# DIY (Backpack Speaker System) Project



## binite (Oct 8, 2016)

This is my DIY Speaker Backpack I am making, The 4s...
A low powered 400 watt bluetooth speaker system in a portable backpack.​*v1*




​*Components List*-
Speakers- BOSS AUDIO CH4220 Chaos Exxtreme 4" 200-watt 2-way Full Range Speakers
Battery- ExpertPower EXP12200 12 Volt 20 Ah Rechargeable Battery
Bluetooth- HomeSpot Waterproof Bluetooth Dongle
Switch- HOTSYSTEM 12V 30 Amp LED ON-OFF Switch
Amp- Pyle PLMRMP1A 2-Channel Waterproof Marine Amplifier
Backpack- CVLIFE Outdoor Tactical Backpack

*Updated-*
The wiring and placement has bin moved around to be more compacted and organized...

*Questions-*
1. If you are good with electricity and amps can you give me an estimated power on time with this set up, I've talked to people making DIY Cooler Speakers, and told me a good amount of time but not an estimation...

2. If u got any ideas for it, keeping in mind I'm trying to keep it simple and a low power draw...

*v2*
*



*​*
Components List*-
Speakers- Poly-Planar MA840
Battery- TalentCell Rechargeable 72W 132WH Battery
Bluetooth- Bluetooth Audio Adapter for Music Streaming Sound System
Amp- SMSL SA 36A Pro
Backpack- CVLIFE Outdoor Tactical Backpack

*Updated*-
The 4s V2 has completely bin remade for better power and heat effeminacy in a smaller area...

*If u got some cool DIY Speaker projects, Post them below and show them off... *
Im pretty good with this stuff if u need advice =^D^=


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## MEDS (Oct 11, 2016)

Aw cool, this is right up my alley. I should be able to help you just about anything you want.

I had a very bad experience with a couple of bad boss amps, so imma go ahead and say that I'm not keen on any of their products anymore. The speakers you picked out are designed to be cheap. So your speakers are rated at 100W rms (this is the continuous power rating that really matters) for the pair, so 50W per speaker. 

On the topic of audio quality, about 70% of your sound quality comes from the enclosure for the speakers. The ideal enclosure would have sufficient volume and dense, isolating walls. You really don't have that in just a backpack. Car speakers achieve this using a sealed plastic enclosure, so you might want to look into incorporating something like that in your design. You mentioned friends using coolers. Guess what, it works because the cooler is the enclosure.
Here's a little bit of the science behind the enclosure:


Spoiler



When the woofer travels forward it creates a shock wave. That's what we hear and interpret as sound. Now when the woofer travels back, it creates an equal and out of phase shock wave coming from the back of the speaker. The sound coming from the front of the speaker and the rear of the speaker sounds almost the same, but since they're out of phase with each other, they can mix and either combine or destroy one another depending on the frequency and the listening position. That's why the enclosure is needed to suppress the backfire.



Your battery is going to be heavy (yay lead!), but it'll do. At 100W you'll get about 2 hours of battery life. For safety, you need to put a fuse less than two inches from the positive terminal. The rating of the fuse should be determined by whatever wire size you use. I would be careful about running the battery completely dry. There's nothing in your design that would prevent this, and it will damage your battery.

Amplifier: Your speakers are only rated for 50W each, so you'll have to be a little cautious powering them with a amplifier rated 100W per channel. What concerns me is that they don't advertise the type of amplifier. I bet it's a class A/B amp. For this application, I highly suggest you find a class D amp. Why? It's significantly more efficient. It's not going to heat up nearly as much as an A/B would, and it'll help your battery life. 

Your questions: Everything is going to power on instantly. All of your waiting is going to be on the bluetooth module. I assume that it's going to take a while to sort out the connection to your device.


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## Somnium (Oct 11, 2016)

I'm no expert at designing speakers but I would highly encourage to use a big woofer that being 10-12 inch for the low frequencies and a separate driver for high frequencies, maybe even horn load it, thus improving system efficiency and sound quality. And of course design a proper sealed box (sealed boxes are easy!) to further improve those aspects. A few watts RMS in an efficient system will surely make a great party.

Dayton has quite a few good offers


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## binite (Oct 11, 2016)

MEDS said:


> Aw cool, this is right up my alley. I should be able to help you just about anything you want.
> 
> I had a very bad experience with a couple of bad boss amps, so imma go ahead and say that I'm not keen on any of their products anymore. The speakers you picked out are designed to be cheap. So your speakers are rated at 100W rms (this is the continuous power rating that really matters) for the pair, so 50W per speaker.
> 
> ...



Thanks for the advice, im going to make new model with this in mind... =^D^=
Should my amp max at the speakers rms? or how dose that work?


