Daddy Dee Posted May 18, 2004 Share Posted May 18, 2004 O.k. I've got some questions about what is happening in a tube amplifier when the speakers are run off the 4 ohm taps instead of 8 ohm taps. On a SS amp, this is not an option, though depending on the amplifier there is sometimes concern about running a pair of 4 ohm speakers in parallel. I've got a couple of pro sound amps used by my youth group that can run into 2 ohm loads all night and not sweat it. I think I can remember Craig suggesting to discover whether I preferred the sound of my Scalas running off the 4 or 8 ohm taps of my first 299. Never did check that out, seemed too much like work. From time to time I will set up a Heresy center with my Khorns and run the output through a Dynaco QD2 to derive a center channel and run all three speakers off two monoblock amps. The sound is impressive. Someone shared with me a week ago that the rigged as such, the QD2 presents a 6 ohm load to the amps. So I thought, might be a good time to change to the 4 ohm taps to see what it sounds like. I switched and am running the Wright 2A3 monoblocks off the 4 ohm taps through the QD2 to the Khorns and Heresy center. Wow. To my ears, the whole sound, especially the mid bass and bass sounds easier, fuller, richer, effortless. I didn't really know what to expect. One thing I'm wondering is... what is going on in the amplifier running of 4 ohm instead of 8 ohm taps? How does a SS amp manage w/o different taps? What if one runs 8 ohm speakers off 4 ohm taps all the time? Is the difference in sound completely subjective? Could it be measured with instruments? My daughter (in engineering school) just gave me her textbook from an intro to electronics she had this semester. So I'm in kindergarten. Appreciate any help here. Talk real slow please. Quote Link to comment Share on other sites More sharing options...
Cal Blacksmith Posted May 18, 2004 Share Posted May 18, 2004 The short story is that the output transformer is there to keep the load even on the output tubes with the different speakers. If you hooked up a 4 ohm speaker on 8 ohm taps, the output tubes will see twice the power draw (current) than normal. When you hook up to the 4 ohm taps, the load is back to normal for the output tubes. Tubes are voltage devices, not current. If I have this wrong, I am sure that I will be corrected! The output on a SS amp, transistors, are current devices not voltage. If they are big enough they can suck up the extra load that a speaker mismatch puts on them. Again I am sure if I am wrong, there will be voices to that affect. At least this is the way I understand the situation. Quote Link to comment Share on other sites More sharing options...
hwatkins Posted May 18, 2004 Share Posted May 18, 2004 Bravo Mark - well done and clear... Quote Link to comment Share on other sites More sharing options...
Deang Posted May 18, 2004 Share Posted May 18, 2004 Dee, your Klipschorns and LaScalas have a nominal impedance of 6 ohms. There some large swings in impedance, going from a little over 5 ohms all the way up to 30 ohms or more. Though sensitive speakers, our big horns actually present a somewhat complex and difficult load to a tube amp. I would use the 4 ohm taps, and if you want to do something interesting -- attach a 15 ohm resistor in parallel with the amps outputs. Quote Link to comment Share on other sites More sharing options...
Parrot Posted May 18, 2004 Share Posted May 18, 2004 I thought the impedance was usually given as 8 ohms. No matter, whatever setting you choose is a compromise because the ohm rating listed is just in name only. In the "Audio" magazine review of the Klipschorn in 1986, the Klipschorn tested ranged from 4.5 ohms to 42.3 ohms, depending on frequency. The measurement constantly changes depending on the music being played. One big benefit of the ALK balancing networks is that this range is tightened a lot. Bass performance should indeed be better using the 4 ohm connections on your amp. Quote Link to comment Share on other sites More sharing options...
ben. Posted May 18, 2004 Share Posted May 18, 2004 Careful, I'm beginning to understand here.... Quote Link to comment Share on other sites More sharing options...
Cal Blacksmith Posted May 18, 2004 Share Posted May 18, 2004 ---------------- On 5/18/2004 9:40:22 AM mdeneen wrote: Tube amps are the reverse because of the "transformer". They can deal with loads above the intended impedance since the B+ is hugely higher than the output voltage there is always room. But with loads BELOW the intended range they quickly run out of current. The maximum current in the ouput tubes is a tiny fraction of the load current. This is generally why SS amps are referred to as current amps, and tube amps are voltage amps. mdeneen ---------------- So to answer my question on the Forte/Heresy thread, if I hook the 2 nominal 4 ohm speakers together in series so that they present a "nominal" 8 ohm load on my 4 ohm taps, every thing should be ok? right? Quote Link to comment Share on other sites More sharing options...
mark1101 Posted May 18, 2004 Share Posted May 18, 2004 To Mark Deneen, Excellent explanations, just like my professors back in the day. However, what sound characterisitics will I notice changing my LaScalas or cornwalls from the 8 ohm tap to the 4 ohm tap. I have Scott integrateds. I am guessing that from what I have read here, the speakers flucuate more above 4 Ohms than below. Thus playing into the sweet spot of a tube amp. Or maybe better stated, playing into its capabilities. So are you saying that you can get better sound on the 4 ohm tap with Klipsch speakers and tube amps? What are your experiences in percieved sound? Thanks for any additional info here. Quote Link to comment Share on other sites More sharing options...
