late night thoughts about DIY vs Comercial - Page 22 - AVS Forum
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post #631 of 682 Old 03-31-2008, 09:47 AM
 
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Ok ... let us look at the 4 x 18 inch FI IB driver in a "sealed box" which was the necessary 25 x VAS needed to mimic the IB design.

We need 1300 cubic feet of interior volume. Assuming no bracing, and no net loss for the drivers, this is an interior enclosure of 14 x 12 x 8 feet for a 4 driver set up.

In other words, if we are willing to build a small room to house this "sealed subwoofer", it will match the IB.

The question is ... is there anyone crazy enough to build such a thing ?

This reminds me of the 200 MPG car and the Loch Ness Monster - it makes for great conversation, but no such animal exists.
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post #632 of 682 Old 03-31-2008, 09:47 AM
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Quote:
Originally Posted by Richard Mayer View Post

For the nth time, it's not about whether someone could or would build a 25x Vas box. It's not whether the box affects the performance or whether it exists mathematically. It's about the performance. And hopefully everyone agrees by now that an IB subwoofer performs just like a large sealed subwoofer. If not, I'm out of words.

Agreed Richard,

From an electro-acoustic standpoint, the operation of an IB & a sealed box are the same. In the system, the suspension compliance and the compliance of the air in the box are in parallel to form the net restoring force. The source of the spring/restoring force differs, as will losses in the system. Which one works better will depend on many factors, where obviously an IB is more dependent on the behavior of the suspension, and a relatively small sealed box with a very soft suspension is more limited by the excursion limits of the suspension and the linearity of the air spring, along with any possible issues with the box construction or function. The suspension has some degree of linearity with respect to excursion, where the air-spring has a degree of linearity with respect to internal pressure change, or SPL/volume/freq. Of course then there are many(most?) systems which fall inbetween these two extremes.

The rambling arguments are all stemming from a lack of clarity in what people are asserting. In the case of IB vs. sealed implementations, you have to first define what you mean as IB, as definitions are coloquial or inferred within communities. There are many ways IB & sealed are similar or the same, and there are of course plenty of important differences between them. While I've been hinting at it for over a year in such posts, I have yet to see anyone look at or discuss what is going on with the impedance curve of typical IB vs. many other common alignments.

The two are subsets of a common system with different benefits. Whether you find those benefits desirable is entirely dependent on the application.

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post #633 of 682 Old 03-31-2008, 09:52 AM
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Quote:
Originally Posted by craigsub View Post

Ok ... let us look at the 4 x 18 inch FI IB driver in a "sealed box" which was the necessary 25 x VAS needed to mimic the IB design.

We need 1300 cubic feet of interior volume. Assuming no bracing, and no net loss for the drivers, this is an interior enclosure of 14 x 12 x 8 feet for a 4 driver set up.

In other words, if we are willing to build a small room to house this "sealed subwoofer", it will match the IB.

The question is ... is there anyone crazy enough to build such a thing ?

This reminds me of the 200 MPG car and the Loch Ness Monster - it makes for great conversation, but no such animal exists.

Any car can do 200 MPG,just build a gently sloping road and I will prove it to you.

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 #634 of 682 Old 03-31-2008, 10:20 AM
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Quote:
Originally Posted by Mark Seaton View Post

I don't have time to jump in the discussion of the conceptual operation of a reflex system, but I wanted to nip this before we get to far.

Steve, please do some homework on the Harman white papers, particularly the ones prior to the multiple subwoofers paper. They tested and concluded, as have plenty of others, that at low frequencies the system of the subwoofer and room is largely minimum phase. Don't get too caught up in the definition of minimum phase, but rather what that means. That means that response changes have associated phase changes. There are conditions at lower frequencies, such as very sharp/narrow nulls, which are not minimum phase, but for the most part the in-room response of a subwoofer is. This means that carefully smoothing the response also improves the phase response and time domain behavior.

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Originally Posted by SteveCallas View Post

Mark, is it not correct that a flat phase response equates to a flat frequency response, but not necessarily the other way around? If there is a sharp null in room centered around 45hz and one applies 16db EQ boost centered at 45hz, the amount of excursion now used around 45hz is disproportionately high to the rest of the woofer's playback range at a given output level. Even though the FR may now be closer to flat, won't this now result in some transient response degredation at and around that frequency because the woofer will take longer to stop? I ask this as a question.

