g3dahl

Oh, yeah, I forgot about that unusual configuration. I went back for a look and see what you mean. Only two 2-uF caps for a 3-way crossover! Clever design, and a pretty lucky situation if you're replacing caps. Personally, since you can do all three channels with six caps, I would just go for the Hovlands and be done with it. $14 for the 2 uF Hovlands is an excellent deal. I use the same caps in the tweeter section of my modified Chorus II's, and am very happy with them. If you want to proceed more cautiously, consider buying three Hovlands, then use one Hovland and one Zen in each speaker. Put the Hovland between the input and the autoformer, and the Zen between the autoformer and the tweeter--that way, you're using the best cap in the position that influences the signal going to all three drivers. Or, for maximum bang-for-the-buck, just put a couple of Zens in your new center-channel speaker. You can't go wrong, because you know you like the sound already. But above all, make sure all three crossovers are done the same way. Have fun! Gary Dahl

You might check the forum at: http://www.hometheaterspot.com Gary Dahl

If you like the sonic "flavor" of the Zen caps in your system, then I suggest that you use the same ones in your center channel. The difference between the sound of the Zens and the Hovlands is most likely smaller than the difference between either and what you replaced. Also, it is highly desirable to match the front and center channel speakers as closely as possible, so you don't want to introduce a different flavor in the center. The Hovlands are more expensive because they are built with film and foil construction rather than metallized film. North Creek (the distributor of Zen capacitors) also offers film and foil caps under the name "Crescendo". They are priced more comparably to the Hovlands. Film and foil caps are certainly excellent, but not always better than a good metallized cap. I have used (and continue to use) Hovlands, Auricaps, Zen and Crescendo capacitors in various locations. If you want to experiment with Hovlands, a good starting point would be to just replace the tweeter capacitors; that is where the difference will be easiest to hear. If you really like the way they sound, then you can move on to the mid if desired. For the woofer section, an inexpensive metallized film cap will work just great. Gary Dahl

---------------- On 9/9/2003 6:40:50 PM wrench_peddler wrote: Question 1. Is it bi-wiring when you run 2 leads to the speakers, One for the lows and one for the highs, both from the same source? Yes. Question 2. Is it bi-amping when you use two amps, one for the lows and one for the highs? Yes. Question 3. Is a bi-amped speaker also bi-wired by default? Yes, but the term "bi-wired" is normally only used as you described in Question 1. As for bi-amping, there are two ways to go about it: Passive bi-amping: Using two amps, one for the lows, and one for the highs. The crossovers (passive) are in the speakers. Active bi-amping: Using two amps, one for the low, and one for the highs. The crossovers (active) are ahead of the amps, so the amps' outputs go directly to the drivers. Gary Dahl

Hi kh, The name "Aloha Audio" made sense at the time, because it was a partnership between Hiroshi Ito (who lived in Honolulu) and Lynn Olson (who lived in Aloha, Oregon). Lynn started the name "Nutshell High Fidelity", back before his Aloha Audio days, for the purpose of distributing his book, "The Soul of Sound". Aloha Audio began when he and Hiroshi decided to start importing Danish Audio Connect (DACT) attenuators. The "Nutshell" name was the result of a conversation between Lynn and his brilliant wife, Karna. He had been talking about the concept of designing the speakers and amplification chain as an integrated whole. She said something about that being his whole philosophy in a nutshell, and ended up suggesting that as a name for his business. Lynn and Hiroshi dissolved Aloha Audio near the end of last year. The replacement has been Nutshell High Fidelity, with a return of the old name. It consists of Lynn and me. We import DACT, and plan to eventually sell amps and line stages of our own design. It really doesn't rain all that much around here, less than in Seattle. It's more of a myth, actually, though there usually is a long stretch of gray skies through the colder part of the year. Gary Dahl Nutshell High Fidelity http://www.nutshellhifi.com

