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2 hz tuning - pros and cons - Page 8

post #211 of 302
Thread Starter 
Quote:
Originally Posted by Ricci View Post

... from a system many times the size of a comparable performing sealed system while ignoring things like vent noise and pipe resonances. It just doesn't make sense to build anything like this unless you have an IB sized space available.

I've covered all of this. You can make the box any size you like as long as you keep the same tuning. Just like a sealed box, just use eq to get it where you want it. I only used the size because it provided an easy comparison to a known product.

I am not ignoring vent noise, in fact I've simulated the hell out of the situation with several different programs.

Pipe resonances have been shown IN EVERY SIMULATION done by both you and me to be a non issue, less than 1 db ripple.

I know you don't think the compromises are worth it, that does not invalidate the simulations. I agree that compression testing will very likely show a situation worse than the simulation but no where near as bad as you seem to think.

The normal course of design for ANY design is to simulate with acceptable velocity limits as predicted by the t/s simulator, 10 or 17 m/s are popular limitations set forth by diy'ers. You may or may not want to check the result with Flare It at that point. This is what everybody does all the time, how come it's not valid in this case?

I seriously don't care if the design is worth it anymore, I'm only arguing that it will work as simulated, just like every other sub works as simulated.
Edited by diy speaker guy - 12/11/12 at 1:26pm
post #212 of 302
Thread Starter 
What's up guys? A real world example has you stumped as you try to figure out how to argue against 45 m/s velocity coming out your little tiny nose hole?

(No doubt high compression situation but it does NOT revert to a sealed hole even at WELL over 10x the core velocity of the hole.)

I fielded a constant and consistent barrage of questioning, do me the same favor. It's too easy to argue against something (a simulation) which I have no practical way of proving by measurement, not so easy to argue against a common natural occurance that has been measured.
Edited by diy speaker guy - 12/11/12 at 1:44pm
post #213 of 302
The problem is not whether things like air compressors exist and whether people 'believe' in the physics behind compressed air - it's the weakness of the forces at work. The large chamber will absorb the additional pressure before it ever gets through the narrow tube once 'significant' turbulence occurs because what you have is a reverse hydraulic lever effect - it takes a significant increase in pressure in the large (main) chamber to effect a small pressure change in the tube (port). One thing I do wonder - if you stuffed the tube with 'poly fill' to intentionally slow down the airflow and prevent the dreaded turbulence, what would the effect be? If poly increases apparent cabinet volume, can it also increase apparent port length, or diameter?
Quote:
Originally Posted by diy speaker guy View Post

What's up guys? A real world example has you stumped as you try to figure out how to argue against 45 m/s velocity coming out your little tiny nose hole?
(No doubt high compression situation but it does NOT revert to a sealed hole even at WELL over 10x the core velocity of the hole.)
I fielded a constant and consistent barrage of questioning, do me the same favor. It's too easy to argue against something (a simulation) which I have no practical way of proving by measurement, not so easy to argue against a common natural occurance that has been measured.
post #214 of 302
Why don't you just build it and measure it already since you seem to have it all figured out?
post #215 of 302
"I think this thread has gone 'round and 'round because of the dozens of comments on port compression, when the simulations have shown, and not been refuted that I can see, that there won't be any, except maybe with a track or two, like F'in Irene which I believe has some strong 5 Hz rotor blade noise."

noah, the spl advantage is about 2.5 times less than "a couple db". it is 0.1db at 20hz and increases to 0.8db at 10hz, assuming that the port is not chuffing (very large roundover required). if that is worth it for the builder, great.

the tradeoff being that if you do go below somewhere between 7 and 9hz and exceed the core limit of the port, the thing will go turbulent, and who knows what kinds of sounds it might start making.

most of the running around in circles has been related to what happens when the core velocity of the port is exceeded, as that is not reflected in any of the t/s models.
Edited by LTD02 - 12/11/12 at 2:15pm
post #216 of 302
Thread Starter 
Quote:
Originally Posted by imagic View Post

The problem is not whether things like air compressors exist and whether people 'believe' in the physics behind compressed air - it's the weakness of the forces at work. The large chamber will absorb the additional pressure before it ever gets through the narrow tube once 'significant' turbulence occurs because what you have is a reverse hydraulic lever effect - it takes a significant increase in pressure in the large (main) chamber to effect a small pressure change in the tube (port).

