced by the surround. The surround is part of the driver's suspension. 
I'm just going to type this bit up from Vance Dickason's _Loudspeaker Design Cookbook_ (linked above, and I highly encourage everyone buy it before spouting off driver design trivia):


> The stiffness provided by the surround and spider is usually presented in terms of ease of motion, or compliance (compliance is the reciprocal of stiffness). In terms of the total compliance of the speaker, the spider provides about 80% and the surround perhaps 20% of the total compliance. The surround has two important functions. Its primary job is to keep the voice coil centered over the pole piece; however, damping the vibration modes at the outer edge of the cone is also critically important. The choice of thickness and type of material used in a surround can dramatically alter the response of the speaker. The ability of the surround to damp cone modes and prevent reflections back down the cone can alter both the amplitude and phase of modes combination, making it an integral element of cone design and a viable response shaping tool.


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## XtremeRevolution (Dec 3, 2010)

bikinpunk said:


> Well, it may be bold of him, but you're making some boldly wrong statements so...
> 
> Keep in mind I don't try to be an ass, so the reply below is my reaction to your statement rather than trying to be a know-it-all on the net behind a computer screen...
> 
> ...


Sigh. I am aware of the surround's other functions. I was speaking relative to the topic.

So it might provide 20% of the suspension, which I imagine varies by the speaker being used. I'm currently listening to some aura ns6 based bookshelf speakers I made. I can guarantee you the thin foam surround provides little to no suspension compliance. If it does, its insignificant compared to the spider. I can destroy it without much effort with my fingernail. It does dampen the vibrations, and it does center the cone. Believe me, trying for 3 hours to align an idmax recone with a defective spider taught me at least that much, but its actual compliance as a percentage of measured Vas is insignificant compared to the spider.

Sent from my HTC Awesome using Tapatalk


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## ErinH (Feb 14, 2007)

XtremeRevolution said:


> *Sigh*. I am aware of the surround's *other functions*. I was speaking relative to the topic.


What's with the "sigh"? your posts certainly show no inkling that you were aware. I mean, ****.... look at your statement:


> the surround does not provide any compliance.


anyone reading this thinks you're stating fact. it certainly comes off as such. 
So, how is the surround's influence on suspension now an "other function" when your reply was in direct discussion of that exact feature?

No wonder you and cajunner aren't getting each other. You're walking over your own statements.


Furthermore....
"relatative to the topic"

Well... how is your incorrect statement anymore correct in the context of this thread?


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## ErinH (Feb 14, 2007)

XtremeRevolution said:


> So it might provide 20% of the suspension, which I imagine varies by the speaker being used. I'm currently listening to some aura ns6 based bookshelf speakers I made. I can guarantee you the thin foam surround provides little to no suspension compliance. If it does, its insignificant compared to the spider. I can destroy it without much effort with my fingernail. It does dampen the vibrations, and it does center the cone. Believe me, trying for 3 hours to align an idmax recone with a defective spider taught me at least that much, but its actual compliance as a percentage of measured Vas is insignificant compared to the spider.
> 
> Sent from my HTC Awesome using Tapatalk


With no data to back this up, how do we know it to be true. Things like this is what I try to steer clear of. 
Just because you feel like the surround contributes nothing to the suspension doesn't mean it you're right.


Furthermore, you said the surround is only there to create a barrier (in so many words). In fact, it's there for much more. Your blanket statements are not correct. That's why I'm replying to them. 
Again, we've got people on this forum who will read what one person writes and be the new resident expert. Are we trying to puff chests or are we trying to educate?


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> again, it's energy being dispersed by air molecules. The box does not absorb anything, it reflects or dissipates energy due to vibration, but it doesn't absorb the back wave!
> 
> I think that some of the fundamentals of acoustics have to be understood before even simple statements will begin to make sense.
> 
> ...


So you're telling me that all of our sealed and ported sub boxes are fundamentally made up of a whole lot of distortion, and the golden ratio for a speaker box is entirely incorrect and irrelevant?

Sent from my HTC Awesome using Tapatalk


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## XtremeRevolution (Dec 3, 2010)

bikinpunk said:


> With no data to back this up, how do we know it to be true. Things like this is what I try to steer clear of.
> Just because you feel like the surround contributes nothing to the suspension doesn't mean it you're right.
> 
> 
> ...


Go to your sub or speaker, and use your finger to press down on the surround. Then press down on the cone in a vented box or on a free air sub. Then tell me roughly what percentage of that compliance in the cone, estimated with your bare hands, is coming from the surround itself. It will be insignificant in the majority of cases until you get close to maximum excursion.

I'm trying to figure out what the truth is, while being royally confused, and a bit tired. I should leave it at that for fear of omitting a blatant detail and contradicting myself till I have more time and energy to choose my words more carefully.

Sent from my HTC Awesome using Tapatalk


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> it's not exactly distortion, it's acoustic energy that is added to the original signal to create a higher SPL than unloaded makes.


So you're creating an unpredictable and uncontrolled output from the cone that is not being instructed by the amplifier. How is this not distortion?



> Try and understand quarter-wave theory and how wave propagation inside an enclosure affects the energy at the cone, increasing it at some frequencies and causing nulls and dips at others.


