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Trying to identify power rating for crossover resistor from 3A


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My tweeter stopped working yesterday. After some diagnostic work, I identified that a resistor had burn up in the crossover (see circled resistor in attached picture). The resistor is 2Mohm, but I'm having trouble identifying the correct power rating. I'd guessed 5W from the size, but it doesn't seem like anyone makes axial 5W 2Mohm resistors. I can certainly accommodate if that is the correct rating, but it made me wonder if my guess was wrong.

Does anyone know the correct part to go here?

IMG_3287.jpeg

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There is no way to get 5W through a 2 Mega Ohm without a Hugh a noun then of voltage.
I would think it might be more likely to be 2k or 200 ohms.

Whatever it is, one could use 2x 4^? Ohm in parallel… as the 4 & 4 in parallel would be equivalent to 2, and then they get 1/2 power each.

Alternatively… if you have any thoughts on bi/tri amping, you are 1/2 way there at this point 😀

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This all started when my tweeter stopped working. I emailed Richard, and he said to mail it in for them to rebuild. So I had the sock (mostly) off to pull the driver anyway. I tested the driver and found that it was fine, which made me think it must be the crossover. Since I already had the sock off, I pulled the mid bass driver, dug through an ocean of foam, and took the picture in the first post. (The crossover is glued to the back of the cabinet in such a way that it's impossible to remove (without knowing some trick I imagine)). I've got plenty of resistors lying around, so I figured why not pull it and see if I have a match. Which brings me to this thread.

But I will call down to LA in the morning, since I haven't been able to identify the value.

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I am pretty interested, as shipping gets harder with distance.

 

49 minutes ago, Ross B. said:

…. The crossover is glued to the back of the cabinet in such a way that it's impossible to remove (without knowing some trick I imagine) …

On some things (like race cars) they’ll bond parts together using Sika flex or other silicon like agent... so often they use a “cheese wire” to remove them, but that is after taking out electrical wires, and coolant lines.

One pretty much looks like a garrotte expert with a wire and broom stick handles, so don’t let the neighbours watch you.

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Everything on these speakers are sealed then screwed. I had to use a screw driver to release the driver carriers, and the crossover is secured firmly to the back panel I don’t think it’s *possible* to remove.

I’ll document the rebuild process. This is by far the most intricately designed speaker I’ve ever dug into.

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@Richard Vandersteen will know….and it’s Hanford, not LA but i almost spit up a bit of Woodford when i read that….made me laugh…in a good way….

Yes, there are some very frugal things that make service more difficult in the “ sock “ series speakers but that also make them an incredible value…

best of luck for a speedy repair !

Jim

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Oh shoot, I feel into the trap of “everything in California that’s not in the Bay Area is in LA”! Well, at least that’s a shorter drive if I ever need to go down there.

I appreciate the sturdy design! Even if it is a lot to get through trying to repair. I feel like I’m breaking in to an ancient crypt that was never meant to be disturbed 😅

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Oof, I’d be nervous cracking open a Model 7… I know it’s all the same stuff, really, but that’s some rarified MDF!

I’ve been going hard on DIY audio the last few months, by now this is just another thing. I just got done building a no-feedback class A Nelson Pass designed amp. I can’t wait to get my speaker repaired so I can enjoy it!

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12 hours ago, Ross B. said:

This all started when my tweeter stopped working. I emailed Richard, and he said to mail it in for them to rebuild. So I had the sock (mostly) off to pull the driver anyway. I tested the driver and found that it was fine, which made me think it must be the crossover. Since I already had the sock off, I pulled the mid bass driver, dug through an ocean of foam, and took the picture in the first post. (The crossover is glued to the back of the cabinet in such a way that it's impossible to remove (without knowing some trick I imagine)). I've got plenty of resistors lying around, so I figured why not pull it and see if I have a match. Which brings me to this thread.

But I will call down to LA in the morning, since I haven't been able to identify the value.

The crossover is glued in so do not try to remove it as we don't have inventory of the old PCB's.  We cut the bad parts out and solder the replacement parts to the leads.  The value of that part is 20 ohms 3 watt.  This speaker has seen a lot of power very high in frequency.  Possibly because of passive bi-amping or the amp is oscillating.  Some amps will oscillate when there is no ground return (cap coupled) on transients.

RV  

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Thanks Richard. I have not passively (or otherwise) bi-amped. My theory is that it was a transient caused by the tone switch on a Hafler DH-110 preamp. I recorded extremely high voltages on the output when switching that unit. I will replace the burned resistor.

Is there anything else you would suggest I inspect in the crossover that might have been damaged as well?

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@Holmz I decided to check the other speaker in case the damage was symmetrical. This time I photographed the process of accessing the crossover board. The official video showing the sock removal process is dead on, so I'll begin with her skirt pulled up. 

 

IMG_3299.thumb.jpeg.0c33edd98d3d8d6f93ee5022cec5ebc6.jpeg

The 8" woofer and overdrive LEDs. Four screws secure it to the cabinet.

