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Hi all, I'm considering plans for a new DIY project that's a variation on the portable boombox concept, hopefully with a more linear frequency response due to higher quality drivers and equalisation and (possibly) digital crossover using MiniDSP. The other major difference would be that the system would be modular, i.e. each driver would be housed in its own box, as would the mimiDSP/battery/PS/amp, and all would slot and fix together making them usable as either a portable boombox, or, at home, a 3 component (2 x speakers + 1 x amp/crossover/psu) system. It won't be dirt cheap, but I do want to keep costs down and try to achieve similar sound quality to a similarly priced consumer hifi system, so around 300-350€ (I'm in Germany these days, hence the Euro) or a bit more if I go for a more complex design. Similar projects have been written up extensively online as 'DIY boomboxes', but the main differences I'm considering in my build are: - the addition of a MiniDSP chip (or two) to improve the frequency response and (possibly) to replace the passive crossover with an active crossover - the use of modular boxes, allowing the system to be utilised as separate components I've chosen the PC165F because they are coaxial (making them easy to deal with) and relatively sensitive (91.9db @ 2.83V/1m), yet (according to Focal at least) have a reasonably linear frequency response and decent dispersion characteristics, as well as sufficient bass extension. On the other hand, I'm concerned about the high resonant frequency (70hz) and the high magnitude of the resonance peak (over 50 Ohm), especially given this will be powered off a cheap battery. So at this stage I'm also open to other driver suggestions. Input will be stereo RCA (or 3.5mm jack) into MiniDSP. From there, I am considering the following options: (1) MiniDSP as EQ (only) / 12V lead acid battery The MiniDSP would be used simply to create a high pass (maybe 40hz) filter, compensate for baffle step, and iron out frequency response problems in the mid and (particularly) high range. I would house the coaxial drivers in well constructed 10-15 litre MDF boxes, and use either sealed boxes or more likely ported boxes, tuned (hopefully) to around 50hz. The MiniDSP would provide a quite steep high pass filter at 40hz-ish, and some EQ to compensate for baffle step and iron out irregularities in the response. This is the concept in a microsoft paint drawing: The basic equipment I have in mind for this is as follows: 1 x MiniDSP 2 x Focal PC165F 1 x Hifimediy T1-M TK2050 1 x 12V UPS lead acid battery 1 x switching PSU With this configuration, I have these questions: Power Is it a good idea to use a 12V UPS lead acid battery for something like this? The basic reason I have it in mind is that it's cheap (around 10-15€) and easily replaceable. Are there better ideas for the battery? If I do use such a battery, how do I set up the system to: (1) run off the PSU when plugged in and switched on, (2) charge the battery when plugged in and switched off, and (3) run off the battery when unplugged? I'm an electronics novice but a patient learner. Is this something I can realistically and safely achieve? Is there a simpler way of doing this that I'm missing? For example, is there a ready-made battery/psu that I could choose that would recharge and provide power to the system at the same time, so that I don't need the PSU or any kind of switch? The miniDSP also needs to draw a small amount of power from somewhere. Where would this come from and how would I make it work? Speakers These drivers have slightly odd parameters as I mentioned before: Will that very high magnitude resonance peak be a problem for a relatively low powered amp like the Hifimediy T1-M running off a 12V battery? The amp is 57w into 4Ohm with a 24V DC supply, but where the resonance peak is it would be running off a 12V DC supply into probably at least 40 Ohm (I am assuming that the heavily damped ported box will move the resonance up a bit from 70hz and reduce its magnitude somewhat). My understanding of how this amp works is that it might struggle to produce much power in this frequency region, is that right? Boxes The driver parameters suggest a ported box will work better, and since these are going to be midwoofers, ports would make sense from the point of view of efficiency. Can anyone see a problem with using a 10-15L box with damping material, with a 5cm diameter port tuned to quite a bit below the Fs (hopefully 50hz), and a digital high pass filter just below the port tuning frequency? (2) Extra amp and sub This would involve adding an additional monoblock chip amp and a small high-efficiency sub, which would most likely be housed in the central unit with the battery and amps etc. This would change my power supply needs, but I'm not sure I understand how. Assuming I found an efficient D-class monoblack 50w or 100w change amp, how would I calculate my power requirements? Would there be any chance of sticking with the 12V lead acid battery or would I simply need to abandon this idea? And does anyone have any suggestions for a decent, small (ideally 8 inch) and efficient subwoofer and amp for this arrangement? (3) MiniDSP as crossover This design idea would be very similar to (1), but in this case the miniDSP would split the input between the woofers and tweeters and replace the passive crossover in the driver unit. There would be an additional Hifimediy T1M amp giving a total of 4 channels. My question here would again be about the battery and PSU. If I were now powering two Hifimediy T1-M's off one PSU or battery, how would that change my power requirements? Would I need a more powerful battery? If so, how powerful would it need to be, and does anyone have any idea what I might use? (4) Extra amp and sub / 2 x MiniDSP This would be the most complex setup and would involve housing an additional sub in the central unit, adding a MiniDSP to create a 2.1-way crossover, and adding an additional sub amp. My question about power supply / battery is similar to my question about the extra amp in design (2) and (3). How would I calculate my power requirements? Are there any suggestions for batteries / PSUs? (5) 2 x sub / 2 x MiniDSP This is basically like design (3), but there are 2 subs instead of one and an additional stereo amp (rather than a mono amp) to power them. The subs would either both sit in the central unit or would have their own boxes, ideally also not much bigger than 10-15L in size. I guess my questions about this design are basically the same as for design (3). Many thanks in advance.

