JBryan Posted January 18, 2005 Share Posted January 18, 2005 I've just received a pr of Transcendent SE-OTL amps and the designer, Bruce Rosenblit suggested that the amps would like to see a 16 ohm load (or higher) from the speakers. I've also read that many low-powered amps, including SET designs benefit from 16 ohm loads. I found a pr of "ZERO" autoformers from Paul Speltz that can increase the impedance on any speaker (2X-4X) but I'm wondering if there's a easier way to accomplish what the ZEROs do at the xover and if its viable for Khorns. Is there a "best" way to approach this and what is the downside? Thanks in advance for your advise and suggestions. Have fun -Bryan Link to comment Share on other sites More sharing options...
WMcD Posted January 18, 2005 Share Posted January 18, 2005 It seems you didn't get any response. So I'll chime in. I recall that Larry Clair here uses OTL amps and likes them very much with his K-Horns. So maybe you don't have a problem. OTOH, Nelson Pass makes MOSFET based amps and has said that distortion does go up with lower impedance loads. Maybe the same with your OTL. I'd read about the Zero autotransformers in AudioXpress. I'm not sure they accomplish more than other transformers. Those being the ones from Universal Transformer in Texas which are used by Al.K. and others in their crossovers. I myself use the primary (i.e. 16-8-4 ohm) windings of a RS 70 volt line transformer. The issue, I assume, is that if you start using autotransformers, you're pretty much obviating the merits (whatever they may be) of the lack of a transformer in a tube amp. You'd like to redesign the K-Horn so that it has a higher impedance overall. You could probably substitute a woofer with a higher voice coil impedance. Sensitivity might suffer a bit. The midrange already works through an autotransformer and is not a big issue. If the woofer sensitivity is knocked down, the midrange can be too. It would take a re design. Then you could feed the tweeter through the autotransformer too. Overall. I'd say it could be done with a lot of work and fiddling. Gil Link to comment Share on other sites More sharing options...
DrWho Posted January 19, 2005 Share Posted January 19, 2005 I just wanted to chime in and point out that reducing the electrical sensitivity doesn't change the distortion characteristics of the mechanical motion of the driver at the same SPL's...I mention this to point out that reducing the electrical sensitivity of the khorn doesn't negate the mechanical efficiency of the design and is thus not a compromise at all; especially if the amp you're using goes into lower levels of distortion as well. I hope that makes sense; I didn't explain it very well, but I know what I'm talking about Link to comment Share on other sites More sharing options...
JBryan Posted January 19, 2005 Author Share Posted January 19, 2005 Thanks guys... The K-33 is my main concern as it can dip as low as 5ohms which may put a strain on an OTL amp which likes to see higher impedances. Putting an autoformer in front of the xover seems like an easier solution to changing speaker components and it would show the amps a higher load and increase the damping factor. As I understand it - the drawback is a loss of sensitivity and possibly more roll-off in the higher frequencies. Since the Khorn already has an autoformer in the xover, the benefits of OTL are already compromised so another transformer in the chain shouldn't have too profound an effect on the signal. I have a xover built by Al K that maintains a relatively stable 8 ohms to the drivers as well as a couple of his #3619 autoformers and a box full of caps, resistors, etc to complete several type A xovers. I was hoping that one of the gurus out there knew of a quickand inexpensive way to bump the speakers to 16 ohms. Paul Speltz's Zeros are an interesting option but too expensive for this experiment. Thanks again and have fun -Bryan Link to comment Share on other sites More sharing options...
D-MAN Posted January 19, 2005 Share Posted January 19, 2005 The mechanical resistance caused by the Klipschorn - bass horn loading makes the K33E "look" as if it is a 16 Ohm voice coil to the amp (this per "Building Speaker Enclosures", Badmaeff and Davis, Sams Publishing, Chicago, 13th reprint 1978). That's why its 4 Ohms rated in the first place, to keep the load down to a reasonable level. It in combination with the other horns used in the 3-way configuration is nominally considered a total of 8 Ohms, but that rating, as with all speakers, represents a rather "hopeful" average. I would guess that you would not have a problem driving it with an OTL design, as the resistance of the load varies widely with any speaker. Horns are especially resistive (reactance is higher), which tends to decrease the wide fluctuations in variance compared to other speaker types. This would represent an easier load to drive for a transformer-output, and seems that it would also benefit a OTL design that is particularily sensitive to impedance fluctuations. DM Link to comment Share on other sites More sharing options...
Colin Posted January 19, 2005 Share Posted January 19, 2005 One) where did you see a linear impedance chart for the Khorn I tried to search for one, but could not find one posted here (I do think it goes to 5-ohms, but also has a peak near 30-phms)? Two) I thought ALKs were a steady 4 or 6-ohms? Three) The hopeful average impedance is very misleading to us blondes no wonder amplifier and loudspeaker matching is considered a craft, few of us have the actual performance measurements to properly match the two together. Four) How are Horns are especially resistive (reactance is higher), which tends to decrease the wide fluctuations in variance compared to other speaker types? (I thought Khorn impedance curve looked just as wide as others.) Link to comment Share on other sites More sharing options...
k2dx Posted January 19, 2005 Share Posted January 19, 2005 I recall seeing the kHorn listed as one of the suitable speakers on the Transcendant site. The amps are fine seeing 8 ohms but the power does increase with 16. At least that is what I recall. Check his website. There's much info there, and helpful people (in addition to the proprietor) on the forum. BTW, vintage kHorns are stated to be 16 ohms....different drivers/crossovers though.... Post your results please... 1 Link to comment Share on other sites More sharing options...
