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2 hz tuning - pros and cons - Page 5

post #121 of 302
I am not addressing the port. We all seem to agree the port is a non issue. I am saying that the driver is going to unload as if their is no port at all and the box will react like a too big sealed enclosure and the driver will fail.Now, those are just thoughts, but reality is a different thing. I am saying the port wil not work at all. I am saying it will be no more than a leak in the box with an 18 inch driver in that big of a box. Josh tested it in a box just over 4 ft and he said it will bottom if not being driven correctly. Your box is going to be just a sealed or IB design at that point. 1000 watts might just push it out of the box on a burst. But, again, I could be wrong.
post #122 of 302
Thread Starter 
Quote:
It's not that the box won't work, it's that it is unlikely to be demonstrably/significantly better than the same driver in a sealed box of the same or bit smaller size

Maybe I'm trying to read too much into Mark's responses (but that's all I can really do since he's a busy guy) but this quote says to me the design will work fine, he just doesn't see much benefit to it.

If that is the case I'm happy to let this conversation end. All I was after is confirmation or denial of the validity of the simulations. I think the simulations are correct, I think this quote says Mark says so too.

The benefit of such a design is a completely different topic. If you desire ultra low tuning there is clear benefit, if you don't there is none whatsoever.
post #123 of 302
Thread Starter 
Quote:
Originally Posted by robertcharles View Post

But, again, I could be wrong.

All the simulations posted by everyone say you are wrong (even if the people that posted them don't necessarily agree with me).

I could be wrong too but I'm pretty sure I'm not. If there is a problem anywhere it's not reflected in currently available simulation software.
post #124 of 302
No, what he is telling you is that the port won't make any more difference than if the box was blue or green.He is saying it will work and the port will just be decoration.
post #125 of 302
So you are saying the 18 will take 1000 watts full tilt with no HPF with Bass I love you in a 24 foot box. I asked you to model it sealed and see if it will work, If you have and the sealed works, then fine, but if the driver unloads, then it will do the same in your-I mean my ported box
post #126 of 302
Thread Starter 
I seriously doubt that's what he meant. The simulations are not wrong as far as I can tell.
post #127 of 302
I would like you to post the actual numbers you used for the drivers so I can plug them in myself. Can you post the winisd parameter input page. I want to use your exact driver numbers and units on the sides ie mm instead of inches and so on. Ok
post #128 of 302
I am telling you that is exactly what he meant
post #129 of 302
the volume of air is tremendous at tuning, do you agree?
post #130 of 302
the numbers?

I have winisd now and I will run the simulation with your numbers and see what I get, If you do not mind?
post #131 of 302
I really think you should be helping me more than I am trying to help you. I want this free lunch as bad as you do. If you prove your point, you are the new KING if not we find out what the problem is and help each other out. No harm no foul. I am ready to plug away, and it could be as simple as a small misread. John's numbers did not match yours from what I remember and he has been doing this modeling for quite some time.
post #132 of 302
what order are you entering the data? what alignment did you use?
post #133 of 302
I just modeled it and you are wrong. Period. I have the graphs and I will tell you exactly how I modeled it and if you show me what you did I will show you where you screwed up
post #134 of 302
Thread Starter 
Quote:
Originally Posted by robertcharles View Post

If you prove your point, you are the new KING

NO!!! It just means I can operate a simulator competently, nothing more, nothing less.

I redid the same type of sealed vs ported head to head simulation Ricci did. I changed power input to 675 watts (as I explained earlier the WinISD graphs I posted were past xmax due to power matching with the previous software which simulates RMS deflection.)

The specs are straight from the manufacturer's data page. The boxes are both 700 liters, the ported one is tuned to 1.8 hz with a 1.85 inch diameter port.



If you simulate at the same power level (as shown) the sealed box can't go lower than 8 hz before hitting the red line. This is not fair since the ported box doesn't hit that excursion until below 2 hz.

If you reduce the power to the sealed box so it can handle 3 or even 5 hz within xmax limitations you get about an extra 2 or 3 db from the ported box across the entire passband in addition to the small gains shown here.


So... just as expected.
post #135 of 302
Thread Starter 
Quote:
Originally Posted by robertcharles View Post

I just modeled it and you are wrong. Period. I have the graphs and I will tell you exactly how I modeled it and if you show me what you did I will show you where you screwed up

From the questions you are asking it sounds like you have never used WinISD before. I modelled it too, see results above. Exactly what I said in the first place.
post #136 of 302
No, on the contrary, you seem to be wrong. I am going over everything. I have two graphs that almost resemble each other with the ported seeing the low dB gain that has been talked about. But the cone is going crazy at 10 Hertz or so and again down lower. My graphs look like I expected. When I post them, you and everyone else can see. I do not believe you wont go step by step with me but I figured as much. I am a scientist by trade and repeating an experiment is how you find the answers. No repeat no guaranteed outcome., and I will not believe your findings. I must be able to replicate it for it to be . So, continue to make fun, but you are wrong or I am, but my graphs look like what everyone else sees in their heads
post #137 of 302
Thread Starter 


Same simulation as above with power reduced to 400 watts to the sealed box (675 to the ported) so the sealed box can hit 3 hz within xmax.
post #138 of 302
post #139 of 302
If you are so sure I am wrong then lets go step by step through winisd and check values and units. Ok
post #140 of 302
Thread Starter 
Quote:
Originally Posted by robertcharles View Post

I do not believe you wont go step by step with me but I figured as much.

