K55M impedance, etc.

[Erik Mandaville]

True of False? The impedance of the K55M is 16 ohms.

A) True

False

We are working on a very simple way, which I've mentioned before, of controlling the output of the mid and/or tweeters by use of a constant-impedance variable L-pad. I've used these so many times on other networks I've built over the past 15 years, and thought I'd give them a try on the A networks I built. They have always worked very well in the past. One just needs to know the impedance of the driver they want to attenuate, and the rest is really easy!

I think we should do a forum tutorial on how to build a simple A network, using one's caps and coils of choice. An excellent and very useful DIY project. One can even use dirt-cheap particle board to mount the parts on, since even the most exotic wood available will do nothing for the sound.

[Erik Mandaville]

Forgive me!

I should have included: "Any help with this question is very much appreciated!" I'm doing the work for a friend, and would like to confirm the impedance of the driver before ordering the L-pads from PartExpress.

[3dzapper]

Yes Erik, the K-55 series are all 16 ohm drivers. (11.3 ohms DCR)

PWK would take you back out to the wood pile. He didn't want anyone fiddling with L-pads on his babies.

Let us know how you make out.

Rick

[Erik Mandaville]

Rick:

...I know you're right about that. If it sounds like $&*%, we can always yank them out and try something else. They haven't caused problems in the past, but all of those drivers were dynamic it type. I've never used an L-pad on a horn. My initial concern was that the impedance of the control would vary depending on the postition of the wiper, but the high wattage L-pads I've found maintain a constant 8 or 16 ohm impedance through the rotation.

If this works out, it sure would be easy to set the output level of the horn.

Thanks for your response -- and the warning!

[Tom Mobley]

Erik,

The K-55 has a reputation for having a pretty nasty impedance curve. I think I've seen stuff about it going up to 35 Ohms at some frequency range that's within its' normal usage range. I'm not sure how this would affect your project but it may very well have some downside. Maybe one of the more knowledge guys would be able to give a better idea of what's going on there.

[Erik Mandaville]

Thanks, Tom. My Lowthers have similar behavior, and have a much less even response curve than that. I use a 50ohm swamping resistor across the speaker inputs, which seems to help.

This variable L-pad really does nothing more than behave as a variable voltage divider -- just like most potentiometers. It will provide a much more user friendly way of adjusting the output of the midrange horn, and/or tweeter; and because it maintains a constant impedance which matches that of the driver, it should actually work without too many problems. But your point is well taken! What sometimes looks fine in one's imagination or on paper, may not always be the case when put into practice.

L-pads are usually installed AFTER the crossover branch in which they're installed, and the crossover point shouldn't be influenced by the control. All it will do is reduce or increase the voltage to the driver. I've used them in the past in both midrange and tweeter circuits, and never experienced anything negative. We'll see how this works out.

Thanks for responding!

Erik

[Erik Mandaville]

Tom!

I forget to mention this: The work you did on those homemade Belles was absolutely incredible!!!! Very nice work!

[Tom Mobley]

Erik,

Thanks for your kind words. The thing is actually getting close to done. I need to build the top baffle, rout it for the horns, add the grill cloth, which I acquired last week. I can build the lower grilles at some convenient time, I finshed the entire top of the bottom panel so it looks pretty nice even without the lower grilles.

Criminy, I need to build another ALK crossover. I might cannabalize the LS if it comes right down to it.

[Erik Mandaville]

Great, good luck and let us know how it goes!

Speaking of Belles and LSs, I recently had the chance to hear my old pair at the house of the friend who bought them from me. Yikes! I forgot how good those things are!

I know Cut Throat (I hope he's doing well) really loves his Belles.

Erik

[Deang]

I've been thinking about this one off and on for a few days. I hope it works, it would be a neat mod. However, I keep coming back to the #3 tap and 6.5uF of capacitance as offering the cleanest way of taming the midrange.

I've heard the DQ-10 with and without the pot in place, and it definitely sounds better with a fixed resistor instead of the pot. It'll be interesting seeing what you come up with.

[Erik Mandaville]

Dean:

What is the cleanest for you may not be so for someone else. The term 'cleanest' is itself a subjectively based evaluation. I have used different sorts of L-pads since the very early 1990s. A variable L-pad in the form of a potentiometer can be used as a starting point -- or as the final termination before the driver itself if the results are good enough.

