Hi there,
I have an XLS 2500 driving a pair of Hivi SP10 subs (with a CSS APR12 per enclosure) and I wanted to respond directly to your questions for anyone contemplating one of these amps. A little context first however; I am an audio nut but am no professional. All I have is my ears and years of tinkering. I have an Emotiva UMC-1 pre pro running into a Rotel RMB 1095 for main, centre and surrounds. I had a Rotel RB 1092 (1000x2 into 4 ohms) for my subs. I replaced the RB 1092 with the XLS after reading a review at
Andrew Robinson Online and was intrigued about what impact a professional amp would have on my home made subs performance.
So my answers are as follows:
1) If you have them on a signal-sensing power strip, did that cause them to be noisy?
I have a power strip that switches my system when the UMC-1 switches and it causes no noise in my system including the Crown.
2) Have you ever heard the fans come on from the listening position?
No. The fan (there is only one in the box) is not operational when the unit is cold. After hours of running the fan is operating but it can only be heard if I put my ear right up to the front of the unit. My XLS shares a cabinet with the Rotel 1095. This is a class A/B amp and runs warm all the time. Part of the reason for trying the XLS is that in summer the Rotels have over heated on occasion in this cabinet as the cabinet has inadequate space/cooling. The RB 1092 didn't like sharing this cabinet with the 1095 and it would also over heat despite being a D class amp itself. As I have limited spousal tolerance for my hifi affliction I can't put my amps outside of this cabinet. So replacing the expensive Rotels with the more modestly priced and seemingly robust Crowns has its benefits in my lounge.
3) When the fans come on, how close do you have to be from the amp to hear them?
Very close, see answer above. Mostly I don't listen for the fans, I feel for them as they are so quiet it's impossible to hear them with any sound playing.
4) If you have one hooked up to mains, is there any hissing? If so, how close does one need to be to hear it, and how efficient are your mains?
No hissing, no noise. They are just quiet.
On the matter of gain matching I have found that the Crown is more sensitive than the RB 1092. In my system this is a good outcome. I run the gain all the way up at 10. It's my understanding that this simply means that there is zero attenuation on the input signal. Consumer amps like the Rotels don't have gain pot's; they just accept their input as it is presented by the pre-amp. Running the gain at 10 on the Crowns is actually like running it like the Rotels; ie with zero attenuation. In other words the gain control adds no additional boost to input signals, rather it simply cuts the input level at anything below 10. At 10 there is no cut applied (some professional amps I have seen actually have the end point on the pots marked as zero and the zero gain marked as negative infinity for no input signal if that makes sense). I figure this is better than adding in resistance (cutting gain) to the signal before it hits the Crowns' amps. This has no negative impact (as far as I can tell) as all my speakers (inc subs) are dead silent with no program playing.
In this way I gain a little sensitivity over the RB 1092. This is good as my subs are not as sensitive as my main, centre, surround speakers (Dynaudio's) and once I put the Crown into my system I was able to re-balance my main speaker levels up relative to my subs (previously with the 1092 running the subs my mains where -3db down in my UMC-1 setup menu for the Dyn's).
The limiters are a real boon. After installing the XLS I ran my favorite Bluray bass test passage from Tron Legacy - the passage from the entry to the grid to the end of the light cycle scene and noticed that I could readily drive the Crown into its clip region on the very loud bass sections. I have subsequently engaged the limiters and now need not worry about damaging my subs or the amp. Lord knows what kinds of clipping I must have been driving my Rotel 1092 into because without the visual indication of the clip lights you just can't tell when sub woofer amplifiers are being over driven - picking distortion from subs is not possible in my system/experience when the rest of the system is running cleanly.
Finally my cabinet has solid doors so once installed I've not seen the somewhat garish front panel lighting as it's hidden from view.
Sound quality? Well again with subs it seems somewhat hard to judge but I can say that the XLS is every bit as good as the RB 1092 which is an amp that in Australia retailed for multiples of what the Crown is priced. Heaps of clean, tight bass is what it gives and without the worry of over driving the amps into clipping.
Perhaps I'll get a second and bridge them both for 2400 watts into each of my subs.....
