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Ricci's Skhorn Subwoofer


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#1 Ricci

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Posted 11 November 2016 - 10:24 PM

Here's the design I'm going to be using to replace my Othorn. It's been "almost" done for a long time now but I finally made an effort to wrap it up to the point that it is ready to build. Originally I was going to go with another TH design I was calling the Palehorn to replace the Othorn but I wasn't quite happy with it. I stumbled on this type of cab a few years ago while doing a billion simulations of different cabinet designs. You can read some of that in the M.A.U.L. thread. I originally planned to try this design first since it was smaller and cheaper to produce but circumstances led to the bigger more complicated M.A.U.L. getting done first. Since this style of 6th order bandpass / horn cab worked quite well and on target with the bigger design, I used what was learned there to make a few tweaks to this and finally wrap it up.  

 

I'll add a lot more info later, but here are some pics to start with.

 

If anyone feels froggy and wants to have a go at building one of these let me know and I'll send the plans.

 

 

SKHORN ISO.jpg

SKHORN ISO BACK.jpg

SKHORN ISO TOP REMOVED.jpg

SKHORN ISO HATCHES.jpg

SKHORN ISO FRONT REMOVED.jpg

SKHORN ISO 2.jpg

SKHORN ISO 3.jpg

Skhorn work.jpg

Skhorn middle tuning.jpg

SKHORN sim RESPONSE.jpg

SKHORN sim excursion.jpg

 

 

Simplified design layout. Add bracing, drivers, hatches, hardware to taste.

SKHORN basic layout.jpg


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#2 Infrasonic

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Posted 16 November 2016 - 06:10 PM

Doesn't go down to 5hz.

 

*unlike*

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

loljk


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#3 Infrasonic

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Posted 16 November 2016 - 06:12 PM

The model looks like it is loaded with IPAL's. Is that the driver of choice or does this work with the B&C 21SW152 like the Othorn?

 

Do you think this is better than the Othorn in other aspects besides more output over the Othorn?



#4 Ricci

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Posted 16 November 2016 - 06:36 PM

And we're back...

 

 Here's a little back story on this cab and the thought process. About 6 months to a year after completing and testing the Othorn's I started thinking about something that would go "further" and hopefully improve upon Othorn. I have been really happy with the Othorn both from a perspective of the measured results and the subjective results. It's one of my favorite subwoofers for pure music listening at stupid levels. It just does something right. A lot of others tend to agree. I don't know how many people have built them but it's far more than I ever expected. There's a guy with 16 in his inventory from what I hear. That said there are a few things I felt could be improved on.

 

 #1 Cut down on cabinet and panel vibration near the driver.

I have found that one of the main weaknesses in tapped horns is the area under the driver near the mouth. This is often a single sheet of material with a large area which can only modestly be braced, if it is even braced at all. It makes the build easier and makes sense as far as folding most times, but it is subjected to a lot of force. In the Othorn this area is braced fairly well compared to many TH's, but the hatch will flex and vibrate quite a bit once it really gets pushed. Placing the hatch area down takes care of most of this, but sometimes cabs need to be placed horizontally. With a 450g moving mass and a lot of pressure in the Othorn cab it will also tend to "hop" when pushed hard.

 

 #2 Improve the fold or reduce build complexity.

The Othorn horn fold I've always felt was quite ugly with 3 90deg folds. There are some odd angles and tricky pieces to fabricate in there as well. It's a product of cramming a huge driver and enough path length for extension down to 25-30Hz into such a compact package. It is not elegant by any means and I've never been that happy with it.

 

 #3 Higher performance.

Of course I always want to get just a bit more out of the same amount of space so improvements in overall efficiency, voltage sensitivity, excursion limited headroom, power handling and output compression are always a priority.

 

 #4 Driver options.

Most people that build the Othorn's do seem to use the recommended 21 or 18" drivers but there have been a few who have used much more affordable / weaker drivers that simply do not perform right in that cab and won't allow it to perform like it should. Usually if someone isn't happy with the Othorn it is because they skimped on the cabinet build quality or used a driver that isn't compatible. With that said it would be nice if a newer design was more tolerant of other drivers.