Steve,

No, the majority of loudspeakers are acoustically small devices at low frequencies, so the phase response will not really be "flat", but rather centered around a 90deg, broad band phase shift plus the effects of the high and low frequency roll off of the system in question. A horn in the vecinity of 25% efficiency or more, and full range drivers that are acoustically large for the wavelength produced are some of the rare situations where a the phase response can be "flat" or near constant group delay... although even then the bandwidth can be limited and there are other issues at hand.

What does happen with any common loudspeaker system with non-changing directivity is that any change in response comes with an associated and uniformly predictable change in phase response. Common filters such as those used for PEQ and HP/LP type filters follow the same behavior.

The important detail is that the affect of the listening room at low frequencies is also largely minimum phase, where boosting or attenuating frequency ranges at the listening position show mostly the same phase changes we would see if we matched this response outdoors with PEQ. As I noted in my post, severe notches will often be exceptions to this case. My TEF25 has a display/EQ mode that determines whether the response deviates minimum phase or not, and flashes a warning when you place your cursor on an area that is not minimum phase. Most swings in response tend to pretty well hold minimum phase behavior.

Since they hold this behavior, correcting their effects with other minimum phase filters will counteract the changes in phase from the room. This was tested and demonstrated in some of the Harman white papers. At higher frequencies discrete, late reflections become more of an issue, and these will most certainly not be minimum phase.

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post #635 of 682 Old 03-31-2008, 10:32 AM
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Mark,

OT so excuse me...

Since you are here,may I ask a question about your SubMersive ? As I am seriously interested in purchasing one.

I did send you PM's none have been returned,I guess you are quite busy.

How long is the wait time on a SubMersive these days?

Thank you

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 #636 of 682 Old 03-31-2008, 10:35 AM
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Quote:
Originally Posted by Mark Seaton View Post

I have yet to see anyone look at or discuss what is going on with the impedance curve of typical IB vs. many other common alignments.

Give me a little bit of time to get a measurement setup in place, and I'll run most of the tests people want.

I can't however post max SPL/distortion for my big IB, since it's positioned ~8' from a 60 sq ft picture window...

Any thoughts on Praxis vs something like Smith & Larson Woofer Tester Pro/Speaker Tester? Approx $1k is my threshold of pain for this investment

http://www.woofertester.com/wtproproduct.htm


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post #637 of 682 Old 03-31-2008, 11:21 AM
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so lets see if we can get back to the original thought process of this thread:

Can Commercial provide an alternative to DIY now, at these prices and new advancements on the commercial front?!

Not to get into another piss match of ported/sealed, or what is IB, etc, but I still believe that although some great improvements have been done over the past year or so, from the Epik line, to the MFW15, and eD, etc, dollar for dollar, DIY is still providing that extra notch of perfomance for the dollar..........but you are giving way to some of the finishing that these commercial offerings are giving now.

Just this weekend I had yet another colleague who wanted me to help them put their HT setup together....and when it came down to subwoofers, his budget was $1200. THus, my immediate reply was:
* 4 fi IB18's ($800), a EP2500 ($250), a FBD2496 ($99), and some wood
however, he coughed at the idea of wanting to cut holes in his ceiling, so we looked at other options:

* a pair of MFW15's, or Epik Castles

or

* pair of Maelstrom-X 18's, some wood or sonotubes, a pair of amps, and viola.

needless to say, the latter was the ending choice.


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post #638 of 682 Old 03-31-2008, 11:31 AM - Thread Starter
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DIY is still providing that extra notch of perfomance for the dollar..........but you are giving way to some of the finishing that these commercial offerings are giving now.


Right, that is my conclusion

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post #639 of 682 Old 03-31-2008, 11:38 AM
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Originally Posted by penngray View Post

Right, that is my conclusion

I agree but as for giving away finish..Shinobiwan will disagree,as his DIY is at least of equal finish quality as the finest commercial.

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 #640 of 682 Old 03-31-2008, 11:45 AM
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Originally Posted by TheEAR View Post

I agree but as for giving away finish..Shinobiwan will disagree,as his DIY is at least of equal finish quality as the finest commercial.

shinobi is THE standard for which DIYers are graded, so its not apples and oranges....very few, if any, can imitate the stunning work he does.

keep in mind as well that the amount of labor and materials he invested to get those finishes were pretty substantial..........as compared to, say, what the finish of a MFW15 is for $500. Just a thought.


