Hi chrapladm,
Looking @ Post #133, that simulation seems to work better as Nd (driver @ the throat end) Try w/ S1=420, and Vrc=100.
Hi Brian,
I just mentioned the W-horn as an example of a symmetrical fold, not to copy it. It should load the driver more evenly than a simple offset driver, and I prefer the looks of the 90 degree bends...it does get big though.
Regards,
Looking @ Post #133, that simulation seems to work better as Nd (driver @ the throat end) Try w/ S1=420, and Vrc=100.
Hi Brian,
I just mentioned the W-horn as an example of a symmetrical fold, not to copy it. It should load the driver more evenly than a simple offset driver, and I prefer the looks of the 90 degree bends...it does get big though.
Regards,
I'm not going to comment on subject reviews found on the internet, so I clipped that part of the quote right out.
What I will comment on is the reactance annulling. A requirement of true reactance annulling is equalizing the pressure on both sides of the cone.
I made a tapped horn once with the Tang Band w6-1139si, it was one of the first batches of this driver made and fs was almost 10 hz higher than published specs even after a brutal break in and even when measuring the driver immediately after being exercised.
The fs was 46 hz IIRC, I can check on that if necessary.
This driver is pretty well known to have parameters that work really well in tapped horns.
I made a tapped horn for it that was almost exactly a scaled down TH_Spud. It had the same undamped response when simulated, and I put some damping in the throat and mouth. It's measured response curve was very similar to the TH_SPUD.
The unstuffed sim shows tuning at about 26 hz.
Unfortunately I can't measure pressure on the driver but I can show what it simulated at.
An externally hosted image should be here but it was not working when we last tested it.
That's a 46 hz fs driver very much like the one you used in the SPUD in a 26 hz horn that's very much like the SPUD. I don't think there's any way you could tweak the driver or the horn to provide true reactance annulling.
If you give up the equalized pressure requirement of reactance annulling then the term is pretty useless, just about anything can be reactance annulled.
If you can show any sim of one of your products or just a random tapped horn that has equalized pressure on both sides of the cone I'd like to see it. You don't have to post any details, just the model of the horn and the graph I've shown.
Thanks for that. Gives me an idea of what sizes will be. My mouth will be about 3800 and horn length is about 350ish. Will try and export txt into sketchup and going to try and use one of the links TB46 or Xoc1 posted for CAD attempt. Probably have to view some youtube clips to get a jist of how to do it all.
Thanks for commenting Tom. Always insightful to hear comments from you. I wish I understood annulling better to full grasp what your talking about.
Thanks will have a look in a few.
Curious about the same. Woulld be good to hear the difference between Keeles horn and a few other designs out there in the same BW. But that will have to be for another project.Maybe your 18's will work in this cabinet Brian.
Your suggestion makes the cabinet 40 liters smaller and has a better high end response. It is very close to the same response I have originally in a smaller cabinet. It makes sense to me why it would have less roll off higher in frequency, I just dont quite understand the difference in alignments when you finally fold the horn. It seems like the Nd would be very similar to an Od when built with S1 = 1 for Od.
Either way huge thanks. Saved me some room and 1 less volt to hit Xmax.
Obviously that's not my graph.
What was your input power to the Othorn in your max SPL graph? When driver excursion is the limiting factor and input power is equal it looks like this below which I posted days ago. Yours obviously has a lot more power for the FLH in a minimum excursion zone in between 2 excursion peaks. The low pass filter you used up top reduced driver excursion by 50% at the upper excursion peak. You effectively placed an EQ boost at a minimum impedance, minimum excursion zone and then used greatly increased voltage in order to get the 2dB advantage between 35-42Hz. The Othorn has better voltage sensitivity in that region. This "advantage" is being eked out by what amounts to EQ and a much bigger amplifier needed for only that sliver of bandwidth.
