udial and 4 destroyed tweeters later, what happened? (take #2)

[simon5]

Hi guys!

This is my first visit on the digital forum on DIYaudio, you can usually find me hanging around Subwoofers and Loudspeakers forums...

Sorry to annoy you guys with this today, but someone from your group recommended me to post that story here! (That's why I've written take #2 beside the subject.)

Here is the original post to put you in context, sorry for the long post :

My friend tested her brand new soundcard, a Creative X-Fi Elite Pro with udial.wav to see if that card passes the udial test. The card passed the test easily with success. Problem is, the tweeter in each Primus 150 bookshelf died. Only the tweeter in the center channel, a Primus C25 center channel, survived. She heard rattling during the test.

What happened? I'm really curious, seems impossible to me! Could someone analyze that sample to see if it's very problematic or unusual very high crest factor or something? Sorry I don't know if I can use the word crest factor in that way?

The test was done at moderate volume, -23 dB on her Pioneer amplifier which can deliver 100W per channel. According to the litterature, the Primus 150 bookshelf got a 4th order crossover (24 dB per octave) at 3.3 kHz. (Here is the specifications sheet)

http://www.infinitysystems.com/homea...es=PRI&cat=BFS

The udial test is there to test the IMD (intermodulation distortion)and poor SRC (resampling) of all Creative soundcards. Every Creative card fail the test at 44.1 kHz except the new X-Fi which got superior SRC algorithm based on a very powerful DSP (it's actually better than most SSRC (software based resampling)). The problem is only at 44.1 kHz, but that's the sampling frequency of 99% of music we listen to. (If you want to download it, please try a lower volume at first, I don't want to blow other people tweeters)

www.nitroware.net/files/udial.wav

You can see the bad IMD with IMD sweep tests, IMD is climbing with frequency. (Last graph in this link, this is for the Audigy 4 Pro, which is the less problematic card compared to previous generations)

http://www.3dss.com/reviews/Audigy4Pro/audigy4RMAA.html

Thank you very much for your help guys!

Here I include the discussion that we did on this subject :

udial and 4 destroyed tweeters later, what happened?

I asked my friend and she's 100% sure that her tweeters were perfectly OK before the test and 100% sure that her tweeters were dead after the test.

The test was run in a loop, someone made an earlier comment that 3 seconds couldn't heat up the voicecoil, so because it's in a loop, we can consider this too now.

Thank you very much guys!

[Francis_Vaughan]

Read this thread - what appears to the origin of this so-called test - and weep.

http://www.hydrogenaudio.org/forums/...ter&f=1&t=9772

The test is stupid, badly thought out, and has killed a lot more speakers than just your friends. The answers were all contained in the responses in the Loudspeaker thread you first posted on. The sound file contains a long burst of very high frequency (about 19.5 kHz) energy at a very high amplitude. Indeed it is supersonic for many people. It seems to have been designed to show whether there is substantial aliasing occurring in some resampling sounds cards or computer sound software. Sure it does that. But the idiot that designed it seems to not care that it will kill tweeters. Run in a loop this test will fry your tweeters without doubt. Most people won't hear the very high pitched tone - and bizarrely this is the sign of the system "passing" the test. Thus they are also tempted to turn the volume up further. Making it ever more likey the tweeter will fry.

If I were in the speaker repair game, and wanted to drum up extra business, this would be perfect. A nice little virus doing the rounds killing tweeters.

[simon5]

Thank you for your answer!

Not saying that her receiver is accurate, but the test was done at -23 dB which in theory is around 1W RMS for the tweeter. That's too much for a 20 kHz test?

[Jocko Homo]

In theory..........

Ah, but did you measure it any manner? No, because if you would have, you probably would never have played in through a speaker.

If you run across the guy that came up with that "test", let us know. We will help beat the stuffing out of him with you.

Jocko

[Francis_Vaughan]

One Watt is a hell of a lot of energy to dissipate for a tweeter. I think part of the problem is that we are not good at having a feeling for what these numbers mean. So, perhaps some other thought experiments.

Would you be prepared to connect a 2.8V battery directly to your 8 Ohm tweeter?

Pull out your parts bin, find a 1 Watt resistor. Contemplate its size and design. It is made of ceramic and metal. Your tweeter is made of metal and glue. The glue is of course the problem.

Another thing you might like to do - use a sound editing tool to create a 1kHz signal - now play that at the same level as the original test tone. Loud isn't it? Now remember that your tweeter is being hit the with the same energy, but is being asked to dissipate the heat in a vastly smaller package - and one with essentially no heat rejection capacity.

[simon5]

I guess that's why ferrofluid has been invented hehe!