D-MAN Posted January 19, 2005 Share Posted January 19, 2005 ---------------- On 1/19/2005 4:26:55 PM Colin wrote: One) where did you see a linear impedance chart for the Khorn – I tried to search for one, but could not find one posted here (I do think it goes to 5-ohms, but also has a peak near 30-phms)? Two) I thought ALKs were a steady 4 or 6-ohms? Three) The hopeful average impedance is very misleading to us blondes – no wonder amplifier and loudspeaker matching is considered a craft, few of us have the actual performance measurements to properly match the two together. Four) How are “Horns are especially resistive (reactance is higher), which tends to decrease the wide fluctuations in variance compared to other speaker types?” (I thought Khorn impedance curve looked just as wide as others.) ---------------- Don't know about #1. #2 the answer is ALKs = a more consistant 8 Ohms depending on the swamping resistor, if I remember correctly - I could be wrong here. #3 the answer is YES (?!) #4 horn loading places a higher than "normal" air resistance to movement on the cone, lessening excursion, and less excursion means less variation. DM Link to comment Share on other sites More sharing options...
JBryan Posted January 19, 2005 Author Share Posted January 19, 2005 "I recall seeing the kHorn listed as one of the suitable speakers on the Transcendant site. The amps are fine seeing 8 ohms but the power does increase with 16. At least that is what I recall. Check his website. There's much info there, and helpful people (in addition to the proprietor) on the forum." The SE-OTL sounds fine with the Khorns and it was a benefit to strap them as monoblocks. The power went from 1.5w/ch to 4w/ch and the damping factor increased by 50% which is particularily noticable in the bass. Its just that Bruce said the amp(s) would prefer to see 16 ohms and I wanted to hear what they can do in their stride. "BTW, vintage kHorns are stated to be 16 ohms....different drivers/crossovers though...." I have 87's - 8 Ohm nominal. Have fun -Bryan Link to comment Share on other sites More sharing options...
Daddy Dee Posted January 20, 2005 Share Posted January 20, 2005 I've got an SE OTL driving Khorns with very good results. Link to comment Share on other sites More sharing options...
D-MAN Posted January 25, 2005 Share Posted January 25, 2005 Kind of interesting comment from PWK in the article posted most recently by Gil in Technical Questions section entitled "A Visit to the Klipsch Kingdom" by Bruce Edgar, 1989... When asked about the Khorn woofer, PWK said that he originally wanted an 8 Ohm woofer because it became a 16 Ohms when loaded into the Khorn. That is mysterious, because the modern K33E is technically rated as a 3.2 Ohm (4 Ohm) voice coil. What impedance does that make it, when put into the horn? I'm going to figure that the 16 Ohms being mentioned in both places ("How to Build Speaker Enclosures", Badmaeff and Davis, Sams Publishing, Chicago, Il., 13th reprint 1978) is the figure to shoot for with the Khorn and represents the nominal bass enclosure impedance. {edit} I keep getting the city and state wrong for Sams Publishing - it's INDIANAPOLIS, INDIANA - why I said Chicago IL, I don't know)... DM Link to comment Share on other sites More sharing options...
WMcD Posted January 26, 2005 Share Posted January 26, 2005 The Audio Magazine review of the K-Horn should be someplace on the forum. Does anyone know? I think I did not post it. But I can't be sure. I can post it for next weekend's reading if necessary. In any case, the impedance plot shows the woofer, between about 50 and 200 Hz, fluctuates between 5 and 6 ohms and is almost entirely resistive. This is fairly consistent with the spec on the K-33 which has a voice coil resistance of 3.2 (is that correct?) ohms. Horn loading in the mid bass should bring it up to 6.4 but that doesn't seem to be the case. Best, Gil Link to comment Share on other sites More sharing options...
D-MAN Posted January 26, 2005 Share Posted January 26, 2005 Gil, is that measurement just the woofer/horn or the entire speaker/crossover combination. I suspect that it is for the later. This would correspond to Al Klappenbergers results with the ALK-A crossover, if I remember correctly. I suspect that the (now) 16 Ohm horn-loaded K33E in parallel with a 16 Ohm K55 A and an 8 Ohm K77 tweeter and type AA crossover works out to around 6.something Ohms total. That would be around my expectations. The K33E by itself in the Khorn cabinet should result in a different impedance, hopefully 16 Ohms thereabouts? I'm guessing here. DM Link to comment Share on other sites More sharing options...
