Guest LaboratoryStandard Xsducer Posted January 17, 2009 Report Share Posted January 17, 2009 Greetings from a newcomer reading the entire AR forum:My darling daughter, Jess, and her life partner Brad gifted us with an Onkyo TX-SR606 AVR. http://www.onkyousa.com/model.cfm?m=TX-SR6...eceiver&p=sAND a http://panasonic.net/avc/blu-ray/dmp-bd35_55/ for optical discsfor the TV, we have a 16:9 CRT from Sony the 34xbr970As you may know these are in the 'bang-for-the-buck' range of Hi-Fi. The big minus for me is in the power supply/complex impedance driving range of the AVR. The thing has crowbarred off a few times for me already. I mean I'm grateful, but the european model _CAN_ be made to drive 4 Ohm loads. >:-(So I have many issues to deal with. The Center channel speaker is one. Being very low on discretionary outcome, another (and mint, not like my barely restored) LST is out of contention, LOL.Can you recommend for audition a much more modest unit?I may end up, in any case, with one of these.http://www.vanns.com/shop/servlet/item/det...kef-iq2c-walnuthttp://www.vanns.com/shop/servlet/item/det...46/klipsch-sc-5 simply because of the really, REALLY good price.The KEF, is a co-axial driver and aesthetically pleasing cabinet.The Klipsch, being a better engineering match as an acoustic suspension/dome tweeter system with little spent on aesthetics.Both can be considered horn like but the difference in LF driver loading may throw my choice.If forced to choose, what do you think?The AVR can BI-AMP in 5.1 mode. This presents a possible solution in the amp/speaker issue.I have the LST diagram and with a little talented work on my part, I may be able to cut the system in half so one amp drives the LFs and the other drives MF/HF drivers. While not a classic restoration of ARs fantastic technology, something I cannot afford, it would go a ways to easing the burden on the AMPS, wouldn't you say?I look forward to hearing from you if you have a moment to reply. Thanks. :-)David Link to comment Share on other sites More sharing options...
Pete B Posted January 17, 2009 Report Share Posted January 17, 2009 It is interesting that the dynamic power is listed into 4 and 3 ohm loads which suggeststhat it at least does not current limit into low impedances. This suggests that heat mightbe the issue; is there free air flow around the unit, or is it in a cabinet?You might try a 1 ohm 25W resistor in series with each system to see if it shuts down.I can help you with bi-amping as I worked out the details some time ago but have not come across a pair to try it out.Have you done any work on your LST's do you know what value input cap is there andis there a resistor across it? An auto-transformer was used in this design, BTW.What part of the country do you live in, perhaps I could help you. Link to comment Share on other sites More sharing options...
genek Posted January 17, 2009 Report Share Posted January 17, 2009 My darling daughter, Jess, and her life partner Brad gifted us with an Onkyo TX-SR606 AVR.Is there no way you can exchange this receiver? One model up in the Onkyo range, the 706 is 4 ohm stable. Link to comment Share on other sites More sharing options...
Guest LaboratoryStandard Xsducer Posted January 17, 2009 Report Share Posted January 17, 2009 Is there no way you can exchange this receiver? One model up in the Onkyo range, the 706 is 4 ohm stable.You are correct in your phraseology. There is no way and no, it did not 'fall off the truck'.I guess I should have mentioned that pertinent fact in my post, so I apologise and very much appreciate your reply.Would that my issue could be solved that way.Could I sell 606?; yes but not for enough that I could grab a 706 without putting my LST's or maybe a kidney on eBay. ;-)I have some reason to believe that bi-amping (in the least destructive manner to the LSTs) would allow the 606 to distribute the complex load more evenly. Heck, at this point I am not even using the surround amps yet. I imagine when I get all the amps working the 606 will keep the house a bit warmer and if I don't push it in an Audessy Equalized- multichannel mode too hard, there won't be many crowbars. I will also explore the option of stereo only, or for real old fashioned fun, move the stuff in the room around so I can have the genuine Bell Labs Standard for stereophonic sound. LSTs 30 feet apart with a center in between. You know, kind of like two Klipschorns with a Heresy center. I wonder what Mr. Vilchur thought of that set-up?Thanks for the reply. Link to comment Share on other sites More sharing options...
