SamP

Gee, I was under the impression that the EV T-35 series are the forerunner of the K-77m, and the K-55 is really an EV 8HD horn with an 1824 driver. Just because K can't figure out how to front mount tweeters on a baffle doesn't make my comments invalid. Recessing the tweet horn behind the baffle was a convince decision, not an engineering one. Too bad K wasn't clever enough to insist that the "new" square magnet K-77's be narrow enough to mount from the front. You missed my point that the vertical horn positioning he had used as an example had evolved to horizontal in 1959.

Hate to state the obvious, but at 350 hz the mid output level will be 12dB less than at 700 hz. The woofer output will be hotter. Unless the drivers are outputing equal levels at the same freq, total cancelation CANNOT occur. Same at 1500 hz. The woofer should be downn 12 dB, aand the mid hotter. PHYSICAL separation on the baffle is a reality we multiple driver system owners have to live with. My concern was the sound wave as it travels forward in space from the driver to the listener. Specifically at 10khz, where my tweet comes on line to bolster the falling high end response of my mid. That mid is playing along at a 10 khz. sine wave for example. If the drivers are not brought into acoustic phase, the two signals will interfere, either constuctively or destructively. Look at two "in phase" sine waves on paper. "ADD" them. The peak gets larger, but the base stays narrow. Now shift the phase on one wave, and "add" them. The peak is lower and the base is broader. That's what happens to transient signals, they get "smeared" by poor ACOUSTIC PHASE conditions. Also note the "new" waveform riding on the original wave. Can you spell heterodyne? I know that sound bounces all around the room, there are baffle interactions, etc. It doesn't matter that the tweeter is not physically aligned with the mid driver, just their acoustic phase must be in sync to prevent the interference. This is the same kind of "lobing" in freq resonse caused by drivers being mounted far apart on baffles. Yes it is room position sensitive. My point was to consider the WORST CASE lobe situation, which is happily the only one easily corrected.

Thank god I can at least hear the difference when I change a crossover cap from 2uF to 1.68uF, moving my tweeter roll-in from 10 khz to 12khz. And that I learned enough physics at Rider U. to understand the concept of constructive/destructive interference as it applies to sound waves. ANYTHING that changes the LCR characteristics of a "circuit" will modify the phase relationships. At what point is it audible? Moving the aforementioned tweeter operating at 10 khz. forwards or back about 0.68 inches will ABSOLUTELY create a 180 shift. If the mid and tweet were in phase prior to the movement, almost total cancellation will occur at the new position. So somewhere between perfect phase alignment and 180 out, a point is reached where "even ears dulled by the abuse of garbage masquerading as music" will notice the change. In light of that INDISPUTABLE physical fact, would not a rational person at least acknowledge the possibility that cable induced changes might be audible under SOME circumstances. Branding something as snake oil cause you don't know the math is a "flat earth" attitude. How you can decide for others what they do or do not hear must be an amazing skill. Especially how you are certain Dunlavey must be right, but someone else is wrong. Even if someone if "totally wrong" with their system setup, if they enjoy it, that's the bottom line. I hate to use tone controls, my brother used to enjoy his. Who am I to say "don't turn that knob". My caveat to cable buyers would be not to assume that just cause it costs a lot it must be better.

I listened to my vintage EV systems for two years with the horns VERTICAL,tweeter on the left, mid on the other side of a 15 inch woofer. Moving the horns to above the woofer, mounted HORIZONTAL (like a "la scala") made a huge improvement in imaging. Vocals and instruments that belong in the center stay there, even when moving about the room. Reflections from the floor and ceiling were greatly reduced, and with the mid and hf drivers so close together, the effect is almost like a "point source". No way is turning a speaker on it's side, woofer to the outside and tweeters to the inside, going to make a beneficial change. Think about the time phase differences being created by such an inappropriate configuration! EV claims 180 degree dispersion patterns with the T-35(K-77m in klipsch speak), and with my rat shack meter the 180 seems to be along the long axis of the horn. So horizontal horns spread out along that plane. The vertical way means much of the dispersion is towards the ceiling and floor, greatly increasing reflections that might be misinterpreted as a "good" thing. I think that true "physics" diffraction is not at work here, although the T-35 horn was called a diffraction horn.

To me phase coherence can be illustrated by listening to quick, short duration, impulsive types of sound like a drum stick being tapped on the rim. Any two drivers reproducing the same sound may interfere with each other in a destructive(180 out of phase) or constructive(in phase) manner. If you take any two identical wave forms, and superimpose them perfectly two things will occur...the output will increase, and the wave shape will remain narrow. Let the phase difference between them increase, and the "peak" will be reduced and the base will spread out. At 180 degrees they cancel completely. Transient signals by their nature are short duration, and lack of coherence will "smear" the audible output of the speaker system. At the 10 khz point where my K-77m's come in to bolster the falling high end of my Altec drivers, swapping the polarity of the tweeter OR moving the tweeter baffle forward/back about 0.68 inches made an easily detectable difference in the character of this type of sound. What you want is the peaks and troughs to be in phase as much as possible in the region where the two drivers are operating "together",i.e. at the crossover frequency, to prevent destructive interference from "smearing" the transients. Obviously any phase shifts caused by crossover components are going to effect the phase of the signals being passed, but by physically moving one driver in relation to the other and listening closely, a sharper "focus" to tics(drum sticks) and pings(chimes) will be heard.

I think the comment about how a speaker or other interconnect wire may effect the transfer function of the circuit in question is valid. This months issue of AudioXpress had a picture of a 20 khz input as distorted at the cable "output". If a square wave gets "rounded off" slightly, isn't that distortion? And aren't some amplifiers load sensitive? The LCR characteristics of cable that are constructed differently MUST be different, the degree to which this "distortion" might be audible is the big question. Personally I prefer to minimize R by going to larger size wire, and intuitively feel that the current "flat" cable types with widely separated conductors would minimize L and C. The current "Belden" wire craze makes me think...excessive shunt capacitance...high end roll-off?