WMcD Posted January 26, 2005 Share Posted January 26, 2005 Thanks for the pointing out some issues. The impedance curve is for the load "seen" by the amp over the entire frequency range. It is measured just at the input terminals of the entire system, as you point out. However, that is relevant to any amp loading issue, as here, because the amp only functions in accordance to what it "sees" rather than why the impedance comes to be of any magnitude because of parallel wiring, etc. You are correct to think there is a parallel circuit issue. E.g., we do electically have the woofer, mid, and tweeter connected in parallel to the input. You can trace that out in a schematic. So if each driver was 8 ohms, the total impedance would be 8/3 ohms. There is a big however. It is that the crossover includes caps and inductors (let's leave out the autoformer and Klipsch's midrange set up because it gets complicated). We see the woofer has an inductor in series with it. It acts as a low pass filter. Only low frequecies go through The tweeter has a cap in series, only high frequencies go through. A rough way of looking at this is that the inductor acts as an open circuit above the cross over frequency. That is why only low frequencies go through. You could consider it an open switch above the bass frequency. Also, a cap acts as an open circuit below the crossover frequency. That is why only high frequencies go through. Again, an open switch at lower frequencies. You put together the two above paragraphs and find something interesting. At woofer frequencies the impedance of the mid and tweeter are not seen at all. If this was a classic passband midrange (which is not true of the K-Horn) at mid frequencies the woofer and tweeter would not be seen at all. At tweeter frequencies the impedance of the woofer and mid is not seen at all. Going back to the bass issue. The impedance presented by the speaker below about 400 Hz is entirely due to the load created by the woofer terminals and the inductor in series with it. The other "switches" are open and we don't have a parallel circuit. Best, Gil Link to comment Share on other sites More sharing options...
Arkytype Posted February 4, 2005 Share Posted February 4, 2005 Gil, According to Roger Russell's web site, the Klipschorn was reviewed in the November 1986 issue of "Audio". Lee Link to comment Share on other sites More sharing options...
John Warren Posted February 4, 2005 Share Posted February 4, 2005 ---------------- On 1/26/2005 8:49:15 PM D-MAN wrote: The K33E by itself in the Khorn cabinet should result in a different impedance, hopefully 16 Ohms thereabouts? I'm guessing here. DM ---------------- Below is the total impedance of a sq motor K33 in free space and the same driver mounted in a Klipschorn bass unit. The driver has a somewhat higher impedance when measured in the Klipschorn due, almost entirely to the increased radiation resistance at the horn throat. So, as guesses usually go, your wrong. Link to comment Share on other sites More sharing options...
D-MAN Posted February 4, 2005 Share Posted February 4, 2005 John Warren, then please 'splain what PWK said about it being 16 Ohms in the Khorn. I've previously quoted the 2 sources in above posts. 2 printed sources, and then this - who are we supposed to believe? Could PWK and others mean at the horn's Fc? Even that does not expain the discrepancy. DM Link to comment Share on other sites More sharing options...
John Warren Posted February 4, 2005 Share Posted February 4, 2005 ---------------- On 2/4/2005 7:21:45 PM D-MAN wrote: John Warren, then please 'splain what PWK said about it being 16 Ohms in the Khorn. I've previously quoted the 2 sources in above posts. 2 printed sources, and then this - who are we supposed to believe? --------------- Why the hell should I "splain" anything! Your the one making the claim, you prove it! Below is the impedance of the Klipschorn as measured by Klipsch in the anechoic chamber. Everything above 300Hz has been cropped. The plot is the entire system, woofer, mid, tweeter and AK-3 network. My plot is just the woofer in the bass bin. The ordinate in total impedance in Ohms. The large peak is ~37Hz. As should be painfully evident to you, the impedance above the resonance peak is BELOW 10 Ohms and increases to 10 Ohms as the frequnecy increases to 300Hz. It is consistent with the plot I provided above. Link to comment Share on other sites More sharing options...
D-MAN Posted February 4, 2005 Share Posted February 4, 2005 John, I am not "making any claims" - I AM REPORTING PUBLISHED INFORMATION and I have quoted the sources above. The contradiction is the question, not your data. I have no doubt that you got what is displayed here. I am asking you to explain your post in light of the above mentioned sources, since you aimed it at me. Since you are in a position to provide actual test data, what are we to make of the publications mentioned above? DM Link to comment Share on other sites More sharing options...
John Warren Posted February 4, 2005 Share Posted February 4, 2005 ---------------- On 1/25/2005 5:36:28 PM D-MAN wrote: When asked about the Khorn woofer, PWK said that he originally wanted an 8 Ohm woofer because it became a 16 Ohms when loaded into the Khorn. That is mysterious, because the modern K33E is technically rated as a 3.2 Ohm (4 Ohm) voice coil. What impedance does that make it, when put into the horn? I'm going to figure that the 16 Ohms DM ---------------- "BINGO" there's your answer, YOU've drawn the wrong conclusion. For some odd-ball reason that must be entirely and utterly logical in your own mind, a 3.2 Ohm woofer mounted in the Khorn becomes a 16 Ohm impedance at the input terminals. So I guess you"figured" wrong. Link to comment Share on other sites More sharing options...
Recommended Posts