Interesting thread! As it turns out, Allen Wright, the other VSE guy, is coming out from Germany in about three weeks to attend VSAC here in Silverdale, Washington, where he will be a guest speaker. His seminar will be on the topic of push-pull amplifier design. He also will be bringing his new amps that he is bringing to the show for their debut (not the Rasmussen design you have been discussing). He will also be bringing his amps to my house to compare with my Lynn Olson-designed Aurora/Amity amps (see http://www.nutshellhifi.com/triode1.html). Lynn Olson is my partner in Nutshell High Fidelity (formerly Aloha Audio), lives here in Silverdale, and has recently begun to participate in the Klipsch forum. If you have questions about how to reconcile his writings with other pieces of information you run into, just ask...I'm sure he would be happy to explain further. If you have questions about the Rasmussen stuff, maybe I can pry some info out of Allen. I'm sure he's well versed in it. Gary Dahl

---------------- On 9/6/2003 1:58:07 PM fini wrote: Thank you, Gary!! Have you gone in the past? Sounds like a good place to get an education. I plan on tasting Sonoma County's finest at the Harvest Fair, happening that same weekend. Anyone need corks for their Cornwalls? I can already taste that Dry Creek Zin... fini Hi fini, Sounds like a good time! As a matter of fact, I've been to all three of the VSACs. What I didn't know when I went to the first one was that by the time the second came around I would have moved to Silverdale! It wasn't the reason I moved here, but it is handy living less than two miles from the venue. The strange thing is that any time I happen to walk into the Silverdale Red Lion Hotel, a part of me expects VSAC to be going on... Hope you can make it next time, it has been growing steadily and this year's VSAC has actually outgrown the hotel! I'm not sure if the next one will be in Silverdale, though. Gary Dahl

Biwiring most certainly does make things better. Have a look at: http://www.geocities.com/jonrisch/page8.htm The graph that the above URL leads to shows a rather dramatic difference. I recommend backing up to the home page and exploring the many fascinating articles on Jon Risch's site. The index page is at this address: http://www.geocities.com/jonrisch/index.htm Have fun! Gary Dahl

---------------- On 9/6/2003 12:22:51 AM fini wrote: What/who/where the Hell is VSAC? fini ---------------- VSAC is "Vacuum State of the Art Conference", October 3-5, Silverdale, Washington. Details can be found at http://www.vsac2003.com. This will be the fourth VSAC; they have been held at 2-year intervals. Seminars will be led by Allen Wright of Vacuum State Electronics, Bruce Edgar of Edgarhorn, and Charles King. Exhibitors include all kinds of tube-related companies and high-efficiency speaker makers, such as: Bottlehead Welborne Labs Modwright Firefly Audio Progressive Engineeering MagneQuest Exemplar Audio Lowther America First Impression Music Wright Sound DIYcable Consonance Adire Audio Iconic Manufacturing Cain&Cain electronluv Jena Labs Bent Audio Hagermann Technology LLC Teres Audio The Bolder Cable Company Galibier Design K & K Audio Aliante loudspeakers Amazon turntables Audion tube electronics Audist loudspeakers Cadence Audio Edison tube kits Nightingale tube electronics Revolver loudspeakers Royal Device loudspeakers Experience Music Edgarhorn Rethm Loudspeakers Omega Speaker Systems Experience Audio Tubeseller.com Solar Hifi GR Research Sun Audio & Two Bald Guys Audio Cardas Audio Hudson Audio Audio Amateur Corp. Oris Horn Diversity Records Harmonic Design Works Redpoint Audio Design Gary Dahl

---------------- On 9/4/2003 4:08:49 PM PAR69 wrote: Another option might be to change the phase of the Cornwall woofer by swapping the leads off of the crossover (positive to negative/negative to positve). Any one see a problem with this? Paul ---------------- Yes, there would be a problem. Reversing the leads between the crossover and the woofer would cause a response null at the crossover frequency. The relative polarity of the drivers is part of the crossover design, so you can't change it without redesigning the crossover. Kerry, if it were my system I would reverse the polarity of the Cornwall, as you did. The idea is to connect things so that the listener receives the same part of the waveform from all three woofers. Because of the longer path length in the LS's, this is achieved with the Cornwall (or both LS's) connected in reverse polarity. Gil is probably right, though, about it not being terribly critical in this application, as PWK wrote. You should feel comfortable making your final decision by ear. The answer might not be particularly clear, because the phase relationships between the mids and tweeters will be all over the place anyway. I would base my decision on the woofers, which are covering the frequency range in which the ear is most sensitive to phase relationships. Gary Dahl

