Tweeter No Sound - 0 ohms across terminals - 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 2nd July 2014, 07:36 PM   #1
Ramie is offline Ramie  United States
diyAudio Member
 
Join Date: Jul 2014
Default Tweeter No Sound - 0 ohms across terminals

Hello folks,

Just re-foamed Cerwin Vega R12's (1977 two-way loudspeaker) after many years of storage and one tweeter wasn't working. No hiss or crackle like it was blown, just zero sound.

Pulled both tweeters and swapped them into opposite cab's and the bad tweeter doesn't work in either cab, while the good tweeter works in both, so it's in the tweeter itself.

Got out DMM and tested across terminal leads on the good tweeter and got 8 ohms and it is indeed an 8 ohms tweeter. (Surprised it read 8 ohms as I read an 8 ohm tweeter reads closer to 5, but whatever... I got 8 full ohms from it.) Tested the bad tweeter and got no reading (0 ohms).

Read 0 ohms means either a "dead short" or "open voice coil" ... and wondering where I can go from here. I know nothing of electronics so please respond as if I am in training. Is this tweeter just no good anymore? Can I try something to unstick the voice coil, if that's it... or open it and look for an obvious soldering break? Thanks!
  Reply With Quote
Old 2nd July 2014, 11:07 PM   #2
diyAudio Member
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
Purchase a new pair of tweeters as one will odd make not ballance otherwise. The voice coil has been cooked. Nothing to be done, sorry.
__________________
www.flyingmole.co.uk For World Wide support for Flying Mole, Class D, Refurbishment and Repairs. www.jonsnell.co.uk
  Reply With Quote
Old 2nd July 2014, 11:16 PM   #3
Ramie is offline Ramie  United States
diyAudio Member
 
Join Date: Jul 2014
Thanks, appreciate your help.
  Reply With Quote
Old 3rd July 2014, 01:53 AM   #4
diyAudio Member
 
Lynn Olson's Avatar
 
Join Date: Jul 2004
Location: Northern Colorado
A reading of "0" ohms means a dead short. Not repairable unless the driver has field-replaceable voice coils. Otherwise, both tweeters need replacing so channel-to-channel symmetry is maintained.
  Reply With Quote
Old 3rd July 2014, 02:58 AM   #5
diyAudio Member
 
Join Date: Jan 2011
Location: Willamette Valley
So the only place a dead short, 0 ohms, can occur is in the voice coil itself. The varnish on the wire has burned out and you can only fix the problem with new wire. An open circuit might be repairable. Sorry.
  Reply With Quote
Old 3rd July 2014, 03:09 AM   #6
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

A dead short is very unusual failure mode for a tweeter,
as it requires epic meltdown without it going open, and
AFAIK that simply never happens, I've never seen it or
heard of it in over 40 years of being involved in audio.

0 ohms does not mean an "open voice coil" that would
measure very high ohms, not a short. If a tweeter
measures 0 ohms I'd immediately look for a wiring
fault / failure as the only likely possible cause.

rgds, sreten.


FWIW read up on the "Econowave", that is the best
way to go with nice cabinets with a 12" bass/mid.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 3rd July 2014 at 03:15 AM.
  Reply With Quote
Old 3rd July 2014, 03:30 AM   #7
diyAudio Member
 
Join Date: Jan 2011
Location: Willamette Valley
You are correct, Sreten. An open circuit does not measure 0 ohms. Now tell us how a short circuit would measure.
  Reply With Quote
Old 3rd July 2014, 03:36 AM   #8
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Quote:
Originally Posted by phivates View Post
You are correct, Sreten. An open circuit does not measure
0 ohms. Now tell us how a short circuit would measure.
Hi,

The bleeding obvious, already stated, what is your point ?

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 3rd July 2014 at 03:43 AM.
  Reply With Quote
Old 3rd July 2014, 08:28 PM   #9
Ramie is offline Ramie  United States
diyAudio Member
 
Join Date: Jul 2014
First, thanks to everyone for your feedback. I greatly appreciate it.

Quote:
Originally Posted by sreten View Post
Hi,

A dead short is very unusual failure mode for a tweeter,
as it requires epic meltdown without it going open, and
AFAIK that simply never happens, I've never seen it or
heard of it in over 40 years of being involved in audio.

0 ohms does not mean an "open voice coil" that would
measure very high ohms, not a short. If a tweeter
measures 0 ohms I'd immediately look for a wiring
fault / failure as the only likely possible cause.
Again please excuse my ignorance, but I assume you mean a fault with the wiring on the tweeter itself, since the good tweeter worked in both cab's, and the bad tweeter is getting no reading on the DMM. (Just dbl-checking because I am so out of my element here.)

Like phivates mentioned, I noticed the varnish over the wire on the bad tweeter was 'a thin, skinny trail' and not as thick as the bead covering the wire on the good tweeter. I can't see an actual break in the varnish or wire anywhere. There was a spec of green corrosion (could only spot it with a magnifying glass) on one side of the voice coil at the base where the wire was running. I used a dental tool and toothbrush to clean it up gingerly, careful not to dig into the varnish or fine wire but it's so very thin (and already obviously broken somewhere) who knows if I made it worse. I would think there cannot be corrosion on varnish so the wire must be exposed there. <?> I did clean it up and could not see a break there or anywhere else, but I might need a microscope. I re-tested but still 0-ohms.

Quote:
FWIW read up on the "Econowave", that is the best
way to go with nice cabinets with a 12" bass/mid.
Hey thanks. I might need that. FTR these CV R12s are only 2-way loud speakers with a 12" woofer and 5-inch round, Dhorm tweeter (DH-10) with a 1-inch VC, 1.5 lb magnet, 2000 Hz xover, and 17,000 gauss... I didn't know what a Dhorm tweeter was (and am still not clear after reading about it). I will look at Econowave but I couldn't find anything to replace them the other night when looking.

However I did luck out... I found an original DH-10 pulled from an R12 just like mine on eBay.. so same exact tweeter meaning I would not have to replace both. He was asking $38 (incl shpg) but I offered $30 and he accepted. So it's on its way.

Meanwhile I AM going to continue to play with the one that isn't working as it looks perfect and I'd really like to find the problem. Even if I can't fix it, I'd just like to know where it failed. My guess is where that corrosion appeared.... maybe I need a better mag glass. Or younger eyes.

Also, these speakers were paired with a Technics SA-404 (50w) purchased at the same time in 1977, and I never abused the speakers. But they did sit in storage in a garage for the last 16 yrs or so. And here in So Cali the garage can get hot in summer. ?
  Reply With Quote
Old 3rd July 2014, 10:58 PM   #10
diyAudio Member
 
Join Date: Jan 2011
Location: Willamette Valley
Dhorm is oldspeak for waveguide. Dome plus horn, not as deep as the usual horns of the day. Glad you found an exact replacement, though Sreten's suggestion will outperform the original by a wide margin.
  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
Changing ohms values for mid and tweeter Ccdave Multi-Way 5 19th November 2011 09:03 AM
8 ohms woofer plus 4 ohms tweeter? stf92 Multi-Way 9 27th August 2011 07:07 AM
Crossover for 4ohm Tweeter and (2) 8 Ohms Woofers rmjeeves Multi-Way 15 1st May 2011 01:47 PM
15 ohms (12 on ohmmeter) with 24 ohms resistor in parallel to bring to 8 ohms McIntosh Man Multi-Way 29 11th June 2010 05:36 PM
Ohms wiring question: How does the tweeter fit in? Emprov Multi-Way 8 23rd May 2005 07:20 PM


New To Site? Need Help?

All times are GMT. The time now is 04:02 PM.


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