Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Recap B&W Matrix 2 1986 issues
Recap B&W Matrix 2 1986 issues
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 11th January 2018, 09:04 PM   #1
MTH444 is offline MTH444  Belgium
diyAudio Member
 
Join Date: Jan 2018
Location: Limburg
Smile Recap B&W Matrix 2 1986 issues

In 1986 I bought a pair of B&W Matrix2 speakers and had a lot of fun with them. Until... one day they smelled like something strange was burning.
A capacitor of 100F and a resistor of 4ohm where burned on both speakers and burned the pcb locally. I brought them back to the store where I bought them, and they guy who sold them to me tried to repair them, but had not the right capacitors of 100F, so he put in the left speaker 12+85= 97F and in the right one 15+82= 97F. For the resistor he used a different value.They worked, but i felt not happy with it. Now so many years later I want to repair them properly.

- what make are the best capacitors to use? (original is ALCAP)
- must I also recap the RCL PMT/2R capacitors?
- some of the smaller resistors are oxidized, must I also replace them?

I'm new on this forum. So if somebody can answer my question would be great.
Many thancks in advance.

PS: I use a Kenwood KA1100SD to drive them. I think this amp is to powerfull for them.

Mike
  Reply With Quote
Old 11th January 2018, 11:47 PM   #2
djk is offline djk
R.I.P
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Premium Audio Grade Components | ERSE
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 12th January 2018, 12:07 AM   #3
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
B&W has become a Mundorf shop, so if you want to stick with the factory choices, I'd go with that. MKP is the least expensive, and also smallest for the overall size.

I like the Mills 12W resistors. They are great sounding, and small for the wattage. Make sure you leave plenty of space around them so they ventilate properly.

Best,

E
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.
  Reply With Quote
Old 12th January 2018, 05:23 AM   #4
MTH444 is offline MTH444  Belgium
diyAudio Member
 
Join Date: Jan 2018
Location: Limburg
must I also replace the RCL PMT/2R capacitors, or do they not age?

eriksquires: what do you mean by Mundorf shop, do they use mundorf capacitors now?

thanks for the replies
  Reply With Quote
Old 12th January 2018, 07:58 AM   #5
giralfino is offline giralfino  Italy
diyAudio Member
 
giralfino's Avatar
 
Join Date: Feb 2009
If the original cap is electrolytic (ALCAP is), buy an electrolytic, you are effectively restoring the original spec and sound. Moreover you'll find rather difficult to accommodate a film cap in a space designed for an electrolytic. Note that the repair done was probably effective because 97uF is equivalent to 100uF once you factor in the caps tolerances.

For the RCL PMT/2R caps, as they are film caps, they don't age so there isn't any reason to replace them.

I would replace also the resistor that was changed after the burn because it is not the original value, and restore the original 4R value.

Ralf

There is not a too powerful amp, in fact the opposite is true: you risk to damage a speaker more easily from an underpowered amp driven to clipping.
  Reply With Quote
Old 12th January 2018, 03:13 PM   #6
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
MTH444 - Yes. All the mid to high end B&W speakers use Mundorf film caps exclusively, but I do not know which electrolytics they use.

Erik
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.
  Reply With Quote
Old 12th January 2018, 06:56 PM   #7
giralfino is offline giralfino  Italy
diyAudio Member
 
giralfino's Avatar
 
Join Date: Feb 2009
From the photo Ive seen this is not true for the Matrix 2, that speaker hasnt any Mundorf cap. You can easily find the service manual: http://bwgroupsupport.com/downloads/...rix%202-TM.pdf

Ralf
  Reply With Quote
Old 13th January 2018, 01:17 AM   #8
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
Yeah, back in 1986 I don't know if B&W used Mundorf parts at all. They do a lot now though.

Best,

E
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.
  Reply With Quote
Old 13th January 2018, 05:10 AM   #9
eriksquires is offline eriksquires  United States
diyAudio Member
 
eriksquires's Avatar
 
Join Date: May 2013
I looked at the schematic you attached. Maybe someone else will chime in here, but those big caps aren't even needed if you are running a solid state amp.

It seems they are all part of an impedance moderating circuit, and should be safely removed completely. This is why they overheated as well. Reducing impedance means they were subject to a lot of current.

Of course, you should still check your amp outputs for evidence of DC, but I would be very much tempted to run without them. If you want to see what happens without them, I'd suggest getting DATS or Room EQ Wizard (free but need a jig) and measuring the impedance of each driver, and simulating it all in XSim. You'll better be able to tell what's going on when you look at the transfer function and the impedance charts.

Best,

E
__________________
All of my successes and failures can be explained by my attempts at getting a girlfriend. All of them.

Last edited by eriksquires; 13th January 2018 at 05:15 AM.
  Reply With Quote
Old 13th January 2018, 10:27 AM   #10
Keruskerfuerst is offline Keruskerfuerst  Germany
diyAudio Member
 
Keruskerfuerst's Avatar
 
Join Date: May 2007
Location: Germany
Strange crossover....
  Reply With Quote

Reply


Recap B&W Matrix 2 1986 issuesHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
1986 Sony CFS-280 Mini Boombox (pics) Robcrx The Lounge 7 29th September 2014 02:48 AM
NOS 1986 Mitsubishi CVX-3 Amplifier Robcrx Car Audio 0 15th March 2013 03:09 PM
Elektor Top of The Range Preamplifier 1986-7 audiophilo Elektor 3 17th December 2011 05:23 PM
scott 222 recap issues ihscoutlvr74 Tubes / Valves 7 25th January 2008 07:37 PM
Discrete Class-D anno 1986 Baldin Class D 11 26th October 2006 07:30 PM


New To Site? Need Help?

All times are GMT. The time now is 05:04 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki