Biggerbyfar's Weblog

White Box Sound System – Critical Mass London October 2009

BBF — Thu, 19 Nov 2009 00:58:56 +0000

White box sound system – it’s not blessed in the looks the department, but in terms of sound quality and volume for the cost, weight and size it ain’t too shabby.

4x Infinity coax speakers in foamboard construction. Show with 12v SLA battery (5Ah 12v) connected via Anderson Powerpole connector and inline blade fuse (10A)

Critical Mass London hit the streets on 30th October 2009, with about 4 sound systems including this one. There was the big “Pedals” or “Son of Pedals” rig, another smaller trailer system, and a another which looked like some domestic house speakers hanging from a front rack. There may have been others but I would easily miss them as I’m generally trying to avoid other systems and the resulting sound-clash.

Playlist

We opted for the easy life this time and stuck near the front during the ride. Blasting off with General Midi’s ”Audio Assault” seemed to go down well soon after departure, riding along York Road towards Westminster Bridge. Tunes came via the excellent Spotify application for iPhone, the only snag was that there is no EQ function within the application. Normally I’d reduce the bass to prevent distortion at the highest volue – like when playing from the normal ipod function, but this just wasn’t possible. The approximate play list from that evening is also available.

Box Modifications

As mention in a previous post, I upgraded the amp from a 41hz.com 2x 25w “Amp6” to a 4x50w “Amp9” kit, which really added some oompf. Only problem was that the existing heatsink wasn’t enough so I carried out two modifications at once. First was to trim the back ‘corner’ (furthest from the speakers), this was necessary as the box was slightly too long and it would dig into the back of the bike saddle.

New heat sink

Secondly was to change the heat sink to something built for the purpose. This was fairly straightforward as (as before) the heat sink was pushed through the side wall with the amp simply bolted to the flat piece on the other side. In effect it’s not attached to the box, just trapped from both sides. With the new heat sink, the amp no longer overheats, and runs very very cool indeed. Going full tilt there is a bit of bass distortion, but I’m not sure if that’s supply voltage clipping or the speakers themselves.

Possible changes

I might run at 24v instead of 12v to give more “headroom” to the amp. I’m fairly sure that amp itself may clip due to not being able to exceed the input voltage on it’s outputs, rather than from an internal power limitation. If correct, this would stop some bass distortion at high volumes. One way to test this would be to rig it up to an oscilloscope and track the input DC voltage – measured at the amp input terminals (to see potential voltage drop at high current), along with the signal-input and power-output waveforms. If the output waveform stays largely the same as the input signal waveform (especially at the peaks), then any distortion if heard will be coming from within the speaker drivers themselves. If the output waveform gets clipped-off at the peaks, it’s a supply voltage issue or, less likely, a power limitation in the amp.

Happy massing.

Inspiron 510m doesn’t support hard drives bigger than 137Gb

BBF — Sat, 08 Nov 2008 12:28:00 +0000

Ahhhh….. what a frigging pain the arse. My old hard drive started making that clicking noise that hard drives make when they’re about to die. I ordered a 250Gb Western Digital Scorpio WD2500BEVE after checking all over the entire interweb and found no conclusive information…. I took this as evidence that the problem whereby drives larger than 137Gb cannot be read correctly, wasn’t an issue for the 510m. I didn’t actually *need* a big drive, I just wanted a fast drive, and speed and capacity go hand-in-hand in the realm of laptop hard drives. This Western Digital drive was the biggest / fastest I could find with an IDE or ATA interface (also called PATA since the introduction of SATA drives…).

I found a dell forum post where someone mentioned that the era of Pentium-M processors (as fitted in this laptop) was about the same time that 48bit LBA was introduced on motherboards and chipsets. So that, combined with the lack of any posts by people actually complaining about their 510m not ‘seeing’ the full capacity of newly installed big drive, led me to think it wouldn’t be an issue.

Wrong.

Just tried it – drive lists as “137Gb”. Boooo. Now I have to felch around with some weird tools supplied by WD that hopefully will make this all work.

Update #1: Boo, fail, disaster. XP just fails to run setup. It hangs at the ‘starting windows’ phase. This just isn’t gonna work.

Update #2: There is so much conflicting information about this on the internet it’s just not funny. Western Digital have a free ‘lifeguard tools’ software download. The windows version (there is also a bootable CD/dos version) seems to have a one-track mind towards formatting and copying your current system drive on the new WD drive. None of the options in the windows based version of ‘lifetools’ seemed to do the trick. This got to the point where I ordered another 120gb drive and put all this nonsence behind me. I then tried the Dos/CD version of WD’s lifeguard software which does do the trick! Yes! Unlike many reports of bios limitations being an absolute barrier to using drives larger than 137Gb in older systems, the ‘dynamic drive overlay’ solution does indeed work. After installing this software into the boot area of the WD drive, all my woes have dissapapeared. The bootable XP w/sp2 CD setup routine works as normal, I could select the whole drive as a C: drive and everything works as expected. Sorted! World peace is restored.