 

 I originally went with a refolded tapped horn the Palehorn in the same cabinet form of 24x36x36. The fold was much better and did address the weak areas under the driver hatch so that the amount of panel vibration should be much less. The overall cabinet should be much sturdier. The path length ended up just a bit longer though and the Othorn was already using one of the highest output pro drivers available so it probably wouldn't have gained much in the overall performance department. Being a TH it was still very driver dependent and only the same few very expensive drivers that would work right in the Othorn would work in the new cab. At the end of the day the PH would've somewhat addressed item #1 and #2 to some extent but did not address #3 or #4 on the above list. Overall I'd call it an improvement but not as big of one as I'd like. I also worked on the Gjallarhorn design for exactly the same reasons at the same time and I did release that design update as GH v2 with the improved cabinet design. I probably will release the PH cab design as a final update to the Othorn as a sort of v3 whenever I get around to finishing the print.

 

 What I really wanted were new cabs that would outperform the GH and Othorn so I kept trying things until I found some simulations I liked with the quasi 6th order BP horn that resulted in the M.A.U.L. and this new Skhorn cab. The M.A.U.L. got completely out of hand since it would be a one off personal project that no one else would be building. However since it matched the simulations quite well and in most cases it has the potential to outperform a pair of GH's from only 36% more space I'm quite happy with it. The M.A.U.L. is what convinced me to go ahead with this type of design and tweak and finish off the Skhorn design.

 

 I am happy with the bandwidth covered by the Othorn for loud music or reinforcement applications (25-100Hz). One way to easily make a sub seem more powerful is to sacrifice extension. It'd be easy to make a 40Hz extension sub that is loud as hell but those types of cabs have been around for decades. Personally I just find "subs" that really only extend to 40-50Hz or higher just miss too much of the bottom end of modern music. Notes come up M.I.A.. In my opinion a real "sub" needs to be able to produce a legit powerful 30Hz at minimum or it's just a bass bin. That means I wanted similar extension as the Othorn for the new design. That being the case, since I want the new design to be able to outperform the Othorn and it is already using one of the most powerful drivers available, there's really only 2 ways to make that happen. Make the cabinet larger due to H.I.L. or use more power and have higher displacement and multiple drivers. If you want significantly higher headroom you do both. To that end I decided I'd go with a slightly larger cab with a form factor and size similar to the large dual 18" vented pro cabs on the market. I tried my ass off to miniaturize down an 18 or 21" tapped horn even smaller than the Othorn, so I could join them in a dual cab while maintaining that type of extension and logistically it is just a nightmare. I just couldn't get it to work without severe compromises. Now if you drop to 12 or 15" drivers it can be done but I'm not about that life. The BP6 horn deal does quite well in sizes even smaller than practical TH's with a deep tuning so I was able to compact it just enough to make that happen. The overall design is a bit simpler than folding up a TH as well. With dual drivers it seems to be able to offer some performance advantages from a cab only marginally larger.


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#5 Ricci

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Posted 16 November 2016 - 07:22 PM

What I ended up with finally for the Skhorn is a 24x32x54" cab with dual opposed 18 or 21" pro drivers.

 

That isn't small by any means but pretty compact when considering it'll house either 2 18 or 21" drivers and be effective to about 25Hz. As usual, if I allowed a few more inches here and there, instead of being obsessed with using drivers in the smallest space reasonable, I could improve the results considerably, but before you know it the cab would be 27x60x36 and positively LARGE. In fact originally the cab was a little smaller than this but I needed to add a bit here and there to allow for slightly larger vents, get the vent tuning where I wanted and get the upper section length where I wanted it to be, so it would be boosting the 50-90Hz range. As it is now the cab is 24cu ft or 680L external. The Othorn is 18cu ft so the Skhorn is 33% larger. Vent tuning in the simulations is about 30Hz but this should come in a little bit lower in reality. One thing I like about using vents for the low frequency output is it gives the option of blocking a vent or two to drop the tuning. Having one vent blocked on each side results in a 25Hz tuning in the simulations which again will drop a little bit lower in reality. I'll have to see how it turns out in reality but that may be an option for when I'm not pushing these brutally hard. I was able to do an opposed driver arrangement so that should help cancel out most of the vibration in the cabinet. Most of the cabinet should be quite solid but as usual there are compromises on the driver hatch area. However I think with the extra hatch reinforcement these should be fairly solid. Testing will tell. The throat area is quite generous at about 2x that of an Othorn but using 2 drivers so while the compression ratio is similar the forces involved should be a little lower at the same general output levels. The vents as usual with any vented design are not a big as I'd like but the vents have nearly the area of a 13" pipe in total so it is a bit more than it looks like.

