Originally Posted by Rex Anderson
The answer probably depends more on listening distance, size of room, volume level you want to achieve etc. I'm always shocked when I run my F208's in stereo full range and see the clip lights flash on my ATI AT4003 (200W/ch, no center running, just the F208's). It is very loud and I don't listen at that level very long, but I want to see what kind of headroom I have.
With some movies, running the front LCR full range, clip lights flash at about the point where I don't want to get any louder. Thus, I could use double the power (3 dB of headroom) running full range. That's with F208s and a C208, listening distance is less than ten feet. Doubt I will need more power when I open the piggy bank and get a pair of JBL HDI 1200P subs.
If I had Salon2's, I'm pretty sure I would want more than 200W ch even if crossed over at 80Hz with subs. It sucks that you need twice as much power to get a 3 dB gain, especially if it is just for headroom.
Yeah, I’ve heard several people now cite cases where their otherwise very capable amps clipped (to their surprise) running Revel’s bigger speakers.
I wonder why this is. My guess: All the bigger Revels (F208, F228, Salon2 etc.) have impedances that reach well into the ~3 ohm range broadly throughout the bass frequencies.
None of the ATI amps seem to be officially rated to drive loads below 4 ohms, at least judging by the specs on their website. (If they are, they should make it official and post the specs.) Yet the majority of your power will be going into the bass frequencies, which (for these speakers) will be delivered through 3 ohms impedance.
It seems pretty reasonable then to infer that when the amp clipping indicator flashes, it’s because the amp is struggling to provide enough current at impedances the amp isn’t officially
rated for. I’m sure they have some extra current headroom, but since they’re not officially rated for (or measured at) these impedances, we simply have no idea how well it behaves there under high load.
I’m sure ATI reps would cite happy customers using their amps to power Salon2’s etc., but if they really want to back their products being used to power 3 ohm speakers then they should stand by it and officially rate it as such, along with specifying max power rating at 2 ohms (or at least 3 ohms).
Even the extremely expensive Mark Levinson amps (amps that cost more than Salon2’s), while “stable at 2 ohms” (which is not
something ATI even claims officially AFAIK
?), seem to be too embarrassed to quote any power numbers at 2 ohms.
In contrast for example, Hypex NC1200 has nothing to be embarrassed about — 1200 watts into 2 ohms. Vastly
lower distortion than Mark Levinson too. And can be bought at 5-10% of the ML’s price tag. I’m sure the awesome Harman dealers like those on this thread can do amazing things on price, but I seriously doubt any dealer can approach a 90%-off discount even in the best case
Originally Posted by gsr
The number of watts isn't the only consideration. @RichB
and I are both powering our Salon 2's with Benchmark AHB2 amps that are "only" 100 wpc into 8 ohms and can play them at deafening levels without the clip indicators coming on or the speakers giving any hint of strain. Trust me - I wouldn't want my system to be capable of playing louder than it currently can because it would destroy my hearing. We both previously had ATI AT6000 series amps and have not felt that switching to the Benchmark amps has been a downgrade in any way. Both of our rooms are pretty good sized - mine is about 16'x26' with a vaulted ceiling that slopes up to about 14' high and the room has a large open doorway that goes into the eat in kitchen (my room is the typical "great room" above a 2 car garage that's very common on newer reproduction colonial houses in the northeast). Rich's room is also fairly large.
Maybe the AHB2 is more capable at higher currents, and so might actually be equal or better at low impedance, which as described above is what matters the most for these big Revels. ATI amps deliver more power into 8 ohms, but you’ll probably never come close to using it all, since only the mids/treble of these speakers will be using the >6 ohm capabilities of your amp.
Therefore I’d lean towards the Hypex NC1200 at this point, which is rated for 400 watts into 8 ohms, 700 watts into 4 ohms, and 1200 watts into 2 ohms.
Regarding the NC500, it’s still a consideration. I initially put in an order for a NC502MP unit but canceled it for doubts about power until I’m sure what I want, so I’m taking my time thinking it over. Right now I’m leaning towards something that has excessive headroom on the amp side, since it seems the biggest risk of damaging a speaker is amp clipping. In reality I doubt I will ever push it that hard as I’m not usually a extreme SPL listener, but the peace of mind is nice.
I do worry a bit about protection circuits etc., which someone mentioned above. It’s not clear though that Hypex modules are inferior here at all, since according to the data sheets every Hypex module has a microcontroller with protection logic to shut down if conditions are detected like out of spec voltage, current, and temperature conditions, as well as direct short detection, power supply failure detection, and other safety logic — all built in as standard.
However some units of even further and add additional protection, monitoring, and active cooling logic on top, e.g. Vera Audio. But you do pay a premium for it. I’m not sure it’s necessary vs the default protections built in. Anyway, the research continues