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post #641 of 682 Old 03-31-2008, 12:12 PM - Thread Starter
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I agree but as for giving away finish..Shinobiwan will disagree,as his DIY is at least of equal finish quality as the finest commercial.

Great will Shinobiwan finish other people's DIY subs for free?

Its good to be back to the original debate......

Its hard to argue comercial vs DIY when the DIY crowd simply puts no limit DIY side.


Someone posted that they can build a DIY sub for $700 that blows the $700 comercial sub out of the water.

Well I guess if we ignore time and $$$ for the DIY project then its probably true BUT if we include some value for the time, some value for the tools needed then I suspect we can not even build a decent sub for under $700


DIY ported sub.....(15", 1000 watts).

Driver $150 - $350
Amp $300

hmmmm, we are already at $450 - $650.

Materials....screws, glue, wood, something to cut holes with.... $100

We are at $550 - $750.

A weekend of work just to build it .....even at minimum wage its around $100 value

Now its $650 - 850.

Now the finish....how much time would it take to have a comericial finish....8-16 hours of labor? so lets say $100. I dont even think 99% of the DIYers can get a comercial finish period let alone in 16 hours because they just dont have the tools needed.

How about EQing? DIY subs bottom out all the time or dont have flat response lines so filters are added - $100

In the end the DIY sub is much more then $700 and there are so many hidden costs to DIY are ignored.

Yes, we dont count our time as value but it is no matter what someone's opinion is. It has to have value when you are doing comparisons.

Its pointless to do comercial vs DIY comparisons unless we are fair to both sides.

If costs savings is the goal for someone to DIY then I would conclude that this year its better to buy comercial because you honestly do not save money at the lower end. Heck, that is my DIY goal, to get a higher performance/$$$, I dont care about subwoofer education over all, a year from now I wont care what SD or Qts means.

Although, I do believe an IB solution is one of the most cost effect, highest performance solution out there and if someone can do an IB they simply should!

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post #642 of 682 Old 03-31-2008, 12:54 PM
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Originally Posted by penngray View Post

In the end the DIY sub is much more then $700 and there are so many hidden costs to DIY are ignored.

The flaw with this argument is that if you asked Hsu or SVS to build one sub, then I expect it would cost a lot more than mass producing 100 or more subs. If the DIY'er were to produce subs at the quantity of some of the smaller sub manufacturers then that would be apples to apples or the manufacturer to build one sub as a DIY'er does. What would the manufacturer charge for one sub? Quite a bit more than a DIY'er.
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post #643 of 682 Old 03-31-2008, 12:58 PM
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Penngray, your cost analysis totally depends on the situation. If a person is starting out with no tools and has no real interest (from a hobby perspective) in doing the woodwork and finishing then I totally agree. To tell someone to go buy a shop full of tools and put other hobbies on hold to build a subwoofer and that they will definitely save money is a lie. If you take someone else who either has the tools or at least access to the tools (like several friends of mine using my tools for projects) and is interested in building to the point that they enjoy the work then I would disagree and say that are cost savings to be had even at lower cost levels.

The point is that each person would have to analyse each project on it's own. The only additional tools I've had to buy for building subs is a circle cutting jig, which turned out to be largely unnecessary as I wound up building my own to get larger radii, and a 3/4" roundover bit. If you want to divide the cost of all of my tools by all of my projects then there's probably 20 to 30 to divide it amongst, most of which are/were more involved than building a sub enclosure (guitars and other instruments, desks, furniture, etc).

If someone's only interest is cost savings then it can get difficult, but of course in higher cost projects the cost savings can become more obvious.

And chasw98 has a good point. As soon as someone wants something custom about a sub (to fit in a certain place, etc) then the options become DIY or a high cost custom solution.
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post #644 of 682 Old 03-31-2008, 01:15 PM
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Quote:
Originally Posted by chasw98 View Post

The flaw with this argument is that if you asked Hsu or SVS to build one sub, then I expect it would cost a lot more than mass producing 100 or more subs. If the DIY'er were to produce subs at the quantity of some of the smaller sub manufacturers then that would be apples to apples or the manufacturer to build one sub as a DIY'er does. What would the manufacturer charge for one sub? Quite a bit more than a DIY'er.

excellent point chuck....beat me to it.

also Penn, your example has certain conditions you have overlooked:

* the driver, which can cost $200-$300, for example, will certainly destroy something similar in a commercial sub. Take the maelstrom-x 18", with 33mm Xmax, XBL^2 motor, at $299......if executed properly, should be capable of destroying the likes of the PB13 or Tower/Castle, etc, in terms of output, extension, FR linearity, distortion, etc........ so, yes, big advantage to DIY.

