Want to build a portable ipod boombox.

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GuyPanico

GuyPanico

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Joined 2005
#1
My idea (I know some have done this as well) is to make a small portable boombox that I can dock my iphone to. I want it to be able to play at a moderate volume and have full sound. I want to keep the footprint to about the size of a standard keyboard or slightly larger.

For simplicity and cost sake, I think i'm going to use a sonic t-amp. For drivers, I am thinking about using a quartet of ported Aura NS3's. Two on each side running full range. I'm not worried about C-C wavelength interactions. I will probably be using this mostly in places where there is background noise, and I will not be facing it much of the time.

Will the pair of NS3's wired to 4ohms output fairly impressive sound with the t-amp? Now I need to research some easy mods to improve the sonic t-amp. I know nothing about electronic parts and how they work, so this limits my modification complexity.

Thanks!
 
#4
How about the Tang Band W4-1052SA? You might get slightly more sensitivity, but it should be able to do much better in the bass. It'd be cheaper. The cab might be bigger than you are looking for, though. Two TB 3"ers will give you a considerable efficiency advantage. Or, you could even consider a 1.5 way and have some real midbass via the BSC. I like the Tang Band look, but that's a matter or personal preference.

pj
 
#6
In this case, what would the benifits be with a bipole design as apposed to a standard monopole? Wouldn't I lose a little bit of volume with the drivers mounted on the rear instead of the front as well?

I forgot to include this plot in my original post...
 

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#8
Fast1one said:
GAH! Disregard my post, I forgot this was for a boombox! Thats what happens when you have multiple windows open 😎
Click to expand...

Actually your suggestion about a bipolar design of a boombox is genius. I've used it for years because it some distinct advantages that is almost impossible to get otherwise, and it practically has no disadvantages.

You might think it would be difficult placing them indoors, but the point is that you should ignore that they have backfacing speakers indoors, and just place them 10-20cm from a wall preferably on a shelf or table. And outdoors just place on the ground.

I think I've outlined the advantages in my Boominator thread but to recap it linarizes the frequency response both when used outdoors and indoors because of the positioning acting as a natural acoustic x-over.
 
#10
Saturnus said:


Actually your suggestion about a bipolar design of a boombox is genius. I've used it for years because it some distinct advantages that is almost impossible to get otherwise, and it practically has no disadvantages.

You might think it would be difficult placing them indoors, but the point is that you should ignore that they have backfacing speakers indoors, and just place them 10-20cm from a wall preferably on a shelf or table. And outdoors just place on the ground.

I think I've outlined the advantages in my Boominator thread but to recap it linarizes the frequency response both when used outdoors and indoors because of the positioning acting as a natural acoustic x-over.
Click to expand...
I am flattered! I actually considered building one with four woofers, but I wasn't sure if it would work well outdoors...

I know it would work well indoors, as that was my original intention, no need for a BSC, good bass response, and relatively cheap...

To the OP, this is what I originally intended http://www.mcminone.com/product.asp?product_id=51-075&catalog_name=MCMProducts

Unfortunately it is out of stock, but as you can see its fairly efficient.

I designed a bass reflex enclosure, the two drivers would be braced with a threaded rod, port in the front...

16.8 liters for each pair, tuned to 62 hz, F3 is 72hz.

An externally hosted image should be here but it was not working when we last tested it.


That plot is for one driver. As you can see it would be good with about 8-10 watts for each pair, won't be very loud, but loud enough I think, with little power requirements (could be powered my an AMP3 for example). Its not perfectly flat, but I wanted as much extension as possible 🙂 Ignore the second half of the graph, bass box pro is not a good estimator of the higher octaves...

It would need a high pass filter to avoid over excursion down low unfortunately..
 
#11
sreten said:
http://www.partsexpress.com/projectshowcase/podzuma/index.cfm

Hi, worth a perusal and rather louder than 4 x NS3's, 🙂/Sreten.
Click to expand...

Yeah, that's a good starting point for a good boombox. Just toss away the box design and make a roughly 25% smaller bipolar box with the 4 woofers mounted magnet to magnet on either side, adjust the box tuning to Q=1. Then toss away the suggested tweeters and use these instead. Design a new 6/12 db/octave x-over instead of the suggested 12/6 db/octave filter, with a x-over at around 3.4 KHz. You don't need a leveling resistor with the new tweeters either. Spray paint as desired. Done.
 
#12
Fast1one said:
I designed a bass reflex enclosure, the two drivers would be braced with a threaded rod, port in the front...

16.8 liters for each pair, tuned to 62 hz, F3 is 72hz.

It would need a high pass filter to avoid over excursion down low unfortunately..
Click to expand...

Make the box tuning to Q=1. Trust me on this. It'll protect the speakers better against over excursion at low frequencies and work better outdoors as well as indoors. F3 will be slightly higher though.

