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General question about speaker impedance and amps

I was recently told my Dunlavy Sc IIIs present a difficult amplifier load due to their impedance which fluctuates between 5.5 ohms and 3 ohms., in general i am trying to get an idea of how to match amps with low impedance speakers, some basic questions i have:
generally speaking are amps which double there power into a lower load good with low impedances? does it necessarily present a harder load when a speakers impedance fluctuates? in general are class A biased amps particularly good with low impedance speakers, i am under the impression tube amps are not suited for this purpose is this correct?(once again, in general). Also my speakers have an efficency of 91db so i was thinking of trying a lower powered amp that would work well with a low impedance, any recommedations? for example a yba or gamut with 70w to 100w, i would like to compare an amp such as this to the DNA -1 i recently bought so i can decide if i want to send it in for revision or go with the lower powered amp as i've found in the past i have prefered to higher powered amps though i have just started to experiment with the dunlavy's
mkaes
piezo
304 posts
 
audiopile had some real good points, especially about the class A amps. I have a little 45 watt guitar that indeed walks all over larger A/B amps and is suitable for cooking food with. Ditto for the sound improvement over time though i switch from the stock EL84s to Phillips Miniwatts with very positive improvements in tone and a shorter warm up period.

Now to your original issue.. I have a pair of Dunlavy Athenas and i do not think they are very hard to drive at all, especially compared with speakers like Aerial. I'm using tubes, and have heard them with Pass labs ss amps and the bass looses almost nothing with the tubes while gaining hugely in the mids. Find yourself some amps you like and try them out from a listening perspective rather than getting bogged down in the math.
audiopile
13 posts
 
In responce to gregm comment about high power SS amps having hefty Power Supplies. Maybe /maybe not. The power at various impedance spec is the only real indicator of power supply capability. You can definitly find amps that will do 100 into 8 ohms - maybe only 120-140 into 4 and possibly as little as 150 into 2 ohms. These will definitly have crap power supplies and will tend to clip hard and long when overdriven and have sorta soggy bass on most speakers. A lot of even pretty hefty surround sound recievers and surround sound 5 and 6 channel amps will fall into this . Is the scuttlebut I heard that video/surround amps are being tested for power ratings with only one channel driven at a time - is this true? If it is true this would certainly explain the pathetic sound produced by these products under most conditions - since this makes their power ratings about as real world usefull as a top speed for a car being derived from it's terminal velocity when dropped from a C-130 at 15,000 feet.
I absoulutly agree with gregm - listening is the only thing that really matters.
gregm
3,399 posts
 
Audio, I agree that the wattage "doubling" specs can serve as an indication when it comes to SS amps. But there's a limit to how far this doubling can go: the PS and the amplification device. Because, in order to keep energy constant as your amperes go down, you either have to lower the volts or increase the watts (A=W/V). Take a look at a very well presented case here. The VA product of the PS has to be humongous (and very heavy -- PS weight is a good indicator!). Furthermore, specs CAN be misleading (not false, mind you). In the thread above, s/one stated that an amp specs a whopping 72amperes (peak-to-peak)!!! Wow, and they're not lying! looking closely, you notice peak-to-peak: i.e. peak current is 72/2 and rms is 36x0,707= 25A. Excellent -- assuming this is per channel.
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