Crown XLS Drivecore amps & subsonic content (v. we have a problem Houston?) - AVS Forum
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post #1 of 91 Old 12-10-2012, 04:03 PM - Thread Starter
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Does anyone else with a Crown XLS Drivecore have an issue with subsonic content triggering some sort of undocumented "protection" mode in the amp? confused.gif

I have a XLS Drivecore 1500 that I've been using to test out my new DIY subwoofers (each a 2 ohm load) until the Crown XLS Drivecore 2500 I bought arrives from the friendly UPS delivery man. I have the amp setup to run stereo and the subs are a 2 ohm load. Long story short, I discovered while playing the War of the Worlds pod emerging scene the amp goes into a temporary protection mode where the thermal lights flash and the output is muted momentarily. After a few seconds the flashing stops and output resumes. This was at -10dB on my receiver and the amp was not working that hard. (the -10dB lights were on pretty solid). Turning the volume down a little didn't solve the problem. The issue still happened even at -20dB on my receiver.

It's not a straight thermal issue since the amp will play through other extended bass heavy scenes from other movies without any issue. Further, this protection mode triggers at the same point in the scene every time regardless of whether the amp has been pounding for minutes (presumably heated up) or has been idle. When I engaged a 2nd order Butterworth HPF at 15Hz in my MiniDSP and then the scene plays fine. This leads to believe that it's not thermal protection, but something else that's not documented.

As a final confirmation test I tried playing low frequency sine waves through the amp and found it pretty easy to trigger this undocumented protection mode. The lower the frequency, the lower the volume where this "protection" kicks in.

Here's what I found.

Frequency : receiver volume where the protection kicks in
20Hz : no
16Hz : no
15Hz : -4dB
10Hz : -12dB
5Hz : -18dB

As a point of reference the amp seems to run out of power at about -4dB when audible distortion from the sub starts so I didn't push any further. My receiver was fed full scale dual channel mono sine waves (0dB?) from my PC via a digital connection (HDMI).

Are these amps just not suitable for sealed subs where no subsonic HPF is used or do I have a lemon? I sent an e-mail to Crown, but haven't heard anything back yet.
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post #2 of 91 Old 12-10-2012, 05:20 PM
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I have an XLS1500 and I haven't noticed anything like what you're experiencing. This post got me looking for my copy of WOTW, and of course I cant find it...Definitely tuned in to this post so that I can hear other responses.
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post #3 of 91 Old 12-10-2012, 05:37 PM - Thread Starter
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Quote:
Originally Posted by jayHRC51 View Post

I have an XLS1500 and I haven't noticed anything like what you're experiencing. This post got me looking for my copy of WOTW, and of course I cant find it...Definitely tuned in to this post so that I can hear other responses.
What impedance load do you have connected to your XLS 1500 and how is the amp configured?

FWIW, I should point out that I tried this with the clip limiters in the amp both on and off and got the same results either way. I also tried driving the subs with a QSC PLX2402 and it had no issues in the same in WOTW scene (BD) at the same volume.

I'm going to be unhappy if the XLS 2500 does the same thing since I bought it specifically to use on these subs since it was "silent".
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post #4 of 91 Old 12-10-2012, 06:08 PM
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have you turned off the Peakx™ limiters ?

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post #5 of 91 Old 12-10-2012, 06:11 PM - Thread Starter
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Originally Posted by psgcdn View Post

have you turned off the Peakx™ limiters ?
Yes, I tried my sine wave testing with the clip limiters both turned on and off and got identical results either way.
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post #6 of 91 Old 12-10-2012, 07:14 PM
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I'm running my amp 2ohm stereo. No limiters on. It's being fed signal directly from my Marantz receiver.
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post #7 of 91 Old 12-10-2012, 07:29 PM - Thread Starter
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Quote:
Originally Posted by jayHRC51 View Post

I'm running my amp 2ohm stereo. No limiters on. It's being fed signal directly from my Marantz receiver.
Interesting... Have you ever tried playing reasonably high output subsonic sine waves? cool.gif
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post #8 of 91 Old 12-10-2012, 07:39 PM
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No sine waves, but I have played some pretty low movie content at high volume levels. Transformers, Blackhawk down, etc
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post #9 of 91 Old 12-10-2012, 09:41 PM
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I got my XLS 2500 specifically for sub duty as well... I hope that this isn't an issue. I'm pretty sure that it's just you though as there's a member on here (mastermaybe) with 6x Crown XLS amps and he hasn't said anything. Here's his build thread as he just built 4 dayton subs to replace his JTR Captivator. If anything he'll be pushing some low infrasonic frequencies with those subs and i'm sure that he isn't having any problems. Although, I don't know what Ohms he is running...

