Please help me identify possible sources for this audio crackle (Yamaha NS-1000 speakers)

[TB2]

Please do not touch on the highly durable Be-mid and Be-high; to touch on or to have repair service on the Be-midrange and/or Be-tweeter should be your very final option!

First, you need to check inside wiring from binding post to LC network, LC network to attenuators, and attenuators to SP drivers' wiring terminals.

Second, you should check the attenuators; I fully disassembled-cleaned-reassembled them (intensive technical skill needed!); further details will be described afterwards hopefully this evening.

In case if you would still have the problem,

Third, you would please check the wiring and capacitors on the LC network boards.

Thank you for your detailed feedback. Are you sure that the kind of noise heard in my videos can even be caused by the attentuators or wiring? In particular, if I do a frequency sweep (let's say upward), the noise will start at a given frequency but if I then lower the frequency back down, the noise persists beyond the frequency where it initially started and only disappear at a lower frequency. (same when coming down until it starts and then going back up). This, to me, indicates that something overcomes a "stickiness" at a certain frequency to start vibrating, which it can continue doing even when returning back down below the initial "unsticking" frequency, as it is already lose and continues resonating. I'm no expert, but I wouldn't know that the electronics (in particular the attenuators) could cause this behavior.

 

[MAB]

Sweep just the driver, no crossover. Start at 500Hz or so just to be safe.

UPDATE: The seller immediately offered me a 300$ discount after I showed him the videos and told him that used JA-0801 speakers go for around 300$ upward. My guess is he knew of the problem. In any case, I'm OK with this.

Now to repairing it...

I finally had the time to very carefully disassemble the unit. The rubber gasket gave me quite a bit of trouble. I have no experience with the JA-0801 so I'm not sure, but I think these had been refurbished before. One of the wire contacts had a sticker "yellow" on it, so at the very least, the speaker had been removed before, and it seemed to me that the gasket was held in place very tightly with more glue than normal. I tried using a hair dryer to soften the gasket and glue but that did basically nothing. In fact, the metal mesh itself was glued on to the speaker quite tightly. I finally managed to remove the gasket and mesh with minimal damage by using a credit card, insulating tape to protect the metal, a flat screwdriver and a bit of force.

View attachment 251756View attachment 251757View attachment 251758View attachment 251759

After removing the dome assembly and inspecting everything visually, I can't really find any problem. The dome looks very well attached to the coil.

View attachment 251755

I could only find a few very minor things:

#1 a tiny piece of copper-colored (but magnetic or at least statically charged) material that sat on the edge of the dome. I guess it's possible that this tiny metal piece vibrated against the dome at certain frequencies but I can't imagine how it could cause that much noise. I removed it very carefully using a small blade that the metal piece jumped to quite readily due to the magnetic field so I could hold it against the knife using a finger and remove it without touching the beryllium dome.
View attachment 251753
View attachment 251754
#2 a bit of a goopy feature on the dome, also visible on the first picture above. To me, it just looks like a little bit of the same glue that attaches the dome to the coil. Maybe during refurbishment some of it got onto the dome where it shouldn't be, but I don't see how this could cause a problem.

#3 there are two or three tiny specs of metal dust in the small gap of the magnet where the coil normally sits. I suppose it's possible that these were rubbing or jumping against the coil. No picture, but it's really just some specks of dust in the magnet. Again I don't see how that could cause so much noise.

Any opinions? Do you see something on the pictures that I don't see? Can it be that these dust particles caused the noise I posted?

Debussy - Clair de Lune: https://streamable.com/ksugwq
Frequency generator: https://streamable.com/hk95ie

Otherwise, I think I'll just try to clean up the unit as much as possible and reconnect it for another frequency sweep.

Do a sweep on the bare driver. Start at 500 Hz or so. Use care, bass frequencies are not attenuated without the crossover. If the audible defect is not present, you either fixed it or the defect is in the crossover or volume pads.
TBH, I would have done the sweep on the bare driver before disassembly! If the defect is elsewhere it saves the driver disassembly. It also gives you a baseline to compare before and after if you do disassemble.