However, if you do some research into crossover design and building -- not just Klipsch networks, but in general, you'll find that some designer and/or companies use sets of fixed resistors in high or mid-pass branches that are engaged by way of a switch. This is basically like a volume control that uses fixed resistors as opposed to a carbon-comp resistive elements. In this way, the user/listener can attenuate the output of the driver by switching between those different values of resistance -- and still have the benefit (if that's what happens to be preferred)of a fixed rather than variable resistor or voltage divider.

The capacitor would be used regardless of the means of voltage division or attenuation.

If we haven't tried using an variable L-pad instead of the autoformer in a Klipsch network, it is completely impossible to say whether it performs poorly; sounds just as good as the autoformer; or is an improvement. Speculating and wondering about something have never been good enough for me. I have to know, and trying it out is the only way I will be able to say one way or the other. Saying the autoformer is 'the cleanest' way (which is an opinion -- indeed, even if it happened to be PWK's opinion)is also speculation because it's being described as such in isolation, not in the presence of direct and recent experience with a variable L-pad counterpart in the same type of Klipsch network.

It may be terrible sounding; it may sound really good, or at least as good as the part it would be replacing.

Dean: For me, speculatiing about something is not enough because it's incomplete. Once I try it, I will know for sure one way or the other. The parts are supposed to arrive today.

Some might also say something along the lines of "If PWK thought they were better, he would have used them!" That's also just fine, but what he liked and wanted to hear might be different from me.

I'm trying to find a more simple and direct way of controlling the output of drivers to match a variety of listening prefences and room response. Turning a control is far easier, in my opinion, and gives greater sensitivity in adjustment, than using one or two different taps on the autoformers. I'm not saying it's better because I don't know that yet. I will say that it would give much greater flexibility, and if it sounds just as good -- then one has the personal choice to go with one or the other. I certainly do not expect someone else to necessarily like what I like -- just because I think it happens to be better.

Erik

[Erik Mandaville]

I'm bumping this up because I want to share a viewpoint: I think it's often that we make statements about changes or modfications in equipment in terms of absolutes -- meaning, what is the best for one person is thus necessarily the same for someone else.

I guess I have a very fundamental problem with such an approach to audio, but really anything where differing opinions may come into play. It simply does not matter, IMO, that one person may have considerably more experience in something than another individual. Experience does have something to do with the overall understanding of -- whatever the issue may be -- however it does not automatically mean that the one with greater understanding should make another feel obliged the share the same opinion. An opinion can be formed instantly, and in my opinion in the complete absence of knowledge. It can be an expression of value that very simply may have to do with, in the case of audio, liking one particular sound over another -- absolutely and completely regardless of the source, topology, output device, etc.

I think we should remain just as respectful towards the impressions and opinions of new comers to audio -- or in the case of horns, tubes, solid state, etc., as we are toward others with considerably more experience. I have seen people criticized simply because they like one kind of an amp over another -- or a tube over a transistor or vis-versa.

That, IMO, as far as I'm concerned, and in my hugely subjective opinion -- is unfair. I think it's so unfortunate that I have received emails, even recently, from guys who don't want to post or share their opinion/s out of fear of being trounced.

Erik

[Deang]

Nevermind.

[Erik Mandaville]

Dean:

I plead guilty, but I've been trying over that past couple of years to be open-minded. Some of the freshest advice and opinions (to my way of thinking)on sound quality have come from people who possibly have not been seriously involved with audio for a long time. For me, that sort of immediate and spontaneous judgement, based 100% on sound alone -- regardless of the source or circuit type -- is important. And it's important to me because it's something that isn't colored or cultivated by pre-conceived notions of what they have been told is GOOD or not so good. It's like talking about works of art with my students. As long as I've been teaching art and art history, I am continually amazed at the insights and impressions of some who have no where near the training, experience, and/or academic background on the subject than I. It's an enormously valuable thing to me, because I and everyone else can benefit from their thoughts, suggestions, and ideas.

What I mentioned above is an overt reminder to myself -- to not turn a hobby that is hugely valuable to everyone here into mean-intentioned, heated debate. It matters, but not so much that people become afraid to share ideas because of what might happen if they do.

Including myself,

Erik