boom box idea

[gio89]

I work at an elementary school and noticed that the p.e. teacher uses a small portable boom box, that sounds terrible, especially since it is outside and blasting through small cheap speakers.
So i thought i would build my own to bring and use for the children during p.e.
What i really want to build is a 2.1 channel system capable of being loud, but still clear and nice sounding with the .1 giving that extra bass.

Is this a good amp board to use TDA7294 2.1 Power Amplifier Board 80Wx2+160W Subwoofer $38.71 Free Shipping @GoodLuckBuy.com ?
I figured 80 watts per channel is much better than the 15watt boombox they are using now, and with the 160watt sub woofer it should sound great right? I don't know if the amp requires 4 ohm or 8 ohm but I'm assuming 4 ohm if you know that would be great.

My plan was to use 2 three way car speakers and 1 car sub woofer.
please give me some advice, i think it would be real neat to say that i have built my own boom box. Also, i don't have too much money to spend, but i would like it to last and perform. Any help is much appreciated.

 

[Meshuganah]

If its gonna run on batteries they better be big ones....too heavy. Is it too far away for a power cord?........you could use a normal P.A. Otherwise, sounds like it would be good in a car with the right speakers.

Interesting chip though!

 

[Meshuganah]

Damn! you can't build it for that......so that's one chip each for the 80w and two in bridge for the bass.....with controls. But two car batteries needed for operation out on the field, or a long power cord!

 

[gio89]

The school just recieved a portable pa system, complete with ipod doc and mic inputs. But it is a 50 watt mono speaker system that is rather quiet and doesn't give great sound.

If anyone knows of any board that would give me great sound quality and still be loud enough for a class of students to hear, please let me know.

I wanted a 2.1 channel system because two 3-way car speakers would give good highs and mids, where the .1 would allow the bass to really be heard.

 

[gio89]

Also, if it didn't have to be portable do you think that board is a good buy.

I'm fairly good with electronics, but no nothing about building my own electronics. That is why this board seems appealing. All i would have to do is get a power source, and hook up the speakers, correct me if i am wrong.

 

[ingenieus]

You would need a heatsink and some sort of cabinet to house the board as well. It does look like a good buy and will do the job that you have in mind. Hopefully it comes with instructions on how to build a complete working system.

Another thing - you will need microphone pre-amplifiers too. One per mike. And a mixer. If the other PA system has a headphone output, you could use it to drive this setup.

If you want this shebang to be battery powered, you will need a deep cycle mobile home type of lead acid battery. Don't count on more than three hours or so on full blast. Might be more if you don't play too loud - this is just a guesstimate.

 

[RJM1]

If you look at the data sheet for the TDA7294 page 6 figure 5 (output power vs supply voltage 4 ohms) you would need to have +-34 volts to get 80W output @ 10% distortion( 6 - 12V batteries). With +- 12V (2 - 12V batteries) you would only get 20W output @ 10% distortion or about 15W at .5% distortion.
Data sheet.
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000017.pdf

 

[Meshuganah]

The only options for your problem are
a) Big 12v battery and a car stereo with big booster amp and a mic input.

b) Look for an old 12v transformer coupled amplifier for PA work that were used in the 60's and 70's those used to kick ***! Distortion figures were not too good but with tubes or germanium outputs it didn't matter too much. With a couple of cheap column speakers, you will get quite acceptable sound for outdoor use.
Look up Boyer amplifiers, (they were really good) Geloso, even old Siemens or Philips jobs. The transformer coupling took a lot of handy short cuts for loud public use!

 

[ingenieus]

You could use a switching power supply to convert the 12V from the battery to the +40V needed by the amp. I should have added that to the list. Easier to just use a car amp.

 

[ODougbo]

Anchor Audio

Check out Anchor Audio, they have cool (battery) stuff.

And they play loud!!

Anchor Audio,Inc.- Leader in Portable Sound Systems, Public Address Systems, Speaker Monitors, Intercom Systems, Conference Systems, Assistive Listening, & Lecterns.

