I'm sure that the TH18 can be improved on. One interesting aspect of the Othorn is the theoretical compression ratio at S2 in a Hornresp sim is far greater, over 4:1 compared with 2.5 in the TH18. But we now know that this is not the true compression as it does not take account of the internal volume of the cone.
Builders of the TH18 that have increased the compression at S2 have had good results. Of course increasing the compression could be disastrous with some drivers and beneficial with others.
Interestingly my first ever posting of the TH18 design had far less reflectors and was therefore even closer to the Danley TH118. The extra reflectors were added because of other forum members requests.
I do know of a extended version of the TH18 which was built with good results for extra bass extension. Predictably the efficiency suffered as a result, all the aspects need to be balanced. Again the Othorn has an edge here as its 21" driver can push more air.
Builders of the TH18 that have increased the compression at S2 have had good results. Of course increasing the compression could be disastrous with some drivers and beneficial with others.
Interestingly my first ever posting of the TH18 design had far less reflectors and was therefore even closer to the Danley TH118. The extra reflectors were added because of other forum members requests.
I do know of a extended version of the TH18 which was built with good results for extra bass extension. Predictably the efficiency suffered as a result, all the aspects need to be balanced. Again the Othorn has an edge here as its 21" driver can push more air.
Are there any measurements that show an improvement from "cone correction"? Or is it all subjective? Please show links.
The cone divot doesn't change compression ratio and simulating the divot as a throat chamber shows that it makes almost no difference at all.
At least a couple of senior forum members have said that "cone correction" won't do anything good and could possibly make things worse by creating an interruption in the line.
If there's any measurements or anything objective that shows "cone correction" does anything good that you could link to I'd like to see it.
The othorn is a pretty darn incredible subwoofer. My girlfriend and I have dragged this pair in and out of 30-40 diff gigs of all sorts over the last year and they never cease to amaze. I mean just when you expect them to run out of extension or output they just go that extra bit. We pulled a 21-152 driver out for cleaning today and it seems good as new. These things have taken an absolute beating and are cruising right along.
We also played with the xoc th18 today. I liked it more today then the last time. Its really not THAT far off from an othorn. People have told me its really only a 40hz sub but it sounds deeper than that. They aren't so different to where you would want to run them together, both dominate 35hz-60hz so it would be to much overlap in my opinion.
Its so nice to be able to wrestle it around! Another cool thing about the xoc is that you can stack them so easily. Othorns may need many people or machinery after a few level levels (well...to do it safely at least). We want to build several th18s and would love to add the corrections!!
I would be game to try a keystone, is there a link to detailed plans por favor? I feel like weltersys normally pops in by now. Must be busy designing more speakers!
We also played with the xoc th18 today. I liked it more today then the last time. Its really not THAT far off from an othorn. People have told me its really only a 40hz sub but it sounds deeper than that. They aren't so different to where you would want to run them together, both dominate 35hz-60hz so it would be to much overlap in my opinion.
Its so nice to be able to wrestle it around! Another cool thing about the xoc is that you can stack them so easily. Othorns may need many people or machinery after a few level levels (well...to do it safely at least). We want to build several th18s and would love to add the corrections!!
I would be game to try a keystone, is there a link to detailed plans por favor? I feel like weltersys normally pops in by now. Must be busy designing more speakers!
There are tons of measurements of designs that have a weak low corner due to the lack of accounting for the volume in the cone.
I'm not even sure what you mean by this. A simulation will show that there is almost no difference at all between not simulating a throat chamber at all and simulating a throat chamber of a few liters to account for the cone divot.
If there is a well known advantage to "cone correction" there should be plenty of measurements to back this up.
Can you provide a single measurement to show the benefit, or at least a single measurement to show what you mean by "a weak low corner due to lack of accounting for the volume in the cone"?
I know there are a couple of subjective reviews of cone correction but that means nothing, it's what you would expect to hear from someone who believes that the extra work they did would provide a benefit. I'd like to see measurements, at least one measurement.
there is a 2 percent difference in size between the outsized volume of the keystone and the th18. the lack of reflectors and minimal bends in the keystone means it has a bit more internal volume.