I have now had the opportunity to listen to the Chorus II's with the completed modifications. The results are fabulous! Wow!! The flatness of the frequency response is immediately obvious when listening to music. There is a beautiful transparency, a very strong "you are there" sense. I have never heard a horn system that was completely free from audible peaks and resonances, especially when listening to orchestral music. Strings are *really* hard to get right with horn systems (or even with direct radiators, for that matter), because any such peaks or resonances, or bits of distortion, destroy the delicate balances that allow strings to sound like they do in real life. Last night when listening to the Telarc SACD of Berlioz' Symphonie Fantastique, I was treated to the most sublime orchestral reproduction I can recall. During dense passages, the tone colors of individual instruments were clearly delineated--the lack of any sort of glare was revelatory. The resulting sound was also quite refined. The delicate violin passages in the opening of the first movement brought goosebumps! I'm not ready to say that the Fostex tweeter offers the last word; there are some very nice units out there that I'd love to try at some point. But if it doesn't get better than this, I am already very pleased. There is also a minor hump in the midbass response that I would like to get evened out. Experimenting with placement might help, but I am also curious about how the original Chorus (vented bass reflex) alignment sounds compared with the Chorus II's passive radiator. I wouldn't hesitate to ditch the PR and cut some ports if it will improve bass smoothness. With that being said, the bass sounds quite good even with the hump. The hump is broad enough that melodic lines played in the lower ranges don't seem to move in and out of an exaggerated response area. In fact, to my ears, the bit of extra warmth makes cellos and basses sound more realistic than they often do in systems that measure "flat". This has always bugged me; in real life, lower strings make a big, warm sound, not something you would call "lean" or "tight". So...what's really right? Looking forward to more listening. Congratulations Lynn, you've really outdone yourself this time! I think you should come over tomorrow for a listen. You'll really like what you hear. Gary Dahl

I have put some time into working with DIY CAT5 cables. My suggestion: keep it simple and compact. For example, use a single CAT5 (teflon, like Belden 1585A or equivalent) for a speaker wire from one amp channel to its speaker. There are four twisted pairs inside, each pair made of one solid-color strand and one striped strand. You can either connect all of the solids to red and all of the stripes to black for minimum inductance (split pairs), or use two twisted pairs going to red and the other two going to black. Most people using CAT5 have used large numbers of strands in various braiding configurations. It is quite easy to build up to a very large capacitance while doing so, especially with split pairs. This capacitance is parasitic, and results in HF losses. With high-sensitivity speakers such as Klipsch, it doesn't take a big heavy speaker cable to do the job. If you don't believe me, open up a CAT5 and replace your speaker wires with just one twisted pair (2 x 24g!) and have a listen. See what I mean? Of course, repeating the experiment with low-sensitivity speakers will bring about different results. If you go to the effort of building a big cable out of many runs of CAT5, you might even be very pleased with the results; many folks swear by the stuff. But you might have fun trying some smaller configurations first. They're cheaper, easier to build, and will give you a feel for how the stuff behaves in your system. Good luck! Gary Dahl

One thing I didn't mention when describing the crossover circuit: the 20 ohm series resistor has been removed from the squawker. Gary Dahl

For the purpose of measurements, we placed the tweeter on top of a couple of thick books (Harry Potter #5 and The Adventures of Sherlock Holmes) and used a folded-up bath towel to cover the rest of the enclosure's top surface. Obviously this worked, because the impulse response measurement results came out very clean. Eventually, I will build a wooden enclosure for the tweeter, and try to come up with a sound-absorbent treatment for the cabinet top that is reasonably attractive. There were quite a few changes to the crossover. Going from memory: The second tweeter cap (2 uF) has an extra 4.7 uF in parallel, and there is now a 50 ohm resistor in parallel with the Fostex FT17H tweeter. The polarity is reversed, as in the original. On the squawker, the Universal 3619 autotransformer has a 10 ohm resistor in parallel (a la ALK). Output is taken from tap #1. Squawker polarity is now reversed. For the woofer section, the capacitor has been changed from 68 uF to 20 uF with a 3-ohm resistor in series. BTW, the 3-ohm value turned out to be critical. The inductors are stock, as is the first tweeter cap (also 2 uF) and the squawker cap (6 uF), though all caps have been replaced with premium-quality polypropylene films. This crossover is for the time-aligned version with the Fostex FT17H tweeter on top of the cabinet only! With the stock tweeter in its normal location, best results were obtained with different parts values...but the response was not nearly as smooth as our final version using the Fostex tweeter. Also, the Fostex/time-aligned version has much cleaner impulse response. I will post again when I have had an opportunity to listen to music! Gary Dahl