Take a look at this thread! Just look at all those super bright crown lights... Try not to drool too much... biggrin.gif

http://www.avsforum.com/t/1433137/from-endless-contemplation-to-fruition-james-first-diy-18-sub-how-low-can-you-go-wise/120#post_22504518
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post #10 of 91 Old 12-11-2012, 12:34 AM
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Can you try running 4 Ohm mono bridged? I doubt it will make a difference but it's nominal impedance so different subs could drop lower or go higher and cause a problem in your particular case.
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post #11 of 91 Old 12-11-2012, 04:28 AM - Thread Starter
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Quote:
Originally Posted by jayHRC51 View Post

No sine waves, but I have played some pretty low movie content at high volume levels. Transformers, Blackhawk down, etc
I only just started using the amplifier on these subs on Sunday evening so I haven't played all the usual LFE demo scenes yet. I've played some and so far only had a problem with WOTW. I'll have to step up my game and systematically go through the demo DVDs and BDs and see if there are any other scenes that cause the amp fits.

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Originally Posted by Audiophile1178 View Post

I got my XLS 2500 specifically for sub duty as well... I hope that this isn't an issue. I'm pretty sure that it's just you though as there's a member on here (mastermaybe) with 6x Crown XLS amps and he hasn't said anything.
If it's just me that means somehow I always manage to get problematic gear or manage to find these sorts of problems. I'm still waiting to hear back from Crown.
Quote:
Here's his build thread as he just built 4 dayton subs to replace his JTR Captivator. If anything he'll be pushing some low infrasonic frequencies with those subs and i'm sure that he isn't having any problems. Although, I don't know what Ohms he is running...
Take a look at this thread! Just look at all those super bright crown lights... Try not to drool too much... biggrin.gif
http://www.avsforum.com/t/1433137/from-endless-contemplation-to-fruition-james-first-diy-18-sub-how-low-can-you-go-wise/120#post_22504518
If he's running 4 of the Dayton 18" HOs from a single XLS2500 he should have a pretty similar impedance load in the subsonic range heading down to ~1.7ohms per channel at DC.

Edit: After double checking, this is not completely correct. The Dayton has a DC resistance of ~3.4 ohms. The AV15-H is ~2.7 ohms so it is harder to drive.

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Can you try running 4 Ohm mono bridged? I doubt it will make a difference but it's nominal impedance so different subs could drop lower or go higher and cause a problem in your particular case.
It will be a little difficult since I put Speakon connectors on the enclosures and I need to rig up some sort of adapter to put two speakon cables in series. However, I think I have the right loose connectors to make an adapter harness though. I'll see about trying it tonight after work though admittedly I don't see why it should matter unless the "protection" thresholds are different depending on the mode of the amp.
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post #12 of 91 Old 12-11-2012, 04:45 AM
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Stereodude, my Crown XTi-1000 does the same thing with a 2 ohm load, but not with all drivers. I found some drivers rated 2 ohm are too much for the Crown (OK specifically the 15" Polk MoMo) and others were no problem. My XTi-2002 doesn't have the issue at all. Do you have a full 120V at the wall outlet?

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post #13 of 91 Old 12-11-2012, 05:47 AM
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Interesting. Since you have a 2 ohm load, I'm assuming you have >1 driver per channel. Is it possible to test with just 1 driver and drop the impedance down to see if this resolves the issue? It sounds like it may have a problem keeping up with current demands with strong signals at very low frequencies.


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post #14 of 91 Old 12-11-2012, 06:34 AM
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Quote:
Originally Posted by Audiophile1178 View Post

I got my XLS 2500 specifically for sub duty as well... I hope that this isn't an issue. I'm pretty sure that it's just you though as there's a member on here (mastermaybe) with 6x Crown XLS amps and he hasn't said anything. Here's his build thread as he just built 4 dayton subs to replace his JTR Captivator. If anything he'll be pushing some low infrasonic frequencies with those subs and i'm sure that he isn't having any problems. Although, I don't know what Ohms he is running...
Take a look at this thread! Just look at all those super bright crown lights... Try not to drool too much... biggrin.gif
http://www.avsforum.com/t/1433137/from-endless-contemplation-to-fruition-james-first-diy-18-sub-how-low-can-you-go-wise/120#post_22504518

Ha ha, hear I am.

wow stereodude, sorry to hear about your troubles.