Is that unexpected? You made 40 posts last night, all saying the same thing. I answered all of them and then you deleted all of it. You are not exhibiting any technical knowledge and I don't have time to do this with you. I'm sorry but I'm not going to respond to you anymore since there's no benefit to either of us.

BTW, I checked your WinISD model and you entered almost every single thing wrong. I don't know if you entered driver specs right or not, but besides the 700 liter part everything is wrong. The tuning is wrong, port length is wrong, power input is wrong. This is what I'm talking about - either you don't understand what's going on or you are not paying attention.

Now despite all your errors it's still reasonably close and it still backs up everything I've said so far. Sounds like you didn't expect the graph to look like that despite the fact that several people including myself have posted graphs that look very close to that (despite your input errors), so again it appears that you don't understand what's going on or are simply not paying attention.
Edited by diy speaker guy - 12/10/12 at 7:51pm
post #141 of 302
Well, you are wrong. I just posted the correct model. It shows little improvement with a port and the excursions are in the stratosphere as well as the port velocities. John was right. If you will not go step by step and compare notes, you are afraid to be proven wrong. I will gladly show you my procedure and let you do it for yourself. I know it worked. I think you enterd some of your info with the incorrect units inches instead of cm or something, but to not let us test it for ourselves leads me to believe you do not trust your procedure. Take a look at my cabinets, they work, but they do what the simulations said and it took more than one tiem to enter the driver parameters to get the correct results. You did not design the software, so what makes you know how to enter the numbers so correctly


http://redspade-audio.blogspot.com/2010/06/winisd-entering-new-driver-data.html


Try this and make sure your number are correct and the units. I bet you are wrong.
post #142 of 302
Remember when you asked John about Le, well here is your answer as to why, and it will address alll the other mistakes you are probably making.
post #143 of 302
Thread Starter 
Quote:
Originally Posted by robertcharles View Post

http://redspade-audio.blogspot.com/2010/06/winisd-entering-new-driver-data.html
Try this and make sure your number are correct and the units. I bet you are wrong.

Are you kidding me? This is downright insulting and yet funny at the same time.

Thanks though, I needed a really good reason to step away from the computer and let this go.
post #144 of 302
This is exactly what I expected. The woofer is coming out of the box at 10 Hertz and then again down low. I am going over my graphs to make sure they are right, but I do not see why you think my graphs look like yours. Octaves aprts. Are you kidding me?

Your graphs are going down to almost 1 Hertz and below at 70 dB- very different indeedWhat do you not see?
post #145 of 302
win isd graphs all of them.zip 12k .zip file

This is all the graphs I got from the numbers. They are showing what everyone is telling you. No real gain. Possible damage. Extreme port velocity. I do not see my graphs looking like yours. In order for you to be correct, someone should be able to duplicate it as you have, or to duplicate mine if I am correct. You do not want to go step by step, so I can only say this is what I have and until I can compare results and procedure no correct just different outcomes using the same drivers.
Edited by robertcharles - 12/10/12 at 8:37pm
post #146 of 302
Quote:
Originally Posted by diy speaker guy View Post



If you reduce the power to the sealed box so it can handle 3 or even 5 hz within xmax limitations you get about an extra 2 or 3 db from the ported box across the entire passband in addition to the small gains shown here.

So... just as expected.

Exactly.

Now look at your first spl curve. Which is the correct one for the comparison. Any significant gains are below 10Hz. You get about 2dB at 5Hz. Check the port airspeed chart though and it shows air speeds of about 20ms from 4Hz down which will be well into compression and noise from the port. At 5 Hz it is 14.5 ms which I would not count on being within the capabilities of the port either. What is left is the tiny little gains above that point. This is what some of us have been trying to say. At the end of the day it's just not worth it. You could reduce the enclosure volume of the sealed enclosures to limit deep bass excursion and use a more powerful amplifier to gain some peak output in the bass ranges that matter far more.

Basically you have a huge vented cabinet that has peak output similar to a much smaller sealed sub above the 10Hz range, with very small advantage down to 5Hz and likely none at all below that point due to immense port compression. It just doesn't amount to any advantage that will make improvement in the experience IMHO.

This is what I have been trying to get across. Yes a port tuned that low still acts like a port. No surprise there. Tuning so low with such a small diameter doesn't really bring much to the party though and you are using a huge enclosure to boot. You would have something far more impressive with such big cabs by tuning about 2.5 to 3 octaves higher and getting a bigger port to provide some output where it matters. For example a GH cab produces the output of 1.5-3 of these cabs over most of its range. Otherwise you can produce basically the same performance from a much smaller sealed system comprising a couple of 4 or 5 ft boxes.
post #147 of 302
Thread Starter 
Wow, we are so so close to being in complete agreement now. I agree with everything in your entire post (for the most part - nothing worth arguing anymore in anything not quoted below. To be clear though, a lot of your post is a subjective opinion on whether it's worth it or not that I'm not going to argue).
Quote:
Originally Posted by Ricci View Post


Now look at your first spl curve. Which is the correct one for the comparison.