Lynn and I got together for another round of Chorus mods. This time, the goal was to see how far we could go with the stock woofer and squawker, but using the Universal 3619 autoformer. I brought the original Klipsch tweeters as well as the Fostex FT17H's. We started with the Klipsch tweeter, and the autoformer set on tap 2, which is one step lower than it would have been with the original autoformer. The tweeter crossover used stock values; the woofer and squawker were set the way they had been at the end of the Altec experiments. We had lots of trouble with the Klipsch tweeters because the joint between the terminals and the voice coil wire is easily broken. I was able to re-melt and get them working again a few times but eventually they couldn't be revived. Better to mount these tweeters and leave them be, rather than subject them to what I did! Anyway, we had already optimized the crossover while we still had a working Klipsch tweeter, and I have more diaphragms on the way. So, we turned our attention to the Fostex tweeter. By this time, we were experimenting with a time-aligned configuration, with the tweeter on top of the speaker enclosure, set about a foot back from the front panel. Once everything was dialed in, we had a remarkably smooth and flat response, far superior to our previous efforts. Now I will have to build the changes into the "permanent" (Ha!) crossovers so we can start listening to something more interesting than MLSSA test signals! Lynn will be posting the MLSSA plots when they are ready, and perhaps the schematic. The topology is mostly similar to the original, but most of the cap values have changed, and resistors are used differently. Gary Dahl

Well, we didn't have very much luck with the 290's. We tried all of the tricks we could think of to extend their HF response to a usable point, but no luck. The 311-60's were probably a factor. So, we moved on to the 288 driver. HF extension was of course much better, and after some messing around we ended up with a beautiful response curve, remarkable in fact! The finished configuration was a 2-way, with the 311-60's running all the way up. The available tweeters didn't have significant output beyond the HF limits of the 288 anyway, a bit short of 15 kHz. Initial listening tests at my house were extremely thrilling. The Patricia Barber SACD was un-friggin'-believeable! Later in the day, however, I put on some orchestral music, which is my most important test, because I am an orchestral conductor. Bad news. Upper strings were a mess. The <15kHz HF extension limit wasn't the problem, but rather the resolution and distortion level of the treble that was there. The same system that was hair-raisingly awesome with blues/jazz was unacceptable (to my ears) with orchestral strings. Hmmm. I think I was closer to what I was looking for with the Chorus II/Fostex tweeter, using the Klipsch squawker, rather than the Altec 311-60/288 combo, which was a huge surprise. The Universal 3619 autoformers are now here, which would have allowed us to dial-in the Klipsch squawker without the series resistor. I'm now thinking that the next step is to go back to the Klipsch squawker with the Universal autoformer, and to find a better tweeter. Lynn is looking seriously at the Beyma CF25, and I will too. I am also thinking of trying the later version of the K-79-K...mine had phenolic diaphragms, but the last ones used polymers. Gary Dahl

You might try Oakwood Veneer at http://www.oakwoodveneer.com. I have used their "bubble-free" veneer, which is excellent. In my opinion, it is easier to work with than plain veneer because of its consistency and the special backing paper. The top layer is real wood. They offer veneers in over 150 species of wood, from ordinary to exotic. Minimum order is a single 4' x 8' sheet, which could cost anywhere from $45 to several hundred, depending upon species. Gary Dahl

