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james folkes 
Old Croc 
Joined: 08 January 2005 Location: United Kingdom Status: Offline Points: 3064 |
 Posted: 20 November 2009 at 7:29pm |
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ind.st's gabba wheelbarrow pa of death.
scourge of shamania festival and companion on many an adventure. the little philips speakers (late of the national centre for popular music) are bob on, sadly one of them got a bit wet at glade 07, but what didn't? the sub is a fairly interesting series tuned 6th order effort from tannoy, being a cpa5-sb, the internal passive crossovers make it a cinch to use without complex amplification solutions, a boon for 12 volt use. there used to be little brackets with them and bolting them to the hubs of the geodesic dome made for an excellent festival lounge.  a new 12 volt rig is currently in the offing: designed around a push-bike trailer concept it's debut on the sheffield scene is long overdue, but then again everything i'm involved in generally is. hey-ho... james.
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mardy hippy.
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rich_gale
Old Croc
Joined: 18 February 2008 Status: Offline Points: 2697 |
Posted: 20 November 2009 at 9:51pm |
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nice! i see a rather formidable battery bank hidden under the sub.
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REFLEX ALL THE WAY.... (however, im playing with horns again...) That ok Mister Valiant? :)
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james folkes
Old Croc
Joined: 08 January 2005 Location: United Kingdom Status: Offline Points: 3064 |
Posted: 21 November 2009 at 2:10pm |
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indeed sir, those are 6 volt, 110 amp-hour beasties out of sheffield town hall's old fire alarm system. i used to have 4 but i gave 2 away to some friends who live off-grid. i've got piles of 38 Ah 12s too, that's what i'm going to use for my new one i think. what with the weight of the trailer, amps, drivers etc i have considered trying to separate the battery packs for when travelling on anything other than flat ground, i'm also quite tempted to build in a hydraulic trailer brake too... can you imagine jack-knifing on a push pike with nigh on 100 kg of pa crashing into you? indeed...
i just ebayed a kenwood kac9152d for the bass section, it's one of the few true monoblock designs that can be bridged with another unit, giving us a modular upgrade route that won't break the bank. i'm building around a 6 ohm phl 15" and the kenwood should give me at least 300 watts with that kind of load (which in a high efficiency enclosure should give us bass we can work with), annoyingly the lpf only goes up to 200 Hz and i intended to cross at 250-ish, but i kind of gave up waiting for a suitable unit to crop up at the right price. i've seen some really nice cycle powered generators of late which has given me a few ideas. if we could tow one of those around with us too then not only could we carry fewer batteries, but the greater supply voltage of ~14.6 during charging gets a good 30% more welly out of all the amps, although we might need to look into a 1.0 farad cap to keep the current to the bass amp(s) more consistent during transient peeks. come to think of it, my old martin 215 mkIIs are full of baked bean tin sized caps, shove all 12 of them in parallel on some nice solid copper rails and we'd be cooking with gas. james.
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mardy hippy.
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rich_gale
Old Croc
Joined: 18 February 2008 Status: Offline Points: 2697 |
Posted: 21 November 2009 at 8:12pm |
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nice when someone goes into detail about their system concepts. i was exactly the same when it came to choosing the class d monoblock in my rig. luckily i got a very nice memphis 500wrms@2r which will go up to 250hz. cost me under £35 because no one knew the manufacturer in the uk . i run it at 2r so feed each pd 12" a solid 200wrms or so. that magic 250hz seems to be ideal to allow smaller cabs to do the rest of the range. any lower than 200-250 and the mid/high cabs need so much more power amp capability.
over 12v is where the party starts. my memphis will take 16volt all day and burp use at 18volt. the power output apparently get huge at 16v but it gets warm so i have fitted a 12v fan.
where you based james? did you say you were in bristol?
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REFLEX ALL THE WAY.... (however, im playing with horns again...) That ok Mister Valiant? :)
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SamV
Old Croc
Joined: 21 October 2008 Location: London Status: Offline Points: 8711 |
Posted: 22 November 2009 at 1:03am |
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Are you going to build you're own trailer? Beatrix weighs near on 100kg and rides on an unbraked trailer and I've never had problems with jackknifing. The only thing is to make sure that your bike's brakes are good enough and that you have a decent wheel rear as it will bear some of the load from the trailer on anything other than perfectly smooth tarmac. Having a brake on the trailer issa bit risky. I've tried having a brake and it just makes it dangerous. And that was on my trike which is more stable than an upright. Make sure your towarm is low and that you have a strong hitch (ones connecting to your drop outs are the best). Most trailers under £100 will buckle with a near 100kg system on it. I found this out the hard way :( Also from experience a cap would make little to no difference.