Please share any design tips for a bespoke DIY high efficiency, audiophile tolerable stereo system, built to run off a minimalist solar powered battery array for a future holiday cabin fantasy. The power system will likely be low powered with just 12V 390Ah storage. Id like a system that has a maximum peak draw of 20A at 12V so 240W at most with about 50W average maximum. It would be fun to build a system that runs on just 20W if possible. There will be no 230VAC grid or generator backup, thus the emphasis on designing a high efficiency system from the ground up. Maybe that should read from the sun up. Is it possible to design gear that runs directly off battery 12VDC (max 13.3V on full charge) without needing an invertor? Will D-class power amps be important to minimise the peak power load and W-hr drain? What about the speakers. Will horns be mandatory for high efficiency?

Hi all I am hoping for some good advice for an outdoor projector for use with the Australian Summer looming! I would prefer a battery powered unit to save running a cable every time I use it. Also want something that can easily be used with Netflix and similar, either with apps on the unit itself or streaming via an iPhone / iPad. Options seem limited in Australia. The best generally on sale here seems to be the Nebula Capsule but my research found the Nebula Mars 2 which does seem a much better product though only available here on import. Then there is the Philips PicoPix Max being crowd funded: https://www.indiegogo.com/projects/philips-picopix-max-1080p-full-hd-pico-projector?gclid=EAIaIQobChMIh-SylMbt5AIViIePCh0NDwdAEAAYASAAEgKuQfD_BwE#/ That looks great but I am concerned about no product reviews being available. Has anyone gone with this or have any thoughts I should consider. Also, what do I need to look for in an outdoor screen. I really want something quick and easy to put up. Thanks so much

I'm keen to try a Nagra BPS, not that fussy on condition as long as the function is unimpaired. Cheers

Item: Ray Samuels Nighthawk F117 Phono Amp Location: Melbourne Price: $500 Item Condition: Excellent Reason for selling: Downscaling my gear collection Payment Method: Pickup - Cash, Paypal, COD Only Extra Info: Hi there, After several years of loyal service, I am reluctantly moving this excellent amp on. I don't think I need to speak to much about the quality of this piece equipment - it's bloody awesome. This particular unit is in great condition, has been used minimally in a smoke free home. Battery feels like it's still holding it's charge like the day I bought it. Happy to answer any questions. Oh, I realise I forgot to photograph the Charging unit! But don't worry, I have it. And if you really need a photo of it I'm willing to break my back bending over the back of my hi-fi shelves, battle my way through the deadly tangle of cables, and retrieve it for a photo shoot. Actually, I have to do that anyway for when it's sold, so I suppose I should just man up and do it now.... Photos:

