Advice needed on compact HiFi componentry for school project

[Isaac Blanc]

Hello!

About me:

Before I start, may I just explain that my understanding of audio technology is pretty limited. I’ve taught myself the basics but, as this is for a one-off project rather than the beginnings of a hobby, I don’t know much more.

About my project:

For my school resistant-materials project, I’ve decided to build an iPod dock. It will need to amplify and play music. Rather than rely on battery power, it will plug into the wall and the audio input will be a 3.5mm jack. The exterior dimensions will be 400mm x 200mm x 200mm whilst the interior dimensions of the speaker enclosure (a simple non-ported design) will be 350mm x 150mm x 120mm. These dimensions are however not final – I can change my designs if need be. The whole product will be made from Baltic Birch Plywood. The final product needn’t be incredibly loud but I would like the sound quality to be quite good. I have a budget of £100 for audio componentry.

Question:

What audio componentry would you recommend I use in this project? As I understand it, I need the following:

A compact amplifier that will accept a 3.5mm audio jack as an input

A pair of full range 4” coaxial drivers

OR:

A compact amplifier that will accept a 3.5mm audio jack as an input

A compact crossover

A pair of 4” woofers

A pair of 1” tweeters

Are these the components I’ll need? If so then what specific parts would you recommend? Any other advice on the project would be greatly appreciated!

Thank you all in advance,

Isaac 🙂

 

[spiny norman]

Something like this would do the job, leaving you only to assemble it and build the casework: if you choose the version with the iPod connector lead instead of the 3.5mm phono, you could create an iPod dock as part of the case, which is probably worth extra points!

Or, if you'd rather have the amp electronics ready built, you can find lots of Class D-type 'amp on a board' solutions from suppliers in China or Hong Kong on sites such as e-bay. Choose one with a volume control built-in, rather than those advertised as just power amplifiers, and then source the extra bits you'll need such as connectors, control knobs, speakers, power supply and cables from somewhere like Maplin.

 

[iQ Speakers]

Great project and an excellent solution. If you wanted to veneer it would be happy to supply the veneer and glue, though baltic plywood can look really good if fiished properly with that end grain. good luck.

 

[splasher]

When you say coaxial drivers, do you mean coaxial as in woofer and tweeter on the same axis like Tannoy or KEF. If so, I think you would still need a crossover.

 

[Isaac Blanc]

Contrary to how it may sound, no sarcasm intended in the title. I'm genuinely quite surprised (pleasantly of course) by the useful, kind responses I've received on this site as well as many others. Thank you all for your responses. I'll reply to you one by one... Spiny Norman:[/b]I really like how the kit comes with all of the electronics. It will save me the considerable worry of components not being compatible. The Apple plug thing is also very cool and would likely gain me extra marks. As you suggested, I will probably try to mount it into the wood of the product as would be done on a professional iPod dock. Thank you for finding me this kit, it is definitely the best possibility yet! I have a few qualms though... 1. The soldering all looks fairly easy but I worry about ending up with a crackly sounding output. Is this likely? I can solder very neatly and my welds are always well-sized, but I doubt that makes me a pro.2. Considering that this includes everything, I find it shocking that the price is so low. I don’t know a whole lot about speakers, but I worry the sound quality from a £30 kit is going to be pretty terrible. What do you think? Do you know of any higher-quality kits like this? iQ Speakers:[/b] Thank you for your kind words about my project! It’s also reassuring to hear you say that Norman’s suggestion is a good one. As much as I like the simplicity of buying everything in a kit, especially one that includes an iPod plug, I worry that, for £30, the sound quality really won’t be up to much. What are your thoughts on this?Initially, I did indeed plan to apply a veneer, Burr Maple to be precise, however my teacher told me that doing so could very easily go wrong, especially as my design is quite a curvy one. Normally fear of failure shouldn’t hold someone back but, when making your GCSE RM project, it really should. Due to the tight timeframe of school, if I screw up my first attempt then I screw up my marks. There really isn’t time for a second try. Besides, as you said, Baltic Birch Plywood can look really nice if well finished. Look at this for example! Splasher:[/b]Yes I do mean exactly that and it varies: some coaxial drivers do require crossovers whilst others have them built in.

 

[Isaac Blanc]

For some reason, this website decided to remove all of my paragraph breaks. Sorry if this makes it hard to read!