Guest LaboratoryStandard Xsducer Posted January 17, 2009 Report Share Posted January 17, 2009 It is interesting that the dynamic power is listed into 4 and 3 ohm loads which suggeststhat it at least does not current limit into low impedances. This suggests that heat mightbe the issue; is there free air flow around the unit, or is it in a cabinet?You might try a 1 ohm 25W resistor in series with each system to see if it shuts down.I can help you with bi-amping as I worked out the details some time ago but have not come across a pair to try it out.Have you done any work on your LST's do you know what value input cap is there andis there a resistor across it? An auto-transformer was used in this design, BTW.What part of the country do you live in, perhaps I could help you.Thank you for your interest, and I have made significant modifications to the enclosure where the 606 resides to reflect the space requirements from the manual. I can't make the sides wider (there is open space there) but there is now plenty of room for thermal draft. Perhaps I should fan it as others on the dedicated thread in the AVS forums have done, few of which are driving as challenging an impedance as I. I reside in the Lehigh Valley area of the Keystone state. I see you hail from the Nutmeg State.I have taken the LF drivers out for Millersound resurrounding. Bill has my highest recommendation.Have I exhaustively disassembled the LSTs? No, but you could say that I have field stripped them. I have also built my own speakers at a time shortly after the LSTs were introduced. They were Sherwood Ravinias with drivers and Xovers hand picked by one of Sherwood's engineers. A large 3 way sealed enclosure system with a tweeter very much like the LST midrange and a sealed 6 inch paper cone for midrange and 12 inch LF.I will have to expose the Xover of the LST to determine my approach and will photograph all in detail. Link to comment Share on other sites More sharing options...
onplane Posted January 18, 2009 Report Share Posted January 18, 2009 Well, if money is tight, why purchase a center channel speaker? I'd wait until you have the LST's bi-amped and see whether it's necessary.As I recall, David, the LST has a circuit board that will require modifications, if you were to bi-amp with two independent amps. When using a quad or a multi-channel amp, it becomes much easier as you no longer have to touch the circuit board. The idea would be to set the Onkyo to 4 channel output and then select Stereo ALL. This puts the same signal on the surround amps as on the front amps. You would then have the front amp drive the mids/tweeters and the surround amp power the woofers.Next, you would completely by-pass the transformer and the huge cap bank. These things create problem loads and without them your Onkyo should have no problems at reasonable volume levels. The separate amps (front & surround) provide a methology to balance the mids and woofers. What is lacking is a way to control the tweeters. The best way to control the tweeters would be to insert a variable resistor in the mid driver circuit. That is, you need a way to "pad the mids". Once you do that, you'll have far more control over LST voicing than you get with the 6 position switch.Send me a PM once you get the woofers back and I'll send you a diagram showing how you would wire the speakers with the very least modifications (so that you could easily return to stock form).Regards,Jerry Link to comment Share on other sites More sharing options...
Pete B Posted January 18, 2009 Report Share Posted January 18, 2009 You're welcome, yes I believe that some low speed fans would help if you're certain that it is a thermal problem.Interesting project, will enjoy reading your updates.I commented on how to eliminate the auto-transformer and input cap, whichwould allow bi, or tri-amping. Then it was confirmed when a member hereposted this letter from Roy Allison:http://www.classicspeakerpages.net/IP.Boar...amp;#entry72334 Link to comment Share on other sites More sharing options...