Hi djk, To make sure I follow your meaning: 1) The "simple series resistor" implies that you don't also have a shunt resistor, right? Actually, I was attracted to ALK's implementation, where there is a shunt resistor across the autoformer which reduces the driver's influence on the upstream circuitry. Are these topologies mutually exclusive? 2) "Add a filter from the input to the output" -- do you mean a capacitor between the top of the autoformer and the output tap being used, to create a shelf filter? I can tell already that I need to put together an external crossover for this project, so I can make changes easily without pulling the terminal box off the back of the speaker for every revision! Oh, one more question: When disassembling one of the 290's, I noticed the internal metal cover that provides a mounting surface for the optional 70-volt transformer. My 288's don't have any sort of hard surface this close to the diaphragm--just a felt pad on the inside of the rear cover. Do you use the internal cover, or have you experimented with alternatives? I have heard that some people even prefer to leave the back covers off! I was considering removing the internal cover and installing a pad inside the rear cover, or perhaps using the 288 rear covers instead. Gary Dahl

Thanks! Great info!! Gary Dahl

Hi Q-man, If I can cross over around 6 kHz or so, that will be great. Someone on Audio Asylum had reported that his 290's started dropping 6 dB/oct at about 2 kHz, and were 10 dB down by 7 kHz. I don't know which version it was. But none of the tweeters I was considering were usable down to 2 kHz! Right now I am using the Fostex FT17H tweeters, with the stock Chorus II crossover (about 5-6 kHz). Their recommended crossover frequency is "more than 5 kHz" according to the spec sheet. They sound to me like they would be happier with a somewhat higher crossover, or perhaps a steeper slope. I am also considering other tweeters, including the later-version K-79-K, which is said to outperform the earlier units. The 290's and the Universal autoformers arrived this evening, so new fun experiments will soon be underway. Thanks for all the helpful information and comments! Gary Dahl

Another twist here. The poor MLSSA showing by the stock Klipsch tweeter was due, at least in part, to a diaphragm compatibility issue. The night before I brough one of the speakers to Lynn's house, one of the tweeters stopped working. After verifying that its diaphragm was open, I installed a replacement diaphragm. While doing so, I noticed that the original was phenolic, but the replacement was not. The material looked like the typical black cloth that one finds on typical dome tweeters. Otherwise they appeared to be the same, but the new one didn't seem to fit as perfectly as the old. I should have paid more attention to that fact. After "retiring" the Klipsch K-79-K tweeters in favor of the Fostex FT17H's, I spent some time trying to repair the open-circuit phenolic diaphragm...what did I have to lose? It turned out that the ultra-fine wire leading from one terminal to the voice coil (it appears to all be one piece of wire) had broken next to the terminal. After a few unsuccessful tries, I finally got it spliced back together. I'll be anxious to try the phenolics once again. But when I was removing the non-phenolic replacement diaphragm, I became quite aware of the fit problem--the replacement voice coil was (slightly) binding on the inner surface of the magnetic gap! No wonder the thing was 10 dB down and had no extension! The other one was exactly the same. I called the Klipsch Parts Department. They sell the same replacement diaphragms (#127103) for all versions of the Chorus. The rep didn't know anything about diaphragm materials...but he did say that they also sell the entire driver assembly (#129102). At just $40 per piece, they might be worth a try. For that matter, maybe I should look into the later-production mid driver as well. Gary Dahl

Hi djk, Thanks for the informative post! It is certainly interesting to see how the Altec products evolved over the years. I had indeed noticed that the sensitivity specs I had quoted were taken at 4' rather than 1m. They came from the 311-60/90 data sheet, which lists sensitivity at 4' for various combinations of 311's and drivers. I just looked again...with the 290-4K driver, it says 109.0 dB in the 311-60 and 106.5 dB in the 311-90. For all the other drivers the relationship is the same: +2.5 dB in the 311-60 over the spec for the 311-90. This is consistent with theory, because the energy is contained within a smaller dispersion pattern. In any event, I'm sure I will need to attenuate my 290-8K's, and expect that the Universal autoformers will provide enough flexibility to get a good match with the woofer. Q-man has reported getting 3 dB less sensitivity with the 16-ohm diaphragms (compared with the 8-ohm), and I have been trying to reconcile that with the Altec sensitivity specs, which don't vary with impedance. Perhaps the autoformer in the Klipsch-style crossover accounts for Q-man's different results. By the way, are you the same djk who has posted on the Audio Asylum's High Efficiency Speaker forum? If so, I was reading some of your old posts last night. The subject involved using a simple resistor to attenuate the 290, resulting in enhanced HF extension. I have recently become concerned about whether the 290's will reach high enough for the tweeters I had planned to use, but I was expecting to use autoformer attenuation, for the same reasons PWK and ALK have used them. Any thoughts or guidelines? Thanks! Gary Dahl

