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Old 17th November 2011, 08:48 PM   #1
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Default Need a 4" Coaxial speaker for Portable Boombox

Hi Guys,

I'm new to this forum and very intrigued about the information given out here.

I want to build a battery-powered portable boombox to take on camping trips. My buddies and I always buy a new boombox every year worth $30-35 and end up trashing it so I want to build something rugged and easy to clean with something as simple as an airduster.

I've come upon this instructable: Ammo Box Speakers

So far, I've decided to run off either D or C batteries with either a T2024 or T2020 Amp (Amazon.com: Lepai Tripath TA2020 Class-T Hi-Fi Audio Amplifier: Electronics) Any insight on the above please feel free to let me know.

I just need some EFFICIENT (will be running off 15-20 watts) 4" full range speakers to throw in. I'm looking at something that will cost around $40 for the pair since these will be thrown around. It's probably not the best budget but it makes sense for what its going to go through.
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Old 17th November 2011, 08:59 PM   #2
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Keep in mind. I'm not a huge audiophile...yet
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Old 17th November 2011, 09:00 PM   #3
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Don't go for crappy car audio speakers. Use proper speakers like the Monacor SP-60/4. You should get a mini tweeter with them too but they can work full-range.
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Old 17th November 2011, 09:40 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

You can use car speakers but always plan on adding l-pad resistors to the tweeter.

8 ohm drivers are less efficient but draw less battery current, also efficiency
determines how much bass extension you get for box size, its all a balance.

Speaker Stuff the Vifa coaxial here fits your
budget, has a decent suggested c/o, and some good design details. It
will limit the power output of amps designed for 4 ohms, but you get
that back in battery life.

The Lepai IMO is a good choice.

Its all a question of balance, how big, how long, how loud, how deep etc.

But for quality IMHO with its c/o you'd be hard pushed to beat the Vifa.
Here quality means you'll most likely compromise long battery life with loud.

rgds, sreten.
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Old 17th November 2011, 10:12 PM   #5
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Nice! The Vifa Coaxial seems like what I need.

Coming from a $35 boombox, quality-wise anything would be better. I'm going for long-battery life.

The reason why I was looking at car audio speakers is because they are more built to take a beating than let's say speakers built for a home use

The spot we go camping at is pretty dusty...
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Old 18th November 2011, 05:47 PM   #6
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I must stress those VIFAs are not center dust protected. There's no screen to avoid dust getting directly into the VC so grill and heavy duty speaker cloth must be used if you intent on using them for a portable speaker. Otherwise they're good except they have terrible sensitivity compared to the Monacor SP-60/4s which are roughly the same price btw.
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Old 19th November 2011, 01:06 AM   #7
sreten is offline sreten  United Kingdom
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Hi,

87dB @ 8ohm is the same as 90dB @ 4 ohm regarding efficiency and battery life.

How you can say the former is "terrible" compared to the latter is beyond me.

rgds, sreten.
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Old 19th November 2011, 02:48 PM   #8
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Quote:
Originally Posted by sreten View Post
87dB @ 8ohm is the same as 90dB @ 4 ohm regarding efficiency and battery life.

How you can say the former is "terrible" compared to the latter is beyond me.
That much is obvious.

Let's take a typical amp used in a boombox, a TA2020 based one. Max output @ 8 ohms = 8W and 16W @ 4 ohms.

Now the peak volume (per channel) of the 2 drivers is:

VIFA = 96 dB
MONACOR = 102 dB

So the Monacor can play twice as loud although at twice the power consumed but that's still miniscule, ie. about 2W per channel.
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Old 19th November 2011, 03:21 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Saturnus View Post

That much is obvious.
Hi,

No its not and the above is wrong. The two drivers are the same efficiency.
The Monacor will only do 99dB, not 102dB (that needs 32W into 4 ohms).

rgds, sreten.
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Old 19th November 2011, 03:55 PM   #10
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Quote:
Originally Posted by sreten View Post
Hi,

No its not and the above is wrong. The two drivers are the same efficiency.
The Monacor will only do 99dB, not 102dB (that needs 32W into 4 ohms).

rgds, sreten.
lol. You can't be serious.

Ok. Let me spell it out so even you can understand it.

For the Monacor SP-60/4

90 dB @ 1W
93 dB @ 2W
96 dB @ 4W
99 dB @ 8W
102 dB @ 16W

For the VIFA coax

87 @ 1W
90 @ 2W
93 @ 4W
96 @ 8W
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