 

[spiny norman]

The specs of the chip-amp used in that kit seem pretty good, and you have enough left in your 'electronics' budget to improve the speakers should these prove the weak link when you have the amp put together and hooked up, though I doubt they will.

I wouldn't expect a sound quality to challenge high-end hi-fi from this kit, but provided you take some care with the design of the 'box' - such as individual internal partitions to create separate 'chambers' for each of the speakers and the amp section – you should be able to achieve a sound on a par with commercial systems of this kind.

After all, I doubt many of the affordable all-in-one iPod docking systems on the market use components costing much more than this! ;-)

 

[Isaac Blanc]

Okay, awesome!

In that case I will most likely buy this kit. Decision made!

One last question, do you have any tips/advice for soldering the amp? Surely any imperfections will result in crackling or distorted sound-quality. Should I use flux when soldering to keep the connections pure for instance?

Thank you once again for your help 🙂

 

[Isaac Blanc]

Great advice. Thanks 🙂

As I am new to using flux, do you have any recomendations for what flux core solder to buy? Sorry if that's a stupid question.

 

[Isaac Blanc]

Would it be worth lining the inside of my enclosure with convoluted foam?

I've seen this done many times but don't fully understand why. Therefore I neither know what type of convoluted foam to use nor whether to use it at all.

Thanks in advance...

 

[Isaac Blanc]

Thank you for the advice and the good luck. I understand what you're saying and I've taken note. I'll be in touch again if I have any more questions or need foam 🙂

Thank you again for your help!

 

[andyjm]

Great advice. Thanks 🙂

As I am new to using flux, do you have any recomendations for what flux core solder to buy? Sorry if that's a stupid question.

Go on to ebay and type 'multicore solder', that will bring up any number of suitable products.

Practice soldering a few times before having a go on your board. Better to mess up on something that doesn't matter. There are plenty of 'how to' videos on youtube. I would suggest you watch a few before having a go yourself

Good luck.

 

[Vladimir]

Just buy flux core solder.

Most important thing is not the tidy soldering but maintaining accurate polarity of the components. If you install a polarized cap in reverse order it will pop and possibly damage the board and other components. Tripple check polarity before feeding power to the circuit.

 

[Vladimir]

Adding the foam (damping) is a good practice, it helps reducing standing waves in the enclosure. The issue can be space in your case. Glue blocks of foam if you have the space but not completely stuff the box (needs to breathe and cool the electronics). If you have room just for one, use it on the back wall. If you have room for the side walls, do those as well. Etc.

You should calculate the port with software and if possible have it at located to benefit cooling the amplifier heatsink with air circulation.

 

[iQ Speakers]

Hi designing a good X over to work with the drivers and encloseur would require lots of skill and calculations and even then the result could be hit or miss. The kit will take the guess work out of the equation, Im sure the kit will advise on the box size and if you should need accoustic foam, again I can send you some if required this is used as part of the total design to limit reverberations and echoes and to tune the whole sound as a package. As to soldering its very easy, just make sure the tip has got solder on it ie silver then place it on the leg of the component, feed in the solder until it runs nicley around the leg remove iron, keep it still and it will quickly set. It should be fairly shiny and stuck in a peak to the leg. Good luck if you need any more advise just shout.

 

[Isaac Blanc]

Thanks to both of you for the replies!

I'm planning on buying this solder (its multicore stuff from eBay just as you suggested).

Advice noted about foam. Thankfully what you said was actually in agreement with much of what I thought about the purpose and application of padding.

 

[andyjm]

Thanks to both of you for the replies!

I'm planning on buying this solder (its multicore stuff from eBay just as you suggested).

Isaac, that solder will be great. It is tin / lead, which is the easiest to use as it 'wets' the connections better than the lead free versions now available.

Lead causes heavy metal poisoning and there has been a move to use lead free solder, certainly for plumbing (which I guess makes sense). Try to avoid chewing the solder and wash your hands after handling it and you should be fine.

There are also health concerns about the smoke/fumes given off from the flux during the soldering process - commercial setups have extractor systems and fume removal equipment built into the soldering iron. If you are soldering all day, every day, then that may be a risk. For a one off, just avoiding breathing the smoke directly and you should be fine.

 

[Isaac Blanc]

Thank for the advice. I'll remember that when soldering.