Guest LaboratoryStandard Xsducer Posted January 18, 2009 Report Share Posted January 18, 2009 Well, if money is tight, why purchase a center channel speaker? I'd wait until you have the LST's bi-amped and see whether it's necessary.As I recall, David, the LST has a circuit board that will require modifications, if you were to bi-amp with two independent amps. When using a quad or a multi-channel amp, it becomes much easier as you no longer have to touch the circuit board. The idea would be to set the Onkyo to 4 channel output and then select Stereo ALL. This puts the same signal on the surround amps as on the front amps. You would then have the front amp drive the mids/tweeters and the surround amp power the woofers.Next, you would completely by-pass the transformer and the huge cap bank. These things create problem loads and without them your Onkyo should have no problems at reasonable volume levels. The separate amps (front & surround) provide a methology to balance the mids and woofers. What is lacking is a way to control the tweeters. The best way to control the tweeters would be to insert a variable resistor in the mid driver circuit. That is, you need a way to "pad the mids". Once you do that, you'll have far more control over LST voicing than you get with the 6 position switch.Send me a PM once you get the woofers back and I'll send you a diagram showing how you would wire the speakers with the very least modifications (so that you could easily return to stock form).Regards,JerryHi Jerry,Thanks for replying and I should've mentioned at first that _my_ name is David. :-) Hello again.The nature of the primary listening material specifies a center channel. I am just the sysadmin (husband). The CEO almost exclusively requires this type material.I think I know where you are coming from and I very much see what you mean about 'why spend if you don't have to spend'. I'm using a borrowed Klipsch computer 5.1 in-a-box center speaker. I have heard different specific %'s but the concensus is that a majority of what you hear in this material is from the center signal. Even without it the LSTs sound great great but with my less than ideal A/V feng shui, the center fills a hole better that the TV's speakers ever could.The Onkyo 606 AVR BI-AMPs this way:Start of quoteThe FRONT L/R and SURR BACK L/R terminal postscan be used with front speakers and surround backspeakers respectively, or bi-amped to provide separatetweeter and woofer feeds for front speakers, providingimproved bass and treble performance.• When bi-amping is used, the AV receiver is able todrive up to 5.1 speakers in the main room.• For bi-amping, the FRONT L/R terminal posts connectto the front speakers’ tweeter terminals. And theSURR BACK L/R terminal posts connect to the frontspeakers’ woofer terminals.• Once you’ve completed the bi-amping connectionsshown below and turned on the AV receiver, you mustset the Speaker Type setting to Bi-Amp to enable biamping(see page 42).[i have included this irrelevant bit below for context]Important:• When making the bi-amping connections, be sureto remove the jumper bars that link the speakers’tweeter (high) and woofer (low) terminals.• Bi-amping can only be used with speakers that supportbi-amping. Refer to your speaker manual.end quoteThis is where my work comes in. What to cut, where to cut and where to place the extra set of connectors with as little damage as possible. I read PeteB's thread suggestion. Would this apply to the LST?Thanks!David Link to comment Share on other sites More sharing options...
Pete B Posted January 18, 2009 Report Share Posted January 18, 2009 This image is the LST crossover schematic marked up by Roy Allison. The changes howeverare fairly extensive if you compare it to the original LST schematic and the contour switch isremoved. You could use LPADs as in the 3a, switched attenuators, or fixed resistor based series-shunt pads set to your preferred settings:http://www.classicspeakerpages.net/IP.Boar...ost&id=3185I've also had thoughts of keeping the autotransformer for the mid-tweeter array, with thewoofer wired as in the above diagram which would allow bi-amping and remove the capand transformer from the woofer circuit. Link to comment Share on other sites More sharing options...
genek Posted January 18, 2009 Report Share Posted January 18, 2009 You are correct in your phraseology. There is no way and no, it did not 'fall off the truck'.I guess I should have mentioned that pertinent fact in my post, so I apologise and very much appreciate your reply.Would that my issue could be solved that way.In this situation I would probably opt for an impedance matching autoformer between the speakers and the amp. Russound has several models that come in black box form and built into remote volume or speaker selector controls. Autoformers do introduce some degradation in performance, but the receiver and center channel speaker you're trying to work with are not high end performers and high end performance is generally wasted on home theater sound anyway. Given the lack of durability of modern electronics, you'll likely be replacing that receiver in 5 years or less; I wouldn't open up and modify a 30+-year-old classic speaker to try to make it compatible with it. Link to comment Share on other sites More sharing options...