 

I did look at using a straight up vented cab but after simulating this design versus dual driver vented cabs the same size this one seems to have some solid advantages. A vented cab is much simpler and could fit slightly larger vents but it only has advantage in sensitivity right near vent tuning due to the larger air volume available in the cab and doesn't offer as much excursion limited output. I also wonder how much of that extra output right at vent tuning would translate at eyeball vibrating levels. We all know ports tend to compress quite a bit. This is one advantage for horns and the Othorn. they do not seem to compress nearly as much at the low corner due to much lower airspeeds. Testing will tell how the vent compression turns out. Also I've heard a few subs over the years and there is something different about the sound of direct radiators versus cabs which bury the driver inside and produce output through waveguides or vents. I'm becoming a big fan of horns and bandpass cabs that bury the driver somewhat. I don't think it's harmonic distortion that is the primary difference though but it may be one factor. It seems to me to be other mechanical and non harmonic noises from the direct radiating drivers  that make the horns and BP's sound more effortless. Outdoors and in very large rooms like halls and gyms it seems to be easier to hear this difference versus in small residential rooms at low volume. Or maybe it's just plain old more output capability causing it. Either way burying the electro-mechanical device inside the cab seems to clean up the sound at high levels somewhat IMHO. YMMV.

 

On paper this cab when loaded with the correct drivers should be quite a bit more sub than the Othorn. Perhaps almost equaling two with the top drivers though I will need to run it through the measurement gauntlet to find that out and also do quite a bit of listening. I plan on doing a single driver half version as well. If I keep it at truly half size it will not quite equal an Othorn but it would be very compact at 24x32x28" or so which is 50% smaller than an Othorn. I may scale it up closer to Othorn size to gain some performance for a single driver version and possibly make it a completely different design internally. Without the dual opposed drivers it might jump all over the place though because it won't weigh much. That might be a real issue.


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#6 Ricci

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Posted 16 November 2016 - 07:57 PM

The model looks like it is loaded with IPAL's. Is that the driver of choice or does this work with the B&C 21SW152 like the Othorn?

 

Do you think this is better than the Othorn in other aspects besides more output over the Othorn?

 

Hey Scott,

 

I think it will offer some subjective and objective performance improvements over the Othorn. Dual drivers sharing the load is never bad. With less power and excursion per driver for the same output levels I'm hoping the distortion performance is even better as well as potential headroom. The "mostly" force cancelled drivers and better braced cab will hopefully keep it more inert and more free from any potential cabinet colorations. It will have higher sensitivity and the drivers are buried even further in the cab too. Neither one have the best group delay or phase response ever on paper but the Othorn performed exceptionally well in that regard over it's intended bandwidth in my view. It is crazy good for a TH if you look at the measurements IMO. I think a very large part of this is using the undersized cabs with drivers having high self damping. I haven't seen a ton of data for this for other DIY bass horns but I expect they may not be quite as well damped. The M.A.U.L. turned out quite well in that regard too so I've got high hopes for this one.

