They sounded great with my Dynaudio Mirage
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Is it safe to assume the ARC gear including all tubes are in good working order? I’d make sure.
If so, those ARC amps still may not be a great match to drive Dynaudio speakers properly. Not surprised the SS Luxman sounds better. The manual online says Classic 120 produces same power to 4 8 or 16 ohm loads. I have Dynaudio Contour 1.3 mkII. You want SS amps that double power output from 8 to 4 ohm with Dynaudios to drive them best with right tonality. This is due to variations in impedance load at various frequencies. That is par for the course with many modern home audiospeakers these days. I use Bel Canto ref 1000m amps and Audio Research sp16 tube pre-amp. This sounds great. Getting the right amp to run Dynaudio is the best first step then fine tune from there if needed.
Mapman, if you download the "manuals" (they’re actually nicely detailed spec sheets) at the following link, for your Contour 1.3 MkII and the OP’s Contour 1.8 MkII, you’ll see that the impedance characteristics of his speakers are much more benign than yours. And in fact their impedance magnitude is remarkably flat compared to most speakers, with impedance phase angles being benign as well.
Also, based on the Classic 120’s specified damping factor of 45 and its use of a relatively large amount of feedback (21 db), it seems certain that the Classic 120 has VERY low output impedance for a tube amp, approaching solid state territory in that respect. So the amp **will** double power into halved load impedances, to a very close approximation, as long as it is not asked to exceed its maximum power capability.
So on paper, at least, it seems like the Classic 120 should be a suitable match for the Contour 1.8 MkII, assuming its maximum power capability is adequate for his purposes (which I would expect it to be under most circumstances). Also, based on the numbers in the spec sheet it seems very likely that the 4 ohm taps of the amps would be the best match for these speakers. If one of the other taps is being used the 4 ohm tap should certainly be tried.
Finally, one thing I note in the spec sheet for the speaker is that its crossover uses "high quality polypropylene capacitors." Poly capacitors can require lengthy breakin periods, IME, with the speaker actually playing music for dozens if not hundreds of hours before they will sound their best. And I suppose it is conceivable that they could have lost that breakin during the four years of non-use. And perhaps the drivers need to loosen up as well. I mention these points because in reading the initial post I’m not completely certain if the solid state equipment that was mentioned was tried with the Dynaudio speakers, or if it was just used with the JBLs.
Almarg how would you reconcile the manual indicating same power into 4 8 and 16 ohm with doubling down power into the same? It is a hybrid design so that would bode well in terms of having low output impedance for a tube based amp.
Those amps were introduced in 1990 and not used for several years. It's possible they are not operating up to spec.
I suspected the larger models would be an easier drive but did not check the specs. Good catch! Dynaudios in general seem to get the rap of being towards the power and current hungry end of things.
Almarg how would you reconcile the manual indicating same power into 4 8 and 16 ohm with doubling down power into the same?
Tube amps providing multiple output taps typically have the same or similar **maximum** power rating when a 4 ohm load is connected to the 4 ohm tap as when an 8 ohm load is connected to the 8 ohm tap, and likewise for a 16 ohm tap if one is provided (as it is here).
However as long as the amp is operated within the limits of that maximum power capability, how much power is delivered as a function of the speaker’s impedance vs. frequency variations depends on the relation between the impedance of the speaker at each frequency and the output impedance of the amp. It does NOT depend on the amp’s **maximum** power capability, as long as that capability is not exceeded. That’s a point which is often not recognized. And as I mentioned the output impedance of this amp comes very close to being in solid state territory, and to being almost negligible in relation to the impedance of the speaker at all frequencies.
Yes the multiple outputs for various impedance levels does cover that.
The speaker specs indicate bass range impedance down to 3.8 ohm. Not natural turf for a tube amp. The speaker specs are fairly detailed for a product manual but specs still leave grey areas. Plus the current operating condition is not clear. It is very hard to say without actually being able to hear what the op hears. I’d give the Luxman a shot for comparison if not done already. Perhaps the ARC amps just need a tune up. They look pretty beefy like they should be reasonably up to the task. Still 4 ohm and less in the bass region and most tube amps are not a natural match from a low distortion perspective.
Hey Al the way the manual is written the 45 damping factor may only be when used with 16 ohm speakers. The amps input stage is semiconductor based, the output tube. Could this tube amp similarly produce a damping factor of 45 into a 4 ohm load? Maybe but do you see in the specs where that is indicated?
