I agree that providing a strong input signal below the port tuning frequency is probably the easiest way to kill a ported sub.\nHowever, I think you are not addressing frequencies above the port tune and how to ensure a proper balance between amp clipping (due to not enough amp power) and overloading the sub (due to too much power). Maybe I am over-complicating it, but using a 250 to 500W amp for a 500W rated sub seems like a broad brush for what I perceive as a matter of fine tuning!\nI might believe that the manufacturers use some sort of limiters to provide frequency dependent output limits?\n\nI look at active speakers like the JBL LSR-305's and what it takes for JBL to make them bullet-proof and think it is an amp with specific, customized parameters. A subwoofer may be less sensitive to these concerns, but I don't know about that!\n\nMaybe @Ed Mullen could give us some idea of what they do on this count?\n\n1. Regardless of what I'm watching or listening, I love Hearing and Feeling the bass, gotta have a lot of bass to SHAKE my room and everything (sofas, pillows) in my room like an EARTHQUAKE. I've never felt like I'm missing anything with a HPF of 20-30Hz. I've tried using HPF of 20Hz, 25Hz, and 30Hz. It seems the difference in the magnitude of the bass was minimal.\n\n2. I've used from 60WPC (ATI amp) to 200W (ATI amp) to power my passive SX-1010 subs. Right now my ATI AT2005 amp is powering my RBH subs (1010s).\n\nIn my living room, the RBH SA-500DSP (500W into 4 ohm) external sub amp is powering the SX-1212 (bottom cabinet of the SVT towers).\n\n3. But I think you have an excellent point about taking a RISK when you go with passive subs vs active subs. I guess because I've always used passive subs even with 60WPC amps and always had room-shaking-earthquake bass with my subs, I've taken them for granted. But there is a risk of blowing your subs.\n\nIn the end, the user has to weigh the risk vs benefits of using passive subs.\n\nI've mentioned this several times on AH, but a friend of mine owned a brand new flagship SVS sub. He had to replace the amp on that sub TWICE in 3 years. Now I've hooked him up with the RBH SVT\/R towers and SA-500DSP amps. He says the bass of the SVT\/R towers are at least as awesome as his big SVS sub.\n\nRBH sells Sub amps (SA-500DSP) that go with their Subs. So these amps were designed to work perfectly with their Subs. The only difference is that the sub is EXTERNAL.\n\nRemember I used to own those Red Linkwitz Orion? They are Active speakers that require 8 amps per pair of speakers. Yet the amps are external (60WPC x 8Ch).\n\nSo perhaps sub (and speaker) companies could offer subs (and speakers) with external amps designed to work perfectly with their subs?\n\n"Active" subs and speakers can still have EXTERNAL amps.\n\nSo sure, let's do all Active speakers and subs. But let's keep the amps external and SEPARATE for better reliability and easier replacements or repairs.