late night thoughts about DIY vs Comercial - Page 19 - AVS Forum
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post #541 of 682 Old 03-28-2008, 09:00 AM
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Quote:
Originally Posted by armystud0911 View Post

You are right though, dae3dae's post really does not hold much merit,

Why the personal attack? The absence of the quoted sentence does not change the meaning of your post in the slightest and gets the point across without starting a flame war.

I think you guys that are missing the point of my post.

If I sell an SVS sub to pay for my HSU sub then I don't have the SVS sub anymore. What if I liked the SVS better? In my example I slap the driver back in the old box and all is well.

You are also assuming that all commercial speakers/subs have decent resale value.

IMO the whole ported vs sealed basically comes down to budget. People that have more money than god will throw a ton of money at the solution and end up with a high number of sealed subs. (SteveC will then jump in and tell them they could have had more performance if they had ported the subs.) People on a budget will usually make the decision to build or buy ported to eak every bit of performance (SPL in this case) per dollar.

In my situation, since I am very happy with the sound of my sealed subs I would rather buy two more Sound Splinter drivers and build two dual-driver subs but that would cost $600+ just in drivers and I would have to buy another amp. Instead I am going to try ported and see if it is acceptable. With DIY this is a cheap audition of the build. I can build one ported sub and then compare it to one of my current sealed and see which I prefer. Commercial I would be hosed if I didn't like the new subs better than the old.

Do you still think my original post has no merit?


My subs play all the way down to 0 Hz!!! It's so low you can't hear or feel anything.

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post #542 of 682 Old 03-28-2008, 09:16 AM
 
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Quote:
Originally Posted by dae3dae3 View Post

Why the personal attack? The absence of the quoted sentence does not change the meaning of your post in the slightest and gets the point across without starting a flame war.

I think you guys that are missing the point of my post.

If I sell an SVS sub to pay for my HSU sub then I don't have the SVS sub anymore. What if I liked the SVS better? In my example I slap the driver back in the old box and all is well.

You are also assuming that all commercial speakers/subs have decent resale value.

IMO the whole ported vs sealed basically comes down to budget. People that have more money than god will throw a ton of money at the solution and end up with a high number of sealed subs. (SteveC will then jump in and tell them they could have had more performance if they had ported the subs.) People on a budget will usually make the decision to build or buy ported to eak every bit of performance (SPL in this case) per dollar.

In my situation, since I am very happy with the sound of my sealed subs I would rather buy two more Sound Splinter drivers and build two dual-driver subs but that would cost $600+ just in drivers and I would have to buy another amp. Instead I am going to try ported and see if it is acceptable. With DIY this is a cheap audition of the build. I can build one ported sub and then compare it to one of my current sealed and see which I prefer. Commercial I would be hosed if I didn't like the new subs better than the old.

Do you still think my original post has no merit?

It's simple. You return the Hsu and buy another SVS. You can try out any commercial sub (from the ID companies) with a full return policy. Therefore, you would not be hosed.

He was not attacking you personally.

And being hosed is SUPPOSED to be fun ...
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post #543 of 682 Old 03-28-2008, 10:26 AM
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Quote:
Originally Posted by dae3dae3 View Post

If I sell an SVS sub to pay for my HSU sub then I don't have the SVS sub anymore. What if I liked the SVS better? In my example I slap the driver back in the old box and all is well.

Do you still think my original post has no merit?

I can see your point but like others have said, its a similar, but different all the same, situation with commercial subs. BTW I nobody attacked you personally, at the most they attacked your idea.

Keeping the the driver from an existing DIY and building a new cabinet to create a new sub is equivalent to selling your old commercial sub and buying a new one. You'll lose some on the resale of the old sub for sure but factor in the effort, time and cost of building a new enclosure for the DIY and things round out.

In the vein your heading in, pretty much any argument in favour of DIY can be reversed and done so for commercial.

I still believe DIY'ers are an odd breed that just plain enjoy doing this as a hobby. Some enjoy the designing and wood working just as much as listening to whatever I've built. If your not one of those then there's little benefit to DIY these days UNLESS your going balls deep.
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post #544 of 682 Old 03-28-2008, 10:52 AM
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Dae3: I don't really see how I attacked you personally, if I called you dumb, that would be a personal attack, I simply said I don't think your idea holds much merit.
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post #545 of 682 Old 03-28-2008, 12:05 PM
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Originally Posted by penngray View Post

I would bet they go sealed because of the size issue.

If they can build a sub with a small footprint and HUGE performance then they win because they already know they can easily build a HUGE ported sub and get similar performances.

Size matter in the commercial, yes I keep repeating it, over and over. Those who dont care about having a monster sub that takes up 1/3 of a room are simple a very small minority of people.

The people that have lots of money and are willing to spend lots of money are not going to stick 11cf boxes or silos in any room. Hence, expensive small, sealed subs. (in general, yes some dont mind).

I can see size in the commercial being a big factor; but I also feel sealed brings other things to the table. I would be dissapointed with JL and Dynaudio is the only reason they made a sealed sub was to keep the size down.

I would assume some of the sound charistics of sealed is also why they did this.

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post #546 of 682 Old 03-28-2008, 12:10 PM
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On another topic... I watched a movie last night using my single TC-3000 12" driver in a 1 cube box. I did something new that I don’t usually do; move the sub into a new location and it actually made it sound a LOT better than my existing location.

Unfortunately the sub wants to be located on my staircase. I have an area with some wasted space on a 90 degree turn on my stairs. I think I am going to build a custom compact sub box in the corner where it wont bother anyone.

I don’t know what I would be doing if I went with a commercial design.

In regards to the TC3000 12”, and besides for the REALLY low extension; I was quite pleased with the subs performance. Building the two TC2000 15’s im sure in a sealed box will impress.