I understand quarter-wave theory. I understand its effects and I understand exactly why we go through such lengths to prevent those standing waves from hitting back into the cone and producing distortion. I say distortion because I have heard it, measured it, and proven that it is distortion in my own test boxes. If you can effectively implement acoustic foam or fiberglass on the inner walls of a loudspeaker, you can significantly decrease the degree to which these standing waves affect output at the cone. It is a very audible difference. 

Its once reason I'm building the Statement Monitors above many other speakers. These have the midrange separated from the box via a transmission line tunnel extending to the back of the box to eliminate all cabinet coloration. 




> the golden ratio is there to create as minimal an involvement by frequencies that act on the cone, as possible. There are still going to be standing waves even in a perfectly executed golden ratio box, but they are lessened by their cancellation inside the box instead of being focused onto the cone's backside.


Perhaps you can see where I get confused when you say things like that, after saying things like this:

"in a box the wave to the rear of the speaker is trapped, it's energy has to be dissipated somewhere, and the cone is the only thing that can do it."

You just specified that the golden ratio does allow these waves to be dissipated, contrary to what you said before. I admit I'm guilty of not choosing my words more carefully or being more clear, but if we're going to point fingers, lets be fair about it. We're not always as thorough or clear as we'd like to be. That doesn't however mean we're entirely wrong in everything we've said. 



> As far as why you mix and match these principles of acoustics to suit a positional stance, I have no good answer but I would believe that it's because you are not knowledgeable enough to explain the differences, because you don't understand the principles themselves.


wtf?



> I'm no authority on this, but I do retain a bit and I've got the cookbook by dickason too, and I've read other books on this stuff as well as many articles over the years.
> 
> I will say that if you study this stuff for a week straight, you're not going to make the same statements you've made tonight.


I've studied this stuff for more than a week straight. I claimed that some of your statements were very confusing, and some of my statements were made out of that confusion and perhaps misunderstanding. Please don't mistake or confuse those with something else.


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> you're trying to understand it as a process of one thing then another, or sequential cause and effect.
> 
> it's not, the electrical energy being transformed into acoustic energy is instantaneous. The movement of this acoustic transform from the coil to the former, and then into the rest of the parts of the speaker, happen in a finite fashion but the actual back and forth by the amplifier's energy, is a function of physical law. The motor IS controlling the cone, more than your suspension parts are by a long shot. There's no "counter-acting" because it's acting all the time, unless you include EMF and all that jazz with phase angle and impedance descriptions that make things more complex.


So you're telling me that if I removed the suspension entirely or reduced its compliance by a crippling amount, that I'd have nearly the same behavior as before?

That's what it sounds like, and correct me if I'm wrong, but "more than your suspension parts are by a long shot" implies it that the suspension is nearly insignificant. 

Modeling alone will demonstrate that doubling or halving the Vas will have a *very *significant effect on the subwoofer's overall output.


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> first off, it's easy to assume a posturing or adversarial viewpoint when being challenged with concepts you are automatically assuming you have a good grasp of, so there's that emotional element at play here.
> 
> I try not to let that get in the way, but I use it to make people think. People do it to me too, it's a vicious circle/cycle.
> 
> ...


Well I'll be damned. 

You know, what you described above is entirely different from what I've been reading from what you've been saying this whole time, and this is not just my attempt to save face. 

I'm not trying to brag, but I'm a really sharp guy. I pick up on things quicker than just about anyone else I know, and I have an ego to deal with as a result. I'm not the kind of guy who will sit there and blatantly and profusely insist that he's right unless he's 100% sure of it. That being said, I will sincerely say I've misunderstood half if not more of what you've said before that post, or I certainly wouldn't have said half if not more of the things I did say. 

I don't disagree with any of what you said above.


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## BuickGN (May 29, 2009)

Back on topic, after modeling this stuff all day, using many different subs in sealed vs IB, the largest difference up top I've been able to produce was 1db with most of the being about .5db louder in the upper frequencies with the sealed setup. So regardless of what's going on inside the box, there's no reason an IB won't be louder down low and about the same loudness as the frequency rises, right?


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## XtremeRevolution (Dec 3, 2010)

BuickGN said:


> Back on topic, after modeling this stuff all day, using many different subs in sealed vs IB, the largest difference up top I've been able to produce was 1db with most of the being about .5db louder in the upper frequencies with the sealed setup. So regardless of what's going on inside the box, there's no reason an IB won't be louder down low and about the same loudness as the frequency rises, right?


That's one thing I noticed as well. If all this energy is stored inside the box and dissipated back into the cone to increase output, why is it that the output of both sealed and IB boxes are so incredibly similar? Modeling a .5 cubic foot box and a 350 cubic foot box while excursion is kept a constant with adjusted amplifier power doesn't show any significant difference, and I've tried every modeling software I have access to. If this was significant and measurable, why is it that it isn't shown in modeling? When excursion is kept a constant, the output is the same in both IB (gigantic sealed) and Sealed boxes.


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> simple question:
> 
> do you have experience trying a sealed box vs. IB installation, in the same car?
> 
> ...


Not many people around here will have that experience, and most people will not have taken the time to measure the output of both. If you run an Infinite Baffle setup, chances are you did it for a reason, not for testing purposes.