* More than likely an EQ will be needed, but this applies to both boxes. The same room interactions affecting one, will affect the other. Those silly single band PEQ's are pretty useless in most rooms, so I don't really count those.

* Most Bash/plate amps are very underated in what they can do....I know, I used one in my DIY AV15. However, as good as they are for the buck, they won't be able to handle the load of an equivalent pro-amp, and thus, in your price of $300 for the amp, you are talking a EP2500 like amp into the mix! With a $200 EP1500 in bridged mode, you still have more clean power than the equivalent bash amps found in the commercial offerings.

the one area I still think is hard to beat is in the finish for the sub-$700 range subs. Veneers are expensive, and it will cost anywhere from $100-$250 to put a nice veneer on a sub.


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post #645 of 682 Old 03-31-2008, 01:27 PM
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DIY is here to stay, even if the commercial subs improve further. HSU...very easy to best for the dollar.

Epik and eD less easy,as they have more of a very capable DIY way,they use much more substantial drivers in cabinets and amps matched.Size is less of a factor.Just look at the flagsip units from Epik and eD.

Even if you are not saving much or at all,DIY is a great change of air.

I did not come to the DIY section to save money,not a money issue. I came to the dark side for the pleasure of building MY subs the way I like.This alone makes DIY viable and worthy of my time.

I can build a given number of units to satisfy my needs for bass ... and fit...just in the limited space I have.

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 #646 of 682 Old 03-31-2008, 01:31 PM
 
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Originally Posted by chasw98 View Post

The flaw with this argument is that if you asked Hsu or SVS to build one sub, then I expect it would cost a lot more than mass producing 100 or more subs. If the DIY'er were to produce subs at the quantity of some of the smaller sub manufacturers then that would be apples to apples or the manufacturer to build one sub as a DIY'er does. What would the manufacturer charge for one sub? Quite a bit more than a DIY'er.

There is nothing preventing the DIYer from deciding to build 500 subwoofers and selling 498 of them, is there ?

Of course, he is no longer a DIYer. He is now a manufacturer. And he gets to talk to OSHA, EEOC, IRS, etc ...

A manufacturer does not get into business to sell one "widget".

And a DIYer is not going to build 500 subwoofers.

Both commercial and DIY have a place.

There are two mindsets on all this. Most DIYers could work overtime for a few weekends, or do some handyman work, and make more than enough to offset the "savings" vs. commercial.

If one wants to spend $1000 on a subwoofer, and looks at, say, a pair of MFW-15's compared to DIY, it breaks down like this:

MFW-15's: ... $999 plus shipping.
....................Thrill of opening new boxes: Priceless

DIY ..............Two 15 inch drivers from eD: $370
................... One LT-1300 Plate amp: $350
................... Ports, wood, Glue, etc: ... ??? $$$
................... Labor to build it: ... ??? $$$
................... Feeling of pride when one is done: Priceless

One can substitute any number of alternatives for both examples, as listed above. But to either person, there is a lot of joy over the new subs.

And that IS what this is all about, isn't it ?
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post #647 of 682 Old 03-31-2008, 01:56 PM
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Thomas has been throwing out this 25x vas number a lot around here and I don't want this to create confusion, there is nothing magical about this number at all. It is simply a figure, a safe estimate of where an IB ought to be, if you are 20x vas you would not notice a difference between that and a 25x vas box. Nothing happens to make the woofer sound "boxless" at 25x vas because there are a variety of things that determine what can contribute to that effect. There is the drivers fs and qts, both of which will never be truly reached in an IB system. Lets look at those Fi IB drivers, if we do 25x vas then the fsc is 23.42Hz while the fs is 22.9Hz, still off. Also the systems qtc is 6.78 while the drivers qts is 6.36, note that these numbers don't magically align at 25x vas, nor do they ever. Furthermore, what is the reference point for this magical "boxless sound" is it the lowered fsc of the system? is it the lowered qtc of the system? That can't be it, because you can design a smaller sealed system with lower fsc and qtc than that, the only reference point you have is the free air parameters which is pretty useless. If I were to get a fi car IB 18 that had its specs altered slightly so that it had a qtc of .70 in a 25x vas enclosure and fsc of 24Hz would it magically sound like it was in a box again? Of course not! so if the lowered fsc and qts is not whats directly contributing to this boxless sound than what is? The sheer size of the enclosure? Well simply making your box big isn't necessarily going to make your woofer sound like its boxless, especially if your attics are made of what most of them are these days. So what if you were to make an enclosure in your attic, use plywood and panel off an area of your attic/basement into "large sealed box" your box that is say, 10x vas. You would have much less colorations than it would if made with junk and a larger enclosure. Ok, so what if you say its the lack of air spring distortion that makes an IB sound so incredibly articulate? As you have seen air spring distortion really doesn't become an issue until you start to get small sealed boxes, even at 1x vas you are likely not going to experience it with most drivers.