But if you (the OP) use a T-amp then it's then it's already filtered below 90Hz. Should you opt to go the modding way just remember to pick a much smaller input cap than suggested in the mods.

Check out the link in my sig. That's my bipolar boombox.
 
#13
If you're not averse to a little soldering, I'd suggest the Amp 6 from 41hz. It has a little more power and a fair amount more bass compared to the T-Amp, even after mods. If you're a GREAT solderer, try the Amp 32 Basic for it's smaller size and lower cost.

Oh, and the other advantage of a dipole, is the reflected sound seems to spread around the room better (after it bounces off the back wall) and gives you a little more soundstage from a small box. I'm thinking of adding a pair of tweeters to the back of mine for just this purpose.

--Buckapound
 
#14
http://www.mcminone.com/product.asp?product_id=51-075&catalog_name=MCMProducts

# Features: Rigid paper cone
# Treated foam surround
# Stamped steel frame
# 1" voice coil
# 9.3 oz. magnet
# Mfr. #A11EC80-02F

Specifications:
# Power capacity: 20W/30W RMS/peak
# Sensitivity: 96dB (1W/1M)
# Impedance: 8ohm
# Re: 7.6ohm
# Le: 0.25mH
# Frequency response: 68Hz ~ 15KHz
# Fs: 68Hz
# Qts: 0.38
# Qes: 0.47
# Qms: 1.40
# VAS (liters): 8.7
# Xmax: 1.0mm


Hi,

Definitely some fantasy numbers with the above drivers specification.

The numbers for this version are more real world :

Product Details:
# Rigid paper cone
# Treated cloth surround
# Stamped steel frame
# 9.2 oz. magnet plus cancellation magnet
# 1" voice coil

# Features: Power capacity: 20W/40W RMS/peak
# Frequency response: 95Hz~15KHz
# Fs: 96Hz
# Impedance: 8ohm
# SPL: 89dB (1W/1M)
# Re: 7.04ohm
# Qes: 0.75
# Qms: 1.74
# Qts: 0.52
# Vas (liters): 4.76
# Xmax: 1.1mm

http://www.mcminone.com/product.asp?product_id=55-2615&catalog_name=MCMProducts

🙂/sreten.
 
#17
I will definantly make mine a bipole now. But i'm still concerned about the bass response and volume requirements of some of the drivers that have been suggested. I'd like to keep mine easily transportable. I've decided to keep the footprint to not much larger then a typical keyboard. So within 20"x9" and maybe about 8 or 9" tall.

The Podzuma looks like a great system. But again I wonder about the bass response.

I think I still want to wimp out and use a sonic impact and just upgrade the caps on it. I'm not at the level yet of making an amp kit.
 
#18
GuyPanico said:
I will definantly make mine a bipole now. But i'm still concerned about the bass response and volume requirements of some of the drivers that have been suggested. I'd like to keep mine easily transportable. I've decided to keep the footprint to not much larger then a typical keyboard. So within 20"x9" and maybe about 8 or 9" tall.

The Podzuma looks like a great system. But again I wonder about the bass response.

I think I still want to wimp out and use a sonic impact and just upgrade the caps on it. I'm not at the level yet of making an amp kit.
Click to expand...
That only gives you an internal area (1/2 inch wood, not including bracing) about .52 cubic feet or ~14-15 liters...not very much but you can probably make it work...four 4 inch drivers in sealed or vented designs in Bipole...

With a T amp it would have to be fairly efficient, so using speakers 90+db sensitivity is a must. Not sure how much fidelity you want to keep, but using PA speakers might be your best option...

Maybe use two T-amps, two 8 ohm drivers ran in parallel for a 4 ohm load, and two 4 ohm tweeters with the second amp. Active crossovers...

Take a look at these amps, fairly cheap, though they may need some modifications

http://cgi.ebay.com/2-15-watt-4ohm-...3696517QQihZ013QQcategoryZ39783QQcmdZViewItem

As for the speakers, the design suggested earlier looks promising:

http://www.partsexpress.com/projectshowcase/podzuma/index.cfm

Just put one driver in the front, one in the rear with a rod connecting them, possibly the tweeter mounted on top or in the front...the drivers are 8 ohms and the tweeters are 4 ohms, with double the power you should end up with a VERY loud boom box 😀 F3 of 80hz is nice as well...
 
#20
For the amplifier -- why not consider one of the development boards from Texas Instruments -- they are less expensive than either version of the sonic-T amplifiers and very well documented.

TPA3002D2EVM for 9 watts per channel and TPA3004D2EVM for 12 watts -- both use a DC voltage for volume control and provide an on-board reference. They are very well documented and easy to use -- but you will have to use an output filter.
 
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