I see the statement you are referring to, which says:
Output Regulation: Approximately 0.2 dB 16 ohm load to open circuit (Damping factor approximately 45)Like most tube amps, the Classic 120 is presumably designed such that the output tubes see a load that is the same or similar when a 4 ohm load is connected to the 4 ohm tap as when an 8 ohm load is connected to the 8 ohm tap, and as when a 16 ohm load is connected to the 16 ohm tap.
To accomplish that, it can be shown that ideally the output impedance of the 4 ohm tap would be half of what it is for the 8 ohm tap, which in turn would be half of what it is for the 16 ohm tap. Ideally that would result in the damping factor being the same for all of the taps. Various factors will cause some differences between the three damping factors, especially when the output impedance is very low, but they will usually be in a similar ballpark.
And given that a damping factor of 45 for the 16 ohm tap corresponds to an output impedance of 16/45 = 0.36 ohms, and the fact that the output impedance of the 4 ohm tap is almost certainly lower than that, it seems safe to say that interaction of the amp’s output impedance with the impedance variations of a speaker whose minimum impedance at any frequency is 3.8 ohms will not be significant.
Almarg yes one can presume that is the case and most likely should be just not clearly identified in that spec as written.
If if everything is properly connected and working properly including broken in as you alluded to earlier then it just may be that is not the right amp for that particular user.
OP it has nothing to do with quality of ARC gear in general FWIW. All ARC amps are different and this may just not be the right one for you if things continue as is currently. Break in of amps and speakers is a real phenomenon. Maybe that would help. If not consider a different amp for comparison. Something high power and high current. I’d recommend Trying a newer high quality class d amp if it comes to that. Give the Luxman a shot if not already. That might do just fine.
Thanks everyone for spending time putting in comments.
To almarg: Speaker polarity is correct as I double checked per your recommendation.
To mapman: I checked the Luxman spec and it is only for 8-ohm speakers. Not sure if I can connect the Luxman to Dyn?
I have turned the amps on and let it run for the last 12 hrs. During that time, I kept playing CD to CD at low volume level just to have some signals running through the whole system. During bed time, I just left them on (including the preamp). I have also played around with speakers position. This morning, before going to work, I played some song and saw that the quality has improved. Also, I checked and see one of the big tubes in one of the amp is not lighting up. So I will do this to clear things out:
- Have the amp and premap serviced
- after that, play around more with speaker positions since I have a weird corner to set up my gears. Please see picture
Put I really think that my amps are not for Dyn speakers. I will try with JBL speakers to find out.
Again, thanks everyone for helping me, I really appreciate it.
The JBLs listed nominal impedance is 8 ohm. The Dynaudios 4 ohm. I do not see an output impedance spec for the Luxman amp but its a safe bet being a SS amp that it is low and not an issue that would prohibit its use with 4ohm nominal speakers. This is of course as always assuming the amp is in decent working order.
The JBLs are likely an easier load to drive, but you can still use most any SS amp with 4ohm nominal impedance speakers safely. As always, just do not overdue it. Start at lower volume and go up gradually. If you hear signs of audible noise or distortion turn it down. Also check to make sure the amp is not getting too hot in that it will have to work harder into a 4ohm load than with 8.
You could even try running the JBLs off the ARC amp. The 8 ohm JBLs are inherently more tube amp friendly than the 4 ohm Dyns. Worth a try! You never know what you will find to sound best. In general amps tend to have higher distortion levels overall into 4 ohm nominal impedance loads than 8. You could then try both the 8 or 4 ohm taps of the amp and compare. Whatever you end up doing trying various combos of what you have is definitely worthwhile. You never know exactly what you will hear until you hear it.
Don't overlook your room either. It has an enormous impact on the sound. Try getting the speakers well away from the walls and listen in the nearfield. Do you hear the same harshness? Maybe, maybe not. If not, than you can start looking at how to better place the speakers and improve your room acoustics.
The LS-22 is one of the very few ARC preamps I’ve ever heard criticized in the forums (many years ago) as mediocre. Suggest replacing it with an Ref-3, Ref-5SE, even an LS-2B.
I’ve owned a number of ARC units and hold them in high regard.
Also, what wire are you using? I use OCC copper exclusively (YMMV).
"Also, I checked and see one of the big tubes in one of the amp is not lighting up."
I am surprised that the amp plays anything if an output tube is bad/blown, my Classic 150 will go into protection mode (indicated by dimming of Screen LED).
The Classic 150 has a 7 position terminal block on the rear with taps from the output transformer connected to it internally, see your owner's manual for the 4 ohm terminal combination.
My Dynaudio Mirage were 4 ohm and I had no issues as I stated above