Hi, if I get 55Hz in an 1.6 Cf sealed enclosure, and I fill it with proper amount of poly-fill, will I get an important down of hz with that action? I have read many users said polyfill does miracles, but they never tells how many hz it dropped down. 😕😕😕
Tom Nousaine did the definitive analysis of box stuffing some years back using poly-fil in a 1.4ft^3 sealed box with a fsb of 56.6Hz. Close enough? So, take a look at it, you should get the answers your looking for (ie between 14%-36% gain in effective volume and a decrease down to around 50Hz depending on how much you use and a handy table to get you there.)
Making a tiny 1.6 cu ft box because your sim said so is like driving into a swamp because your GPS said so.
The isothermal versus adiabatic argument goes back 50 yrs. Perhaps a small but welcome benefit esp if you get some seriously effective stuffing to also address interior noises (I rather like felt rug underlay).
B.
The isothermal versus adiabatic argument goes back 50 yrs. Perhaps a small but welcome benefit esp if you get some seriously effective stuffing to also address interior noises (I rather like felt rug underlay).
B.
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General observations on stuff and stuffing.
Hi Y'all,
Post #5: "...I rather like felt rug underlay."
We used to pack all the stuffing/filling/lining material that had to go into a box under a board, and compressed it to get an idea about the solid volume loss, and then adjust the internal volume calculations/losses/gains accordingly. But, that only gave a vague starting point...
Now, I find it easier to get a starting point from a simulation. 🙂
I'll attach a discussion of the thread subject by Douglas Purl and Ken Kantor.
Regards,
Hi Y'all,
Post #5: "...I rather like felt rug underlay."
We used to pack all the stuffing/filling/lining material that had to go into a box under a board, and compressed it to get an idea about the solid volume loss, and then adjust the internal volume calculations/losses/gains accordingly. But, that only gave a vague starting point...
Now, I find it easier to get a starting point from a simulation. 🙂
I'll attach a discussion of the thread subject by Douglas Purl and Ken Kantor.
Regards,
Good to see you post that old discussion. Naturally each time I read it, I get a kick out of Ken Kantor dismissing sims!
But you have to read between the lines. Kantor is saying he fools at great length with type and quantity of stuffing (and other carpentry issues) till it sounds good to his ears. Perhaps at some point, his box has achieved a tasty audio retail store sound with a marketable mix of tubby and low and works fine on the music his customers like in the environment they play it in. Please don't take that as "faint praise" - I am simply outlining how products are brought to market by skillful designers.
The OP is asking to lower the system resonance and might have other tricks to address the resulting speaker sound as he sees fit. And that is roughly what I say about blindly following sim marching-orders to the destination the sim wants to take you.
So, without doubting a word of that good discussion, I am only pointing out that tastes, goals, DSP tools, and systems vary.
Ben
But you have to read between the lines. Kantor is saying he fools at great length with type and quantity of stuffing (and other carpentry issues) till it sounds good to his ears. Perhaps at some point, his box has achieved a tasty audio retail store sound with a marketable mix of tubby and low and works fine on the music his customers like in the environment they play it in. Please don't take that as "faint praise" - I am simply outlining how products are brought to market by skillful designers.
The OP is asking to lower the system resonance and might have other tricks to address the resulting speaker sound as he sees fit. And that is roughly what I say about blindly following sim marching-orders to the destination the sim wants to take you.
So, without doubting a word of that good discussion, I am only pointing out that tastes, goals, DSP tools, and systems vary.
Ben
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polyfill (pillow stuffing) is a very poor choice for use at low frequencies below 100Hz it is a waste of space.
Seriously Ben, it reads like you've never actually seen a simulator in real life. It sounds like your only experience with simulators is a second hand story from someone that didn't know how to use one.
Simulators show the predicted results based on USER INPUTS. They don't recommend anything and they have no destination that the sim wants to take you to.