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post #547 of 682 Old 03-28-2008, 01:05 PM
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I am sure they would, you could even use them with the TC3000 if you wanted to, then you'd have about 12dB's more output than your current sub.
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post #548 of 682 Old 03-28-2008, 01:11 PM
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Blah blah blah...the tape is an endless loop...I hear the same things recycled over and over.

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #549 of 682 Old 03-28-2008, 01:25 PM
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Quote:
Originally Posted by armystud0911 View Post

I am sure they would, you could even use them with the TC3000 if you wanted to, then you'd have about 12dB's more output than your current sub.

Assuming I want to open the wallet for another amp

Which is actually temping idea lol.

Would I have any issues with group delay or anything like that using multiple sealed subs. (15's and 12's)

I know this issue was brought up when talking about sealed and ported working together.

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post #550 of 682 Old 03-28-2008, 02:04 PM - Thread Starter
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Blah blah blah...the tape is an endless loop...I hear the same things recycled over and over.

We have to waste time somewhere

It is not "open-minded" to reject knowledge - Bob Lee
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post #551 of 682 Old 03-28-2008, 02:56 PM
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Well you got the TC2000's, either you sell them or you power them or you let them sit, its up to you.
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post #552 of 682 Old 03-28-2008, 04:59 PM
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I plan on using them sooner or later. I dont ever plan on selling them only due to its positive history and the parts express pricing puts a smile on my face. Its like having my stocks go up.

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post #553 of 682 Old 03-28-2008, 08:05 PM
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Quote:
Originally Posted by bosso View Post

To try to answer your question, why would a person need a subwoofer at all if he's cost conscious and listens to the music you refer to?

This baffles me, as you really seem to be forgetting that there is a range of bass frequencies greater than single digits, and when it comes to music, the ovewhelming majority of it has bass that does not dip below 30hz. That's precisely why someone would need a subwoofer if they listen to music, be it classical, instumental, rock, pop, jazz, rap, etc. Let's get one thing straight, I'm by no means against single digit extension - the more extension the better - however, to give it the type of priority you do, at the cost of higher frequency performance (which whether you want to admit it or not, will happen, even with quad 15" sealed drivers), when it is rarely if ever observed in music, and is more of a novelty in movies, comes off as an exercise in futility.

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Then why are you commenting as though it matters what you think?

The discussion is about bass performance, and a large ported subwoofer will offer greater performance compared to sealed over at least 75% of the bass range based on where the majority of bass in real media falls.

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Yeah, so your answer is that you would have to build a PR version, or that the driver can't be ported? Because, you know, that would sort of blow your 'driver for driver' spiel. It's YOU who has no ported version to compare it with, and your answer should be that you are mistaken when you say that 'driver for driver, ported is better'. You need to rephrase that statement or continue to sound ill-informed.

My answer is neither, I simply stated that it's easy to look good with no competition, and that is precisely the reason you mentioned that sub. You continue to ignore the perfect comparison that is the TC2k ported vs TC2k sealed. An oddball driver here or there, especially one that costs what the LMS did, was available for as short a period of time as it was, and was specially developed and optimized for the sole purpose of working well in a small, sealed enclosure, is definitely not something that would cause me to change my view.

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You don't have a point. That's the fundamental flaw in your posts.

You're oblivious to the point, that's why you can't grasp it.

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Originally Posted by Thomas View Post

I'm star-struck watching a "Professional Genius" in action....

Thanks. Signed autograph is $30 if you are interested.

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Originally Posted by Looneybomber View Post

Well technology is always going to extend our sound reproduction capabilities. You make it sound that we must be able to reproduce 3hz with 100db of output. That is rediculous to me knowing just how much that will cost. You make it sound like a person with a $500 budget may as well forget the subwoofer because it wont be flat to below what an elephant can hear.

I don't even look at this as a matter of budget. If the goal is to be able to better recreate bass in music that you will actually be able to differentiate, then digging into single digits wouldn't seem to add anything - lowering distortion and increaisng headroom in the more audible ranges is a better goal. Again, I have proposed an experiment that can prove/disprove this. If the goal is to achieve extra rumble 5% of the time from certian types of movies after all headroom and distortion concerns have been met, then by all means, have at it. The furthering of the notion that extension to 3hz adds to the musical experience - without any facts, proof, or logic - is viewed as eccentric and perhaps even wasteful.

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Originally Posted by augerpro View Post

versus a 300L @ 13Hz box with 6" port

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OTOH even with a 6" inch port the first resonance is showing up at around 170Hz

Which is why a LLT requirement is for the first port resonance to be no lower than 190hz, preferably much higher in fact. People have built ports as long as 36" for a ~188hz first resonance with no offensive audible effect, though I personally would tend to error on the side of caution.

Quote:
Originally Posted by bosso View Post

To correct you, 30Hz+ is better achieved and cheaper in a sealed sub, for many reasons.

Umm, not really. If one is only interested in 30hz+, they could just build a ported sub optimized for a ~25hz tune.

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Originally Posted by Stealthdude View Post

Just look at JL Audio and Dynaudio for example... Commercial offerings and companies who have the R&D to make any type of speaker or sub they choose to make.

Both of their top shelf sub alignments are sealed.... there has to be a reason for it.

Yeah, there definitely is a reason for it. Because a top shelf ported alignment would be similar in size to the LLT subs you see many people building nowadays. The logistics of designing a manufacturing operation and handling the shipping for such large subs would be a nightmare for all but the most dedicated. I'm really quite surprised Epic went as large as they did with the Conquest, yet it still falls a little short in my eyes in regards to proper porting and achieveing the best balance of performance with the selected tune. It's much easier for a manufacturer to dump a bunch of money into a smaller sealed design.

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Originally Posted by Mark Seaton View Post

Of course now I'm going to have to listen to Steve go on about how big boxes are the only way to go. Of course the largest, most efficient box is still a waste if it's in a very inefficient location to drive the room.

Absolutely. And the story you went on to tell about using a small sealed subwoofer to test for the best position in room of a large ported subwoofer is something I have suggested to many LLT owners while in the planning stages. If you are going to go DIY, you may as well tailor it to perform the best it can in your listening environment.