For Sell : Jeff Rowland Coherence II preamp (with Battery Power Supply) Finishing : black. Voltage : 210-240 volts original . Stereophile Recommended Class A preamp & winner of Stereophile Products of the Year Award . Condition : 8.5 of 10 (excellent condition) . Include : - include brandnew battery for BPS - copy manual book - remote sensor/display unit - remote control - original DC power supply cable : 2 meters length (which made by Cardas) Price : A$ 8.2k Price already include one day "door to door" shipping by Fedex . I can accept Paypal (must add 4% fee) & bank transfer . Contact me : +62 (81) 132 9979 (possible by call/Whatsapp/SMS) or by PM . I'm in Surabaya - Indonesia (possible pick up at my home ) Merry Christmas & Happy New Year 2014 !!!

Item: Battery DAC, TDA1543, Non Over Sampling (NOS) Location: Brisbane Price: SOLD Item Condition: As new, unmarked - also will ship in the packaging it cam in Reason for selling: Surplus and have upgraded to new model Payment Method: EFT, PayPal as friend, Cash Extra Info: Highly regarded DAC, sweet and detailed sound with great imaging and tone. NOTE - This is the upgraded dual Battery model Pictures: Of actual unit From the website - What are the main features of this DAC ? And what are the main goals of its design ? Extract the pure performance of the last built non-oversampling true 16-bit TDA1543 DAC from Philips Optical & Coaxial inputs (leftmost switch on the photo) DIR9001 96 kHz SPDIF Receiver (lowest-jitter on the market - 50ps) Supports sampling frequencies from 28kHz to 108kHz (continuous range, including non-standard frequencies) TDA1543 16-bit DAC - the original from Philips® Passive I/V conversion No Op-Amp - direct output with 2Vpp (will drive any power amp well) Huuuge capacitors on the output path provides sub-Hertz cutoff frequency (<0.3Hz on a 10kOhms input) Dual Stage power supply regulation (for a super low background noise level) Separate voltage regulator for the DAC and the Digital SPDIF receiver (same reason as above) Battery-powered with a single 9V NiMH battery (optional - but without it you must provide a clean 12V - 15V power supply) Smart battery charger on-board (quickly charges the battery when depleted, keeps it charged at low current when idle) When both power switches are on, the battery is recharged, and is also used to buffer the external power, completely removing hum. Will Directly drive any power amplifier Easy to carry around and use it at your friends home 2+ hours of listening on the battery alone Thread - http://www.stereo.net.au/forums/topic/71210-“the-battery-dac-“-impressions/

Item: Battery DAC, TDA1543, NOS Location: Brisbane Price: $170 plus postage Item Condition: As new, unmarked - also will ship in original packaging Reason for selling: surplus and have upgraded to new model Payment Method: EFT, PayPal as friend, Cash Extra Info: highly regarded DAC, sweet and detailed sound with great imaging and tone. NOTE - This is the upgraded dual Battery model From the website - What are the main features of this DAC ? And what are the main goals of its design ? Extract the pure performance of the last built non-oversampling true 16-bit TDA1543 DAC from Philips Optical & Coaxial inputs (leftmost switch on the photo) DIR9001 96 kHz SPDIF Receiver (lowest-jitter on the market - 50ps) Supports sampling frequencies from 28kHz to 108kHz (continuous range, including non-standard frequencies) TDA1543 16-bit DAC - the original from Philips® Passive I/V conversion No Op-Amp - direct output with 2Vpp (will drive any power amp well) Huuuge capacitors on the output path provides sub-Hertz cutoff frequency (<0.3Hz on a 10kOhms input) Dual Stage power supply regulation (for a super low background noise level) Separate voltage regulator for the DAC and the Digital SPDIF receiver (same reason as above) Battery-powered with a single 9V NiMH battery (optional - but without it you must provide a clean 12V - 15V power supply) Smart battery charger on-board (quickly charges the battery when depleted, keeps it charged at low current when idle) When both power switches are on, the battery is recharged, and is also used to buffer the external power, completely removing hum. Will Direclty drive any power amplifier Easy to carry around and use it at your friends home 2+ hours of listening on the battery alone http://www.stereo.net.au/forums/topic/71210-“the-battery-dac-“-impressions/