Members abzurd Posted November 18, 2014 Members Share Posted November 18, 2014 I've been trying to diagnose my latest RCF 522A problem. The highs on one box just aren't as strong as the other and (I think) don't sound as good. It's hard to tell when the balance isn't there between the woofer and compression driver. I figured it was yet another bad amp as all the past issues were with the highs amp. It doesn't appear that's the issue though as I swapped amps between the box that sounds good and the one with the issues and the issues remain in the same box. Before I remove the compression driver I thought I'd ask if, when diaphragms have problems does it always lead to total failure or can it still sort of work? I seems like there may be a bit of distortion at higher volumes, but I really can't tell if I'm just making that up because that's what I want to hear. Should i just pull the driver out, open it up and take a look? If it's not the diaphragm is there anything else that can be evaluated by sight alone? Oh, and I did run pink noise through and the resulting chart shows they are pretty much the same, but it's just not the case. I also swept with sine wave and couldn't really tell anything there either. When playing music you can definitely tell the difference. I used Dave Matthews #41, which starts with, what is essentially a high hat solo. In the good speaker you can hear all the nuance of the stick hitting the cymbal and just a crisp edge to everything. The other just sounds lifeless. The vocals too just don't have as much edge in the speaker that's acting up. Link to comment Share on other sites More sharing options...
Members dboomer Posted November 18, 2014 Members Share Posted November 18, 2014 So you're listening to Dave Matthews in mono when you make the comparison,right? I'd pull the drivers and take a look. Link to comment Share on other sites More sharing options...
Members dennis a Posted November 18, 2014 Members Share Posted November 18, 2014 I've been trying to diagnose my latest RCF 522A problem. The highs on one box just aren't as strong as the other and (I think) don't sound as good. It's hard to tell when the balance isn't there between the woofer and compression driver. I figured it was yet another bad amp as all the past issues were with the highs amp. It doesn't appear that's the issue though as I swapped amps between the box that sounds good and the one with the issues and the issues remain in the same box. Before I remove the compression driver I thought I'd ask if, when diaphragms have problems does it always lead to total failure or can it still sort of work? I seems like there may be a bit of distortion at higher volumes, but I really can't tell if I'm just making that up because that's what I want to hear. Should i just pull the driver out, open it up and take a look? If it's not the diaphragm is there anything else that can be evaluated by sight alone? Oh, and I did run pink noise through and the resulting chart shows they are pretty much the same, but it's just not the case. I also swept with sine wave and couldn't really tell anything there either. When playing music you can definitely tell the difference. I used Dave Matthews #41, which starts with, what is essentially a high hat solo. In the good speaker you can hear all the nuance of the stick hitting the cymbal and just a crisp edge to everything. The other just sounds lifeless. The vocals too just don't have as much edge in the speaker that's acting up. Meter both diaphragms with an Ohm meter to see if there is a noticeable difference. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 18, 2014 Members Share Posted November 18, 2014 Could be some debris in the VC gap, or fuzz in the phase plug. If it was a paper bobbin than blistering of the paper is another possibility, but I think those are Kapton. Don's comment has significant merit too. Link to comment Share on other sites More sharing options...
Members abzurd Posted November 18, 2014 Author Members Share Posted November 18, 2014 Yes, I confirmed it was mono. I'll pull the driver and see if it's anything obvious. I'd rather not take both compression drivers apart. Can I measure the resistance by just using the +/- spades on the driver? Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted November 18, 2014 CMS Author Share Posted November 18, 2014 Yes, (disconnected from the crossover, of course). Link to comment Share on other sites More sharing options...
Members dboomer Posted November 18, 2014 Members Share Posted November 18, 2014 Measuring the resistance might tell you something but if the cause is something foreign stuck down inside it won't tell you anything. The most common cause of something like this in my experience is from liquid getting down in the driver in which case you'll have to open the drivers to fix it. But it may not be the driver at all. You could have some shift in the crossover. You could flip the drivers to the other boxes and see if the problem stays with the box or with the driver. Link to comment Share on other sites More sharing options...