I can add to this...

Funny (not really, but you know what I mean) I saw the identical flashing lights during the pods emerging scene...mine occurred though right at reference running 5dbs hot, but that's not of course to say it could not have occurred at a lower figure like you're seeing, or that I'm pushing my own amp as hard as your 1500. I haven't seen the phenomenon on ANYTHING else since and I've had my current set-up going for about a month now.

But, crucially- and this could be a rather big but- I do NOT recall the amp cutting output. Yep, btw: I'm pushing 2 ohm loads off either side.

Just FYI: never a single issue with any of the six pushing my mains/center/surrounds/heights/wides.

I'm going to check this out when I get home in 6 hours and of course check back.

James

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post #15 of 91 Old 12-11-2012, 06:38 AM
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One more thought: Is the limiter activated? If it is, I bet the 'release' is set to 2 seconds and you've got your answer....

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post #16 of 91 Old 12-11-2012, 06:38 AM
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Honestly, I wouldn't be shocked if these amps are simply running out of gas, down REAL low, below 2 ohms. I mean let's get real, we're asking for a quite a bit out of a $500 amplifier.


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post #17 of 91 Old 12-11-2012, 06:43 AM
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Could it be that the driver load is dropping down below 2ohms and perhaps the XLS can not handle a 2ohm load to begin with so that combined with the dropping down of the impedence possibly below 2ohms?
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post #18 of 91 Old 12-11-2012, 06:50 AM
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^ It's rated for a 2 ohm stereo load and seems to perform well with such on 99.9% of the material it sees in my application.

If indeed a pair of Daytons wired in parallel are running well below 2 ohms down low, this would be an entirely different issue and really have nothing to do with the amp being able to handle 2 ohm loads perfectly fine, of course.

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post #19 of 91 Old 12-11-2012, 07:06 AM
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When I decided to run a pair in parallel off either side of my 2500 I knew this could be an issue, I'm just happy I haven't found it be, thus far, outside of the WOTW clip.


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post #20 of 91 Old 12-11-2012, 07:15 AM
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Can you wire your subs (are they DVC) for 8 ohm and test again? I agree with others that your impedance is probably dipping quite low.

What drivers? How large are the cabs?

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post #21 of 91 Old 12-11-2012, 08:15 AM - Thread Starter
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Quote:
Originally Posted by imagic View Post

Do you have a full 120V at the wall outlet?
Yes, I have a full 120V or a little more.

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Originally Posted by Gorilla83 View Post

Is it possible to test with just 1 driver and drop the impedance down to see if this resolves the issue?
Not exactly. They are sealed dual opposed. If I power only one driver I end up with a passive radiator of sorts, and I'm not sure what the net effect is in terms of putting big power to a single driver. The best option is probably to rewire a single enclosure to be two 4 ohm loads. That will still take some effort to do since I'm using Speakon connectors and don't have 4 conductor cables or the internal wiring to do that, etc.

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Originally Posted by imagic View Post

One more thought: Is the limiter activated? If it is, I bet the 'release' is set to 2 seconds and you've got your answer....
Negative, it does the same thing with them off or on.

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Originally Posted by Martycool007 View Post

Could it be that the driver load is dropping down below 2ohms and perhaps the XLS can not handle a 2ohm load to begin with so that combined with the dropping down of the impedence possibly below 2ohms?
According to the simulation results, the impedance of the enclosures does drop below 2 ohms basically at 16Hz. So, that's probably a key factor here.


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Can you wire your subs (are they DVC) for 8 ohm and test again? I agree with others that your impedance is probably dipping quite low.
What drivers? How large are the cabs?
Oh, I know they drop low. I just wasn't expecting this. The drivers are AE AV15-Hs and the cabs are ~165L net with walls covered with R13 fiberglass.
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post #22 of 91 Old 12-11-2012, 09:12 AM
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According to the simulation results, the impedance of the enclosures does drop below 2 ohms basically at 16Hz. So, that's probably a key factor here.

THIS

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post #23 of 91 Old 12-11-2012, 09:35 AM - Thread Starter
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So after thinking this over since yesterday... (long time I know) tongue.gif

First, my hope is that the XLS 2500 is a little more resilient than the 1500 / has more headroom before this protection kicks in. Second, based on the in room frequency response at the listening position shown here:



It seems pretty clear there's little point in trying to reproduce subsonic content under ~13-14Hz since it should be imperceptible relative to any other sounds the system is reproducing at the same time due to the low SPL level (relatively). So, the use a complementary subsonic filter in the MiniDSP around the same frequency should significantly reduce the likelihood of this protection triggering without taking anything away from the overall LFE experience.
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post #24 of 91 Old 12-11-2012, 09:52 AM
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Interesting. I bet it is some sort of current limiting or DC protection circuit built into the amps to protect against high power demands below a certain frequency. WOTW has notoriously high level sub 10Hz content in parts and I bet one of these spikes of energy below 10Hz is causing it. Now imagine using an LT circuit and boosting the bass the lower it gets with this type of material and what it does to the amps.