Foam board speakers : summary

BBF — Fri, 07 Nov 2008 10:32:00 +0000

The system summary.
Four infinity 5002i 13cm full range coax speakers
Micro 4x50w “Amp9-basic” 12-24v class-D amplifier (actually a variation by Tripath which they call class “T”) supplied by 41hz.com
Two sheets of 10mm thick foam-board
One ‘Haze’ branded 5Ah 12v battery (a small sealed lead acid, cheap and only weighs just over 1Kg).

Future mods: fix the heatsink. Add a seperate sub.

The heatsink isn’t a problem, but the added faff of a crossover and sub is making that change look unlikely.

There are some interesting resources on the internet but they are not the easiest ones to find :-
http://www.lautsprechershop.de/english/index_hifi.htm (some really bizzare drivers in there)
http://www.digikey.com/ (massive range of accelerometers)

The only reason I’m interested in accelerometers was so that I could contemplate using my currently un-used 8″ JL Audio sub as a servo-feedback device. I had previously used this same driver successfully in this configuration but using one of the two voice coils as a pickup coil. While this did work with some fairly primitive op-amp ciruitry, is was hideously inefficient using only one coil to power the device with. So to get around this, the idea is that you stick an accelerometer directly to the cone and use that to provide feedback on where the cone actually is, and modify your drive signal accordingly. You can then get ruler-flat response and viciously punchy sound, I guess you could even forget about tuning your box for that purpose too.

Bicycle soundsystem foamboard speakers Part 3

BBF — Thu, 06 Nov 2008 13:47:00 +0000

It was bound to happen. The desire for more power is almost a foregone conclusion. Two failed attempts with the more powerfull kit from 41hz.com – the “Amp-9″ had not been successful, and while the current amp, the 2x25w “Amp-6″ was working fine, it sometimes lacked a bit of oomph, and a bit of gain. I gave this one more shot, but in the form of the AMP-9 “Basic” which is somewhat simplified, and bit smaller. This more muscular amp knocks-out a whopping 4x50w rms when running from 24v. Although that figure is quoted at slightly-high distortion criteria, it is an impressive feat, all coming from a single IC chip.

Some aspects of soldering the kit are surprisingly difficult, but the amp worked first time and once hooked-up to the existing box, did offer a bit more welly in the low end. That bass ‘pop’ became a bit more of a thump again, without any crunching of distortion. The new configuration was definitely more power-hungry with a standby current of about 200mA, and running warmer too. The improved ‘white-box soundsytem’ took it’s first outing to Critical Mass on September 2008, it ran pretty well, although the heatsink wasn’t big enough. This resulted in the small aluminium plate becoming very hot – too hot to touch. Because of this, I had to keep shutting it down for a few minutes to cool. Very annoying.

Bicycle sound-system foamboard speakers Part 2 : Audio amp steroids…

BBF — Sun, 02 Nov 2008 23:12:00 +0000

Shoving four car speakers in a lightweight box sort of solves the portability issue in terms of size and weight, but this thing still needs a power supply and some amplification. My initial thoughts were that car amplifiers were out due to being power-hungry, heavy, lie through their teeth about every spec, and over-priced too. That said, I did find a few references to a discontinued blaupunkt low-ish power Class-D amp. I couldn’t find any stockists of the particular model but it did seem idea – I think it was 2x50w rms, 12v and class-D design which makes it as efficient as you can generally hope for ( usually 80%+ efficient).

I found a solution in the form of a 41hz.com audio amplifiers. After a couple of failed attempts at two Amp-9 kit (first one DOA, second one died after 10mins use), the winning formula was the “amp-6 basic”. This tiny kit was still quite tricky to solder with it’s surface mount components and heat-wicking heavy copper traces, but worked first time. It is almost perfect for the job :

~12 volts
Very very low standby current – less than 50mA I think.
Very small – smaller that a mobile phone.
Stereo
Uses 4 channels to give 2 briged outputs

This thing was amazing. Absolutely tiny, barely got warm even when running flat-out, so little heat in fact that it ran fine just hanging of a small piece of aluminium sheet (10 x 15cm) folded through 90 degrees and punched through the foam-board wall of the box. The amp just hung off the interal piece by the chip. The only problem with this was a a bit of gain. My crappy Sansa E250 mp3 player didn’t seem to have very high signal output, even on max. A borrowed ipod nano gave a much stronger output.

