Reviving the NOTHORN, a LTD02 design - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 25 Old 01-05-2019, 03:30 PM - Thread Starter
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Reviving the NOTHORN, a LTD02 design

Late in 2015, @LTD02 designed a lower tuned, front loaded horn as an alternative to the LOWARHORN using a less expensive Stereo Integrity 18HT subwoofer. There was some additional discussion about the new design here. Recently i took a second look at LTD's design and tried my hand at modeling the horn with a few of the midrange B&C 21" subwoofers. It turned out that the 21DS115-4 modeled even better than the original driver in John's design. I have included the original Hornresp parameters as well as the parameters I used for the B&C driver along with their frequency response plots. The third plot is the comparison of the B&C vs. the SI driver (the B&C driver is the very faint grey line in the plot).


The original simulation was done at a time when the importance of inductance compensation was not fully understood. I'm wondering how these drivers would simulate now with appropriate inductance compensation (unfortunately the degree of compensation is beyond my level of understanding). Furthermore, I'm wondering if the DS115-4 is the optimum driver for this design given a max value of $600 and appropriate inductance compensation. I modeled the new LaVoce driver at parts Express, but it's performance was substantially worse.

Thanks,
Mike
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post #2 of 25 Old 01-05-2019, 03:37 PM
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I know nothing about any of the horns but they definitely interested me. Good luck bringing this back to life. I look forward to seeing your progress.
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post #3 of 25 Old 01-05-2019, 03:42 PM
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Finding a 21" driver with better price to performance ratio than the 21ds115 is hard.
Seeing how the graph is flatter and outputs more SPL overall compared to the SI shows how beastly those B&C's are.
Anyways, what's the tuning of that horn?

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post #4 of 25 Old 01-05-2019, 03:44 PM
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I, like you, am missing the understanding of the science of it all. I am looking forward to seeing what all you can glean from this project.


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post #5 of 25 Old 01-05-2019, 03:47 PM
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isn't this what eventually became the submaximus? and then through aarose's building and measuring sparked the flurry of inductance adjustment techniques for making simulations more accurate for these modern super beefy drivers......if memory serves
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post #6 of 25 Old 01-05-2019, 08:27 PM
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I think so. Max V3 is the latest version of this horn. Still haven't seen a great measurement of it with the DS21 though. Considering it's massive size it's understandable why nobody wants to drag it outside. Asarose did but I think he used the uxl.

It's so big. Like an actual regular sized refrigerator. We joke about fridge sized subs, but this one really is that big.
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post #7 of 25 Old 01-05-2019, 09:31 PM
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How many of these were ever built??

Horns are great if space is not a concern but budget is. I think this horn was tuned a little bit lower than the Submax horn. But again another great design for some fun.
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post #8 of 25 Old 01-05-2019, 11:10 PM - Thread Starter
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The tune is in the 14-15Hz range. A search of the forum does not reveal any of these were ever built.

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post #9 of 25 Old 01-06-2019, 02:51 AM
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Also not sure this will matter but I would not use a cheap driver in 21" size in the horn. 1600/330 is on the high side for compression ratio. 1120/330 is easier and definitely fine with almost any 18 cone out there.
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post #10 of 25 Old 01-06-2019, 05:25 AM
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Quote:
Originally Posted by Samps View Post
I think so. Max V3 is the latest version of this horn. Still haven't seen a great measurement of it with the DS21 though. Considering it's massive size it's understandable why nobody wants to drag it outside. Asarose did but I think he used the uxl.

It's so big. Like an actual regular sized refrigerator. We joke about fridge sized subs, but this one really is that big.
since 4 were just built and loaded with b&c 21s, if hd0823 is within an hour or so of Chicago I would volunteer to visit and measure them. he just posted a photo with a friend standing next to one, and its taller than the friend.

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Originally Posted by chrapladm View Post
How many of these were ever built??