Clearly I was discussing the LPF you added later. It's not the LPF that I disagree with, but thinking a 200-250v amplifier is appropriate is, which is in turn being used to generate the very small advantage you have touted between a small bandwith from 35-42Hz or thereabout. The driver runs out of excursion at 165v at 50Hz. It handles less voltage than that below 35Hz. EQ does not change this. 200v into the min impedance of the cab is a LOT of power. It's a zone of min impedance and min excursion too. How do you keep damaging amounts of power from the driver? High and low pass filters won't be enough if it gets used like a lot of cabs do. 50Hz is smack in the middle of the bandwidth it would handle and will be an area of heavy content.
I would not operate that FLH on an amp capable of 250v with your filters and a limiter set at 250v. Simple as that to me. Limiters set at 165v maybe. That being the case I do not feel that the comparison is valid. YMMV.
Funny because I could say the same of you. How many times have you said I was wrong or mistaken or implied I was stupid in your last few posts? If we could at least agree on what data we are discussing that would be one thing, but you have taken comments I made about data in my graphs, setup the way I believe they should be looked at for a valid comparison and then implied that I'm talking about yours which will have different input powers, filters, programs, etc...I STILL don't agree with the way your sims are setup.
You are taking a lot of my comments out of context. This is why this conversation is going no where. I made the 8kw comment while looking at my graphs not yours and with the filters I had in place not yours. Clearly that was the case? It may not be 8kw but it sure as hell isn't only 3800w either. Should be closer to 6500 or so around 70Hz after looking at it again. I only spent about 10min looking at things before running out the door and was ball parking it. I added a 90Hz 4th order cause that's a typical crossover point for many. Later you added a 50Hz 12dB low pass to reduce the entire upper end response and reducing the excursion at 50Hz some 50% ,which I had not done. This was when you switched to Akabak I believe. Then you have made a big deal about it over a few posts like I was discussing your graph when I made the comments! That is certainly not fair play. The point is the amplifier reserves needed are much bigger to realize its maximums.
It's almost impossible to build a flh with the driver firing into S1. Not completely impossible but very difficult to fold up like that. I don't think I've ever seen one but technically it is possible so there might be real world examples. So it's best to stick to OD, like Sine's drawing (and most if not all flh drawings) show unless you are up for a real folding challenge.
9999, same as the flh. Although that number means nothing once the filters are added. Max out power and you see the excursion limits.
You can call the lpf eq if you want, and you can even replace the lpf with eq, but either way you have to cut the rising response, you can't use the cab with the lpf you showed in your graphs without additional processing. Whether you use eq or a lpf to accomplish that, it's going to dramatically reduce input power. That is NOT cheating, it's just the way it is.
An externally hosted image should be here but it was not working when we last tested it.
That's the Akabak power graph again, flh on top at 165 V, Othorn on the bottom at 120. Those voltages are the SIM INPUTS not what the driver sees due to the required filters. Both of these cabs have the required filters that they need to protect them below tuning and to give a flat response through the passband. You selected ALL the filters except the lpf on the flh, I changed it because it didn't get rid of the rising response. Whether you use eq or a lpf to get rid of the rising response it's not an option, it has to be done, and the resulting power consumed by the driver will be the same either way.
The flh consumes 3800 watts and the Othorn consumes 3300 at their respective peaks, but over the entire bandwidth the flh is consuming far less power. The flh consumes less power and will see less power compression.
Forget about 250 V for now, this is at 165 for the flh and 120 for the Othorn. At this level the cabs have almost identical performance, same bandwidth, same spl level but the flh is taking a LOT less power to do it. More voltage yes. But less power.
If we can't agree on that much this is hopeless. This isn't something I'm making up, it's an Akabak analysis, and all the filters were specified by you expect the one required to level the rising response in the flh, which is an absolute requirement to run the cab properly.
Here's the response graph again.
An externally hosted image should be here but it was not working when we last tested it.
Unless you are going to run the cab with the rising response not notched down these filters are appropriate. These sims are set up exactly the way you specified, you called the voltage level and all the filters except the flh lpf, so you can't say they aren't set up right, I simmed exactly what you said to sim.
Regardless, it's the hpf that takes most of the power away from the main spike, not the lpf. In the 165 V sim power peaks at 3800 watts into the flh because of the high pass filter you specified. You can see it right in the graph above.
