My Dayton ND105-4's have died a not so peaceful death. But why?

[fjhuerta]

Saturday night I had a long (+5 hours) listening session with my wife. We started at sane listening levels and ended up with quite a (sonic) boom (from smooth Jazz to Queen and everything in between).

I was feeding a pair of speakers based on a single ND105-4 and a 1" tweeter with a Rotel RB-1070 crossed over at 70Hz to a sub. 200W RMS @ 4 Ohm. I guess you know where this is going...

The Daytons never bottomed out or gave any indication they were about to die. Actually the Rotel did - it went into protection mode a couple of times. I have no idea why When we finally went to sleep both speakers sounded as they always had.

But the next day I noticed one of the speakers sounds strange - I have no other word for it. Very little bass and mids sound weird. The other one's woofer is dead. Or so I thought. It actually emits some mids and upper mids at a very low level.

I know they are dead and I know PE may not honor the warranty But I wonder what happened. They never bottomed out or gave any indication I was about to kill them... any ideas?

[johnnyrichards]

Pe doesn't match Xlim.

[fastbike1]

Are you sure you didn't fry something in the crossover?

[cwad8505]

Are you sure you didn't fry something in the crossover?

+1

[Chris Roemer]

+1

200w, with protection running, is a bit more power than the (30w ?) v.c. is rated for.

Relieved from lower bass duties, you probably melted the coils (or distorted the formers from heat) WAY before you ran into any excursion issues (at +/-10mm).

Chris

[DanP]

Pe doesn't match Xlim.

Exactly. These woofers are only rated for 30 watts RMS, but the Xlim is 10mm I believe. These are one of the rare drivers where you'll overheat the voice coil before they bottom out.

Dan

[fjhuerta]

+1

Well. The woofer x-over does have a couple of BP caps in it, so it could be possible.

I'll disassemble then sometime this week. If the Daytons actually survived the torture test, my respect for them will be very high.

[fjhuerta]

200w, with protection running, is a bit more power than the (30w ?) v.c. is rated for.

Relieved from lower bass duties, you probably melted the coils (or distorted the formers from heat) WAY before you ran into any excursion issues (at +/-10mm).

Chris

This is what I'm thinking could have happened. I suppose that while I was feeding the drivers and the coils were hot everything was "fine". When they cooled, I think a couple (a lot?) of turns may have become short circuited.

Still - what an excursion those drivers have. If their power handling matched their displacement they would be the driver to beat at 4" (at least from those I've used).

[benchtester]

In a similar vein to the deformed former: maybe the magnet wire insulation is melted and now bumpy, and rubbing in the gap. Is there any extra drag if you move the cone in and out by hand?

[fjhuerta]

I'll take an impedance measurement today and see what I can imply from it. Then I'll disassemble the speaker and find out for sure.

But...

I just found out the ND105 is out of stock UNTIL JULY 11, 2012!!!!!

PE, why????

[fjhuerta]

Now I know what happened.

One of the woofers voice coil is absolutely, completely glued to the magnet.

The other one is halfway there - it scrapes the magnet and sometimes stays stuck.

I haven't felt this dumb since I was almost suspended from an electronics class because I wanted to see how caps blew up.

[Wolf]

Now I know what happened.

One of the woofers voice coil is absolutely, completely glued to the magnet.

The other one is halfway there - it scrapes the magnet and sometimes stays stuck.

I haven't felt this dumb since I was almost suspended from an electronics class because I wanted to see how caps blew up.

Nothing like a welded voice coil to reassess the volume level.
I've only seen that once persoanlly, but it was a bad amp channel and fried a 12" driver.

Later,
Wolf

[fastbike1]

Look on the bright side. Now we have at least one data point to demonstrate that the ND-105's won't bottom before they melt. Nothing better than empirical data.

Now I know what happened.

One of the woofers voice coil is absolutely, completely glued to the magnet.

The other one is halfway there - it scrapes the magnet and sometimes stays stuck.

I haven't felt this dumb since I was almost suspended from an electronics class because I wanted to see how caps blew up.

[Pete Basel]

Now I know what happened.

One of the woofers voice coil is absolutely, completely glued to the magnet.

The other one is halfway there - it scrapes the magnet and sometimes stays stuck.

I haven't felt this dumb since I was almost suspended from an electronics class because I wanted to see how caps blew up.

If you are up for taking one of the drivers apart I'd like confirmation that the VC former is not metallic or thermally conductive. The spec says polyimide, but it is always good to confirm it. I generally prefer a conductive former for just this reason. They probably would have survived with a bit more heat capacity and sinking.

[fjhuerta]

If you are up for taking one of the drivers apart I'd like confirmation that the VC former is not metallic or thermally conductive. The spec says polyimide, but it is always good to confirm it. I generally prefer a conductive former for just this reason. They probably would have survived with a bit more heat capacity and sinking.

Just tell me what to do and I'll go ahead and rip them apart.

[Pete Basel]

Cut the lead in wires at the input terminal.
Then either cut with an exacto or similar the
rubber edge and then the spider. You should
then be able to pull the cone out and inspect
the voice coil and former. It will probably be
charred.

Your problem is the same discussed here regarding
tweeters. Interesting that some suggested that
thermal compression is not an issue in the home
listening environment:
http://techtalk.parts-express.com/sh...d.php?t=230805

[Pete Basel]

You might find this interesting:
http://techtalk.parts-express.com/sh...9&postcount=48

[Chris Roemer]

Look on the bright side. Now we have at least one data point to demonstrate that the ND-105's won't bottom before they melt. Nothing better than empirical data.

The OP stated that these were rolled off at 70Hz.
They WILL "pop" when vented hard down to 40Hz (more like a "squeal"). I've heard it several times, without any apparent damage.

Chris

[Pete Basel]

Also, 5 hours is a very long listening session and there is an effect called threshold shift. When you listen even at moderately loud listening levels your ears sort of have automatic volume control and turn it down. We tend to compensate by turning the system up. The VC temp integrates the power and tends to continuously rise when driven hard if not given a break, so 5 hours contibuted to the problem. The owner's manual for Vandersteen speakers suggests taking a break every half hour or so, even 5 minutes gives the driver some time with zero power to cool down. Still a metal former is a much better solution.

You might want to consider an MTM version of your speaker since it provides twice the thermal capacity and also 3 dB higher efficiency.

[jonpike]

Heh... Sounds like you had, instead of ferrofluid, you had "glueofluid" in your gap... Motion and heat would keep it flowing, then after cooling down and resting... it's glue again.

Interesting to know, and nicer than a loud CLANG and the sound of bent, rubbing or outright broken parts.