Here's my rough attempt to overlay the impedance curve for the TH118 on the published on for the TH115, which is basically the same horn with a 15" driver. Note where the lower resonance point is for both. Basically it looks like the whole impedance measurement has been shifted down by 10 Hz, and the impedance magnitudes reduced by a factor of three.
Hmm, maybe that's exactly what happened...
.Attachments
Subtracting the area of the cone really depends on the dimensions of the cone you have! From the calculations I have made in the past you have squashed S2 by an large amount. Where you have a S2 dimension of 18mm I would recommend a more gentle 38mm Still a lot less than the original 86mm - For S1, I have a dimension of about 166, and I did not have the extra bend between S1 and the flat section of S2.
The flat section width dimension you have as 113mm I calculated as 90mm - where you have added 70mm to the centre panel I have 47mm. I Think the amount of compression you have at S2 would kill a lot of the drivers used by many DIY builders. Build at your own risk!
Unfortunately I don't have time nether budget to build at my risk 
So here is the sketch updated.
Colored in green the extra bend not present at your design nether some rounded panels.
So here is the sketch updated.
Colored in green the extra bend not present at your design nether some rounded panels.
An externally hosted image should be here but it was not working when we last tested it.
Putting drivers with 25-30% less motor force into a TH that did not exist in an 18" version until the stronger neo motors came out would be a reasonable indicator that you won't get an equivalent performing system, add to that you also have half the x-max and probably 1/4 the power handling, cone, and suspension quality. Good times ahead...
Dan, so from your point of view FLH or BR would be better options for those drivers?
The motor force I think that drivers are aligned at least regarding 18TBX100, 18LW2400 and 18W1000, BL 25,5 T/M 25,6 T/M and 27,6 T/M, and the Xmax are aligned too 9mm 9,5mm and 7mm respectively.
If you consider 18SW115, 18NLW9600 or even V18-1000 is a different history, don't you think?
Oversound Sub800 - BL 25 T/M - Xmax 8mm
Keybass KSPA-18-1200 - BL 28 T/M - Xmax 6,5mm (stronger motor with less Xmax, this one could be a problem).
The motor force I think that drivers are aligned at least regarding 18TBX100, 18LW2400 and 18W1000, BL 25,5 T/M 25,6 T/M and 27,6 T/M, and the Xmax are aligned too 9mm 9,5mm and 7mm respectively.
If you consider 18SW115, 18NLW9600 or even V18-1000 is a different history, don't you think?
Oversound Sub800 - BL 25 T/M - Xmax 8mm
Keybass KSPA-18-1200 - BL 28 T/M - Xmax 6,5mm (stronger motor with less Xmax, this one could be a problem).
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I didn't get the point from Dan, maybe is my english, but he didn't reply, soo.
Still regarding the driver Keybass KSPA-18-1200 with Xmax 6,5mm, I made contact with the manufacture and they answered me indicating the Xlim=15,2mm, so regarding the simulation the diaphragm displacement will be in between Xmax and Xlim the same I've seeing on many simulations, looks like the risk is to add more distortion but not much perceived by the public at low frequencies.
Another option is to install 15" driver over 18" one and in this case I found a good option.
Look at this comparison between 18sound 18LW2400 and Snake HPX2150 @2,83V and @61,32V
Hornresp inputdata for 15" driver
Thiele/Small data comparison
Displacement results @61,32V (800W@4,7ohm) - Shows 1,2mm (>Xmax8,5mm but < Xlim 22mm).
Is this option better them the 18" one Keybass KSPA-18-1200? all results looks the same the only difference between them is the diaphragm displacement capacity.
The price is the same for both drivers.
Still regarding the driver Keybass KSPA-18-1200 with Xmax 6,5mm, I made contact with the manufacture and they answered me indicating the Xlim=15,2mm, so regarding the simulation the diaphragm displacement will be in between Xmax and Xlim the same I've seeing on many simulations, looks like the risk is to add more distortion but not much perceived by the public at low frequencies.