IMG_3300.thumb.jpeg.4b8e68d78ca439c1067f755fdd5dcfc5.jpeg

A layer of rubbery calk seals the woofer to the cabinet, even with the screws removed. A few gentle taps with my screwdriver separated the driver assembly.IMG_3301.thumb.jpeg.884e859bed2b48d1029c6848badcc269.jpeg

With the driver removed, you can see the calk (as well as my screwdriver mark), as well as the large magnet IMG_3303.thumb.jpeg.c360b21eb99930fd6305383a73bbd20e.jpeg

The damping foam is cut in a circle to acomidate the voice coil of the woofer. Behind it you can see a flap of insulation. The leads pass through a hole in this flap, and thus must be snipped or desoldered from the driver.

IMG_3304.thumb.jpeg.bff43d6ecf86a96f06c1f4bad2aa02d9.jpeg

Push the damping foam down into the cabinet to reveal the flappy thing. Not sure what material it is exactly, some sort of insulation, maybe 3/4" think. It's stapled at the top, but not at the bottom. Once you push the woofer leads through, it can fold up and out of the way.

IMG_3305.thumb.jpeg.00c0ab160761ea8666fa0e32801a6aba.jpeg

Behind it we find yet more damping foam. Let no one say Vandersteen speakers are poorly damped! This foam isn't connected to anything and can be removed.

IMG_3306.thumb.jpeg.f996ea0bc97a7fc1927e30ec751b045f.jpeg

The damping foam that sits behind the crossover, between the bass cabinet and the midrange/tweeter area. Enough to stuff a small pillow!

IMG_3307.thumb.jpeg.846d32ca939387eac49dab4736e206be.jpeg

At least, the crossover board! The green wire goes to the tweeter, and the tan to the midrange (the two blacks between them are the returns). To the bottom right you can see the red wire going to the acoustic coupler (the black return is next to it, but obscured in this photo). The tan wires next to them connect to the overload LEDs. You can see the back of the binding posts in the center, and the two frequency adjustment knobs to the upper left. This crossover is connected with six screws *and* glued in, as Richard mentioned. At this point I'm convinced Vandersteen speakers are water tight.

There was nothing wrong with this crossover, so I'll be putting this speaker back together. I have a replacement for the burned resistor on order, and will be performing that repair on Wednesday.

@Richard VandersteenThank you for your help and advice, as always. You make a damn fine speaker. I'm curious if my methods here deviate from your official factory process 🙂

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2 hours ago, Ross B. said:

@Holmz I decided to check the other speaker in case the damage was symmetrical. This time I photographed the process of accessing the crossover board. The official video showing the sock removal process is dead on, so I'll begin with her skirt pulled up. 

… 🙂

Thank you Sir!

The wording also compliment the photos🥰

 

2 hours ago, Ross B. said:

Behind it we find yet more damping foam. Let no one say Vandersteen speakers are poorly damped! This foam isn't connected to anything and can be removed.

IMG_3306.thumb.jpeg.f996ea0bc97a7fc1927e30ec751b045f.jpeg

🙂

I suspect that the damping (black gasket Ing and glue) on the cabinet was not something accidentally happened, and was something that went a long way to removing unpleasing sounds.

That chunk of heaven’s cloud, probably violates the forum rules on religious discussion 😇, but maybe that is what is contributing to the sound?  

 

Speaking of which, has anyone read tyhe book, “The Art of Racing in the Rain”?

Edited by Holmz
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I'm glad my pictures were useful! Certainly as someone who just spent much time googling "Vandersteen Model 3 Crossover" looking for reference images, I can appreciate good photos.

I do agree about all the damping. I imagine having everything bounded together by that slightly gummy stuff makes the entire system one unit. No vibrations between parts, no air gaps, etc. It's gummy enough that I think simply screwing down the drivers back into place will reform the seal. At least I hope so (@Richard Vandersteen Can you share the material used for sealing, in case I have need to replace it in the future?).

The heavenly clouds certainly contribute to the sound. I've had experience stuffing super cheap empty-cabinet Panasonic speakers with craft store foam and it made a significant difference. I'm curious about the diagonal mat insulation; I assume it plays some roll in separating the bass enclosure from the mid/treble zone.

I have not read "The Art of Racing in the Rain". What are the salient concepts?

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A much loved Dog plots to fake his own death only to actually die but in doing so tells the great story of his master and the heart wrenching  path his family must travel. The dog having near 24/7 access to the weather , speed F1, and the history channels is somewhat of a savant and a great pup. My great take away is the Tibetan practice of cutting the tail off a truly great dog at death because they are now ready to be a flawed human….is not a bad idea… We need more great dogs and people..

A great book, not a bad movie..

my two cents

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4 hours ago, TomicTime said:

A much loved Dog plots to fake his own death only to actually die but in doing so tells the great story of his master and the heart wrenching  path his family must travel. The dog having near 24/7 access to the weather , speed F1, and the history channels is somewhat of a savant and a great pup. My great take away is the Tibetan practice of cutting the tail off a truly great dog at death because they are now ready to be a flawed human….is not a bad idea… We need more great dogs and people..

A great book, not a bad movie..

my two cents

The first paragraph had me in tears of laughter.
The dog cannot wait to die, because on the history channel it said that the tibetans believe that doings get reincarnated as humans.
The tear keep coming, but laughter part disappears…
There is the owner (Danny the race car driver), his wife’s cancer, which terminates in death, and the eventual maternal grand parents custody fight. 

It is well written, and even better if one likes racing and driving in the rain, or dogs.

If anyone wears make up, then like I told my daughter, this book may have been sponsored by the water proof mascara company. Even the movie is a tear jerker.

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