Quote:
Originally Posted by cluelessngr View Post

what happens when after hitting a substantially loud low bass note resulting in a displacement of air out of the enclosure via the port, logic would have it that for a brief period of time the enclosure is in a negative pressure situation

Remember that the driver is still moving - the moving mass of air is only sucked back into the port when the driver is told to move again in the opposite direction. The driver is the dog that wags the movement of air in the port, not the other way around, as the driver is receiving the signal from the amplifier and initiates all the action. The air in the port is just a slave.

Quote:


Add to this that if the driver it asked to produce another large burst of sound before the enclosure/port has replaced the air from the first burst we have a situation in which we have the port both exhaling and inhaling introducing resistance to the second burst at the same time. It would seem to me that this effect, along with any noise that occurs from the re-stabilization of air volume has to add a level of distortion not found in the sealed design (which it appears has other distortion issues not so prevalent in the ported design).

Again, the moving mass of air in the port responds to the motion of the driver. Assuming an at least somewhat well thought out design with no EQ around tuning, this scenario can not and will not take place.

Keep in mind that the port involvement is minimal a couple octaves above tuning and gradually becomes more pronounced as you approach tuning. Also, remember that the frequency being reproduced means that the driver is moving in that many cycles per second, so this whole scenario of action/reaction between the driver and port is happening extremely quickly, even with infrasonic tuning.

The only way in which this act can result in added distortion (as compared to say sealed trying to reproduce the same frequency) is if the port is undersized or underflared for the application, resulting in turbulent air flow and "chuffing", or a swooshing sound. A competent design uses large diameter ports and flaring to avoid this, and thus, the benefits of porting (when combined with a low tune) are achieved with minimal to no negativelu audible side effects. Since the driver moves so little at tuning, distortion is actually improved dramatically.

Good question.

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Originally Posted by Jack View Post

I'm thinking the compression of the air in the box by the port has to be fairly considerable at high SPL if it's actually what's damping the motion of the driver. Is that the case, or am I thinking about it the wrong way (again)?

Think of the amount of air being displaced to recreate a 20hz sine wave at 120db from 1 meter ground plane, ignoring the driver, alignment, and enclosure. It's a significant amount of displacement. Now imagine we are displacing that amount of air with a single 18" driver using ~60mm of total travel continuously. Now place that 18" driver moving back and forth a total of 60mm inside a small, sealed enclosure. The amount of air being displaced by the driver forces the small volume or air inside the enclosure to compress. This results in a very high pressure.

Now place that 18" driver in a humongous sealed enlcosure. You're still displacing the same amount of air, but since there is far greater volume for that force to be diffused upon internally, the increase in pressure is nowhere near the same. When you add a port and approach tuning, you're simply trading movement of the driver for movement of the port, so the internal pressure created is the same, and it is still far less than a small sealed enclosure.

Quote:
Originally Posted by dae3dae3 View Post

IMO the whole ported vs sealed basically comes down to budget. People that have more money than god will throw a ton of money at the solution and end up with a high number of sealed subs. (SteveC will then jump in and tell them they could have had more performance if they had ported the subs.)

Correct. It's not about the size of the budget, it's about the amount of performance you want at any budget. Performance-orientated, ported wins. Size-orientated, sealed wins.

Quote:
Originally Posted by Stealthdude View Post

I would be dissapointed with JL and Dynaudio is the only reason they made a sealed sub was to keep the size down.

Prepare to be disappointed Surely they didn't have low distortion, FR linearity, and headroom as top priorities for their budget when they decided to build a small, sealed enclosure. Ultimately, in the end, they may have built subs that achieve great performance in those areas generally speaking compared to other subs, but, it cost them a lot more to get there than it would have to have gone ported and achieved better results.
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post #554 of 682 Old 03-28-2008, 10:15 PM
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Steve,

The EBS(LLT) has its place in HT use,and is a great choice in many systems where the owner has space in the room or hidden behind a screen.


Stealthdude,

Do not compare the sealed Dynaudio to the JL Audio subs,not even close. The Dyanudio gets stomped in extension,output and does in NO way best vthe sound quality of the f113.

I love Dyanudio Contour and Confidence series speakers,as I own Dynaudio speakers for over 12 years now. But the subs they offer are nothing special. JL Audio is on another level.

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #555 of 682 Old 03-28-2008, 11:22 PM
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however, to give it the type of priority you do, at the cost of higher frequency performance (which whether you want to admit it or not, will happen, even with quad 15" sealed drivers), when it is rarely if ever observed in music, and is more of a novelty in movies, comes off as an exercise in futility.

4X15" with 6K watts will be compromised from 30Hz to crossover exactly how?

Check the attached graph and try...try to pay attention. I have the ability to select extension by the flip of a switch (I did not run a 6dB L/T sweep in that graph, but it's an option), also selecting system Q by another flip of a switch (3 choices of Q are available. .7 is selected for both sweeps shown).

I know this is an alien concept for you, because it's not possible with a ported sub, except by implementing a series of selectable multiple HP filters of differing orders and knees, which is not a good plan.

Now, here's the part that seems to escape you: Regardless of which anechoic F3 and/or system Q I select, the 'performance' from 30Hz to crossover is UNCHANGED. With 4X15" and 6KW, 30-80Hz 'performance' would easily top Ilkka's list in every category he measures for.

Now, you seem to be claiming that although virtually no source contains single digits, having response to single digits somehow compromises 'performance' from 30-80Hz. Yet, if your single driver ported sub is tuned to 12Hz, that is perfectly fine and somehow its performance will be better in that range, whether I admit it or not.

And please don't bring up the IMD subject again. I addressed that 6 years ago and many times since. According to your claims your own assertion regarding IMD is a dog chasing its tail. If there is no content, how will IMD be effected at all, but if there is an IMD problem, there must be content to cause the problem.

