32blownhemi Posted January 29, 2018 Share Posted January 29, 2018 I'm bi-amping my Julilee's & K-402 Horns with two Mc275's. Do I use the 4 ohm or 8 ohm connections? I thought someone told me to use the 4 ohm connections but McIntosh told me to use the 4 Ohm one's... Thank You! Bill Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 29, 2018 Share Posted January 29, 2018 4 ohm on Jub LF 8 ohm on K402 if using any of the standard Klipsch drivers I’ve seen paired with it. miketn Quote Link to comment Share on other sites More sharing options...
Schu Posted January 29, 2018 Share Posted January 29, 2018 I thought you could use either connection that sounds the best to you and your set up. Quote Link to comment Share on other sites More sharing options...
Deang Posted January 29, 2018 Share Posted January 29, 2018 If you're biamping, you can optimize the setup. Since the LF section runs two woofers in parallel, 4 ohms makes the most sense. Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 29, 2018 Share Posted January 29, 2018 24 minutes ago, Schu said: I thought you could use either connection that sounds the best to you and your set up. In most situations you can try either and there will be some slight frequency spectrum shifting. In the specific question by Bill the Jub LF is closest to a 4 ohm load in the frequency range it will be used and the best damping factor will be with the 4 ohm tap of the Mc275. miketn Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 29, 2018 Share Posted January 29, 2018 Bill are you doing Vertical Bi-Amping using the Mc275 amps...? If not I strongly suggest you do since it will maximize the systems performance. miketn 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted January 29, 2018 Share Posted January 29, 2018 Quote Link to comment Share on other sites More sharing options...
Md5150 Posted January 29, 2018 Share Posted January 29, 2018 I've been using the 8 ohm taps on the 402 horn with mc452 amp. Sounds great to me. The compression drivers are 16 ohm, why would anyone use the 4 or 2 ohm tap for this application? Quote Link to comment Share on other sites More sharing options...
32blownhemi Posted January 31, 2018 Author Share Posted January 31, 2018 On 1/29/2018 at 4:56 AM, mikebse2a3 said: Bill are you doing Vertical Bi-Amping using the Mc275 amps...? If not I strongly suggest you do since it will maximize the systems performance. miketn Thanks for all the replies everyone! I'm Horizontal Bi-Amping. I will switch to Vertical... McIntosh told me that my tubes showed excessive wear (on the amp they repaired recently) & the reason was because I was using the 8 ohm connections. They said to switch to 4 ohm's that being on 8 ohm's was forcing the amp to put out double power. They said the Jubilee bass bins were 4 ohm but they say 8 ohm on them. They said the 402's were 4 ohm... Hmm... Bill Quote Link to comment Share on other sites More sharing options...
Deang Posted February 1, 2018 Share Posted February 1, 2018 I think the folks at McIntosh have lost their minds. Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted February 1, 2018 Share Posted February 1, 2018 11 hours ago, 32blownhemi said: Thanks for all the replies everyone! I'm Horizontal Bi-Amping. I will switch to Vertical... McIntosh told me that my tubes showed excessive wear (on the amp they repaired recently) & the reason was because I was using the 8 ohm connections. They said to switch to 4 ohm's that being on 8 ohm's was forcing the amp to put out double power. They said the Jubilee bass bins were 4 ohm but they say 8 ohm on them. Bill the problem with trying to assign a single impedance value to a loudspeaker is in the fact that the large majority of them actually have a complex impedance that varies with frequency and the truth is a single number is often of very little use and whenever information is available showing the complex impedance of the loudspeaker then well informed decisions can be made but the average consumer wouldn't understand how best to use this information unfortunately. Also I will say well designed amplifiers should easily be able to handle loads from 4-ohms and up and if they don't I would be looking for a different amplifier because amplifiers must be able to handle impedance swings of loudspeakers. Here again is the Jub LF Raw Impedance Plot and in the specific case of the Jub LF as you are using it the impedance in the range from 20Hz to 600Hz should be the area of focus. Within this range we see the highest impedance peak of about 27 ohm @ 43Hz and the lowest impedance of about 3.35 ohm @ 68 Hz and as can be seen within this range an overall average of about 4 ohms is the best value to use when matching to Tube Amplifiers Output Transformer Tap Options. "They said to switch to 4 ohm's that being on 8 ohm's was forcing the amp to put out double power." While this is true because how you impedance load the secondary of the output transformer will be reflected back to the primary impedance of the output transformer (that the Output Tubes work into) it's not that simple and to blame the mismatched tap settings in this case for excessive wear is very questionable IMO unless you were pushing the amplifier towards it's maximum capabilities over long periods of time. Since we are talking Jubs here as little as 10 watts would send many people out of the typical size listening room in a very short time and the MC275 is capable of much more even if one was to de-rate it's output capability due to the impedance tap mismatch. Now if you are in a very large space and pushing the amplifier toward it's maximum output then they might have a point about excessive wear of the output tubes. Regardless placing the Jub LF on the 4 ohm tap of the amplifier will give your amplifier/loudspeaker the optimum balance of distortion, power output and least wear on the output tubes. miketn 2 Quote Link to comment Share on other sites More sharing options...
32blownhemi Posted February 2, 2018 Author Share Posted February 2, 2018 Thank You Mike! So I'll switch to the 4 Ohm connections & Vertical Bi-Amping. I'm going to go answer another post I have going "Tubes bad in 80 days on new Mc275? Are they BS'ing me?... Apparently my ADHD confused 'em. LOL... This post relates to that post.... Thanks again for all the replies! Bill Quote Link to comment Share on other sites More sharing options...
bharat Posted February 24, 2020 Share Posted February 24, 2020 On 1/29/2018 at 4:47 AM, 32blownhemi said: I'm bi-amping my Julilee's & K-402 Horns with two Mc275's. Do I use the 4 ohm or 8 ohm connections? I thought someone told me to use the 4 ohm connections but McIntosh told me to use the 4 Ohm one's... Thank You! Bill OP can I ask why the choice of MC275 to bi-amp and why not MC 75 monoblocks instead? Bharat Quote Link to comment Share on other sites More sharing options...
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