I have a Kenwood 930D I think doing bass on mine running 4x JBL GT4 subs ported. Edited by SamV - 22 November 2009 at 1:05am |
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james folkes
Old Croc
Joined: 08 January 2005 Location: United Kingdom Status: Offline Points: 3064 |
Posted: 22 November 2009 at 6:10pm |
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i'm interested in your experiences there sam, the capacitor bank would be bulky and would represent an energy discharge hazard, maybe we will give that a miss, i think a few experiments would help make my mind up, i know they can really make a difference to delivering bass transients on some of my friend's auto installs.
what i'm really surprised to hear is your feelings on braked trailers. living in the peak district the the concept of towing 100 kg un-braked is practically unthinkable. i've had some bad experience towing various trailers with my land-rover, the worst of which happened on an un-braked and overloaded sankey and i ended up leaving the road very unceremoniously. we're not building the system to fit a trailer, we're using the cab itself as a stressed member and bolting the wheels on the sides, saving weight and allowing the centre of mass to be lowered over a conventional flatbed trailer. 26" mountain bike wheels from the scrap pile are to be employed, the hitching system will be based on others that use the drop-outs, i've also found that works best. you may well turn out to be correct about the trailer brake, but i'm not prepared to omit it from the design at the moment! james.
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mardy hippy.
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james folkes
Old Croc
Joined: 08 January 2005 Location: United Kingdom Status: Offline Points: 3064 |
Posted: 23 November 2009 at 1:46am |
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i'm up in sheffield rich, don't get down the south west anything like as much a i'd like to. that memphis looks good, 250 Hz really was what i had been holding out for but everything suitable went for daft money. the healthy power output of the kenwood (500 @ 4r @ 14.6 V), keen price and the fact that another will turn up before too long and i'll be able to spanner my single driver with nigh on 1.5k if necessary, meant i felt i'd made a fair compromise...
...not that i'm sure it will be necessary. i had a little play with a new maystar amp that i bought by accident, turns out it was a happy accident.  this cx255 model has rather handy filters on the input and pass-through connectors. feeding that with a laptop driving full range toa install boxes, pass-through connectors feeding the ageing sanyo amp which was bridged into a single 15" reflex. when i hooked the battery up and had a blast i was refreshingly surprised. the bass was getting less than 100 watts, the tops about 20 each and the room was getting a good workout. output for the size and power was superb, but what really won me over was the quality. the toas are lovely little cabs and the bass is a p-audio bm-15lf (one of their really sweet drivers) tuned fairly nicely so the ingredients were there, the amps filled in the rest of the equation and left me with a big smile. the bass particularly had a really warm tone without loosing good tight control of the cone, and this is on a fairly entry level bit of kit. but yeah, already fairly loud and really pretty sweet! i've not been so excited about a pa project in years, i have a feeling it's going to see a lot of action in the future as we are forced in to more discrete and elusive small-scale partying. stealth parties... oxymoronic, but a noble enough goal. james.
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mardy hippy.
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rich_gale
Old Croc
Joined: 18 February 2008 Status: Offline Points: 2697 |
Posted: 23 November 2009 at 10:43am |
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yes. my memphis is 'stackable' too. im gonna get another one soon. will give a healthy 1k into a 4ohm load then.
im loving your power wire...:) 5amp is that? lol. im the same, put a thin power wire in as makeshift and then when you want to turn it up it ends up getting warm. and i bet you cranked the system so it was pulling 20a at times.. haha
nice to hear it all is working nice. something very satisfying when you get a battery powered system that doesnt sound like its running from a battery
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REFLEX ALL THE WAY.... (however, im playing with horns again...) That ok Mister Valiant? :)
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biotec
Old Croc
Joined: 07 June 2004 Location: United Kingdom Status: Offline Points: 2932 |
Posted: 23 November 2009 at 10:44am |
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how about a Christiana bike?
Its a type of three wheel cargo bike invented in the carless autonomous area of Copenhagen called Christiana.
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me so horny, me love you long throw.
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eltron
Registered User 
Joined: 21 December 2007 Location: Finland Status: Offline Points: 399 |
Posted: 23 November 2009 at 12:50pm |
This is what i've been pondering, and i have been looking for one for ages! There doesn't seem to be any second hand bikes on the market over here and no importer at the mo. Buying and shipping abroad proved to be way too expensive, would end up costing more than the sound inc. parts... I was in cph last summer and actually visited the christiania bikes shop in christiania. Manufacturing is done elswhere nowadays though. Jylland if i remember correctly... or is it even in denmark? Oh well. |
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SamV
Old Croc
Joined: 21 October 2008 Location: London Status: Offline Points: 8711 |
Posted: 23 November 2009 at 1:21pm |
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Too big/heavy and the brakes aren't great.
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james folkes
Old Croc
Joined: 08 January 2005 Location: United Kingdom Status: Offline Points: 3064 |
Posted: 23 November 2009 at 4:04pm |
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i like the funky and functional appearance of the christiana bikes, although as sam says they do look a tad weighty... might we just call it well built? the fact that they've got a stirmey archer hub gear on suggests they aren't taken up steep hills very often, likewise the lack of a hardline braking system. still very cool though, and a pleasingly simple solution mechanically.
i wondered if anyone would comment on the "silly string"... it's 2 x 0.75 mm, pretty weedy but it's what we used to use for 100 V line installs so i have - or at least had - a fair few miles of it knocking about. the real thing will of course use super-chonging fat boy cable, of whatever kind is handiest when building...
james.
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mardy hippy.
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biotec wrote: