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XLS 602 D Heating problems


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#1 SpaceyDeeJ

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Posted 04 December 2006 - 06:00 PM

Recently I installed a new XLS 602D amp for a customer of mine.
I use the amp in combination with 4 JBL Controll C29 speakers. 2 C29 cabinets are connected paralel on every output of the 602D.

To prevent any clipping, the signal goes through a compressor/limiter before it goes to the 602D ampflifier.

When the amplifier has to work a lot, sometimes it suddenly goes into heat protection !
Even after we placed the amplifier rack in the basement of the etablisement, it still happens....
I have placed two fans in the back of the 19 inch rack the extra blow out the heated air out of the rack and I left 1 HE space under and above the amp.

Can someone please someone tell me what the heck is going wrong here, while the average temp in the basement is somewehere around the 20 degrees.....

#2 Lou

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Posted 06 December 2006 - 08:26 AM

Can you measure any DC on the outputs? Is that 20 degrees centigrade or farenheight?

#3 DGlass

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Posted 07 December 2006 - 10:56 AM

I see you are from Rotterdam so I am pretty sure it's 20 degrees C (68 degrees F) not 20 degrees F. smile.gif

I went to the JBL web site and looked up the Control 29AV speakers. First I am going to assume that the speakers are set to the "Thru" position and not one of the 70v taps. In this way two C29 speakers per side would be about a 3-ohm/600 watt load which is a good power match to the XLS602D. Since the amps seems to work good until after being pushed hard for a while there has to be something else going on either the amp or the load or the system.

In this case it could be a combination of two things. If the compressor is set to hard limiting (brick wall) then you decrease the crest factor of the music raising the percent duty cycle of the Music. Basically meaning the amp is pushing hard all the time with very little difference between the high and low levels of the music and could over heat after a period of time.  This could also cause the speakers to over heat and burn up as well.

Next, looking at the Frequency vs. Impedance chart for the C29 there is a weird anomaly that happens around 4 KHz. It appears that between 3.5 and 5.5 kHz the box impedance is below 2-ohms being 0-ohms (a short) at 4 kHz. Put two of these boxes together and from 3 and 6 kHz the load would be below 2-ohms and 0-ohms between 3.5 and 5.5 kHz.  sad.gif

Put both of these together and yes the amp could be over heating after a whle of being pushed hard.

Possible fixes:

Find a compromise in a Lower Compression setting of the compressor. By increasing the crest factor and decreasing the duty cycle making the amp will work less hard.

Install another XLS 602D and divide the speakers one per amp channel. This way the amp is driving the lower impedance anomaly over a smaller frequency range. Also you'll get about 80 watts of extra headroom.

#4 SpaceyDeeJ

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Posted 08 December 2006 - 02:01 PM

QUOTE(DGlass @ Dec 7 2006, 05:56 PM)
I see you are from Rotterdam so I am pretty sure it's 20 degrees C (68 degrees F) not 20 degrees F. smile.gif

I went to the JBL web site and looked up the Control 29AV speakers. First I am going to assume that the speakers are set to the "Thru" position and not one of the 70v taps. In this way two C29 speakers per side would be about a 3-ohm/600 watt load which is a good power match to the XLS602D. Since the amps seems to work good until after being pushed hard for a while there has to be something else going on either the amp or the load or the system.

In this case it could be a combination of two things. If the compressor is set to hard limiting (brick wall) then you decrease the crest factor of the music raising the percent duty cycle of the Music. Basically meaning the amp is pushing hard all the time with very little difference between the high and low levels of the music and could over heat after a period of time.  This could also cause the speakers to over heat and burn up as well.

Next, looking at the Frequency vs. Impedance chart for the C29 there is a weird anomaly that happens around 4 KHz. It appears that between 3.5 and 5.5 kHz the box impedance is below 2-ohms being 0-ohms (a short) at 4 kHz. Put two of these boxes together and from 3 and 6 kHz the load would be below 2-ohms and 0-ohms between 3.5 and 5.5 kHz.  sad.gif

Put both of these together and yes the amp could be over heating after a whle of being pushed hard.

Possible fixes:

Find a compromise in a Lower Compression setting of the compressor. By increasing the crest factor and decreasing the duty cycle making the amp will work less hard.

Install another XLS 602D and divide the speakers one per amp channel. This way the amp is driving the lower impedance anomaly over a smaller frequency range. Also you'll get about 80 watts of extra headroom.
View Post



Hello,

thanks for looking into this case allready. Though I dont understand where you are ghetting the 3 Ohn from. As far as I always learned, when you put two resistants parallel, you have to devide the amount, and double the wattages.

So when a speaker would be 300 watt on 8 ohm, put a second speaker parallel, you would get 600 Watt on 4 Ohm.

The XLS 602D should do the job on this I was thinking.

Today I have serviced the first amp, and I found out something strange. When I installed the replacement amp last night, I saw a red led burning inside of the amp. This new amp is working fine, but it has not been crowded yet in the bar dancing so I have to wait till saterday night to find out if the replacement really worked out and nothing wnet wrong.

Back to the story, when I was doing dust cleaning insite of the first amp, I found out, there was no led at all on the print..

So now I am wondering if there has been a modification during the past couple of months...