I'm tempted to try it, but the amount of work involved is not something I'm ready to attempt.


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## BuickGN (May 29, 2009)

XtremeRevolution said:


> Not many people around here will have that experience, and most people will not have taken the time to measure the output of both. If you run an Infinite Baffle setup, chances are you did it for a reason, not for testing purposes.
> 
> I'm tempted to try it, but the amount of work involved is not something I'm ready to attempt.


Do it! You will love it. Building the baffle is actually very easy. For me, it was easier than building my old bandpass box.

I thank you guys for the interesting conversation.


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## XtremeRevolution (Dec 3, 2010)

BuickGN said:


> Do it! You will love it. Building the baffle is actually very easy. For me, it was easier than building my old bandpass box.
> 
> I thank you guys for the interesting conversation.


I'll think about it. I still need to install my Massive Audio RK6s in doors that were made for 5.25" drivers. Its been a royal PITA so far, so if I can get this to work well and look good, I might try it with my IDMax10.


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## jda123 (Dec 21, 2010)

Couldn't anybody with IB currently in their car just open the trunk to measure the output of sealed vs IB?

More correctly, would this test be high-volume-sealed with deadener vs near-IB?


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## BuickGN (May 29, 2009)

It's obviously not a true IB in a car. Opening the trunk on a couple of my setups like the 12w6 and Tempest X resulted in a big loss of bass. With the IB15s, there's hardly a difference. The one thing I never tried was with the doors and windows closed, hitting the trunk release. I always had the doors open when I hit the trunk. Not sure if the rear wave could cause cancellation or not in that scenario.


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## The A Train (Jun 26, 2007)

I have a scenario I would like to be answered if possible.

Enclosure A: Unknown driver in a sealed enclosure built with .5" wood.
Enclosure B: Same unknown driver in enclosure A, in same interior volume enclosure; built with 1" wood.

My understanding is that in sealed enclosures, the backwaves bounce around in the box and is either dissapated or exits through the cone. In a less dense/stiff enclosure (like enclosure A) there will be more vibration of the box due to acoustic energy inside the box bouncing around hitting the walls. In a very strong box (like enclosure B) the box will vibrate less. The acoustic energy will not be able to be lost in the enclosure structure, so it is forced to be dissapated inside or forced through the cone. 

When I hear that soundwaves are forced through the cone, I think of distortion. Think about it. On the outside of the cone, there will be one frequency played...that same frequency will be played within the enclosure, bounce around and then exit the cone. I see a difference in timing. You will hear the original tone first, followed by the backwave exiting the cone.

Secondly, I believe that the waves inside the box will distort the SQ of the driver. Not only do you theoretically have two tones playing at any given time, but the interior volume is now 'compromised.' The driver is acting as a piston, going up and down. Once there is acoustic energy inside the box, its going to have an effect on the efficiency of the driver.

Am I on the right path here? I have no evidence to back this up, this is just my theory on how it all works. Also I'm not even sure if this is an audible to even worry about.


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## BuickGN (May 29, 2009)

ameuba10 said:


> I have a scenario I would like to be answered if possible.
> 
> Enclosure A: Unknown driver in a sealed enclosure built with .5" wood.
> Enclosure B: Same unknown driver in enclosure A, in same interior volume enclosure; built with 1" wood.
> ...



I'm sure the other much smarter people will be here to answer but this is exactly the way I think of it too. You have energy getting through the cone out of time and possibly different frequencies than what the signal is commanding. My theory is that 1db or so bump from the sealed is 1db of distortion.


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## XtremeRevolution (Dec 3, 2010)

ameuba10 said:


> I have a scenario I would like to be answered if possible.
> 
> Enclosure A: Unknown driver in a sealed enclosure built with .5" wood.
> Enclosure B: Same unknown driver in enclosure A, in same interior volume enclosure; built with 1" wood.
> ...


I'm sure cajunner will disagree on this and tell me I have a lot to learn, but here's what my research has shown so far. 



> as long as the x-over's 1/4 wavelength is longer than any dimension of the box then there is no reflection. This is cause the box just goes through pressure cycles. The whole box being pressurized then not.





> At low frequencies, the air in an enclosure acts more like a hydraulic fluid than a medium in which waves propagate and travel.
> 
> The property of hydraulic fluids that matters here, is that any pressure change in any location of the enclosure is immediately 'felt' (can be measured) to occur any and everywhere else in the box almost instantaneously.
> 
> ...


So long as the 1/4 wavelength of your crossover frequency is not greater than the largest dimension inside your box, the only thing the box will experience is pressure. 

You have to remember, an 80hz wave is 14 feet. That wave won't be long enough to bounce around in a 3 foot max length box. I can see it being an issue up to 100hz, but I don't know who around here actually crosses their subs up to 100hz.

Were this not so, you WOULD be hearing massive amounts of distortion from the waves bouncing back into the cone. I know the effects this causes because I have personally had to deal with them in my home theater speaker designs. Without acoustic foam or fiberglass wall treatments, you *do* get these waves bouncing back into the the cone and creating significant amounts of distortion. You can reproduce this test on your own if you don't believe me. Hell, I will probably measure it for everyone to see soon enough to prove my point once and for all. I've already measured the effects of amplifier clipping with my own RTA software with oscilloscope and RTA software. All I'd need to do is hook this up to my car.