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post #556 of 682 Old 03-29-2008, 04:51 AM
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Quote:
Originally Posted by cluelessngr
what happens when after hitting a substantially loud low bass note resulting in a displacement of air out of the enclosure via the port, logic would have it that for a brief period of time the enclosure is in a negative pressure situation

Remember that the driver is still moving - the moving mass of air is only sucked back into the port when the driver is told to move again in the opposite direction. The driver is the dog that wags the movement of air in the port, not the other way around, as the driver is receiving the signal from the amplifier and initiates all the action. The air in the port is just a slave.

Nobody is disputing the fact that the air movement is a direct result of the driver displacement. I don't think you understand what I mean. Its a cause/effect relationship of course. The driver has a length of excursion in either a positive (forward) or negative (backwards) position. A driver that has an 18 inch diameter and as it moves towards its negative excursion limit will displace x amount of air within the enclosure in a ported system. To assume this movement of air is instantaneous with the backward movement of the driver is mathmatically impossible, there will be a small, however measurable delay from when the driver cone reaches its farthest point of negative travel until the air pressure within the ported enclosure stabilizes. This is quite simply fact. Now this air movement does not occur within a sealed system, instead we are either compressing this body of air or contracting it. Furtermore when air moves it produces oise(*see wind).Now while it has been discussed that the compression/extraction introduces a level of distortion to the sealed design two things need to be considered.

1) While air pressure variations within a sealed enclosure will always be greater than a ported system, the ported system will still have pressue fluctuations. Thus, whatever distortion that occurs in a sealed system as a result of the compression of this air and its effect on the driver cone will also happen in a ported system, albeit in a much smaller amount. And in either case a larger the enclosure will minimize this effect.

2) The ported system has introduced a second variable to the equation, one that is not found in the sealed system, and that is the noise (be it however small) of bi-irectional air travel in/out of the enclosure thru the port and its subsequent impact on the perceived sound quality. I think it is this second property that (speaking in general terms) that fuzzies up the sound wave a bit resulting in that "Muddy" impression many get with ported subwoofers. Granted proper design can always reduce these levels to near neglible or perhaps even neglible levels, it can never be totally eliminated. Then in the case of many smaller ported subwoofer designs (which are very prevalent in the commercial arena), this second factor is very prevalent.
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post #557 of 682 Old 03-29-2008, 06:00 AM
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Again, the moving mass of air in the port responds to the motion of the driver. There can never be a situation in which the driver is moving back into the enclosure without the moving mass of air first finding its way back into the port - the scenario you describe is physically impossible. But it's a good question in that you are actually thinking about how a ported system works.

Actually the scenario you describe is physically impossible. As I already discussed in the above post the stabilization of air within the enclosure cannot be instantaneous as you suggest. It will have a measurable lag (albeit small). Now if you are suggesting that the driver has to wait for this stabilization to occur before moving in the opposite direction I can assure you that if this were to happen as you describe the resulting sound quality would be quite unplesant. Try this simple experiment, take a tupperware container, totally seal it with the exception of one corner. Now push down on the top, air is forced out of the tupperware, is it instantaneous? Nope. Did you hear the air escape? Yup. Now release your finger from the top and let the lid return to neutral. What happens? Air come back in. And you can plainly visualize that this is not an instantaneous event. Now I will grant you that this is an extreme case, but there is no denying the same factors exist and will be measureable within a ported enclosure. As to there significance is for others to argue, but trust me they do exist.

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remember that the frequency being reproduced means that the driver is moving in that many cycles per second

Yes it hyperventilating I agree. however, moving air makes noise regarless of direction. Furthermore you are merely confirming what I have already said, as this moement of air across the port is changing direction many times a second, and as I have shown that there will be a "lag" in this air movement as it correlates to the driver movement. This will either result in one of the two following things (but in all likelhood a combintion of both) occuring. Increased temporary pressure within the ported enclosure or simultaneous bi-directional air travel through the port. What I am guessing that is happening is that you have air flow in one direction along the inner diameter near the surface of the port in one direction and air traveling in the opposite direction in the middle of the port. Much like a rock in a stream, this resistance is impacting the sound wave.
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The only way in which this act can result in added distortion (as compared to say sealed trying to reproduce the same frequency) is if the port is undersized or underflared for the application, resulting in turbulent air flow and "chuffing", or a swooshing sound.

The fact that your chuffing occurs further proves my point. While I agree that this chuffing is an extreme case it ony proves the point that the port is adding some distortion to the sound quality for the fact that this "chuffing" can be greatly reduced to mere fractions or fractions of fractions it will never be eliminated completely.

Quote:


A competent design uses large diameter ports and flaring to avoid this, and thus, the benefits of porting (when combined with a low tune) are achieved with minimal to no negativelu audible side effects. Since the driver moves so little at tuning, distortion is actually improved dramatically.

I am not argueing the point of sealed over ported just pointing out that there are other factors to consider that I have not yet seen addressed in the ported design vs sealed controversy. At least here you say a ported design adds minimal to neglible distortion as a direct result of the port itself, and I am not either agreeing or disagreeing with that fact, but merely pointing out a few factors that have to be occuring as a result of the port itself. As to there significance I am not sure, but looking at it logically one can see how these things I bring into question might "fuzzy up" the sound wave leading to that "Muddy bass" perception. Furthermore, one would only use a large port when one is using a large enclosure. The large enclosure in and of itself must be given a good deal of credit for reduced distortion. I beleive when you go this route it is a compromise between the sealed/IB systems. An 18 driver will produce a great deal more pressure within a 1 cubit foot enclosure than it would within a 100 cubic foot enclosure, even though it is displacing or compressing the same volume of air.
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post #558 of 682 Old 03-29-2008, 06:02 AM
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Clueless,
What you're saying about differing pressures, air speeds, and delays, would also be effected by enclosure volume...What I'm imagining is a smaller box will pressurize quicker, thus forcing air out of the port with less delay correct? Granted, I'm talking milliseconds, but the difference should be there.