Hi Q-man, The K series, introduced in 1979, was the first non-alnico 290. All previous units (C, D, E, G and H) had alnico magnets. The ferrite units are easy to identify, because the magnet is larger in diameter than the rest of the driver and is visible as a 1"-wide black band protruding around the middle of the driver, just ahead of the rear cover. The alnico magnets, having different proportions, fit entirely within the casting of the driver. My 290-8k's will arrive Monday. I am anxious to see if they have Tangerine phase plugs like my 291-16k's (which are really 299's because I installed 8-ohm Pascalite diaphragms). Supposedly the Tangerines help in the HF extension department. The higher the 290's will go, the easier it will be to integrate a tweeter. Altec says 7k, which would be great, but they also claim 20k for the 802/902's, which is pretty iffy. Gary Dahl

---------------- On 8/10/2003 10:03:04 AM leok wrote: Gary, Very interesting. Observing similar graphs in Stereophile reviews, I've wondered what various Klipsch designs would look like. Do you have the Chorus-IIs in a corner? I've come to consider the corner simply part of a speaker if there is a rear-firing passive element of any kind. Caps I used in mine were Jensen foil pio for the 6uF on the mids and Hovland foil/polyprop. on the tweeters. The Jensens definately needed several weeks of break-in .. they were just terrible at first. Hovlands seemed fine all along. Now, if I can just keep grunge out of my tube sockets, and no more of my expert solder joints go cold, the speakers are very clean sounding. On the K-61-K (I think that's it) mid. My Chorus-IIs are '95. My Forte-IIs are (or were) '90. Both use the K-61-K mid horn. I tried the '90 mids in the Chorus-II and they were too loud for the other two drivers (as they tend to be in the '90 Forte-II also. The '95 mids were a much better match for the other two drivers. That may accound for some of excessive mid power you found. Thanks for posting your results. leok ---------------- Hi leok, Yes, Stereophile's graphs are produced using MLSSA, just like Lynn's. When comparing Lynn's graphs with Stereophile's be sure to check the length of the sampling window--you can make the results appear much more flattering by reducing the sample length, or changing the scale of the waterfall plot. I don't have the Chorus II's in a corner. I do realize that having them against the wall or in the corner would affect the lower frequencies, and probably bring the mid into balance with the woofer (with the stock crossover). In my room, however, it wouldn't be a practical placement. Thanks very much for the info about the later K-61-K drivers. I think my Chorus II's are earlier units. I wonder what makes your later ones different...the diaphragm, or perhaps the whole driver? My K-79-K tweeters changed completely when I replaced the phenolic diaphragms with the newer polymers. Kind of frustrating; I wish Klipsch would use different designations for different parts. If it's not the same, it shouldn't be called the same thing! Gary Dahl

---------------- On 8/10/2003 10:29:04 AM Q-Man wrote: Gary, Is the sensitivity rating of the Chorus around 100dB? I find the 290 with the 311-90 horn to be a perfect match with the 104dB Klipschorns. I was surprised that no attenuation was necessary. I'm curious how the 290 and 311-60 will sound on the Chorus. ---------------- Yes, the Chorus II is rated at 101 dB/W/1m, which appears to be about right for the mid, but the woofer looks more like 98 dB. I will expect to bring everything in at an appropriate level to match the woofer. I don't know which version of the 290 you have, but my 290-8K's are rated at 109 dB in the 311-60's and 106.5 dB in the 311-90's--the narrower pattern of the '60's results in higher on-axis output, so I do expect to need significant attenuation from the autoformers. If your 290's are earlier alnicos, perhaps their output has dropped a bit over the years, and is just right to match your K-horns...in any case, great luck for you! Your enthusiasm for the 290's was a significant factor in my decision to buy a pair. I had previously owned 311-60's, and already knew they were good. I nearly bought a pair of 311-90's, but I realized that they would look pretty silly on top of a pair of Choruses! On the other hand, the 311-60's are just an inch wider than the Choruses, and look pretty cool up there. My listening room is fairly small, and I think it will be just as well to have the '60's anyway. Gary Dahl