 

[MAB]

Thank you for your detailed feedback. Are you sure that the kind of noise heard in my videos can even be caused by the attentuators or wiring? In particular, if I do a frequency sweep (let's say upward), the noise will start at a given frequency but if I then lower the frequency back down, the noise persists beyond the frequency where it initially started and only disappear at a lower frequency. (same when coming down until it starts and then going back up). This, to me, indicates that something overcomes a "stickiness" at a certain frequency to start vibrating, which it can continue doing even when returning back down below the initial "unsticking" frequency, as it is already lose and continues resonating. I'm no expert, but I wouldn't know that the electronics (in particular the attenuators) could cause this behavior.

If not the driver, yes crossover and controls can cause very odd issues.

Given you description ind diagnosis so far, I suspect a rubbing voice coil. But can’t rule out crossover.
You have a good opportunity to test the driver alone. Then the driver back in the speaker.

One more comment on testing the bare driver. If your amp makes a turn on or turn off noise, you need to avoid that. Which means connecting and disconnecting the driver while the amp is powered on!!! Which means you need to not short the amps leads while it is powered on.
And, volume starts at zero.

Hope this helps.

 

[Doodski]

Hmmz. That voice coil looks dark colored to me and the dark area does not look like the other lighter colored area of the voice coil. Can we see the voice coil in a couple of close up pics and at different angles? Can you measure the voice coil with a Ohms meter; have you done that already?.

 

[Doodski]

OH, and smell the voice coil to see if it smells burnt.

 

[sq225917]

If you have continuity across the coil wires and thd resistance matches the other channel within a few percent don't worry about the coil.

Inspecting the former, and how round it is would be my next move. I'd make a go/no-go guage based the two diameters of the magnet gap. If you ask yamaha Japan they will give you these dimensions if you don't have a suitable way of measuring it.

As noted above you might find the coil is out of round, if it is theres really not much you can do other than givenit a squeeze.

 

[Doodski]

If you have continuity across the coil wires and thd resistance matches the other channel within a few percent don't worry about the coil.

Not necessarily because the voice coil could have a intermittent break in the wire that is only noticeable when the driver is in operation. At this point don't discount anything, especially when the driver is disassembled already. Check everything, suspect everything till something leads you to a fault. As was said a long time ago, "Divide and conquer." Divide that speaker into sections and address each part thoroughly so you don't go in circles trying to determine the cause.

 

[MAB]

Hmmz. That voice coil looks dark colored to me and the dark area does not look like the other lighter colored area of the voice coil. Can we see the voice coil in a couple of close up pics and at different angles? Can you measure the voice coil with a Ohms meter; have you done that already?.

Good eye. That might be a partially blown coil. To add to what Doodski said, if partially blown It will show lower resistance compared to the other speaker’s voice coil.

 

[TB2]

Thanks everyone for the great advice!

I confirmed that it's the speaker (not the electronics) and I think I now know what a burnt voice coil looks like. I can't say that it smells like anything. Here are three more pictures and a close-up:



Now that I know what to look for, I think it's pretty obvious, so I didn't bother removing the other driver to measure its resistance. Or is there still any doubt that this one's toast?

 

[Doodski]

Thanks everyone for the great advice!

I confirmed that it's the speaker (not the electronics) and I think I now know what a burnt voice coil looks like. There are three more pictures:

Now that I know what to look for, I think it's pretty obvious, so I didn't bother removing the other driver to measure its resistance.

Yes, it has justtttt been burned enough to discolor it and break the adhesive so that in pic #...8587 the coil appears to have abraded against the magnet assembly. Any idea if the dome complete with voice coil is available for purchase or is it whole tweeters only?

 

[Doodski]

WeirdO double post. Deleted.

 

[MAB]

Thanks everyone for the great advice!

I confirmed that it's the speaker (not the electronics) and I think I now know what a burnt voice coil looks like. I can't say that it smells like anything. There are three more pictures:

Now that I know what to look for, I think it's pretty obvious, so I didn't bother removing the other driver to measure its resistance.

It does look burnt. Can you get a DC resistance measurement? I am anticipating something much different than 4-8 Ohms. Agree with Doodski, looks like the voice coil is displaced a bit. Perhaps there was a rub or obstruction that started this off.