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post #25 of 91 Old 12-11-2012, 10:00 AM - Thread Starter
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Quote:
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Interesting. I bet it is some sort of current limiting or DC protection circuit built into the amps to protect against high power demands below a certain frequency.
That's basically my conclusion also.

It would be nice though if this protection feature was documented in the manual. I was showing the subs off to a friend yesterday since I only finished them on Sunday, hadn't tried WOTW before, and got a little concerned when the amp muted the outputs and flashed the thermal lights. Thankfully he's a DIY guy also and enjoyed the ensuing testing and amp swapping that followed. tongue.gif
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post #26 of 91 Old 12-11-2012, 10:16 AM
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^ I agree with you re getting a bit concerned- it's funny cause I was demoing WOTW too to a few guys when I saw the lights, but no one seemed to notice the bass cutting out, as I recall. I'm all juiced up to try this when I get home tonight...I am very much aware of the double flashing red lights you're speaking of on my 2500, but again, for the life of me I don't remember the output being cut. We'll see I guess.

Every time I start considering other amps as an option, two things immediately spring into my mind:

1. The substantial additional cost of a unit that would deliver a scant few dbs more.

2. The fan noise/needed mods for my application.

In the end, I can already hit reference with no problems so it's simply hard for me to justify the additional cost and mods.


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post #27 of 91 Old 12-11-2012, 12:06 PM
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Quote:
Originally Posted by mastermaybe View Post

^ I agree with you re getting a bit concerned- it's funny cause I was demoing WOTW too to a few guys when I saw the lights, but no one seemed to notice the bass cutting out, as I recall. I'm all juiced up to try this when I get home tonight...I am very much aware of the double flashing red lights you're speaking of on my 2500, but again, for the life of me I don't remember the output being cut. We'll see I guess.
Every time I start considering other amps as an option, two things immediately spring into my mind:
1. The substantial additional cost of a unit that would deliver a scant few dbs more.
2. The fan noise/needed mods for my application.
In the end, I can already hit reference with no problems so it's simply hard for me to justify the additional cost and mods.
James

With your new sealed setup that is capable of down to 10hz (For sure), you should definitely consider an alternative. The Crown XLS series are not the best for sub duties. Crown's newer amps in general begin to rolloff much higher than others, even at 20hz where their specifications stop (for good reason).

Fan mod on an ep or epx4000 literally takes 5 minutes, and I knew NOTHING about pc boards, electronic circuits or anything of that nature. I am a financial planner, not an engineer wink.gif

OP, some of that rolloff you see on your graph is exactly what I mentioned before, the premature rolloff of the crown.

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post #28 of 91 Old 12-11-2012, 01:52 PM - Thread Starter
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OP, some of that rolloff you see on your graph is exactly what I mentioned before, the premature rolloff of the crown.
I really don't think so. I measured the response with my QSC and got the same response.

As an aside, I tested the QSC (with a different D/A from the signal chain in my great room) into a 8 ohm load and found the -3dB point to be ~2.5Hz.
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post #29 of 91 Old 12-11-2012, 02:04 PM
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well then all good there I guess. That is a nice response on the QSC, I thinks maybe the 1500 I have headed my way for the mains should be done with a loopthrough first?

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post #30 of 91 Old 12-11-2012, 02:36 PM
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Yeah, I spoke to a crown tech (Kevin) and he said that the roll off business was nonsense and that the xls output's nearly flat to 5hz. I don't know, just relaying what he told me.

I'll know more about my own room soon when I get done measuring, but I've seen/heard some pretty incredible stuff thus far, easily on par if not above my cap and "old" Crown xs900.

BTW: just ran war of the worlds again right at reference (bout 5dbs hot) and while I was getting brief red clip lights, I didn't get the double flashers this time and certainly the output didn't cut out. This was in the 115+db neighborhood!


??????

James

Actual phone call (see pic to left):

 

Tech (responding to laughter): "I'm sorry sir, did I miss something?"

Me: "Yeah, a case of Diet Mountain Dew walking across my living room."

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