Two issues with crowns is that they take up too much rack space for 2 channels and they have fans which draw in dust to the system.

Keep this in mind when considering them.

Which pro amps don't have fans?

Beat me to it. Also wanted to comment on the "Takes up too much space for two channels" comment. There are very few 1U, 2-channel pro power amps out there that don't cost $4K or more (PowerSoft). Curious to see what amps blazar recommends.

Blazar went with a Lab Gruppen 10000 for his diy subs I believe.

Very nice amp. Not one that many of us can afford though. It's also a 2U unit, though obviously you've got four very powerful channels in that 4U of space. The 10000 does have fans, which I'm sure make some noise as do 99% of pro amps.

I think that is a bad a$$ looking amp! It has me thinking of selling my pair of Emotiva XPA 1's and getting one of these for my mains, just based on the looks alone

YMMV

Pretty much all of them do, and generally are quite audible. I was just saying this as a reminder.

The first gen XLS series are actually very decent in terms of noise.

There is no longer a 2u "requirement" for the latest "class D" designs, but it depends on how much power you want.

Someone mentioned powersoft as a 2u amplifier which can be very pricey but often times the comparison is not apples to apples since powersoft often have WAY more transient power.

Another option is Lab's IPD series for more typical amplifier requirements. The control capabilities of these things are fairly powerful but mostly for pro-applications.

The NAD M27's that I used to replace my crown XLS's with are now fanless and Hypex nCore based. These are quite cool also even in with a stack of 3 of them. They also have 12v triggers which is nice. These things come with 7 channels per box. Unfortunately they are not rack mountable unless you buy some middle atlantic custom racks which aren't exactly cheap. They do look slick in a rack though. The sound quality, especially noise floor characteristics simply blow away the crown xls line for high sensitivity speakers. You can hear ALMOST no hiss out of these things even with high sens. speakers. Unlike the crowns, they do not have any high pass filters or volume attenuators. Because these amps are so quiet, I did not feel the need to use volume attenuation tricks with the NAD's in order to lower the ambient hiss out of them.

The M27's are considerably pricier but definitely better than the first gen Crown XLS's in my application.

I actually considered doing a custom build project with everything I wanted: 12v triggers, ncore modules, low rack space requirement, neutrik speakon connectors, etc. Unfortunately there was no rack mount / pre-made casework available and the cost did not make sense at that point compared to NAD's fully functional new amps.

For main speaker amplification, I went with the new Benchmark AHB2, the lowest signal-to-noise ratio amplifier built so far. This thing is simply the best amplifier ever made in terms of baseline ambient noise. The sound is very similar to the Pass Labs series amps that I have used such as the XA30.5 and XA30.8 while being completely black in terms of noise. The NAD ncore setup is very good also, but not quite as quiet as the Benchmark AHB2. The ncore is slightly brighter in comparison and with my particular speakers, a bit more fatiguing over time. With different main speakers, I might prefer the NAD's "more detailed" top end. In either case, the AHB2 now powers my main speakers and the NADM27 handles the rest of the 17 channels of surround duties.

I will likely add 4 more speakers with the rest of the NAD's channels if I feel it is necessary to complete the Atmos/X surround field.

My experience with the first gen crown xls series for surround speaker duties was quite good. I would not say that ncore based NAD's are some sort of mega game changer for most people. In fact, for most folks looking to do a 20+channel system, the Crowns are considerably more cost effective.

If you haven't tried to setup a "mega" multichannel setup yet, I can tell you there is some seriously awesome fun to had. Crowns represent some of the best amplifier value out there in order to get high channel counts.

My wishlist for the 1st gen crowns could be summarized:
1. I didn't like the styling much but this is not critical.
2. The volume knobs, while functional could not be locked into position (such as what a Lab Gruppen can do).
3. the noise floor was really really bad for high sensitivity speakers such as my mains. The NAD's definitively blow the Crowns away in this department.
4. I do love neutrik speakon connectors and I wish all manufacturers of all amps and speakers would move to these. But we know consumer manufacturers are half insane. Dual pole connectors on the Crowns were awesome and these are also present on the Benchmark AHB2.
5. 1u rack space is technically feasible for these but they went with 2u perhaps to make them "look beefier"? Perhaps they wanted simpler cooling size.
6. 12 volt triggers are lacking in the crowns and are very important if you want to be able to turn them off easily with your other stuff. having 10 amps all go off at once using external 12 volt trigger strips, etc. can lead to these tripping your rack's breakers. You could alternatively leave them on all the time and burn some electricity. I like them off during listening to my mains for music since the crown XLS + marantz 8801 hiss too much.
7. A 4 channel version of these would have been decent in a 4u space.
8. IP based control of all the crowns would be nice but that would get you into the price range of lab gruppen.


