Melted NeoPro5i

[ultrachrome]

I could light money on fire but that's not nearly as painful.

Not sure what happened but it involved attempting to measure FR with a wallin jig and my desktop computer's built-in sound card. This test worked fine with my laptop.

Picture provided for your enjoyment and my therapy.

Low res attached. High res (1.6MB) here

[DIY_newbie]

Brian,

Sorry to here that bro... Looks like you sent too much low frequency energy to the ribbon. Was there a pop? The ribbon looks like it twisted and ripped?

I know how you're feeling right now, the good news is it costs around $28 to fix it at madisound Maybe this will make you feel better:

JP2.0 Project Part IV : How to blow up a ribbon and scare the life out of your cat

Anyway welcome to the broken ribbon club

--Chris

[ultrachrome]

Thanks. Great to be here.

Actually I had just done a FR test with this new computer but then realized that I did not have the wallin jig between the amp and the speaker. So I fixed that and as soon as I powered up the amp, the amp's fabulous "instantaneous distortion" LEDs illuminated and I quickly turned it off.

Unlike my previous test rig where I could hear the tweeter hiss (high eff. + noisy sound card) there was no sound save for a barely perceptible high-freq whine accompanied by a melting plastic smell.

When I regained conciousness, I noticed the distorted ribbon. I should note that the ribbon normally has a slight crease down the middle. The bottom of the ribbon looks normal. The top is a little distorted and pulling slightly away from the magnets.

This ribbon is $45 and I hope only the ribbon was damaged.

Actually, it seems to sound okay and impedance and nearfield FR measurements (the latter without the jig) look fine as well. I guess I would need to do distortion tests to see what the damage really is.

edit: I've had a 15uF cap on the ribbon for all FR tests.

[DIY_newbie]

Yeah, I have a 20uf cap inline with my tweeter at all times, with the efficiency of these ribbons even a few mV of DC offset can really cause trouble.. My guess is your soundcard had just a bit of DC offset and it pushed the ribbon constantly outward causing it to tear/streatch.

I wouldn't be too concerned about destroying more than the ribbon, I managed to send a 250 Watt impulse function to mine which caused an arc between the magnet and the actual ribbon. The discharge deposted metal from the ribbon onto the magnet (basically mini arc-welding) and the transformer was 100% fine

Now that you're a member of the club we have to get the moderators to give you access to the super-secret "Ribbon Killaz" forum where we laugh at all the puny dome tweeters

--Chris

[Audiophilenoob]

if the neo didn't use that composite material I would send you some replacement foil

one advantage to DIYing ribbons

[thylantyr]

fyi;

pure ribbons are cool drivers but not as robust as magnetic
planars like PT2. I'd rather have a NeoPro5i over PT2 but
to give you an example of how robust the PT2's are.

re: The NSB/PT2 line array, I turn on the system out of
sequence and hear those DCX pops. No problems.

One day I was hooking up my Roland M1000 and I was
toggling the front panel button to change 'modes' and the
system was crackling when changing songs as if it was trying
to sync, that nasty crackling seemed 100x stronger than
those little DCX turn on pops, yet the PT2's survived.

At high SPL, I clip my amps. No problem. To add more comedy
to this story, each PT2 has it's own AGC 1A fuse -just in case-
and I haven't blown a fuse in months torturing the line array.

This weekend an old friend came over and he was listening
to the system and before he left, we played one Slayer song
at hellish SPL levels and I forced heavy clipping on purpose
to punish him. We had fun doing this, shortly all the tweeters
were not playing. /doh

I checked the system and found the 1A fuses were blown,
all of them. Cool, the fuses did their job. I replced the fuses
and the system is fully operational again.

I don't have capacitors between the amp and tweeters either,
I never use them ever. Since I've been doing audio (early 80's},
the fuse has always saved me in spite of what people tell me
that they are no good, they don't respond fast enough, they
color the sound, etc. Guess what? I can't remember the last
time I blew a tweeter and I've never heard any bad sonics
associated with an inline fuse. Am I lucky or is there a method
to my madness ?

Anyway welcome to the broken ribbon club
I mentioned to use a fuse in the last ribbon blowing fiasco.
There is no guarantee that the fuse will help if you twisted the
foil with a low frequency signal, but at least it will help when
you exceed power handling.

20 PT2's in the array. Cost to replace 20 fuses? $4.00
If not fused, cost to replace 20 PT2's would be = $500

[ultrachrome]

Yeah, I think I remember that you mentioned that. I simply elected never to turn my DCX off.

I can't be pushing more than a couple watts through these at most. 5 watts @ 7 ohms would be .85 amps if my math is correct. And a half amp fuse would die after 1.75 watts?

Btw, while not much into metal anymore, I have a secret love of Slayer's Decade of Decadence. I love how warts-and-all it sounds. To me, it sounds closer to being there than other live recordings I've heard (bootlegs not included).

[ultrachrome]

Originally posted by DIY_newbie
Yeah, I have a 20uf cap inline with my tweeter at all times, with the efficiency of these ribbons even a few mV of DC offset can really cause trouble.. My guess is your soundcard had just a bit of DC offset and it pushed the ribbon constantly outward causing it to tear/streatch.
--Chris

I noticed when I was setting volume levels in SW with line in connected to line out that the + and - swings of the sine wave where not equal. For example if the the positive side hit 8k, the negative side was maybe 7k.

Didn't have this issue with my laptop rig.

[DIY_newbie]

Sounds like your soundcard has some DC offset, but if you had a 15uf Cap it should have blocked the DC...

Thy : The fuses are a good idea if you're worried about spikes and high energy inpulses like the ones that killed my tweeter, but I don't think the fuse will do nothing to block DC offset from an amplifier or source.. If you really want to be safe, you should probably have both...

--Chris

[thylantyr]

Originally posted by DIY_newbie
Sounds like your soundcard has some DC offset, but if you had a 15uf Cap it should have blocked the DC...

Thy : The fuses are a good idea if you're worried about spikes and high energy inpulses like the ones that killed my tweeter, but I don't think the fuse will do nothing to block DC offset from an amplifier or source.. If you really want to be safe, you should probably have both...

--Chris

I believe those ribbon tweeters have isolation transformers
for impedance matching. DC voltage at the amplifier terminals
won't pass to the tweeter because isolation transformers don't
pass DC voltage. /bonus

If your amplifier has abnormal DC offest, lets say 0.1V or greater,
then your amplifier is either a.) broken b.) bad design c.) not
proper for the application, but if the ribbon has the transformer,
doesn't matter. {ie, the transformer is built into the speaker}.

This is easy to test. Measure the DC voltage across the
ribbon element after you turn on the amp. What does it say?
{don't measure at the speaker terminals because it's before
the transformer, not after}.

Now that the tweeter is toast, you might as well explore this.