In some of the more basic simulators there are choices you can pick from - WinISD has several closed and ported box mathematically derived choices that you can chose from but there is a good healthy range between these options and YOU DON'T GET ANYTHING AT ALL UNLESS THE USER CHOOSES ONE OF THEM. It's also recognized that these choices are just a starting point, if they weren't there wouldn't be any point to any of the other graphs besides transfer function because they wouldn't matter.
There is not a single simulator that I have ever seen in my life that chooses a box size for the user. I have at least 1/2 dozen (maybe even close to a dozen) simulators on my computer right now, not a single one of them behaves the way you constantly describe and I've told you this several times.
The only thing that comes close to what you describe is the crappy online box designers that spit out a .707 alignment box size for a given Fs, Vas and Qts. These are NOT simulators, they do not provide any kind of simulation. While these programs might be slightly better than just guessing I would never recommend that anyone ever use them, they are garbage made for people that don't know any better and people that don't realize we aren't stuck with using simple math for popular alignments from the 50s.
+1 for Just a guy.
A simulator is a fast calculator.
The user learns how to ask a question and the calculator gives an answer to the question asked.
If you ask a silly question, the calculator will give you a silly answer !
A simulator is a fast calculator.
The user learns how to ask a question and the calculator gives an answer to the question asked.
If you ask a silly question, the calculator will give you a silly answer !
I ask myself all the time..........
I ask myself all the time: "how in the world did I get anything done in all the years pre-simulator" ?
Ben, stay your ground, fight the good fight 🙂
I ask myself all the time: "how in the world did I get anything done in all the years pre-simulator" ?
Ben, stay your ground, fight the good fight 🙂
Scott -
The answer, in the case of sealed boxes as in this thread is, "... because there is only one parameter: how big will my spouse* let me build it". OK, maybe one-and-a-half parameters if you count stuffing, as in this thread.
Which leads to the necessary conclusion that people without spouses* have only half a parameter to fuss about.
Ben
*folks who taught in computer science departments in two major universities as i did are careful to always use non-sexist terminology.
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While I agree in principle with the sentiment Ben is trying (but failing) to express - that .707 qtc sealed boxes are rarely the best design choice - I vehemently disagree that this has anything at all to do with simulators.
If you tell a simulator to simulate a box with qtc = qts (infinite baffle, which is the lowest possible qtc) it will do it. If you tell it to simulate a box with qtc = 10, it will do it, although it will be too small the actually fit the driver in.
Almost without exception, IB is a better design choice than any other size of sealed box, as far as sealed boxes go bigger is almost always better. Unless the primary goal is small size.
If you want to go pen and paper old school that's fine and doesn't change anything. The choice in box size has to do with factors that have nothing to do with simulators. Simulators can show you things that can help you choose more wisely but they do not recommend anything. Paper and pen your way to a .5 qtc sealed box, or better yet forget the paper and pen and throw your driver in IB. It will perform better that way and it won't require a simulator.
I am guilty of getting off topic. The short answer is, yes, you will gain a little,
but over stuffing will also change the sound character. As to whether it's an improvement or a degradation, only your own ears can tell you that.
An oversized sealed enclosure will result in a lower Q. Some listeners will prefer a lower than .707 Q, while others might prefer something closer to 1.
The "closer to 1" listeners will often prefer a vented enclosure, for this very same reason.
If I was given the choice as to which airline captain I would fly with; 1) a 25 year old with 5 perfect years of simulator flight, or a 55 year old with 30 years of actual flying experience, I'd choose the 55 year old. But, hey, that's just me.
These days it's pretty safe to assume everyone has access to at least a simple equalizer (if not a full blown dsp) so the frequency response shape of a simple sealed box hardly matters, especially considering what the room is going to do with the response shape. Power handling and power required to reach excursion limits is a much more valid concern and that can't be fixed with eq, you can only improve it by increasing box size.
This is hardly a fair analogy. Let's change it up a bit to make it more realistic.