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## sqshoestring (Jun 19, 2007)

BuickGN said:


> Even still, how is this energy going to increase SPL without causing more excursion? I've been modeling sealed vs IB on different subs all morning and it's the same each time. IB has massively more low end and when you start getting into the 40-50hz range, they're either even or sealed has like a .5db bump.


I missed this thread. Bikini hit most of this, but the big reason sealed is 'louder' than IB is because people are talking about SPL frequencies. You have Q or tuning of the sub, and then you have frequency played on it. The box pushes Q up and causes a bump in response (likely your .5db), usually right where you want max output. The sub has been tuned to like that spot; the air spring in the box is tuned with the mass of the cone like the frequency a bell rings at. Given most subs are made to suppress a particular frequency from peaking in the response. This makes it easier for the sub to play that frequency, lets say 50Hz. Why 50, well because most subs can play that really loud without needing much xmax. When you go lower you get limited in output by xmax...the sub will never be able to play lower frequency as loud no matter what because it can't displace more air. Pro systems play loud with larger drivers and low xmax because they are cheap and work well that way, they don't care about large boxes....but they never play that low where xmax starts to matter. They use horns to boost low end without need for big xmax.

The box and IB will be roughly similar in max output at lower frequencies limited by xmax, but the box will require more power to reach xmax as well as more EQ boost to get as flat a response as the IB. It also fills your trunk.

Why go with more cone area IB? More output to start with, but on top of that xmax is a huge problem it makes the sub distort. Sure you can get expensive subs that do not distort at big xmax, if you want to, but they tend to have worse specs for IB including inductance, inefficient, expensive, low qts that gives more rolloff on the bottom, etc. They can work, but if you put a baffle in why not fill it up with the largest you can fit there is no negative in that excepting a couple inches more motor height. Plus odds are you get a driver with a lower Fs that will play lower, it will have more output, more output at less xmax/distortion, just because it is larger. I went beyond that and ran cheaper 15s because I could fit them but figure I didn't need the output of a big xmax 15 in a pair (say the AE IB15 I really liked). Even these pyles showed over 1" of travel in a test before I mounted them, on a 170rms amp and sine tones. So I figure if I use half that it should be pretty low distortion, indeed output is large on my scale at .5" excursion. On the other hand if you want to get something around 20Hz you need to move some air so going overboard is good for that.




BuickGN said:


> It's obviously not a true IB in a car. Opening the trunk on a couple of my setups like the 12w6 and Tempest X resulted in a big loss of bass. With the IB15s, there's hardly a difference. The one thing I never tried was with the doors and windows closed, hitting the trunk release. I always had the doors open when I hit the trunk. Not sure if the rear wave could cause cancellation or not in that scenario.


Mostly it depends on the Vas of the subs. If you are approaching Vas with your trunk it will start to act like a box and roll off the bottom, push up the Q. You will hear it when you open the trunk. If you model a sub at vas (say your trunk is roughly total vas) and then at 10X vas you should see the difference you hear. My 15s are 5cf vas and 15cf trunk, so I am at 1.5X vas. If I model that and compare to 100cf I am losing 1dB at 20Hz and the rest is the same. I can't really hear that difference considering not many notes hit 20hz or hit it strong enough to be fully aware of it. But if I change 20Hz on my EQ it certainly makes a difference with a lot of music. Next on the EQ is 31Hz so it might affect response up to that not sure. It is hard to hear a tone under about 25Hz in my car but I do feel it. Trunk open is no or only slight difference but some stuff in the trunk will start to roll it off.

When I had quad infinity 12s in my car IB it would get really loud at 50-60Hz. I had to EQ and double xover to cut it down near flat. They had Fs 24 and qts .46 (kind of low for IB) and that caused a rolloff on the bottom. I only had 420rms on them and if I didn't EQ and turned the low pass to 80 they would near blow me out of the car at 50. So you can make a SPL type IB system, or close to it, if you use the right subs. These 15s have near the same specs as the AE IB15s and need nearly no EQ to play flat, very impressive bottom maybe the best I have had in a car. But my goal was SQ low as I could get, pretty flat not needing big EQ, would go loud enough to feel it. I have taken out a 500rms amp and put in a 350rms, jury still out but it is not bad this way for my use I don't need to shake the roof of the car really and it overwhelms the mid/highs. Also when I had the 12s in I used a PEQ on them finally to get some control, did not have the 16 band right away. It was awesome I could make those subs sound any way I liked and am seriously considering putting it back in. It worked better than the 16band no doubt, for the subs. The 16 only has 20/31/50/80Hz in the sub range, so I would very highly recommend a PEQ on IB subs if you like to change how they respond. I used an old alpine that only worked under 200Hz. But these pyles sound so nice I'm not in a hurry to find a place to mount the PEQ again.


