Some of the Adcoms are suppose to...but I would try a professional amp like Peavey,Crown,and the like .These are designed to handle the tough ohm loads and do it all day!
I am using a Pass Labs X-250 to drive MartinLogan Aerius i's, which drop to 1.2ohms at 20Khz fully driven.
Though it does spike the built-in power meter pretty hard on heavy treble transitions, the amp NEVER sounds stressed, and seems to be designed to shrug off this kind of load. If anything, these speakers are now the weak-point of my system - not the amp.
YMMV - This is only my personal experience - I don't know everything - please do not flame me.
The older Krells (KSA 80, 100, 200 and References, as well as their monoblock versions) were about your only choice back when Apogee was in business, a major reason they used to be demo'd together. Would expect them to still sound good as a combo. Don't know what's available now, but I'd expect a pure class A design might fill the bill (Gryphon?). You might want to check the archives for a link to the Apogee users group website, I'm sure they'd have plenty of suggestions.
McIntosh has performance graphs for most of its recent amps that show total stability at 1 ohm.
However, it also depends on the volume you wish to listen at since the power is to the square of voltage (P=V^2/R). Most amps will do it at low volume but then they will either overheat (surprising how many designs are inadequately cooled) or clip heavily at higher levels. It's hard to answer your question directly. I don't know of any amps that will rock hard at 1 ohm for extended periods. Need to look at the impedance graph of your speakers because the minimum may only happen at one point.
Scintillas? Seadogsl, how much money do you want to spend? Old krells would be your cheapest way out, but if you want to get the best out the best speaker in the world (IMO), then the Pass Labs X600 monos are unrivaled (IMO). Old Krells probably will have maintenace problems. Pass X600 amps are still relatively new, and are fine used. Expect to pay approximately $7000 for used ones (still a lot cheaper than Gryphon.)
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You may find that the Zero Autoformer useful with low impedence speakers. The "Zero's" multiply the speakers' impedence allowing an easier load for your amp. I use them very successfully with Audio Research tube amps and Soundlabs. The designer recommends caution when using the Zero's with certain SS amps with excess offset voltage (details are in the literature) Check out the website for more information: www.ZEROimpedence.com.
The Apogee Scintilla's (which I believe you're referring to) were most often mated with Classe Audio amps. Jason Bloom and David Reich had a close working relationship; I'd go so far as to say they voiced their stuff for the best synergy. The pure "class A" Classe audio amplifiers that mated with the Scintilla's were the DR-3 (sometimes in pairs) and more appropriately the DR-VHC amps. Gobs of current. I know all this to be accurate; email me if you'd like to know more. Best, Jeff
I have no quarrel with chunky class A amps with huge heat sinks being able to run a 1 ohm load. Classe amps of that descriptin do power the Scintilla well. But that does not mean they have the best synergy with the Scintilla. It may have been true a dozen years ago. If the Pass X600 wasn't around, I would have thought seriously about the Classe..
There was a guy here on Audiogon that was running Perreaux PMF-2150's in bridged mode to drive Apogee's. I can't remember who it was, but that is one helluva testimony to the ruggedness / reliability of the Perreaux. In bridged mode, the amps were seeing somewhere around half an ohm (.5 ohms) !!!
As a side note, my Perreaux 3150's have no problem driving very low impedances. Much of this has to do with the heavy gauge output inductor that Perreaux uses. Not only does the amp maintain a low output impedance as power is increased*, it can pass more current on demand as needed without any type of restriction. That's why these amps, when running properly, have great bass impact. Most amps have relatively scrawny output inductors, so they lack the capacity to pass enough current as needed. The end result is a lack of control as impedances are reduced and a reduction in "slam" at any impedance.
Other than that, the two channel Sunfire Signature will drive Apogee's with no problem. Sunfire even has a specific set of "factory mods" that they do for Apogee's. I've had this done to my Signature and it noticeably increased the bass impact. One of the reasons for better bass response ? They install larger output inductors to pass more current : ) Sean
* damping factor varies with the dynamic load and output levels that the amps sees and responds to. Many "techs" & "engineers" will say i'm off my rocker, so believe whom you want.
Have you ever tried a 1 ohm load with the palladiums..
The head sinks are "v" grooved in the center and rather effective. As differential monoblocks, you have only one channel per chassis to cool... Granted the Krell ksa's have alot more Visible heat sinks, I have run most every kind of speaker load with the palladiums with no failure in the short term and no signs of fatigue.
All due respect,
Custom Audio LLC
Just to clarify things, the "Apogee mod" is the slang term that Sunfire uses for the mods that they do to their amps to better deal with very tough to drive, low impedance, low sensitivity speakers. Since Apogee's are the "ultimate" in terms of "low impedance, low output, high reactance" speakers, they chose to name the mods for the amps after those speakers. As such, Sunfire does not perform modifications to Apogee speakers.