That's not fair. The ported box can go way lower within xmax. You can't compare them at equal power, you need to compare them at xmax limited max spl at the lowest frequency of interest. That's the only fair comparison. Post 137 shows a much more fair comparison based on excursion although I admit the sealed box doesn't really need to go quite that low so you could apply 50 or 100 more watts to be a little more fair. But comparing equal power is not fair.
Quote:
You could reduce the enclosure volume of the sealed enclosures to limit deep bass excursion and use a more powerful amplifier to gain some peak output in the bass ranges that matter far more.

Yes, but then it's an even more unfair comparison. If the goal as stated is lowest frequency possible at highest spl with the lowest possible power requirements this suggestion is going in the opposite direction. Now I fully agree, people with fat wallets might not see much benefit to the ported design vs sealed (even as shown in post 137) but it is a clear gain that is there for the taking if you want it.
Quote:
air speeds of about 20ms from 4Hz down which will be well into compression and noise from the port.

Not so sure about this. I think 20 m/s will be pretty chuff free with a decent roundover. It's well into core turbulence at that point but I'm not convinced it will be audibly objectionable until you get a bit higher velocity. Even so, there's not much content that low and lower so it's hardly an issue. Most people are comfortable designing for 17 m/s worst case scenario so I don't see 20 m/s at 4 hz as a huge problem.

Even these small considerations are nothing worth arguing over, I'm just so happy this is finally over.
Edited by diy speaker guy - 12/10/12 at 9:25pm
post #148 of 302
Quote:
Originally Posted by diy speaker guy View Post

Thank you for this.
In this case the primary motivation was simply to model this driver to see what it takes to extract it's full potential within the rated power handling spec. It takes a very low tuning to do this. Like I said, I'm not married to the 2 hz idea and probably won't build this anyway but I'm still interested in the concept. And the concept is sound, as I've shown here. I'm satisfied with that and I don't really care that I haven't convinced anyone. It wasn't hard to do though, since the only arguement put forth is that all the software is all wrong.
The point of this concept was to use only the top half of the port resonance, the other half (the problematic half) was ALWAYS supposed to be buried in signal chain rolloff ON PURPOSE. This idea was not ever about playing 2 hz tones at full volume, or ever even "hearing" 2 hz at all. It's not meant to be providing effective output until around 5 hz or higher, where there is actually some content in some material. The concept uses a very small port but buries the consequences of such so low that it doesn't matter. It won't chuff because it won't ever see the frequencies that might cause chuffing.
So I'll leave you guys (and this topic) alone now. Thanks anyway.

I didn't say anything about the software being wrong. Software crunches math based on the user's input. My point was as basic as it gets; the input is where the flaw resides.

You posted a sim, then you posted another sim. The 2 sims were radically different, but no matter because, although you mention signal chain roll off in passing, as though it's an irrelevant piece of data (as most do), it actually is the whole bowl of wax.

Taking loopback measurements of the analog SW output of a popular AVR, a popular PEQ and a popular amplifier, summing the additive effect and applying that signal chain data to your sims shows a far more accurate picture:



This is a typical result using popular signal chain hardware. It can easily be far worse depending on the hardware in the chain, but it can also be far better. In fact, more attention to the signal chain can improve performance below 10 Hz magnitudes greater than building a huge box and sticking a long pipe in it.

What I'm saying is that you either raise the tune to see a real advantage before the signal chain roll off (as the seasoned vets of that sort of alignment have repeatedly said in this thread) or focus more effort improving your signal chain fidelity. Both avenues will yield far better results than discussing a grossly flawed computer simulation.

Also, I mentioned it in my post that incorrect edicts about content should be a thing of the ancient past, but still persist and cause a huge and unnecessary waste of virtual ink. You appeared to agree, but have posted that 'no content ever contains...', etc... Of course, that's just not true:



This is one of many examples that have been around for quite a few years. I'm mentioning it here because it's pertinent info and no one should be misled by posts to the contrary. IF anyone decides to get serious about signal chain fidelity, thinking this content doesn't exist will end in destroyed hardware.
post #149 of 302
Fair...forcing the sealed system to be the same in every way when it makes no sense for them to be is fair? We are still talking about the same drivers. You would probably save enough money just on enclosure materials to make up for the cost of more power. Power is very cheap these days.

Objective vs subjective...How about this. The vented system offers an average of 1dB increase in displacement limited output over the 5-10 Hz octave and less than that above 10Hz when compared with a sealed system 1/3rd the size. This is assuming that the 2" vent is capable of uncompressed output at the port speeds produced at those drive levels and frequencies. Doubtful IMO.

Cut the graphs at 7Hz and look at the differences. All of this back and forth is over a single dB which some of us are not sure that the port will actually be able to provide.
post #150 of 302
And that is why I have a low frequency HPF. with the rest of the levels high, that ULF causes excursion to skyrocket. It IS there.
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