Not sure why you think the combined simulations are not taking this into consideration. The arguement here (at the extreme end) is that exceeding the core velocity in Flare It will very quickly cause the hole to not pass ANY air. The sneeze example shows this is not true until you get well past at least 10 x the core velocity red line in Flare It.
Quote:
One thing I do wonder - if you stuffed the tube with 'poly fill' to intentionally slow down the airflow and prevent the dreaded turbulence, what would the effect be? If poly increases apparent cabinet volume, can it also increase apparent port length, or diameter?

Stuffing the port blocks the air flow. If you use a little stuffing in a port you get the same effect as stuffing in a transmission line but if you increase it, it will eventually completely block the airflow.
post #217 of 302
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

noah, the spl advantage is about 2.5 times less than "a couple db". it is 0.1db at 20hz and increases to 0.8db at 10hz, assuming that the port is not chuffing (very large roundover required). if that is worth it for the builder, great.

Post 137 is the valid comparison, not the graph you are looking at.

Xmax limited max SPL at the lowest frequency of interest is the only thing that matters, and the graphs you refer to (at same power level) are not a valid comparison in that respect.

Noah is correct (in the context of this conversation) and you are not.

If equal power simulation was relevant then you would be correct.
post #218 of 302
Thread Starter 
Quote:
Originally Posted by Stereodude View Post

Why don't you just build it and measure it already since you seem to have it all figured out?

Why don't you? Probably for the same reason I can't. There simply is no affordable supporting equipment to set this up and measure properly.
post #219 of 302
As far as equating a sneeze to the operation of a helmholtz resonator there is a bit of a disconnect there. You can force a ton of air through a tiny tube with a compressed air system but that has little to do with the way a resonant system works.

This would be easy to measure with fairly standard measurements. It is easy to show when compression is happening and the signal is not being tracked. There is no need to measure port airspeed when it is far easier to monitor the strength of the port contribution. No I won't be doing this. Someone else can set that up. I already know what will happen.
post #220 of 302
Thread Starter 
Why is everyone so scared to even mention the sneeze? It invalidates all of your collective arguments in one fell swoop.

EDIT - posted too soon.

SO you are saying the power of your lungs is several times more powerful than the Bl of the two 18 inch drivers?

Resonance has nothing to do with this. It's a core velocity issue, and it's not an issue. The arguement has been stated that high enough velocity will effectively seal the hole at levels shown in my sim, this will simply not happen.
post #221 of 302
Thread Starter 
This thread has no point anymore. I've provided proof with simulations and real world measured occurances. No one has effectively argued any of it despite pages of conjecture and speculation with no supporting evidence. Every link that has been posted to disprove what I'm saying actually backs up my POV.

Neither side is gaining any ground. I will agree to disagree and stop posting completely if everyone else does too, with the agreement that we absolutely do not agree with each other.
post #222 of 302
Quote:
Originally Posted by diy speaker guy View Post

Why don't you? Probably for the same reason I can't. There simply is no affordable supporting equipment to set this up and measure properly.

So why the hell do you care if it works or not if you're not going to build it? You seem like a kid with ADD. Though I have to admit, I'm impressed with your trolling skills but it's all getting old pretty quick.
post #223 of 302
Quote:
Originally Posted by diy speaker guy View Post

Resonance has nothing to do with this.


Wow. And with that I bow out.
post #224 of 302
Thread Starter 
Quote:
Originally Posted by N8DOGG View Post

So why the hell do you care if it works or not if you're not going to build it? You seem like a kid with ADD. Though I have to admit, I'm impressed with your trolling skills but it's all getting old pretty quick.

As stated in post 1, I wanted to discuss the pros and cons of the simulation, simple as that. The information in this case is several times more valuable than the finished product, which I was only halfheartedly considering building in the first place.

I apologize for my passion and for trying to answer each individual point. If you (and at least one other person) think that's trolling I will gladly leave avsforum for good.
post #225 of 302
Thread Starter 
Quote:
Originally Posted by Ricci View Post

Wow. And with that I bow out.

The lungs and nasal passage are also a resonant system.
Edited by diy speaker guy - 12/11/12 at 3:16pm
post #226 of 302
Quote:
Originally Posted by diy speaker guy View Post

Why is everyone so scared to even mention the sneeze? It invalidates all of your collective arguments in one fell swoop.
EDIT - posted too soon.
SO you are saying the power of your lungs is several times more powerful than the Bl of the two 18 inch drivers?
Resonance has nothing to do with this. It's a core velocity issue, and it's not an issue. The arguement has been stated that high enough velocity will effectively seal the hole at levels shown in my sim, this will simply not happen.

