Q-pack: Light weight sound system |
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Daniel Twellmann
Registered User Joined: 02 October 2011 Location: Denmark Status: Offline Points: 48 |
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Posted: 08 August 2014 at 9:27pm |
Hello world
My Friend, Q, has asked me to build a sound system for him, which I have dubbed Q-pack. He has borrowed my backpak sound system and wanted something similar for himself. My system consists of:
The whole thing was thrown together almost from scraps and extras, because why not. It has seen a lot of use and has never failed, except from a replaced battery. It has prominent peak somewhere around 200-250hz which makes synths and male voices quite powerful, but there is not a lot of bass. The drivers are placed two on each side and the solar panel is slanted 45deg and facing away from the shoulder straps. All in all a compact, but powerful packages. It's biggest problem is the weight, which is why I'm starting this thread My friend is an avid athlete who recently started doing marathons and triathlons, and has played badminton for almost twenty years. Because of all these activities he would like something a bit more, shall we say trimmed. Furthermore he is quite the fashionista and likes things to look clean and neat, as opposed to my system which looks like its been to Wacken and back. He also would like for it to fit on his around the bike, which has a small basket on the rear rack. The last thing he requested was that the system could also be used for sitting on, not like a chair, but more like a comfy wooden box . So, to sum up my(his) design criteria:
To fulfill these criteria I've made some preliminary design choices for the Q-pack:
This is it for now. Please comment on anything you like, pictures and links will slowly emerge |
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WesleyK
Registered User Joined: 24 December 2012 Status: Offline Points: 90 |
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Nice! Looking forward to the results of this build :) . One little correction: the SP60 drivers are about 650gr each instead of 900gr. Still on the heavy side, ofcourse.
Edited by WesleyK - 08 August 2014 at 9:48pm |
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Daniel Twellmann
Registered User Joined: 02 October 2011 Location: Denmark Status: Offline Points: 48 |
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Silly me, trusting the datasheet |
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WesleyK
Registered User Joined: 24 December 2012 Status: Offline Points: 90 |
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I will put them on my scale tomorrow for you. I believe they are about 660gr each, but can't give you the exact figures yet.
Edited by WesleyK - 08 August 2014 at 10:30pm |
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Daniel Twellmann
Registered User Joined: 02 October 2011 Location: Denmark Status: Offline Points: 48 |
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Thoughts on the power source for the Q-pack:
The Amp6 and MaxAmp2 has an average current draw of about 300mA at maximum volume. I believe this is shown empirically by Saturnus for the boominator, but I'm not 100% sure. I have never really measured/observed the power consumption on my other builds. A Bluetooth reciever uses some unknown amount, but probably not more than 100mA. So on average 400mA on full tilt with bluetooth activated. I need a minimum of 8-10 hours of playtime, so I need a battery with around 3000-4000mAh capacity. In order to shed some weight I'm looking into a Lithium based solution, most likely a LiPo pack similar to this: http://www.hobbyking.com/hobbyking/store/__7634__ZIPPY_Flightmax_4000mAh_3S1P_20C.html This type of battery needs a balancing charger in order to prolong the life of the battery, and also to prevent charging accidents: http://www.hobbyking.com/hobbyking/store/__30032__HobbyKing_E4_Balance_Charger_EU_warehouse_.html It also needs some battery protection: http://www.ebay.com/itm/Protection-Circuit-Module-3S-8A-PCM-11-1V-Li-ion-Li-Polymer-Battery-4S8AL-/221181041984 Some sort of charge indicator is also desirable: http://www.batteryspace.com/fuelgaugeforpcbof111vli-ionbatterypack1.aspx I tried to look into LiFePO4 chemistry, but I don't know anything about them to be honest , so if any you have experience, please chime in
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Saturnus
Old Croc Joined: 13 July 2010 Location: Copenhagen Status: Offline Points: 2025 |
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Some people builds a halfinator (half a boominator) with the lite speakers (basslite S2010 and pht407n, you can get both from blue aran and other sources) for backpack use. That is 30x30x50cm so much closer to the original required measurements, and about 8kg including lifepo4 batteries. They then use a diver's harness to carry it which is extremely well balanced and can carry a lot of weight (and since they have to meet very rigorous safety requirements they're also pretty damn near indestructible). You can even use a solar panel on one side to make it pretty much last forever.