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post #559 of 682 Old 03-29-2008, 08:28 AM
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Originally Posted by bosso View Post

Now, here's the part that seems to escape you: Regardless of which anechoic F3 and/or system Q I select, the 'performance' from 30Hz to crossover is UNCHANGED.

So let's say you are listening to some of this single digit extension music you have so much of. In the first scenario, you leave all four of your drivers with their natural respose, no LT applied. In the second instance, you apply a 24db/octave LT. In this music, you have both higher frequency bass as well as your single digit bass, playing together at the same time. With no LT, the response is naturally down so much in the single digits because the air insde the enclosure is allowed to resist cone movement. The single digits in the music come and go, and we will call the amount of nonlinear distortion created at those frequencies by this "natural" configuration the standard. Now we replay the song with the 24db/octave LT in play. When those single digits come into play, the amp is being told to deliver significantly more power, 256 times more power per octave if I did my math correctly. This results in greater excursion, greater heat in the voice coil, and greater air spring distortion (had to throw that in). This adds up to a significant increase in distortion being created over the standard amount from scenario 1. At the same time though, the driver is also being asked to reproduce higher bass frequences. What I am saying is that there is no way the driver can be reproducing those higher frequencies as cleanly in scenario 2 as it can in scenario 1 when there is also single digit information in play.

Quote:
Originally Posted by cluelessmgr View Post

To assume this movement of air is instantaneous with the backward movement of the driver is mathmatically impossible, there will be a small, however measurable delay from when the driver cone reaches its farthest point of negative travel until the air pressure within the ported enclosure stabilizes.

When the air pressure stabilizes, that means the air mass has moved out of the port, and yes, there is a delay for that action to take place known as group delay.


Quote:


I think it is this second property that (speaking in general terms) that fuzzies up the sound wave a bit resulting in that "Muddy" impression many get with ported subwoofers. Granted proper design can always reduce these levels to near neglible or perhaps even neglible levels, it can never be totally eliminated.

That is potentially one reason, but there are others as well. Lots of compromises need to be made when one looks to mass market a subwoofer, and they can't always do what is ideal. Check my LLT Explained thread for more of these reasons. When these levels become negligible - which is accomplished with adequate port area and an infrasonic tuning - what you are left with is greater displacement and less distortion, a double win.

Quote:


Actually the scenario you describe is physically impossible. As I already discussed in the above post the stabilization of air within the enclosure cannot be instantaneous as you suggest. It will have a measurable lag (albeit small). Now if you are suggesting that the driver has to wait for this stabilization to occur before moving in the opposite direction I can assure you that if this were to happen as you describe the resulting sound quality would be quite unplesant

No, it's not impossible, it's the norm, and it has been measured. What I said was that before the driver moves from one cycle of 'negative' excursion (as you call it) to the next cycle of 'negative' excursion', the air mass will have already found itself back inside the port, as the driver had to move to nuetral (sucking the air mass back in), then to positive (sucking external air in), then back to nuetral (pushing external air out), and finally back to negative (pushing internal air out). If that mass of air never found its way back in the port from the first negative stroke by the time it made it around to the next negative stroke, you could measure this as a group delay greater than one cycle at tuning.

Some commercial subs which are applying EQ at, around, and even before tuning may go on to achieve this feat as can be seen from Ilkka's measurements of certain SVS subwoofers - there is extremely high distortion that follows. Therefore, I will ammend my earlier comment with the preface of no EQ at or around tuning and using an at least somewhat well thought out design. But when we look at a design like the TC2k ported, with no EQ and no steep highpass filter, the group delay at tuning is far less than one cycle. To really dig into the detail, Ilkka has even been kind enough to measure a commercial ported subwoofer - again, SVS - using its own amplifier (with all the built in EQ, limiters, highpass, etc.), and then again with that amplifier bypassed, using a pro amp hard wired to the driver upon my request. Sure enough, there was a considerable decrease in group delay when bypassing the built-in amp with all its "foolproof" protection. That is another type of compromise that a commercial subwoofer manufacturer needs to implement unfortunately, and yet thre are still more as well.

But to address a point you bring up later, yes, with Ilkka's help in conducting detailed measurements, a core group of enthusiasts on this forum have been looking into all of these minute details over the course of the last 3 years. Ilkka, noak katz, Mark Seaton, and even bosso probably recall many of these debates we have had. Unfortunately this forum is much worse off without the addition of Ilkka, as nobody else here is willing or able to provide the kind of measurements and data he could. Luckily though, he is still an active member at other, ahem (better?), forums.


Quote:


I am not argueing the point of sealed over ported just pointing out that there are other factors to consider that I have not yet seen addressed in the ported design vs sealed controversy. At least here you say a ported design adds minimal to neglible distortion as a direct result of the port itself, and I am not either agreeing or disagreeing with that fact, but merely pointing out a few factors that have to be occuring as a result of the port itself. As to there significance I am not sure, but looking at it logically one can see how these things I bring into question might "fuzzy up" the sound wave leading to that "Muddy bass" perception. Furthermore, one would only use a large port when one is using a large enclosure. The large enclosure in and of itself must be given a good deal of credit for reduced distortion. I beleive when you go this route it is a compromise between the sealed/IB systems. An 18 driver will produce a great deal more pressure within a 1 cubit foot enclosure than it would within a 100 cubic foot enclosure, even though it is displacing or compressing the same volume of air.

LLT Explained. I think you will find that it has all been addressed.
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post #560 of 682 Old 03-29-2008, 12:01 PM
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So let's say you are listening to some of this single digit extension music you have so much of. In the first scenario, you leave all four of your drivers with their natural respose, no LT applied. In the second instance, you apply a 24db/octave LT. In this music, you have both higher frequency bass as well as your single digit bass, playing together at the same time. With no LT, the response is naturally down so much in the single digits because the air insde the enclosure is allowed to resist cone movement. The single digits in the music come and go, and we will call the amount of nonlinear distortion created at those frequencies by this "natural" configuration the standard. Now we replay the song with the 24db/octave LT in play. When those single digits come into play, the amp is being told to deliver significantly more power, 256 times more power per octave if I did my math correctly.

