dBspl

Yep, that's it. Thanks for posting. This should go without saying, but the whole article is tongue & cheek. It was just to highlight the absurdity of the idea that constant impedance and high power handling are required for good sound reproduction. This completely goes against everything that PWK believed. A couple of the footnotes in that article are hilarious. Kerry

There's another Dope from Hope article that ridicules the whole idea of constant impedance loudspeakers. I believe it's called "The Ultimate LSH Loudspeaker". There's nothing like good PWK satire! And I can also confirm PWK spent a lot of time in his later years developing extreme high slop passive filters. Kerry

It's just a crude estimate based on a midrange impedance of around 30 ohms and a shunt resistor of around 8 ohms. The loss would be significantly higher on a product such as a Heresy where the midrange impedance approaches 100 ohms. Kerry

Does it seem bizarre to anyone the solution to this problem is to shunt power through a resistor in the midrange circuit? Of course it depends on the size of the shunt resistor, but in the case of the Klipschorn, you would basically have to generate about 5 watts just to generate one watt in the compression driver (4 watts will be dissipated by the resistor as heat). You have already cut the midrange efficiency to 20% just by going through the network. Does it really sound like a good idea to dissipate that kind of power through the network?

By the way, nice Dynaco ST-70 in the background of that picture.

This isn't quite right. The KG1 came well after Gary Gillum left the company. Gary introduced the KG2 & KG4 (although the KG4 isn't a bookshelf product). The KG1 was introduced around 1990, and was one of the first products introduced after the sell of the company to Fred Klipsch. Fred's wife Judy was the inspiration for the KG1, and also the architectural products that soon followed. Kerry

According to that Behringer spec, the noise floor of the microphone is 32 dBA. That's pretty high for background noise measurements. It will probably be difficult to resolve noise levels below that. Kerry

I'm not aware of a multi-meter that measures ESR, but I haven't really made an effort to look. I have a Peak Atlas ESR meter that does happen to measure capacitance and resistance, though. But it really doesn't replace a good multi-meter because the meter has very limited capabilities in that regard. The one nice thing about this meter is that it measures capacitors in-circuit. Kerry http://www.mcmelectronics.com/product/72-9912?green=59978692-BE3F-57BF-B27F-54BC7A8A9EA2

Being so close in serial number, it is plausible the veneer panels were cut from the same timber. That would help ensure the pair still had similar grain pattern and color. Kerry

All Heritage product should have sequential serial numbers. The label on the packing carton should even call out the serial number of the speaker that it's matched with (serial # XXXXXX1, match with serial # XXXXXX2). The speakers are grain-matched. In other words, the left speaker is virtually a mirror image of the right speaker. This is why the speakers have sequential serial numbers - so they can be kept together (easily) through the factory, as well as after they leave the factory. One reason why this is important is because real wood veneer (especially exotic wood veneers) will vary dramatically in grain pattern, texture & color. Matching the wood grain makes a distinct improvement in the perceived beauty of the product. Kerry

Here are a few more nice shots. Pricing is as follows: Special Addition Heresy in California Black Walnut: MSRP $3,200 pair Special addition Heresy in East Indian Rosewood: MSRP $3,200 pair Special addition Cornwall in California Black Walnut MSRP $6,000 pair Kerry

The K-400 and K-401 are the same horn design. The 400 was die-cast aluminum, whereas the 401 is injection molded. I believe the 400 horn tool had worn out, and the decision was made to move it to an injection molded (plastic) horn. I know Jim Hunter was responsible for putting the K-401 into production. Don Keele wouldn't have had anything to do with the development of either one of those horns. The 400 was well before, and the 401 was well after, his time at Klipsch. Miketn, I never met Richard Heyser, but I'm a fan of his, too. He passed away about 7 or 8 months after I started with the company. I still remember the day PWK's assistant got the message he had passed, and was on her way into Mr K's office to give him the bad news. Kerry

