Whoops, forgot about the sand. She's sealed so no going back. But now that I don't have the wimpy dowels in place the cabinet is much less resonant. Knuckle rap test tells me it's fairly solid at least, and I don't hear any overt cabinet resonances but I need to do more listening. Tapping the side of the mouth still produces a hollow sound, but I'm guessing that not abnormal. I have 2 sets of isolation spikes that I might try to fit on at some later point. I also need to try to build those stands and see if they change the sound. I know you recommend lifting them, but I feel like the BK12 needs all the floor coupling it can get. I imagine the FE166 driver itself has decent midbass response. The FE126 has none.

These speakers seem to defy conventional logic when it comes to the bass being omnidirectional. It's definitely not. Usually when you take a few steps off-axis, it feels like the tweeter got turned off. With these, it feels like the bass and treble go away. So I guess these have a more uniform off-axis roll-off than you traditional 2-way. But the treble's off-axis response doesn't look too great I'll wager.

I'm going to find my old man's camera stand and see if I can mount the mic on that effectively. That'll give me adjustable height too. I think my near-field measurements (with a single speaker) are a little skewed because I just placed the mic on the other cabinet. The surface could have caused some problems. My near-field (at my desk) measurements of the OS were very interesting though. I'll post those sometime tomorrow. I would like to try measuring outside, but tomorrow is Saturday and I don't want to piss off any neighbors. That'll have to wait for Monday.

What exactly should I be listening for with the 1/3 octave noise? I was trying log swept tones with the OS to see if I could point out where the port shuffling was happening at high SPLs. It seemed to be happening all the way up to 100Hz actually. Then I tried listening for the room modes (or horn modes?) between 100 and 300. I was able to identify the peaks but trying to find the dips was a lot harder. As in, they didn't sound like reductions in SPL just general weirdness at that area (~175Hz). I need to try this with the BK12 and measure the mouth up close and see what happens.

Here's the desktop setup. Mic is placed approximately where my head would be when listening. Parallel with ground. 2' from each baffle. This is slightly above the tweeter's vertical axis, but *way* off-axis horizontally.  Note the tweeters are firing past the the mic; I'm not doing the classic equilateral triangle here. Why not? Toeing in directly removes the perception of depth and soundstage I find. They *can* be toed in directly without seeming to bright (Carmody accounted for this in his design), but this configuration seems best to me.




Red is desk, blue is living room. Not level matched obviously.

Bass is way too boomy as you can see, although this is to be expected when the rear port is <6" from the wall. Subjectively, this is just as bad as it looks. It's the first thing you notice when sitting down to listen. Makes me wish I had built a design with a front port like the Zaph ZA5.2. The null at 170 seems to be mostly gone though, telling me this was probably a living room interaction. I'm also noting that the peak at 250 isn't here anymore, although the one at 120 still is. I think I can surmise that 120 peak has to do with the port specifically, which is why this back wall is aggravating it here to an even higher degree.

Now..the null at ~350. I'm thinking this is a cabinet resonance. Playing chromatic scale (at high SPL) lets me hear a very annoying vibrational resonance going on here. I don't think this is my port vibrating or shuffling though, that seems to happen down lower. I'm not sure if this is a construction fault on my part or just the nature of the beast. I've never noticed it with music though, but again, I listen near-field at fairly soft levels. I'll have to figure this out later.

Treble roll off is even more exaggerated in this positioning, as is expected when you're this far off-axis. But note the resonances at 1k and 2k here. More on this next.

So, a buddy of mine told me I should take near-field measurements of a single speaker to get a better look at what's going on with the driver's response. He recommended I take the measurements in the center of the room elevated off the ground by at least 30", with the mic 1m away. Here's that.





Ok, so obviously the 120 peak is gone now that I'm far enough away from the wall, although my 170 null is back (because of the living room?). But other than that, this speaker is fairly flat and well extended. Except for some problems with the upper-midrange. I originally thought this was cone breakup. Metal cone woofers are supposed to have major problems with cone break up. But it wouldn't make sense to have the whole region around 1-2k elevated. OTOH, the peak at 4k (which is also the xover point) looks exactly what I expected the cone breakup to be. It sounds like it too. Nastiness there when I play chromatic scale.

So what's going on in the presence region? I don't know. I originally though the 1k, 2k, 4k might be the triple octave penetrator that has been spotted in headphones. But I'm not hearing it. I've commented before that the OS seems recessed in this region more than anything. Here's Carmody's own commentary FWIW:

The actual woofer filter is 2nd order electrical, with the addition of a small capacitor across the inductor, which acts as a notch filter (these are sometimes referred to as "tank" or "elliptic" filters). The tweeter filter is 3rd order electrical, with an L-pad used to attenuate the tweeter's level. The crossover point occurs around 4,000 Hz. Although it's not apparent on the frequency response graph, I intentionally voiced the Overnight Sensations with a subtle dip in the midrange. I did this for two reasons. One, to ensure that the speakers would be listenable for hours and hours without becoming fatiguing . Two I wanted them to be forgiving of recordings that were "less than top-notch" (of which I have many).

It might be the tweeter's output is combining with the woofer in this region, which is why we're seeing it elevated.

Bass is way too boomy as you can see, although this is to be expected when the rear port is <6" from the wall. Subjectively, this is just as bad as it looks. It's the first thing you notice when sitting down to listen. Makes me wish I had built a design with a front port like the Zaph ZA5.2. The null at 170 seems to be mostly gone though, telling me this was probably a living room interaction. I'm also noting that the peak at 250 isn't here anymore, although the one at 120 still is. I think I can surmise that 120 peak has to do with the port specifically, which is why this back wall is aggravating it here to an even higher degree.

Can you use port plugs? How much of the <100Hz response is the port as opposed to the driver itself?

Maybe try cutting some foam to fit. Pipe insulators would also probably work, and they would allow you to experiment with reducing the size of the port rather than sealing it entirely.