3db(2), 6db(4), 12dB(8), 24dB(16) 16 times the power. Since the input signal boost is precisely tailored to the natural roll off, that 16X boost is also gradual, not reaching the full 16X until the new F3. In most cases of a .7 sealed alignment that point is around 10Hz.

If your system is 90dB @ 1W/1M, you have capability to 115dB from 35Hz and up with 300 watts. 16 times is 4,800 watts. This is an oversimplification and does not take into consideration boundary gain, but it's easy enough to do some math when looking at the GP numbers of the sealed L/T LMS-5400-18" sub.

The mistake you (and nearly everyone else) keep making is that you believe that the playback of the single digit content of the recording of a real event such as a kick drum strike must be boosted to some ridiculously high level to be appreciated.

The high end recording and consumer electronics industries have struggled with only one thing since inception. Is it real, or is it Memorex? Huge advancements have been made over the past 1/2 century in eliminating noise like 'rumble' and in increasing the dynamic range capabilities.

Accurate reproduction of transients have been a focus. 25 years ago I read a paper by Carver who began the paper by recalling a meeting with a well known acoustician of the day in his lab. He had a stack of amplifiers totaling 10KW and was snipping a piece of paper with scissors and observing the results on an oscilloscope. He said to Carver, "Can you believe this? 10,000 watts and this transient event still shows some distortion!"

Today, we have the ability to reproduce that transient all the way down to zero, non-linear distortions notwithstanding.

Quote:


This results in greater excursion, greater heat in the voice coil, and greater air spring distortion (had to throw that in). This adds up to a significant increase in distortion being created over the standard amount from scenario 1. At the same time though, the driver is also being asked to reproduce higher bass frequences. What I am saying is that there is no way the driver can be reproducing those higher frequencies as cleanly in scenario 2 as it can in scenario 1 when there is also single digit information in play.

This scenario is highly source dependent. In the case of the lightning strikes in chapter 4 of WOTW (see attached spectrogram), the first strikes have most energy concentrated in the 40-50Hz range for the majority of listeners. Only the last 3 strikes have high level 4-10Hz content, showing -15-20dBFS on the first two of them, the last one being attenuated even further.

The proper way to have accomplished this effect in harmony with the format, as it was intended, would be to place all of that single digit content in the discrete LFE channel, where it could be played back through a discrete LFE subwoofer. The rest of the spectrum of the effect would be reproduced by full range capable mains, or a discrete redirected bass subwoofer.

Since Dolby has held to their position of backward compatibility to the old pro logic system, in which the .1 channel is not discrete, but is instead a matrixed channel, too many DVDs have LFE content in the front channels, by Dolby's recommendation. THAT is what 'muddies' the waters.

One would hope that any engineer who is purposely placing high level low freqs on a soundtrack would be smart enough to realize that placing that content in the mains for the sole purpose of backward compatibility with a system that has zero chance of playing back at all, and place all of it in the LFE channel.

All of that aside, and dealing with reality, yes (even though you have traditionally rejected this argument and now you embrace it as a point of disadvantage for single digit extension) there is an increase of IMD whenever 2 inharmonic tones are reproduced at the same time by the same transducer. Some contend that this is not an issue a VLF, but I still believe there is the potential for it.

This will typically only occur when synthesized effects are encoded in conjunction with music or other tones that are not harmonics of each other. This is less of a concern when reproducing a music transient. What makes you able to tell a piano from a cello, even though the 2 instruments are plucking the same fundamental tone, is the unique combinations of harmonics each of the 2 instruments generate when playing the same note.

The question really is whether or not the full spectrum playback is perceived as closer to the real event vs a truncated spectrum. WOTW is an extreme example. I don't know if the effect is synthesized from a real lightning strike and I suspect that it is an amalgam of synthesized versions of real events, based on what I've learned about the generation of effects like the chopper blades in BHD and other soundtrack effects. But it's simple: do you have more accurate playback, with single digits, non linear distortions included, or with the effect erased altogether?

You have to listen, A/B, to answer that question, but common sense should be at play.

I'll just say that so far you haven't ever complained about IMD from 10Hz to crossover, or from 40-160Hz in your mains. If you had, would you think the answer would be to eliminate those frequencies?

My opinion is that extension equals an enhanced perception of realism, every time. Improving headroom, lowering non linear distortions, better understanding of and improving the process, increasing the number of and variety of source, etc, are all important pieces of the puzzle. And, make no mistake, they will march onward, but, they are separate discussions to the basic debate.

Bosso
LL
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post #561 of 682 Old 03-29-2008, 12:21 PM
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Steve

Perhaps you dont understand what I disagree with to clarify it is this:


Quote:


There can never be a situation in which the driver is moving back into the enclosure without the moving mass of air first finding its way back into the port

I am saying yes there can and yes there is.

Quote:


What I said was that before the driver moves from one cycle of 'negative' excursion (as you call it) to the next cycle of 'negative' excursion', the air mass will have already found itself back inside the port,

To this I agree with the added exception of the fact that the air mass will have arrived at a small but measurable amount of time after the cone. But lets look instead of the full cycle of cone excursion from negative to positive then back to negative to just the time frame from when the cone travels to negative then to positive.When the cone travels inward it expells air from the enclosure outside thru the port. When the cone reaches its furthest part of negative excursion the air has not yet caught up. Now during this time frame (as the air stabiizes) the cone begins its forward travel which has the opposite effect and wants to draw air in and not expell it. Unfortuatly, due to the small lag between the cone movement and the air movement we already have air traveling in the opposite direction. We are now asking that air (which does have mass) to reverse direction and travel the opposite direction. So now we have introducd a level of port turbulence as well as added another level of resistance (much like the resistance in the sealed design) for a brief period of time. But in the sealed design this resistance is linear while in the ported design it is non-linear and subject to variations based on whatever material is being played.

