NSD:2005 Buzz/Distortion

High power and fidelity from an easy to build cabinet.
Post Reply
Message
Author
njkreger
Posts: 81
Joined: Sat Jun 16, 2018 6:45 am

NSD:2005 Buzz/Distortion

#1 Post by njkreger » Sun May 26, 2019 11:38 am

Hi,

We built 6 OTop12 J-Arrays, 3012HO loaded with the NSD:2005 compression driver. We've been running them bi-amped, mono, with the CD limited at 19v. Limiting and active crossovers are done with a dbx VENU360. They're crossed at 1.2k with a 24dB LR. We don't run them very loud, and it's super-rare that the limiter will even kick in.

I noticed a few weeks back that just one of the NSD:2005's has a slight buzz/distortion. It's not all the time, and it seems to be at the lower frequency range, around the crossover point on up through about 2.2k.

For instance, we were playing a song this morning, and the keys sounded like crap the first go around. We played the same song a few minutes later and it sounded just fine. There's one pastor who speaks that it seems to distort on certain words he says, but sounds fine when the other pastor speaks. Vocals from the band seem to be okay.

I'd figure with a blown driver it would distort across the whole frequency range and all the time, not just at the lower end and only some of the time.

Any thoughts on this, what might be going on, how to troubleshoot it, etc.?

Thanks!

nivlek
Posts: 20
Joined: Mon Jul 16, 2012 7:32 pm

Re: NSD:2005 Buzz/Distortion

#2 Post by nivlek » Fri Jun 07, 2019 2:42 pm

It sounds like it could be a looseness somewhere that is resonating on certain notes...intermittently.

I have had similar experiences with horns in the past, just not this particular brand. If it were mine, I would check the cheap stuff first...

Swap drivers from another cabinet on the other side of the building to see if the vibration/distortion goes with the driver. Thats fairly cheap stuff. You may find a bad driver... or a defect in the horn flare/cabinet.

The following ideas are not so quick, but be patient with yourself, and do some snooping...

Open up the box, and slowly make a thorough visual inspection. Take a small probe and touch the wires, looking for looseness,
between anything that could be a source of signal interruption...while playing some music or tones through the speaker. Look for loosenes, anomalies in the box, loose sawdust or splinters, insulation, etc. that could add to the problem.

If that reveals nothing, get your volt meter out and check the continuity of each single conductor from the speaker cable connector to the driver, while gently probing.

In the past I have found a few wires broken, that appeared to be ok because they looked to be connected, but were only touching (broken by vibration fatigue), yeilding themselves to be an unreliable connection, sensitive to fundamental frequencies.

Also, check the input connectors the same way. I have seen 1/4" phone jacks that didn't have enough tension on the spring loaded finger to make a good connection on the tip of the plug. I've seen rust and corrosion on the connections affect the sound the same way.

If you still have no luck, take a .002" (.05 mm) feeler guage and feel the seal surface between the driver and the horn, there may be a slightly clearance (not desired) between the driver and the mount surface allowing some resonant vibration. If you think that the wood flange is warped, use some carpenter's chalk and chalk the wood side only, bolt the driver up, then remove and see if it is making a good contact (a ring all the way around the driver output area).

Feel for looseness of the driver and the horn assembly. If the bolts aren't tensioned enough to eliminate a gap, vibrations could occur. If you have flat washers on the driver, see if any of the washers will move. Any washer movement indicates looseness.

If the flange is warped, you may need to put a small gasket or oring in the joint to stop the vibration that could be making the offending noise.

Next, disassemble to view everything...you could have a particle of foreign debris (dead spider, ants, sawdust clump, etc.) between the phase plug and the diaphragm, causing the unpleasant distortions. Blow the dust out with low pressure (<20 psi) compressed air
(careful here keep the blower about a foot away) and be sure to blow out (with ~90 psi compressed air close to the circular slot) the magnetic gap if the voice coil is completely removed. Use safety glasses when using an air blower, please. I have seen loose rust particles in the gap, become the offender in intermittent distortion/vibration. Use a flashlight and a magnifying glass to look for debris in the gap.

