Sunday 22 October 2023

Repairing a Boston Acoustics Micromedia subwoofer

19:35 Posted by G No comments

 I've had my 2.1 computer speakers system for a very long time (I knew this as I bought them when I was at my old company, and I've been at my current employer for 17 years.  But when I actually disassembled the subwoofer, it has 'May 1997' on it, so that's a good 26 years service, so not unreasonable for it to have it first problem

Over the last couple of weeks there has been a nasty vibration at lower frequencies, annoyingly just in the range of some peoples voices, so when spending the day on video calls it was getting a little grating.

So first point of call was internet research. I didn't actually find anything that useful, but there was this YouTube video, which isn't very illuminating, but there were other references to speaker surrounds that had perished over time.

This is the same system as I had. So I started taking it apart (4 crosshead screws, one in each corned - you can see them recessed).  This allows you to take off the whole front of the subwoofer.  However I couldn't work out how to give myself enough room to inspect the subwoofer closely enough.  I couldn't work out how to get the front off as it the video (I still don't know how it was done in the video) .  For me the sub cable had no slack and I couldn't stretch it from the back of the enclosure.  So as it wasn't working properly and I'd had it for 26 years, I thought I'd nothing to lose by cutting the cable. I reasoned that I could always extend the cable and connect it via some sort of cable connector.

Once I'd cut the cable this is what I found :

Left hand image is the rear of the front panel, you can see the cut speaker cable and the bass port which fits into the hole above the sub. You can see from the photo on the right that the subwoofer speaker surround has perished, and therefore this was the likely cause of vibration. 

The photo above shows the problem most clearly,  you can see the near side of the speaker surround has completely perished, but the actual cone (made of paper I think) is still in good condition.

So more internet searching suggested that either Ebay or a company called North Speaker parts could sort out replacement surrounds.  I went with North Speaker parts, as they were UK based, and seemed to be a specialist.  So for the princely sum of £8 I ordered a 5" foam speaker surround replacement kit. This included glue, brush, instructions and 2 new surrounds (even though I only needed one) - kit from here. They arrived neatly packed two days later, very happy with their service.

So as per the North Speakers instructions, with the careful use of a Stanley knife, and rubbing alcohol (we used nail varnish remover) we managed [I enlisted the help of my son, hence the we] to get the majority of the old surround off.  having done that helpful teenager then applied the glue to reattach the cone to the new surround.  Allow that to bond, then an hour later he glued the cone/new surround to the brass frame.  This is more difficult as there's much less space to work with, and it took a while for the glue to actually stick to the new surround. We let this set overnight.

In the morning we checked our work, and it looked pretty promising

So while son was working on the speaker I was working on the cabling. I had spoken a while ago to our plumber and he was raving about Wago connectors. This project looked like a good opportunity to try them out, so a quick trip to ScrewFix for a pack on 100 (not sure I'll ever get through even half of these). I went for these ones - link.  To be honest their blurb says halves the time to make connections, but I found them a real pain (could easily be user error), it could also be that they are designed for solid core mains cable, in which case I can see it would be much easier.  However I had stranded cable, and it probably took me about an hour to get the 4 connections working ! (again could be user error!).

However finally we got it all together, you can see in the photo below a couple of the wago connectors and the sub back in situ.  We tested it like this and there was still some vibration, so I was a bit worried that we hadn't succeeded, however when we screwed it all together it all sounded good ! It's not perfect - when I really turn up the bass there is still a bit of vibration, but at normal levels it sounds perfectly fine. 

I'm really happy how it worked, and my £100 investment (I can't actually remember what I paid), is still going strong. Slightly weird to think I bought this setup before I met my wife, before we got married, before either of the kids arrived, and it's still going strong !

Thank you Boston Acoustics for making such good kit ! and hope this article is useful !

Finally a well earned beer after the project...

Thursday 5 October 2023

VAR shables - blaming human error is missing the point

17:42 Posted by G No comments

Definitely a systems failure !

I've been meaning to write this article for a few days, and in the time I've been thinking about it, Matthew Syed has written a piece in The Times with a very similar perspective.

He's written a book along similar lines, and that book (Black Box Thinking) references a really great book by Atul Gawande called The Checklist Manifesto, which is a fascinating read.  It talks about how the medical profession has learnt from the aviation (and space) industries about the use of checklists.

In The Times article Matthew Syed references Chesley Sullenberger the pilot who landed US Airways flight 1549 on the Hudson in the US in 2009.  What is amazing is the calmness and ability to follow a checklist to avoid any human frailties or individual errors.

What's clear in the VAR incident where the VAR team gave the wrong decision, is that there was no process or checklist to prevent an individual failure.  The PGMOL should have come out and said we had a process failure rather than an individual human failure. For a game that doesn't suffer from being underfunded, the whole implementation of VAR is poor.

As Syed says 

" Instead, given that football is the greatest game on earth and people in football obviously know more than anyone else, they decided that they would do it their own way. We may call this “football knows best syndrome”

He goes on 

"Football, let me suggest, is hubris institutionalised. Its masters assume that because the game is (to some people) a religion, they are gods. I was against VAR from the outset, by the way, fearful that it would destroy the spontaneity of a fast-flowing game but not even I could imagine how poorly it would be implemented. The Premier League, in their infinite wisdom, took no time to learn lessons from other industries, let alone other sports, about how to avoid human error in high-pressure decision-making. They thought they knew best. They were — hopelessly, comically — wrong."

I completely agree, the equivalent VAR processes in both Rugby and Cricket are much simpler, effective and transparent to the fans of their respective sports, it's seem incredible that football has managed to get this so far wrong.

The other parallel to me, is that the Premier League has got fixated on a single human error, rather than the leadership standing up and saying "we designed a poor process" which allowed a single error to escalate into a significant failing".  It reminds me of both the VW dieselgate process, where only one engineer was initially charged, and the Equifax data breach where again one engineer was blamed for not correctly scanning for a vulnerability.  In both cases, there were individual failings, but both were wider process failings.