Members nchangin Posted November 18, 2014 Members Share Posted November 18, 2014 Wouldn't it be easier to swap drivers to a diff box to rule out amps.xovers first since these have been an issue in the past? Link to comment Share on other sites More sharing options...
Members abzurd Posted November 18, 2014 Author Members Share Posted November 18, 2014 Sorry if I wasn't clear, but I mentioned in the original post that I've already flipped the amps, which is much easier than flipping the drivers since you have to take the amps out to get to the drivers. That's how I'm certain it's the compression driver and not the amp/crossover. I'll take a look this evening. Link to comment Share on other sites More sharing options...
Members nchangin Posted November 18, 2014 Members Share Posted November 18, 2014 Oh ok, sorry bout that. Link to comment Share on other sites More sharing options...
Members dboomer Posted November 18, 2014 Members Share Posted November 18, 2014 I'm confused. Doesn't a 522a have builtin amps and processing? Link to comment Share on other sites More sharing options...
Members abzurd Posted November 18, 2014 Author Members Share Posted November 18, 2014 I'm confused. Doesn't a 522a have builtin amps and processing? Yes it does. I've taken the amps and swapped them between the boxes, which is a heck of a lot more simple than swapping the drivers. The thing is the same box (same compression driver) has the issue regardless of the amp module I'm using. So it's not the amp/DSP/crossover. It's something about the physical driver itself. Link to comment Share on other sites More sharing options...
Members Unalaska Posted November 18, 2014 Members Share Posted November 18, 2014 I'd guess debris in the VC or even a shifted magnet. Without looking there is no way to say. Open up and look, remember to mark what wires go where to keep polarity correct. Link to comment Share on other sites More sharing options...
Members abzurd Posted November 18, 2014 Author Members Share Posted November 18, 2014 I'd guess debris in the VC or even a shifted magnet. Without looking there is no way to say. Open up and look' date=' remember to mark what wires go where to keep polarity correct.[/quote'] I'm more worried about the shifted magnet. One of the cabinets too a fall in the trailer some time ago. Debris would be difficult to get in as the horn mouth is covered with a thick screen, pretty much a grill really. Not that it couldn't happen but it's unlikely. Link to comment Share on other sites More sharing options...
Members abzurd Posted November 19, 2014 Author Members Share Posted November 19, 2014 Well, the resistance is 5.1 ohms for each. As for removing the compression driver, tat's not happening today. There's no practical way to do it without splitting the box. The problem with that is it's an extremely deep set, yet small headed, phillips screw. That's not a screwdriver I have.... yet anyway. Link to comment Share on other sites More sharing options...
Members dboomer Posted November 19, 2014 Members Share Posted November 19, 2014 Yes it does. I've taken the amps and swapped them between the boxes, which is a heck of a lot more simple than swapping the drivers. Wow, that seems like a lot of work so I was guessing something else happened. Ok, what I'd try next would be to run a sweep tone through both boxes and see if you can locate where it's the same and where it's different. But I think either way you'l eventually have to come back to pulling the drivers and getting physical exam. It is possible that somehow the diaphragm has somehow loosened up and is not bolted down with even tension. Other than that you are looking at dust, liquid or a magnet shift. Magnet shift would be the only thing covered by a standard warranty. Link to comment Share on other sites More sharing options...
Members abzurd Posted November 19, 2014 Author Members Share Posted November 19, 2014 Wow, that seems like a lot of work so I was guessing something else happened. Ok, what I'd try next would be to run a sweep tone through both boxes and see if you can locate where it's the same and where it's different. But I think either way you'l eventually have to come back to pulling the drivers and getting physical exam. It is possible that somehow the diaphragm has somehow loosened up and is not bolted down with even tension. Other than that you are looking at dust, liquid or a magnet shift. Magnet shift would be the only thing covered by a standard warranty. Thanks Don. I've done the pink and sine wave tests with both speakers on as well as just the compression driver. I even switched polarity on the compression driver to rule out that it was mislabeled. Unfortunately the warranty on these guys is long gone. They've been problematic though since I bought them. This isn't the usual defective amplifier issue like the other problems though. I'll pull the driver in the next few days. I just need to get a long phillips screwdriver. Link to comment Share on other sites More sharing options...