Horns are great if space is not a concern but budget is. I think this horn was tuned a little bit lower than the Submax horn. But again another great design for some fun.
if it is the pre-submaximus 1. in its current iteration...maybe 7 or 8. submax is tuned to about 17hz, so im pretty sure this was the first iteration of what would become that horn.
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post #11 of 25 Old 01-06-2019, 05:34 AM
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Originally Posted by VegaMan View Post
since 4 were just built and loaded with b&c 21s, if hd0823 is within an hour or so of Chicago I would volunteer to visit and measure them. he just posted a photo with a friend standing next to one, and its taller than the friend.


if it is the pre-submaximus 1. in its current iteration...maybe 7 or 8. submax is tuned to about 17hz, so im pretty sure this was the first iteration of what would become that horn.
The Submax design has a 500 S2 so much less compression then the Nothorn sim from the first post. So if the Submax is what came of that first design then no need for this to be built. Well, unless you want to go a little wider and use dual 15's or the 21. LOL
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post #12 of 25 Old 01-06-2019, 06:25 AM
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I can't follow what is what here.

Can we get a rundown on what version we are talking about and the current design plans, tuning, drivers, etc?

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post #13 of 25 Old 01-06-2019, 06:43 AM
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Quote:
Originally Posted by chrapladm View Post
The Submax design has a 500 S2 so much less compression then the Nothorn sim from the first post. So if the Submax is what came of that first design then no need for this to be built. Well, unless you want to go a little wider and use dual 15's or the 21. LOL
still on the hunt for something fun to do with those alpines?
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post #14 of 25 Old 01-06-2019, 03:50 PM
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I built Max V3 outside, so all testing was done once I got it onto a re-enforced / resized HF dolly. pics in my thread
that achieved thanks to @kevings
but not without some "whoa there big boy"

who also assisted in turning Max on it's side for driver installation / sealing testing and then back again forthe hatch install / testing . and running the 50 foot 12 ga. from 6k inside the home
at about 350#, moving requires some planning and smooth surfaces, and a bodacious reefer dolly
at 80" tall, while not top heavy, commands respect

As i also built Max V2 (38 ft^3), according to @LTD02 , his opinion was that there wouldn't be much noticeable difference
if he were trying to deter me, perhaps,
after all how many huge boxes can 1 HT survive anyway . .

can't wait for the results from @hd0823 . .
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post #15 of 25 Old 01-07-2019, 09:04 PM
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awesome mike!

you'll want to model with the lossy inductance turned on for the ht-18 type driver. the ds21 will probably be somewhere in between turning on lossy inductance and not, but i'm not exactly sure which one would be closer. my guess is a little closer to the lossy inductance results.

lossy inductance can be turned on by double clicking on Le. it will turn red when turned on.

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post #16 of 25 Old 01-07-2019, 09:07 PM
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also, nd and od are different types of horns.

the one in the picture is an offset driver horn. "od"

another thing to keep and eye on is compression ratio. too low and you may tear up your driver cone.

2:1 is super conservative. 3:1 is typical. 4:1 or more may be possible with cones that are rugged. i probably would design for a slightly lower compression ratio (perhaps 3:1) and live with a little more "choppiness" in the frequency response than go too high and damage the driver.

compression ratio is cone area (sd) divided by S1 in a "nd" horn, and it is sd divided by S2 for an offset driver horn.

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post #17 of 25 Old 01-07-2019, 09:38 PM
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the inductance effect can be seen here.

something like this kind of magnetic braking occurs with voice coils and the pole piece in woofers.

in the video the result is 'weakened gravity'. in a woofer, the result is a 'weakened motor'.

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post #18 of 25 Old 01-07-2019, 10:08 PM
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The inductance "white paper" that came out is not physically or mathematically valid and should never be used, and the model should be removed from hornresp because it's not valid. It suffers from a fundamental flaw. It attempts to improve inductance modeling, an issue solely confined to the electrical portion of the impedance, by modifying the motional impedance. The technique apparently used was to screw around with model parameters until the simulated frequency response became closer to that which was measured. This involved, among other things, altering the BL product, which leads to incorrect simulation of displacement and sensitivity among other parameters. One of the signatories was someone who admitted to not understanding the math at all (making the error understandable), but unfortunately, another was a very well respected member of the community.

The correct way to deal with this problem is to use the new inductance model of hornresp and its associated spreadsheet.