I doubt I'm going to give you the king of answer that you're looking for, but here's my perspective with regard PWK and the Klipschorn. Most of the (interesting) history happened before Roy or I (and even Hunter) were around. I do think his criteria and priorities were pretty well stated in everything he wrote on the subject, though. And you didn't have to be around PWK very long to realize that's exactly what he believed. He was pretty much: This is the way it is, and if you want challenge that - you'd better have the facts AND data to back it up. A good example of this is that he never really accepted the Tractrix horn until he read a PhD thesis comparing an exponential horn to the Tractrix. Nevertheless, the Klipschorn had already matured in its design by the time I started with the company. Only the occasional refinement were being applied throughout the early years of my employment. However, PWK did want a 2-way solution for the Klipschorn. And he did continue to experiment with new horn & driver designs during the time I was there. I got the opportunity to run the data on several of his experimental horns. He had abandoned the original 2-way design (and eventually the K-5-J horn) during the late 50's because he couldn't get the extended high frequency response necessary. Using the tools that we have today, it really isn't that difficult. But in those days with the limitations they had in equipment, it was probably out of reach. With the switch to the 3-way design, and the introduction of the K-400 horn, the Klipschorn had achieved a level of performance that it would only require the occasional refinement after that. But apparently, the 2-way design never left him, because it was a fairly big deal to him during the time I knew him. PWK didn't seem to care for the original K-5-J horn. The K-5-J is essentially a constant directivity horn design, which does require significant equalization for a flat response. I know that was a factor, but he may have also had an issue with how the radial horn mouth set-back into the cavity of the HF section and the issues that brought with it. The K-400 horn solved all of this. The horn had a flat mouth and easily mounted to a baffle. The horizontal coverage is fairly consistent at 90 degrees, but he did sacrifice vertical coverage to improve horn output at higher frequencies. This is the self-equalization characteristic that compensated for the driver's rolled off power response. This was the technique he seemed to prefer. I say this because the experimental horns he later designed still used this approach. Now, I do seem to recall the one horn design he was leaning toward did have flat sidewalls angled at 90 degrees. This was more similar to the K-5-J, but the vertical was all K-400 style. We did continue to experiment with the LF section, too. But PWK was fairly comfortable with the LF design and didn't get too involved in those experiments. Kerry

Yea, I should have been more careful with that statement. In the passband of the midrange, it is significant. The K-400 is essentially a self equalizing horn design. The 3 or 4 dB per octave gain in directivity (decreasing vertical coverage) accounts for the flat on-axis frequency response. I was just saying that once you get above the compression driver's cut-off of 6kHz, the attenuation is so fast that even though the horn directivity will continue to increase, it really isn't increasing fast enough to have any meaningful impact on the frequency response. Kerry

Yes, the K-55 exhibits a band-pass response. At least in the earlier Khorns, the high-pass is dominated by the electrical high-pass filter, whereas the low-pass is dominated by the acoustic filter characteristic of the phase plug. The phase plug transfer function is pretty aggressive, and it relies on constructive & destructive interference to give you a net result. This isn't a bad thing, but it does make the phase plug sensitive to small changes in assembly & design that will effect the region just above and below cut-off. I suspect that's why all the different manufacturer of this driver over the years seem to exhibit slightly different frequency response characteristics in the 3500 to 6000 Hz region. With regard to the rising directivity factor (narrowing coverage) of the K-400 horn; I really don't think the gain is enough to matter. I haven't looked at the DI in a long time, but I doubt it rises more than 3 or 4 dB per octave, but I could be wrong. On the other hand, you do have other things working in your favor, such as the mass of the diaphragm, and the inductance of the voice coil. Kerry

I never really understood why the early Belle's didn't utilize a low-pass filter in the woofer leg, either. I was told it was because the woofer horn had trouble getting out to 500 Hz - which is true. However, it also had a very shallow roll-off which resulted in a wide crossover interference band. The solution is to add Q to a low-pass filter to boost the region just before cut-off. I believe this was eventually done. On the other hand, I don't see why the absence of a low-pass filter on the mid-range (I think that's what you mean) is necessarily bad? The K-55 cuts off really hard. As long as the output is attenuated enough not to cause interference with the tweeter output, what's the harm? Kerry