 

[djk]

Sure 4x100W @ 4 Ohm TK2050 Class-D Audio Amplifier Board 320-302

Or:

4*100 watt @ 4ohm, TK2050 D-class Audio Amplifier Board | eBay

This will run off anything from 10V~32V, class D for low battery drain.

A 350W switchmode supply:

MW 24V DC14.6A 350W Regulated Switching Power Supply | eBay

 

[ingenieus]

You could also use a more high tech battery, such as lithium, at an increased price of course...

 

[Saturnus]

gio89, first a couple of elementary don'ts:

- do not use car audio speakers or amps, they're completely unsuited for the job

- do not try to go (much) above 2x15W in amplifier power or it will either not be portable or last very short time

Luckily your search is over. Just head over to my Boomiator thread. It will answer questions you didn't even think to ask.

http://www.diyaudio.com/forums/class-d/104402-boominator-another-stab-ultimate-party-machine.html

The Boominator | Facebook

 

[ODougbo]

Lots of good ideas here....might be best to put together a proposal for the ES Principal or the PTA for a Anchor setup.

 

[ingenieus]

- do not use car audio speakers or amps, they're completely unsuited for the job

Out of interest, why do you say that? Too much output power that drains the battery, or are they not reliable enough for this application?

Luckily your search is over. Just head over to my Boomiator thread. It will answer questions you didn't even think to ask.

Excellent idea! Will take quite a while to read through all of that, though.

 

[Saturnus]

Out of interest, why do you say that? Too much output power that drains the battery, or are they not reliable enough for this application?

Several reasons really.

Car audio driver have very low sensitivity when you actually look behind the marketing claims. Sensitivity is for car audio always measured at 2.83V, and not the relevant voltage for the impedance as PA drivers always are. With most car audio speakers being either 4 or even 2 ohms that means the sensitivity is actually given at 2W or even 4W which means the actual sensitivity as given for dB/W/m is exaggerated by at least 3 or even 6 dB. Furthermore, it is standard in car audio to list the peak sensitivity, and not average sensitivity in the usable range as with PA drivers, so the already inflated sensitivity can easily be inflated by another 3 dB or more for really crappy driver with huge peaks in the frequency range.

Boomboxes are compact tiny boxes that typically plays outside, and you will typically want a completely different tuning than car audio speakers which are meant to play in extremely tiny listening rooms (the cabin). It's almost impossible to get reliable t/s data on most car audio speakers but neither do you really need to. When you take the completely different uses in consideration it goes without saying that a car audio speakers t/s data will be completely useless for a compact enclosure meant to play in free field, or near free field enviroments.

Because of the above concerns car audio amplifier needs to have huge power output because otherwise the typical car audio speaker wouldn't even drown out tire noise. That's not a problem since you have an unlimited power supply in the engine so extremely large and inefficient class A/B design or multi-kilowatt class D designs is the norm. In a boombox it is not so, you have to save every milliwatt you can in order to have long playing time or a managable battery size. For example, the Boominator in the suggested build uses 50mA (0.6W) in idle. Had I included a power on status LED, that would have gone up to roughly 65mA(0.8W). In general use just removing a power status LED from the Boominator I gain roughly 2-3 hours more in battery life with typical use.

 

[gio89]

Boominator question

I like the boominator idea, But i would like it to have only the one side with speakers. And the posts don't actually describe how to build it step by step, at least not in the first fifty steps. most of the links take you to a web site and not the specific page where you can order the part.

I really like the solar panels!

I would really appreciate it if someone could just say, "hey man, you need these speakers, this amp, this is how you connect it, the box size should be this, and it will probably cost $$" I guess what I'm asking for is a DIY, i hope I'm not asking too much.

Thanks for all of the information thus far, its been very helpful.

 

[qusp]

you came to the wrong place if you just want a canned one size fits all solution, mainly because it simply doesn't exist. the boominator thread is a wealth of info for you, you need to get a better idea of what it is you actually need before you can even think about building it.