How much DC offset does it take to kill a speaker? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 18th June 2009, 11:57 AM   #1
wwenze is offline wwenze  Singapore
diyAudio Member
 
Join Date: Mar 2008
Default How much DC offset does it take to kill a speaker?

Apparently my speakers survived 300mV (!) worth of it. The other channel had around 90mV. This is coming from a cheap small Chinese ebay amp that hums like crazy.

So I was calculating, at 0.3V, the heating power would be, assuming 6 ohms for DC current, 0.015W, which appears to be able to generate less temperature difference than living in the tropics, which I do.

Do we need to be paranoid about speakers frying from such (huge?) amount of offset?
  Reply With Quote
Old 18th June 2009, 12:17 PM   #2
Dr_EM is offline Dr_EM  United Kingdom
diyAudio Member
 
Dr_EM's Avatar
 
Join Date: Oct 2006
Location: Swindon
I think it's more indicative of a flaw in the amplifier at these sort of levels than of actual concern for the drivers.

It may damage the transformer of a direct coupled ribbon tweeter, but you should never do this anyhow. The offset could also degrade sound quality I suspect.
  Reply With Quote
Old 18th June 2009, 12:22 PM   #3
RIP
 
Join Date: Oct 2005
Location: Central Florida
You'll get lots of opinions about how much offset is acceptable, but if you have 300mv there is something wrong with the amp.
Generally, most DC protection circuits dont kick in until the DC gets above 1V, and your math is correct.

Best, Bill
  Reply With Quote
Old 18th June 2009, 12:29 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
how far does the driver offset from the zero position when you connect 300mV of offset to it?
__________________
regards Andrew T.
  Reply With Quote
Old 18th June 2009, 01:00 PM   #5
diyAudio Member
 
Join Date: Sep 2008
Had a DCX2496 leave 1V DC on one of its outputs(it was faulty) into a Zapsolute mk2. It's DC servo probably saved things but even that ran out of range.
Peerless HDS164 (850438) got HOT!
I first detected a smell out of the BR port and turned things off quickly. It was on for a minute or so, maybe two.
The phaseplug was nearly untouchable and the cage was nearly as hot.
The driver works fine and I can not detect any differences or bad sound compared to the non heated one.
So it depends on the driver. The thermal design is important and they certainly held up in that department.

Personally, anything above 50mV is a no no. Prefer it to be under 20mV.
More due to principle than damage potential.
  Reply With Quote
Old 18th June 2009, 01:17 PM   #6
RIP
 
Join Date: Oct 2005
Location: Central Florida
Quote:
Originally posted by David_Web
Had a DCX2496 leave 1V DC on one of its outputs(it was faulty) into a Zapsolute mk2. It's DC servo probably saved things but even that ran out of range.
Peerless HDS164 (850438) got HOT!
I first detected a smell out of the BR port and turned things off quickly. It was on for a minute or so, maybe two.
The phaseplug was nearly untouchable and the cage was nearly as hot.
The driver works fine and I can not detect any differences or bad sound compared to the non heated one.
So it depends on the driver. The thermal design is important and they certainly held up in that department.

Personally, anything above 50mV is a no no. Prefer it to be under 20mV.
More due to principle than damage potential.
You had a hell of a lot more than 1V DC across your speaker!

Bill
  Reply With Quote
Old 18th June 2009, 01:45 PM   #7
diyAudio Member
 
StigErik's Avatar
 
Join Date: Feb 2008
.
__________________
dipoles dipoles dipoles dipoles dipoles dipoles dipoles dipoles and dipoles
  Reply With Quote
Old 18th June 2009, 01:52 PM   #8
diyAudio Member
 
Join Date: Sep 2008
I sure did.
No way of knowing how much as I don't know the gain of the amp nor how much the DC servo managed to correct before 'clipping'.

I was afraid I had burned both amp and speaker. But they are fine.
I guess this is why we pay for quality.
  Reply With Quote
Old 18th June 2009, 02:08 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by David_Web
No way of knowing how much as I don't know the gain of the amp nor how much the DC servo managed to correct before 'clipping'.
Hi,
if a DC coupled amplifier is a "must", then one "must" consider DC detect and speaker isolation. A DC servo is NOT ENOUGH.
__________________
regards Andrew T.
  Reply With Quote
Old 14th October 2011, 02:13 PM   #10
diyAudio Member
 
Join Date: Jan 2004
Location: Honduras Central America
Send a message via MSN to opacheco Send a message via Yahoo to opacheco
Default Loudspeaker and DC Offset

Hi,

I readed some very short about this here:

B&C SPEAKERS

But I would like to find something more specific(theorical analysis I mean!) for that....Do somebody know where I can find something like that???

Thanks
Opacheco.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What is acceptable DC offset on speaker terminals? valterdaw Car Audio 3 3rd December 2007 09:01 PM
Speaker output with offset.. unknow81 Solid State 7 26th October 2007 03:05 PM
Did I kill my B+Ws allquiet Multi-Way 8 29th May 2007 08:16 PM
Can a bad cap kill an LM3875? SRMC Chip Amps 5 18th April 2003 02:41 PM
Over kill? Scribble Pass Labs 1 21st January 2003 07:27 PM


New To Site? Need Help?

All times are GMT. The time now is 11:00 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2