I do use a Lab Gruppen 10000 PLM for my subwoofers for a simple reason. I asked Notnyt what brand amp he would use for subwoofers if cost were literally no object and he said a "real" lab gruppen (as opposed to the clones out there). The Lab Gruppen has some loud fans but this thing is crazy powerful. I am fairly certain this thing could melt my subwoofer setup if I pushed it even a little bit. During normal usage, I am using less than 25% of its peak capabilities I think.

The Lab Gruppen is some of the craziest amplification in a 2u rack space besides the powersoft products. The Dolby Lake functions are also awesome. I was able to integrate this into my control4 system for power on/off functions also with some effort using their hexcodes transmitted via IP/UPD port.

Another reminder I just thought of: Some of QSC's products have 4 channels of amplification in a 2u rack space and also have more DSP capabilities. The QSC stuff looks better too... The QSC pricing per channel may be a little more in line with what most people are looking for in a Crown XLS.


I think you get a sense for what kind of amps I would like to see personally for large scale multichannel setups: Hypex ncore modules, pro connectors, pro DSP, fanless, 12v triggers, compact rack space usage. Perhaps, even Tascam balanced connectors the way Datasat and Trinnov gear is setup.

I feel that the "pro" gear and the "consumer" gear should have converged long ago with each having all the benefits of the other. The Benchmark AHB2 gets very close to my theoretical ideal but is pricey to be doing multichannel with it.

Hopefully this detailed description of my experience helps

Which model QSC are you referring to?

RMX 1850HD, I did misspeak a bit it is rated +/-3 dB from 5-50,000 Hz per the spec sheet. Good enough for me.

Crown actually makes or does almost all of that stuff in their higher series of amps. Is this a case of comparing a $399 amp to a $1399 amp ? Crown makes $1399 amps too btw.

You always get what you pay for.

Cheap stuff is cheap cause the good stuff got left out.

XLS is the value leader. But the DSi, XTi, CDi, DCi and etc... Etc... They all exist for different reasons. so does the itech and macro tech lines.

If you need quieter noise floor, remote trigger, more powerful DSP, network control, Wireless connectivity, more power etc... It all exits. Just not in the XLS. I think XLS is a tremendous value as it is, but I'm realistic about what I'll get for such short money. There is few amps that sound better and have the bang for the buck.

Yes great points, comparing apples to apples is important in cost concerns.

For a lot of channels, not having trigger functions was really a nuisance with crown xls. If i just had a single amp, i would probably just leave it on and be done with it.

interestingly, it looks like the input sensitivity on the ahb2 is 9.75v (+22dbu). with 100 watts output at 8 ohms (28.3v), that is only 2.9x or 9.25db voltage gain.


the m27 has a gain of 31.8db and the crown xls2500 32.5db.


so the gain structure would have to be completely reconfigured to compare either of those amps to the ahb2, or so it would seem.


hhmm....

The amp has 3 gain settings. Basically pro and consumer gains are on that adjustable switch.

This is awesome for matching input gain to whatever you want to plug into it and to account for different sensitivity speakers.

does the noise level change when going from the 9.75v setting to the 2v setting?

That's what I do....just leave it on. My xls powers a pair of klipschs. I switched from a Yamaha to marantz receiver and I don't appear to have major issues with preamp voltage. The marantz will begin to clip the crown at high volume. The biggest complaint is the lights. Which seems to be corrected.

Regarding pro amps without fans, there is the Crown K2 amp. it is sealed, fanless and therefore quiet. it doesn't have any dsp functionality though. I have one that I have been using on my mains for the last few years or so. I have called Crown tech support in the past and asked a couple of the techies their opinion on whether or not I should go to their newer xls series from the K2. They both told me to keep the K2 and said when any K amps come back to their place of business, all the guys who work there try and grab it for themselves.

I think the interest in the xls series has been particularly decent sound quality. I have no idea how the xls compares to the k series. If they improve noise floor and some other aspects of the xls, it could definitely be a winner. I would have been more impresses had it been fanless and 1u coupled with a 12v trigger setup.

I honestly don't think any of these features would have priced the crown much higher considering what these things cost to produce these says.

Anthem makes a nice 1u amp but they are quite pricey for what they are.

We all know that consumer grade amps are definitively NOT the best bang for the buck...

A benchmark AHB2 in a 1u form factor, priced under $1000 each, combined with the PEQ such as dolby lake processing (such as in Lab Gruppen PLM)... Would be a industry dominating amp.

The output of most pro audio audio devices and mixing consoles is between +20dBU and +24 dBu. Here is what Benchmark says on their webpage. See the last sentence in particular.
Most input sensitivities are rated based on average input levels. However, the peak levels the amp can handle are much higher. For example, see the following from Meyers Audio for the amp on their UPQ-1P powered speaker.



The Input Sensitivity is 1V RMS (+2.2 dBu), but it says that you need an Input Level 10V RMS (+22.2 dBu) for maximum peak SPL. Notice the correlation between their Input Level and the Input Sensitivity of the Benchmark on the low gain setting?