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## BuickGN (May 29, 2009)

sqshoestring said:


> I missed this thread. Bikini hit most of this, but the big reason sealed is 'louder' than IB is because people are talking about SPL frequencies. You have Q or tuning of the sub, and then you have frequency played on it. The box pushes Q up and causes a bump in response (likely your .5db), usually right where you want max output. The sub has been tuned to like that spot; the air spring in the box is tuned with the mass of the cone like the frequency a bell rings at. Given most subs are made to suppress a particular frequency from peaking in the response. This makes it easier for the sub to play that frequency, lets say 50Hz. Why 50, well because most subs can play that really loud without needing much xmax. When you go lower you get limited in output by xmax...the sub will never be able to play lower frequency as loud no matter what because it can't displace more air. Pro systems play loud with larger drivers and low xmax because they are cheap and work well that way, they don't care about large boxes....but they never play that low where xmax starts to matter. They use horns to boost low end without need for big xmax.
> 
> The box and IB will be roughly similar in max output at lower frequencies limited by xmax, but the box will require more power to reach xmax as well as more EQ boost to get as flat a response as the IB. It also fills your trunk.
> 
> ...


Wow, what a great post, thanks! This answered a lot of questions for me. Going to read it one more time just to make sure I've understood it all.


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## sqshoestring (Jun 19, 2007)

Some subs have a huge Vas, commonly used for HT IB subs into a room/attic/etc. They will change in a car because the trunk is small for the Vas. In general a larger vas is often a more efficient driver, but you can't have your trunk tuning it higher and lose your low bass right....so its a tradeoff. Tiny vas subs are usually for tiny boxes and usually not efficient at all, as well as low qts with big roll off on the bottom. They are built to have the box push Q back up to work right.

Remember in the end you can use a monster xmax sub of near any kind for IB, move lots of air and have lots of output. It might tune terribly and need a lot of EQ, but moving air in the end is the ultimate factor of the output you will get. So tuning an IB sub and looking for pure output are two different ways to get whatever your goal is....or a combination that works for you. I chose a Fs 20 and Qts .7 15" that comes out near flat response in the car, and with a pair its overkill for what I need. The smooth response makes it really easy to tune. Or you could run a JBL GTi and let it wang, you would need some EQ but a sub like that will have significant output. You can run into inductance and other issues especially if you play your sub higher than 80-100Hz or so with big HD subs, but I never play mine that high anyway. Actually cheap subs tend to work well IB because they have smaller motors, maybe are based on older IB designs, etc., but may not have the big xmax or may distort at high excursion.


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## XtremeRevolution (Dec 3, 2010)

I went out earlier and tested out what I said above because I was bored. I measured my IDMax and tried to figure out if these backwaves actually have anything to do with output in a sealed box. 

I hooked it up to my QSC GX3 with an 8 ohm load to get 350W RMS. As noted in the quotes I made, bass frequencies do not create additional output. Its nothing but pressure. You can however hear a distinct resonance/distortion starting at around 150hz, which coincidentally is where the 1/4 wavelength meets the largest internal dimension of that box. Anything above that produced even greater resonances. 

I had a bunch of fiberglass insulation, so I lined the inside of the box with about 6" of it and tried again. Keep in mind, I was running some test music to listen for resonances with my ear, and I ran test tones using TrueRTA with an XLR microphone I had. Starting at around 150hz and up, there were significant distortion readings without fiberglass fill, and nearly no distortion readings with the fiberglass fill inside. 

If anyone needs to see the screenshots, I can run the tests again. I think my point has been made. Sealed boxes do not increase output from bass waves and "acoustical energy" being dissipated back into the cone. Its all just pressure at those frequencies because the 1/4 wavelengths are not long enough to actually bounce off of anything. 

I invite anyone to perform this same experiment if you have any doubts.


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## sqshoestring (Jun 19, 2007)

You will run into reflection/resonance in say a square box with a home woofer that plays higher, but a car sub seems to be out of that realm. There is no reason to use stuffing/insulation except for the dampening effect of stuffing in a small box....which lowers efficiency but flattens response a little. Output is so cheap and easy to get in car subs today I ignore all that stuff that has minor effect on it....it just means nothing unless you are going for low power/high efficiency and nobody does it. Then you would run a much different setup anyway like multiple IB or large ported with efficient subs; something you could run on 100-200w max.


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## BuickGN (May 29, 2009)

cajunner said:


> but what are you proving?
> 
> it's really simple to understand if you take the same sub/amp combo, and do a perfect IB install, or do a box install with a permeable back seat/rear deck.
> 
> ...


That was not my experience when using the same sub sealed and IB. The low end was greatly improved and the upper end hit at least as hard in IB. With a smartly setup SS filter, the IB seems to give up 1db or less up top.


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## XtremeRevolution (Dec 3, 2010)

cajunner said:


> but what are you proving?
> 
> it's really simple to understand if you take the same sub/amp combo, and do a perfect IB install, or do a box install with a permeable back seat/rear deck.
> 
> ...


Not sure if you missed the part where I actually plugged a microphone into my laptop and used an RTA application to measure the differences. Its not a bunch of modeling. Try again. I actually did pull my sub out of my car. Read my post again. 

Is it that difficult to believe that a 1/4 wave that isn't longer than the largest internal dimension in the box cannot physically bounce against anything and be reflected back into the cone? Like I said, I can run the test again, take screenshots, even a video, and upload them here to demonstrate what I tested. This had absolutely nothing to do with sealed vs IB, and everything to do with your claim that you gain additional output in a sealed box because the back waves bounce around inside the box and hit the cone again to create additional output. 

