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Author Topic: Over excussion in my qrx 218 boxes  (Read 6954 times)

Conrad Muzoora

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Over excussion in my qrx 218 boxes
« on: July 30, 2013, 06:18:02 am »

So i recently added a used pair to my qrx 218 line up for my DJ rigs bringing the total to 6 boxes. This particular pair looks to be in a great shape compared to my older boxes. I personally opened both boxes and sure enough the evx 180B woofers appeared immaculate to my eyes. Usually i run a pair of boxes on each rig and run them interchangeably between the following amps.
1. QSC Plx 3602
2 QSC RMX 5050
3. CREST 8002 (The best sounding of the lot IMHO)

The processing is the same using DBX driverack HPF 36hz BW 12, LPF 91hz LR24, PEQ Freq 36hz Q 0.939 Gain 3db.

This weekend, while listening to Recorded music, i heard the unmistakable crackling sound of over excursion in both boxes while running at reasonably high levels. Well the amp was clipping reasonably (May be 1/3 output) but i have never heard the same happen on the even bigger amps i have tried above. The type of music was the typical that we play as usual. Makes me wonder, did i get a pair of defective boxes? They all seem airtight with no leaks. To correct the problem, i had to remove the PEQ filter and use a steeper slope on the HPF of LR24.
Any ideas welcome
« Last Edit: July 30, 2013, 06:20:19 am by Conrad Muzoora »
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Robert Weston

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Re: Over excussion in my qrx 218 boxes
« Reply #1 on: July 30, 2013, 07:07:59 am »

So i recently added a used pair to my qrx 218 line up for my DJ rigs bringing the total to 6 boxes. This particular pair looks to be in a great shape compared to my older boxes. I personally opened both boxes and sure enough the evx 180B woofers appeared immaculate to my eyes. Usually i run a pair of boxes on each rig and run them interchangeably between the following amps.
1. QSC Plx 3602
2 QSC RMX 5050
3. CREST 8002 (The best sounding of the lot IMHO)

The processing is the same using DBX driverack HPF 36hz BW 12, LPF 91hz LR24, PEQ Freq 36hz Q 0.939 Gain 3db.

This weekend, while listening to Recorded music, i heard the unmistakable crackling sound of over excursion in both boxes while running at reasonably high levels. Well the amp was clipping reasonably (May be 1/3 output) but i have never heard the same happen on the even bigger amps i have tried above. The type of music was the typical that we play as usual. Makes me wonder, did i get a pair of defective boxes? They all seem airtight with no leaks. To correct the problem, i had to remove the PEQ filter and use a steeper slope on the HPF of LR24.
Any ideas welcome

If you bought them used, you may want to open them up to make sure the drivers are actually what should be in the box.  As for the over excursion sound, were you hearing the "metal ball dropping" sound?

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Ivan Beaver

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Re: Over excussion in my qrx 218 boxes
« Reply #2 on: July 30, 2013, 07:14:50 am »



The processing is the same using DBX driverack HPF 36hz BW 12, LPF 91hz LR24, PEQ Freq 36hz Q 0.939 Gain 3db.

 Well the amp was clipping reasonably (May be 1/3 output)
Why do you have an eq boost below the HPF setting?  And yes I would go with 24dB Butterworth for highpass.

How do you figure the amp was at 1/3rd output and clipping?  If it was clipping-it was past full output-hence the clipping.
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Jeff Bankston

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Re: Over excussion in my qrx 218 boxes
« Reply #3 on: July 30, 2013, 07:38:58 am »

1/3 output and clipping does not compute !
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Bill Hornibrook

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Re: Over excussion in my qrx 218 boxes
« Reply #4 on: July 30, 2013, 10:22:28 am »

Any ideas welcome
Set it up along with one of your others that you seem to think works ok
Same room
Same amp
Same program material
Same output level

Then see if your new purchase if behaving differently.

I can kind of see what you're trying to do (putting a slight bump at port tuning) but honestly anything even slightly below that is going to make those drivers go nuts - and they have an Xmax of only 6.4mm (just looked it up).  And believe me, if you're playing current hip-hop there's plenty of LF info below 35hz (I use 21s to cover those gigs).

When you switched to highpass filter type to LR (which unlike BW is down at cutoff... -6dB I believe) that also is a good indication that you were just asking your drivers to do too much. 
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Paul G. OBrien

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Re: Over excussion in my qrx 218 boxes
« Reply #5 on: July 30, 2013, 11:58:29 am »

Usually i run a pair of boxes on each rig and run them interchangeably between the following amps.
1. QSC Plx 3602
2 QSC RMX 5050
3. CREST 8002

And how are they connected to those amps... 1 box per channel or a single amp bridged into the box? A lot of people are under the mistaken impression that the EVX 180B is a 1000w driver because it says so all over the web, but the reality is EV's own spec sheet says it's only good for 600w AES from 50-200hz and with an xmax of only 6.4mm it likely won't even take half that at 30hz. The driver does have a generous voice coil gap with a 1-way mechanical limit of 1"(25mm) so they will take some abuse without damage but pushing them hard at low frequencies is relying more on the suspension than the motor to control cone movement, so I suspect the PO of your new boxes is like many that have been asking too much of these things with too much power at low frequencies and now the suspension is tired so the voice coil bottoms easier. Reconing is a temporary fix that might just be good enough for you if you have never had any problems with the other boxes, but the same will happen again eventually if they're fed the same input signal and power level.
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Greg_Cameron