onplane Posted January 18, 2009 Report Share Posted January 18, 2009 Hi Jerry,• For bi-amping, the FRONT L/R terminal posts connectto the front speakers’ tweeter terminals. And theSURR BACK L/R terminal posts connect to the frontspeakers’ woofer terminals.This is where my work comes in. What to cut, where to cut and where to place the extra set of connectors with as little damage as possible. I read PeteB's thread suggestion. Would this apply to the LST?Thanks!DavidDavid, the boldfont above from Onkyo is exactly the same as I was suggesting. This will require the least cutting/chopping of your LST's. The only problem area is the mid-drivers. They need to be padded or they will over power the tweeters. The LST xover has some padding already, but it's simply not enough once you eliminate the transformer. Further, you'll want some ability to control the amount of padding, so either an AR-3 type pot or a variable resistor. Pete, you mentioned keeping the autotransformer for the mid/tweeters. Boy, I would think there are two problems with that:1. the autotransformer and cap bank are a "bad load" for powerhouse amp and what we have here is modest power amps2. life just becomes too complicated as the balance between woofer and mids will be controlled by the volume levels in the front and surround amps. This leaves the switch just controlling the balance between the mid and tweeter. Frankly, I think there are simplier ways to do this.Gene, is suggesting that you use a transformer to bring the impedance of the LST's UP so that's it will be more compatible with the Onkyo. Now, that will work, but remember you already have a transformer INSIDE the LST's. When you put two transformers PLUS that huge cap bank together, anything can happen. That is, the entire system may oscilate. I mean, we are really into an unknown area with the only certainity that audio quality will degrade.Hope this helps ...Regards,Jerry Link to comment Share on other sites More sharing options...
Pete B Posted January 22, 2009 Report Share Posted January 22, 2009 Pete, you mentioned keeping the autotransformer for the mid/tweeters. Boy, I would think there are two problems with that:1. the autotransformer and cap bank are a "bad load" for powerhouse amp and what we have here is modest power amps2. life just becomes too complicated as the balance between woofer and mids will be controlled by the volume levels in the front and surround amps. This leaves the switch just controlling the balance between the mid and tweeter. Frankly, I think there are simplier ways to do this.Gene, is suggesting that you use a transformer to bring the impedance of the LST's UP so that's it will be more compatible with the Onkyo. Now, that will work, but remember you already have a transformer INSIDE the LST's. When you put two transformers PLUS that huge cap bank together, anything can happen. That is, the entire system may oscilate. I mean, we are really into an unknown area with the only certainity that audio quality will degrade.Hope this helps ...Regards,JerryJerry, I don't see the logic in your point that what I suggest would be a "bad load".I could use complex conjugate load matching if I thought it was a problem, howeverI don't expect any issues. The input impedance is easy to measure.I would not do it this way (normally) but the auto-transformer is there and wouldneed to be replaced with pots, or whatever if it was removed.The external transformer is a real bad idea, good high power transformers are expensive and heavy. Better to outboard a high current amp at that point. Link to comment Share on other sites More sharing options...
genek Posted January 22, 2009 Report Share Posted January 22, 2009 The external transformer is a real bad idea, good high power transformers are expensive and heavy.The OP's receiver is rated 90W, 20-20k, 2 channels driven. With all channels going for surround or biamp use, he'll be lucky if he can get 50WPC before it clips or the circuit protector kicks in. 40 real, classic era WPC is more likely. He'd be throwing his money away on anything with a rating higher than 50W RMS. Link to comment Share on other sites More sharing options...
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