Here is the post where someone asked about the sealed box use and my reply. The quote in post #94 is not right so it appears like I was the one who made some addditional claims that I had not made.
In a sealed enclosure, output is determined primarily by enclosure size and input power. In the case of the LMS5400, it has more excursion and handle more power allowing it to get much louder when output is excursion limited. However, when excursion limits don't come into play, the TD18H+ will have huge advantages. You can see how both drivers compare in a 5cf sealed enclosure here:
At 20hz, the TD18H+ is limited to 700W to stay within the 14mm Xmax range. In reality the suspension is good to nearly 25mm one way so it is not unreasonable to put in 1000W. At 20hz, the TD18H+ has about a 1.7dB advantage in efficiency. At 100Hz it has a 6dB advantage. At 100hz this means the LMS5400 needs 2800W to reach the same level of the TD18H+ with only 700w. This alone is a massive advantage in keeping distortion low. Factor in the issues related to Le(i) (flux modulation) and the distortion created when putting that much current into the coil and the TD18H+ has a huge advantage as long as the output at 20Hz is enough.
Ricci, I will send an email to you. Something still isn't right if that happened again. I have not experienced any of those issues with over 250 standard TD18H+ that are in the field now. We have a sound company based in Chicago market that is using 20 of them in EV Xline Sub boxes. They do sound for EDM events and festivals. They kept destroying the EVX180B's on a monthly basis. They tried the TD18H+ in 10 dual 18 cabinets back in June. Each cabinet is run off a bridged Crest 8001 (2800w 4ohm bridged) and run full out to clipping for weekend long festivals at times. They have not had a failure. Elite Audio has been running individual TD18's off 2500W Lab Gruppen channels from the FP+10000 with no burnt or shorted coils in nearly 3 years now. He has 24 drivers in the field and swtiched to the TD18's after having failures with the B&C 18BTX1000. Another local sound company is using a bridged Itech 6000 per cabinet with some PAS dual 18 cabinets now housing the TD18H+. This is 5000W bridged per pair of drivers. He has had 16 drivers in the field for over a year now without a coil failure after having continual failures with the RCF 18's that were in the cabinet. These are drivers used 4-7 days a week and abused for hours on end. I can't imagine you are pushing these nearly as hard as they do.
These are all non-apollo option woofers. The apollo should only increase the thermal power handling. Something is either not right with the coils as we found in the first batch from Precision, or something else is happening. I would like to get you a non-apollo version to try out for comparison. There may be something with the gluing of the apollo rings and either the glue coming into the gap, or solvent from the glue causing issues with the VC adhesive. I definitely want to find out what the issue is though.