Originally Posted by Mark Seaton
I guess you can go to extreme lengths to reinforce IB construction, of course you could just eliminate the source of the problem and use a balanced, opposed mounting where the concern is then just the spill of the IB's rear radiation and the acoustic energy in the room... which will be an issue for any subwoofer.
Obviously poor integration, poor component choices and poor location can muck up most any subwoofer design. With sufficient drivers to keep out of the red, an IB is a killer solution that should be a sanity check when describing the worthiness of any subwoofer design. I'm not saying they are the best or un-beatable, just a worthy point of reference for good performance in the DIY realm. Outside of Ilkka's measurement of the single vented TC-2k, I've seen a lot more DIYers with IBs take more detailed measurements as to the end result. While there is all sorts of talk of a design's strengths, there is precious little talk of the confirmation of what they do. Many if not most will perform extremely well, but assuming ideally linear operation under most all circumstances is rather optimistic based on my experience. Plain and simple, if you haven't measured it, you are guessing or hypothesizing.
When a guy hits a nail on the head it usually is driven home. Unfortunately, Mark's points will largely be ignored, as are most intelligent posts that have real points to consider ignored in these discussions.
My point was a shot in the dark, but thank goodness guys like TW, Ssab and Seaton check in once in a while to notice it. The point being that IB is the perfect reference starting point.
Bang for buck, least obstructive, most efficient, best extension, low non-linear distortions, flat in-room FR, low GD, adjustable roll off, high headroom and looks mean absolutely nothing.
I prefer a sealed box of much smaller proportions because, besides offering all of those good things, save efficiency and bang for buck, I gain the ability to limit excursion, to eliminate some non linear distortions, placement options, corner loading (which is free lunch) and they look cool as hell and I'm taking them with me when I move.
Like Mark pointed out, where are these measurements that show lower distortion, flatter response, deeper extension, more headroom, etc.? Chas' IB was posted flat to 6Hz. My in room response has been posted, flat to 3.5Hz. Many IB owners have posted graphs. Seaton posted the in room response improvement in Art's HT to 10Hz, but the majority of ported in-room graphs posted have been cut off at 15Hz, and Ilkka only tests to 10Hz, GP.Show me the money!!