Ultimately you need to see just how the drivers model in the system, there are no magic number, be them 5x vas, 10x vas 25x vas or 100x vas. Those are all just the point where various people chose their compromise for their IB. I hate all this attention that we give to parameters like the Qtc, vas and fs, what really matters is frequency response of the system. Heres something fun to do, try modeling an AE IB15 for an IB with Qtc of 0.7 and have a look at the corresponding fr, its dead flat to 20Hz, when do you ever see a sealed system, especially one with a qtc of 0.7 get a flat anechoic response to 20Hz? No other driver that I have seen does that, you don't need an LT circuit to get the most from your low end even in anechoic rooms. When you really look at just how various drivers actually perform in their alignments you start to realize just how useless of a parameter the Q of the system is when you just look at it by itself. You simply cannot generalize them, some drivers will sound boomy with a Q of well below 0.5, others can have ruler flat response with a Q of 0.7. A high Q is anything but a sound way to prevent over excursion down low and a low is anything but a sure way to get a subs frequency response flat to lower frequencies, even if it does have a fairly low fs.


Craig, you have cited the impracticality of an IB due to Thomas's 25x vas spec, you needn't throw it out so easily, you can easily get a very good IB system with 8 ficar IB18's in a 1000 cubic foot or smaller airspace, especially depending on if you want to actually panel it off to prevent leaks.
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Originally Posted by armystud0911 View Post

Thomas has been throwing out this 25x vas number a lot around here and I don't want this to create confusion, there is nothing magical about this number at all. It is simply a figure, a safe estimate of where an IB ought to be, if you are 20x vas you would not notice a difference between that and a 25x vas box. Nothing happens to make the woofer sound "boxless" at 25x vas because there are a variety of things that determine what can contribute to that effect. There is the drivers fs and qts, both of which will never be reached in a non IB system. Lets look at those Fi IB drivers, if we do 25x vas then the fsc is 23.42Hz while the fs is 22.9Hz, still off. Also the systems qtc is 6.78 while the drivers qts is 6.36, note that these numbers don't magically align at 25x vas, nor do they ever. Furthermore, what is the reference point for this magical "boxless sound" is it the lowered fsc of the system? is it the lowered qtc of the system? That can't be it, because you can design a smaller sealed system with lower fsc and qtc than that, the only reference point you have is the free air parameters which is pretty useless. If I were to get a fi car IB 18 that had its specs altered slightly so that it had a qtc of .70 in a 25x vas enclosure and fsc of 24Hz would it magically sound like it was in a box again? Of course not! so if the lowered fsc and qts and whats directly contributing to this boxless sound than what is? The sheer size of the enclosure? Well simply making your box big isn't necessarily going to make your woofer sound like its boxless, especially if your attics are made of what most of them are these days. So what if you were to make an enclosure in your attic, use plywood and panel off an area of your attic/basement into "large sealed box" your box that is say, 10x vas. You would have much less colorations than it would if made with junk and a larger enclosure. Ok, so what if you say its the lack of air spring distortion that makes an IB sound so incredibly articulate? As you have seen air spring distortion really doesn't become an issue until you start to get small sealed boxes, even at 1x vas you are likely not going to experience it with most drivers.