 

[TB2]

Okay I went ahead and took out the healthy driver just to be sure. But I didn't desolder it, if that makes a difference! I measured it as it was.

I have two (cheap) multi-meters. They read 2.0 and 2.6 Ohm for the healthy driver, and 6.8 and 7.4 for the burnt one. I honestly don't see any displacement, but Doodski if you're seeing abrasion I bet it's there

Now if I source a replacement, is there anything in particular I should watch out for? And is there something I should check with the speaker electronics to make sure this was not caused by a fault that would kill the replacement, too?

 

[Doodski]

Now if I source a replacement, is there anything in particular I should watch out for? And is there something I should check with the speaker electronics to make sure this was not caused by a fault that would kill the replacement, too?

The tweeter is burnt a little bit but not horribly compared to others that have been fried by a heavy hand. That's why it still works and gives you a bad resistance reading but still gives you one at all. If you can swap the good tweeter (Is it good ?) for the bad one and see if it works good with each crossover. You could do a visual inspection of the crossovers too checking for bulging capacitors, leaking capacitors and burnt coils.

I indicated in the pic where the displacement appears to have occurred.

 

[MAB]

Okay I went ahead and took out the healthy driver just to be sure. But I didn't desolder it, if that makes a difference! I measured it as it was.

I have two (cheap) multi-meters. They read 2.0 and 2.6 Ohm for the healthy driver, and 6.8 and 7.4 for the burnt one. I honestly don't see any displacement, but Doodski if you're seeing abrasion I bet it's there

Now if I source a replacement, is there anything in particular I should watch out for? And is there something I should check with the speaker electronics to make sure this was not caused by a fault that would kill the replacement, too?

Before you de-solder any more drivers, make sure you know the polarity of the wires, in case it isn't obvious!!! Take a picture if you haven't already.

Your really nice picture really looks like burnt coil. Very possibly due to a rub. Although it could be a partial burn that delaminated the coil, leading to the rub. I am pretty certain you need to replace this. But, I am not 100% certain yet.

Your resistance measurement with the driver still wired to the crossover isn't valid. You are measuring the driver in parallel with the volume attenuator and the two inductors and resistors that make up the filter. To make a valid comparison, need to de-solder at least one terminal. Here is the crossover to illustrate the additional components you are measuring at the same time.

Yamaha-NS1000

I would de-solder one wire from the good driver, make the measurement again to compare to your potentially bad driver.

 

[TB2]

Thanks again. I'm not sure when I'll have the chance to come back to this project, but I'll report back when there's any news.

 

[TB2]

@dualazmak, so it was the driver after all. I'll be sourcing a replacement in Japan and I was wondering if you have any tips for me. I was going to just browse jmty, mercari and ebay, but maybe you have a better idea where I can get a JA-0801 in good condition for a reasonable price? I saw a nice pair of NS-1000M at hard-off but never any drivers so far. Thank you for your advice!

 

[dualazmak]

As for the SP drivers for NS-1000 and NS-I000M (and other Yamaha drivers), I occasionally look at "Yahoo Auction" web site, but only in Japanese, and I do not know about the possibility of shipping abroad; it would be depending on your possible communication with the seller.
Present search result with key word "JA-0801";
https://auctions.yahoo.co.jp/search...q=-1&oq=&sc_i=&fr=auc_top&p=JA-0801&x=38&y=21
I hope your web browser will properly translate these into English.

 

[dualazmak]

"Hard-Off" is a big company and is reliable enough with good reputation and guaranteed QC on used audio gears. They have very well trained technical staffs. They even add some warranty and free send-back refund system for odd non-functioning gears.
https://www.hardoff.co.jp/
https://netmall.hardoff.co.jp/
I recommend you to communicate/negotiate with them by e-mail for possibility of "JA-0801 driver(s)" to be detached from their QC-passed NS-1000 and/or NS-1000M.

I just found they also have overseas operation;
https://www.hardoff.co.jp/shop/overseas_store/

BTW, where are you locating?

 

[sq225917]

If you are US based there's a guy in the Midwest who strips ns1000 for parts and sells the guts singly. He has a good rep for selling only on spec parts.