Special Edition Heresy III in East Indian Rosewood. Kerry

Thought I would post a couple of pictures from out recent photo shoot of our 70th anniversary & special edition Heritage products. The two photo's below are of the special edition Cornwall III in California Black Walnut with a vintage Lambswool grille cloth. They will begin shipping in October. This special production run will be limited to around 70 pair, although future production runs are possible. I'll post photo's of the other products as they become available. Kerry

All Heritage models are currently sold with sequential serial numbers. It is primarily done to ensure the grain matched enclosures stay together. The carton label on the product will list the serial number of that particular speaker, and also the serial number of the speaker it is matched with. The dealers (and distribution centers) are aware of this, but unfortunately it isn't enough to keep speakers from being mismatched from time-to-time. If I remember correctly, Quartet, Forte & Chorus's were all grain matched, but KG series speakers were not (maybe Kg2's & Kg4's were in the beginning). It's no small task to build a pair of loudspeakers that are virtually identical. Literally, the veneer leaves have to be kept together form the point they are sliced from the tree, and then all the way through the production process. The most costly issue you have to deal with is that if one speaker is damaged during construction, the pair of speakers has to be culled. Fortunately, it doesn't happen very often - but it does happen. Kerry

PWK use to say speaker design all boils down to moving furniture. If you've ever done it, you know the truth in that statement. Kerry

While I guess that is possible, I don't believe that was the case. It also doesn't seem logical that you would attenuate the mid-range 1.5 to 2 dB and leave everything else alone. However, I also never really understood how a deviation of 1.5 to 2 dB over the entire pass-band of the K-55 driver could happen. That's going beyond normal production tolerances. I would have to look, but I seem to recall the changes from the AK-2 to AK-3 were relatively modest value changes. Kerry

I was involved with the move to the AK-3 network. Of course that was a very long time ago, and I'm sure I don't remember all the facts. I had only started with the company in 1986, so it was never perfectly clear to me the events leading up to the AK-3 network change. So my comments may only add to the confusion. My recollection is that when the AK-2 was introduced, it was accompanied with a K-55 driver change. I want to say we changed suppliers, but I'm not positive. Again, this all happened before me, but my understanding was that when the new K-55 engineering samples were measured they were about 1.5 to 2 dB hotter than the old K-55. When the AK-2 network was designed, it was based around these hotter drivers (resulting in more attenuation in the mid-range network). This is what was implemented into production. However, at some point down the line (and I don't know when), it was realized that production drivers where not as sensitive as those original engineering samples. This must have been around the time I started because I do recall there was growing concern over a period of time that something needed to be done to correct it. At some point I was asked to take a look at it, and also work with Hunter and John Allen to confirm any changes. This resulted in the AK-3. Well, if nothing else, it's something else to chew on... Kerry

I'm not sure I follow everything in your post, but I would care to guess there's a lot of stuff going on that's going to effect the result. At the very least, I would point to the phase relationship between the woofer and midrange. This will dictate the amount of "coupling" going on between the two drivers in the crossover band. As you change the slope of the woofer filter, the phase relationship of the two drivers will change (relative to each other) such that the combined output will vary according to whether the drivers are "in" or "out" of phase with each other. dbspl

Although this isn't always the case, the stated frequency response is an accuracy specification and therefore its purpose is to establish just that, rather than reflect the useable bandwidth of the system. Plus or minus 3 dB is a typical tolerance window, although it's not unusual to see a variety of others. An accuracy specification isn't very accurate at capturing the useable bandwidth of the system (particualrly low frequency extension), because output as much as 10 dB down is still considered audible. For this reason, the low frequency extension is usually broken out separately. dbspl

I believe the Hickok vacuum tube testers are the most sought after. I've considered buying one myself (although I have never actually used one). One in good condition starts to get a little pricey. dbspl