Ultimately you need to see just how the drivers model in the system, there are no magic number, be them 5x vas, 10x vas 25x vas or 100x vas. Those are all just the point where various people chose their compromise for their IB. I hate all this attention that we give to parameters like the Qtc, vas and fs, what really matters is frequency response of the system. Heres something fun to do, try modeling an AE IB15 for an IB with Qtc of 0.7 and have a look at the corresponding fr, its dead flat to 20Hz, when do you ever see a sealed system, especially one with a qtc of 0.7 get a flat anechoic response to 20Hz? No other driver that I have seen does that, you don't need an LT circuit to get the most from your low end even in anechoic rooms. When you really look at just how various drivers actually perform in their alignments you start to realize just how useless of a parameter the Q of the system is when you just look at it by itself. You simply cannot generalize them, some drivers will sound boomy with a Q of well below 0.5, others can have ruler flat response with a Q of 0.7. A high Q is anything but a sound way to prevent over excursion down low and a low is anything but a sure way to get a subs frequency response flat to lower frequencies, even if it does have a fairly low fs.


Craig, you have cited the impracticality of an IB due to Thomas's 25x vas spec, you needn't throw it out so easily, you can easily get a very good IB system with 8 ficar IB18's in a 1000 cubic foot or smaller airspace, especially depending on if you want to actually panel it off to prevent leaks.

This is all good. Now tell me ... When's the last time any sane person built a 1000 cubic foot subwoofer box for his home ?
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post #649 of 682 Old 03-31-2008, 02:10 PM
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That depends a lot on your definition of "sane". Its been done before, especially in basements where you already have a room that is paneled and sealed off, attics are more tricky. What "sane" person goes out and builds their own subs anyway? What sane person dumps thousands into testing them out in a massive comparison? Some folks love to work with their hands, a buddy of mine dumps way more money into his hobbies where he works on cars doing what could be done better by a professional for less money and WAAAY less time, but thats what he enjoys doing in his free time, that is his entertainment.

Really craig it doesn't have to be that hard, all finished basements have unfinished storage areas, just use that space as your IB enclosure, most likely it will be at LEAST 1000 cubic feet, often times more like 3000 cubic feet, more than enough room to have a substantial IB system in, even if you don't seal it off. Furthermore, most attics are quite large as well, a friend of mine lives in a simple condo and he has a closed off attic space (from his neighbors) and his airspace is about 5000 cubic feet. Why is it so unrealistic to have a home with 2000-3000 cubic feet of unused airspace?
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post #650 of 682 Old 03-31-2008, 02:21 PM
 
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Quote:
Originally Posted by armystud0911 View Post

That depends a lot on your definition of "sane". Its been done before, especially in basements where you already have a room that is paneled and sealed off, attics are more tricky. What "sane" person goes out and builds their own subs anyway? What sane person dumps thousands into testing them out in a massive comparison? Some folks love to work with their hands, a buddy of mine dumps way more money into his hobbies where he works on cars doing what could be done better by a professional for less money and WAAAY less time, but thats what he enjoys doing in his free time, that is his entertainment.

Really craig it doesn't have to be that hard, all finished basements have unfinished storage areas, just use that space as your IB enclosure, most likely it will be at LEAST 1000 cubic feet, often times more like 3000 cubic feet, more than enough room to have a substantial IB system in, even if you don't seal it off. Furthermore, most attics are quite large as well, a friend of mine lives in a simple condo and he has a closed off attic space (from his neighbors) and his airspace is about 5000 cubic feet.

You have not been paying attention to the argument. The discussion was about a "sealed subwoofer" vs. an "IB subwoofer", with the idea being presented that an IB is nothing more than a large "sealed" subwoofer. I merely pointed out that the idea of building a 1000, 2000 or 3000 cubic foot enclosure was not realistic.

It was not about an already existing adjacent space which one wants to use for an IB.

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post #651 of 682 Old 03-31-2008, 02:30 PM
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Originally Posted by penngray View Post

Yes, we dont count our time as value but it is no matter what someone's opinion is. It has to have value when you are doing comparisons.

Its pointless to do comercial vs DIY comparisons unless we are fair to both sides.

So, instead of surfing the internet and watching tv for 8-16hrs, you spend that building a DIY project, how much is that time really worth? IMO it's wasted time anyway and thus pretty cheap, if not free.

Now if I took off work to build my sub, well then I can definatly put a dollar/hr value on the time because of the money I wouldn't make.