Let's completely forget about simulating at anything past 165 V. These graphs show the power levels and filters you specified (with the exception of the flh lpf) and Akabak says the flh peaks at 3800 watts. As far as I can tell that is solid fact and cannot be disputed.
I say the flh has more left in the tank, you say it doesn't. That part doesn't matter, we can agree to disagree, but on everything else in this post I don't see any wiggle room at all.
That's the problem, THIS is the sim you were talking about, you specified the filters (except for the required response leveling lpf) and the power level. I just put it into Akabak so I could see the filters AND the power level at the same time. You can't do that in Hornresp and you said you don't have Akabak right now, so there's no possible way you could be looking at the driver power with the filters in place. You can look at power WITHOUT the filters in place, and that will show 8000 watts, but with the hpf you specified in place it's 3800 watts as I've shown here, and also several posts back.
You say showing an absolutely required lpf in my sims is not fair play because you didn't include it in your sims, but if it's absolutely required it has to be included.
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Hi chrapladm,
Just a few more thoughts. Let me preface this by saying that I have no experience with todays high power, high excursion subwoofers. I just don't like very high throat compression ratio in general, so I increased the S2 value in your OD-FLH, and made a few more changes, see the attached Export. The I reduced the volume by using Exp (see below).
I also played around a little w/ the vented rear chamber feature.
A quick note to using Par v. Exp: when you do an overall expansion it makes sense to use Exp, and when you fold the horn you use the cross-sectional areas from the Exp horn at the turns. The individual horn sections may well end up being Par, but the overall expansion of the horn will be Exp. Might reduce the volume, and give you a better response.
It will take a few iterations to arrive at a decent simulation/drawing. Then there is still that pesky woodworking problem. After that you can measure to see how close you got. It's a real challenge.
Regards,
Just a few more thoughts. Let me preface this by saying that I have no experience with todays high power, high excursion subwoofers. I just don't like very high throat compression ratio in general, so I increased the S2 value in your OD-FLH, and made a few more changes, see the attached Export. The I reduced the volume by using Exp (see below).
I also played around a little w/ the vented rear chamber feature.
A quick note to using Par v. Exp: when you do an overall expansion it makes sense to use Exp, and when you fold the horn you use the cross-sectional areas from the Exp horn at the turns. The individual horn sections may well end up being Par, but the overall expansion of the horn will be Exp. Might reduce the volume, and give you a better response.
It will take a few iterations to arrive at a decent simulation/drawing. Then there is still that pesky woodworking problem. After that you can measure to see how close you got. It's a real challenge.
Regards,
Attachments
Hi just a guy,
Post #146: "It's almost impossible to build a flh with the driver firing into S1..."
In this thread: Posts #4 and #132 are both firing quite nicely into S1. It's not uncommon for horns to be "end-loaded". Even some offset driver horns actually have the driver(s) loaded into a form of throat chamber that then pipes into the horn proper.
Regards,
Post #146: "It's almost impossible to build a flh with the driver firing into S1..."
In this thread: Posts #4 and #132 are both firing quite nicely into S1. It's not uncommon for horns to be "end-loaded". Even some offset driver horns actually have the driver(s) loaded into a form of throat chamber that then pipes into the horn proper.
Regards,
True, you got me.
In each of those cases however there's issues.
In post 4 there's a bunch of wasted space around the first part of the horn, and a bunch of extra wood required to make that first section of the flare. There are ways to lay it out to avoid this and still be Nd, but it would require quite a bit of planning.
In post 132 (and all other symmetrical layouts) a lot of extra wood is required to lay out symmetrically. Weltersys comments on this often. Extra wood takes extra space and causes extra weight. Symmetrical layouts look fantastic but are a bit wasteful. When size and weight are not a concern I like them a lot.
But yeah, I was wrong, I've seen two Nd flhs in this thread alone, and numerous other symmetrical layout flhs. Not sure why that didn't register.