Next, while the driver is out of the horn, take a small flashlight (as bright as you can find) and hold it behind the horn, shining in toward the joints, looking for light through the joints in the horn. Push lightly on the corner joints of the horn panels, while looking for a gap. If you find one, this could be a source of vibration if the PL was not placed sufficiently or has drooped from the gap,
unnoticed, during assembly.

Reassemble...making sure each step is done to perfection. For example, put a drop of glue on the felt plugs (if it has any) to secure and prevent vibrations and to retain each part in its proper position. Be plucky and particular here. The only permissible movement should be with the voice coil/diaphram assembly. Complete assembly and try it out.

If no luck here, you may want to resolder everything that you previously soldered just in case you may have a cold solder joint.

No luck? You may indeed have a bad driver. You have now eliminated several other possibilities that would STILL exist, if you just jump out there and buy a new driver.

Food for thought.



Nivlek

User avatar
Tom Smit
Posts: 6693
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: NSD:2005 Buzz/Distortion

#3 Post by Tom Smit » Sat Jun 08, 2019 12:16 am

Are you able to locate which cab is doing it? If you can, run only that cab and do frequency sweeps from below, to above the crossover point to cause it to happen. At that point you should be able to figure out which exact frequency is causing it, and run that frequency to locate the noise.
TomS

User avatar
Bill Fitzmaurice
Site Admin
Posts: 26685
Joined: Tue May 02, 2006 5:59 pm

Re: NSD:2005 Buzz/Distortion

#4 Post by Bill Fitzmaurice » Sat Jun 08, 2019 6:25 am

Get a replacement diaphragm. With all those NSDs you should have one on hand anyway. If you narrow the problem down to a driver swap out the diaphragm to rule it out as the cause.

njkreger
Posts: 81
Joined: Sat Jun 16, 2018 6:45 am

Re: NSD:2005 Buzz/Distortion

#5 Post by njkreger » Sat Jun 08, 2019 3:54 pm

Wow, thank you for the extensive replies and help. Seriously. You guys are really incredible.

I did isolate which driver it was, and I ended up contacting Eminence, and they had me send it to them. They replicated the issue pretty quickly and just sent me a new one. I don't really know what was wrong with it, and last I heard they still didn't really know either. But, I've got a new driver, stuck it in there, and all seems well for now.

Thanks again!

-Nathan

Bruce Weldy
Posts: 6563
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: NSD:2005 Buzz/Distortion

#6 Post by Bruce Weldy » Sat Jun 08, 2019 4:41 pm

njkreger wrote:
Sat Jun 08, 2019 3:54 pm
Wow, thank you for the extensive replies and help. Seriously. You guys are really incredible.

I did isolate which driver it was, and I ended up contacting Eminence, and they had me send it to them. They replicated the issue pretty quickly and just sent me a new one. I don't really know what was wrong with it, and last I heard they still didn't really know either. But, I've got a new driver, stuck it in there, and all seems well for now.

Thanks again!

-Nathan
Guess they still had a few of the NSDs left.....good for you! But, as Bill said - get a couple of spare diaphragms while they are still available. I've always kept two spares for just in case....

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

User avatar
Bill Fitzmaurice
Site Admin
Posts: 26685
Joined: Tue May 02, 2006 5:59 pm

Re: NSD:2005 Buzz/Distortion

#7 Post by Bill Fitzmaurice » Sat Jun 08, 2019 4:47 pm

Eminence would likely keep some in stock for warranty. They might even still have some for re-order. All I can say for sure is that they're not making any more of them.

njkreger
Posts: 81
Joined: Sat Jun 16, 2018 6:45 am

Re: NSD:2005 Buzz/Distortion

#8 Post by njkreger » Sun Jun 09, 2019 8:56 am

Just out of curiosity, have you come up with a good replacement for the NSD:2005 in the OTops?

User avatar
Bill Fitzmaurice
Site Admin
Posts: 26685
Joined: Tue May 02, 2006 5:59 pm

Re: NSD:2005 Buzz/Distortion

#9 Post by Bill Fitzmaurice » Sun Jun 09, 2019 9:39 am


Post Reply