YID DIY
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Ahh, I understand that, I simply thought, since you quoted me, that my idea of paneling off a room into a large sealed box was unrealistic. I was aware of that argument of sealed vs IB and thought we moved past that, my entire point was that there is no magic line where you go from sealed to IB. I don't know of any sane people either who build 3000 cubic foot sealed sub boxes, the thought is so ridiculous that it flew over my head that that is what you meant.
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Originally Posted by armystud0911 View Post

Ahh, I understand that, I simply thought, since you quoted me, that my idea of paneling off a room into a large sealed box was unrealistic. I was aware of that argument of sealed vs IB and thought we moved past that, my entire point was that there is no magic line where you go from sealed to IB. I don't know of any sane people either who build 3000 cubic foot sealed sub boxes, the thought is so ridiculous that it flew over my head that that is what you meant.

Actually, it started when you misunderstood me. I was not taking on Thomas about the impracticality of an IB system see this portion of your post:

Quote:


Craig, you have cited the impracticality of an IB due to Thomas's 25x vas spec, you needn't throw it out so easily, you can easily get a very good IB system with 8 ficar IB18's in a 1000 cubic foot or smaller airspace, especially depending on if you want to actually panel it off to prevent leaks.

I was agreeing with Thomas that building such a large enclosure as a sealed subwoofer was not practical.

If one has the adjacent space, and if loading that space with the back wave of a multi driver set up works well in one's home, then that space is "free".

But to BUILD something that big ...
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post #654 of 682 Old 03-31-2008, 02:45 PM
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Originally Posted by Looneybomber View Post

So, instead of surfing the internet and watching tv for 8-16hrs, you spend that building a DIY project, how much is that time really worth? IMO it's wasted time anyway and thus pretty cheap, if not free.

Now if I took off work to build my sub, well then I can definatly put a dollar/hr value on the time because of the money I wouldn't make.

Lets face it, we spend time on the net because we want to. Other things that we don't want to do, are work. If we make enough money or have flexible enough jobs, we can hire people to do the things we don't want to do, such as cook, clean, do things around the house and outside. Most middle class people are not in the necessary financial state or have the flexibility to work more with their jobs to hire out all the stuff they don't want to do around the house. So if you are working 40-50 hours a week in a normal job making 50-80k a year, you inevitably will have free time that you spend doing work to manage your home and additional free time that you spend entertaining yourself, be it alone or with family. The balance that everyone need to discover with DIY is how much they enjoy doing it, if you don't enjoy doing it, is it worth your time to build it or not? If you do enjoy doing it is that time better spent with your family or not? There are gray areas for all this, some people have their kids help them with diy and thus it can be a unique bonding experience, other people diy when they need personal time and space to be alone. Often times people like doing diy for some time each day or week but grow sick of it if they do it too much and it becomes "work". Ultimately, you need to find a balance and what works for you in your rhythm of life.
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post #655 of 682 Old 03-31-2008, 03:13 PM
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Originally Posted by armystud0911 View Post

Thomas has been throwing out this 25x vas number a lot around here and I don't want this to create confusion, there is nothing magical about this number at all. It is simply a figure, a safe estimate of where an IB ought to be,

The 25X summed Vas numbers were posted because they illustrate at what point with regard to box size the driver's Qts = box Qtc....

When a person accesses the IB FAQ page, there is information about different sized IB 'boxes' starting with 4 times Vas....As a rule of thumb the recommendation is for people to have approx 10X Vas for their IB subs..

Craig,

The IB forum has been running for almost 9 yrs, to date no one has gone to the extreme of building an addition to their house specifically for an IB....

Typically IB's are 'vented' into the attic, basement, crawl-space, adjacent rooms, closets, enclosed areas under a stairway, and a few instances to the outside world..


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However, from what I have seen, often times there is absolutely no point at all where the qts = qtc, no matter how big you get, in the case of the fi IB, this difference is definitely there, a qtc of 0.677 where the qts is 0.636, thats a difference 0.041 which is substantial when it comes to the qtc of a system. If you go to 100x vas, it drops to 0.668, if you drop your box to 20x vas, its 0.680, not much different at all, like I said, there is nothing magical about 25x, nothing happens there that doesn't elsewhere, you still get a qtc drop afterwords, if you were to plot the qtc/vas for every sub you would find those curves to be different and not the same across the board, the 25x vas thing is just a point on that curve that you (or someone else) picked where many drivers no longer drop the qtc in a meaningful way, you can choose whatever point on that curve you want, it varies from driver to driver, sometimes it may be 15x, sometimes as much as 50x or even 100x, its all up to you. What you determine to be a meaningful qtc drop is by no means set in stone though and as I said, it varies from driver to driver. Furthermore, as I said before qtc isnt not as important as we seem to make it to be around here, just the qtc is a VERY poor way to judge the overall roll off of the system.
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Originally Posted by Thomas-W View Post

The 25X summed Vas numbers were posted because they illustrate at what point with regard to box size the driver's Qts = box Qtc....