Another option is to install 15" driver over 18" one and in this case I found a good option.
Look at this comparison between 18sound 18LW2400 and Snake HPX2150 @2,83V and @61,32V
An externally hosted image should be here but it was not working when we last tested it.
Hornresp inputdata for 15" driver
An externally hosted image should be here but it was not working when we last tested it.
Thiele/Small data comparison
An externally hosted image should be here but it was not working when we last tested it.
Displacement results @61,32V (800W@4,7ohm) - Shows 1,2mm (>Xmax8,5mm but < Xlim 22mm).
An externally hosted image should be here but it was not working when we last tested it.
Is this option better them the 18" one Keybass KSPA-18-1200? all results looks the same the only difference between them is the diaphragm displacement capacity.
The price is the same for both drivers.
You will have problems with your driver of choice in the TH18 sub because the MMS is a bit to low. What this means it that the diaphragm,voice coil former, suspension and all the other moving parts are thin and possibly weak. If they are using extremely high quality parts, that could have been a non issue but I bet if they are cheap they are not using the best parts possible, probably the opposite. So those parts will behave in a chaotic way especially under compression from a horn loading.
radulescu,
Now is very clear.
So I can also conclude that those driver below aren't good for TH18, because it will easily damage even with low power level, besides the Xmax. In this case I need to find other cab design and consider this constrain for what a have available.
18Sound 18LW2400 - Mms = 192g (Hummmm - Is this good enough?)
18Sound 18W1000 - Mms = 139g
PrecisionDrive PD186 - Mms = 184g
RCF L18P300 = Mms = 180g
Maybe the target for TH18 is Mms higher them 220g genericaly speaking, so the optimal driver would be just:
Void V18-1000 - Mms = 226g
B&C 18SW115 - Mms = 275g
18Sound 18NLW9600 - Mms = 261g
Looks like this cab is a binary solution, or good or crapy, there is nothing in between
Now is very clear.
So I can also conclude that those driver below aren't good for TH18, because it will easily damage even with low power level, besides the Xmax. In this case I need to find other cab design and consider this constrain for what a have available.
18Sound 18LW2400 - Mms = 192g (Hummmm - Is this good enough?)
18Sound 18W1000 - Mms = 139g
PrecisionDrive PD186 - Mms = 184g
RCF L18P300 = Mms = 180g
Maybe the target for TH18 is Mms higher them 220g genericaly speaking, so the optimal driver would be just:
Void V18-1000 - Mms = 226g
B&C 18SW115 - Mms = 275g
18Sound 18NLW9600 - Mms = 261g
Looks like this cab is a binary solution, or good or crapy, there is nothing in between
DSL uses the B&C 18SW115 in the TH-118, the XOC1 TH18 is basically a copy of the commercial cabinet, which originally used the 18Sound 18NLW9600, which had "rocking" problems at certain frequencies.
The B&C 18TBW100 is also a good choice, with a MMS of 268.2, it is more sensitive and less expensive than the neo drivers, but slightly less ultimate output than the 18SW115. That said, with 3000 watt peak power, I expect it to actually have a bit more output due to the higher sensitivity than the 18SW115.
I'll be using the B&C 18TBW100-4 in the new Keystone "B-Low" (29 Hz Fb) design.
I recently did a "push up" test on one of my B&C 18TBW100-4, with my hands around the dust cap, 98 pounds (45.5 kg) weight, it went to Xlim, no damage to the cone or surround whatsoever.
The lightweight cones you mentioned earlier would crumple or tear if you tried that test on them.
Art
Good news, I found the 18Sound 18LW2400 to buy here for the double price of a local drive, so this is the only one good option I have, so I i will also take all feedback you guys gave me into account while I'm selling my old stuffs to start build the new one.
I will also start another thread for other cab type and let this one flow without many interruptions from my side. So thanks if you guys can give me a little help there too.
I will also start another thread for other cab type and let this one flow without many interruptions from my side. So thanks if you guys can give me a little help there too.
I've told you a few times now that the 2400 is not a good choice - at least not ideal.
