Weekend Reading 7/11/2008

[jtkinney]

Someone brought up three channel playback of two channel recordings. Here is another artlcle by Mr. Paul on that subject.

Enjoy

01166223.pdf

01166223.pdf

[Daddy Dee]

Thanks JT

[WMcD]

Thanks JT, from me also.

This paper was not included in the collection of Klipsch Papers which I ordered from Hope many decades ago. Perhaps it was in collections which others bought at other times.

Footnote 12 is of interest. Sometimes people point out that very recent Klipsch crossovers for the Heritage series do not use auto-transformers. This is seen as somewhat a departure from the wisdom of PWK as set out in The Trouble with Attenuators where L pads are shown to be inferior. (A search should find this. I posted it a long time ago.)

But FN 12 is a bit of a backtrack, at least at the time of publication of the subject article..

The following is the result of me making a close reading. (Others may disagree) It seems to me PWK is in FN 12 maintaining his dislike of "constant impedance" L-pads. Those will maintain the impedance the crossover ahead of the L pad "sees." But it messes up the driving impendance the driver sees looking back into the L-pad. It is too high.

He is backtracking a bit and is saying that an L-pad can be designed so that the impedance looking back into the pad is 4 ohms (somewhat lower) and this is acceptable for 16 ohm drivers. Part of the issue is that the acoustic horn provides acoustic damping.

I wonder if PWK did not reverse himself again in later days. The Forte-Chorus-Quartet line uses an autotransformer. It was my thought that he must have insisted on it and he still had enought control over the design to prevent others involved from going with a fixed L-pad even if optimized per the possibility mentioned in FN 12.

And now with recent designs, we're back to FN 12.

Wm McD

[Erik Mandaville]

This discussion of attenuation has been a curiosity for me for years. There have been those who made very significant alterations to Mr. Klipsch's original designs in the way of using completely different midrange horns and drivers (same for the tweeter) -- elements that arguably would alter PWK's original voicing of the speaker. However, replacing that single element of the crossover has been considered a sort of 'out-of-bounds' area in terms of another, in my opinion, less impacting and traumatic modification.

There are so many equally well-known loudspeaker makers and designers -- I've used Altec and JBL as examples in the past -- that use resistive L-pads in their designs, most often the variable type (which once set in the desired position are in fact 'fixed') that doubtless were aware of Klipsch's work on this subject. That gross alterations of horn and driver have been accepted as valid modifications to PWK's and the autoformer-to-fixed L-pad generally not is a mystery to me.

Others have said that Klipsch, due to its significantly higher cost, no longer uses the autoformer because they prefer to focus on maintaining a profit. What are the implications of such a statement? That they no longer care as much about performance? Perhaps it's because it was found that what the autoformer contributed in terms of what can actually be heard was not great enough, or in fact was found to be inferior to fixed resistor attenuation. There are loudspeaker designs costing exponentially more that rely on fixed resistive L-pads.

That it's okay on the one hand to toss out the drivers and horns that PWK worked so hard to develop yet oppose, often rather strongly, the simple change to a fixed L-pad is something I continue to try to understand.

Maybe there are other aspects of loudspeaker design more worthy of this sort of time and energy. With a little DIY ability and interested personal research, one can put oneself in the position of making a personal choice -- just as a personal choice can be made concerning the use of, for example, 511-B squawkers and JBL tweeters.

Thanks for the link!

Erik

[Erik Mandaville]

For the record: There is nothing wrong in the least with using horns and drivers from other companies than those originally designed and put into use by Paul Klipsch. I merely used that as an illustration and an example. I've had that opportunity, too, and agree that the 511 B is a nice sounding horn. I used it with a La Scala for center channel use for a time.

Erik