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## MEDS (Oct 12, 2016)

Match the speakers rms power rating to the amps rms power rating. RMS stands for root mean square, and it can be thought of the "average" of the signal. An audio signal is sinusoidal, so yes, it'll have voltage peaks at the top of the waveform, but for continuous power handling, the "average" power of the system is important.


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## Somnium (Oct 12, 2016)

MEDS said:


> Match the speakers rms power rating to the amps rms power rating.



Oh definitely not! Power rating shows how much can a speaker handle before exploding and when they run near their limit speakers distort and are very inefficient at converting electricity to sound we humans perceive. In other words you're just wasting battery power for very little gain.


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## binite (Oct 12, 2016)

MEDS said:


> Match the speakers rms power rating to the amps rms power rating. RMS stands for root mean square, and it can be thought of the "average" of the signal. An audio signal is sinusoidal, so yes, it'll have voltage peaks at the top of the waveform, but for continuous power handling, the "average" power of the system is important.



Just updated to 2.0 what u think?


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## nitrohusky (Oct 12, 2016)

add a 5w solar panal


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## binite (Oct 12, 2016)

nitrohusky said:


> add a 5w solar panal



Planning that in the future =^O^=


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## nitrohusky (Oct 12, 2016)

think about a smaller battery with a 1f cap it will be lighter


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## nitrohusky (Oct 12, 2016)

a 14.4v laptop battery with a 1f cap would be better than a lead acid battery


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## nitrohusky (Oct 12, 2016)

40% lighter 20% more power


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## nitrohusky (Oct 12, 2016)

for the boss system i would use 3 14.4v laptop batterys and 1  1f cap that setup should give you about 4 hrs of run time at 50%


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## binite (Oct 12, 2016)

nitrohusky said:


> for the boss system i would use 3 14.4v laptop batterys and 1  1f cap that setup should give you about 4 hrs of run time at 50%



I'm planning on just going with v2... It has all kinds of fixes like that =^D^=


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## MEDS (Oct 13, 2016)

I like the new design. I appreciate that you took my advice with the speaker enclosures. Also it looks like you downsized your system while keeping your speakers and power source well balanced. The use of the lithium ion pack also makes charging easy, since they include the charger.


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## binite (Oct 13, 2016)

MEDS said:


> I like the new design. I appreciate that you took my advice with the speaker enclosures. Also it looks like you downsized your system while keeping your speakers and power source well balanced. The use of the lithium ion pack also makes charging easy, since they include the charger.


 Thanks =^D^=
Do u have another ideas or advise? u seem alot better then me =-_-=


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## Somnium (Oct 13, 2016)

binite said:


> Thanks =^D^=
> Do u have another ideas or advise? u seem alot better then me =-_-=



Why no one is listening to my advise!


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## binite (Oct 13, 2016)

Somnium said:


> Why no one is listening to my advise!



I read ur advice... I cant add a sub to it dew to it being to heavy and theirs not enough power for that... and i toulk advice about for power rating like u said... I just hadn't replayed yet...


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## Somnium (Oct 13, 2016)

binite said:


> I read ur advice... I cant add a sub to it dew to it being to heavy and theirs not enough power for that... and i toulk advice about for power rating like u said... I just hadn't replayed yet...



Oh no they aren't heavy at all compared to most woofers, for example dayton audio 12 inch weights less than 8lb and cost $40 and 10 inch version weights less than 5lb for $30. And it's a misconception that big speakers need a lot of power, in most cases they need less for the same loudness compared to small speakers. 

Well of course it will be a heavier/bigger system and more difficult to build, but if you value sound quality and battery life it might be worth to consider.


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## binite (Oct 13, 2016)

Somnium said:


> Oh no they aren't heavy at all compared to most woofers, for example dayton audio 12 inch weights less than 8lb and cost $40 and 10 inch version weights less than 5lb for $30. And it's a misconception that big speakers need a lot of power, in most cases they need less for the same loudness compared to small speakers.
> 
> Well of course it will be a heavier/bigger system and more difficult to build, but if you value sound quality and battery life it might be worth to consider.



Yah but sorry i'm going to stick without a sub, 2 channels of 20watts is not much to work with and the (wattege-battery life) ratio i have i love (8ish hours) if im doing my math right...


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## Somnium (Oct 13, 2016)

binite said:


> Yah but sorry i'm going to stick without a sub, 2 channels of 20watts is not much to work with and the (wattege-battery life) ratio i have i love (8ish hours) if im doing my math right...



that's up to you


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## binite (Oct 13, 2016)

nitrohusky said:


> for the boss system i would use 3 14.4v laptop batterys and 1  1f cap that setup should give you about 4 hrs of run time at 50%



Ima going to stick with the battery gots =^D^=


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