Here you go:

Wavelength

And of course, the below quote stating that a properly done IB setup sounded louder and hit harder. You would think the difference would be more than 1db if you've got a 100+db wave bouncing around inside the box and it only loses 3db per bounce. The truth is that above ~150hz for my box, the difference was much larger than below ~150hz where there was no distortion. However, it was also unpleasant to listen to because it was pure and unquestionable distortion (like anything else that a cone produces that is not specifically instructed by the amplifier), and nobody crosses their sub that high anyway. 

Like I said, you're more than welcome to run the experiment yourself. Hell, you can do it cheap too. Get a coaxial or component speaker, build a box for it out of MDF, and run a few RTA scans at different frequencies and jot down the response and output at those frequencies. Once your 1/4 wavelength of a given frequency is smaller than the longest distance inside the box, you'll start hearing distortion.

I know it, speaker designers know it, everyone who has ever built a speaker without any acoustic foam, polyfill, or sound dampening knows it. Why do you think there's always some polyfill, fiberglass, or acoustic foam in every decent sized speaker? Try taking it out and see how much you enjoy your music. 



BuickGN said:


> That was not my experience when using the same sub sealed and IB. The low end was greatly improved and the upper end hit at least as hard in IB. With a smartly setup SS filter, the IB seems to give up 1db or less up top.


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## jda123 (Dec 21, 2010)

I am testing now. I have no desire to test the same driver in each configuration, rather try and do some near-best-of-class drivers in each class against each other.

Oscilloscope, some huge resistors, SPL meter, FI IB3 15, AE SBP 15 and a sealed 12" FI Q (current)... some of the parts of my ongoing IB vs sealed test.

I tested some pairs of "normal" drivers in IB, but they were not much of a comparison (12w6, T112 and WX33s). Some sounded good, but output of the pairs was way less than the single 12" Q in my car now.

Numbers, pictures and even a video or two are coming when I am done. For now, the amp is measured for wattage at every increment on my HU (at 4 and 3 ohms). The amp settings or signal will not be touched for control. The Q is measured and recorded since it is in already. FI IB3 going in this week some time. The AE will go in whenever (if ever) it gets here.

Any guesses on if a single FI IB3 or SBP will get louder than the 12" Q? Any guesses on the db readings of the IB3 or SBP? I already measured the Q and they will have to play pretty good.

I do expect the IB3 and SBP them to sound terrific.


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## jda123 (Dec 21, 2010)

BuickGN said:


> That was not my experience when using the same sub sealed and IB. The low end was greatly improved and the upper end hit at least as hard in IB. With a smartly setup SS filter, the IB seems to give up 1db or less up top.


Was this on the same signal, or were the W6 sealed on the LOC with the sub signal and then IB with the MS8 with a full-range flat signal? Without a static signal, is this a good test? My sincere apologies if I misremembered what I read from the Acura board.


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## BuickGN (May 29, 2009)

jda123 said:


> Was this on the same signal, or were the W6 sealed on the LOC with the sub signal and then IB with the MS8 with a full-range flat signal? Without a static signal, is this a good test? My sincere apologies if I misremembered what I read from the Acura board.


I only had the MS8 for the last little bit on the W6. I had roughly a week of run time on the MS8/W6 before I went with the Tempest. For the majority of the time is was a traditional post-amp-loc-amp. The Tempest was on the MS8the whole time with a loc and the IB15s started off with the loc and later off of the HU-line driver-MS8 with the factory amp removed.

Without the SS filter, I nearly bottomed the W6 several times. From about 40hz and up you could put some real power to it but without the SS I could never turn it up unless I knew the content had no 30hz and below. On test tones, 40hz was annoyingly loud, 50hz was painful without running out of excursion. However, I could never put that kind of power to them on music without a SS filter or I would kill them. That efficiency down low is great but you have to have the proper safeguards in place or you will kill the subs or you won't be able to put as much power to them up high. I think the majority of the people saying IB doesn't hit as hard or go as loud up high are not sending enough power to the subs due to a lack of a SS filter or not having it set up right. They reduce the gains so that excursion is kept under control in the low end and kill the high end potential.


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## cobra93 (Dec 22, 2009)

BuikGN, i posted this in another forum and got the explanation I was looking for.
I assumed you were looking for output at one freq., sealed versus IB.
I don't know how hard each system would be to tune to flat, but this is the answer I received.

Which makes my initial post incorrect.

These are not my words, but there's the math for proof.


> There's not much to debate. It's a simple fact of physics that in a 2nd order alignment output is directly determined by displacement. The more displacement, the more output. In fact you can figure out the (anechoic) potential output for a given displacement at a given frequency for a subwoofer (or any driver) by the formula
> SPL = 102.4dB + 20log(xmax) + 20log(Sd) + 40log(freq)
> *Sd in square meters; xmax in meters, one-way
> 
> ...


Me>


> I'll try to restate what I believe he's after.
> 
> I assume he means at a given frequency, say 45 hz.
> If both systems are pushed to the same excursion at the same freq. and the woofers are identical. This could be a stretch, but maybe not.
> ...


