Want to build a portable ipod boombox.

[GuyPanico]

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!

 

[planet10]

NS3... easy mods to improve the sonic t-amp. I know nothing about electronic parts and how they work, so this limits my modification complexity.

Also consider the Fostex FF85k.

Audio Magus sells the Trends T-Amp with various levels of mods (conceived by our own panomaniac)

dave

 

[Fast1one]

You won't be disappointed in a small room, but in a large room they may leave more to be desired...Consider running them in a bipole configuration, one in the rear and one in the front...an MLTL would probably work well

 

[pjanda1]

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

 

[Saturnus]

You won't be disappointed in a small room, but in a large room they may leave more to be desired...Consider running them in a bipole configuration, one in the rear and one in the front...an MLTL would probably work well

Where on earth did you get that idea?

 

[GuyPanico]

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...

 

[Fast1one]

GAH! Disregard my post, I forgot this was for a boombox! Thats what happens when you have multiple windows open

Cheers,
Sergio

 

[Saturnus]

GAH! Disregard my post, I forgot this was for a boombox! Thats what happens when you have multiple windows open

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.

 

[sreten]

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

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

 

[Fast1one]

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.

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.

[IMGDEAD]http://img184.imageshack.us/img184/1003/fullrangeboomboxau2.png[/IMGDEAD]

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..

 

[Saturnus]

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

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

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.

 

[Saturnus]

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..

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.

 

[Buckapound]

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

 

[sreten]

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.

 

[Saturnus]

I agree. 96 db/watt/m sensitivity from a 4½" speaker with an fs of 68 Hz? Not likely without a neodymium magnet the size of an oil barrel.

 

[Fast1one]

Nice find! I thought it was a little too optimistic, but still miles ahead of the Aura NS3s that have a very low sensitivity...

 

[GuyPanico]

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.

 

[Fast1one]

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.

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...

 

[sreten]

Hi,

The podzuma drivers need reflexing for low bass efficiency.
They need around 6 litres each.

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-010

May look somewhat familiar, note the large discrepancy between
the specified and measured parameters. The Pioneer needs around
4 litres each sealed, and has no low bass.

/sreten.

 

[jackinnj]

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.