When a person accesses the IB FAQ page, there is information about different sized IB 'boxes' starting with 4 times Vas....As a rule of thumb the recommendation is for people to have approx 10X Vas for their IB subs..

Craig,

The IB forum has been running for almost 9 yrs, to date no one has gone to the extreme of building an addition to their house specifically for an IB....

Typically IB's are 'vented' into the attic, basement, crawl-space, adjacent rooms, closets, enclosed areas under a stairway, and a few instances to the outside world..

Thomas ... Of course no one would build something that size. The whole idea that a sealed subwoofer and an IB are the "same thing" is what prompted me to do the math about the size of enclosure one would have to build to match an IB.

My first exposure to an IB subwoofer was in 1980, an audiophile who had quad 15 inch Gauss drivers loaded into a heated garage. The guy also had B&W DM-6 floorstanding monitors all driven by McIntosh ... We sold him the speakers and Mcintosh gear ...

He made a hell of a Pastrami sandwich, too.

I am pretty sure 1980 was more than 9 years ago, but thanks for letting me know what people use for the "back end" of an IB ...
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Originally Posted by craigsub View Post

My first exposure to an IB subwoofer was in 1980, an audiophile who had quad 15 inch Gauss drivers loaded into a heated garage. The guy also had B&W DM-6 floorstanding monitors all driven by McIntosh ... We sold him the speakers and Mcintosh gear ...

He made a hell of a Pastrami sandwich, too.

Everyone knows a good Pastrami sandwich is far more important than any subwoofer...

I makes no claims to have invented anything with regard to IB subs. People were putting Altec 15"s in-wall during the 1950's. AFAIK the first manifold IB sub was created by Tom Nousaine in the mid 1990's.

Dan Wiggins, David Hyre, Tom Nousaine, and various members of the Bass-list were the resources I used for designing my first IB. The IB forum is simply an extension of the conversations with the people who assisted me; combined with my 9yrs of hands-on experience, plus feedback from the several hundred people who've built IB subs and posted about them.


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post #659 of 682 Old 03-31-2008, 04:17 PM
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Originally Posted by ssabripo View Post

1) IB system, unlike Sealed systems, has no pressure on the back movement of the subwoofer, and therefore does not effect any damping, and thus the volume area has to be large enough (10x Vas) to insure that there is no dampening effect on the drivers.

That statement doesn't really make a point though, as you are saying an IB isn't like a large sealed sub because the large sealed sub would have to be REALLY large. Yeah, that's the whole idea.

From your own link regarding bass traps:

Quote:


Absorption panels meant to tame mid and high frequencies are generally fairly thin, and they can be placed flat on the walls and ceiling where they intrude very little. However, bass traps by definition need to be fairly large, or at least thick, and they are most effective when placed in or near the room corners.

A few inches of absorption just in't going to cut it in the subwoofer range.

Quote:


As "LLT" has certain requirements that improve some of the issues with regular EBS alignments, the IB also has some characteristics that resolve issues over its sealed counterpart, from system damping, to the elimination of the box interaction of the rear-wave and the compressing air-mass inside the box changing the 'Q' of the system, to name a couple.

Sure, but a LLT is still a ported subwoofer. It's just a large and low tuned one. An IB is still a sealed subwoofer, just a large one that tends to use an adjacent space as the enclosure.

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Originally Posted by Richard View Post

Actually you still have a box even though it's really large. If you wouldn't have a box, you would have a dipole subwoofer, and that's different from a sealed or an IB subwoofer because you will have back wave cancellation

Exactly.

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Originally Posted by Mark View Post

The important detail is that the affect of the listening room at low frequencies is also largely minimum phase, where boosting or attenuating frequency ranges at the listening position show mostly the same phase changes we would see if we matched this response outdoors with PEQ

Well you know me Mark, I'm going to want to see measurements - not because I don't believe you, just because I like to see things with my own eyes. I'll see if Ilkka is up for any in-room measurements with his monster LMS subwoofer.


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post #660 of 682 Old 03-31-2008, 04:20 PM
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Hold on.....My jensen triaxial loaded in my trunk of a "76" chrystler Newport.

If I only has the Vas on that triax.This was some time ago

KG


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