With the Sansa running between 90-100% volume most of the time, this mobile contraption first hit the streets during Critical Mass in 2007, I can’t remember which month, but I think I might have been the only sound system present. First time out I took two batteries, expecting to need to change during the night. I obtained two very basic 12v 5Ah sealed lead-acid batteries for only £7.65 each from the excellent Rapid Electronics, a hell of a lot cheaper than that ‘electronics store’ crap-house of all that is shite (you know the one) that is more commonly found on the high street.

I have never ever had to change the battery. Ever. So I still don’t actually know how long it lasts for, but it’s definitely over three hours running flat out. When I say flat out, I think literally everything is running flat out – the amp is just under clipping point, the speakers are about at their limit before the bass ruins everything else and it gets painfully loud if you get too near. Running from a lab PSU with moving-coil volt/ammeter shows that running flat out pulls about 4amp peaks, but the average is probably more like 1-1.25amp, so I guess this fits with the apparent run-time from a 5.7Ah battery – 5.7 divided by about 1.25 is 4-5 hours, although the 5Ah figure is usually quoted at a 10-hour rate, getting worse the higher the current. But it all seems to add up about right. It certainly doesn’t need to run any longer than three hours.

Bicycle sound-system foamboard speakers Part1.

BBF — Sun, 28 Sep 2008 12:41:00 +0000

The criteria:

To have some party tunes on-the-move at London’s “Critical Mass”
LOUD
Not sound crap
Not be heavy
Cheap!

OK, first things first – this is a retrospective posting catching up with all that’s happened in the last few months/years. This has
already been built but I have the feeling that it should be passed-on. Why? Because almost every question that arose while constructing this ‘beast’ was not (is still hasn’t) been answered online. “What questions?” you ask – well… let me divulge… Warning – this post gets mildly technical, because I’m that way inclined.

I wanted to bolster the communal atmosphere at London’s awesome critical mass rides. Why? Because it’s a great affair, and one that feeds on collective contribution. If you consider that the British psyche might be considered quite ‘reserved’, then it surely gives even more weight to the idea that on the last Friday of every month, typically 500+ cyclists gather at Southbank (under Waterloo Bridge, outside the NFT) to leave, en-masse, between 6:30 and 7pm for a jolly ride around this fair old city. In the summer months, this figure swells to 1000+ and really is a sight to behold.

Several sound-systems already exist. Some are purpose built, only for ‘CM’ or ‘the mass’, others are borrowed or multi-tasking beasts. This is not an un-loved section of the hifi community – there is a flickr group aimed squarely at the adoration of such musical conveyance. But you can never have enough choice, and so the “white-box soundsystem” was born.

I used to own a car, worth all of £500, it was awesome in every respect. It took abuse, jumped the odd bridge, went to Glasto when they still made you drive through crazy tracks, and then it had the audio-overhaul which cost about £200 all-in. Might sound a lot for some people, but it worked out rather well. There was a JL-Audio (8w6 dual voice coil) sub, in a small, sealed, MDF box. There was also four 5 ¼” Infinity coax drivers, which really do sound very good, and better still if you don’t try to send them any bass. Add a steal from Ebay – £40 for a 4 x 60Watt Kenwood amp + 1x200watt mono sub amp made the perfect combination. The key ingredient was to not send bass to the tops, and not send tops to the sub. Did it. Sounded *awesome*, if I do say so myself.

So I had four coax speakers suitable, bit heavy (all together) and not particularly efficient, but they do sound nice. The use of the ubiquitous MDF wasn’t an option – far too heavy. I had previously played with some foam-board, the stuff you usually mount photos on to. While foam-board is soft to ‘crushing’ it is quite structurally strong. I gave it at a whirl armed with nothing more than some superglue and a craft knife. What a combination! It’s amazing how strong this stuff is if applied in the right way. If you see the pics, the biggest challenge was cutting the angles correctly so that gluing was possible. In some cases I used the ever-amazing “grip-fill” instead. Jesus – that stuff has a reputation, and not without merit. It sticks anything to anything. Forever.