I'm not sure I follow how it takes more wood..., other than the nee for a full front panel.
while the keystone has a shorter pathlength, the mouth restriction brings tuning down to a similar level.
I'm not sure I follow how it takes more wood..., other than the nee for a full front panel.
while the keystone has a shorter pathlength, the mouth restriction brings tuning down to a similar level.
I've never studied either of these designs in depth so I can't comment on either specifically but physics and common sense allow some perspective.
Dan says the Keystone is tuned higher, PASC says Keystone has more lows. Which is it? It can't be both.
Both Dan and PASC say Keystone should be more efficient, PASC says 2 db or more. If the boxes are ~ the same net volume and tuning they will be ~ equal in output. You can get more output at certain frequencies by having a different response curve but overall net volume dictates max output. (Unless there is something seriously wrong with the design or the construction of the sub.)
Forward directivity is a different issue, and the one with a larger front face will have more forward directivity but the difference isn't large. Keystone is 45x26.5 and XOC TH118 is 40x22.5. This amounts to a bit over 1/2 db difference. Nothing to get excited about. Keystone approximation on top, TH118 approximation below.
An externally hosted image should be here but it was not working when we last tested it.
So... there's absolutely no objective evidence that "cone correction" does anything at all?
This isn't a surprise, since theory and simulation say it's nonsense, but I was expecting to see something from the people that have been talking about it over the last couple of years like it's the best thing since sliced bread.
This isn't a surprise, since theory and simulation say it's nonsense, but I was expecting to see something from the people that have been talking about it over the last couple of years like it's the best thing since sliced bread.
I used the cut list .pdf from post #1 in the TH-18 Flat to 35hz! (Xoc1's design), so that probably isn't the final form. Anyway, 2 inches won't make much difference to the sim I showed, but it will make the two responses even closer than shown - so really not much difference in forward directivity between the two.
So does the Keystone tastes great or is it less filling? 
Am I right, the next big TH would be JBell's stadium horn? The cool part about this design is how well inexpensive drivers work with it. I would have gone OTHORN if I could get a decent priced driver to work with it. All sims I tried except that 21" are worse than KS/XOC.
Am I right, the next big TH would be JBell's stadium horn? The cool part about this design is how well inexpensive drivers work with it. I would have gone OTHORN if I could get a decent priced driver to work with it. All sims I tried except that 21" are worse than KS/XOC.
OK. I researched this for a while and the last posted HR data txt file on the Keystone is posted here #254. http://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers-26.html
Can someone more knowledgeable than I critique this and advise if accurate. This is driving me nuts...
Can someone more knowledgeable than I critique this and advise if accurate. This is driving me nuts...
So does the Keystone tastes great or is it less filling?
Am I right, the next big TH would be JBell's stadium horn? The cool part about this design is how well inexpensive drivers work with it. I would have gone OTHORN if I could get a decent priced driver to work with it. All sims I tried except that 21" are worse than KS/XOC.
More subjective insight. The KS is louder than an SRX728 (by at least 3dB, probably more), and doesn't seem to be missing anything in low end extension.
My 18TBW100 that I managed to toast reached it's thermal limit far before it showed any signs of mechanical stress, the KS seems to control excursion.
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Hi Zwiller,
Post #38: "...HR data txt file on the Keystone is posted here #254. Keystone Sub Using 18,15,&12 Inch Speakers......This is driving me nuts..."
When you read through the whole Keystone thread(s) you'll find, that the measured results do not correspond to the Hornresp simulation. The reason is the reduced cross-section and offset keystone horn mouth. The standard Hornresp TH simulation will not show the same low end as Art Welter's measurements which have been confirmed by PASC.
Regards,
Post #38: "...HR data txt file on the Keystone is posted here #254. Keystone Sub Using 18,15,&12 Inch Speakers......This is driving me nuts..."
When you read through the whole Keystone thread(s) you'll find, that the measured results do not correspond to the Hornresp simulation. The reason is the reduced cross-section and offset keystone horn mouth. The standard Hornresp TH simulation will not show the same low end as Art Welter's measurements which have been confirmed by PASC.
Regards,
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