Would you prefer a box design from someone who had never used a simulator, had never built anything and had limited experience and understanding of a few commercial products? Or would you prefer a box design from someone that had extensive experience with simulators, had built many many things and correlated the sims to actual measurements of the stuff that was built?
Experience with a simulator does not preclude experience with actual physical products, both diy and commercial, and I think it's fair to say that around here the people that simulate extensively usually have a lot more practical experience with actual subs and measurements than those that don't.
All true.
But any Q is too much for reproducing music. A speaker should aim to be absolutely featureless*, at least within its designated range. So maybe no such thing as "oversized" resulting in too diffuse a bass thump for the OP. Sadly, getting Q very low in the real-world requires trade-offs.
One of the silly things about sims is the belief they perpetuate that there are good Q's to aim for and the sim will help you saw your box to get you there. Many an innocent DIY builder has been tricked into thinking "critical" resonance is a desirable design goal.
Ben
*or as Scott correctly points out, people who think a speaker should have a distinctive character can build a bass reflex box that gives them the bass jollies they like to hear.
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This is just silly and shows a misunderstanding of what q actually is. Q = zero isn't necessary. Q just describes the low knee and rolloff behavior (and to some extent the stored energy which isn't really audible as time smearing or important at reasonable q values). Q = zero would be flat response down to dc (or something like that). We can get pretty close to that now (with the exception that q = zero implies no stored energy and isn't actually physically possible) with modern drivers and dsp, even with extremely small boxes but it takes a lot of displacement and a lot of power.
What's important is flat response as measured at the listener position down to a reasonable frequency, not q.
Again, this has nothing at all to do with sims. And again, while I agree in principle with the premise, these beliefs have been around since the dawn of mathematical formulas that give a certain qtc based on t/s parameters, decades before simulators and long before computers were invented.
You are trying to create some silly myth that simulators are evil based on things that have nothing at all to do with simulators.
If a person is not smart enough to know what a "max flat" 0.707 qtc alignment is, or what a "critically damped" .05 qtc is or what IB (qtc = qts) is, or how any of those alignments behave, that's a lack of theoretical knowledge, it has nothing at all to do with simulators. Simulators don't recommend any qtc and they will simply show the results of the user inputs.
There are a lot of myths and misconceptions about how sealed boxes should be designed, simulators are not responsible for any of them. People with no theoretical understanding of what they are talking about are responsible.
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The Great Q-uest
If we could find a virtually "zero" Q woofer element on the market it must have a quite spectacular looks to maintain such physical properties to have a satisfying end result for the listener, wouldn't it?
Or, we could correct the bass response by means of an equalizer, which only shifts the Q problem from the element into the electronic filters, besides DSP then.
Also, we shouldn't forget the room response/interaction which affects the result much more on the bass response than for the greater part of the audio spectrum above bass frequencies, so, as long as most of us normally deadly humans have to stick with passive solutions, and the vast majority of contemporary woofer elements on the market being what they are, we have to cheat a bit with the Q value in order to reach a certain bass response, as such, it would bring us back to square 1 why sims matters for most of us, rest is academic drivel, so to speak. 😉
Anyway, for me rockwool rocks. 🙂
If we could find a virtually "zero" Q woofer element on the market it must have a quite spectacular looks to maintain such physical properties to have a satisfying end result for the listener, wouldn't it?
Or, we could correct the bass response by means of an equalizer, which only shifts the Q problem from the element into the electronic filters, besides DSP then.
Also, we shouldn't forget the room response/interaction which affects the result much more on the bass response than for the greater part of the audio spectrum above bass frequencies, so, as long as most of us normally deadly humans have to stick with passive solutions, and the vast majority of contemporary woofer elements on the market being what they are, we have to cheat a bit with the Q value in order to reach a certain bass response, as such, it would bring us back to square 1 why sims matters for most of us, rest is academic drivel, so to speak. 😉
Anyway, for me rockwool rocks. 🙂
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