Either way, Sine's picture is how most flhs are configured in the first part of the flare and this saves a lot of space and extra wood. It also allows for a flare rate change at S2 if you butt the throat and last bend of the flare side by side in the layout, so you can get that triangle shaped flare at the beginning of the horn like a lot of Danley's designs like the TH_SPUD have. (Not that either of the layout styles in post 4 or 132 couldn't also have a flare rate change at S2, but it's easily accomplished with an Od layout.) That little triangle isn't doing anything useful in the last bend and in fact a lot of people block it off with a relector anyway, but it could be usefully used in the throat area. I think you mentioned this triangle throat shape earlier in this thread.
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Bjørn Kolbrek summed up the concept very nicely some time ago:
"Regarding reactance anulling, the idea is to make the negative reactance of the rear chamber equal to the positive mass reactance of the horn. This way they largely cancel, and the load seen by the driver is mainly resistive in the working range. It is first described by A.L. Thuras in US patent # 2037185".
I dont quite fully understand the differences of Exp vs Par but I am trying to understand. IN your simulation example the tuning is much higher and would need Hpass at 33hz if pushing enough voltage to hit Xmax just below the tune. My exaple would need a 28hz Hpass.
BUT saying that, your design with the smaller chamber with 127v to hit Xmax just below tune never allows the drive to go past 25mm. SO while being higher tune and a higher Hpass it has the same SPL at 30hz. But below about there it goes to my larger design. So maybe I can just extend the horn in yours and match the low end. Or just go between the two for extension because above 30hz your horn excels over mine quite a bit, like 4db down near tune to about 3db higher up.
I can adjust my mouth to your 4000 spec you stated earlier. Not sure the exact number I would have to look. But if it is needed I can adjust it. Although now I need to look hard at TB46's sim because it seems to have more DB higher up. BUT it does take 20v more to do that also. SO another revision perhaps with more extension will get the voltage down a bit.
Post four was what I found also when I was finally figuring out it could be done. And then I looked at Keeles more.
Another question I am curious about is, does the TH offer more cooling to the motor verse the FLH?
I would imagine it does because of the turbulence from the horn itself and being exposed to the air. Where as the FLH is fully enclosed.
Just curious is all when throwing high voltage at these things. And this is mainly for my own knowledge. Like I said before I wont have an amp that is going to be able to push a pair of these monsters. Design for maximum output while keeping most things in "safe," boundaries and then use what ever amp I can. So dual 127v per channels wont happen anytime soon.
Yes, the driver in a tapped horn is basically sitting in a fanned duct. You would have to take temps to find out how much this benefits compared to just having the cone alone fan the motor as is the case is a sealed chamber flh. I don't have any data on this. The only way a flh could benefit from this same type of thing is if you had a big throat chamber with the driver motor inside the throat chamber. In post 4, if the throat chamber was opened up a bit wider you could stick the motor inside the throat chamber and the motor would be in the horn, not in the sealed rear chamber. But like I said I have no idea how much this would benefit, maybe a lot maybe not. Probably at least some.
As I showed a couple of times now, once you knock down the flh's rising response with eq or lpf, the only area that sees high power is a narrow band of frequencies right above tuning. It was 30 - 43 hz in the example I just showed with the Akabak sims. (That example was Othorn vs the 560 liter tapped horn from earlier in the thread but I can sim power demands for whatever design you end up with if you want.) From 43 hz and up in that example the driver only sees less than 1/2 the power an equivalent tapped horn would because the lpf (or eq or whatever you use to flatten the rising response) limits the power. On average the flh consumes way less power so it will have way less issues with heat. The sealed chamber vs fanned duct is the other half of the story and as I said I don't have any data on that part.
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Ya I figured as much. I am not really worried about the voltage I will be putting to this driver. I am also happy that the BC does have a 6" VC. I have been pretty hard on much smaller VC's and been fine. PLUS I will probably leave that subject for another project.
Funny thing for me is that after I changed a few parameters in TB46 design to get it to match the low end of the design I had the horns then become almost the same exact size.
