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Two Cabs "singing" square waves.. Crossover Broken?

#22
Am I getting this right using this calculator?

http://www.diyaudioandvideo.com/Calculator/XOver/

assuming 8ohm loads and only using the HPF half of it?

That works out to a 1st order 6db/octave HPF set about 2900hz and leave the inductor out of it or am I getting this wrong.

Could you do the same with 3rd or 4th order HPF's?

He could change things here if he wants to or replace with the same if you like what you have now.


Edit: got quite a few pieces and parts laying around here that could make useable floor monitors with just a HPF, even good capacitors are cheap. Can you get 3rd or 4th order just using caps only and leaving out the inductors?
 
#24
But why would the capacitor make the sound in both cabinets.

I would try playing with the tweeter unplugged or even with the Xover bypassed just going to the woofer. Also the tweeter could be blown. But on both???

But the symptom of the sound only being noticeable when the signal is low, sounds more like Amp Biasing. If your bias is to low basically you are missing the first half volt of your signal until there is enough to turn on the transistor. This is effectively running in Class B. Instead or Running Class AB like intended.

From What I've heard SVT3 Pro's are notorious for having their Bias getting knocked out of calibration. I had that problem with mine. I don't know about your head.

It may be easiest to plug your head into someone else's cab and seeing if the same thing has happened

I'm skeptical about bad cap, when an electrolytic goes bad, it'll either short (Which would blow a fuse or trip amp protection), or become a smaller value capacitor (because the dielectric drys up). If its shorted thats really bad news. Never heard of dry caps causing an intermittent noise. No one has every proved to me that Bi-Polar electrolytics make audible Crossing distortion, But I've heard that one before.

I don't think there is much point in buying new Caps until you try playing through someone else's cab and playing someone else's head through your tops. Though It seems like a reasonable upgrade to go from NP electrolytics to Mylar or Polyester caps.

Keep us informed.
 
#25
Standalone said:
Well, at any rate, it's pretty clear that it's the cabs. I'll try some cable switching, but I've been hooking up and unhooking and re-wiring everything with my band's live rig cabling and doubt that's it.

I guess I'm left to wire directly to the woofers and see what's up. I'd still love to get a good link or some info on how to choose an x-over. :help:
Click to expand...


Sorry, all my ?'s up there may constitute a hijack. Anyway http://www.diyaudioandvideo.com/Calculator/XOver/ that's the link to the calculator, that whole site is good reading. Here's a little more Invalid Link Removed .
 
#27
There sure is a lot of guessing going on, without some basic speaker troubleshooting techniques being followed.

Assuming the ampifier is indeed ok, it's unusual for a crossover to cause this problem. It's also unusual (though certainly possible) for the tweeter to cause this problem. It is far more likely that the LF driver is the source of the problems and the most basic troubleshooting technique for this is to disconnect the feed to the high frequency driver and listen to the result. If the problem is still there you have narrowed the problem to the LF driver.

The most common cause is overpowering the LF driver, causing one (or both) of 2 things... the voice coil assembly to deform be either blistering/distorting the former/bobbin OR causing mechanical damage to the souspension components of the driver causing the voice coil to become uncentered. There is no easy fix for this other than reconing or replacement of the driver.

The same can happen to the tweeter, but this is generally much less common and limited to thermal damage to the voice coil assy. The series capacitor is also very unlikely to be the cause of this kind of failure, generally they fail open or the impedance increases by a factor of 10 or so upon failure.

It is very uncommon for an amplifier to fall so far out of bias that crossover (not the same crossover as in a speaker) distortion is heard. I think I have seen this maybe once or twice in 30 years.

Hope this helps.

So try this and see where it leads to.
 
#28
agedhorse said:
There sure is a lot of guessing going on, without some basic speaker troubleshooting techniques being followed.

Assuming the ampifier is indeed ok, it's unusual for a crossover to cause this problem. It's also unusual (though certainly possible) for the tweeter to cause this problem. It is far more likely that the LF driver is the source of the problems and the most basic troubleshooting technique for this is to disconnect the feed to the high frequency driver and listen to the result. If the problem is still there you have narrowed the problem to the LF driver.

The most common cause is overpowering the LF driver, causing one (or both) of 2 things... the voice coil assembly to deform be either blistering/distorting the former/bobbin OR causing mechanical damage to the souspension components of the driver causing the voice coil to become uncentered. There is no easy fix for this other than reconing or replacement of the driver.

The same can happen to the tweeter, but this is generally much less common and limited to thermal damage to the voice coil assy. The series capacitor is also very unlikely to be the cause of this kind of failure, generally they fail open or the impedance increases by a factor of 10 or so upon failure.

It is very uncommon for an amplifier to fall so far out of bias that crossover (not the same crossover as in a speaker) distortion is heard. I think I have seen this maybe once or twice in 30 years.

Hope this helps.

So try this and see where it leads to.
Click to expand...
Thank you, agedhorse! The "deformed voice coil assembly" makes the most sense from what I was finding.

I had been testing the flite sitting on end vertically, but I went back up to the studo and, when horizontal, the noise was easily traceable to the left 8" woofer.

My Genz 212 sounds fantastic with the GK, so it's not a bias issue or other amp issue.

The fact that it's happening with two cabs that are not rated very high makes your diagnosis make even more sense.
________________________________________________
I will get into the Yamaha and run an amp directly to the woofer, but I suspect that there is a similar issue with that woofer, even though it's far less noticeable.

I'm still amazed that such an "electronic" sounding distortion can be caused by a physical deformity or mechanical problem with the driver.

I'll post again after I'm sure what's up with the 110.

And thanks, Jaco Who? for cross linking-- I had linked here from that thread...
 
#30
Jim Carr said:
Do each of the cabs do the noise when connected alone? If so, how can that be? They are totally different...
Click to expand...
Yes. I never wire them in series, as one is 4 ohm and the other 8, and my amp has two power amps, one rated down to 4 and one only down to 8.

Looks like both have a damaged driver. The 110 buzz is SUPER subtle. No one would notice it unless they were playing alone and really listening.

The buzzing in the 2x8 is much more noticeable.
 
#31
dmusic148 said:
Blown driver, no doubt. Been there. As explained above, the bobbin, when overheated, will swell up and rub on the magnet. Carefully push the speaker in and out by hand, you'll be able to hear it.
Click to expand...
On the flite, I could hear a sound-- just a little "tap" as I pushed in one of the drivers.

It's funny. I always thought a blown driver would be all distorted and worse at higher volumes....

Oh well. I sure got my money's worth out of that Yamaha, that's for sure.
 
#35
The one that's really quiet, the 110, if you are VERY lucky the noise will go away after awhile-the swollen resin of the bobbin will wear away eventually(been there too, mine still works). On the other hand you may also wear through the wire, and then it will make no noise at all.;)
 

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