Answer>


> Same excursion (and assuming same cone area, meaning same total displacement) at the same frequency in the same environment?
> 
> Yes, they would measure the same output.
> 
> See formula previously mentioned in my response to XXXXX.


Me


> Quote
> My original thought was that you could send quite a bit more power to the sealed system and the acceleration of the cone would be faster/quicker. I would think this would make a difference leaning in favor to the sealed system.
> This leads me to my next issue. Both woofers would have to receive the same clean or partially clipped signal in order to compare them.
> I would have to believe that all woofers can play a 45hz freq., let's say just below clipping (an identical wave form) and the faster accelerating cone would achieve a higher (to some extent) output.


Answer


> No, acceleration would be the same. It would be required to be the same by the fact they were playing the same frequency at the same level of excursion. One can't accelerate "quicker" than the other and both play the same frequency at the same excursion level. If the acceleration were different, one driver would necessarily need to either be moving faster in time (different frequency) or moving farther with each stroke (different excursion level). But acceleration would be identical for two different subs moving at the same frequency at the same excursion level.
> 
> The only difference would be the amount of power input required to achieve this condition. One subwoofer might require more power input than the other, which would mean one subwoofer had a higher sensitivity/efficiency than the other at that given frequency.....but that's it.


(Different person) Answer>


> Output would be the same in a perfect world; this is not possible to duplicate in the auto environment though. Perhaps a large anechoic chamber with precision testing instruments and meticulous measurements. Everything equal aside from the alignment, which is what we are debating, will lead to a different response, different peaks, and different bandwidths. Granted the sealed enclosure and IB should be similar, but far from it given the application. We have to think about aiming , reflection, cancellation, etc. . . You may consider this semantics, but it's most relevant due to the nature of the environment.


Answer>


> I think if you break it down to the basics of his question, he's not concerned about environmental affects and more concerned about the basis of the physics involved at the driver level. Which tells us that output would be identical as it's determined by the displacement of the driver for a 2nd order system.


I hope this is the proof you were looking for.


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## jda123 (Dec 21, 2010)

Do you have a single W6 still that you could hook up and test out with your current signal for a better output test? I know that you really like them already, but I think that you will be even more impressed now. The 3G TL stock sub signal already drops probably -6 to -9 db/oct (observation, not measured), so the post-amp LOC even hurt that. It will be louder now and probably sound better, especially down low.

Once you put the MS8 into play, it should have flattened out any/most damage from a LOC before it.

I had to subsonic the "normal" drivers at 28hz (amp setting). Did you have to do this with the Tempest and AE, or are those cool to somewhat turn loose since they are made for near-IB? I can run down to 20hz on my Q with no second thought.


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## sqshoestring (Jun 19, 2007)

I've run a lot of IB, and a box is always perceived to be louder for a number of reasons. I always put more cone area into an IB to make up for it....and because I like big bottom lol. 

The reasons can be:
Box is tuned to 40Hz and higher where you don't have xmax problems.
Box is not going to xmax on lower frequencies, you can wang on it.
IB is not tuned, or, well a good SQ IB is not, for a peak that always sounds 'loud'.
Vented boxes have more output than sealed or IB...where they are tuned to work.
If you have no 30Hz, does the 40Hz+ sound louder? I'd guess yes.
Hardly anything can get as low as IB in a car, but that is near the opposite of 'loud'.
I would always recommend more cone area going box to IB.
Sure a SS filter can help IB if you are near xmax, but it does not push the Q up like a box.

In the end you put in the car what you want, if its not IB then make a box and be happy....box is usually easier to make. IB gets low with ease and leaves an empty trunk. You can build IB to make some SPL but that is not one of its advantages.....why else do SPL comps set records with one sub in a box but IB can win in SQ no problem.

IB is just a big box, while small box 1Kw subs can work in a big box it is often not ideal or not well tuned. Cheap, efficient subs can work quite well IB but may never be impressive in a box or go 'as loud' IB. But if you use more of them you will have some impressive bang for the buck.

Once I ran quad cheap 10s in a car IB. Took them out and put them in a 4cf box, they sounded terrible no bottom but sure they went 'loud'. Ported the box, still not good. Took a pair out and ported again then I could get very close to output of the IB though spl was down a little. Given one car was a 2dr rwd and the other a hatch fwd and it was only my ears. But I would call that a typical comparison. If you run double the driver IB it is usually louder than the box, plus it goes lower and all that. On top of all that making SPL at low frequencies is the hardest thing to do, so you want more/larger IB to make some SPL down there....that is always where any sub will run out of gas first.


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## BuickGN (May 29, 2009)

jda123 said:


> Do you have a single W6 still that you could hook up and test out with your current signal for a better output test? I know that you really like them already, but I think that you will be even more impressed now. The 3G TL stock sub signal already drops probably -6 to -9 db/oct (observation, not measured), so the post-amp LOC even hurt that. It will be louder now and probably sound better, especially down low.
> 
> Once you put the MS8 into play, it should have flattened out any/most damage from a LOC before it.
> 
> I had to subsonic the "normal" drivers at 28hz (amp setting). Did you have to do this with the Tempest and AE, or are those cool to somewhat turn loose since they are made for near-IB? I can run down to 20hz on my Q with no second thought.


