Driver on the blink?

Martin Prothero · 10th May 2010, 07:35 PM

I may be being paranoid but I can notice on some tracks that my left driver is distorting at certain frequencies.

Fostex (FE168EZ) bought about 3 years ago. Has had lots of use but never abused. How long is the life expectancy for these?

It may be an amp issue. I have just finished a gainclone (stereo LM3875). I have swapped over the speaker cables at the amp end and it seemed that the right driver was not showing the same symptoms.

The sound is a grainy slightly fuzzy sound, just audible in some music (like cleanly recorded sax or clarinet). I thought it was just the sound of the reed at first but with my head really close I can defo hear something odd going on...

Any thoughts? Could it be DC on the left amp channel?

Cal Weldon · 10th May 2010, 07:42 PM

Try another speaker to see if it's the amp. If it is the Fostex, try removing and turning it over. It may be a rubbing coil and this may fix it.

planet10 · 10th May 2010, 07:45 PM

I would at least take a precautionary look for DC. I'd also check to see if some damping material has come in contact with the cone.

dave

Martin Prothero · 10th May 2010, 08:01 PM

Thanks guys. I'll have it out tomorrow and look for any of the above signs.

I measure DC at the speaker posts right, or will it need to be at some other part of the amp output?

Glowbug · 10th May 2010, 08:03 PM

Yep, at the outputs.

Martin Prothero · 10th May 2010, 09:23 PM

Erm
Be gentle on me...but I seem to be getting some odd readings so I am obviously not understanding this right.
I have set up my DMM with crock clips on the outputs of L speaker posts and have music running through it. I wanted to measure at 0 and full volume but the readings are fluctuating with the music.
Do I need to find a sine wave and use that? Maybe my DMM isn't set to the correct reading. (I can't find the instructions and I last read it about 3 years ago!)
Can someone be nice and treat me like a school kid and tell me what I need to do and which symbol to put the meter on.
eerm, please:-)

godfrey · 10th May 2010, 09:29 PM

Check for DC with the amp on, but no signal. e.g. volume all the way down.

Martin Prothero · 10th May 2010, 09:40 PM

OK.
I put the black probe (in COM on meter) onto the ground post and the red on the positive. The symbol on the meter is the V with a line and a dotted line (not the wavy one) and the measurements were
L channel: -02.4mV at zero and -46.2mV at full volume
R channel: 11.1mV at zero and -36.0mV at full

Does that make any sense to anyone or am I just slipping into a coma?

Martin Prothero · 10:36 AM

Well, I think it was a mounting issue. Took out the driver to inspect. Nothing unusual to be seen but when I tried again having put it back in the original problem seems to have gone. Screws were all tight, so I don't have a clue!

Fingers crossed it was just a blip and will never come back.

kipman725 · 11th May 2010, 12:06 PM

probobly the early mentioned rubbing voice coil and by moving the driver you reset it to the correct position. I had a driver do this seemingly randomly and unfortunatly it was unfixable, although it was 15 years old.

10th May 2010, 07:35 PM	#1
Martin Prothero diyAudio Member Join Date: Jan 2007 Location: Devon, UK	Driver on the blink? I may be being paranoid but I can notice on some tracks that my left driver is distorting at certain frequencies. Fostex (FE168EZ) bought about 3 years ago. Has had lots of use but never abused. How long is the life expectancy for these? It may be an amp issue. I have just finished a gainclone (stereo LM3875). I have swapped over the speaker cables at the amp end and it seemed that the right driver was not showing the same symptoms. The sound is a grainy slightly fuzzy sound, just audible in some music (like cleanly recorded sax or clarinet). I thought it was just the sound of the reed at first but with my head really close I can defo hear something odd going on... Any thoughts? Could it be DC on the left amp channel? __________________ Keep a green bough in your heart, the singing bird will come.

10th May 2010, 07:42 PM	#2
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Try another speaker to see if it's the amp. If it is the Fostex, try removing and turning it over. It may be a rubbing coil and this may fix it. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

10th May 2010, 07:45 PM	#3
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	I would at least take a precautionary look for DC. I'd also check to see if some damping material has come in contact with the cone. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

10th May 2010, 08:01 PM	#4
Martin Prothero diyAudio Member Join Date: Jan 2007 Location: Devon, UK	Thanks guys. I'll have it out tomorrow and look for any of the above signs. I measure DC at the speaker posts right, or will it need to be at some other part of the amp output? __________________ Keep a green bough in your heart, the singing bird will come.

10th May 2010, 08:03 PM	#5
Glowbug diyAudio Member Join Date: Feb 2006 Location: Hillsborough, NC/McLean, VA	Yep, at the outputs. __________________ Jim J.


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10th May 2010, 09:23 PM	#6
Martin Prothero diyAudio Member Join Date: Jan 2007 Location: Devon, UK	Erm Be gentle on me...but I seem to be getting some odd readings so I am obviously not understanding this right. I have set up my DMM with crock clips on the outputs of L speaker posts and have music running through it. I wanted to measure at 0 and full volume but the readings are fluctuating with the music. Do I need to find a sine wave and use that? Maybe my DMM isn't set to the correct reading. (I can't find the instructions and I last read it about 3 years ago!) Can someone be nice and treat me like a school kid and tell me what I need to do and which symbol to put the meter on. eerm, please:-) __________________ Keep a green bough in your heart, the singing bird will come.

10th May 2010, 09:29 PM	#7
godfrey diyAudio Member Join Date: Nov 2009 Location: Cape Town	Check for DC with the amp on, but no signal. e.g. volume all the way down.

10th May 2010, 09:40 PM	#8
Martin Prothero diyAudio Member Join Date: Jan 2007 Location: Devon, UK	OK. I put the black probe (in COM on meter) onto the ground post and the red on the positive. The symbol on the meter is the V with a line and a dotted line (not the wavy one) and the measurements were L channel: -02.4mV at zero and -46.2mV at full volume R channel: 11.1mV at zero and -36.0mV at full Does that make any sense to anyone or am I just slipping into a coma? __________________ Keep a green bough in your heart, the singing bird will come.

11th May 2010, 10:35 AM	#9
Martin Prothero diyAudio Member Join Date: Jan 2007 Location: Devon, UK	Well, I think it was a mounting issue. Took out the driver to inspect. Nothing unusual to be seen but when I tried again having put it back in the original problem seems to have gone. Screws were all tight, so I don't have a clue! Fingers crossed it was just a blip and will never come back. __________________ Keep a green bough in your heart, the singing bird will come. Last edited by Martin Prothero; 11th May 2010 at 10:36 AM. Reason: mispellignz

11th May 2010, 12:06 PM	#10
kipman725 diyAudio Member Join Date: Jun 2007 Location: London/N.lincs	probobly the early mentioned rubbing voice coil and by moving the driver you reset it to the correct position. I had a driver do this seemingly randomly and unfortunatly it was unfixable, although it was 15 years old.

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