Thorborg gives details about this inductance modeling here.
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Last edited by andyc56; 01-07-2019 at 10:19 PM.
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post #19 of 25 Old 01-08-2019, 11:25 AM
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Quote:
Originally Posted by LTD02 View Post
the inductance effect can be seen here.

something like this kind of magnetic braking occurs with voice coils and the pole piece in woofers.

in the video the result is 'weakened gravity'. in a woofer, the result is a 'weakened motor'.
That's some cool science at work there. Thanks for posting that!

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post #20 of 25 Old 01-08-2019, 12:36 PM
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+1 for the vid.
cool science, indeed . .

now, what about that V4 rumor . .?

Spoiler!
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post #21 of 25 Old 01-08-2019, 11:35 PM
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Quote:
Originally Posted by andyc56 View Post
That is a good article, however even that is STILL too oversimplified.

The problem with simulations is that you are trying to simulate a dynamic system with static parameters, and you don't even have all of the parameters that are effecting the system, such as: permeability and conductivity and distance to all materials in the motor.

You also don't know how well the motor can cool itself and how the various materials react with heat when given multiple kW...

Sim's also don't account for loss of motor force due to coil leaving the gap. You'd have to know the coil height and gap height, at a minimum.

If you want a truly accurate model, you have to quantify those, and apply the related math to the model. t/s isn't enough information!

The math that reality uses is fully-complete and all-encompassing, the math humans use is far incomplete.

Reality has no problem calculating the effects of your pet goat ramming your dust cap in the middle of a sweep or the effects of the lightning blast in your backyard, the software didn't account for that at-all...

I love how scientists make generalizations and simplifications in their models, and then wonder why it doesn't match reality.

Throughout grade school you were taught to neglect air resistance. Air resistance is very-real and non-neglectable. Among others... LOL

You can't model the universe if you don't even know where an electron "is" or if it is a "wave or a particle" or both at different times, based on observations or the lack thereof. LOL!

3-body insolvability problem, and the other unsolvable math\universe paradoxes etc etc etc... LOL!

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post #22 of 25 Old 01-12-2019, 11:34 AM
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Quote:
Originally Posted by andyc56 View Post
The inductance "white paper" that came out is not physically or mathematically valid and should never be used, and the model should be removed from hornresp because it's not valid. It suffers from a fundamental flaw. It attempts to improve inductance modeling, an issue solely confined to the electrical portion of the impedance, by modifying the motional impedance. The technique apparently used was to screw around with model parameters until the simulated frequency response became closer to that which was measured. This involved, among other things, altering the BL product, which leads to incorrect simulation of displacement and sensitivity among other parameters. One of the signatories was someone who admitted to not understanding the math at all (making the error understandable), but unfortunately, another was a very well respected member of the community.

The correct way to deal with this problem is to use the new inductance model of hornresp and its associated spreadsheet.

Thorborg gives details about this inductance modeling here.
in light of nothing better at the time, screwing around the model parameters is the method that was used to try to match simulated vs measured frequency response. it worked pretty well, as evidenced by hitting the frequency response target on the submaximus v3 pretty close on. the theory and math behind accurate modelling of inductance isn't a domain with which i am familiar, so if there is a better way then we should go with it.

do you happen to know if hornresp has been revised to employ the thorborg approach?

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post #23 of 25 Old 01-12-2019, 04:00 PM
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@andyc56

thanks for the info. i just spent some time over at diyaudio reading about semi-inductance and the adjustment in hornresp. it seems that i had fallen behind.

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post #24 of 25 Old 04-23-2020, 07:36 PM
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I am interested in this horn design. I've modeled, some horn not necessarily the one above, in hornresp using a um18-22 and 500w power. I chose this because I have two um18-22 and an amp that does two channels 500w @4ohm . The expansion ratio is 3.68. Assuming the hornresp parameters roughly matches the horn above I'd like to try building this horn. Are there full dimensions anywhere for the horn fold depicted above? I can muck around in hornresp but folding is out of my league.

I was going to add the hornresp image but adding an image is beyond my abilities. My simulation uses the parameters of the hornresp above using a OD horn and a um18-22 driver.
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post #25 of 25 Old 04-24-2020, 10:28 AM
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FTR,
Max V2 and V3 run off a 6K, 1 channel each thru a 2x4HD @ close to full throttle
and @hd0823 has his 4 using 21's and lord know how much oompah -loompah

there are better designs to take advantage of the subs and amp you have,
like the Marty sub line

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