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Re: Over excussion in my qrx 218 boxes
« Reply #6 on: July 30, 2013, 01:39:31 pm »

And how are they connected to those amps... 1 box per channel or a single amp bridged into the box? A lot of people are under the mistaken impression that the EVX 180B is a 1000w driver because it says so all over the web, but the reality is EV's own spec sheet says it's only good for 600w AES from 50-200hz and with an xmax of only 6.4mm it likely won't even take half that at 30hz. The driver does have a generous voice coil gap with a 1-way mechanical limit of 1"(25mm) so they will take some abuse without damage but pushing them hard at low frequencies is relying more on the suspension than the motor to control cone movement, so I suspect the PO of your new boxes is like many that have been asking too much of these things with too much power at low frequencies and now the suspension is tired so the voice coil bottoms easier. Reconing is a temporary fix that might just be good enough for you if you have never had any problems with the other boxes, but the same will happen again eventually if they're fed the same input signal and power level.

In the right box, those drivers will do a decent job at and a bit below 30Hz. But the QRx is not that box. And certainly they can't take their rated power at 30Hz or below in any box or they'll become a backplate hammer :)
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Bernard Fernand

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Re: Over excussion in my qrx 218 boxes
« Reply #7 on: July 30, 2013, 01:43:01 pm »

From the EV manual:

hi-pass @ 35 Hz w roll-off of 12 dB/octave MINIMUM
cross over range 80-120 Hz w roll-off of 24 dB/octave

If you work within these recommended parameters with proper power you should be just fine.

If you are feed the subs frequencies down to 20 Hz as the op was doing in the thread cited above you WILL have failures.
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Luke Geis

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Re: Over excussion in my qrx 218 boxes
« Reply #8 on: July 30, 2013, 02:24:35 pm »

I have used these exact boxes with the exact amp and can say that if set up in bridge mono mode with one amp per speaker, you will have more boom than you should ever need! Now it sounds as if you are running one sub per side which should yield about 1,200 watts per cab. This is not a lot of power for sub duty in my opinion, but should get the job done reasonably well.

If you read closely in many of the amp specs, you will find that many state when the red lights flicker, there is audible distortion occurring! With subs, clipping signals will be less omni directional and will be rather evident. It may not be over excursion as much as your just hearing the amp going hell with that, i'm just going to try and destroy your speaker instead!!!!!!!!! One way to test would be to set up one speaker to run off one side of the amp and go till you just get audible distortion. Mark the db level down that you collect. Next set the amp up to run that same cab in bridge mono mode. My bet is that you will acquire the same level much earlier on the fader and you won't have audible distortion anymore?

Another thing that may be an issue is because of the DJ's love to see red syndrome..................... Hold on a second, I will get to the point in a second : )     Most DJ's tend to run their inputs into the red, followed by their outputs which also blink into the red. Anytime you see a red lights flicker on the input, or output meter, your probably going to have some form of audible distortion!!!!!!!!!! Now having the inputs slammed into the red may not make it so bad as having both the inputs and outputs red. As with most EDM media, it is bass heavy and the beats are very distinct. In other words the inputs and outputs may only clip when the bass hits on each beat. Bass eats up a lot of headroom and that hit may be what is causing things to clip, overload and cause audible distortion? This is food for thought, not necessarily what is actually happening in your case.

With what you mention in our post above about Drive rack settings, I would not be surprised to see red lights. You have an EQ boost at the knee of the HP filter. 36 Hz is pretty low and to have even a 3db boost there will eat up a bit of headroom. The slopes you mention should be fine, but 33-35 Hz is the typical HP, or low cut point. The steeper the better usually in this spot. Not a whole lot of content is needed down that low, although it is nice to have the floors shake on the low notes when there is!

On to sub power. I feel that the subs are underpowered in your current situation. They say that the things are rated to 4,800 watts peak. So about 2,400 watts should get it into it's program rating and 1,200 watts for its rms long term rating? I prefer to power subs at about 75% of their peak power rating. This would put it at 3,600 watts for what I consider properly powered!!!!! Perfect, we have an amp in your current inventory that will do exactly that. The very nicely made PLX3602 is a great amp that produces exactly what you need and has a built in crossover network and sub sonic filter that without any processing at all, should get those subs working very nicely! In bridge mono mode I would bet you could go from two subs to just one and still have the same amount of impact. Place two subs powered this way in a single location ( not in stereo, but actually placed together ) you will find that you will really get the party shaking! I ran a show with a pair of these subs powered by the PLX3602 in bridge mono mode and can say that the amps were barely even thinking about working. There was more than enough boom and the amps were barely even doing anything to do it.
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Bernard Fernand

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Re: Over excussion in my qrx 218 boxes
« Reply #9 on: July 30, 2013, 02:28:31 pm »

if anyone can help with this problem i would greatly appreciate it,i have blown about about 2 of my subwoofers in my old jbl sr4719a's and i found out it was because i didn't have enough power on them,i know have a crown i-tech8000 and hooked it up to my jbl srx728's and my ev qrx 218s's and have been getting a burning smell but have not blown them,the speakers were used,but i'm wondering is this is because they have never seen this kind of power and they're getting broke in or is it something i'm doing wrong,i have the average and peak settings correct
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