 

About the suitable driver choices...That was one of my pet peeves about the Othorn. If you try throwing a 8mm xmax 18 with mediocre motor strength in that cab it fails hard. It's not even on the same planet as it is with a 21sw152 or a 21nlw9601. This type of cab seems to be a bit more tolerant of other drivers than a TH and that is good. It is still more picky than a vented cab. This one still follows my usual MO of needing very high motor strength to load it effectively but it isn't quite so picky as with the Othorn. There are some reasonable cost drivers that simulate quite well in it. Testing is needed of course so I can find out where the real cab comes in compared to the simulations so I can then tweak the simulations to better match the real result. That said quite a few different drivers seem useable in the cab to varying degrees. I've listed the ones I've simulated below. Some of the cheaper ones cost less than a single 21sw152. The real fun starts at about the 18 sound 18LW2500 or the Faital 18XL1600 I'd say and the "dumb" kicks in with B&C 21DS115's. In fact those look like a match for the 21SW152's for $100 cheaper.

 

Of course I'll be going straight to the nuclear option and running 21Ipal's in mine whenever it gets built. ;)

 

All of these drivers look serviceable to varying degrees. There are more I'm sure but I didn't simulate everything on the market.

 

B&C 18PZB100

B&C 18NW100

B&C 18RBX100

Faital 18XL1600

18 Sound 18LW2500

B&C 18SW115

18 Sound 18NLW9601 / 9600 / 9600C

TC Sounds Pro-5100

B&C 21DS115

18 Sound 21NLW9601 /9600 / 9000C

B&C 21SW152

B&C 21SW150

18Sound 21ID

B&C 21IPAL

Funk TSAD-21v2 & UH21 :o


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#7 Infrasonic

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Posted 16 November 2016 - 08:36 PM

Wow! Excellent response about this new system, Josh. You answered my questions too. Thanks!

 

What would you say about one of these compared to (2) Othorn's with 152's and equivalent amplification? Disregarding build differences (just performance) what would you say about that comparison? Do the differences come down to TH versus BP and their aspects or something else? There will be differences, I'm sure but I'm wondering. The consensus of the Othorn is that is one of the best sounding TH's around. I believe it! So I wonder if this has the same qualities to knock the Othorn off the podium.

 

Thanks.

 

 

 

 

Oh and can you model me a horn using HT18's? I want it to be tuned to 8hz. Keep it smaller, plz. Done by this weekend? Thanks! :D

 

 

 

 

Sorry. Can't help myself. :P



#8 Ricci

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Posted 16 November 2016 - 10:07 PM

What would you say about one of these compared to (2) Othorn's with 152's and equivalent amplification? Disregarding build differences (just performance) what would you say about that comparison? Do the differences come down to TH versus BP and their aspects or something else? There will be differences, I'm sure but I'm wondering. The consensus of the Othorn is that is one of the best sounding TH's around. I believe it! So I wonder if this has the same qualities to knock the Othorn off the podium.

 

That's a good question. 2 Othorn's should out perform a single Skhorn using the same drivers. Looking at simulations it isn't as bad as I thought it might be. It's pretty close from 35-95Hz. Basically a dead heat on paper. Below 35Hz the dual Othorn's would have a bit of an advantage because they are bigger, TH's and tuned just slightly lower in the sims. 28Hz versus about 30. I expect that the vent tuning will drop a bit lower than expected on the real Skhorn cab so that should put them closer to the same tuning.

 

However consider that the Skhorn isn't supposed to beat 2 Othorns. It's supposed to handily beat a single in a slightly larger cab and come fairly close to a pair with a MUCH smaller cab. Actually what it's really supposed to do is offer a headroom and extension combo beyond any of the vented dual 18 or 21 cabs on the market or pretty much anything else similar in size and extending as low.

 

When you consider that 2 Othorns is 36cu ft of cabinet versus only 24 cubes for a Skhorn that's a big difference in space taken up. 50% more cab volume is a BIG advantage.

 

As usual with me it's not about the most I can get out of a single driver or for the least amount of cash but what can I get out of X amount of cubic volume for application X using whatever means necessary. Can't help it it's just what I find interesting anymore.

 

Oh and can you model me a horn using HT18's? I want it to be tuned to 8hz. Keep it smaller, plz. Done by this weekend? Thanks! :D

 

 

 

 

Sorry. Can't help myself. :P

 

I'm on it. Should have a full prototype and simulations done for ya in 15min.


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#9 lilmike

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Posted 21 November 2016 - 08:27 PM

Any progress on that 8 Hz HT18 horn? I just bought a sheet and a half of plywood, that should be enough, right?