Other than that, i'm sure that there are mods and tweaks that one can do to the various Apogee models. Sean
Kool, nobody runs Aragons on Scintillas. Duettas, Divas, Calipers, yes, but not Scintillas. Scintillas run on an average 1 ohm, and dips down to .6 ohm. This pulls a tremendous amount of current through the amps, causing huge temp rises. This requires giant heat sinks or fans, neither of which the Aragon has.
Actually Apogee speakers are not a highly reactive load. They are mainly a resistive load. Only the Scintilla ran at 1 ohm. Most other ribbon models run in the 3-4 ohm range, a horse of a different color entirely.
Actually the Scintillas have a 3 ohm wiring option, but don't sound as good this way.
THe old Krell KMA-100 and KMA-200 monoblocks were built with the Scintilla in mind.
A 1 Ohm load will barbeque most amps.
Ghostrider: Thanks for the clarification. For some reason, i was thinking that these were quite reactive loads.
As far as 1 ohm speakers go, some of the Acoustats ( and possibly other E-stat's ) hit 1 ohm at very high frequencies. I know that my Ohm's drop well below 2 ohms but do so at low frequencies. Nothing like asking an amp to deliver all it can at frequencies that already need gobs of current...
As far as the Scintilla's dropping down to .6 ohms, good luck : ) If we put 2.83 volts into an 8 ohm speaker, we have about .353 amps flowing through the output stage of the amp. This is equivalent to one watt of power. If we put that same 2.83 volts into that .6 ohm load, we've got almost FIVE amps ( 4.717 ) flowing throw the output stage. This is literally 13+ times the amount of current. Needless to say, MASSIVE heatsinks and / or forced cooling would be pretty much mandatory. This is especially true if you were "standing on the throttle" for any amount of time. Sean
PS... I don't think that the guy that was using the bridged Perreaux 2150's was using them to drive Scintilla's : )
PPS... People with Scintilla's can charge folks money to break in their power cords. If they rig up adapters, they can use power cords as speaker cables and draw as much or more current through them as a refrigerator would : )
ProSound amps (Crown,etc) were suggested by Gmood1, and it is true that they are generally designed to function with low impedance loads, and include self-protection features if you abuse them too much. However, I note that their distortion specs (for some of the latest models, quite respectable into 8 and 4 ohms) increase greatly with low impedance loading. Is this also true of the audiophile amps mentioned above?
On the cheap, the Krell Ksa-300s would work very well and that is what I would use (better than the classe). The Ksa-150/250's were also made as mono's...the Ksa-250 becomes the MDA-500 and the Ksa-150 becomes the MDA-300. Both of these come up for sale here on audiogon and would work very well. The pass 600's would for sure be the better of the bunch (I've seen your system at the Apogee forum Muralman1, very nice). My choice for amps would be IMHO.
1. Pass X600's
2. Krell MDA 500's
3. Krell Ksa 300s
4. Krell MDA 300's
5. Krell Ksa 250
6. Most of the other older Krell Ksa's and the Classe amps.
Do not try the Krell Kav's or the Aragon's...they may work for a while but will give it up from overheating in the long run. My info. comes from what I have read on the WWW from Scintilla owners. I am sure there are other amps that would also work very well that are not on my list. I left some older amps off the list because of service issue problems that could come up with these companys.
Muralman: Just read over some of your responses. Aragon Palladiums can rum 1 ohm and below with realitve ease. Very underrated amp,especially for driving extreme low impedance loads. Awhile back we did a lil test running 4(at one point we had 6 speakers in total running off of one channel, but the last pair were 6 ohm nominal speakers) true 4 ohm nominal speakers in parallel off of one channel back in 98'. She ran the load all day long(which is a serious statement)at moderate volume with no overheating issues whatsoever. If your wall has the current, the Aragon's will deliver, and they will do it reliably. Too bad Klipsh owns em now. I believe the Palladium 1k's are going to be discontinued real soon. They are the last of the truely industrial quality amps built by this company.
Ritteri, I am not arguing about whether the Palladium has the current to run <1 ohm. I just would not put my money on them surviving high dynamic peak fluctuations.
There are very few <1 ohm speakers out there. I own one of them. My X600 monos have enormous power capabilities, and huge heat sinks. Even they get too hot to touch more than momentarily.
I know a lot of the <1ohm speaker owners. None use Aragons. Many use Aragons on 4 ohm speakers, mostly in a bi amp configuration, the Aragon being relegated to bass panel duty.