I've also told you a few times to double up Re in your sim to get a crude idea of what's going to happen if you get the driver hot and get into serious power compression. I assume you haven't done that, if you had I doubt you would be considering the 2400 still.
I've also told you a few times to double up Re in your sim to get a crude idea of what's going to happen if you get the driver hot and get into serious power compression. I assume you haven't done that, if you had I doubt you would be considering the 2400 still.
Of course I made it, double Re makes all drivers bad, compare the 18LW2400 againt 18SW115. What you conclude? Even 18SW115 is a bad choise for this cab? is there a good choise considering 2*Re?
Using less power then your driver capacity will help to reduce power compression due to thermal effect on Re.
It also doesn't make sense too me that there is no under 1000W driver option for this cab. It's like install V6 engine in a 1000kg vehicle, you can do it but you don't need. It's not a competition. Maybe 2.0 engine is enough.
Using less power then your driver capacity will help to reduce power compression due to thermal effect on Re.
An externally hosted image should be here but it was not working when we last tested it.
It also doesn't make sense too me that there is no under 1000W driver option for this cab. It's like install V6 engine in a 1000kg vehicle, you can do it but you don't need. It's not a competition. Maybe 2.0 engine is enough.
First of all, the dip in the SW curve is clearly not as deep as the 2400 dip at 2xRe. It's not a big difference but there is a difference.
Second, the 2400 is a 1200 watt driver, the SW is a 1700 watt driver, so presumably the SW will handle heat better than the 2400.
Third, the 2xRe sim shows that tapped horns in general aren't that great when it comes to heavy power compression - this is a good reason to look into front loaded horns - they are much more graceful at 2xRe - but they can also require more power to reach xmax so to some extent it's not a clear advantage, it has to be studied case by case.
Yes, obviously. The point I was trying to make was that the higher Bl drivers will look a lot better in both the regular sims and in sims where Re is doubled.
If you don't need it that's fine, but most people want it.
If you only use 600 watts you could use a driver with less xmax and a lighter (weaker) cone. But you still need the high motor force or the frequency response will show the high q shape that the 18 Sound 2400 has.
And I guarantee that 600 watts will becoming boring very quickly. You will find that you want more. A lot more.
JAG,
1) Presumably those interested in XOC1 TH18 design are considering it because of it's relatively small size of around 15 cubic feet (416 liter) exterior volume, high output, and low frequency response. What "case" of a front loaded horn of 416 L exterior volume would compete favorably in terms of SPL and low corner?
2) Interesting, the dip in the SW curve at 2xRe may have been responsible for the upper reduction in output noted in the "full power" B&C18SW115-4 Keystone TH sine wave tests compared to the BR tests- the TH has upper pass band low impedance points, while the BR has a steadily rising impedance. As the tests were started from low frequency, which has better heat pumping, and ended with upper frequencies, which don't pump as much heat from the voice coil, the upper pass band compression noted in the TH compared to the BR makes sense, thanks for the insight.
3) Having began my career using drivers with 100 to 400 watt potential (the 400 watt drivers being less sensitive, having only a few dB at best more output potential), I did not find them to be "boring", other than the requirement of lugging around a lot more plywood and fiberglass to achieve what modern drivers are capable of.
The difference is a lot less than you make it out to be, as the heavier, higher power drivers are inevitably less sensitive than their lighter counterparts, resulting in some of the additional power required to move the additional moving weight not being used as effectively, causing more relative Re increase.
Although I won't go back to using drivers with less Xmax due to my professional self-imposed size and weight use restrictions, if size and weight are not a primary issue, lower Xmax drivers that are in abundance both new and used can be a more cost-effective solution to providing a given SPL than modern heavy MMS high excursion drivers for those willing to lug and store more cabinets.
For some markets, the size of the stack is more important than the output, so the cheaper drivers can be doubly cost effective, and doubling frontal area and cone area can result in a 6 dB increase in level, so will actually achieve far more "breathtaking" results than the same power used with high Xmax/Mms drivers.
Art
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