Quote:


LLT Explained. I think you will find that it has all been addressed.

Yes I have read parts of this good read.

I would like to summize that as the enclosure size of ported and sealed systems grow, the difference between the two designs do not become as pronounced. I am still admittably confused by the meaning of the infinite baffle design as it appears to have been misnamed. To this end I would like to ask at what point does a large box become infinite? It as always been my understanding that the only area that could be designed as infinite would be (outer) space. Therefore, the only way to have an "infinite" baffle system would be to have the speaker out of the earth's atmospere. However, as space is a vacuum and sound does not travel thru a vaccuum, I fail to see how this would be desirable .
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Correct me if I'm wrong but the driver does not push the air out of the port at the same time its cone is moving negatively, except under the tuning point. It seems to me that when the cone is moving positively the air in the port is actually travelling out (positively also) and vice versa. Otherwise we wouldn't get any sound-which we don't when the opposite happens under tuning- cones goes out, but port air goes in. Out of phase. At and above tuning the port acts as another driver moving in phase with the real driver. This isn't a simple push pull system, it's a resonator.

You guys are over thinking this a bit.
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post #563 of 682 Old 03-29-2008, 12:40 PM
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Quote:
Originally Posted by cluelessngr View Post

I am still admittably confused by the meaning of the infinite baffle design as it appears to have been misnamed. To this end I would like to ask at what point does a large box become infinite? It as always been my understanding that the only area that could be designed as infinite would be (outer) space. Therefore, the only way to have an "infinite" baffle system would be to have the speaker out of the earth's atmospere. However, as space is a vacuum and sound does not travel thru a vaccuum, I fail to see how this would be desirable .

Are you for real? Have you bothered to read anything on IB? It just means that the baffle is relatively large compared to the wavelengths involved. Although your universe comparison is more apt than you realize. The universe (baffle) is not infinite- but to us little hairless apes (the wavelength) who have no way or hope of traversing its distance, it might as well be (IB).
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post #564 of 682 Old 03-29-2008, 12:54 PM
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After reading this thread for a couple of months I have learned much about subs (I think). I was drawn to DIY primarily for the performance per $ value. Then I remembered the pile of 4 x 2s stacked in the shop meant for another workbench that has remained motionless since around the turn of the century. It's True! My friends were right. I have PCD, Project Completion Disorder. No more projects till the others are finished.
This thread will end the same as the Chevy vs Ford, 30'06 vs 308, and Mary Ann or Ginger debates.
For the IB guys... should a person put cross bracing between the floor joists (if none existing) before "cranking it"?
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post #565 of 682 Old 03-29-2008, 01:54 PM
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bosso, I'd actually like to stop and thank you for making a post devoid of any insults. If the tone is kept as civil as that last post, perhaps we can reach some type of common ground or even agreement.

Quote:
Originally Posted by bosso View Post

The mistake you (and nearly everyone else) keep making is that you believe that the playback of the single digit content of the recording of a real event such as a kick drum strike must be boosted to some ridiculously high level to be appreciated.

This has been tested in the past and can easily be tested now. Since few - if any - of us have subwoofers capable (relatively flat FR, adequate headroom, low distortion) into the low single digits, we make the experiment focus on the 10-20hz range, where many more of us DIYers can participate. Since sensitivity decreases with frequency, can we not conclude that if information in the 10-20hz range at attenuated output levels as compared to a fundamental in higher bass frequencies is not perceivable, that it surely could not be in the 1-9hz range? Where is the flaw in that hypothesis?

Quote:


All of that aside, and dealing with reality, yes (even though you have traditionally rejected this argument and now you embrace it as a point of disadvantage for single digit extension) there is an increase of IMD whenever 2 inharmonic tones are reproduced at the same time by the same transducer. Some contend that this is not an issue a VLF, but I still believe there is the potential for it.

Again, please don't get me wrong, I'm in no way saying single digit extension is a bad thing. Believe it or not, I'd actually love to find out that solid extension into the single digits - when accompanied with a relatively flat FR, adequate headroom, and low distortion - does add something signifcant to the perceivable experience. Why? Because then I would know there is more out there - it would easily justify me spending time on designing and building something new that will increase performance. But as I said, first, we would need to have something to suggest that it is a worthwhile cause, and second, that range would need to be able to be reproduced effectively. In my current job, I have access to almost anything and everything one would need to build a type of transducer purpose-built to focus on moving large amounts of air, focusing on <20hz or so. Disregard the concept of multiple 15" or 18" electromagnetic cone drivers (sorry EAR ), it's too inefficient and just not suited for such a purpose, we can do so much better than that. That frequency range still requires fast oscillations, but if we don't have to worry about going any higher, we open ourselves up to a broader range of possibilities than electromagnets/voice coils, and maintaining a linear motor system becomes much, much easier.

As for IMD, Ilkka's measurements have shown that when a system maintains low harmonic distortion over a given frequency range, it also maintains low IMD when multiple frequencies in that same range are played simultaneously as compared to other subs. It's not a perfect correlation, but there is definitely a trend. What this means is that one would need a system capable of low distortion into the low single digits or else they will definitely will be degrading the audible performance of higher frequency playback if the media in question calls for reproduction of frequencies in both ranges. Therefore, when I see harmonic distortion graphs of small sealed subs start to skyrocket below 35hz, it tells me right away that that type of a system is not suitable for single digit reproduction, as we need something that maintains low distortion deeper. With a large and low tuned ported, we can maintain low distortion, relatively flat FR, and more headroom to somewhere below tuning, and then, with no EQ in play, allow electronics rolloff and a natural tendency to phase out to essentially just let things die off somewhere below tuning. What we are left with is a system that does great things in a targeted FR range. 10-80hz covers a lot of ground. Is it better to be great from only 10-80hz or great from 35-80hz and then progresisvely worse below 35hz with a constant rolloff? Based on the way our ears work, I think all evidence points to the first option.