TB46's with my changes is now 680l roughly with an 85l chamber. Mine is roughly 680 also with a 150l chamber. Takes 107v to hit 14mm Xmax and TB46's with my changes take 113v.
They both have different Hpass to keep the low end from going over 16mm. After looking at that they are almost identical with my design maybe having a slight edge by maybe a 1/2db or so below Hpass. So not much of a difference.
Tuned a little higher as it originally was TB46 design had about 4db's more SPL at 33hz and up. Amazing how big the box grows to have a little bit of extra extension.
Here is the comparison. This is with 127v vs my 107 with more extension.
While I am sure none of this is amazing to anyone here I just thought it was eye opening to me. To have a little bit of extension you need to grow the cabinet by about 100 liters. WOW
Funny thing for me is that after I changed a few parameters in TB46 design to get it to match the low end of the design I had the horns then become almost the same exact size.
TB46's with my changes is now 680l roughly with an 85l chamber. Mine is roughly 680 also with a 150l chamber. Takes 107v to hit 14mm Xmax and TB46's with my changes take 113v.
They both have different Hpass to keep the low end from going over 16mm. After looking at that they are almost identical with my design maybe having a slight edge by maybe a 1/2db or so below Hpass. So not much of a difference.
Tuned a little higher as it originally was TB46 design had about 4db's more SPL at 33hz and up. Amazing how big the box grows to have a little bit of extra extension.
Here is the comparison. This is with 127v vs my 107 with more extension.
While I am sure none of this is amazing to anyone here I just thought it was eye opening to me. To have a little bit of extension you need to grow the cabinet by about 100 liters. WOW
You can tune lower and make the box smaller too, if you wanted to do that. It's all about the flare shape. Making it less flared (morphing to a straight, constant csa transmission line) will allow for lower tuning and smaller size while also killing off the rising response. Try it, leave everything the same but decrease S3, S4 and S5 incrementally. Box size goes down, tuning goes lower, rising response gets killed off, and max spl goes down.
Size dictates max potential spl, shape dictates tuning and response curve shape.
Size dictates max potential spl, shape dictates tuning and response curve shape.
Ah ok. Would decreasing those also require more voltage to hit Xmax?
I am liking the SPL and dont want that to go down any. Its just when I saw his design compared to mine it was much more SPL. Then when comparing apples to apples, so to speak, it becoms about the same SPL/size when they have similar response.
I am liking the SPL and dont want that to go down any. Its just when I saw his design compared to mine it was much more SPL. Then when comparing apples to apples, so to speak, it becoms about the same SPL/size when they have similar response.
To Par or not to Par?
Hi chrapladm,
Wayne Parham did a lot of research pertaining to cooling when he designed his 12Pi basshorn subwoofer:
Pi Speakers - Push/Pull Basshorn Subs
As to Par v. Exp, I just wanted to point out, that you should not feel that you have to simulate in one or the other. AkAbak only gives you Con, but a lot more sections. Often Exp will give you better results in a bass horns, and the final flare rate will come from the wood, not from the simulation. So, simulate, then draw it out, convert your drawing back to a simulation (now you do watch carefully that you get it as close as possible, e.g.: individual section as Par even if the whole horn flare from throat to mouth is Exp). Then you file around on your simulation, and draw again....
Also keep in mind that you are designing an acoustically sub-optimum horn because of size restraints.
Regards,
Hi chrapladm,
Wayne Parham did a lot of research pertaining to cooling when he designed his 12Pi basshorn subwoofer:
Pi Speakers - Push/Pull Basshorn Subs
As to Par v. Exp, I just wanted to point out, that you should not feel that you have to simulate in one or the other. AkAbak only gives you Con, but a lot more sections. Often Exp will give you better results in a bass horns, and the final flare rate will come from the wood, not from the simulation. So, simulate, then draw it out, convert your drawing back to a simulation (now you do watch carefully that you get it as close as possible, e.g.: individual section as Par even if the whole horn flare from throat to mouth is Exp). Then you file around on your simulation, and draw again....
Also keep in mind that you are designing an acoustically sub-optimum horn because of size restraints.
Regards,
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