I think nobody mentions the sneeze since it offers a poor analogy. The analogous part actually shoots you in the foot and you should never have mentioned it. Try this, get yourself some strong duct tape and tape your mouth shut, then snort some pepper. When you start to sneeze the intense pain you feel is the compression of the little port, you will do every thing you can to rip that tape off and open a large port because your head is acting like a sealed box alignment...
post #227 of 302
Quote:
Originally Posted by diy speaker guy View Post

Post 137 is the valid comparison, not the graph you are looking at.
Xmax limited max SPL at the lowest frequency of interest is the only thing that matters, and the graphs you refer to (at same power level) are not a valid comparison in that respect.
Noah is correct (in the context of this conversation) and you are not.
If equal power simulation was relevant then you would be correct.

post 137 is not a valid comparison at all because you just turned down the power on the sealed cab without making a similar adjustment to the ported cab.

again, you are using a t/s model and that is a total fail.

well, let's end this non-sense right here. the port air velocity in your design at 2hz is 72 m/s, which is 162 mph! that is a freak'n category 5 hurricane. lol.

if you don't think blowing 162 mph wind back and forth through a 2" port tube two times per second isn't going to make a sh_t ton of noise, then you are in total fantasyland. do you really need an experiment to test that???

the key takeaway here is one that josh has made a few times--models are pretty good when you stay low level and keep designs kind of average.

what you have done is reductio ad absurdum.
post #228 of 302
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

well, let's end this non-sense right here. the port air velocity in your design at 2hz is 72 m/s, which is 162 mph! that is a freak'n category 5 hurricane. lol.

As stated in post 1, and about 60 times since then, this is not supposed to be able to play 2 hz. It was designed to be tuned so the problems would be below the rolloff of the supporting equipment. Why is this so hard to understand? There is absolutely no problem above 5 hz, and I'd argue even lower. The signal chain IS the high pass filter.
Quote:
post 137 is not a valid comparison at all because you just turned down the power on the sealed cab without making a similar adjustment to the ported cab.

AFAIK, ALL valid comparisons compare xmax limited max spl at the lowest frequency of interest. Comparing equal power does not reflect that and I can't see any usefullness to comparing that unless you are limited by the amp power and not xmax.

But let's just stop now. If I'm seen as a troll I don't want to continue but find it very hard to ignore posts directed at me.
Edited by diy speaker guy - 12/11/12 at 3:00pm
post #229 of 302
Quote:
Originally Posted by diy speaker guy View Post

As stated in post 1, and about 60 times since then, this is not supposed to be able to play 2 hz. It was designed to be tuned so the problems would be below the rolloff of the supporting equipment. Why is this so hard to understand? There is absolutely no problem above 5 hz, and I'd argue even lower. The signal chain IS the high pass filter.
But let's just stop now. If I'm seen as a troll I don't want to continue but find it very hard to ignore posts directed at me.

You're creating MORE problems within the audible bandwidth with this design. How can you not understand that?

There absolutely ZERO advantages to building this alignment of yours. It will be a mess all over. You will gain nothing.
Quote:
Originally Posted by N8DOGG View Post

So why the hell do you care if it works or not if you're not going to build it? You seem like a kid with ADD. Though I have to admit, I'm impressed with your trolling skills but it's all getting old pretty quick.

Quote:
Originally Posted by Ricci View Post

Wow. And with that I bow out.

Werd and werd.
Quote:
Originally Posted by diy speaker guy View Post

Why don't you? Probably for the same reason I can't. There simply is no affordable supporting equipment to set this up and measure properly.

Wait! WTF!?!?!? All this BS back and forth with all of us and you aren't going to even build the damn thing?

