Round Tractrix

[Guest David H]

I'm not sure that instrumented measurements can yield better results in practice.

Cask05, you make an excellent argument.

We are going to have to agree to disagree on this one.

Dave

[djk]

"didn't Mr Klipsch do a blind test in which he had an audience sit in front of a curtain and behind the curtain there was some driver movement to determine if the audience could tell a difference and he concluded that they could not. is this another version of the old saying my imagination is my reality."

Not all people that were there would agree with PWK, many disagreed. And it wasn't a blind test (from what I was told, I wasn't there).

" If I warm up my car on a cold day before taking off it will run better."

Mine does. I wait till the lifters stop making noise, and it comes off fast idle.

" if I warmup my stereo before I get into serious listening mode it will sound better."

I've had that too. I had a Mark Levinson amplifier that had no stereo image until it was on about 30 minutes. Or course some tube gear takes even longer.

" If I move drivers around, it will sound better."

I can demonstrate it.

[Al Klappenberger]

Nat,

I have the old Klipsch bibliography of articles published by PWK. I think the test he did by moving the high section around is described somewhere in there. I just need to dig it out and look for it. That requires getting the lead out of my butt though. That's a tall order!

The experiments you suggest all assume that even 48 dB / octave is a high slope. That's still rather gradual for what I'm thinking would be needed to really isolate "double exposure" from complex component overlap between drivers (phase errors BETWEEN components). The extreme-slope networks that have had the reactions of truly opening the stereo image are zero-placed filters which have slopes of over 100 dB / octave down to about 20 dB attenuation increase more gradually slowly beyond that. Crossover frequency should be where we normally cross to the tweeter, about 6000 Hz. I think an experiment where a tweeter connected to such a filter is moved to and from the listener by a second person might be valid. I believe the listener should be blindfolded during the test so that he is relying on his hearing, not visual clues though. The program material used is an open question in my thinking however. I suspect it should be something with a lot of high frequency content. A female vocal, or maybe a violin solo. I generally try to think up some sort of continuous instrument generated sound for tests like this, but in this case I don't know what that would be. Whatever the choice of program, it would need to of short duration and repeated from the beginning each time the tweeters (both of them) were moved.

My obviously biased expectation here is that the listner will be hard-pressed to hear any difference except for more highs as the tweeter is moved closer. They should get louder.

This sort of testing is not simple!

Al K.

[Chris A]

Configuration A: ...(very easy to do if you are using a DCX2496)...18 dB/octave Butterworth shapes and requires the -3 dB points to be separated and the measured delays to be shifted. It's all in that link including square-wave responses.

Configuration B: use the steepest slopes supported at each crossover, for example 48 dB/octave Linkwitz-Riley using the same crossover frequencies.

I haven't tried this for my center tri-amped Belle, but I can say that approach "A" isn't very applicable to my fronts--which are 2-way speakers. Their crossover frequency is in the range of 450 Hz.

Actually, config "A" has already been done at its only crossover point using the settings that Roy has for the 2-way Jubilee. I can describe the 2-way Jubilee soundstage in terms of commercial movie theater sound systems (...not surprising since the KPT-Jubilee 535s are currently marketed as movie theater speakers...).

Chris

EDIT: The point of the above is to highlight the fact that is that it is difficult to pull off good crossover design since issues of both phase matching and driver polar distribution matching arise every time another driver is introduced. Le Cleac'h has done an excellent job of looking closer into the issue of phase matching in the crossover area, but note that it was always a design goal of PWK to minimize the number of crossovers, leading to a 2-way Khorn crossover design. That same philosophy was carried forward 50 years later when the Jubilee was designed as a replacement for the Khorn design by PWK and Roy Delgado.

[Olorin]

I also time aligned a pair of speakers but I used an active crossover to take my measurements, then I adjusted the drivers placement until the the delays were zero. Surprisingly the magnets were very close to perfect alignment. Next I designed and built the speaker boxes to compliment the drivers placement.

I would think time alignment by ear would be no more than a guessing game, however magnet alignment seems to have some relevence.

Dave

I'm fortunate enough to have heard those speakers. They sound niiiiiiice.

[Guest David H]

I'm fortunate enough to have heard those speakers. They sound niiiiiiice.

I forgot you had a chance to listen to them. Thanks, I am pleased you like them.

Dave

[Greg_M]

To compare the shortened 1 inch horn to the proper 2 Inch horn, I did the example again for a 2 Inch. It looks similar. There is a slight change in cutoff frequency though.

Al K.

Obviously I am getting here very late in the conversation but by this chart it looks like the whole horn is only 3.451" over all from mouth to throat? Maybe I'm reading it wrong? In the finished pictures it looks deeper?

Maybe the dimensions got changed later?