Cal Blacksmith Posted May 18, 2004 Share Posted May 18, 2004 My Forte 1s are rated at 4 ohm on the nameplate and 8 ohm by Klipsch specs. I first played them at 8 ohm and they sounded good. I then played them on the 4 ohm tap and the bass became deeper and the mids became better also, while causing me to turn the gain up on the preamp a little higher to acheave the same sound pressure. Quote Link to comment Share on other sites More sharing options...
mark1101 Posted May 18, 2004 Share Posted May 18, 2004 Will it hurt anything if I change just 1 speaker to the 4 ohm tap and leave the other on the 8 ohm tap temporarily? Then, I could hear the difference between the 2 Channels. The Scott integrateds have nice controls for balancing the channels and should work nicely to help determine the better tap. Quote Link to comment Share on other sites More sharing options...
Colin Posted May 18, 2004 Share Posted May 18, 2004 At preacherman DaddyDees Klipsch gathering in Little Rock, Arkansas (May, 2004), Stream moved from the 8-ohm posts on his copper faced Cayin TA30 integrated tube amplifier to the 4-ohm taps. The difference on his unmodified RF7s was slight, but my brief impression was that the bass (because it was lower or because there was more of it?) extended further into the room, without any significant change in the mid-range Quote Link to comment Share on other sites More sharing options...
Cal Blacksmith Posted May 18, 2004 Share Posted May 18, 2004 ---------------- On 5/18/2004 10:46:26 AM mark1101 wrote: Will it hurt anything if I change just 1 speaker to the 4 ohm tap and leave the other on the 8 ohm tap temporarily? Then, I could hear the difference between the 2 Channels. The Scott integrateds have nice controls for balancing the channels and should work nicely to help determine the better tap. ---------------- I can't see how it would hurt anything, each channel has it's own amp so one shouldn't affect the other. With my amp, it is a solder reconnect so it was a bit more invloled. Quote Link to comment Share on other sites More sharing options...
djk Posted May 18, 2004 Share Posted May 18, 2004 "So to answer my question on the Forte/Heresy thread, if I hook the 2 nominal 4 ohm speakers together in series so that they present a "nominal" 8 ohm load on my 4 ohm taps, every thing should be ok? right?" NO Unless the speakers are identical the frequency response will be changed as the peaks and dips in impedance are at different frequencies. "So are you saying that you can get better sound on the 4 ohm tap with Klipsch speakers and tube amps?" At low volumes a speaker always plays loudest on the 8 and 16 ohm taps. As you turn up the volume and 'thump' it a bit you will find the speaker sounds the best on the tap that closest matches its impedance, and plays the loudest too. Always try the 4 ohm tap. Leave it on whatever sounds the best. Hint: it sounds 'thin' when you turn it up if you have it hooked to too high of a tap. Quote Link to comment Share on other sites More sharing options...
chops Posted May 18, 2004 Share Posted May 18, 2004 This reminds me of when I had the Cornwalls and MY Mcintosh MC250 hooked up together. At first, I naturally had them hooked up to the 8 ohm taps. Then after doing some reading online, I heard people suggest hooking them up to the 4 ohm taps. To make a long story short, I left it that way for the rest of the time. The bass was better sounding (not sure about deeper bass or more bass though), the mids were fuller, and the treble was smoother and warmer. Overall, that MC250 really started to sound like a real tube amp when wired into the 4 ohm taps. One other thing I remembered is that it ran cooler using the 4 ohm taps as well. BTW, reading those two posts of mdeneen's made me feel like I was listening to my dad talk when I ask him how tubes and such work and why. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted May 18, 2004 Author Share Posted May 18, 2004 Thanks guys for the help here. And for typing slow for me, too. Is this a great forum or what? Here are two all too rarely combined elements... one is an impressive base of knowledge... the second is a willingness to teach and share. Appreciate the commitment to fight ignorance, even if it is taking alot longer than anybody thought! Quote Link to comment Share on other sites More sharing options...
mark1101 Posted May 18, 2004 Share Posted May 18, 2004 Thanks guys. I will try the 4 ohm taps and see how it sounds. Nice explanations. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted May 18, 2004 Share Posted May 18, 2004 ---------------- On 5/18/2004 11:14:51 AM djk wrote: Hint: it sounds 'thin' when you turn it up if you have it hooked to too high of a tap. ---------------- What if it sounds absolutely perfect when you turn it up but slightly thinner at low volumes ?? Just thought I will throw some twist into the subject ! Quote Link to comment Share on other sites More sharing options...
dubai2000 Posted May 18, 2004 Share Posted May 18, 2004 From my listening experiences there is no generalization here. Whereas the MC30s and the Wrights sound better to me (more open, transparent) using the 4 ohm taps when running with the Khorns, the Eico sounds thin on 4 ohms when using it with the Heresy (never tried that on the Khorns though). So best seems to be listenening and deciding according to one's ears. Wolfram Quote Link to comment Share on other sites More sharing options...
mark1101 Posted May 19, 2004 Share Posted May 19, 2004 Well guys, did the testing last night and for me it's the 8 ohm tap on the 222/LaScalas system. It sounded thin on the 4 ohm tap, just not as good. Even at louder volumes not as good. I started by just changing 1 speakre so I could usd the balance control to hear the differences. I don't what is so different about our systems that most of you guys seem to prefer the 4 ohm tap. It was easily clear that 8 ohms was better here though. In fact when I heard the system at first, I can remember "that sound" and that I had tried this last year and been through the whole thing already. Anyhow, thanks for the great info on the fundamentals here. Quote Link to comment Share on other sites More sharing options...
Audible Nectar Posted May 19, 2004 Share Posted May 19, 2004 Mark, I think it's just a matter of what amp you have. On my McIntosh 250, the 4 ohm taps are preferred here (on the Belle Klipsch and the Cornwalls), it seems that those owning MC-30's are using those too (and that has been noted here as well). Quote Link to comment Share on other sites More sharing options...
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