Members Audiopile Posted November 20, 2014 Members Share Posted November 20, 2014 I just need to get a long phillips screwdriver. I'll offer than a bone-fide justification to add a tool to one's toolbox is "turning out to be a pretty good day". A few weeks ago I capitalized on my justification to upgrade tool boxes... because the tool collection had outgrown the existing tool boxes. Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted November 20, 2014 Members Share Posted November 20, 2014 You might want to read this before you go in that driver and attempt to pull the diaphragm. A diaphragm not centered in the gap can give issues similar to what you are experiencing. Not sayin...just sayin http://www.gitarren-forum.de/threads/686138-diaphragm-nd651-nd650-8ohm-for-rcf-art-522a-525a-725a Link to comment Share on other sites More sharing options...
Members abzurd Posted November 20, 2014 Author Members Share Posted November 20, 2014 You might want to read this before you go in that driver and attempt to pull the diaphragm. A diaphragm not centered in the gap can give issues similar to what you are experiencing. Not sayin...just sayin http://www.gitarren-forum.de/threads/686138-diaphragm-nd651-nd650-8ohm-for-rcf-art-522a-525a-725a Thanks. Now what does it mean exactly? Does RCF have to do it? Any speaker repair shop? Link to comment Share on other sites More sharing options...
Members abzurd Posted November 20, 2014 Author Members Share Posted November 20, 2014 I'll offer than a bone-fide justification to add a tool to one's toolbox is "turning out to be a pretty good day". A few weeks ago I capitalized on my justification to upgrade tool boxes... because the tool collection had outgrown the existing tool boxes. Sure. I'm not unhappy about an $8 screwdriver. Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted November 20, 2014 Members Share Posted November 20, 2014 Ever have a metal phillips screwdriver get sucked into a brand new JBL 2441 diaphragm on to the pole piece of the compression driver in the field before a show? Happened to me back in 1983..bad day I have never opened up that compression driver model. I have experienced a diaphragm not exactly centered in the gap. Seems to me most of the new stuff is self centered in a machined step on the compression driver these days. Is it possible the guass of magnet is weak? Did that driver get dropped on concrete in the factory? I think Don mentioned shifting. Last of all...did you buy these used or new? If they are used do you know the history? Link to comment Share on other sites More sharing options...
Members abzurd Posted November 20, 2014 Author Members Share Posted November 20, 2014 Ever have a metal phillips screwdriver get sucked into a brand new JBL 2441 diaphragm on to the pole piece of the compression driver in the field before a show? Happened to me back in 1983..bad day I have never opened up that compression driver model. I have experienced a diaphragm not exactly centered in the gap. Seems to me most of the new stuff is self centered in a machined step on the compression driver these days. Is it possible the guass of magnet is weak? Did that driver get dropped on concrete in the factory? I think Don mentioned shifting. Last of all...did you buy these used or new? If they are used do you know the history? Bought new in 2008. Their history has been well documented on this forum over the years. I'm on amp 5 I think as far as replacements go due to a design / manufacturing flaw in the original release of the cabinets. Then a series of gaffs from RCF, including shipping me amps that they knew were defective. That's a long story. The compression driver is recent. One of the cabs has fallen in the trailer in the past, but it seemed OK. Maybe not though. Link to comment Share on other sites More sharing options...
Members abzurd Posted November 21, 2014 Author Members Share Posted November 21, 2014 Cracked the box and pulled the driver. Opened it up and it looks fine. Folded over a post it note to clean out the the gap and did get some dirt out. Took another post it and ran it around the inside and outside of the diaphragm. Here's what it looks like apart. Not really sure what else to do but put the cabinet back together. That should be a blast. It was a bit difficult getting it apart. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 21, 2014 Members Share Posted November 21, 2014 Interesting, so that's not a Kapton bobbin, it's treated paper. Look carefully on the inside at the paper and see if there are any small bubbles in the paper. I can't tell from the photo. Link to comment Share on other sites More sharing options...
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