Regarding power consumption. The TA2020 is about 360mA just before clipping, and about 110mA at lower listening levels. The maxamp20 is about 320mA and 80mA respectively under the same conditions. However, that's into 4 ohms. In 8 ohm it's slightly over half that for the maximum volume number and about 2/3rds of the lower volume number. I'd strongly suggest building a halfinator for this. It's pretty much a perfect fit. Though I can certainly understand that you'd like to make your own design.
Edited by Saturnus - 09 August 2014 at 9:25am |
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Daniel Twellmann
Registered User Joined: 02 October 2011 Location: Denmark Status: Offline Points: 48 |
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The footprint can't be more than 38x20cm, and the basslites will break the budget, otherwise it would probably be close to perfect. How about charging the LiFePO4s? How do you accomplish that?
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lutkeveld
Young Croc Joined: 23 September 2013 Location: The Netherlands Status: Offline Points: 517 |
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How about 2 Dayton ND105's in a 16-18 liter enclosure tuned to 50hz.
-360gr each -F3=42hz -Bump at 60hz -87dbwm To keep the weight down you can get a 4400mAh LiFe battery from Hobbyking. Only 30 euro's and it can be charged within half an hour if your charger supports such high charge rates. You can charge it with a SLA charger but you'll only utilize 80% of its capacity. With a special LiFe charger you utilize its full capacity. |
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Saturnus
Old Croc Joined: 13 July 2010 Location: Copenhagen Status: Offline Points: 2025 |
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The 87db/w/m is wrong. Datasheet says 83 for the 8 ohm version and 82 for the 4 ohm version. Both are a little optimistic as well. They're about 1 db below that really.
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lutkeveld
Young Croc Joined: 23 September 2013 Location: The Netherlands Status: Offline Points: 517 |
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WinISD showed combined sensitivity, so -3db for one unit. Around 83db average indeed.
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slaz
Old Croc Joined: 27 November 2009 Location: London E2 Status: Offline Points: 2713 |
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Well - if its any help - I'm successfully using a Zippy branded 5000mAH 6S Lipo pack to drive a Sure STA508 amplifier ..... LipO pack and Turnigy Accucell 6 balancing charger bought from Hobbyking. I was going to go LiFePo4, but there were some bad reviews of the Hobbyking-supplied packs. Watch out a bit for Hobbyking - they're a bit slippery .... I thought I was getting delivery from a EU warehouse, but it actually shipped from HK (took nearly 3 weeks to reach) .... high shipping charges buried deep until last phase of checkout ...... and they're pretty hardcore with the "marketing" email. I'm quite pleased with the performance of the LiPo pack though ..... I have reason to think the real-world capacity is close to spec. The STA508 gets powered by the 5000mAH LiPo pack for portability mode, and by 2 x 7Ah SLA in static mode. The LiPo pack weighs about 750g - so much lighter (and smaller) than 2 x 7Ah SLA. The connections are a bit awkward - you need those 4mm HXT connectors/adapters and the JST-XH connectors for balancing ..... would be a PITA if mounting battery inside your box ..... I like flexibility wrt power, so I always have batteries external anyway. The Accucell charger works well - caters for Pb, NiMH, Li-ION, LiPo and LiFePo4. |
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REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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Daniel Twellmann
Registered User Joined: 02 October 2011 Location: Denmark Status: Offline Points: 48 |
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Is there a way to make sure it is from the EU warehouse?
I've been thinking about the charger connection as well. I was considering rewiring the connection to a multipole plug, maybe 5 pin XLR or something. Edited by Daniel Twellmann - 09 August 2014 at 3:25pm |
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