The foamboard was bought in London Graphics for about £10. The speakers I already had. I made the box, with superglue and gripfill. The difficult bit was mounting anything into a foamboard structure. Normally you would simply screw into the box – but this wasn’t possible, if you screw into foamboard it just pulls out straight away. The speakers themselves were screwed into those metal ‘clips’ you get with car speakers to clip around thin parcel shelf fibre-board to give something to screw into. This works fine with board-board but the entire clip must be on the inside of the box rather that clipped around the thickness of the material. I also had a lid on the box which posed its own problems. While the ‘clips’ would work when held in place, it would only work so long as you can hold the clips in place with your hand while screwing from the other side. This can’t be done if you’re securing the last panel of an enclosed space, so the ‘lid’ needed captive nuts. A speaker mounting kit from Maplin had such nuts in a 4x pack, and perfectly resolved the problem of how to secure the removable lid.

Box completed. More to follow.

It’s good to be back.

BBF — Fri, 22 Dec 2006 12:56:00 +0000

Homeward bound. While the pilot had mentioned that there was low cloud and fog in London, never did it become an issue. It was only while talking to the cab driver on my route from Paddington Station to home did I realize that many flights were delayed or cancelled. It may have explained why I didn’t wait very long to get through immigration!

The cabbie in a broad cockney accent said “are you takin’ the piss like?” After I mentioned it was “good to be back”. I guess he was just seeing the freezing fog and traffic, whereas I was seeing some familiar turf. I think I counted more motorcycles and bicycles in three minutes that I did in three weeks in L.A. – despite freezing fog.

CSI – wtf did it go!

BBF — Thu, 21 Dec 2006 13:50:00 +0000

OK, so this is a RARE occurrence by any standards including L.A. But what was probably a bullet made this hole in the office window at some point over the weekend. No-one could find any other holes or fragments apart from bits of glass.

Vomit rocket and Frys please.

BBF — Thu, 21 Dec 2006 07:28:00 +0000

I went to check out some roller-coasters after finding that ‘Six Flags’ Magic Mountain was only 30 miles away. Despite forecasts of possible rain, we set off and were delighted to find that the place was almost empty. We waited no more than 3 minutes to get on any ride we wanted, and quite often just strolled straight on. Magic Mountain is dominated by roller-coasters, you won’t find many fairground gut-churners here.

The problem I had was that without the delay of queuing, it’s quite easy to blast onto three or four rides in quite succession without a pause and become a bit nauseous. Time-out was required.

We, rode, flew, hung and stood on all the rides available. Don’t make the mistake of being on a stand-up ride and being on tip-toes when the seat locks. Well, it’s more of a bike saddle than a seat. You then have to endure high g-forces without being able to take your weight on your feet. Nnnnnnnggg…

The undisputed favourites where ‘Tatsu‘ and ‘Scream‘. Scream was fast and noticeably smooth compared to the others, some of which tended to throw you around a bit. Most vomit inducing may have been ‘Deja-Vu‘ which starts by hauling you backwards up a vertical rail and dropping you after a pause. Once you do the ride forwards, you do it all over again but backwards. Definite vomit points here. Goliath towers up way over two hundred feet, but the tallest structure in the park is the Sky Tower viewing platform at 384 feet tall.

After fighting the urge to vomit, we left Magic Mountain and called in at the humongous electronics store that is Frys. It is h-u-g-e. It has pretty much anything you could want from De-gaussing coils (!) to electrical components, to computer cases, to memory, processors, monitors, cables, ipods, headphones, cameras, tripods, lenses, books, CDs, DVDs, TV screens, washing machines, dryers, cleaners, etc etc etc. Very keen prices and massive range too.

Everything pretty much was obviously cheaper.

Groceries revisited

BBF — Thu, 21 Dec 2006 06:59:00 +0000

Aerosol cheese. Discuss.

I can’t remember if I’ve seen this in the UK or not, but if it never makes it to these shores it would be a good thing. It’s gross! Not so much because it’s in an aerosol, but because it doesn’t really even taste of cheese, and has a very strange hint of butterscotch too. Arrrg!

So now that the sensory overload has died down (first time I went into a grocery store I couldn’t find ANYTHING) I noticed a few more completely trivial things…..

Cheese is never referred to as ‘mature’ i.e. Mature Cheddar Cheese, nope instead is it ‘Sharp Cheddar’.
Bacon comes in no less than 1lb packs (18 rashers), and there seems to be no distinction between ‘Back’ and ‘Streaky’.
Continuing with that theme, quite often I only found eggs in packs of 12 or 18.
All milk has “Vitamin D” plastered all over it. “Skimmed” milk is called “No Fat”, and Semi-skimmed is called “2%”. There is also “Half & Half” which is 50% milk and 50% cream mixed. Once, when I ordered a take away coffee, I asked for half-fat milk. The response came back with “You want it with percent?”
You can buy milk by the gallon, in a cube-shaped poly-bottle.

Ho hum.