*sigh*
Edited by Scott Simonian - 12/11/12 at 3:06pm
post #230 of 302
"As stated in post 1, and about 60 times since then, this is not supposed to be able to play 2 hz....Why is this so hard to understand?"

because that is why you turned down the power in post 137 so the sealed driver excursion wouldn't go out of control and made the argument that the ported wouldn't need to be turned down because of the port.

the only way that is possible is hurricane force wind blowing out of the port.
post #231 of 302
FWIW I was unable to unearth the efficiency gains you claim using WinISD and a different driver's parameters - the LMS-Ultra. Simulated running at 1,000 watts, here's a powerful driver with xmax you wouldn't want to leave on the table, right? So how do you explain this graph, which seems to strongly support the notion that it will behave like a sealed box with that design? (unless you get really excited about a simulated gain of .32db)


Quote:
Originally Posted by diy speaker guy View Post

As stated in post 1, and about 60 times since then, this is not supposed to be able to play 2 hz. It was designed to be tuned so the problems would be below the rolloff of the supporting equipment. Why is this so hard to understand? There is absolutely no problem above 5 hz, and I'd argue even lower. The signal chain IS the high pass filter.
AFAIK, ALL valid comparisons compare xmax limited max spl at the lowest frequency of interest. Comparing equal power does not reflect that and I can't see any usefullness to comparing that unless you are limited by the amp power and not xmax.
But let's just stop now. If I'm seen as a troll I don't want to continue but find it very hard to ignore posts directed at me.
post #232 of 302
Thread Starter 
I turned down the power on the sealed so neither one of them would pass xmax until below 3 hz. As mentioned, it might be a bit more fair to add a bit more power to the sealed since it doesn't really need to go that low, but you still can't compare same power if you want to figure out how loud either will be at 4 or 5 hz if one of the designs can't handle that power at that frequency.
post #233 of 302
Thread Starter 
Quote:
Originally Posted by imagic View Post

FWIW ...
Well, I surely do not want to expand the topic, I'm trying to narrow it or end this completely but I'd be happy to discuss this by email or PM if you like. Post 137 shows my opinion on the matter. I've given all details of exactly what I simulated so you can recreate that if you like.
post #234 of 302
I think it's a worthwhile experiment in the mysthbusters vein. If this was built and tested and the whole process was properly filmed and documented it would be awesome no matter how it turned out. A real science project. Discussing any more without taking another step is definitely not worth it.
post #235 of 302
Thread Starter 
I agree with that completely but hopefully with a bit more scientific rigor than Mythbusters.
post #236 of 302
Thread Starter 
Quote:
Originally Posted by Scott Simonian View Post

Wait! WTF!?!?!? All this BS back and forth with all of us and you aren't going to even build the damn thing?
*sigh*

Did you read post 1? I never said I was going to build it, I wanted to discuss a simulation. Many people say the sim is wrong and that is fine and welcome but I was hoping to see some evidence.

I did mention the drivers were in my price range now and that's why I simulated this in the first place but I never said I was going to buy them. I did get a bit excited at one point around page 2 or 3 until you guys beat the will to continue living out of me.
post #237 of 302
Well, we have ALL been saying that your simulation is inaccurate and will not work. So what has all these last few pages been about if you have picked that up?


And btw, this is the Do It Yourself audio section. I am to believe that you would eventually build what ever it is you're talking about. AVS has an Audio Theory subforum elsewhere.
post #238 of 302
Quote:
Originally Posted by Ricci View Post

Wow. And with that I bow out.

Actually diy is correct for the current point of discussion; the port velocity is high because of resonance, but the debate is about the implications of the velocity, not what causes it.
Edited by noah katz - 12/11/12 at 3:30pm
post #239 of 302
Quote:
Originally Posted by diy speaker guy View Post

Did you read post 1? I never said I was going to build it, I wanted to discuss a simulation. Many people say the sim is wrong and that is fine and welcome but I was hoping to see some evidence.
I did mention the drivers were in my price range now and that's why I simulated this in the first place but I never said I was going to buy them. I did get a bit excited at one point around page 2 or 3 until you guys beat the will to continue living out of me.

Man. I forgot where I was for a moment. For a second I imagined I was in my living room listening to my wife and pre teen daughter arguing back and forth over something that would never come to fruition. biggrin.gif
post #240 of 302
Thread Starter 
Quote:
Originally Posted by Scott Simonian View Post

Well, we have ALL been saying that your simulation is inaccurate and will not work. So what has all these last few pages been about if you have picked that up?
And btw, this is the Do It Yourself audio section. I am to believe that you would eventually build what ever it is you're talking about. AVS has an Audio Theory subforum elsewhere.

If this is not the appropriate place for discussion of theory please ask a mod to delete the thread.
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