Thanks for all the insights Josh. I'll re-read things when I have a bit more time.



#10 Ricci

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Posted 21 November 2016 - 10:06 PM

Thanks Mike. I must've gave everyone reading information overload.

 

 The sims with some of those drivers listed above look quite good to my eye. Vent compression at war volume is my main concern with it.

 

Now I just need to get one built.

 

I'm working on that 8hz horn Scott wants but for some reason I just can't get it to work while still fitting through a doorway. I don't understand what's going on. B)  Might have to try my new, experimental, patent pending, rotary, quadratic, bi-phase, 10th order, sub-harmonic re-accumulator cabinet to get it to work right. 


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#11 lilmike

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Posted 21 November 2016 - 11:17 PM

"my new, experimental, patent pending, rotary, quadratic, bi-phase, 10th order, sub-harmonic re-accumulator cabinet"

 

LOL!

 

Fair bit of information overload there plus the fact that my schedule is just slammed right now. Throw a work PC that is all sorts of cranky into the mix and I am way behind where I am supposed to be. 

 

I have so many ideas I want to try when it comes to subs, but they're all still on hold. I HAVE to build some temporary furniture pieces, then there's still the fact that I have no railings on my stairways (any of them...). We're hosting a Christmas party in 3 weeks, and those two are just the start of the list of things I need to finish up. Good times.



#12 Ricci

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Posted 22 November 2016 - 03:46 PM

 there's still the fact that I have no railings on my stairways (any of them...). We're hosting a Christmas party in 3 weeks...

 

What the hell is going on over there?! Get it together man. :D



#13 lilmike

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Posted 23 November 2016 - 01:46 AM

Priorities man, I had a couple seasons of "Here Comes Honey Boo Boo" recorded, I just finished the last season of "Jersey Shore".


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#14 Samps

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Posted 25 November 2016 - 02:22 AM

Interesting design. Looks like you put a lot of work into this.

I've stared at the graphics and I just can't imagine how you will be able to build a sturdy hatch recess and still have enough room to fit the driver in. It appears the driver is nearly touching 3 sides. So the hatch opening will need to be pretty close to the full height of the cab. That wouldn't leave any material for the hatch to mount to. And reaching the rear mounting screws looks very difficult. Hopefully I'm just not seeing how this all goes together. At first I thought maybe you were building the cab with the drivers installed.

If it works like you think it will, I might just build one.

#15 Ricci

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Posted 25 November 2016 - 04:08 PM

It'll work. Solidworks modeling FTW. Yes the back panel is mostly hatch but the points the back panel are attached are very solid. The hatches are going to be sturdy as hell. Shouldn't be too bad getting the drivers in really.

#16 Ricci

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Posted 06 December 2016 - 04:07 PM

I am trying to come up with something more affordable and easier to build using this type of cab but it really seems to like low qts drivers. So far I'm not having much luck with lower cost / available drivers.

 

Anyone have suggestions for cost effective bass drivers to look at other than the usual Dayton / Alpine?



#17 Ricci

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Posted 06 December 2016 - 04:09 PM

Also. After Samp's post about the back panel I might make some changes there. Probably just change the pack panel to but up against the ends of the side panels rather than in between them. That would help. Need to look at it.



#18 lilmike

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Posted 07 December 2016 - 01:11 AM

There just aren't a lot of low Qes drivers that also happen to be low inductance and cheap.

 

Wonder why???  I've been looking for years, they just aren't out there.

 

When I get to messing with HornResp again, I will try a few drivers on my short list and see what we get.



#19 Infrasonic

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Posted 07 December 2016 - 06:02 PM

Spent the past day trying to come up with alternate drivers with such features. I really...can't think of any. Hate to say it but you might have to look into high-end car audio but then things are expensive again.

 

The past half-decade has been full of low cost, large-ish displacement (for the money) drivers and they are almost always higher Qes or something else making them otherwise unsuitable for such alignments.

 

Frustrating.



#20 Samps

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Posted 07 December 2016 - 09:10 PM

How about those two 18n862s you have? First cab would be really cheap.




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