Quote:


The question really is whether or not the full spectrum playback is perceived as closer to the real event vs a truncated spectrum.

Quote:


But it's simple: do you have more accurate playback, with single digits, non linear distortions included, or with the effect erased altogether?

Right. Again though, we can test this. Just raise the range in question from 1-9hz to 10-20hz, and more people can participate.

Quote:


I'll just say that so far you haven't ever complained about IMD from 10Hz to crossover, or from 40-160Hz in your mains. If you had, would you think the answer would be to eliminate those frequencies?

But most LLTs will have low harmonic distortion from 10hz to crossover at what most would consider adequate listening levels. And while my mains are far from the beefiest, with dual 7" drivers that are crossed over at 400hz, ported and tuned to ~30hz, and use a 4th order highpass at 60hz, they shouldn't fair all that bad at what I consider adequate listening levels. If one were to use a simple 2-way design with a 5" woofer though, then yeah, I can see your point, no room to talk.
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post #566 of 682 Old 03-29-2008, 02:16 PM
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Quote:
Originally Posted by cluelessmgr View Post

When the cone travels inward it expells air from the enclosure outside thru the port. When the cone reaches its furthest part of negative excursion the air has not yet caught up. Now during this time frame (as the air stabiizes) the cone begins its forward travel which has the opposite effect and wants to draw air in and not expell it. Unfortuatly, due to the small lag between the cone movement and the air movement we already have air traveling in the opposite direction. We are now asking that air (which does have mass) to reverse direction and travel the opposite direction. So now we have introducd a level of port turbulence as well as added another level of resistance (much like the resistance in the sealed design) for a brief period of time. But in the sealed design this resistance is linear while in the ported design it is non-linear and subject to variations based on whatever material is being played.

Again, this lag time you speak of is measurable and has typically been one of the many performance aspects measured in subs. Port utilization is at its highest at tuning, and while Ilkka's measurements show a low group delay at tuning with the TC2k to begin with, an infrasonic tuning would prevent even a high group delay from being perceivable. So it's a one two punch - first minimize it with no EQ or highpass filter, then lower it to a range where it wouldn't have been audible to begin with. It's in LLT Explained along with a few accompanying measurments showing this concept at work. I don't see how this group delay creates any "added resistance" however - added in relation to what exactly? As for resistance being linear in sealed, I think it has been mentioned a few times now that above some percentage of compression, it no longer stays linear. I actually think the strength of the cone comes into question at that point too, in a small sealed enclosure where the internal volume is being highly compressed that is. And we haven't even mentioned temperature yet....

Quote:


I would like to summize that as the enclosure size of ported and sealed systems grow, the difference between the two designs do not become as pronounced.

Correct. There is still a significant difference in FR linearity, distortion, and headroom between a large ported and large sealed in favor of the ported, but yes, it's slightly reduced as when compared to a small sealed.
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post #567 of 682 Old 03-29-2008, 04:09 PM
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Originally Posted by bossobass View Post

3db(2), 6db(4), 12dB(8), 24dB(16) 16 times the power.

You may want to check your math.
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Originally Posted by geoffstgermaine View Post

You may want to check your math.

Yep I think that should read:

3db(2), 6db(4), 9dB(8), 12dB(16) 16 times the power.
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post #569 of 682 Old 03-29-2008, 04:45 PM - Thread Starter
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lol, new people posting.....same arguements over and over and over.....

I guess I will post about the dead horse again


The tribal wisdom of the Dakota Indians, passed on from generation to generation, says that, "When you discover that you are riding a dead horse, the best strategy is to dismount."

However, in government, education, and in corporate America, more advanced strategies are often employed, such as:

1. Buying a stronger whip.
2. Changing riders.
3. Appointing a committee to study the horse.
4. Arranging to visit other countries to see how other cultures ride dead horses.
5. Lowering the standards so that dead horses can be included.
6. Reclassifying the dead horse as living-impaired.
7. Hiring outside contractors to ride the dead horse.
8. Harnessing several dead horses together to increase speed.
9. Providing additional funding and/or training to increase dead horse's performance.
10. Doing a productivity study to see if lighter riders would improve the dead horse's performance.
11. Declaring that as the dead horse does not have to be fed, it is less costly, carries lower overhead and therefore contributes substantially more to the bottom line of the economy than do some other horses
12. Rewriting the expected performance requirements for all horses.


It is not "open-minded" to reject knowledge - Bob Lee
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post #570 of 682 Old 03-29-2008, 05:06 PM
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I don't see how this group delay creates any "added resistance" however - added in relation to what exactly?

The group delay causes a set of circumstances in such that in anyone instance in time the direction of the air flow thru the cone could be contradictory to the direction of cone travel. I emphasize could, as it will be determined by the source material being played. In a perfect world air would come in thru the port, stabilize, then be asked to leave the enclosure. In the real world air that is coming in thru the port is asked to reverse direction and leave the port before this stabilization occurs. It does not always happen, but it happens which leaves a variable in the equation as for the pressure seen by the driver.

Quote:


Correct me if I'm wrong but the driver does not push the air out of the port at the same time its cone is moving negatively,

If, on a front firing sub-woofer you carefully push in the driver cone, air is expelled out the enclosure. Release it and air is drawn back in.

Quote:


Are you for real? Have you bothered to read anything on IB? It just means that the baffle is relatively large compared to the wavelengths involved. Although your universe comparison is more apt than you realize. The universe (baffle) is not infinite- but to us little hairless apes (the wavelength) who have no way or hope of traversing its distance, it might as well be (IB).

Nobody was critisizing IB, only that its a dumb name (IMHO). When does a very large enclosure stop being an enclosure and start being infinite?
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