A few things to consider:
1. The sensitivity provided for any pro amp is the maximum sensitivity. You use the gain knobs to adjust the sensitivity so more input voltage results in the same power output.
2. The Benchmark's low gain setting is easily matched by using the gain setting on any pro amp.
3. The low gain setting on the Benchmark is similar to the Input Level spec from Meyers Sound in that it is showing the maximum voltage the amp needs to provide maximum SPL.
4. The amps I use also have a fixed input sensitivity (no gain knobs). The input sensitivity is rated at 2.1 V rms, but I need an output from the audio device of +20 dBU (7.75V RMS) to fully drive the amps to max.

Some subwoofer amps have variable phase controls and some have a switch to change between 0 and 180 degrees. In a similary way, most pro amps have variable gain controls and the Benchmark just uses switches for 3 preset levels. The high-gain setting is like many pro amps with the gain controls all the way up. The mid-gain setting is like the amp with the gain set to -5 dB, and the low-gain setting is like the amp with the gain set to -14 dB.

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thanks dd. i am actually aware of that information (except for the meyer speaker). what i was pointing out was the difference in input sensitivity of the benchmark vs. just about every other amp on the planet. to have a valid comparison of noise level, that must be considered (lower input sensitivity requires higher input voltage, which in turn reduces noise from the source device, which may be where most of the noise is actually coming from in this case). the 2v sensitivity setting has more noise, which is why i asked about that. it may still be the lowest noise going, but it will be higher than the 9.75v setting for sure.

The problem with 1U is the capacitor height is not there so they need large quantities of smaller ones to fit. Add in that you have to use tiny fans to fit and the really deep chassis makes it quite possibly the worst design available for an amp. It can cool itself properly by using a screaming scroll fan but why?

I do like the AHB2 since they made it a 2U but made it half as wide--if you want two amps they can be placed side-by-side.

My first Class D PA amp was a Peavey DPC1000 back in the '90's--it was a 1U. The thing was deeper than everything else in the rack to squeeze into 1U which was very annoying. Getting that scroll fan up to max speed was annoying but if they used a 120mm quiet high flow variable speed computer fan--that takes 3U. Someday a 3U half-wdith very quiet multi-channel PA amp with full DSP and simple to configure 5" screen and 120mm quiet fan will arrive...someday!

Watching closely...the price of the original series 1 xls amps is dropping online right now...may be able to pick some up new with warranty relatively cheap closer to the drop of the series 2

Great minds think alike. The original XLS amps are dead-quiet even when the fan kicks on, which isn't very often when using them to power cabs say from 80Hz-ish and up...like 7 main speakers in a 7.1 setup. There's a few XLS1500s on EBay listed at $300 with a "Or best offer". I would assume that when buying multiples the seller would go a bit lower. I saved $200 on the pair of RMX2450a I bought on Ebay that exact way. Free shipping too on 100 pounds worth of amps.


I would say if you could get new XLS1500s for $250 each w/the full warranty, that would be a good buy. Would need four amps to power a 7-channel setup, but $1K for that much juice with a warranty is a steal. Compare to buying a 7-channel Emotiva or similar. You're getting another 100 watts per channel and you're not sharing the same power supply for all channels. Would need more than one 15 amp circuit to power them off though for full power, however.

The 1000 is 220 free shipping and 1500 is 280 shipped...give it a couple weeks and I bet the 1000 goes for 199 and the 1500 249 on amazon

If the 1500 gets down to $250 shipped on Amazon, I may wind up with a fully outboard-powered HT rig. At that price it would be too good to pass up. The 1500 puts out 300w RMS @ 8 ohms. Perfect for mains/surrounds. $250 for an almost silent, 600 guaranteed watts amp? Yes, please.

I just sold my crown xls 2500 last night, looks like I got ride of it at an opportune time.

That said the xls was very clean and an overall great amp. But it wont replace my DSI's or inukes. It would be cool if behringer came out with a HT version of their amps. I know it wont ever happen but it would be fun to not longer need to do the fan swap.

I would suggest checking out your local guitar center. They usually put stuff like that on clearance, I got my crown xls 2500 for $300.

I saw the new series on pre-order special with a decent discount a couple of weeks ago but don't remember the retailer. Does anyone happen to know who that was or where the best deal is on these?

I'm using two Gen 1 XLS2000's in mono mode to drive two HST-18's in sealed boxes. With room gain they are fairly flat to 10 Hz. I'm very happy with them. Haven't clipped them yet and they shake the house pretty well in this setup.

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Looks interesting and promising. I've been bugging Crown for 3 years to produce a DriveCore with more advanced DSP.

The big question with these is how is the ULF response. Down 3db at 5hz is ok but anymore raises the question of their worthiness for LF and ULF reproduction. Guess we'll see.