Serial # of the first amp (with no led inside ) is : 8500034324
Serial # of the second amp ( with a red led inside ) : 8500052137.

Looking forward for your answer...

#5 DGlass

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Posted 08 December 2006 - 03:43 PM

QUOTE(SpaceyDeeJ @ Dec 8 2006, 02:01 PM)
QUOTE(DGlass @ Dec 7 2006, 05:56 PM)
I see you are from Rotterdam so I am pretty sure it's 20 degrees C (68 degrees F) not 20 degrees F. smile.gif

I went to the JBL web site and looked up the Control 29AV speakers. First I am going to assume that the speakers are set to the "Thru" position and not one of the 70v taps. In this way two C29 speakers per side would be about a 3-ohm/600 watt load which is a good power match to the XLS602D. Since the amps seems to work good until after being pushed hard for a while there has to be something else going on either the amp or the load or the system.

In this case it could be a combination of two things. If the compressor is set to hard limiting (brick wall) then you decrease the crest factor of the music raising the percent duty cycle of the Music. Basically meaning the amp is pushing hard all the time with very little difference between the high and low levels of the music and could over heat after a period of time.† This could also cause the speakers to over heat and burn up as well.

Next, looking at the Frequency vs. Impedance chart for the C29 there is a weird anomaly that happens around 4 KHz. It appears that between 3.5 and 5.5 kHz the box impedance is below 2-ohms being 0-ohms (a short) at 4 kHz. Put two of these boxes together and from 3 and 6 kHz the load would be below 2-ohms and 0-ohms between 3.5 and 5.5 kHz.† sad.gif

Put both of these together and yes the amp could be over heating after a whle of being pushed hard.

Possible fixes:

Find a compromise in a Lower Compression setting of the compressor. By increasing the crest factor and decreasing the duty cycle making the amp will work less hard.

Install another XLS 602D and divide the speakers one per amp channel. This way the amp is driving the lower impedance anomaly over a smaller frequency range. Also you'll get about 80 watts of extra headroom.
View Post



Hello,

thanks for looking into this case allready. Though I dont understand where you are ghetting the 3 Ohn from. As far as I always learned, when you put two resistants parallel, you have to devide the amount, and double the wattages.

So when a speaker would be 300 watt on 8 ohm, put a second speaker parallel, you would get 600 Watt on 4 Ohm.

The XLS 602D should do the job on this I was thinking.

Today I have serviced the first amp, and I found out something strange. When I installed the replacement amp last night, I saw a red led burning inside of the amp. This new amp is working fine, but it has not been crowded yet in the bar dancing so I have to wait till saterday night to find out if the replacement really worked out and nothing wnet wrong.

Back to the story, when I was doing dust cleaning insite of the first amp, I found out, there was no led at all on the print..

So now I am wondering if there has been a modification during the past couple of months...

Serial # of the first amp (with no led inside ) is : 8500034324
Serial # of the second amp ( with a red led inside ) : 8500052137.

Looking forward for your answer...
View Post

The Red LED you are seeing was part of the design for a short period of time so our engineers could have an idea of things like rail voltage and what they were doing. They were later removed because marketing didn't like people looking in the amp and seeing RED. They serve no purpose other than for our engineers use.

Actual impedance of a speaker will vary because it is a reactive load not a pure resistive load. Thus impedance is a function of frequency and will be different at different frequencies. When a speaker is rated at 8-ohms that is its nominal impedance. In this case the minimum rated impedance for the C29AV is 6.3 ohms (per the manufactures data sheet) put two of these together and the load would be a 3.15-ohm/600watt load, at its minimum.

However if you look at the next page of the data sheet you will see the frequency vs. impedance graph were the anomaly I previously discussed is shown.

Now... letís lets look at it this way you are limiting the signal so the amp never clips. This increases the duty cycle making the amps work harder which also suggest that this system is being pushed to its limits all time. With the duty cycle raised you are probably also starting to heat up the speakers which also lowers the actual speaker impedance. Next you have two speakers per side that are showing basically a short between 3 to 6 kHz to the already being pushed amplifier.  sad.gif

On the phone just a little while ago you said this was in a club. So what you have is a high performance system playing highly compressed club music, being limited to keep the amps from clipping and being pushed to its max by an entry level amplifier, with a speaker load that that at certain frequencies is a short.  In this case you may need to either get another XLS602D and distribute the load or move up to an XS700 or an XTi2000. Yes you have enough power and yes you have 3db of headroom but entry level amplifiers are not designed to handle the same things as higher end amplifiers can do in a high performance system.

#6 baileydogg

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Posted 08 December 2006 - 04:00 PM

RE: the C29AV, that certainly is an interesting freq/impedance curve.

One thing to note is that in the table of specifications on page one lists a minimum Z of 3.3 ohms @ 4.1kHz, which is in disagreement with the printed curve (which shows the minimum Z near zero!)

Wish I had one to test.

Steve Rynbrandt

#7 SpaceyDeeJ

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Posted 08 December 2006 - 05:12 PM

David,

thank you so far for you answer and the invested time on this issue.
I have had a large conversation with a collegue of mine after reading your second answer.
Tomorrow (saterday ) I will contact my reseller for a solution and immedialty delivery of new amps to solve the problem with the customer....

Kind regards !