I have a pair of super tweeters on top of my KLF-10's. I have tried them on every spot on top of the cabinet where they will fit. I have pointed them backwards, forwards, sideways, and tilted them at every possible angle.
Because your Cornwalls are already playing full-range, a supplemental tweeter in a front firing position anywhere near the other drivers is gonna cause "comb filtering", sharp dips in the frequencies being reproduced by both the main drivers and the extra tweeter, where they are experiencing destructive interference/phase cancelling. You can put it flush with the front face, or aligned with the diaphragms of the CW's drivers, or anywhere in between, they will still interfere. If you move the tweeter all the way to the back of the speaker, you might lose the original comb filtering, but you will get reflections off the top of the cabinet and a whole different set of interferences.
The idea of a rear-pointing tweeter comes from the premise that with a large enough shift in time alignment, the external tweeter's outgoing information will be so far behind the information coming out of the mains that it will no longer interfere. In all the testing I did, this did seem to be the case, the comb filtering was eliminated. And, even if the external tweeters are pointing at a far back wall, a side wall, or a ceiling, you will get significant sound reinforcement and don't worry, you won't notice the delay.
But that doesn't mean all your problems are solved. For me, any back, or up, or side, or back-at-an-angle position didn't sound good enough. You do get nice high-frequency reinforcement and a more airy treble, but the downside is this: It diffuses the presence and forwardness of your midrange image. The little bit of midrange reinforcement that those tweeters are giving will soften your midrange and make it lose its focus.
Of course at this point you're thinking: "Well, I'll just give those tweeters a steep crossover slope, way up high, and that'll fix it". You're right, it will, but then you'll soon be realizing that with all that time, effort, and money spent on building crossovers, those tweeters are sounding pretty sweet and you bet they'd sound better pointing right at you. And you're back at square one.
IMHO, the idea of a big shift in time alignment has merit. But I didn't like pointing them backwards. What I did was pointed them forward, place them as far to the back of the speaker cabinet as they would go, and I also lifted them up off the surface of the cabinet by a few inches. They are far back enough to lose most comb filtering, and up off of the cabinet enough, to not have significant reflections. It's easy to tell if you're getting reflections: With the tweeter in a interference producing position, sit in a chair up close between the speakers and listen to music while moving your head around. You won't just hear changes due to off-axis issues, you will find zones of extreme high frequency cancellation all over the place as you move your head around. In the position I now have my super tweeters, I no longer hear that. And I sit close to my speakers, as they are on either side of my desk in a near-field setup.
It's known that having the driver array of a speaker close together is better for time alignment and under normal circumstances, you wouldn't want your tweeter sitting so high, far from the other drivers, but in this case, we are trying to separate, so, at least for me, it works. The added lift is added distance. It's not the perfect solution, nothing is. But the forward, powerfully present midrange of a Klipsch horn driver was not something I wanted to compromise.
Now, the KLF-10's are 16 inches deep, giving me a decent distance for a decent time shift. CW's may be deep enough too. You can always buy a low priced pair to try, mine were 20 bucks from Parts Express and I'm still enjoying them. I'll eventually get a pair of ribbons or something else nice. In the images, those are the tweeter covered by a microfiber cloth for a bit of attenuation, sitting on a 4x4 block with padded feet. And note that I didn't even get into the whole issue of how the tweeter will affect your speaker's impedance profile...
So... after goofing around a while after writing I have to admit i am a moron.
I misread the On/Auto/Off standby and when my receiver said make sure Stand By is off on your woofer, I thought turning Standby Mode meant putting the switch to Off because of my lack of reading comprehension skills lol. The moment I out it in Auto or On
Yeah it worked and we enjoyed Frozen 2 and my walls rattled.
Well at least I hope people get a good laugh LoL.
Well, 10KHz may indeed be a little high. But, I don't think one would want too much overlap with the K77. Of course, with a 1st order network the rear firing tweeter would only be down 6dB at 5KHz and 12dB at 2500Hz. I would just have to grab a handful of different value caps, and listen to which one sounds the best - it should be pretty obvious with a little trial and error. I would think the effect should be subtle for the best performance; after all, the Cornwall is a pretty well balanced speaker as is. But then again, the whole idea may just be a bust, which is why I was asking...
BTW, lovely room you have there, Gary. Thank you for posting.