Mural: You should tear an Aragon apart, like I stated the amps capabilities are far underrated which is a shame. Even though the heatsinks look small in the configuration their in, its actually surprising the actual surface area of them. The amps run relatively cool with a nominal 3-4 ohm load putting out about 6-800 watts, under 2 ohms they do get hot. But Dynamics really arent a problem for this amp. 1500 watt dynamic peaks at 2 ohms or less is nothing to sneeze at. And I kinda think thats more than enough power for concert level sound levels in even really large rooms wouldnt you say? Now as for how long they would run at this impedance, yes, thats something I never did or tried with them for long listening sessions at a time(nor found the need to really as there arent many speakers made with a 2 ohm nominal load or lower) at maximum volume capabilities. But talking with a few techs a few years back at Mondial Designs, I was told that if each monoblock is given its own dedicated 20amp circuit(which they should really be on to begin with), they would run ANY speaker and are completely stable down to below a half ohm if driven within their(with caution not to overdrive the output stage) capabilites.
Im sure you do have plenty of real world experience, but so do I, with ALOT of different gear in countless configurations(yes I used to be a dealer for alot of high end gear in Ma. and RI.).And I probably have just as much if not more real world experience with what an Aragon amplifier is capable of. No Im not a dealer anymore, nor have I been for the last 3-4 years(got out of the business at just the right time before the tradgedy in NYC)but I do have solid experience with Aragon's running Apogee speakers with ease, as back in 97-98' I sold a few pairs of the older Palladium's to folks with low impedance Apogee speakers. To this day I know that at least 1 of my old customers is still running the combo and enjoying it as much today as he did when he first purchased them 6 years back.
What Im adamant about is a statement that these amps cant run low impedances reliably for extneded periods at high output volumes when I know for a fact this is the farthest thing from the truth.
Here's something else to think about folks. That is, the lower the impedance, the less time that the amp stays in Class A and the sooner it switches over to Class B. The more switching of operating Class that takes place, the "grungier" and less consistent the amp will sound ( in most cases ).
With that in mind, a "typical" amp that is of a "rich AB" design is typically 6 - 10 wpc at 8 ohms in Class A and then switches over to Class B at power levels above that point. If one has a 4 ohm load, the same amp will only run in Class A up to about 3 - 5 wpc. At 2 ohms, you get 1.5 - 2.5 wpc in Class A and at 1 ohm, you end up with .75 - 1.25 wpc in Class A. As such, one would have to have an amp that is VERY richly biased if you wanted to stay in Class A mode for the majority of listening on a very low impedance, low sensitivity speaker. In order to do this, you need an amp that has GOBS of heatsinking and current capacity to say the least. Otherwise the amp will both starve itself and cook itself to death at the same time.
With that in mind, a rather unique approach regarding bias levels were chosen when John Curl designed the Parasound JC-1's. The JC-1's are switchable between "rich biasing" and "very rich biasing" for these purposes. In the lower bias mode, it runs in Class A up to 10 wpc and then switches over to Class B mode. In the high bias mode, it runs in Class A up to about 25 - 30 wpc* and then switches over to Class B above that point. Using this approach, one can let the amps idle in "low bias" mode when not in use, which will keep them as warm or warmer than most other amps, and then switch over into high bias mode when listening. This approach allows one to have the benefits of "ultra high bias" in terms of sonics yet retain the benefits of "medium to high bias" by cutting down on power consumption and heat build-up. I'm not suggesting that this amp is the right amp for Apogee's or any other specific speaker, but that it is a very unique and "user friendly" approach to designing real world products.
Doing the math with the JC-1 as a reference and starting off with the conservative rating of 25 wpc of Class A operation available at 8 ohms, this would give us something like 12.5 wpc @ 4 ohms, 6.25 wpc @ 2 ohms and slightly over 3 wpc @ 1 ohm. All of these figures are based on the amp operating in Class A and then switching to Class B operation above that point. Given that most listening occurs with less than a watt or two being used ( except for rock music ), the JC's should retain their sonic characteristics relatively consistently for most uses with just about any load. This is due to the consistent electrical characteristics that the amp would display while remaining in Class A operation and the lack of switching distortion that all amplifiers will demonstrate when pushed harder.** Sean
* Stereophile measured 27 watts in Class A on their review samples.
** This is all based on theory and not first hand familiarity with this amp. I chose it as i was familiar with the electrical characteristics of the amp as advertised and as measured by Stereophile. Other amps, like the Bear Labs Symphony, Pass Labs X series, larger Krell's, etc..., may perform quite similarly due to the very high levels of bias applied to the output stage.
Sean, that was a relief. I knew I was familiar with your name. The JC-1 is a great amp, so I heard.
Having the X600, I don't have to do math (luckily). I just follow the needle.
At <1 ohm, I need to go to live levels to swing the needle into AB. AND at that point, if it weren't for the needle, I wouldn't have ever noticed.
There is a fellow in our Apogee group who has the most advance listening rooms I have seen. There are Apogee Full Ranges forward, Apogee Duetta Signatures righ and left, with Divas in the rear.
This fellow employs a lot of Aragon's as great workhorses. They do the Duetta Signatures, and are on the bass panels for the Divas, and Full Ranges.
He also says Aragons are great amps for starting points. All these are 4 ohm speakers.
For Scintilla, one fellow tried an Aragon 4004 MK11 that overheated.