First off, I think the Tempest X would have made an amazing HT IB sub. I wish I would've bought all 4 from the guy who was selling them. In the car, they had a TON of low end and hardly anything past 40-50hz. By removing the weatherseal from the trunk temporarily of course and creating a leak, the response smoothed out. The low end was more than the MS8 could take out. I ended up cutting 20-40hz by 10db and boosting 63-80 by 10db to get it somewhat flat. I still have the 12W6, even at $150, no one wants it, I've had literally 10+ buyers who wanted it "right now just give me your paypal address" and they disappeared every time. I threw the old baffle away or I would try it again. Too much trouble now.

The Tempest X was rated at 750w and I had the 1,000w amp's gain turned all the way up. The Tempest seemed to just stop getting any louder past a certain point. Once past about halfway on the volume, it started taking considerably more power to get any louder.

The AEs are very linear, with the gains 1/4 of what they were on the Tempest, they get louder and as you get into higher SPL, they don't require the huge power increases to hear a difference. They sound exactly the same at high volume as low. I accidentally hit them with a 10hz tone without the SS on and at pretty high volume. The excursion was crazy and if it were possible for them to bottom, I'm sure they would have. I've heard they run out of motor at about the same time the suspension is tightening up from the end of it's travel so they can't hurt themselves. There were no bad sounds, no mechanical noises, just a ton of excursion, what looked to be a bit more than the 25mm rated xmech. I would say with the Tempest X and AE you don't HAVE to run a SS just to protect the driver from destruction but it would benefit the system as a whole to have one. I don't like the crazy excursions down low from such a low volume hard to get driver. At my normal listening level you can't even see them move. I think this is the big advantage of two 15s. Even with the Tempest, it moved a fair amount at moderate volumes. The two AEs have no noticeable movement unless you get in the back seat and stare at them. The only time I've pushed them to xmax is when other people want to hear what they will do and of course no one cares about SQ, it's all about SPL to 99% of the population.

The 12W6 definitely needed a subsonic. I never bottomed it but I came close and according to the one tested around here, in free air it will mechanically bottom at 220w.


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## sqshoestring (Jun 19, 2007)

Depends on what you are wanting as to how you run them, SS filter will save power for the amp as well as save the sub from xmax. But some of us put IB in because we want to get to 20Hz....not to use a SS filter to get rid of it. We only want to note what power level xmax comes so we can stay below it. If we need more output we can use more/larger/more xmax subs.


IIRC AEs have braking rings so they really can't bottom unless very overpowered. But when you hit them it controls the cone so certainly it will cause distortion. But right, for normal people a pair of them can produce a lot of output so you do not get to that point. In normal listening my pyles hardly move either, I have to abuse a bass CD to get them flopping around visibly and it overpowers the highs substantially. That is fun for about 30 seconds.


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## BuickGN (May 29, 2009)

sqshoestring said:


> Depends on what you are wanting as to how you run them, SS filter will save power for the amp as well as save the sub from xmax. But some of us put IB in because we want to get to 20Hz....not to use a SS filter to get rid of it. We only want to note what power level xmax comes so we can stay below it. If we need more output we can use more/larger/more xmax subs.
> 
> 
> IIRC AEs have braking rings so they really can't bottom unless very overpowered. But when you hit them it controls the cone so certainly it will cause distortion. But right, for normal people a pair of them can produce a lot of output so you do not get to that point. In normal listening my pyles hardly move either, I have to abuse a bass CD to get them flopping around visibly and it overpowers the highs substantially. That is fun for about 30 seconds.


I love the 20hz output. The MS8 only offers a 20hz and up filter so I'm kind of stuck there. At least it's at a shallow 6db slope. Still though, it has plenty output in the 20hz and even below range. I boosted 20hz by 1.5db to try and make up for the filter. On test tones, you really can't hear a reduction in output at all in that range between but the SS does tone down the useless 10hz range a bit which allows more overall SPL throughout the frequency range and less useless excursion.


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## sqshoestring (Jun 19, 2007)

BuickGN said:


> I love the 20hz output. The MS8 only offers a 20hz and up filter so I'm kind of stuck there. At least it's at a shallow 6db slope. Still though, it has plenty output in the 20hz and even below range. I boosted 20hz by 1.5db to try and make up for the filter. On test tones, you really can't hear a reduction in output at all in that range between but the SS does tone down the useless 10hz range a bit which allows more overall SPL throughout the frequency range and less useless excursion.


Me too. The alpine had a 15Hz SS I tried but it seemed to cut <25 so I turned it off. Not sure yet on this smaller 350rms it acts like it gets up to a point and stops, it bumps nice, but the 500 seemed to have more except it also acted like it didn't have enough gain. This alpine has some auto gain thing I really don't like. Now thinking I want to try a different amp all together to make sure its not the amps. I had a kenwood in there before too when I first put the 15s in but that is all. Some amps they roll off the bottom to save power, because you know, nobody listens to 20 Hz right? Not sure what to try next. It is pretty impressive right now just want to make sure I am getting everything it has to offer. Not been driving that car much since I swapped the 350rms in on subs. I wanted to try to determine if I was getting into compression or xmax with the 500rms, it did get strained with that when I stood on it.

I should take the 500rms and put a meter/scope on it then run test tones and see if it rolls off.


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